-/* ----------------------------------------------------------------------------
- * $Id$
- * ----------------------------------------------------------------------------
- * Public Domain C Library - http://pdclib.sourceforge.net
- * This code is Public Domain. Use, modify, and redistribute at will.
- * --------------------------------------------------------------------------*/
+/* $Id$ */
-#include <__size_t.h>
+/* void * malloc( size_t )
-void * malloc( size_t size ) { /* TODO */ };
+ This file is part of the Public Domain C Library (PDCLib).
+ Permission is granted to use, modify, and / or redistribute at will.
+*/
-/* This is a simple best-fit / first-fit implementation heavily based on
- * Thomas "Beyond Infinity" Kreitner's code
- */
+#include <stdlib.h>
+#include <stdint.h>
-/* memory list element */
-struct chunk_t
-{
- void * address;
- size_t size;
- chunk_t * next;
-};
-
-struct memlist_t
-{
- chunk_t * start;
- chunk_t * last;
-};
+#ifndef REGTEST
-size_t heap_start = 0xa0000000;
-size_t heap_used = 0x00000050; /* HEAP in use. Holds the next FREE address (?) */
-size_t heap_max = 0xfffffff; /* max. HEAP */
+#ifndef _PDCLIB_GLUE_H
+#define _PDCLIB_GLUE_H _PDLIB_GLUE_H
+#include <_PDCLIB_glue.h>
+#endif
-static struct memlist_t free_mem = { (struct memlist_t *) heap_start,
- (struct memlist_t *) heap_start };
-/* free_mem.start->next = NULL; */
+/* TODO: Primitive placeholder. Much room for improvement. */
-static struct memlist_t used_mem = { (struct memlist_t *) heap_start + sizeof( chunk_t ),
- (struct memlist_t *) heap_start + sizeof( chunk_t ) };
-/* used_mem.start->next = NULL; */
+/* Keeping pointers to the first and the last element of the free list. */
+struct _PDCLIB_headnode_t _PDCLIB_memlist = { NULL, NULL };
void * malloc( size_t size )
{
- chunk_t * chunk = 0;
- chunk_t * prev_chunk;
- if ( free_mem.start != free_mem.last )
+ if ( size == 0 )
{
- /* first pass: exact fit */
- chunk = free_mem.start;
- while ( 1 )
- {
- prev_chunk = chunk;
- chunk = chunk->next;
- if ( ( chunk == NULL ) || ( chunk->size == size ) )
- {
- break;
- }
- }
+ return NULL;
}
- if ( chunk == NULL )
+ if ( size < _PDCLIB_MINALLOC )
+ {
+ size = _PDCLIB_MINALLOC;
+ }
+ {
+ struct _PDCLIB_memnode_t * current = _PDCLIB_memlist.first;
+ struct _PDCLIB_memnode_t * previous = NULL;
+ struct _PDCLIB_memnode_t * firstfit = NULL;
+ struct _PDCLIB_memnode_t * firstfit_previous = NULL;
+ /* Trying exact fit */
+ while ( current != NULL )
{
- /* second pass - first fit */
- chunk = free_mem.start;
- while ( 1 )
+ if ( current->size == size )
{
- prev_chunk = chunk;
- chunk = chunk-> next;
- if ( ( chunk == NULL ) || ( chunk->size > size ) )
+ /* Found exact fit, allocate node */
+ if ( previous != NULL )
{
- break;
+ /* Node in the middle of the list */
+ previous->next = current->next;
}
+ else
+ {
+ /* Node is first in list */
+ _PDCLIB_memlist.first = current->next;
+ }
+ if ( _PDCLIB_memlist.last == current )
+ {
+ /* Node is last in list */
+ _PDCLIB_memlist.last = previous;
+ }
+ return (char *)current + sizeof( struct _PDCLIB_memnode_t );
}
+ else if ( current->size > size && ( firstfit == NULL || current->size < firstfit->size ) )
+ {
+ /* Remember previous node in case we do not get an exact fit.
+ Note that this is the node *pointing to* the first fit,
+ as we need that for allocating (i.e., changing next pointer).
+ */
+ firstfit_previous = previous;
+ firstfit = current;
+ }
+ /* Skip to next node */
+ previous = current;
+ current = current->next;
}
- if ( chunk != NULL )
+ /* No exact fit; go for first fit */
+ if ( firstfit != NULL )
{
- /* remove chunk from free_mem list */
- if ( free_mem.start->next->next == NULL )
+ if ( ( firstfit->size - size ) > _PDCLIB_MINALLOC )
{
- /* free_mem list has only one entry */
- free_mem.last = free_mem.start;
+ /* Oversized - split into two nodes */
+ struct _PDCLIB_memnode_t * newnode = (struct _PDCLIB_memnode_t *)( (char *)firstfit + sizeof( struct _PDCLIB_memnode_t ) + size );
+ newnode->size = firstfit->size - size - sizeof( struct _PDCLIB_memnode_t );
+ newnode->next = firstfit->next;
+ firstfit->next = newnode;
+ firstfit->size = firstfit->size - newnode->size - sizeof( struct _PDCLIB_memnode_t );
}
- else if ( chunk == free_mem.last )
+ if ( firstfit_previous != NULL )
{
- /* chunk is last element of free_mem list */
- prev_chunk->next = NULL;
- free_mem.last = prev_chunk;
+ /* Node in the middle of the list */
+ firstfit_previous->next = firstfit->next;
}
else
{
- /* chunk is neither only nor last in free_mem list */
- prev_chunk->next = prev_chunk->next->next;
+ /* Node is first in list */
+ _PDCLIB_memlist.first = firstfit->next;
}
- /* append chunk to used_mem list */
- chunk->next = NULL;
- used_mem.last->next = chunk;
- used_mem.last = chunk;
- }
- /* append new chunk to end of used_mem list (if there's space) */
- if ( chunk == NULL )
- {
- if ( ( heap_used + size ) <= heap_max )
+ if ( _PDCLIB_memlist.last == firstfit )
{
- /* building the header */
- chunk = (chunk_t *) heap_start + heap_used + 1;
- chunk->size = size;
- chunk->next = NULL;
- chunk->address = chunk + sizeof( chunk_t );
- /* push heap_used past allocated area */
- heap_used += sizeof( chunk_t ) + size;
- used_mem.last->next = chunk;
- used_mem.last = chunk;
+ /* Node is last in list */
+ _PDCLIB_memlist.last = firstfit_previous;
}
- else
+ return (char *)firstfit + sizeof( struct _PDCLIB_memnode_t );
+ }
+ }
+ {
+ /* No fit possible; how many additional pages do we need? */
+ int pages = ( ( size + sizeof( struct _PDCLIB_memnode_t ) - 1 ) / _PDCLIB_PAGESIZE ) + 1;
+ /* Allocate more pages */
+ struct _PDCLIB_memnode_t * newnode = (struct _PDCLIB_memnode_t *)_PDCLIB_allocpages( pages );
+ if ( newnode != NULL )
+ {
+ newnode->next = NULL;
+ newnode->size = pages * _PDCLIB_PAGESIZE - sizeof( struct _PDCLIB_memnode_t );
+ if ( ( newnode->size - size ) > ( _PDCLIB_MINALLOC + sizeof( struct _PDCLIB_memnode_t ) ) )
{
- /* allocation would exceed max. heap size -
- /* demand more memory from kernel - not implemented */
- return 0;
+ /* Oversized - split into two nodes */
+ struct _PDCLIB_memnode_t * splitnode = (struct _PDCLIB_memnode_t *)( (char *)newnode + sizeof( struct _PDCLIB_memnode_t ) + size );
+ splitnode->size = newnode->size - size - sizeof( struct _PDCLIB_memnode_t );
+ newnode->size = size;
+ /* Add splitted node as last element to free node list */
+ if ( _PDCLIB_memlist.last == NULL )
+ {
+ _PDCLIB_memlist.first = splitnode;
+ splitnode->next = NULL;
+ }
+ else
+ {
+ _PDCLIB_memlist.last->next = splitnode;
+ }
+ _PDCLIB_memlist.last = splitnode;
}
+ return (char *)newnode + sizeof( struct _PDCLIB_memnode_t );
}
- return (void *) chunk->address;
+ }
+ /* No fit, heap extension not possible - out of memory */
+ return NULL;
}
+
+#endif
+
+#ifdef TEST
+#include <_PDCLIB_test.h>
+#include <string.h>
+
+#define MEMTEST( ptr, size ) ( ( ptr = malloc( size ) ) != NULL ) && ( memset( ptr, 0, size ) == ptr )
+#define PAGETEST( x ) ( pages_start + x * _PDCLIB_PAGESIZE ) == sbrk( 0 )
+#define EFFECTIVE _PDCLIB_PAGESIZE - sizeof( struct _PDCLIB_memnode_t )
+
+/* This can be enabled to give a dump of available nodes */
+#if 0
+#define NODETRACE( x ) do { struct _PDCLIB_memnode_t * tracer = _PDCLIB_memlist.first; printf( "Node trace #%d, %d allocated pages\n", x, ( (intptr_t)sbrk( 0 ) - (intptr_t)pages_start ) / _PDCLIB_PAGESIZE ); while ( tracer != NULL ) { printf( "- node %p, size %#x\n", (void *)tracer, tracer->size ); tracer = tracer->next; } } while ( 0 )
+#else
+#define NODETRACE( x ) ( (void) 0 )
+#endif
+
+/* Note that this test driver heavily tests *internals* of the implementation
+ above (and of free() and realloc(), too). That means that changes in the
+ implementation must be accompanied with appropriate changes of the test
+ driver. It does *not* make a good regression tester for the implementation,
+ I am afraid, and thus there is no REGTEST equivalent.
+*/
+
+void * sbrk( intptr_t );
+
+int main( void )
+{
+#ifndef REGTEST
+ void * ptr1, * ptr2, * ptr3, * ptr4, * ptr5, * ptr6, * ptr7, * ptr8, * ptr9;
+ char * pages_start = _PDCLIB_allocpages( 0 );
+ /* allocating 10 byte; expected: 1 page allocation, node split */
+ TESTCASE( MEMTEST( ptr1, 10 ) );
+ TESTCASE( PAGETEST( 1 ) );
+ NODETRACE( 1 );
+ /* allocating EFFECTIVE - 10 byte; expected: no page allocation, receiving split node */
+ TESTCASE( MEMTEST( ptr2, EFFECTIVE - 10 - sizeof( struct _PDCLIB_memnode_t ) ) );
+ TESTCASE( PAGETEST( 1 ) );
+ NODETRACE( 2 );
+ /* allocating EFFECTIVE; expected: 1 page allocation, no node split */
+ TESTCASE( MEMTEST( ptr3, EFFECTIVE ) );
+ TESTCASE( PAGETEST( 2 ) );
+ NODETRACE( 3 );
+ /* allocating EFFECTIVE - 4; expected: 1 page allocation, no node split */
+ TESTCASE( MEMTEST( ptr4, EFFECTIVE - 4 ) );
+ TESTCASE( PAGETEST( 3 ) );
+ NODETRACE( 4 );
+ /* freeing and re-allocating EFFECTIVE - 4; expected: no page allocation, no node split */
+ free( ptr4 );
+ TESTCASE( MEMTEST( ptr5, EFFECTIVE - 4 ) );
+ TESTCASE( ptr4 == ptr5 );
+ TESTCASE( PAGETEST( 3 ) );
+ NODETRACE( 5 );
+ /* releasing EFFECTIVE; expected: no page release */
+ free( ptr3 );
+ TESTCASE( PAGETEST( 3 ) );
+ NODETRACE( 6 );
+ /* allocating EFFECTIVE + _PDCLIB_PAGESIZE; expected: 2 page allocation, no node split */
+ TESTCASE( MEMTEST( ptr3, EFFECTIVE + _PDCLIB_PAGESIZE ) );
+ TESTCASE( PAGETEST( 5 ) );
+ NODETRACE( 7 );
+ /* reallocating to 10 byte; expected: no page allocation, no node split */
+ TESTCASE( realloc( ptr3, 10 ) == ptr3 );
+ TESTCASE( PAGETEST( 5 ) );
+ NODETRACE( 8 );
+ /* reallocating to EFFECTIVE + _PDCLIB_PAGESIZE; expected: no page allocation, no node split */
+ TESTCASE( realloc( ptr3, EFFECTIVE + _PDCLIB_PAGESIZE ) == ptr3 );
+ TESTCASE( PAGETEST( 5 ) );
+ NODETRACE( 9 );
+ /* reallocating to EFFECTIVE + _PDCLIB_PAGESIZE * 2; expected: 3 page allocations, no node split */
+ TESTCASE( realloc( ptr3, EFFECTIVE + _PDCLIB_PAGESIZE * 2 ) != ptr3 );
+ TESTCASE( PAGETEST( 8 ) );
+ NODETRACE( 10 );
+ /* allocating EFFECTIVE + _PDCLIB_PAGESIZE; expected: no page allocation, no node split */
+ TESTCASE( MEMTEST( ptr4, EFFECTIVE + _PDCLIB_PAGESIZE ) );
+ TESTCASE( PAGETEST( 8 ) );
+ NODETRACE( 11 );
+ /* allocating zero size; expected: no page allocation, no node split */
+ TESTCASE( ! MEMTEST( ptr6, 0 ) );
+ TESTCASE( PAGETEST( 8 ) );
+ NODETRACE( 12 );
+ /* allocating 4 byte; expected: no page allocation, upsizing of size, node split */
+ TESTCASE( MEMTEST( ptr7, 4 ) );
+ TESTCASE( PAGETEST( 8 ) );
+ NODETRACE( 13 );
+ /* allocating rest of page; expected: no page allocation, no node split */
+ TESTCASE( MEMTEST( ptr8, EFFECTIVE - _PDCLIB_MINALLOC - sizeof( struct _PDCLIB_memnode_t ) ) );
+ TESTCASE( PAGETEST( 8 ) );
+ NODETRACE( 14 );
+ /* freeing, and allocating one byte more; expected: 1 page allocation, no node split */
+ free( ptr8 );
+ NODETRACE( 15 );
+ TESTCASE( MEMTEST( ptr8, EFFECTIVE + 1 - _PDCLIB_MINALLOC - sizeof( struct _PDCLIB_memnode_t ) ) );
+ TESTCASE( PAGETEST( 9 ) );
+ NODETRACE( 16 );
+ /* realloc with NULL pointer; expected: no page allocation, no node split */
+ ptr9 = realloc( NULL, 4072 );
+ TESTCASE( ptr9 != NULL );
+ TESTCASE( memset( ptr9, 0, 4072 ) == ptr9 );
+ TESTCASE( PAGETEST( 9 ) );
+ NODETRACE( 17 );
+#else
+ puts( "No testing of malloc() - test driver does not know internals of system function." );
+#endif
+ return TEST_RESULTS;
+}
+
+#endif
projects / pdclib / blobdiff