Introduce new btree2u with traditional buffer pool manager.

diff --git a/README.md b/README.md
index 856ec018df7075e2adc903e2b09a164572910580..d24a063ed99e0431073545feb012d99df9893434 100644 (file)
--- a/README.md
+++ b/README.md
@@ -3,12 +3,14 @@ Btree-source-code
 
 A working project for High-concurrency B-tree source code in C
 
-There are five major code sets in the standard btree source code:
+There are six files in the btree source code:
 
 btree2s.c       Single Threaded/MultiProcess version that removes keys all the way back to an original empty btree, placing removed nodes on a free list.  Operates under either memory mapping or file I/O.  Recommended btrees hosted on network file systems.
 
 btree2t.c       Single Threaded/MultiProcess version similar to btree2s except that fcntl locking has been replaced by test & set latches in the first few btree pages.  Uses either memory mapping or file I/O.
 
+btree2u.c              Single Threaded/MultiProcess version that implements a traditional buffer pool manager in the first n pages of the btree file.  The buffer pool accesses its pages with mmap.  Evicted pages are written back to the btree file from the buffer pool pages with pwrite.
+
 threads2h.c     Multi-Threaded/Multi-Process with latching implemented by a latch manager with pthreads/SRW latches in the first few btree pages. Recommended for Windows.
 
 threads2i.c     Multi-Threaded/Multi-Process with latching implemented by a latch manager with test & set latches in the first few btree pages with thread yield system calls during contention.