/*
** 2017 October 11
**
** 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 module exports a single C function:
**
** int sqlite3_check_freelist(sqlite3 *db, const char *zDb);
**
** This function checks the free-list in database zDb (one of "main",
** "temp", etc.) and reports any errors by invoking the sqlite3_log()
** function. It returns SQLITE_OK if successful, or an SQLite error
** code otherwise. It is not an error if the free-list is corrupted but
** no IO or OOM errors occur.
**
** If this file is compiled and loaded as an SQLite loadable extension,
** it adds an SQL function "checkfreelist" to the database handle, to
** be invoked as follows:
**
** SELECT checkfreelist(<database-name>);
**
** This function performs the same checks as sqlite3_check_freelist(),
** except that it returns all error messages as a single text value,
** separated by newline characters. If the freelist is not corrupted
** in any way, an empty string is returned.
**
** To compile this module for use as an SQLite loadable extension:
**
** gcc -Os -fPIC -shared checkfreelist.c -o checkfreelist.so
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#ifndef SQLITE_AMALGAMATION
# include <string.h>
# include <stdio.h>
# include <stdlib.h>
# include <assert.h>
# define ALWAYS(X) 1
# define NEVER(X) 0
typedef unsigned char u8;
typedef unsigned short u16;
typedef unsigned int u32;
#define get4byte(x) ( \
((u32)((x)[0])<<24) + \
((u32)((x)[1])<<16) + \
((u32)((x)[2])<<8) + \
((u32)((x)[3])) \
)
#endif
/*
** Execute a single PRAGMA statement and return the integer value returned
** via output parameter (*pnOut).
**
** The SQL statement passed as the third argument should be a printf-style
** format string containing a single "%s" which will be replace by the
** value passed as the second argument. e.g.
**
** sqlGetInteger(db, "main", "PRAGMA %s.page_count", pnOut)
**
** executes "PRAGMA main.page_count" and stores the results in (*pnOut).
*/
static int sqlGetInteger(
sqlite3 *db, /* Database handle */
const char *zDb, /* Database name ("main", "temp" etc.) */
const char *zFmt, /* SQL statement format */
u32 *pnOut /* OUT: Integer value */
){
int rc, rc2;
char *zSql;
sqlite3_stmt *pStmt = 0;
int bOk = 0;
zSql = sqlite3_mprintf(zFmt, zDb);
if( zSql==0 ){
rc = SQLITE_NOMEM;
}else{
rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
sqlite3_free(zSql);
}
if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
*pnOut = (u32)sqlite3_column_int(pStmt, 0);
bOk = 1;
}
rc2 = sqlite3_finalize(pStmt);
if( rc==SQLITE_OK ) rc = rc2;
if( rc==SQLITE_OK && bOk==0 ) rc = SQLITE_ERROR;
return rc;
}
/*
** Argument zFmt must be a printf-style format string and must be
** followed by its required arguments. If argument pzOut is NULL,
** then the results of printf()ing the format string are passed to
** sqlite3_log(). Otherwise, they are appended to the string
** at (*pzOut).
*/
static int checkFreelistError(char **pzOut, const char *zFmt, ...){
int rc = SQLITE_OK;
char *zErr = 0;
va_list ap;
va_start(ap, zFmt);
zErr = sqlite3_vmprintf(zFmt, ap);
if( zErr==0 ){
rc = SQLITE_NOMEM;
}else{
if( pzOut ){
*pzOut = sqlite3_mprintf("%s%z%s", *pzOut?"\n":"", *pzOut, zErr);
if( *pzOut==0 ) rc = SQLITE_NOMEM;
}else{
sqlite3_log(SQLITE_ERROR, "checkfreelist: %s", zErr);
}
sqlite3_free(zErr);
}
va_end(ap);
return rc;
}
static int checkFreelist(
sqlite3 *db,
const char *zDb,
char **pzOut
){
/* This query returns one row for each page on the free list. Each row has
** two columns - the page number and page content. */
const char *zTrunk =
"WITH freelist_trunk(i, d, n) AS ("
"SELECT 1, NULL, sqlite_readint32(data, 32) "
"FROM sqlite_dbpage(:1) WHERE pgno=1 "
"UNION ALL "
"SELECT n, data, sqlite_readint32(data) "
"FROM freelist_trunk, sqlite_dbpage(:1) WHERE pgno=n "
")"
"SELECT i, d FROM freelist_trunk WHERE i!=1;";
int rc, rc2; /* Return code */
sqlite3_stmt *pTrunk = 0; /* Compilation of zTrunk */
u32 nPage = 0; /* Number of pages in db */
u32 nExpected = 0; /* Expected number of free pages */
u32 nFree = 0; /* Number of pages on free list */
if( zDb==0 ) zDb = "main";
if( (rc = sqlGetInteger(db, zDb, "PRAGMA %s.page_count", &nPage))
|| (rc = sqlGetInteger(db, zDb, "PRAGMA %s.freelist_count", &nExpected))
){
return rc;
}
rc = sqlite3_prepare_v2(db, zTrunk, -1, &pTrunk, 0);
if( rc!=SQLITE_OK ) return rc;
sqlite3_bind_text(pTrunk, 1, zDb, -1, SQLITE_STATIC);
while( rc==SQLITE_OK && sqlite3_step(pTrunk)==SQLITE_ROW ){
u32 i;
u32 iTrunk = (u32)sqlite3_column_int(pTrunk, 0);
const u8 *aData = (const u8*)sqlite3_column_blob(pTrunk, 1);
u32 nData = (u32)sqlite3_column_bytes(pTrunk, 1);
u32 iNext = get4byte(&aData[0]);
u32 nLeaf = get4byte(&aData[4]);
if( nLeaf>((nData/4)-2-6) ){
rc = checkFreelistError(pzOut,
"leaf count out of range (%d) on trunk page %d",
(int)nLeaf, (int)iTrunk
);
nLeaf = (nData/4) - 2 - 6;
}
nFree += 1+nLeaf;
if( iNext>nPage ){
rc = checkFreelistError(pzOut,
"trunk page %d is out of range", (int)iNext
);
}
for(i=0; rc==SQLITE_OK && i<nLeaf; i++){
u32 iLeaf = get4byte(&aData[8 + 4*i]);
if( iLeaf==0 || iLeaf>nPage ){
rc = checkFreelistError(pzOut,
"leaf page %d is out of range (child %d of trunk page %d)",
(int)iLeaf, (int)i, (int)iTrunk
);
}
}
}
if( rc==SQLITE_OK && nFree!=nExpected ){
rc = checkFreelistError(pzOut,
"free-list count mismatch: actual=%d header=%d",
(int)nFree, (int)nExpected
);
}
rc2 = sqlite3_finalize(pTrunk);
if( rc==SQLITE_OK ) rc = rc2;
return rc;
}
int sqlite3_check_freelist(sqlite3 *db, const char *zDb){
return checkFreelist(db, zDb, 0);
}
static void checkfreelist_function(
sqlite3_context *pCtx,
int nArg,
sqlite3_value **apArg
){
const char *zDb;
int rc;
char *zOut = 0;
sqlite3 *db = sqlite3_context_db_handle(pCtx);
assert( nArg==1 );
zDb = (const char*)sqlite3_value_text(apArg[0]);
rc = checkFreelist(db, zDb, &zOut);
if( rc==SQLITE_OK ){
sqlite3_result_text(pCtx, zOut?zOut:"ok", -1, SQLITE_TRANSIENT);
}else{
sqlite3_result_error_code(pCtx, rc);
}
sqlite3_free(zOut);
}
/*
** An SQL function invoked as follows:
**
** sqlite_readint32(BLOB) -- Decode 32-bit integer from start of blob
*/
static void readint_function(
sqlite3_context *pCtx,
int nArg,
sqlite3_value **apArg
){
const u8 *zBlob;
int nBlob;
int iOff = 0;
u32 iRet = 0;
if( nArg!=1 && nArg!=2 ){
sqlite3_result_error(
pCtx, "wrong number of arguments to function sqlite_readint32()", -1
);
return;
}
if( nArg==2 ){
iOff = sqlite3_value_int(apArg[1]);
}
zBlob = sqlite3_value_blob(apArg[0]);
nBlob = sqlite3_value_bytes(apArg[0]);
if( nBlob>=(iOff+4) ){
iRet = get4byte(&zBlob[iOff]);
}
sqlite3_result_int64(pCtx, (sqlite3_int64)iRet);
}
/*
** Register the SQL functions.
*/
static int cflRegister(sqlite3 *db){
int rc = sqlite3_create_function(
db, "sqlite_readint32", -1, SQLITE_UTF8, 0, readint_function, 0, 0
);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3_create_function(
db, "checkfreelist", 1, SQLITE_UTF8, 0, checkfreelist_function, 0, 0
);
return rc;
}
/*
** Extension load function.
*/
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_checkfreelist_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
SQLITE_EXTENSION_INIT2(pApi);
return cflRegister(db);
}