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Improve sessions module documentation and comments. Fix some other code issues.

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FossilOrigin-Name: bfc8bd80f8b225cebc66478448510ce84223ae7d
This commit is contained in:
dan
2014-09-27 12:26:18 +00:00
parent fa29ecc4ed
commit 16228167c2
4 changed files with 171 additions and 130 deletions
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48
ext/session/sqlite3session.c
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@ -49,10 +49,10 @@ struct SessionBuffer {
};
/*
** An object of this type is used internally as an abstraction for the
** input data read by changeset iterators. Input data may be supplied
** either as a single large buffer (sqlite3changeset_start()) or using
** a stream function (sqlite3changeset_start_str()).
** An object of this type is used internally as an abstraction for
** input data. Input data may be supplied either as a single large buffer
** (e.g. sqlite3changeset_start()) or using a stream function (e.g.
** sqlite3changeset_start_str()).
*/
struct SessionInput {
int iNext; /* Offset in aData[] of next change */
@ -2173,6 +2173,10 @@ static int sessionValueSetStr(
int nData, /* Size of buffer aData[] in bytes */
u8 enc /* String encoding (0 for blobs) */
){
/* In theory this code could just pass SQLITE_TRANSIENT as the final
** argument to sqlite3ValueSetStr() and have the copy created
** automatically. But doing so makes it difficult to detect any OOM
** error. Hence the code to create the copy externally. */
u8 *aCopy = sqlite3_malloc(nData);
if( aCopy==0 ) return SQLITE_NOMEM;
memcpy(aCopy, aData, nData);
@ -2299,12 +2303,16 @@ static int sessionChangesetBufferTblhdr(SessionInput *pIn, int *pnByte){
/*
** The input pointer currently points to the first byte of the first field
** of a record consisting of nCol columns. This function ensures the entire
** record is buffered.
** record is buffered. It does not move the input pointer.
**
** If successful, SQLITE_OK is returned and *pnByte is set to the size of
** the record in bytes. Otherwise, an SQLite error code is returned. The
** final value of *pnByte is undefined in this case.
*/
static int sessionChangesetBufferRecord(
SessionInput *pIn,
int nCol,
int *pnByte
SessionInput *pIn, /* Input data */
int nCol, /* Number of columns in record */
int *pnByte /* OUT: Size of record in bytes */
){
int rc = SQLITE_OK;
int nByte = 0;
@ -2335,6 +2343,15 @@ static int sessionChangesetBufferRecord(
** + number of columns in table (varint)
** + array of PK flags (1 byte per column),
** + table name (nul terminated).
**
** This function decodes the table-header and populates the p->nCol,
** p->zTab and p->abPK[] variables accordingly. The p->apValue[] array is
** also allocated or resized according to the new value of p->nCol. The
** input pointer is left pointing to the byte following the table header.
**
** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code
** is returned and the final values of the various fields enumerated above
** are undefined.
*/
static int sessionChangesetReadTblhdr(sqlite3_changeset_iter *p){
int rc;
@ -3775,7 +3792,7 @@ static int sessionChangeMerge(
** Add all changes in the changeset passed via the first two arguments to
** hash tables.
*/
static int sessionAddChangeset(
static int sessionChangesetToHash(
sqlite3_changeset_iter *pIter, /* Iterator to read from */
SessionTable **ppTabList /* IN/OUT: List of table objects */
){
@ -3794,15 +3811,6 @@ static int sessionAddChangeset(
SessionChange *pExist = 0;
SessionChange **pp;
#if 0
assert( bPatchset==0 || bPatchset==1 );
assert( pIter->bPatchset==0 || pIter->bPatchset==1 );
if( pIter->bPatchset!=bPatchset ){
rc = SQLITE_ERROR;
break;
}
#endif
sqlite3changeset_op(pIter, &zNew, &nCol, &op, &bIndirect);
if( !pTab || sqlite3_stricmp(zNew, pTab->zName) ){
/* Search the list for a matching table */
@ -3899,9 +3907,9 @@ int sessionChangesetConcat(
assert( xOutput==0 || (ppOut==0 && pnOut==0) );
rc = sessionAddChangeset(pLeft, &pList);
rc = sessionChangesetToHash(pLeft, &pList);
if( rc==SQLITE_OK ){
rc = sessionAddChangeset(pRight, &pList);
rc = sessionChangesetToHash(pRight, &pList);
}
bPatch = pLeft->bPatchset || pRight->bPatchset;