From: drh <drh@noemail.net>
Date: Tue, 1 Jun 2010 01:08:08 +0000 (+0000)
Subject: Comment edits and cleanup in wal.c.  No functional code changes.
X-Git-Tag: version-3.7.2~328^2~7
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=181e091ff38f3fa958b2df74aa3b369c19390fe4;p=thirdparty%2Fsqlite.git

Comment edits and cleanup in wal.c.  No functional code changes.

FossilOrigin-Name: e8e666ab8273f5db5265f0773b39820f75b6df1a
---

diff --git a/manifest b/manifest
index 16b6c1f177..4c44723b0d 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Attempt\sto\sget\sthe\sfilectrl.test\sscript\srunning.
-D 2010-06-01T00:28:43
+C Comment\sedits\sand\scleanup\sin\swal.c.\s\sNo\sfunctional\scode\schanges.
+D 2010-06-01T01:08:09
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in a5cad1f8f3e021356bfcc6c77dc16f6f1952bbc3
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -224,7 +224,7 @@ F src/vdbeblob.c 5327132a42a91e8b7acfb60b9d2c3b1c5c863e0e
 F src/vdbemem.c 2a82f455f6ca6f78b59fb312f96054c04ae0ead1
 F src/vdbetrace.c 864cef96919323482ebd9986f2132435115e9cc2
 F src/vtab.c a0f8a40274e4261696ef57aa806de2776ab72cda
-F src/wal.c b3f312fe54d298f965de98870af9eae0c5829310
+F src/wal.c d03eebb92e496ef6d4bd15d366bea2ee28e7fd8c
 F src/wal.h 1c1c9feb629b7f4afcbe0b47f80f47c5551d3a02
 F src/walker.c 3112bb3afe1d85dc52317cb1d752055e9a781f8f
 F src/where.c 75fee9e255b62f773fcadd1d1f25b6f63ac7a356
@@ -815,7 +815,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
-P bc707c83e5f9849d9d201d695d0d071ca9ed93cb
-R ae102866b2fd164e7001ff9fe230b9d8
+P e46a8f2b752f86c4d8942ee125210516026ffdc2
+R 09bc5e191ce3f59e21c41c3724d44527
 U drh
-Z ebdd27e86d236f32028490bc4dcd2173
+Z 50c2b0464eb7589c438f6f5d9973cb2c
diff --git a/manifest.uuid b/manifest.uuid
index 127181b163..5dc4c3e42a 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-e46a8f2b752f86c4d8942ee125210516026ffdc2
\ No newline at end of file
+e8e666ab8273f5db5265f0773b39820f75b6df1a
\ No newline at end of file
diff --git a/src/wal.c b/src/wal.c
index 99d884c463..0a67de59d5 100644
--- a/src/wal.c
+++ b/src/wal.c
@@ -595,7 +595,8 @@ static int walDecodeFrame(
 
 #if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
 /*
-** Names of locks.
+** Names of locks.  This routine is used to provide debugging output and is not
+** a part of an ordinary build.
 */
 static const char *walLockName(int lockIdx){
   if( lockIdx==WAL_WRITE_LOCK ){
@@ -615,7 +616,9 @@ static const char *walLockName(int lockIdx){
     
 
 /*
-** Set or release locks.
+** Set or release locks on the WAL.  Locks are either shared or exclusive.
+** A lock cannot be moved directly between shared and exclusive - it must go
+** through the unlocked state first.
 **
 ** In locking_mode=EXCLUSIVE, all of these routines become no-ops.
 */
@@ -674,10 +677,10 @@ static int walIndexEntry(u32 iFrame){
 }
 
 /*
-** Return the minimum mapping size in bytes that can be used to read the
-** wal-index up to and including frame iFrame. If iFrame is the last frame
-** in a block of 256 frames, the returned byte-count includes the space
-** required by the 256-byte index block.
+** Return the minimum size of the shared-memory, in bytes, that is needed
+** to support a wal-index containing frame iFrame.  The value returned
+** includes the wal-index header and the complete "block" containing iFrame,
+** including the hash table segment that follows the block.
 */
 static int walMappingSize(u32 iFrame){
   const int nByte = (sizeof(u32)*HASHTABLE_NPAGE + HASHTABLE_NBYTE) ;
@@ -743,7 +746,8 @@ static int walIndexRemap(Wal *pWal, int enlargeTo){
 
 /*
 ** Compute a hash on a page number.  The resulting hash value must land
-** between 0 and (HASHTABLE_NSLOT-1).
+** between 0 and (HASHTABLE_NSLOT-1).  The walHashNext() function advances
+** the hash to the next value in the event of a collision.
 */
 static int walHash(u32 iPage){
   assert( iPage>0 );
@@ -806,9 +810,10 @@ static void walHashFind(
 ** This function is called whenever pWal->hdr.mxFrame is decreased due
 ** to a rollback or savepoint.
 **
-** At most only the very last hash table needs to be updated.  Any
-** later hash tables will be automatically cleared when pWal->hdr.mxFrame
-** advances to the point where those hash tables are actually needed.
+** At most only the hash table containing pWal->hdr.mxFrame needs to be
+** updated.  Any later hash tables will be automatically cleared when
+** pWal->hdr.mxFrame advances to the point where those hash tables are
+** actually needed.
 */
 static void walCleanupHash(Wal *pWal){
   volatile HASHTABLE_DATATYPE *aHash;  /* Pointer to hash table to clear */
@@ -1089,14 +1094,12 @@ static void walIndexClose(Wal *pWal, int isDelete){
 }
 
 /* 
-** Open a connection to the log file associated with database zDb. The
-** database file does not actually have to exist. zDb is used only to
-** figure out the name of the log file to open. If the log file does not 
-** exist it is created by this call.
+** Open a connection to the WAL file associated with database zDbName.
+** The database file must already be opened on connection pDbFd.
 **
 ** A SHARED lock should be held on the database file when this function
 ** is called. The purpose of this SHARED lock is to prevent any other
-** client from unlinking the log or wal-index file. If another process
+** client from unlinking the WAL or wal-index file. If another process
 ** were to do this just after this client opened one of these files, the
 ** system would be badly broken.
 **