]> pd.if.org Git - btree/commitdiff
Use test & set latching instead of file locking calls
authorunknown <karl@E04.petzent.com>
Tue, 25 Feb 2014 20:09:08 +0000 (12:09 -0800)
committerunknown <karl@E04.petzent.com>
Tue, 25 Feb 2014 20:09:08 +0000 (12:09 -0800)
btree2t.c [new file with mode: 0644]

diff --git a/btree2t.c b/btree2t.c
new file mode 100644 (file)
index 0000000..7138712
--- /dev/null
+++ b/btree2t.c
@@ -0,0 +1,2388 @@
+// btree version 2t
+//     with reworked bt_deletekey code
+// 25 FEB 2014
+
+// author: karl malbrain, malbrain@cal.berkeley.edu
+
+/*
+This work, including the source code, documentation
+and related data, is placed into the public domain.
+
+The orginal author is Karl Malbrain.
+
+THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY
+OF ANY KIND, NOT EVEN THE IMPLIED WARRANTY OF
+MERCHANTABILITY. THE AUTHOR OF THIS SOFTWARE,
+ASSUMES _NO_ RESPONSIBILITY FOR ANY CONSEQUENCE
+RESULTING FROM THE USE, MODIFICATION, OR
+REDISTRIBUTION OF THIS SOFTWARE.
+*/
+
+// Please see the project home page for documentation
+// code.google.com/p/high-concurrency-btree
+
+#define _FILE_OFFSET_BITS 64
+#define _LARGEFILE64_SOURCE
+
+#ifdef linux
+#define _GNU_SOURCE
+#endif
+
+#ifdef unix
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <errno.h>
+#else
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <fcntl.h>
+#endif
+
+#include <memory.h>
+#include <string.h>
+
+typedef unsigned long long     uid;
+
+#ifndef unix
+typedef unsigned long long     off64_t;
+typedef unsigned short         ushort;
+typedef unsigned int           uint;
+#endif
+
+#define BT_latchtable  128                                     // number of latch manager slots
+
+#define BT_ro 0x6f72   // ro
+#define BT_rw 0x7772   // rw
+#define BT_fl 0x6c66   // fl
+
+#define BT_maxbits             24                                      // maximum page size in bits
+#define BT_minbits             9                                       // minimum page size in bits
+#define BT_minpage             (1 << BT_minbits)       // minimum page size
+#define BT_maxpage             (1 << BT_maxbits)       // maximum page size
+
+/*
+There are five lock types for each node in three independent sets: 
+1. (set 1) AccessIntent: Sharable. Going to Read the node. Incompatible with NodeDelete. 
+2. (set 1) NodeDelete: Exclusive. About to release the node. Incompatible with AccessIntent. 
+3. (set 2) ReadLock: Sharable. Read the node. Incompatible with WriteLock. 
+4. (set 2) WriteLock: Exclusive. Modify the node. Incompatible with ReadLock and other WriteLocks. 
+5. (set 3) ParentModification: Exclusive. Change the node's parent keys. Incompatible with another ParentModification. 
+*/
+
+typedef enum{
+       BtLockAccess,
+       BtLockDelete,
+       BtLockRead,
+       BtLockWrite,
+       BtLockParent
+}BtLock;
+
+//     definition for latch implementation
+
+// exclusive is set for write access
+// share is count of read accessors
+// grant write lock when share == 0
+
+volatile typedef struct {
+       unsigned char mutex[1];
+       unsigned char exclusive:1;
+       unsigned char pending:1;
+       ushort share;
+} BtSpinLatch;
+
+//  hash table entries
+
+typedef struct {
+       BtSpinLatch latch[1];
+       volatile ushort slot;           // Latch table entry at head of chain
+} BtHashEntry;
+
+//     latch manager table structure
+
+typedef struct {
+       BtSpinLatch readwr[1];          // read/write page lock
+       BtSpinLatch access[1];          // Access Intent/Page delete
+       BtSpinLatch parent[1];          // Posting of fence key in parent
+       BtSpinLatch busy[1];            // slot is being moved between chains
+       volatile ushort next;           // next entry in hash table chain
+       volatile ushort prev;           // prev entry in hash table chain
+       volatile ushort pin;            // number of outstanding locks
+       volatile ushort hash;           // hash slot entry is under
+       volatile uid page_no;           // latch set page number
+} BtLatchSet;
+
+//     Define the length of the page and key pointers
+
+#define BtId 6
+
+//     Page key slot definition.
+
+//     If BT_maxbits is 15 or less, you can save 2 bytes
+//     for each key stored by making the first two uints
+//     into ushorts.  You can also save 4 bytes by removing
+//     the tod field from the key.
+
+//     Keys are marked dead, but remain on the page until
+//     cleanup is called. The fence key (highest key) for
+//     the page is always present, even if dead.
+
+typedef struct {
+       uint off:BT_maxbits;            // page offset for key start
+       uint dead:1;                            // set for deleted key
+       uint tod;                                       // time-stamp for key
+       unsigned char id[BtId];         // id associated with key
+} BtSlot;
+
+//     The key structure occupies space at the upper end of
+//     each page.  It's a length byte followed by the value
+//     bytes.
+
+typedef struct {
+       unsigned char len;
+       unsigned char key[0];
+} *BtKey;
+
+//     The first part of an index page.
+//     It is immediately followed
+//     by the BtSlot array of keys.
+
+typedef struct BtPage_ {
+       uint cnt;                                       // count of keys in page
+       uint act;                                       // count of active keys
+       uint min;                                       // next key offset
+       unsigned char bits:7;           // page size in bits
+       unsigned char free:1;           // page is on free list
+       unsigned char lvl:6;            // level of page
+       unsigned char kill:1;           // page is being deleted
+       unsigned char dirty:1;          // page is dirty
+       unsigned char right[BtId];      // page number to right
+} *BtPage;
+
+//     The memory mapping hash table entry
+
+typedef struct {
+       BtPage page;            // mapped page pointer
+       uid  page_no;           // mapped page number
+       void *lruprev;          // least recently used previous cache block
+       void *lrunext;          // lru next cache block
+       void *hashprev;         // previous cache block for the same hash idx
+       void *hashnext;         // next cache block for the same hash idx
+#ifndef unix
+       HANDLE hmap;
+#endif
+}BtHash;
+
+typedef struct {
+       struct BtPage_ alloc[2];        // next & free page_nos in right ptr
+       BtSpinLatch lock[1];            // allocation area lite latch
+       ushort latchdeployed;           // highest number of latch entries deployed
+       ushort nlatchpage;                      // number of latch pages at BT_latch
+       ushort latchtotal;                      // number of page latch entries
+       ushort latchhash;                       // number of latch hash table slots
+       ushort latchvictim;                     // next latch entry to examine
+       BtHashEntry table[0];           // the hash table
+} BtLatchMgr;
+
+//     The object structure for Btree access
+
+typedef struct _BtDb {
+       uint page_size;         // each page size       
+       uint page_bits;         // each page size in bits       
+       uint seg_bits;          // segment size in pages in bits
+       uid page_no;            // current page number  
+       uid cursor_page;        // current cursor page number   
+       int  err;
+       uint mode;                      // read-write mode
+       uint mapped_io;         // use memory mapping
+       BtPage temp;            // temporary frame buffer (memory mapped/file IO)
+       BtPage alloc;           // frame buffer for alloc page ( page 0 )
+       BtPage cursor;          // cached frame for start/next (never mapped)
+       BtPage frame;           // spare frame for the page split (never mapped)
+       BtPage zero;            // zeroes frame buffer (never mapped)
+       BtPage page;            // current page
+       BtLatchSet *latch;              // current page latch
+       BtLatchMgr *latchmgr;   // mapped latch page from allocation page
+       BtLatchSet *latchsets;  // mapped latch set from latch pages
+#ifdef unix
+       int idx;
+#else
+       HANDLE idx;
+       HANDLE halloc;          // allocation and latch table handle
+#endif
+       unsigned char *mem;     // frame, cursor, page memory buffer
+       int nodecnt;            // highest page cache segment in use
+       int nodemax;            // highest page cache segment allocated
+       int hashmask;           // number of pages in segments - 1
+       int hashsize;           // size of hash table
+       int found;                      // last deletekey found key
+       BtHash *lrufirst;       // lru list head
+       BtHash *lrulast;        // lru list tail
+       ushort *cache;          // hash table for cached segments
+       BtHash *nodes;          // segment cache
+} BtDb;
+
+typedef enum {
+BTERR_ok = 0,
+BTERR_notfound,
+BTERR_struct,
+BTERR_ovflw,
+BTERR_lock,
+BTERR_hash,
+BTERR_kill,
+BTERR_map,
+BTERR_wrt,
+BTERR_eof
+} BTERR;
+
+// B-Tree functions
+extern void bt_close (BtDb *bt);
+extern BtDb *bt_open (char *name, uint mode, uint bits, uint cacheblk, uint pgblk, uint hashsize);
+extern BTERR  bt_insertkey (BtDb *bt, unsigned char *key, uint len, uint lvl, uid id, uint tod);
+extern BTERR  bt_deletekey (BtDb *bt, unsigned char *key, uint len, uint lvl);
+extern uid bt_findkey    (BtDb *bt, unsigned char *key, uint len);
+extern uint bt_startkey  (BtDb *bt, unsigned char *key, uint len);
+extern uint bt_nextkey   (BtDb *bt, uint slot);
+
+//     internal functions
+BTERR bt_update (BtDb *bt, BtPage page, uid page_no);
+BTERR bt_mappage (BtDb *bt, BtPage *page, uid page_no);
+//  Helper functions to return slot values
+
+extern BtKey bt_key (BtDb *bt, uint slot);
+extern uid bt_uid (BtDb *bt, uint slot);
+extern uint bt_tod (BtDb *bt, uint slot);
+
+//  BTree page number constants
+#define ALLOC_page             0
+#define ROOT_page              1
+#define LEAF_page              2
+#define LATCH_page             3
+
+//     Number of levels to create in a new BTree
+
+#define MIN_lvl                        2
+
+//  The page is allocated from low and hi ends.
+//  The key offsets and row-id's are allocated
+//  from the bottom, while the text of the key
+//  is allocated from the top.  When the two
+//  areas meet, the page is split into two.
+
+//  A key consists of a length byte, two bytes of
+//  index number (0 - 65534), and up to 253 bytes
+//  of key value.  Duplicate keys are discarded.
+//  Associated with each key is a 48 bit row-id.
+
+//  The b-tree root is always located at page 1.
+//     The first leaf page of level zero is always
+//     located on page 2.
+
+//     The b-tree pages are linked with right
+//     pointers to facilitate enumerators,
+//     and provide for concurrency.
+
+//     When to root page fills, it is split in two and
+//     the tree height is raised by a new root at page
+//     one with two keys.
+
+//     Deleted keys are marked with a dead bit until
+//     page cleanup The fence key for a node is always
+//     present, even after deletion and cleanup.
+
+//  Deleted leaf pages are reclaimed  on a free list.
+//     The upper levels of the btree are fixed on creation.
+
+//  Groups of pages from the btree are optionally
+//  cached with memory mapping. A hash table is used to keep
+//  track of the cached pages.  This behaviour is controlled
+//  by the number of cache blocks parameter and pages per block
+//     given to bt_open.
+
+//  To achieve maximum concurrency one page is locked at a time
+//  as the tree is traversed to find leaf key in question. The right
+//  page numbers are used in cases where the page is being split,
+//     or consolidated.
+
+//  Page 0 (ALLOC page) is dedicated to lock for new page extensions,
+//     and chains empty leaf pages together for reuse.
+
+//     Parent locks are obtained to prevent resplitting or deleting a node
+//     before its fence is posted into its upper level.
+
+//     A special open mode of BT_fl is provided to safely access files on
+//     WIN32 networks. WIN32 network operations should not use memory mapping.
+//     This WIN32 mode sets FILE_FLAG_NOBUFFERING and FILE_FLAG_WRITETHROUGH
+//     to prevent local caching of network file contents.
+
+//     Access macros to address slot and key values from the page.
+//     Page slots use 1 based indexing.
+
+#define slotptr(page, slot) (((BtSlot *)(page+1)) + (slot-1))
+#define keyptr(page, slot) ((BtKey)((unsigned char*)(page) + slotptr(page, slot)->off))
+
+void bt_putid(unsigned char *dest, uid id)
+{
+int i = BtId;
+
+       while( i-- )
+               dest[i] = (unsigned char)id, id >>= 8;
+}
+
+uid bt_getid(unsigned char *src)
+{
+uid id = 0;
+int i;
+
+       for( i = 0; i < BtId; i++ )
+               id <<= 8, id |= *src++; 
+
+       return id;
+}
+
+BTERR bt_abort (BtDb *bt, BtPage page, uid page_no, BTERR err)
+{
+BtKey ptr;
+
+       fprintf(stderr, "\n Btree2 abort, error %d on page %.8x\n", err, page_no);
+       fprintf(stderr, "level=%d kill=%d free=%d cnt=%x act=%x\n", page->lvl, page->kill, page->free, page->cnt, page->act);
+       ptr = keyptr(page, page->cnt);
+       fprintf(stderr, "fence='%.*s'\n", ptr->len, ptr->key);
+       fprintf(stderr, "right=%.8x\n", bt_getid(page->right));
+}
+
+//     Latch Manager
+
+//     wait until write lock mode is clear
+//     and add 1 to the share count
+
+void bt_spinreadlock(BtSpinLatch *latch)
+{
+ushort prev;
+
+  do {
+       //      obtain latch mutex
+#ifdef unix
+       if( __sync_lock_test_and_set(latch->mutex, 1) )
+               continue;
+#else
+       if( _InterlockedExchange8(latch->mutex, 1) )
+               continue;
+#endif
+       //  see if exclusive request is granted or pending
+
+       if( prev = !(latch->exclusive | latch->pending) )
+               latch->share++;
+
+#ifdef unix
+       *latch->mutex = 0;
+#else
+       _InterlockedExchange8(latch->mutex, 0);
+#endif
+
+       if( prev )
+               return;
+
+#ifdef  unix
+  } while( sched_yield(), 1 );
+#else
+  } while( SwitchToThread(), 1 );
+#endif
+}
+
+//     wait for other read and write latches to relinquish
+
+void bt_spinwritelock(BtSpinLatch *latch)
+{
+uint prev;
+
+  do {
+#ifdef  unix
+       if( __sync_lock_test_and_set(latch->mutex, 1) )
+               continue;
+#else
+       if( _InterlockedExchange8(latch->mutex, 1) )
+               continue;
+#endif
+       if( prev = !(latch->share | latch->exclusive) )
+               latch->exclusive = 1, latch->pending = 0;
+       else
+               latch->pending = 1;
+#ifdef unix
+       *latch->mutex = 0;
+#else
+       _InterlockedExchange8(latch->mutex, 0);
+#endif
+       if( prev )
+               return;
+#ifdef  unix
+  } while( sched_yield(), 1 );
+#else
+  } while( SwitchToThread(), 1 );
+#endif
+}
+
+//     try to obtain write lock
+
+//     return 1 if obtained,
+//             0 otherwise
+
+int bt_spinwritetry(BtSpinLatch *latch)
+{
+uint prev;
+
+#ifdef unix
+       if( __sync_lock_test_and_set(latch->mutex, 1) )
+               return 0;
+#else
+       if( _InterlockedExchange8(latch->mutex, 1) )
+               return 0;
+#endif
+       //      take write access if all bits are clear
+
+       if( prev = !(latch->exclusive | latch->share) )
+               latch->exclusive = 1;
+
+#ifdef unix
+       *latch->mutex = 0;
+#else
+       _InterlockedExchange8(latch->mutex, 0);
+#endif
+       return prev;
+}
+
+//     clear write mode
+
+void bt_spinreleasewrite(BtSpinLatch *latch)
+{
+#ifdef unix
+       while( __sync_lock_test_and_set(latch->mutex, 1) )
+               sched_yield();
+#else
+       while( _InterlockedExchange8(latch->mutex, 1) )
+               SwitchToThread();
+#endif
+       latch->exclusive = 0;
+#ifdef unix
+       *latch->mutex = 0;
+#else
+       _InterlockedExchange8(latch->mutex, 0);
+#endif
+}
+
+//     decrement reader count
+
+void bt_spinreleaseread(BtSpinLatch *latch)
+{
+#ifdef unix
+       while( __sync_lock_test_and_set(latch->mutex, 1) )
+               sched_yield();
+#else
+       while( _InterlockedExchange8(latch->mutex, 1) )
+               SwitchToThread();
+#endif
+       latch->share--;
+#ifdef unix
+       *latch->mutex = 0;
+#else
+       _InterlockedExchange8(latch->mutex, 0);
+#endif
+}
+
+//     link latch table entry into latch hash table
+
+void bt_latchlink (BtDb *bt, ushort hashidx, ushort victim, uid page_no)
+{
+BtLatchSet *latch = bt->latchsets + victim;
+
+       if( latch->next = bt->latchmgr->table[hashidx].slot )
+               bt->latchsets[latch->next].prev = victim;
+
+       bt->latchmgr->table[hashidx].slot = victim;
+       latch->page_no = page_no;
+       latch->hash = hashidx;
+       latch->prev = 0;
+}
+
+//     release latch pin
+
+void bt_unpinlatch (BtLatchSet *latch)
+{
+#ifdef unix
+       __sync_fetch_and_add(&latch->pin, -1);
+#else
+       _InterlockedDecrement16 (&latch->pin);
+#endif
+}
+
+//     find existing latchset or inspire new one
+//     return with latchset pinned
+
+BtLatchSet *bt_pinlatch (BtDb *bt, uid page_no)
+{
+ushort hashidx = page_no % bt->latchmgr->latchhash;
+ushort slot, avail = 0, victim, idx;
+BtLatchSet *latch;
+
+       //  obtain read lock on hash table entry
+
+       bt_spinreadlock(bt->latchmgr->table[hashidx].latch);
+
+       if( slot = bt->latchmgr->table[hashidx].slot ) do
+       {
+               latch = bt->latchsets + slot;
+               if( page_no == latch->page_no )
+                       break;
+       } while( slot = latch->next );
+
+       if( slot ) {
+#ifdef unix
+               __sync_fetch_and_add(&latch->pin, 1);
+#else
+               _InterlockedIncrement16 (&latch->pin);
+#endif
+       }
+
+    bt_spinreleaseread (bt->latchmgr->table[hashidx].latch);
+
+       if( slot )
+               return latch;
+
+  //  try again, this time with write lock
+
+  bt_spinwritelock(bt->latchmgr->table[hashidx].latch);
+
+  if( slot = bt->latchmgr->table[hashidx].slot ) do
+  {
+       latch = bt->latchsets + slot;
+       if( page_no == latch->page_no )
+               break;
+       if( !latch->pin && !avail )
+               avail = slot;
+  } while( slot = latch->next );
+
+  //  found our entry, or take over an unpinned one
+
+  if( slot || (slot = avail) ) {
+       latch = bt->latchsets + slot;
+#ifdef unix
+       __sync_fetch_and_add(&latch->pin, 1);
+#else
+       _InterlockedIncrement16 (&latch->pin);
+#endif
+       latch->page_no = page_no;
+       bt_spinreleasewrite(bt->latchmgr->table[hashidx].latch);
+       return latch;
+  }
+
+       //  see if there are any unused entries
+#ifdef unix
+       victim = __sync_fetch_and_add (&bt->latchmgr->latchdeployed, 1) + 1;
+#else
+       victim = _InterlockedIncrement16 (&bt->latchmgr->latchdeployed);
+#endif
+
+       if( victim < bt->latchmgr->latchtotal ) {
+               latch = bt->latchsets + victim;
+#ifdef unix
+               __sync_fetch_and_add(&latch->pin, 1);
+#else
+               _InterlockedIncrement16 (&latch->pin);
+#endif
+               bt_latchlink (bt, hashidx, victim, page_no);
+               bt_spinreleasewrite (bt->latchmgr->table[hashidx].latch);
+               return latch;
+       }
+
+#ifdef unix
+       victim = __sync_fetch_and_add (&bt->latchmgr->latchdeployed, -1);
+#else
+       victim = _InterlockedDecrement16 (&bt->latchmgr->latchdeployed);
+#endif
+  //  find and reuse previous lock entry
+
+  while( 1 ) {
+#ifdef unix
+       victim = __sync_fetch_and_add(&bt->latchmgr->latchvictim, 1);
+#else
+       victim = _InterlockedIncrement16 (&bt->latchmgr->latchvictim) - 1;
+#endif
+       //      we don't use slot zero
+
+       if( victim %= bt->latchmgr->latchtotal )
+               latch = bt->latchsets + victim;
+       else
+               continue;
+
+       //      take control of our slot
+       //      from other threads
+
+       if( latch->pin || !bt_spinwritetry (latch->busy) )
+               continue;
+
+       idx = latch->hash;
+
+       // try to get write lock on hash chain
+       //      skip entry if not obtained
+       //      or has outstanding locks
+
+       if( !bt_spinwritetry (bt->latchmgr->table[idx].latch) ) {
+               bt_spinreleasewrite (latch->busy);
+               continue;
+       }
+
+       if( latch->pin ) {
+               bt_spinreleasewrite (latch->busy);
+               bt_spinreleasewrite (bt->latchmgr->table[idx].latch);
+               continue;
+       }
+
+       //  unlink our available victim from its hash chain
+
+       if( latch->prev )
+               bt->latchsets[latch->prev].next = latch->next;
+       else
+               bt->latchmgr->table[idx].slot = latch->next;
+
+       if( latch->next )
+               bt->latchsets[latch->next].prev = latch->prev;
+
+       bt_spinreleasewrite (bt->latchmgr->table[idx].latch);
+#ifdef unix
+       __sync_fetch_and_add(&latch->pin, 1);
+#else
+       _InterlockedIncrement16 (&latch->pin);
+#endif
+       bt_latchlink (bt, hashidx, victim, page_no);
+       bt_spinreleasewrite (bt->latchmgr->table[hashidx].latch);
+       bt_spinreleasewrite (latch->busy);
+       return latch;
+  }
+}
+
+//     close and release memory
+
+void bt_close (BtDb *bt)
+{
+BtHash *hash;
+#ifdef unix
+       // release mapped pages
+
+       if( hash = bt->lrufirst )
+               do munmap (hash->page, (bt->hashmask+1) << bt->page_bits);
+               while(hash = hash->lrunext);
+
+       if( bt->mem )
+               free (bt->mem);
+       close (bt->idx);
+       free (bt->cache);
+       free (bt);
+#else
+       if( hash = bt->lrufirst )
+         do
+         {
+               FlushViewOfFile(hash->page, 0);
+               UnmapViewOfFile(hash->page);
+               CloseHandle(hash->hmap);
+         } while(hash = hash->lrunext);
+
+       if( bt->mem)
+               VirtualFree (bt->mem, 0, MEM_RELEASE);
+       FlushFileBuffers(bt->idx);
+       CloseHandle(bt->idx);
+       GlobalFree (bt->cache);
+       GlobalFree (bt);
+#endif
+}
+//  open/create new btree
+
+//     call with file_name, BT_openmode, bits in page size (e.g. 16),
+//             size of mapped page pool (e.g. 8192)
+
+BtDb *bt_open (char *name, uint mode, uint bits, uint nodemax, uint segsize, uint hashsize)
+{
+uint lvl, attr, cacheblk, last, slot, idx;
+uint nlatchpage, latchhash;
+BtLatchMgr *latchmgr;
+off64_t size;
+uint amt[1];
+BtKey key;
+BtDb* bt;
+int flag;
+
+#ifndef unix
+SYSTEM_INFO sysinfo[1];
+#endif
+
+       // determine sanity of page size and buffer pool
+
+       if( bits > BT_maxbits )
+               bits = BT_maxbits;
+       else if( bits < BT_minbits )
+               bits = BT_minbits;
+
+#ifdef unix
+       bt = calloc (1, sizeof(BtDb));
+
+       bt->idx = open ((char*)name, O_RDWR | O_CREAT, 0666);
+
+       if( bt->idx == -1 )
+               return free(bt), NULL;
+       
+       cacheblk = 4096;        // minimum mmap segment size for unix
+
+#else
+       bt = GlobalAlloc (GMEM_FIXED|GMEM_ZEROINIT, sizeof(BtDb));
+       attr = FILE_ATTRIBUTE_NORMAL;
+       bt->idx = CreateFile(name, GENERIC_READ| GENERIC_WRITE, FILE_SHARE_READ|FILE_SHARE_WRITE, NULL, OPEN_ALWAYS, attr, NULL);
+
+       if( bt->idx == INVALID_HANDLE_VALUE )
+               return GlobalFree(bt), NULL;
+
+       // normalize cacheblk to multiple of sysinfo->dwAllocationGranularity
+       GetSystemInfo(sysinfo);
+       cacheblk = sysinfo->dwAllocationGranularity;
+#endif
+
+#ifdef unix
+       latchmgr = malloc (BT_maxpage);
+       *amt = 0;
+
+       // read minimum page size to get root info
+
+       if( size = lseek (bt->idx, 0L, 2) ) {
+               if( pread(bt->idx, latchmgr, BT_minpage, 0) == BT_minpage )
+                       bits = latchmgr->alloc->bits;
+               else
+                       return free(bt), free(latchmgr), NULL;
+       } else if( mode == BT_ro )
+               return free(latchmgr), bt_close (bt), NULL;
+#else
+       latchmgr = VirtualAlloc(NULL, BT_maxpage, MEM_COMMIT, PAGE_READWRITE);
+       size = GetFileSize(bt->idx, amt);
+
+       if( size || *amt ) {
+               if( !ReadFile(bt->idx, (char *)latchmgr, BT_minpage, amt, NULL) )
+                       return bt_close (bt), NULL;
+               bits = latchmgr->alloc->bits;
+       } else if( mode == BT_ro )
+               return bt_close (bt), NULL;
+#endif
+
+       bt->page_size = 1 << bits;
+       bt->page_bits = bits;
+
+       bt->mode = mode;
+
+       if( cacheblk < bt->page_size )
+               cacheblk = bt->page_size;
+
+       //  mask for partial memmaps
+
+       bt->hashmask = (cacheblk >> bits) - 1;
+
+       //      see if requested size of pages per memmap is greater
+
+       if( (1 << segsize) > bt->hashmask )
+               bt->hashmask = (1 << segsize) - 1;
+
+       bt->seg_bits = 0;
+
+       while( (1 << bt->seg_bits) <= bt->hashmask )
+               bt->seg_bits++;
+
+       bt->hashsize = hashsize;
+
+       if( bt->nodemax = nodemax ) {
+#ifdef unix
+         bt->nodes = calloc (nodemax, sizeof(BtHash));
+         bt->cache = calloc (hashsize, sizeof(ushort));
+#else
+         bt->nodes = GlobalAlloc (GMEM_FIXED|GMEM_ZEROINIT, nodemax * sizeof(BtHash));
+         bt->cache = GlobalAlloc (GMEM_FIXED|GMEM_ZEROINIT, hashsize * sizeof(ushort));
+#endif
+         bt->mapped_io = 1;
+       }
+
+       if( size || *amt )
+               goto btlatch;
+
+       // initialize an empty b-tree with latch page, root page, page of leaves
+       // and page(s) of latches
+
+       memset (latchmgr, 0, 1 << bits);
+       nlatchpage = BT_latchtable / (bt->page_size / sizeof(BtLatchSet)) + 1; 
+       bt_putid(latchmgr->alloc->right, MIN_lvl+1+nlatchpage);
+       latchmgr->alloc->bits = bt->page_bits;
+
+       latchmgr->nlatchpage = nlatchpage;
+       latchmgr->latchtotal = nlatchpage * (bt->page_size / sizeof(BtLatchSet));
+
+       //  initialize latch manager
+
+       latchhash = (bt->page_size - sizeof(BtLatchMgr)) / sizeof(BtHashEntry);
+
+       //      size of hash table = total number of latchsets
+
+       if( latchhash > latchmgr->latchtotal )
+               latchhash = latchmgr->latchtotal;
+
+       latchmgr->latchhash = latchhash;
+
+#ifdef unix
+       if( write (bt->idx, latchmgr, bt->page_size) < bt->page_size )
+               return bt_close (bt), NULL;
+#else
+       if( !WriteFile (bt->idx, (char *)latchmgr, bt->page_size, amt, NULL) )
+               return bt_close (bt), NULL;
+
+       if( *amt < bt->page_size )
+               return bt_close (bt), NULL;
+#endif
+
+       memset (latchmgr, 0, 1 << bits);
+       latchmgr->alloc->bits = bt->page_bits;
+
+       for( lvl=MIN_lvl; lvl--; ) {
+               slotptr(latchmgr->alloc, 1)->off = bt->page_size - 3;
+               bt_putid(slotptr(latchmgr->alloc, 1)->id, lvl ? MIN_lvl - lvl + 1 : 0);         // next(lower) page number
+               key = keyptr(latchmgr->alloc, 1);
+               key->len = 2;           // create stopper key
+               key->key[0] = 0xff;
+               key->key[1] = 0xff;
+               latchmgr->alloc->min = bt->page_size - 3;
+               latchmgr->alloc->lvl = lvl;
+               latchmgr->alloc->cnt = 1;
+               latchmgr->alloc->act = 1;
+#ifdef unix
+               if( write (bt->idx, latchmgr, bt->page_size) < bt->page_size )
+                       return bt_close (bt), NULL;
+#else
+               if( !WriteFile (bt->idx, (char *)latchmgr, bt->page_size, amt, NULL) )
+                       return bt_close (bt), NULL;
+
+               if( *amt < bt->page_size )
+                       return bt_close (bt), NULL;
+#endif
+       }
+
+       // clear out latch manager locks
+       //      and rest of pages to round out segment
+
+       memset(latchmgr, 0, bt->page_size);
+       last = MIN_lvl + 1;
+
+       while( last <= ((MIN_lvl + 1 + nlatchpage) | bt->hashmask) ) {
+#ifdef unix
+               pwrite(bt->idx, latchmgr, bt->page_size, last << bt->page_bits);
+#else
+               SetFilePointer (bt->idx, last << bt->page_bits, NULL, FILE_BEGIN);
+               if( !WriteFile (bt->idx, (char *)latchmgr, bt->page_size, amt, NULL) )
+                       return bt_close (bt), NULL;
+               if( *amt < bt->page_size )
+                       return bt_close (bt), NULL;
+#endif
+               last++;
+       }
+
+btlatch:
+#ifdef unix
+       flag = PROT_READ | PROT_WRITE;
+       bt->latchmgr = mmap (0, bt->page_size, flag, MAP_SHARED, bt->idx, ALLOC_page * bt->page_size);
+       if( bt->latchmgr == MAP_FAILED )
+               return bt_close (bt), NULL;
+       bt->latchsets = (BtLatchSet *)mmap (0, bt->latchmgr->nlatchpage * bt->page_size, flag, MAP_SHARED, bt->idx, LATCH_page * bt->page_size);
+       if( bt->latchsets == MAP_FAILED )
+               return bt_close (bt), NULL;
+#else
+       flag = PAGE_READWRITE;
+       bt->halloc = CreateFileMapping(bt->idx, NULL, flag, 0, (BT_latchtable / (bt->page_size / sizeof(BtLatchSet)) + 1 + LATCH_page) * bt->page_size, NULL);
+       if( !bt->halloc )
+               return bt_close (bt), NULL;
+
+       flag = FILE_MAP_WRITE;
+       bt->latchmgr = MapViewOfFile(bt->halloc, flag, 0, 0, (BT_latchtable / (bt->page_size / sizeof(BtLatchSet)) + 1 + LATCH_page) * bt->page_size);
+       if( !bt->latchmgr )
+               return GetLastError(), bt_close (bt), NULL;
+
+       bt->latchsets = (void *)((char *)bt->latchmgr + LATCH_page * bt->page_size);
+#endif
+
+#ifdef unix
+       free (latchmgr);
+#else
+       VirtualFree (latchmgr, 0, MEM_RELEASE);
+#endif
+
+#ifdef unix
+       bt->mem = malloc (6 * bt->page_size);
+#else
+       bt->mem = VirtualAlloc(NULL, 6 * bt->page_size, MEM_COMMIT, PAGE_READWRITE);
+#endif
+       bt->frame = (BtPage)bt->mem;
+       bt->cursor = (BtPage)(bt->mem + bt->page_size);
+       bt->page = (BtPage)(bt->mem + 2 * bt->page_size);
+       bt->alloc = (BtPage)(bt->mem + 3 * bt->page_size);
+       bt->temp = (BtPage)(bt->mem + 4 * bt->page_size);
+       bt->zero = (BtPage)(bt->mem + 5 * bt->page_size);
+
+       memset (bt->zero, 0, bt->page_size);
+       return bt;
+}
+
+// place write, read, or parent lock on requested page_no.
+
+void bt_lockpage(BtLock mode, BtLatchSet *latch)
+{
+       switch( mode ) {
+       case BtLockRead:
+               bt_spinreadlock (latch->readwr);
+               break;
+       case BtLockWrite:
+               bt_spinwritelock (latch->readwr);
+               break;
+       case BtLockAccess:
+               bt_spinreadlock (latch->access);
+               break;
+       case BtLockDelete:
+               bt_spinwritelock (latch->access);
+               break;
+       case BtLockParent:
+               bt_spinwritelock (latch->parent);
+               break;
+       }
+}
+
+// remove write, read, or parent lock on requested page
+
+void bt_unlockpage(BtLock mode, BtLatchSet *latch)
+{
+       switch( mode ) {
+       case BtLockRead:
+               bt_spinreleaseread (latch->readwr);
+               break;
+       case BtLockWrite:
+               bt_spinreleasewrite (latch->readwr);
+               break;
+       case BtLockAccess:
+               bt_spinreleaseread (latch->access);
+               break;
+       case BtLockDelete:
+               bt_spinreleasewrite (latch->access);
+               break;
+       case BtLockParent:
+               bt_spinreleasewrite (latch->parent);
+               break;
+       }
+}
+
+//     allocate a new page and write page into it
+
+uid bt_newpage(BtDb *bt, BtPage page)
+{
+uid new_page;
+int reuse;
+
+       //      lock allocation page
+
+       bt_spinwritelock(bt->latchmgr->lock);
+
+       // use empty chain first
+       // else allocate empty page
+
+       if( new_page = bt_getid(bt->latchmgr->alloc[1].right) ) {
+               if( bt_mappage (bt, &bt->temp, new_page) )
+                       return 0;
+               bt_putid(bt->latchmgr->alloc[1].right, bt_getid(bt->temp->right));
+               reuse = 1;
+       } else {
+               new_page = bt_getid(bt->latchmgr->alloc->right);
+               bt_putid(bt->latchmgr->alloc->right, new_page+1);
+               reuse = 0;
+       }
+
+       bt_spinreleasewrite(bt->latchmgr->lock);
+
+       if( !bt->mapped_io )
+         if( bt_update(bt, page, new_page) )
+               return 0;       //don't unlock on error
+         else
+               return new_page;
+
+#ifdef unix
+       if( pwrite(bt->idx, page, bt->page_size, new_page << bt->page_bits) < bt->page_size )
+               return bt->err = BTERR_wrt, 0;
+
+       // if writing first page of pool block, zero last page in the block
+
+       if( !reuse && bt->hashmask > 0 && (new_page & bt->hashmask) == 0 )
+       {
+               // use zero buffer to write zeros
+               if( pwrite(bt->idx,bt->zero, bt->page_size, (new_page | bt->hashmask) << bt->page_bits) < bt->page_size )
+                       return bt->err = BTERR_wrt, 0;
+       }
+#else
+       //      bring new page into pool and copy page.
+       //      this will extend the file into the new pages.
+
+       if( bt_mappage (bt, &bt->temp, new_page) )
+               return 0;
+
+       memcpy(bt->temp, page, bt->page_size);
+#endif
+       return new_page;
+}
+
+//  compare two keys, returning > 0, = 0, or < 0
+//  as the comparison value
+
+int keycmp (BtKey key1, unsigned char *key2, uint len2)
+{
+uint len1 = key1->len;
+int ans;
+
+       if( ans = memcmp (key1->key, key2, len1 > len2 ? len2 : len1) )
+               return ans;
+
+       if( len1 > len2 )
+               return 1;
+       if( len1 < len2 )
+               return -1;
+
+       return 0;
+}
+
+//  Update current page of btree by writing file contents
+//     or flushing mapped area to disk.
+
+BTERR bt_update (BtDb *bt, BtPage page, uid page_no)
+{
+off64_t off = page_no << bt->page_bits;
+
+#ifdef unix
+    if( !bt->mapped_io )
+        if( pwrite(bt->idx, page, bt->page_size, off) != bt->page_size )
+                return bt->err = BTERR_wrt;
+#else
+uint amt[1];
+       if( !bt->mapped_io )
+       {
+               SetFilePointer (bt->idx, (long)off, (long*)(&off)+1, FILE_BEGIN);
+               if( !WriteFile (bt->idx, (char *)page, bt->page_size, amt, NULL) )
+                       return GetLastError(), bt->err = BTERR_wrt;
+
+               if( *amt < bt->page_size )
+                       return GetLastError(), bt->err = BTERR_wrt;
+       } 
+       else if( bt->mode == BT_fl ) {
+                       FlushViewOfFile(page, bt->page_size);
+                       FlushFileBuffers(bt->idx);
+       }
+#endif
+       return 0;
+}
+
+// find page in cache 
+
+BtHash *bt_findhash(BtDb *bt, uid page_no)
+{
+BtHash *hash;
+uint idx;
+
+       // compute cache block first page and hash idx 
+
+       page_no &= ~bt->hashmask;
+       idx = (uint)(page_no >> bt->seg_bits) % bt->hashsize;
+
+       if( bt->cache[idx] ) 
+               hash = bt->nodes + bt->cache[idx];
+       else
+               return NULL;
+
+       do if( hash->page_no == page_no )
+                break;
+       while(hash = hash->hashnext );
+
+       return hash;
+}
+
+// add page cache entry to hash index
+
+void bt_linkhash(BtDb *bt, BtHash *node, uid page_no)
+{
+uint idx = (uint)(page_no >> bt->seg_bits) % bt->hashsize;
+BtHash *hash;
+
+       if( bt->cache[idx] ) {
+               node->hashnext = hash = bt->nodes + bt->cache[idx];
+               hash->hashprev = node;
+       }
+
+       node->hashprev = NULL;
+       bt->cache[idx] = (ushort)(node - bt->nodes);
+}
+
+// remove cache entry from hash table
+
+void bt_unlinkhash(BtDb *bt, BtHash *node)
+{
+uint idx = (uint)(node->page_no >> bt->seg_bits) % bt->hashsize;
+BtHash *hash;
+
+       // unlink node
+       if( hash = node->hashprev )
+               hash->hashnext = node->hashnext;
+       else if( hash = node->hashnext )
+               bt->cache[idx] = (ushort)(hash - bt->nodes);
+       else
+               bt->cache[idx] = 0;
+
+       if( hash = node->hashnext )
+               hash->hashprev = node->hashprev;
+}
+
+// add cache page to lru chain and map pages
+
+BtPage bt_linklru(BtDb *bt, BtHash *hash, uid page_no)
+{
+int flag;
+off64_t off = (page_no & ~bt->hashmask) << bt->page_bits;
+off64_t limit = off + ((bt->hashmask+1) << bt->page_bits);
+BtHash *node;
+
+       memset(hash, 0, sizeof(BtHash));
+       hash->page_no = (page_no & ~bt->hashmask);
+       bt_linkhash(bt, hash, page_no);
+
+       if( node = hash->lrunext = bt->lrufirst )
+               node->lruprev = hash;
+       else
+               bt->lrulast = hash;
+
+       bt->lrufirst = hash;
+
+#ifdef unix
+       flag = PROT_READ | ( bt->mode == BT_ro ? 0 : PROT_WRITE );
+       hash->page = (BtPage)mmap (0, (bt->hashmask+1) << bt->page_bits, flag, MAP_SHARED, bt->idx, off);
+       if( hash->page == MAP_FAILED )
+               return bt->err = BTERR_map, (BtPage)NULL;
+
+#else
+       flag = ( bt->mode == BT_ro ? PAGE_READONLY : PAGE_READWRITE );
+       hash->hmap = CreateFileMapping(bt->idx, NULL, flag,     (DWORD)(limit >> 32), (DWORD)limit, NULL);
+       if( !hash->hmap )
+               return bt->err = BTERR_map, NULL;
+
+       flag = ( bt->mode == BT_ro ? FILE_MAP_READ : FILE_MAP_WRITE );
+       hash->page = MapViewOfFile(hash->hmap, flag, (DWORD)(off >> 32), (DWORD)off, (bt->hashmask+1) << bt->page_bits);
+       if( !hash->page )
+               return bt->err = BTERR_map, NULL;
+#endif
+
+       return (BtPage)((char*)hash->page + ((uint)(page_no & bt->hashmask) << bt->page_bits));
+}
+
+//     find or place requested page in page-cache
+//     return memory address where page is located.
+
+BtPage bt_hashpage(BtDb *bt, uid page_no)
+{
+BtHash *hash, *node, *next;
+BtPage page;
+
+       // find page in cache and move to top of lru list  
+
+       if( hash = bt_findhash(bt, page_no) ) {
+               page = (BtPage)((char*)hash->page + ((uint)(page_no & bt->hashmask) << bt->page_bits));
+               // swap node in lru list
+               if( node = hash->lruprev ) {
+                       if( next = node->lrunext = hash->lrunext )
+                               next->lruprev = node;
+                       else
+                               bt->lrulast = node;
+
+                       if( next = hash->lrunext = bt->lrufirst )
+                               next->lruprev = hash;
+                       else
+                               return bt->err = BTERR_hash, (BtPage)NULL;
+
+                       hash->lruprev = NULL;
+                       bt->lrufirst = hash;
+               }
+               return page;
+       }
+
+       // map pages and add to cache entry
+
+       if( bt->nodecnt < bt->nodemax ) {
+               hash = bt->nodes + ++bt->nodecnt;
+               return bt_linklru(bt, hash, page_no);
+       }
+
+       // hash table is already full, replace last lru entry from the cache
+
+       if( hash = bt->lrulast ) {
+               // unlink from lru list
+               if( node = bt->lrulast = hash->lruprev )
+                       node->lrunext = NULL;
+               else
+                       return bt->err = BTERR_hash, (BtPage)NULL;
+
+#ifdef unix
+               munmap (hash->page, (bt->hashmask+1) << bt->page_bits);
+#else
+               FlushViewOfFile(hash->page, 0);
+               UnmapViewOfFile(hash->page);
+               CloseHandle(hash->hmap);
+#endif
+               // unlink from hash table
+
+               bt_unlinkhash(bt, hash);
+
+               // map and add to cache
+
+               return bt_linklru(bt, hash, page_no);
+       }
+
+       return bt->err = BTERR_hash, (BtPage)NULL;
+}
+
+//  map a btree page onto current page
+
+BTERR bt_mappage (BtDb *bt, BtPage *page, uid page_no)
+{
+off64_t off = page_no << bt->page_bits;
+#ifndef unix
+int amt[1];
+#endif
+       
+       if( bt->mapped_io ) {
+               bt->err = 0;
+               *page = bt_hashpage(bt, page_no);
+               return bt->err;
+       }
+#ifdef unix
+       if( pread(bt->idx, *page, bt->page_size, off) < bt->page_size )
+               return bt->err = BTERR_map;
+#else
+       SetFilePointer (bt->idx, (long)off, (long*)(&off)+1, FILE_BEGIN);
+
+       if( !ReadFile(bt->idx, *page, bt->page_size, amt, NULL) )
+               return bt->err = BTERR_map;
+
+       if( *amt <  bt->page_size )
+               return bt->err = BTERR_map;
+#endif
+       return 0;
+}
+
+//     deallocate a deleted page 
+//     place on free chain out of allocator page
+//     call with page latched for Writing and Deleting
+
+BTERR bt_freepage(BtDb *bt, uid page_no, BtPage page, BtLatchSet *latch)
+{
+       if( bt_mappage (bt, &page, page_no) )
+               return bt->err;
+
+       //      lock allocation page
+
+       bt_spinwritelock (bt->latchmgr->lock);
+
+       //      store chain in second right
+       bt_putid(page->right, bt_getid(bt->latchmgr->alloc[1].right));
+       bt_putid(bt->latchmgr->alloc[1].right, page_no);
+       page->free = 1;
+
+       if( bt_update(bt, page, page_no) )
+               return bt->err;
+
+       // unlock released page
+
+       bt_unlockpage (BtLockDelete, latch);
+       bt_unlockpage (BtLockWrite, latch);
+       bt_unpinlatch (latch);
+
+       // unlock allocation page
+
+       bt_spinreleasewrite (bt->latchmgr->lock);
+       return 0;
+}
+
+//  find slot in page for given key at a given level
+
+int bt_findslot (BtDb *bt, unsigned char *key, uint len)
+{
+uint diff, higher = bt->page->cnt, low = 1, slot;
+uint good = 0;
+
+       //      make stopper key an infinite fence value
+
+       if( bt_getid (bt->page->right) )
+               higher++;
+       else
+               good++;
+
+       //      low is the lowest candidate, higher is already
+       //      tested as .ge. the given key, loop ends when they meet
+
+       while( diff = higher - low ) {
+               slot = low + ( diff >> 1 );
+               if( keycmp (keyptr(bt->page, slot), key, len) < 0 )
+                       low = slot + 1;
+               else
+                       higher = slot, good++;
+       }
+
+       //      return zero if key is on right link page
+
+       return good ? higher : 0;
+}
+
+//  find and load page at given level for given key
+//     leave page rd or wr locked as requested
+
+int bt_loadpage (BtDb *bt, unsigned char *key, uint len, uint lvl, uint lock)
+{
+uid page_no = ROOT_page, prevpage = 0;
+uint drill = 0xff, slot;
+BtLatchSet *prevlatch;
+uint mode, prevmode;
+
+  //  start at root of btree and drill down
+
+  do {
+       // determine lock mode of drill level
+       mode = (lock == BtLockWrite) && (drill == lvl) ? BtLockWrite : BtLockRead; 
+
+       bt->latch = bt_pinlatch(bt, page_no);
+       bt->page_no = page_no;
+
+       // obtain access lock using lock chaining
+
+       if( page_no > ROOT_page )
+               bt_lockpage(BtLockAccess, bt->latch);
+
+       if( prevpage ) {
+               bt_unlockpage(prevmode, prevlatch);
+               bt_unpinlatch(prevlatch);
+               prevpage = 0;
+       }
+
+       // obtain read lock using lock chaining
+
+       bt_lockpage(mode, bt->latch);
+
+       if( page_no > ROOT_page )
+               bt_unlockpage(BtLockAccess, bt->latch);
+
+       //      map/obtain page contents
+
+       if( bt_mappage (bt, &bt->page, page_no) )
+               return 0;
+
+       // re-read and re-lock root after determining actual level of root
+
+       if( bt->page->lvl < drill) {
+               if( bt->page_no != ROOT_page )
+                       return bt->err = BTERR_struct, 0;
+                       
+               drill = bt->page->lvl;
+
+               if( lock != BtLockRead && drill == lvl ) {
+                       bt_unlockpage(mode, bt->latch);
+                       bt_unpinlatch(bt->latch);
+                       continue;
+               }
+       }
+
+       prevpage = bt->page_no;
+       prevlatch = bt->latch;
+       prevmode = mode;
+
+       //  find key on page at this level
+       //  and descend to requested level
+
+       if( !bt->page->kill )
+        if( slot = bt_findslot (bt, key, len) ) {
+         if( drill == lvl )
+               return slot;
+
+         while( slotptr(bt->page, slot)->dead )
+               if( slot++ < bt->page->cnt )
+                       continue;
+               else
+                       goto slideright;
+
+         page_no = bt_getid(slotptr(bt->page, slot)->id);
+         drill--;
+         continue;
+        }
+
+       //  or slide right into next page
+
+slideright:
+       page_no = bt_getid(bt->page->right);
+
+  } while( page_no );
+
+  // return error on end of right chain
+
+  bt->err = BTERR_eof;
+  return 0;    // return error
+}
+
+//     a fence key was deleted from a page
+//     push new fence value upwards
+
+BTERR bt_fixfence (BtDb *bt, uid page_no, uint lvl)
+{
+unsigned char leftkey[256], rightkey[256];
+BtLatchSet *latch = bt->latch;
+BtKey ptr;
+
+       // remove deleted key, the old fence value
+
+       ptr = keyptr(bt->page, bt->page->cnt);
+       memcpy(rightkey, ptr, ptr->len + 1);
+
+       memset (slotptr(bt->page, bt->page->cnt--), 0, sizeof(BtSlot));
+       bt->page->dirty = 1;
+
+       ptr = keyptr(bt->page, bt->page->cnt);
+       memcpy(leftkey, ptr, ptr->len + 1);
+
+       if( bt_update (bt, bt->page, page_no) )
+               return bt->err;
+
+       bt_lockpage (BtLockParent, latch);
+       bt_unlockpage (BtLockWrite, latch);
+
+       //  insert new (now smaller) fence key
+
+       if( bt_insertkey (bt, leftkey+1, *leftkey, lvl + 1, page_no, time(NULL)) )
+               return bt->err;
+
+       //  remove old (larger) fence key
+
+       if( bt_deletekey (bt, rightkey+1, *rightkey, lvl + 1) )
+               return bt->err;
+
+       bt_unlockpage (BtLockParent, latch);
+       bt_unpinlatch (latch);
+       return 0;
+}
+
+//     root has a single child
+//     collapse a level from the btree
+//     call with root locked in bt->page
+
+BTERR bt_collapseroot (BtDb *bt, BtPage root)
+{
+BtLatchSet *latch;
+uid child;
+uint idx;
+
+       // find the child entry
+       //      and promote to new root
+
+  do {
+       for( idx = 0; idx++ < root->cnt; )
+         if( !slotptr(root, idx)->dead )
+               break;
+
+       child = bt_getid (slotptr(root, idx)->id);
+       latch = bt_pinlatch (bt, child);
+
+       bt_lockpage (BtLockDelete, latch);
+       bt_lockpage (BtLockWrite, latch);
+
+       if( bt_mappage (bt, &bt->temp, child) )
+               return bt->err;
+
+       memcpy (root, bt->temp, bt->page_size);
+
+       if( bt_update (bt, root, ROOT_page) )
+               return bt->err;
+
+       if( bt_freepage (bt, child, bt->temp, latch) )
+               return bt->err;
+
+  } while( root->lvl > 1 && root->act == 1 );
+
+  bt_unlockpage (BtLockWrite, bt->latch);
+  bt_unpinlatch (bt->latch);
+  return 0;
+}
+
+//  find and delete key on page by marking delete flag bit
+//  when page becomes empty, delete it
+
+BTERR bt_deletekey (BtDb *bt, unsigned char *key, uint len, uint lvl)
+{
+unsigned char lowerkey[256], higherkey[256];
+uint slot, dirty = 0, idx, fence, found;
+BtLatchSet *latch, *rlatch;
+uid page_no, right;
+BtKey ptr;
+
+       if( slot = bt_loadpage (bt, key, len, lvl, BtLockWrite) )
+               ptr = keyptr(bt->page, slot);
+       else
+               return bt->err;
+
+       // are we deleting a fence slot?
+
+       fence = slot == bt->page->cnt;
+
+       // if key is found delete it, otherwise ignore request
+
+       if( found = !keycmp (ptr, key, len) )
+         if( found = slotptr(bt->page, slot)->dead == 0 ) {
+               dirty = slotptr(bt->page,slot)->dead = 1;
+               bt->page->dirty = 1;
+               bt->page->act--;
+
+               // collapse empty slots
+
+               while( idx = bt->page->cnt - 1 )
+                 if( slotptr(bt->page, idx)->dead ) {
+                       *slotptr(bt->page, idx) = *slotptr(bt->page, idx + 1);
+                       memset (slotptr(bt->page, bt->page->cnt--), 0, sizeof(BtSlot));
+                 } else
+                       break;
+         }
+
+       right = bt_getid(bt->page->right);
+       page_no = bt->page_no;
+       latch = bt->latch;
+
+       if( !dirty ) {
+         if( lvl )
+               return bt_abort (bt, bt->page, page_no, BTERR_notfound);
+         bt_unlockpage(BtLockWrite, latch);
+         bt_unpinlatch (latch);
+         return bt->found = found, 0;
+       }
+
+       //      did we delete a fence key in an upper level?
+
+       if( lvl && bt->page->act && fence )
+         if( bt_fixfence (bt, page_no, lvl) )
+               return bt->err;
+         else
+               return bt->found = found, 0;
+
+       //      is this a collapsed root?
+
+       if( lvl > 1 && page_no == ROOT_page && bt->page->act == 1 )
+         if( bt_collapseroot (bt, bt->page) )
+               return bt->err;
+         else
+               return bt->found = found, 0;
+
+       // return if page is not empty
+
+       if( bt->page->act ) {
+         if( bt_update(bt, bt->page, page_no) )
+               return bt->err;
+         bt_unlockpage(BtLockWrite, latch);
+         bt_unpinlatch (latch);
+         return bt->found = found, 0;
+       }
+
+       // cache copy of fence key
+       //      in order to find parent
+
+       ptr = keyptr(bt->page, bt->page->cnt);
+       memcpy(lowerkey, ptr, ptr->len + 1);
+
+       // obtain lock on right page
+
+       rlatch = bt_pinlatch (bt, right);
+       bt_lockpage(BtLockWrite, rlatch);
+
+       if( bt_mappage (bt, &bt->temp, right) )
+               return bt->err;
+
+       if( bt->temp->kill ) {
+               bt_abort(bt, bt->temp, right, 0);
+               return bt_abort(bt, bt->page, bt->page_no, BTERR_kill);
+       }
+
+       // pull contents of next page into current empty page 
+
+       memcpy (bt->page, bt->temp, bt->page_size);
+
+       //      cache copy of key to update
+
+       ptr = keyptr(bt->temp, bt->temp->cnt);
+       memcpy(higherkey, ptr, ptr->len + 1);
+
+       //  Mark right page as deleted and point it to left page
+       //      until we can post updates at higher level.
+
+       bt_putid(bt->temp->right, page_no);
+       bt->temp->kill = 1;
+
+       if( bt_update(bt, bt->page, page_no) )
+               return bt->err;
+
+       if( bt_update(bt, bt->temp, right) )
+               return bt->err;
+
+       bt_lockpage(BtLockParent, latch);
+       bt_unlockpage(BtLockWrite, latch);
+
+       bt_lockpage(BtLockParent, rlatch);
+       bt_unlockpage(BtLockWrite, rlatch);
+
+       //  redirect higher key directly to consolidated node
+
+       if( bt_insertkey (bt, higherkey+1, *higherkey, lvl+1, page_no, time(NULL)) )
+               return bt->err;
+
+       //  delete old lower key to consolidated node
+
+       if( bt_deletekey (bt, lowerkey + 1, *lowerkey, lvl + 1) )
+               return bt->err;
+
+       //  obtain write & delete lock on deleted node
+       //      add right block to free chain
+
+       bt_lockpage(BtLockDelete, rlatch);
+       bt_lockpage(BtLockWrite, rlatch);
+       bt_unlockpage(BtLockParent, rlatch);
+
+       if( bt_freepage (bt, right, bt->temp, rlatch) )
+               return bt->err;
+
+       bt_unlockpage(BtLockParent, latch);
+       bt_unpinlatch(latch);
+       return 0;
+}
+
+//     find key in leaf level and return row-id
+
+uid bt_findkey (BtDb *bt, unsigned char *key, uint len)
+{
+uint  slot;
+BtKey ptr;
+uid id;
+
+       if( slot = bt_loadpage (bt, key, len, 0, BtLockRead) )
+               ptr = keyptr(bt->page, slot);
+       else
+               return 0;
+
+       // if key exists, return row-id
+       //      otherwise return 0
+
+       if( ptr->len == len && !memcmp (ptr->key, key, len) )
+               id = bt_getid(slotptr(bt->page,slot)->id);
+       else
+               id = 0;
+
+       bt_unlockpage (BtLockRead, bt->latch);
+       bt_unpinlatch (bt->latch);
+       return id;
+}
+
+//     check page for space available,
+//     clean if necessary and return
+//     0 - page needs splitting
+//     >0 - go ahead with new slot
+uint bt_cleanpage(BtDb *bt, uint amt, uint slot)
+{
+uint nxt = bt->page_size;
+BtPage page = bt->page;
+uint cnt = 0, idx = 0;
+uint max = page->cnt;
+uint newslot = slot;
+BtKey key;
+int ret;
+
+       if( page->min >= (max+1) * sizeof(BtSlot) + sizeof(*page) + amt + 1 )
+               return slot;
+
+       //      skip cleanup if nothing to reclaim
+
+       if( !page->dirty )
+               return 0;
+
+       memcpy (bt->frame, page, bt->page_size);
+
+       // skip page info and set rest of page to zero
+
+       memset (page+1, 0, bt->page_size - sizeof(*page));
+       page->act = 0;
+
+       while( cnt++ < max ) {
+               if( cnt == slot )
+                       newslot = idx + 1;
+               // always leave fence key in list
+               if( cnt < max && slotptr(bt->frame,cnt)->dead )
+                       continue;
+
+               // copy key
+               key = keyptr(bt->frame, cnt);
+               nxt -= key->len + 1;
+               memcpy ((unsigned char *)page + nxt, key, key->len + 1);
+
+               // copy slot
+               memcpy(slotptr(page, ++idx)->id, slotptr(bt->frame, cnt)->id, BtId);
+               if( !(slotptr(page, idx)->dead = slotptr(bt->frame, cnt)->dead) )
+                       page->act++;
+               slotptr(page, idx)->tod = slotptr(bt->frame, cnt)->tod;
+               slotptr(page, idx)->off = nxt;
+       }
+
+       page->min = nxt;
+       page->cnt = idx;
+
+       if( page->min >= (max+1) * sizeof(BtSlot) + sizeof(*page) + amt + 1 )
+               return newslot;
+
+       return 0;
+}
+
+// split the root and raise the height of the btree
+
+BTERR bt_splitroot(BtDb *bt, unsigned char *leftkey, uid page_no2)
+{
+uint nxt = bt->page_size;
+BtPage root = bt->page;
+uid right;
+
+       //  Obtain an empty page to use, and copy the current
+       //  root contents into it
+
+       if( !(right = bt_newpage(bt, root)) )
+               return bt->err;
+
+       // preserve the page info at the bottom
+       // and set rest to zero
+
+       memset(root+1, 0, bt->page_size - sizeof(*root));
+
+       // insert first key on newroot page
+
+       nxt -= *leftkey + 1;
+       memcpy ((unsigned char *)root + nxt, leftkey, *leftkey + 1);
+       bt_putid(slotptr(root, 1)->id, right);
+       slotptr(root, 1)->off = nxt;
+       
+       // insert second key on newroot page
+       // and increase the root height
+
+       nxt -= 3;
+       ((unsigned char *)root)[nxt] = 2;
+       ((unsigned char *)root)[nxt+1] = 0xff;
+       ((unsigned char *)root)[nxt+2] = 0xff;
+       bt_putid(slotptr(root, 2)->id, page_no2);
+       slotptr(root, 2)->off = nxt;
+
+       bt_putid(root->right, 0);
+       root->min = nxt;                // reset lowest used offset and key count
+       root->cnt = 2;
+       root->act = 2;
+       root->lvl++;
+
+       // update and release root (bt->page)
+
+       if( bt_update(bt, root, bt->page_no) )
+               return bt->err;
+
+       bt_unlockpage(BtLockWrite, bt->latch);
+       bt_unpinlatch(bt->latch);
+       return 0;
+}
+
+//  split already locked full node
+//     return unlocked.
+
+BTERR bt_splitpage (BtDb *bt)
+{
+uint cnt = 0, idx = 0, max, nxt = bt->page_size;
+unsigned char fencekey[256], rightkey[256];
+uid page_no = bt->page_no, right;
+BtLatchSet *latch, *rlatch;
+BtPage page = bt->page;
+uint lvl = page->lvl;
+BtKey key;
+
+       latch = bt->latch;
+
+       //  split higher half of keys to bt->frame
+       //      the last key (fence key) might be dead
+
+       memset (bt->frame, 0, bt->page_size);
+       max = page->cnt;
+       cnt = max / 2;
+       idx = 0;
+
+       while( cnt++ < max ) {
+               key = keyptr(page, cnt);
+               nxt -= key->len + 1;
+               memcpy ((unsigned char *)bt->frame + nxt, key, key->len + 1);
+               memcpy(slotptr(bt->frame,++idx)->id, slotptr(page,cnt)->id, BtId);
+               if( !(slotptr(bt->frame, idx)->dead = slotptr(page, cnt)->dead) )
+                       bt->frame->act++;
+               slotptr(bt->frame, idx)->tod = slotptr(page, cnt)->tod;
+               slotptr(bt->frame, idx)->off = nxt;
+       }
+
+       //      remember fence key for new right page
+
+       memcpy (rightkey, key, key->len + 1);
+
+       bt->frame->bits = bt->page_bits;
+       bt->frame->min = nxt;
+       bt->frame->cnt = idx;
+       bt->frame->lvl = lvl;
+
+       // link right node
+
+       if( page_no > ROOT_page )
+               memcpy (bt->frame->right, page->right, BtId);
+
+       //      get new free page and write frame to it.
+
+       if( !(right = bt_newpage(bt, bt->frame)) )
+               return bt->err;
+
+       //      update lower keys to continue in old page
+
+       memcpy (bt->frame, page, bt->page_size);
+       memset (page+1, 0, bt->page_size - sizeof(*page));
+       nxt = bt->page_size;
+       page->dirty = 0;
+       page->act = 0;
+       cnt = 0;
+       idx = 0;
+
+       //  assemble page of smaller keys
+       //      (they're all active keys)
+
+       while( cnt++ < max / 2 ) {
+               key = keyptr(bt->frame, cnt);
+               nxt -= key->len + 1;
+               memcpy ((unsigned char *)page + nxt, key, key->len + 1);
+               memcpy(slotptr(page,++idx)->id, slotptr(bt->frame,cnt)->id, BtId);
+               slotptr(page, idx)->tod = slotptr(bt->frame, cnt)->tod;
+               slotptr(page, idx)->off = nxt;
+               page->act++;
+       }
+
+       // remember fence key for smaller page
+
+       memcpy (fencekey, key, key->len + 1);
+
+       bt_putid(page->right, right);
+       page->min = nxt;
+       page->cnt = idx;
+
+       // if current page is the root page, split it
+
+       if( page_no == ROOT_page )
+               return bt_splitroot (bt, fencekey, right);
+
+       //      lock right page
+
+       rlatch = bt_pinlatch (bt, right);
+       bt_lockpage (BtLockParent, rlatch);
+
+       // update left (containing) node
+
+       if( bt_update(bt, page, page_no) )
+               return bt->err;
+
+       bt_lockpage (BtLockParent, latch);
+       bt_unlockpage (BtLockWrite, latch);
+
+       // insert new fence for reformulated left block
+
+       if( bt_insertkey (bt, fencekey+1, *fencekey, lvl+1, page_no, time(NULL)) )
+               return bt->err;
+
+       //      switch fence for right block of larger keys to new right page
+
+       if( bt_insertkey (bt, rightkey+1, *rightkey, lvl+1, right, time(NULL)) )
+               return bt->err;
+
+       bt_unlockpage (BtLockParent, latch);
+       bt_unlockpage (BtLockParent, rlatch);
+
+       bt_unpinlatch (rlatch);
+       bt_unpinlatch (latch);
+       return 0;
+}
+
+//  Insert new key into the btree at requested level.
+//  Pages are unlocked at exit.
+
+BTERR bt_insertkey (BtDb *bt, unsigned char *key, uint len, uint lvl, uid id, uint tod)
+{
+uint slot, idx;
+BtPage page;
+BtKey ptr;
+
+  while( 1 ) {
+       if( slot = bt_loadpage (bt, key, len, lvl, BtLockWrite) )
+               ptr = keyptr(bt->page, slot);
+       else
+       {
+               if( !bt->err )
+                       bt->err = BTERR_ovflw;
+               return bt->err;
+       }
+
+       // if key already exists, update id and return
+
+       page = bt->page;
+
+       if( !keycmp (ptr, key, len) ) {
+         if( slotptr(page, slot)->dead )
+               page->act++;
+         slotptr(page, slot)->dead = 0;
+         slotptr(page, slot)->tod = tod;
+         bt_putid(slotptr(page,slot)->id, id);
+         if( bt_update(bt, bt->page, bt->page_no) )
+               return bt->err;
+         bt_unlockpage(BtLockWrite, bt->latch);
+         bt_unpinlatch (bt->latch);
+         return 0;
+       }
+
+       // check if page has enough space
+
+       if( slot = bt_cleanpage (bt, len, slot) )
+               break;
+
+       if( bt_splitpage (bt) )
+               return bt->err;
+  }
+
+  // calculate next available slot and copy key into page
+
+  page->min -= len + 1; // reset lowest used offset
+  ((unsigned char *)page)[page->min] = len;
+  memcpy ((unsigned char *)page + page->min +1, key, len );
+
+  for( idx = slot; idx < page->cnt; idx++ )
+       if( slotptr(page, idx)->dead )
+               break;
+
+  // now insert key into array before slot
+  // preserving the fence slot
+
+  if( idx == page->cnt )
+       idx++, page->cnt++;
+
+  page->act++;
+
+  while( idx > slot )
+       *slotptr(page, idx) = *slotptr(page, idx -1), idx--;
+
+  bt_putid(slotptr(page,slot)->id, id);
+  slotptr(page, slot)->off = page->min;
+  slotptr(page, slot)->tod = tod;
+  slotptr(page, slot)->dead = 0;
+
+  if( bt_update(bt, bt->page, bt->page_no) )
+         return bt->err;
+
+  bt_unlockpage(BtLockWrite, bt->latch);
+  bt_unpinlatch(bt->latch);
+  return 0;
+}
+
+//  cache page of keys into cursor and return starting slot for given key
+
+uint bt_startkey (BtDb *bt, unsigned char *key, uint len)
+{
+uint slot;
+
+       // cache page for retrieval
+
+       if( slot = bt_loadpage (bt, key, len, 0, BtLockRead) )
+         memcpy (bt->cursor, bt->page, bt->page_size);
+       else
+         return 0;
+
+       bt_unlockpage(BtLockRead, bt->latch);
+       bt->cursor_page = bt->page_no;
+       bt_unpinlatch (bt->latch);
+       return slot;
+}
+
+//  return next slot for cursor page
+//  or slide cursor right into next page
+
+uint bt_nextkey (BtDb *bt, uint slot)
+{
+BtLatchSet *latch;
+off64_t right;
+
+  do {
+       right = bt_getid(bt->cursor->right);
+
+       while( slot++ < bt->cursor->cnt )
+         if( slotptr(bt->cursor,slot)->dead )
+               continue;
+         else if( right || (slot < bt->cursor->cnt))
+               return slot;
+         else
+               break;
+
+       if( !right )
+               break;
+
+       bt->cursor_page = right;
+       latch = bt_pinlatch (bt, right);
+    bt_lockpage(BtLockRead, latch);
+
+       if( bt_mappage (bt, &bt->page, right) )
+               return 0;
+
+       memcpy (bt->cursor, bt->page, bt->page_size);
+       bt_unlockpage(BtLockRead, latch);
+       bt_unpinlatch (latch);
+       slot = 0;
+  } while( 1 );
+
+  return bt->err = 0;
+}
+
+BtKey bt_key(BtDb *bt, uint slot)
+{
+       return keyptr(bt->cursor, slot);
+}
+
+uid bt_uid(BtDb *bt, uint slot)
+{
+       return bt_getid(slotptr(bt->cursor,slot)->id);
+}
+
+uint bt_tod(BtDb *bt, uint slot)
+{
+       return slotptr(bt->cursor,slot)->tod;
+}
+
+
+#ifdef STANDALONE
+
+uint bt_audit (BtDb *bt)
+{
+ushort idx, hashidx;
+uid next, page_no;
+BtLatchSet *latch;
+uint cnt = 0;
+BtKey ptr;
+
+#ifdef unix
+       if( *(uint *)(bt->latchmgr->lock) )
+               fprintf(stderr, "Alloc page locked\n");
+       *(uint *)(bt->latchmgr->lock) = 0;
+
+       for( idx = 1; idx < bt->latchmgr->latchdeployed; idx++ ) {
+               latch = bt->latchsets + idx;
+               if( *(uint *)latch->readwr )
+                       fprintf(stderr, "latchset %d rwlocked for page %.8x\n", idx, latch->page_no);
+               *(uint *)latch->readwr = 0;
+
+               if( *(uint *)latch->access )
+                       fprintf(stderr, "latchset %d accesslocked for page %.8x\n", idx, latch->page_no);
+               *(uint *)latch->access = 0;
+
+               if( *(uint *)latch->parent )
+                       fprintf(stderr, "latchset %d parentlocked for page %.8x\n", idx, latch->page_no);
+               *(uint *)latch->parent = 0;
+
+               if( latch->pin ) {
+                       fprintf(stderr, "latchset %d pinned for page %.8x\n", idx, latch->page_no);
+                       latch->pin = 0;
+               }
+       }
+
+       for( hashidx = 0; hashidx < bt->latchmgr->latchhash; hashidx++ ) {
+         if( *(uint *)(bt->latchmgr->table[hashidx].latch) )
+                       fprintf(stderr, "hash entry %d locked\n", hashidx);
+
+         *(uint *)(bt->latchmgr->table[hashidx].latch) = 0;
+
+         if( idx = bt->latchmgr->table[hashidx].slot ) do {
+               latch = bt->latchsets + idx;
+               if( *(uint *)latch->busy )
+                       fprintf(stderr, "latchset %d busylocked for page %.8x\n", idx, latch->page_no);
+               *(uint *)latch->busy = 0;
+               if( latch->hash != hashidx )
+                       fprintf(stderr, "latchset %d wrong hashidx\n", idx);
+               if( latch->pin )
+                       fprintf(stderr, "latchset %d pinned for page %.8x\n", idx, latch->page_no);
+         } while( idx = latch->next );
+       }
+
+       next = bt->latchmgr->nlatchpage + LATCH_page;
+       page_no = LEAF_page;
+
+       while( page_no < bt_getid(bt->latchmgr->alloc->right) ) {
+               pread (bt->idx, bt->frame, bt->page_size, page_no << bt->page_bits);
+               if( !bt->frame->free ) {
+                for( idx = 0; idx++ < bt->frame->cnt - 1; ) {
+                 ptr = keyptr(bt->frame, idx+1);
+                 if( keycmp (keyptr(bt->frame, idx), ptr->key, ptr->len) >= 0 )
+                       fprintf(stderr, "page %.8x idx %.2x out of order\n", page_no, idx);
+                }
+                if( !bt->frame->lvl )
+                       cnt += bt->frame->act;
+               }
+
+               if( page_no > LEAF_page )
+                       next = page_no + 1;
+               page_no = next;
+       }
+       return cnt - 1;
+#endif
+}
+
+#ifndef unix
+double getCpuTime(int type)
+{
+FILETIME crtime[1];
+FILETIME xittime[1];
+FILETIME systime[1];
+FILETIME usrtime[1];
+SYSTEMTIME timeconv[1];
+double ans = 0;
+
+       memset (timeconv, 0, sizeof(SYSTEMTIME));
+
+       switch( type ) {
+       case 0:
+               GetSystemTimeAsFileTime (xittime);
+               FileTimeToSystemTime (xittime, timeconv);
+               ans = (double)timeconv->wDayOfWeek * 3600 * 24;
+               break;
+       case 1:
+               GetProcessTimes (GetCurrentProcess(), crtime, xittime, systime, usrtime);
+               FileTimeToSystemTime (usrtime, timeconv);
+               break;
+       case 2:
+               GetProcessTimes (GetCurrentProcess(), crtime, xittime, systime, usrtime);
+               FileTimeToSystemTime (systime, timeconv);
+               break;
+       }
+
+       ans += (double)timeconv->wHour * 3600;
+       ans += (double)timeconv->wMinute * 60;
+       ans += (double)timeconv->wSecond;
+       ans += (double)timeconv->wMilliseconds / 1000;
+       return ans;
+}
+#else
+#include <time.h>
+#include <sys/resource.h>
+
+double getCpuTime(int type)
+{
+struct rusage used[1];
+struct timeval tv[1];
+
+       switch( type ) {
+       case 0:
+               gettimeofday(tv, NULL);
+               return (double)tv->tv_sec + (double)tv->tv_usec / 1000000;
+
+       case 1:
+               getrusage(RUSAGE_SELF, used);
+               return (double)used->ru_utime.tv_sec + (double)used->ru_utime.tv_usec / 1000000;
+
+       case 2:
+               getrusage(RUSAGE_SELF, used);
+               return (double)used->ru_stime.tv_sec + (double)used->ru_stime.tv_usec / 1000000;
+       }
+
+       return 0;
+}
+#endif
+
+//  standalone program to index file of keys
+//  then list them onto std-out
+
+int main (int argc, char **argv)
+{
+uint slot, line = 0, off = 0, found = 0;
+int ch, cnt = 0, bits = 12;
+unsigned char key[256];
+double done, start;
+uid next, page_no;
+uint pgblk = 0;
+float elapsed;
+time_t tod[1];
+uint scan = 0;
+uint len = 0;
+uint map = 0;
+BtKey ptr;
+BtDb *bt;
+FILE *in;
+
+       if( argc < 4 ) {
+               fprintf (stderr, "Usage: %s idx_file src_file Read/Write/Scan/Delete/Find [page_bits mapped_pool_segments pages_per_segment start_line_number]\n", argv[0]);
+               fprintf (stderr, "  page_bits: size of btree page in bits\n");
+               fprintf (stderr, "  mapped_pool_segments: size of buffer pool in segments\n");
+               fprintf (stderr, "  pages_per_segment: size of buffer pool segment in pages in bits\n");
+               exit(0);
+       }
+
+       start = getCpuTime(0);
+       time(tod);
+
+       if( argc > 4 )
+               bits = atoi(argv[4]);
+
+       if( argc > 5 )
+               map = atoi(argv[5]);
+
+       if( map > 65536 )
+               fprintf (stderr, "Warning: buffer_pool > 65536 segments\n");
+
+       if( map && map < 8 )
+               fprintf (stderr, "Buffer_pool too small\n");
+
+       if( argc > 6 )
+               pgblk = atoi(argv[6]);
+
+       if( bits + pgblk > 30 )
+               fprintf (stderr, "Warning: very large buffer pool segment size\n");
+
+       if( argc > 7 )
+               off = atoi(argv[7]);
+
+       bt = bt_open ((argv[1]), BT_rw, bits, map, pgblk, map /  8);
+
+       if( !bt ) {
+               fprintf(stderr, "Index Open Error %s\n", argv[1]);
+               exit (1);
+       }
+
+       switch(argv[3][0]| 0x20)
+       {
+       case 'a':
+               fprintf(stderr, "started audit for %s\n", argv[2]);
+               cnt = bt_audit (bt);
+               fprintf(stderr, "finished audit for %s, %d keys\n", argv[2], cnt);
+               break;
+
+       case 'w':
+               fprintf(stderr, "started indexing for %s\n", argv[2]);
+               if( argc > 2 && (in = fopen (argv[2], "rb")) )
+                 while( ch = getc(in), ch != EOF )
+                       if( ch == '\n' )
+                       {
+                         if( off )
+                               sprintf((char *)key+len, "%.9d", line + off), len += 9;
+
+                         if( bt_insertkey (bt, key, len, 0, ++line, *tod) )
+                               fprintf(stderr, "Error %d Line: %d\n", bt->err, line), exit(0);
+                         len = 0;
+                       }
+                       else if( len < 245 )
+                               key[len++] = ch;
+               fprintf(stderr, "finished adding keys for %s, %d \n", argv[2], line);
+               break;
+
+       case 'd':
+               fprintf(stderr, "started deleting keys for %s\n", argv[2]);
+               if( argc > 2 && (in = fopen (argv[2], "rb")) )
+                 while( ch = getc(in), ch != EOF )
+                       if( ch == '\n' )
+                       {
+                         if( off )
+                               sprintf((char *)key+len, "%.9d", line + off), len += 9;
+                         line++;
+                         if( bt_deletekey (bt, key, len, 0) )
+                               fprintf(stderr, "Error %d Line: %d\n", bt->err, line), exit(0);
+                         len = 0;
+                       }
+                       else if( len < 245 )
+                               key[len++] = ch;
+               fprintf(stderr, "finished deleting keys for %s, %d \n", argv[2], line);
+               break;
+
+       case 'f':
+               fprintf(stderr, "started finding keys for %s\n", argv[2]);
+               if( argc > 2 && (in = fopen (argv[2], "rb")) )
+                 while( ch = getc(in), ch != EOF )
+                       if( ch == '\n' )
+                       {
+                         if( off )
+                               sprintf((char *)key+len, "%.9d", line + off), len += 9;
+                         line++;
+                         if( bt_findkey (bt, key, len) )
+                               found++;
+                         else if( bt->err )
+                               fprintf(stderr, "Error %d Syserr %d Line: %d\n", bt->err, errno, line), exit(0);
+                         len = 0;
+                       }
+                       else if( len < 245 )
+                               key[len++] = ch;
+               fprintf(stderr, "finished search of %d keys for %s, found %d\n", line, argv[2], found);
+               break;
+
+       case 's':
+               scan++;
+
+       case 'c':
+         cnt = 0;
+
+         fprintf(stderr, "started reading\n");
+
+         next = bt->latchmgr->nlatchpage + LATCH_page;
+         page_no = LEAF_page;
+
+         while( page_no < bt_getid(bt->latchmgr->alloc->right) ) {
+         uid off = page_no << bt->page_bits;
+#ifdef unix
+               pread (bt->idx, bt->frame, bt->page_size, off);
+#else
+               DWORD amt[1];
+
+               SetFilePointer (bt->idx, (long)off, (long*)(&off)+1, FILE_BEGIN);
+
+               if( !ReadFile(bt->idx, bt->frame, bt->page_size, amt, NULL))
+                       return bt->err = BTERR_map;
+
+               if( *amt <  bt->page_size )
+                       return bt->err = BTERR_map;
+#endif
+               if( !bt->frame->free && !bt->frame->lvl )
+                       cnt += bt->frame->act;
+               if( page_no > LEAF_page )
+                       next = page_no + 1;
+               page_no = next;
+         }
+               
+         cnt--;        // remove stopper key
+         fprintf(stderr, " Total keys read %d\n", cnt);
+         break;
+       }
+
+       done = getCpuTime(0);
+       elapsed = (float)(done - start);
+       fprintf(stderr, " real %dm%.3fs\n", (int)(elapsed/60), elapsed - (int)(elapsed/60)*60);
+       elapsed = getCpuTime(1);
+       fprintf(stderr, " user %dm%.3fs\n", (int)(elapsed/60), elapsed - (int)(elapsed/60)*60);
+       elapsed = getCpuTime(2);
+       fprintf(stderr, " sys  %dm%.3fs\n", (int)(elapsed/60), elapsed - (int)(elapsed/60)*60);
+       return 0;
+}
+
+#endif //STANDALONE