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sqlite/ext/recover/dbdata.c
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/*
** 2019-04-17
**
** 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.
**
******************************************************************************
**
** This file contains an implementation of two eponymous virtual tables,
** "sqlite_dbdata" and "sqlite_dbptr". Both modules require that the
** "sqlite_dbpage" eponymous virtual table be available.
**
** SQLITE_DBDATA:
** sqlite_dbdata is used to extract data directly from a database b-tree
** page and its associated overflow pages, bypassing the b-tree layer.
** The table schema is equivalent to:
**
** CREATE TABLE sqlite_dbdata(
** pgno INTEGER,
** cell INTEGER,
** field INTEGER,
** value ANY,
** schema TEXT HIDDEN
** );
**
** IMPORTANT: THE VIRTUAL TABLE SCHEMA ABOVE IS SUBJECT TO CHANGE. IN THE
** FUTURE NEW NON-HIDDEN COLUMNS MAY BE ADDED BETWEEN "value" AND
** "schema".
**
** Each page of the database is inspected. If it cannot be interpreted as
** a b-tree page, or if it is a b-tree page containing 0 entries, the
** sqlite_dbdata table contains no rows for that page. Otherwise, the
** table contains one row for each field in the record associated with
** each cell on the page. For intkey b-trees, the key value is stored in
** field -1.
**
** For example, for the database:
**
** CREATE TABLE t1(a, b); -- root page is page 2
** INSERT INTO t1(rowid, a, b) VALUES(5, 'v', 'five');
** INSERT INTO t1(rowid, a, b) VALUES(10, 'x', 'ten');
**
** the sqlite_dbdata table contains, as well as from entries related to
** page 1, content equivalent to:
**
** INSERT INTO sqlite_dbdata(pgno, cell, field, value) VALUES
** (2, 0, -1, 5 ),
** (2, 0, 0, 'v' ),
** (2, 0, 1, 'five'),
** (2, 1, -1, 10 ),
** (2, 1, 0, 'x' ),
** (2, 1, 1, 'ten' );
**
** If database corruption is encountered, this module does not report an
** error. Instead, it attempts to extract as much data as possible and
** ignores the corruption.
**
** SQLITE_DBPTR:
** The sqlite_dbptr table has the following schema:
**
** CREATE TABLE sqlite_dbptr(
** pgno INTEGER,
** child INTEGER,
** schema TEXT HIDDEN
** );
**
** It contains one entry for each b-tree pointer between a parent and
** child page in the database.
*/
#if !defined(SQLITEINT_H)
#include "sqlite3.h"
typedef unsigned char u8;
typedef unsigned int u32;
#endif
#include <string.h>
#include <assert.h>
#ifndef SQLITE_OMIT_VIRTUALTABLE
#define DBDATA_PADDING_BYTES 100
typedef struct DbdataTable DbdataTable;
typedef struct DbdataCursor DbdataCursor;
typedef struct DbdataBuffer DbdataBuffer;
/*
** Buffer type.
*/
struct DbdataBuffer {
u8 *aBuf;
sqlite3_int64 nBuf;
};
/* Cursor object */
struct DbdataCursor {
sqlite3_vtab_cursor base; /* Base class. Must be first */
sqlite3_stmt *pStmt; /* For fetching database pages */
int iPgno; /* Current page number */
u8 *aPage; /* Buffer containing page */
int nPage; /* Size of aPage[] in bytes */
int nCell; /* Number of cells on aPage[] */
int iCell; /* Current cell number */
int bOnePage; /* True to stop after one page */
int szDb;
sqlite3_int64 iRowid;
/* Only for the sqlite_dbdata table */
DbdataBuffer rec;
sqlite3_int64 nRec; /* Size of pRec[] in bytes */
sqlite3_int64 nHdr; /* Size of header in bytes */
int iField; /* Current field number */
u8 *pHdrPtr;
u8 *pPtr;
u32 enc; /* Text encoding */
sqlite3_int64 iIntkey; /* Integer key value */
};
/* Table object */
struct DbdataTable {
sqlite3_vtab base; /* Base class. Must be first */
sqlite3 *db; /* The database connection */
sqlite3_stmt *pStmt; /* For fetching database pages */
int bPtr; /* True for sqlite3_dbptr table */
};
/* Column and schema definitions for sqlite_dbdata */
#define DBDATA_COLUMN_PGNO 0
#define DBDATA_COLUMN_CELL 1
#define DBDATA_COLUMN_FIELD 2
#define DBDATA_COLUMN_VALUE 3
#define DBDATA_COLUMN_SCHEMA 4
#define DBDATA_SCHEMA \
"CREATE TABLE x(" \
" pgno INTEGER," \
" cell INTEGER," \
" field INTEGER," \
" value ANY," \
" schema TEXT HIDDEN" \
")"
/* Column and schema definitions for sqlite_dbptr */
#define DBPTR_COLUMN_PGNO 0
#define DBPTR_COLUMN_CHILD 1
#define DBPTR_COLUMN_SCHEMA 2
#define DBPTR_SCHEMA \
"CREATE TABLE x(" \
" pgno INTEGER," \
" child INTEGER," \
" schema TEXT HIDDEN" \
")"
/*
** Ensure the buffer passed as the first argument is at least nMin bytes
** in size. If an error occurs while attempting to resize the buffer,
** SQLITE_NOMEM is returned. Otherwise, SQLITE_OK.
*/
static int dbdataBufferSize(DbdataBuffer *pBuf, sqlite3_int64 nMin){
if( nMin>pBuf->nBuf ){
sqlite3_int64 nNew = nMin+16384;
u8 *aNew = (u8*)sqlite3_realloc64(pBuf->aBuf, nNew);
if( aNew==0 ) return SQLITE_NOMEM;
pBuf->aBuf = aNew;
pBuf->nBuf = nNew;
}
return SQLITE_OK;
}
/*
** Release the allocation managed by buffer pBuf.
*/
static void dbdataBufferFree(DbdataBuffer *pBuf){
sqlite3_free(pBuf->aBuf);
memset(pBuf, 0, sizeof(*pBuf));
}
/*
** Connect to an sqlite_dbdata (pAux==0) or sqlite_dbptr (pAux!=0) virtual
** table.
*/
static int dbdataConnect(
sqlite3 *db,
void *pAux,
int argc, const char *const*argv,
sqlite3_vtab **ppVtab,
char **pzErr
){
DbdataTable *pTab = 0;
int rc = sqlite3_declare_vtab(db, pAux ? DBPTR_SCHEMA : DBDATA_SCHEMA);
(void)argc;
(void)argv;
(void)pzErr;
sqlite3_vtab_config(db, SQLITE_VTAB_USES_ALL_SCHEMAS);
if( rc==SQLITE_OK ){
pTab = (DbdataTable*)sqlite3_malloc64(sizeof(DbdataTable));
if( pTab==0 ){
rc = SQLITE_NOMEM;
}else{
memset(pTab, 0, sizeof(DbdataTable));
pTab->db = db;
pTab->bPtr = (pAux!=0);
}
}
*ppVtab = (sqlite3_vtab*)pTab;
return rc;
}
/*
** Disconnect from or destroy a sqlite_dbdata or sqlite_dbptr virtual table.
*/
static int dbdataDisconnect(sqlite3_vtab *pVtab){
DbdataTable *pTab = (DbdataTable*)pVtab;
if( pTab ){
sqlite3_finalize(pTab->pStmt);
sqlite3_free(pVtab);
}
return SQLITE_OK;
}
/*
** This function interprets two types of constraints:
**
** schema=?
** pgno=?
**
** If neither are present, idxNum is set to 0. If schema=? is present,
** the 0x01 bit in idxNum is set. If pgno=? is present, the 0x02 bit
** in idxNum is set.
**
** If both parameters are present, schema is in position 0 and pgno in
** position 1.
*/
static int dbdataBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdx){
DbdataTable *pTab = (DbdataTable*)tab;
int i;
int iSchema = -1;
int iPgno = -1;
int colSchema = (pTab->bPtr ? DBPTR_COLUMN_SCHEMA : DBDATA_COLUMN_SCHEMA);
for(i=0; i<pIdx->nConstraint; i++){
struct sqlite3_index_constraint *p = &pIdx->aConstraint[i];
if( p->op==SQLITE_INDEX_CONSTRAINT_EQ ){
if( p->iColumn==colSchema ){
if( p->usable==0 ) return SQLITE_CONSTRAINT;
iSchema = i;
}
if( p->iColumn==DBDATA_COLUMN_PGNO && p->usable ){
iPgno = i;
}
}
}
if( iSchema>=0 ){
pIdx->aConstraintUsage[iSchema].argvIndex = 1;
pIdx->aConstraintUsage[iSchema].omit = 1;
}
if( iPgno>=0 ){
pIdx->aConstraintUsage[iPgno].argvIndex = 1 + (iSchema>=0);
pIdx->aConstraintUsage[iPgno].omit = 1;
pIdx->estimatedCost = 100;
pIdx->estimatedRows = 50;
if( pTab->bPtr==0 && pIdx->nOrderBy && pIdx->aOrderBy[0].desc==0 ){
int iCol = pIdx->aOrderBy[0].iColumn;
if( pIdx->nOrderBy==1 ){
pIdx->orderByConsumed = (iCol==0 || iCol==1);
}else if( pIdx->nOrderBy==2 && pIdx->aOrderBy[1].desc==0 && iCol==0 ){
pIdx->orderByConsumed = (pIdx->aOrderBy[1].iColumn==1);
}
}
}else{
pIdx->estimatedCost = 100000000;
pIdx->estimatedRows = 1000000000;
}
pIdx->idxNum = (iSchema>=0 ? 0x01 : 0x00) | (iPgno>=0 ? 0x02 : 0x00);
return SQLITE_OK;
}
/*
** Open a new sqlite_dbdata or sqlite_dbptr cursor.
*/
static int dbdataOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
DbdataCursor *pCsr;
pCsr = (DbdataCursor*)sqlite3_malloc64(sizeof(DbdataCursor));
if( pCsr==0 ){
return SQLITE_NOMEM;
}else{
memset(pCsr, 0, sizeof(DbdataCursor));
pCsr->base.pVtab = pVTab;
}
*ppCursor = (sqlite3_vtab_cursor *)pCsr;
return SQLITE_OK;
}
/*
** Restore a cursor object to the state it was in when first allocated
** by dbdataOpen().
*/
static void dbdataResetCursor(DbdataCursor *pCsr){
DbdataTable *pTab = (DbdataTable*)(pCsr->base.pVtab);
if( pTab->pStmt==0 ){
pTab->pStmt = pCsr->pStmt;
}else{
sqlite3_finalize(pCsr->pStmt);
}
pCsr->pStmt = 0;
pCsr->iPgno = 1;
pCsr->iCell = 0;
pCsr->iField = 0;
pCsr->bOnePage = 0;
sqlite3_free(pCsr->aPage);
dbdataBufferFree(&pCsr->rec);
pCsr->aPage = 0;
pCsr->nRec = 0;
}
/*
** Close an sqlite_dbdata or sqlite_dbptr cursor.
*/
static int dbdataClose(sqlite3_vtab_cursor *pCursor){
DbdataCursor *pCsr = (DbdataCursor*)pCursor;
dbdataResetCursor(pCsr);
sqlite3_free(pCsr);
return SQLITE_OK;
}
/*
** Utility methods to decode 16 and 32-bit big-endian unsigned integers.
*/
static u32 get_uint16(unsigned char *a){
return (a[0]<<8)|a[1];
}
static u32 get_uint32(unsigned char *a){
return ((u32)a[0]<<24)
| ((u32)a[1]<<16)
| ((u32)a[2]<<8)
| ((u32)a[3]);
}
/*
** Load page pgno from the database via the sqlite_dbpage virtual table.
** If successful, set (*ppPage) to point to a buffer containing the page
** data, (*pnPage) to the size of that buffer in bytes and return
** SQLITE_OK. In this case it is the responsibility of the caller to
** eventually free the buffer using sqlite3_free().
**
** Or, if an error occurs, set both (*ppPage) and (*pnPage) to 0 and
** return an SQLite error code.
*/
static int dbdataLoadPage(
DbdataCursor *pCsr, /* Cursor object */
u32 pgno, /* Page number of page to load */
u8 **ppPage, /* OUT: pointer to page buffer */
int *pnPage /* OUT: Size of (*ppPage) in bytes */
){
int rc2;
int rc = SQLITE_OK;
sqlite3_stmt *pStmt = pCsr->pStmt;
*ppPage = 0;
*pnPage = 0;
if( pgno>0 ){
sqlite3_bind_int64(pStmt, 2, pgno);
if( SQLITE_ROW==sqlite3_step(pStmt) ){
int nCopy = sqlite3_column_bytes(pStmt, 0);
if( nCopy>0 ){
u8 *pPage;
pPage = (u8*)sqlite3_malloc64(nCopy + DBDATA_PADDING_BYTES);
if( pPage==0 ){
rc = SQLITE_NOMEM;
}else{
const u8 *pCopy = sqlite3_column_blob(pStmt, 0);
memcpy(pPage, pCopy, nCopy);
memset(&pPage[nCopy], 0, DBDATA_PADDING_BYTES);
}
*ppPage = pPage;
*pnPage = nCopy;
}
}
rc2 = sqlite3_reset(pStmt);
if( rc==SQLITE_OK ) rc = rc2;
}
return rc;
}
/*
** Read a varint. Put the value in *pVal and return the number of bytes.
*/
static int dbdataGetVarint(const u8 *z, sqlite3_int64 *pVal){
sqlite3_uint64 u = 0;
int i;
for(i=0; i<8; i++){
u = (u<<7) + (z[i]&0x7f);
if( (z[i]&0x80)==0 ){ *pVal = (sqlite3_int64)u; return i+1; }
}
u = (u<<8) + (z[i]&0xff);
*pVal = (sqlite3_int64)u;
return 9;
}
/*
** Like dbdataGetVarint(), but set the output to 0 if it is less than 0
** or greater than 0xFFFFFFFF. This can be used for all varints in an
** SQLite database except for key values in intkey tables.
*/
static int dbdataGetVarintU32(const u8 *z, sqlite3_int64 *pVal){
sqlite3_int64 val;
int nRet = dbdataGetVarint(z, &val);
if( val<0 || val>0xFFFFFFFF ) val = 0;
*pVal = val;
return nRet;
}
/*
** Return the number of bytes of space used by an SQLite value of type
** eType.
*/
static int dbdataValueBytes(int eType){
switch( eType ){
case 0: case 8: case 9:
case 10: case 11:
return 0;
case 1:
return 1;
case 2:
return 2;
case 3:
return 3;
case 4:
return 4;
case 5:
return 6;
case 6:
case 7:
return 8;
default:
if( eType>0 ){
return ((eType-12) / 2);
}
return 0;
}
}
/*
** Load a value of type eType from buffer pData and use it to set the
** result of context object pCtx.
*/
static void dbdataValue(
sqlite3_context *pCtx,
u32 enc,
int eType,
u8 *pData,
sqlite3_int64 nData
){
if( eType>=0 ){
if( dbdataValueBytes(eType)<=nData ){
switch( eType ){
case 0:
case 10:
case 11:
sqlite3_result_null(pCtx);
break;
case 8:
sqlite3_result_int(pCtx, 0);
break;
case 9:
sqlite3_result_int(pCtx, 1);
break;
case 1: case 2: case 3: case 4: case 5: case 6: case 7: {
sqlite3_uint64 v = (signed char)pData[0];
pData++;
switch( eType ){
case 7:
case 6: v = (v<<16) + (pData[0]<<8) + pData[1]; pData += 2;
case 5: v = (v<<16) + (pData[0]<<8) + pData[1]; pData += 2;
case 4: v = (v<<8) + pData[0]; pData++;
case 3: v = (v<<8) + pData[0]; pData++;
case 2: v = (v<<8) + pData[0]; pData++;
}
if( eType==7 ){
double r;
memcpy(&r, &v, sizeof(r));
sqlite3_result_double(pCtx, r);
}else{
sqlite3_result_int64(pCtx, (sqlite3_int64)v);
}
break;
}
default: {
int n = ((eType-12) / 2);
if( eType % 2 ){
switch( enc ){
#ifndef SQLITE_OMIT_UTF16
case SQLITE_UTF16BE:
sqlite3_result_text16be(pCtx, (void*)pData, n, SQLITE_TRANSIENT);
break;
case SQLITE_UTF16LE:
sqlite3_result_text16le(pCtx, (void*)pData, n, SQLITE_TRANSIENT);
break;
#endif
default:
sqlite3_result_text(pCtx, (char*)pData, n, SQLITE_TRANSIENT);
break;
}
}else{
sqlite3_result_blob(pCtx, pData, n, SQLITE_TRANSIENT);
}
}
}
}else{
if( eType==7 ){
sqlite3_result_double(pCtx, 0.0);
}else if( eType<7 ){
sqlite3_result_int(pCtx, 0);
}else if( eType%2 ){
sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
}else{
sqlite3_result_blob(pCtx, "", 0, SQLITE_STATIC);
}
}
}
}
/* This macro is a copy of the MX_CELL() macro in the SQLite core. Given
** a page-size, it returns the maximum number of cells that may be present
** on the page. */
#define DBDATA_MX_CELL(pgsz) ((pgsz-8)/6)
/* Maximum number of fields that may appear in a single record. This is
** the "hard-limit", according to comments in sqliteLimit.h. */
#define DBDATA_MX_FIELD 32676
/*
** Move an sqlite_dbdata or sqlite_dbptr cursor to the next entry.
*/
static int dbdataNext(sqlite3_vtab_cursor *pCursor){
DbdataCursor *pCsr = (DbdataCursor*)pCursor;
DbdataTable *pTab = (DbdataTable*)pCursor->pVtab;
pCsr->iRowid++;
while( 1 ){
int rc;
int iOff = (pCsr->iPgno==1 ? 100 : 0);
int bNextPage = 0;
if( pCsr->aPage==0 ){
while( 1 ){
if( pCsr->bOnePage==0 && pCsr->iPgno>pCsr->szDb ) return SQLITE_OK;
rc = dbdataLoadPage(pCsr, pCsr->iPgno, &pCsr->aPage, &pCsr->nPage);
if( rc!=SQLITE_OK ) return rc;
if( pCsr->aPage && pCsr->nPage>=256 ) break;
sqlite3_free(pCsr->aPage);
pCsr->aPage = 0;
if( pCsr->bOnePage ) return SQLITE_OK;
pCsr->iPgno++;
}
assert( iOff+3+2<=pCsr->nPage );
pCsr->iCell = pTab->bPtr ? -2 : 0;
pCsr->nCell = get_uint16(&pCsr->aPage[iOff+3]);
if( pCsr->nCell>DBDATA_MX_CELL(pCsr->nPage) ){
pCsr->nCell = DBDATA_MX_CELL(pCsr->nPage);
}
}
if( pTab->bPtr ){
if( pCsr->aPage[iOff]!=0x02 && pCsr->aPage[iOff]!=0x05 ){
pCsr->iCell = pCsr->nCell;
}
pCsr->iCell++;
if( pCsr->iCell>=pCsr->nCell ){
sqlite3_free(pCsr->aPage);
pCsr->aPage = 0;
if( pCsr->bOnePage ) return SQLITE_OK;
pCsr->iPgno++;
}else{
return SQLITE_OK;
}
}else{
/* If there is no record loaded, load it now. */
assert( pCsr->rec.aBuf!=0 || pCsr->nRec==0 );
if( pCsr->nRec==0 ){
int bHasRowid = 0;
int nPointer = 0;
sqlite3_int64 nPayload = 0;
sqlite3_int64 nHdr = 0;
int iHdr;
int U, X;
int nLocal;
switch( pCsr->aPage[iOff] ){
case 0x02:
nPointer = 4;
break;
case 0x0a:
break;
case 0x0d:
bHasRowid = 1;
break;
default:
/* This is not a b-tree page with records on it. Continue. */
pCsr->iCell = pCsr->nCell;
break;
}
if( pCsr->iCell>=pCsr->nCell ){
bNextPage = 1;
}else{
int iCellPtr = iOff + 8 + nPointer + pCsr->iCell*2;
if( iCellPtr>pCsr->nPage ){
bNextPage = 1;
}else{
iOff = get_uint16(&pCsr->aPage[iCellPtr]);
}
/* For an interior node cell, skip past the child-page number */
iOff += nPointer;
/* Load the "byte of payload including overflow" field */
if( bNextPage || iOff>pCsr->nPage || iOff<=iCellPtr ){
bNextPage = 1;
}else{
iOff += dbdataGetVarintU32(&pCsr->aPage[iOff], &nPayload);
if( nPayload>0x7fffff00 ) nPayload &= 0x3fff;
if( nPayload==0 ) nPayload = 1;
}
/* If this is a leaf intkey cell, load the rowid */
if( bHasRowid && !bNextPage && iOff<pCsr->nPage ){
iOff += dbdataGetVarint(&pCsr->aPage[iOff], &pCsr->iIntkey);
}
/* Figure out how much data to read from the local page */
U = pCsr->nPage;
if( bHasRowid ){
X = U-35;
}else{
X = ((U-12)*64/255)-23;
}
if( nPayload<=X ){
nLocal = nPayload;
}else{
int M, K;
M = ((U-12)*32/255)-23;
K = M+((nPayload-M)%(U-4));
if( K<=X ){
nLocal = K;
}else{
nLocal = M;
}
}
if( bNextPage || nLocal+iOff>pCsr->nPage ){
bNextPage = 1;
}else{
/* Allocate space for payload. And a bit more to catch small buffer
** overruns caused by attempting to read a varint or similar from
** near the end of a corrupt record. */
rc = dbdataBufferSize(&pCsr->rec, nPayload+DBDATA_PADDING_BYTES);
if( rc!=SQLITE_OK ) return rc;
assert( pCsr->rec.aBuf!=0 );
assert( nPayload!=0 );
/* Load the nLocal bytes of payload */
memcpy(pCsr->rec.aBuf, &pCsr->aPage[iOff], nLocal);
iOff += nLocal;
/* Load content from overflow pages */
if( nPayload>nLocal ){
sqlite3_int64 nRem = nPayload - nLocal;
u32 pgnoOvfl = get_uint32(&pCsr->aPage[iOff]);
while( nRem>0 ){
u8 *aOvfl = 0;
int nOvfl = 0;
int nCopy;
rc = dbdataLoadPage(pCsr, pgnoOvfl, &aOvfl, &nOvfl);
assert( rc!=SQLITE_OK || aOvfl==0 || nOvfl==pCsr->nPage );
if( rc!=SQLITE_OK ) return rc;
if( aOvfl==0 ) break;
nCopy = U-4;
if( nCopy>nRem ) nCopy = nRem;
memcpy(&pCsr->rec.aBuf[nPayload-nRem], &aOvfl[4], nCopy);
nRem -= nCopy;
pgnoOvfl = get_uint32(aOvfl);
sqlite3_free(aOvfl);
}
nPayload -= nRem;
}
memset(&pCsr->rec.aBuf[nPayload], 0, DBDATA_PADDING_BYTES);
pCsr->nRec = nPayload;
iHdr = dbdataGetVarintU32(pCsr->rec.aBuf, &nHdr);
if( nHdr>nPayload ) nHdr = 0;
pCsr->nHdr = nHdr;
pCsr->pHdrPtr = &pCsr->rec.aBuf[iHdr];
pCsr->pPtr = &pCsr->rec.aBuf[pCsr->nHdr];
pCsr->iField = (bHasRowid ? -1 : 0);
}
}
}else{
pCsr->iField++;
if( pCsr->iField>0 ){
sqlite3_int64 iType;
if( pCsr->pHdrPtr>=&pCsr->rec.aBuf[pCsr->nRec]
|| pCsr->iField>=DBDATA_MX_FIELD
){
bNextPage = 1;
}else{
int szField = 0;
pCsr->pHdrPtr += dbdataGetVarintU32(pCsr->pHdrPtr, &iType);
szField = dbdataValueBytes(iType);
if( (pCsr->nRec - (pCsr->pPtr - pCsr->rec.aBuf))<szField ){
pCsr->pPtr = &pCsr->rec.aBuf[pCsr->nRec];
}else{
pCsr->pPtr += szField;
}
}
}
}
if( bNextPage ){
sqlite3_free(pCsr->aPage);
pCsr->aPage = 0;
pCsr->nRec = 0;
if( pCsr->bOnePage ) return SQLITE_OK;
pCsr->iPgno++;
}else{
if( pCsr->iField<0 || pCsr->pHdrPtr<&pCsr->rec.aBuf[pCsr->nHdr] ){
return SQLITE_OK;
}
/* Advance to the next cell. The next iteration of the loop will load
** the record and so on. */
pCsr->nRec = 0;
pCsr->iCell++;
}
}
}
assert( !"can't get here" );
return SQLITE_OK;
}
/*
** Return true if the cursor is at EOF.
*/
static int dbdataEof(sqlite3_vtab_cursor *pCursor){
DbdataCursor *pCsr = (DbdataCursor*)pCursor;
return pCsr->aPage==0;
}
/*
** Return true if nul-terminated string zSchema ends in "()". Or false
** otherwise.
*/
static int dbdataIsFunction(const char *zSchema){
size_t n = strlen(zSchema);
if( n>2 && zSchema[n-2]=='(' && zSchema[n-1]==')' ){
return (int)n-2;
}
return 0;
}
/*
** Determine the size in pages of database zSchema (where zSchema is
** "main", "temp" or the name of an attached database) and set
** pCsr->szDb accordingly. If successful, return SQLITE_OK. Otherwise,
** an SQLite error code.
*/
static int dbdataDbsize(DbdataCursor *pCsr, const char *zSchema){
DbdataTable *pTab = (DbdataTable*)pCsr->base.pVtab;
char *zSql = 0;
int rc, rc2;
int nFunc = 0;
sqlite3_stmt *pStmt = 0;
if( (nFunc = dbdataIsFunction(zSchema))>0 ){
zSql = sqlite3_mprintf("SELECT %.*s(0)", nFunc, zSchema);
}else{
zSql = sqlite3_mprintf("PRAGMA %Q.page_count", zSchema);
}
if( zSql==0 ) return SQLITE_NOMEM;
rc = sqlite3_prepare_v2(pTab->db, zSql, -1, &pStmt, 0);
sqlite3_free(zSql);
if( rc==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW ){
pCsr->szDb = sqlite3_column_int(pStmt, 0);
}
rc2 = sqlite3_finalize(pStmt);
if( rc==SQLITE_OK ) rc = rc2;
return rc;
}
/*
** Attempt to figure out the encoding of the database by retrieving page 1
** and inspecting the header field. If successful, set the pCsr->enc variable
** and return SQLITE_OK. Otherwise, return an SQLite error code.
*/
static int dbdataGetEncoding(DbdataCursor *pCsr){
int rc = SQLITE_OK;
int nPg1 = 0;
u8 *aPg1 = 0;
rc = dbdataLoadPage(pCsr, 1, &aPg1, &nPg1);
if( rc==SQLITE_OK && nPg1>=(56+4) ){
pCsr->enc = get_uint32(&aPg1[56]);
}
sqlite3_free(aPg1);
return rc;
}
/*
** xFilter method for sqlite_dbdata and sqlite_dbptr.
*/
static int dbdataFilter(
sqlite3_vtab_cursor *pCursor,
int idxNum, const char *idxStr,
int argc, sqlite3_value **argv
){
DbdataCursor *pCsr = (DbdataCursor*)pCursor;
DbdataTable *pTab = (DbdataTable*)pCursor->pVtab;
int rc = SQLITE_OK;
const char *zSchema = "main";
(void)idxStr;
(void)argc;
dbdataResetCursor(pCsr);
assert( pCsr->iPgno==1 );
if( idxNum & 0x01 ){
zSchema = (const char*)sqlite3_value_text(argv[0]);
if( zSchema==0 ) zSchema = "";
}
if( idxNum & 0x02 ){
pCsr->iPgno = sqlite3_value_int(argv[(idxNum & 0x01)]);
pCsr->bOnePage = 1;
}else{
rc = dbdataDbsize(pCsr, zSchema);
}
if( rc==SQLITE_OK ){
int nFunc = 0;
if( pTab->pStmt ){
pCsr->pStmt = pTab->pStmt;
pTab->pStmt = 0;
}else if( (nFunc = dbdataIsFunction(zSchema))>0 ){
char *zSql = sqlite3_mprintf("SELECT %.*s(?2)", nFunc, zSchema);
if( zSql==0 ){
rc = SQLITE_NOMEM;
}else{
rc = sqlite3_prepare_v2(pTab->db, zSql, -1, &pCsr->pStmt, 0);
sqlite3_free(zSql);
}
}else{
rc = sqlite3_prepare_v2(pTab->db,
"SELECT data FROM sqlite_dbpage(?) WHERE pgno=?", -1,
&pCsr->pStmt, 0
);
}
}
if( rc==SQLITE_OK ){
rc = sqlite3_bind_text(pCsr->pStmt, 1, zSchema, -1, SQLITE_TRANSIENT);
}
/* Try to determine the encoding of the db by inspecting the header
** field on page 1. */
if( rc==SQLITE_OK ){
rc = dbdataGetEncoding(pCsr);
}
if( rc!=SQLITE_OK ){
pTab->base.zErrMsg = sqlite3_mprintf("%s", sqlite3_errmsg(pTab->db));
}
if( rc==SQLITE_OK ){
rc = dbdataNext(pCursor);
}
return rc;
}
/*
** Return a column for the sqlite_dbdata or sqlite_dbptr table.
*/
static int dbdataColumn(
sqlite3_vtab_cursor *pCursor,
sqlite3_context *ctx,
int i
){
DbdataCursor *pCsr = (DbdataCursor*)pCursor;
DbdataTable *pTab = (DbdataTable*)pCursor->pVtab;
if( pTab->bPtr ){
switch( i ){
case DBPTR_COLUMN_PGNO:
sqlite3_result_int64(ctx, pCsr->iPgno);
break;
case DBPTR_COLUMN_CHILD: {
int iOff = pCsr->iPgno==1 ? 100 : 0;
if( pCsr->iCell<0 ){
iOff += 8;
}else{
iOff += 12 + pCsr->iCell*2;
if( iOff>pCsr->nPage ) return SQLITE_OK;
iOff = get_uint16(&pCsr->aPage[iOff]);
}
if( iOff<=pCsr->nPage ){
sqlite3_result_int64(ctx, get_uint32(&pCsr->aPage[iOff]));
}
break;
}
}
}else{
switch( i ){
case DBDATA_COLUMN_PGNO:
sqlite3_result_int64(ctx, pCsr->iPgno);
break;
case DBDATA_COLUMN_CELL:
sqlite3_result_int(ctx, pCsr->iCell);
break;
case DBDATA_COLUMN_FIELD:
sqlite3_result_int(ctx, pCsr->iField);
break;
case DBDATA_COLUMN_VALUE: {
if( pCsr->iField<0 ){
sqlite3_result_int64(ctx, pCsr->iIntkey);
}else if( &pCsr->rec.aBuf[pCsr->nRec] >= pCsr->pPtr ){
sqlite3_int64 iType;
dbdataGetVarintU32(pCsr->pHdrPtr, &iType);
dbdataValue(
ctx, pCsr->enc, iType, pCsr->pPtr,
&pCsr->rec.aBuf[pCsr->nRec] - pCsr->pPtr
);
}
break;
}
}
}
return SQLITE_OK;
}
/*
** Return the rowid for an sqlite_dbdata or sqlite_dptr table.
*/
static int dbdataRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
DbdataCursor *pCsr = (DbdataCursor*)pCursor;
*pRowid = pCsr->iRowid;
return SQLITE_OK;
}
/*
** Invoke this routine to register the "sqlite_dbdata" virtual table module
*/
static int sqlite3DbdataRegister(sqlite3 *db){
static sqlite3_module dbdata_module = {
0, /* iVersion */
0, /* xCreate */
dbdataConnect, /* xConnect */
dbdataBestIndex, /* xBestIndex */
dbdataDisconnect, /* xDisconnect */
0, /* xDestroy */
dbdataOpen, /* xOpen - open a cursor */
dbdataClose, /* xClose - close a cursor */
dbdataFilter, /* xFilter - configure scan constraints */
dbdataNext, /* xNext - advance a cursor */
dbdataEof, /* xEof - check for end of scan */
dbdataColumn, /* xColumn - read data */
dbdataRowid, /* xRowid - read data */
0, /* xUpdate */
0, /* xBegin */
0, /* xSync */
0, /* xCommit */
0, /* xRollback */
0, /* xFindMethod */
0, /* xRename */
0, /* xSavepoint */
0, /* xRelease */
0, /* xRollbackTo */
0, /* xShadowName */
0 /* xIntegrity */
};
int rc = sqlite3_create_module(db, "sqlite_dbdata", &dbdata_module, 0);
if( rc==SQLITE_OK ){
rc = sqlite3_create_module(db, "sqlite_dbptr", &dbdata_module, (void*)1);
}
return rc;
}
int sqlite3_dbdata_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
(void)pzErrMsg;
return sqlite3DbdataRegister(db);
}
#endif /* ifndef SQLITE_OMIT_VIRTUALTABLE */
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