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Comment:Updated comments on journal.c. No changes to code. (CVS 4408)
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SHA1: 3298441086330d1d24c30b7c061dfec98e9ea3ac
User & Date: drh 2007-09-06 13:49:37.000
Context
2007-09-06
22:19
Allocate page cache headers and page cache data buffers separately. The data buffer will be a power of two in size and this gives some malloc implementation additional optimization opportunitites. (CVS 4409) (check-in: 2b755defe5 user: drh tags: trunk)
13:49
Updated comments on journal.c. No changes to code. (CVS 4408) (check-in: 3298441086 user: drh tags: trunk)
07:47
Add some extra comments to the header in test_async.c. (CVS 4407) (check-in: 79cf4e886c user: danielk1977 tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/journal.c. 
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/*
** 2007 August 22
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** @(#) $Id: journal.c,v 1.6 2007/09/03 15:19:35 drh Exp $
*/

#ifdef SQLITE_ENABLE_ATOMIC_WRITE

/*
** This file implements a special kind of sqlite3_file object used
** by SQLite to create journal files if the atomic-write optimization













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/*
** 2007 August 22
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** @(#) $Id: journal.c,v 1.7 2007/09/06 13:49:37 drh Exp $
*/

#ifdef SQLITE_ENABLE_ATOMIC_WRITE

/*
** This file implements a special kind of sqlite3_file object used
** by SQLite to create journal files if the atomic-write optimization
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**   1) The in-memory representation grows too large for the allocated 
**      buffer, or
**   2) The xSync() method is called.
*/

#include "sqliteInt.h"






struct JournalFile {
  sqlite3_io_methods *pMethod;

  int nBuf;
  char *zBuf;
  int iSize;

  int flags;
  sqlite3_vfs *pVfs;
  sqlite3_file *pReal;
  const char *zJournal;
};
typedef struct JournalFile JournalFile;

/*
** If it does not already exists, create and populate the on-disk file 
** for JournalFile p.
*/








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**   1) The in-memory representation grows too large for the allocated 
**      buffer, or
**   2) The xSync() method is called.
*/

#include "sqliteInt.h"


/*
** A JournalFile object is a subclass of sqlite3_file used by
** as an open file handle for journal files.
*/
struct JournalFile {
  sqlite3_io_methods *pMethod;    /* I/O methods on journal files */

  int nBuf;                       /* Size of zBuf[] in bytes */
  char *zBuf;                     /* Space to buffer journal writes */
  int iSize;                      /* Amount of zBuf[] currently used */

  int flags;                      /* xOpen flags */
  sqlite3_vfs *pVfs;              /* The "real" underlying VFS */
  sqlite3_file *pReal;            /* The "real" underlying file descriptor */
  const char *zJournal;           /* Name of the journal file */
};
typedef struct JournalFile JournalFile;

/*
** If it does not already exists, create and populate the on-disk file 
** for JournalFile p.
*/
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  return SQLITE_OK;
}

/*
** Read data from the file.
*/
static int jrnlRead(
  sqlite3_file *pJfd, 
  void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  int rc = SQLITE_OK;
  JournalFile *p = (JournalFile *)pJfd;
  if( p->pReal ){
    rc = sqlite3OsRead(p->pReal, zBuf, iAmt, iOfst);
  }else{
    assert( iAmt+iOfst<=p->iSize );
    memcpy(zBuf, &p->zBuf[iOfst], iAmt);
  }
  return rc;
}

/*
** Write data to the file.
*/
static int jrnlWrite(
  sqlite3_file *pJfd, 
  const void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  int rc = SQLITE_OK;
  JournalFile *p = (JournalFile *)pJfd;
  if( !p->pReal && (iOfst+iAmt)>p->nBuf ){
    rc = createFile(p);
  }
  if( rc==SQLITE_OK ){








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  return SQLITE_OK;
}

/*
** Read data from the file.
*/
static int jrnlRead(
  sqlite3_file *pJfd,    /* The journal file from which to read */
  void *zBuf,            /* Put the results here */
  int iAmt,              /* Number of bytes to read */
  sqlite_int64 iOfst     /* Begin reading at this offset */
){
  int rc = SQLITE_OK;
  JournalFile *p = (JournalFile *)pJfd;
  if( p->pReal ){
    rc = sqlite3OsRead(p->pReal, zBuf, iAmt, iOfst);
  }else{
    assert( iAmt+iOfst<=p->iSize );
    memcpy(zBuf, &p->zBuf[iOfst], iAmt);
  }
  return rc;
}

/*
** Write data to the file.
*/
static int jrnlWrite(
  sqlite3_file *pJfd,    /* The journal file into which to write */
  const void *zBuf,      /* Take data to be written from here */
  int iAmt,              /* Number of bytes to write */
  sqlite_int64 iOfst     /* Begin writing at this offset into the file */
){
  int rc = SQLITE_OK;
  JournalFile *p = (JournalFile *)pJfd;
  if( !p->pReal && (iOfst+iAmt)>p->nBuf ){
    rc = createFile(p);
  }
  if( rc==SQLITE_OK ){
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  0              /* xDeviceCharacteristics */
};

/* 
** Open a journal file.
*/
int sqlite3JournalOpen(
  sqlite3_vfs *pVfs, 
  const char *zName, 
  sqlite3_file *pJfd,
  int flags,
  int nBuf
){
  JournalFile *p = (JournalFile *)pJfd;
  memset(p, 0, sqlite3JournalSize(pVfs));
  if( nBuf>0 ){
    p->zBuf = sqlite3MallocZero(nBuf);
    if( !p->zBuf ){
      return SQLITE_NOMEM;








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  0              /* xDeviceCharacteristics */
};

/* 
** Open a journal file.
*/
int sqlite3JournalOpen(
  sqlite3_vfs *pVfs,         /* The VFS to use for actual file I/O */
  const char *zName,         /* Name of the journal file */
  sqlite3_file *pJfd,        /* Preallocated, blank file handle */
  int flags,                 /* Opening flags */
  int nBuf                   /* Bytes buffered before opening the file */
){
  JournalFile *p = (JournalFile *)pJfd;
  memset(p, 0, sqlite3JournalSize(pVfs));
  if( nBuf>0 ){
    p->zBuf = sqlite3MallocZero(nBuf);
    if( !p->zBuf ){
      return SQLITE_NOMEM;
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