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Combine the internal btree functions BtreePutData() and getPayload(). (CVS 3901)

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FossilOrigin-Name: a100a5304b0e7cbbdb6dac71a39c78eb71d44a03
This commit is contained in:
danielk1977
2007-05-02 17:48:45 +00:00
parent ae7e151a24
commit 9f8d64009e
3 changed files with 51 additions and 109 deletions
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144
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.366 2007/05/02 16:48:37 danielk1977 Exp $
** $Id: btree.c,v 1.367 2007/05/02 17:48:46 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
@@ -3139,20 +3139,28 @@ static int getOverflowPage(
/*
** Read payload information from the entry that the pCur cursor is
** pointing to. Begin reading the payload at "offset" and read
** a total of "amt" bytes. Put the result in zBuf.
** This function is used to read or overwrite payload information
** for the entry that the pCur cursor is pointing to. If the eOp
** parameter is 0, this is a read operation (data copied into
** buffer pBuf). If it is non-zero, a write (data copied from
** buffer pBuf).
**
** A total of "amt" bytes are read or written beginning at "offset".
** Data is read to or from the buffer pBuf.
**
** This routine does not make a distinction between key and data.
** It just reads bytes from the payload area. Data might appear
** on the main page or be scattered out on multiple overflow pages.
** It just reads or writes bytes from the payload area. Data might
** appear on the main page or be scattered out on multiple overflow
** pages.
*/
static int getPayload(
#define getPayload(a,b,c,d,e) accessPayload(a,b,c,d,e,0)
static int accessPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
int offset, /* Begin reading this far into payload */
int amt, /* Read this many bytes */
unsigned char *pBuf, /* Write the bytes into this buffer */
int skipKey /* offset begins at data if this is true */
int skipKey, /* offset begins at data if this is true */
int eOp /* zero to read. non-zero to write. */
){
unsigned char *aPayload;
Pgno nextPage;
@@ -3187,7 +3195,17 @@ static int getPayload(
if( a+offset>pCur->info.nLocal ){
a = pCur->info.nLocal - offset;
}
memcpy(pBuf, &aPayload[offset], a);
if( eOp ){
/* A write operation. */
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
memcpy(&aPayload[offset], pBuf, a);
}else{
/* A read operation */
memcpy(pBuf, &aPayload[offset], a);
}
if( a==amt ){
return SQLITE_OK;
}
@@ -3232,8 +3250,8 @@ static int getPayload(
}
#endif
}else{
/* Need to read this page properly, to obtain data to copy into
** the caller's buffer.
/* Need to read this page properly. It contains some of the
** range of data that is being read (eOp==0) or written (eOp!=0).
*/
DbPage *pDbPage;
int a = amt;
@@ -3246,7 +3264,18 @@ static int getPayload(
if( a + offset > ovflSize ){
a = ovflSize - offset;
}
memcpy(pBuf, &aPayload[offset+4], a);
if( eOp ){
/* A write operation. */
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc!=SQLITE_OK ){
sqlite3PagerUnref(pDbPage);
return rc;
}
memcpy(&aPayload[offset+4], pBuf, a);
}else{
/* A read operation */
memcpy(pBuf, &aPayload[offset+4], a);
}
offset = 0;
amt -= a;
pBuf += a;
@@ -6942,7 +6971,7 @@ int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, const void *z){
** (d) the cursor points at a valid row of an intKey table.
*/
if( pBt->inTransaction!=TRANS_WRITE ){
/* Must start a transaction before doing an insert */
/* Must start a transaction before writing to a blob */
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
assert( !pBt->readOnly );
@@ -6956,94 +6985,7 @@ int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, const void *z){
return SQLITE_ERROR;
}
/* Parse the cell-info. Check that the cell-data area is large
** enough for the proposed write operation.
*/
getCellInfo(pCsr);
pInfo = &pCsr->info;
if( pInfo->nData<(offset+amt) ){
return SQLITE_ERROR;
}
ovflSize = pBt->usableSize - 4;
assert(pCsr->cacheOverflow);
if( !pCsr->aOverflow ){
int nOverflow = (pInfo->nPayload - pInfo->nLocal + ovflSize - 1)/ovflSize;
pCsr->aOverflow = (Pgno *)sqliteMalloc(sizeof(Pgno)*nOverflow);
if( nOverflow && !pCsr->aOverflow ){
return SQLITE_NOMEM;
}
}
if( pInfo->nLocal>iOffset ){
/* In this case data must be written to the b-tree page. */
int iWrite = pInfo->nLocal - offset;
if( iWrite>iRem ){
iWrite = iRem;
}
rc = sqlite3PagerWrite(pCsr->pPage->pDbPage);
if( rc!=SQLITE_OK ){
return rc;
}
memcpy(&pInfo->pCell[iOffset+pInfo->nHeader], zRem, iWrite);
zRem += iWrite;
iRem -= iWrite;
}
iOffset = ((iOffset<pInfo->nLocal)?0:(iOffset-pInfo->nLocal));
assert(pInfo->iOverflow>0 || iRem==0);
if( iRem>0 ){
if( pCsr->aOverflow[iOffset/ovflSize] ){
iIdx = iOffset/ovflSize;
iOvfl = pCsr->aOverflow[iIdx];
iOffset = iOffset%ovflSize;
}else{
iOvfl = get4byte(&pInfo->pCell[pInfo->iOverflow]);
}
for(iIdx++; iRem>0; iIdx++){
if( iOffset>ovflSize ){
/* The only reason to read this page is to obtain the page
** number for the next page in the overflow chain. So try
** the getOverflowPage() shortcut. */
rc = getOverflowPage(pBt, iOvfl, 0, &iOvfl);
if( rc!=SQLITE_OK ){
return rc;
}
iOffset -= ovflSize;
pCsr->aOverflow[iIdx] = iOvfl;
}else{
int iWrite = ovflSize - iOffset;
DbPage *pOvfl; /* The overflow page. */
u8 *aData; /* Page data */
rc = sqlite3PagerGet(pBt->pPager, iOvfl, &pOvfl);
if( rc!=SQLITE_OK ){
return rc;
}
rc = sqlite3PagerWrite(pOvfl);
if( rc!=SQLITE_OK ){
sqlite3PagerUnref(pOvfl);
return rc;
}
aData = sqlite3PagerGetData(pOvfl);
iOvfl = get4byte(aData);
pCsr->aOverflow[iIdx] = iOvfl;
if( iWrite>iRem ){
iWrite = iRem;
}
memcpy(&aData[iOffset+4], zRem, iWrite);
sqlite3PagerUnref(pOvfl);
zRem += iWrite;
iRem -= iWrite;
iOffset = ((iOffset<ovflSize)?0:(iOffset-ovflSize));
}
}
}
return SQLITE_OK;
return accessPayload(pCsr, offset, amt, (unsigned char *)z, 0, 1);
}
/*