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Overview
Comment:Updated header comments in wal.c. No functional code changes.
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SHA1: 687632a6b3a0aeb006c1eda5c27d5489f08c230e
User & Date: drh 2010-05-25 15:53:32.000
Context
2010-05-26
15:06
Change the semantics of xShmGet() such that it will never increase the size of shared memory. xShmSize() must be used to grow the size of shared memory. A shared memory segment size cannot be shrunk (except by dropping it). (check-in: 72de007312 user: drh tags: trunk)
2010-05-25
15:53
Updated header comments in wal.c. No functional code changes. (check-in: 687632a6b3 user: drh tags: trunk)
15:23
Add a busy-handler to a test case in walthread.test to prevent errors. (check-in: d3d348aa97 user: dan tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/wal.c.
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**        exactly match the checksum computed consecutively on the
**        WAL header and the first 8 bytes and the content of all frames
**        up to and including the current frame.
**
** The checksum is computed using 32-bit big-endian integers if the
** magic number in the first 4 bytes of the WAL is 0x377f0683 and it
** is computed using little-endian if the magic number is 0x377f0682.









**
** On a checkpoint, the WAL is first VFS.xSync-ed, then valid content of the
** WAL is transferred into the database, then the database is VFS.xSync-ed.
** The VFS.xSync operations server as write barriers - all writes launched
** before the xSync must complete before any write that launches after the
** xSync begins.
**








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**        exactly match the checksum computed consecutively on the
**        WAL header and the first 8 bytes and the content of all frames
**        up to and including the current frame.
**
** The checksum is computed using 32-bit big-endian integers if the
** magic number in the first 4 bytes of the WAL is 0x377f0683 and it
** is computed using little-endian if the magic number is 0x377f0682.
** The checksum values are always stored in the frame header in a
** big-endian format regardless of which byte order is used to compute
** the checksum.  The checksum is computed by interpreting the input as
** an even number of unsigned 32-bit integers: x[0] through x[N].  The
** 
**   for i from 0 to n-1 step 2:
**     s0 += x[i] + s1;
**     s1 += x[i+1] + s0;
**   endfor
**
** On a checkpoint, the WAL is first VFS.xSync-ed, then valid content of the
** WAL is transferred into the database, then the database is VFS.xSync-ed.
** The VFS.xSync operations server as write barriers - all writes launched
** before the xSync must complete before any write that launches after the
** xSync begins.
**
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