/*
** Copyright (c) 1999, 2000 D. Richard Hipp
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of the GNU General Public
** License as published by the Free Software Foundation; either
** version 2 of the License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
** General Public License for more details.
**
** You should have received a copy of the GNU General Public
** License along with this library; if not, write to the
** Free Software Foundation, Inc., 59 Temple Place - Suite 330,
** Boston, MA 02111-1307, USA.
**
** Author contact information:
** drh@hwaci.com
** http://www.hwaci.com/drh/
**
*************************************************************************
** This file contains code to implement the database backend (DBBE)
** for sqlite. The database backend is the interface between
** sqlite and the code that does the actually reading and writing
** of information to the disk.
**
** This file uses GDBM as the database backend. It should be
** relatively simple to convert to a different database such
** as NDBM, SDBM, or BerkeleyDB.
**
** $Id: dbbe.c,v 1.15 2000/06/21 13:59:11 drh Exp $
*/
#include "sqliteInt.h"
#include <gdbm.h>
#include <sys/stat.h>
#include <unistd.h>
#include <ctype.h>
#include <time.h>
/*
** Information about each open disk file is an instance of this
** structure. There will only be one such structure for each
** disk file. If the VDBE opens the same file twice (as will happen
** for a self-join, for example) then two DbbeCursor structures are
** created but there is only a single BeFile structure with an
** nRef of 2.
*/
typedef struct BeFile BeFile;
struct BeFile {
char *zName; /* Name of the file */
GDBM_FILE dbf; /* The file itself */
int nRef; /* Number of references */
int delOnClose; /* Delete when closing */
int writeable; /* Opened for writing */
BeFile *pNext, *pPrev; /* Next and previous on list of open files */
};
/*
** The following structure holds the current state of the RC4 algorithm.
** We use RC4 as a random number generator. Each call to RC4 gives
** a random 8-bit number.
**
** Nothing in this file or anywhere else in SQLite does any kind of
** encryption. The RC4 algorithm is being used as a PRNG (pseudo-random
** number generator) not as an encryption device.
*/
struct rc4 {
int i, j;
int s[256];
};
/*
** The complete database is an instance of the following structure.
*/
struct Dbbe {
char *zDir; /* The directory containing the database */
int write; /* True for write permission */
BeFile *pOpen; /* List of open files */
int nTemp; /* Number of temporary files created */
FILE **apTemp; /* Space to hold temporary file pointers */
char **azTemp; /* Names of the temporary files */
struct rc4 rc4; /* The random number generator */
};
/*
** An cursor into a database file is an instance of the following structure.
** There can only be a single BeFile structure for each disk file, but
** there can be multiple DbbeCursor structures. Each DbbeCursor represents
** a cursor pointing to a particular part of the open BeFile. The
** BeFile.nRef field hold a count of the number of DbbeCursor structures
** associated with the same disk file.
*/
struct DbbeCursor {
Dbbe *pBe; /* The database of which this record is a part */
BeFile *pFile; /* The database file for this table */
datum key; /* Most recently used key */
datum data; /* Most recent data */
int needRewind; /* Next key should be the first */
int readPending; /* The fetch hasn't actually been done yet */
};
/*
** Initialize the RC4 PRNG. "seed" is a pointer to some random
** data used to initialize the PRNG.
*/
static void rc4init(struct rc4 *p, char *seed, int seedlen){
int i;
char k[256];
p->j = 0;
p->i = 0;
for(i=0; i<256; i++){
p->s[i] = i;
k[i] = seed[i%seedlen];
}
for(i=0; i<256; i++){
int t;
p->j = (p->j + p->s[i] + k[i]) & 0xff;
t = p->s[p->j];
p->s[p->j] = p->s[i];
p->s[i] = t;
}
}
/*
** Get a single 8-bit random value from the RC4 PRNG.
*/
static int rc4byte(struct rc4 *p){
int t;
p->i = (p->i + 1) & 0xff;
p->j = (p->j + p->s[p->i]) & 0xff;
t = p->s[p->i];
p->s[p->i] = p->s[p->j];
p->s[p->j] = t;
t = p->s[p->i] + p->s[p->j];
return t & 0xff;
}
/*
** This routine opens a new database. For the GDBM driver
** implemented here, the database name is the name of the directory
** containing all the files of the database.
**
** If successful, a pointer to the Dbbe structure is returned.
** If there are errors, an appropriate error message is left
** in *pzErrMsg and NULL is returned.
*/
Dbbe *sqliteDbbeOpen(
const char *zName, /* The name of the database */
int writeFlag, /* True if we will be writing to the database */
int createFlag, /* True to create database if it doesn't exist */
char **pzErrMsg /* Write error messages (if any) here */
){
Dbbe *pNew;
struct stat statbuf;
char *zMaster;
if( !writeFlag ) createFlag = 0;
if( stat(zName, &statbuf)!=0 ){
if( createFlag ) mkdir(zName, 0750);
if( stat(zName, &statbuf)!=0 ){
sqliteSetString(pzErrMsg, createFlag ?
"can't find or create directory \"" : "can't find directory \"",
zName, "\"", 0);
return 0;
}
}
if( !S_ISDIR(statbuf.st_mode) ){
sqliteSetString(pzErrMsg, "not a directory: \"", zName, "\"", 0);
return 0;
}
if( access(zName, writeFlag ? (X_OK|W_OK|R_OK) : (X_OK|R_OK)) ){
sqliteSetString(pzErrMsg, "access permission denied", 0);
return 0;
}
zMaster = 0;
sqliteSetString(&zMaster, zName, "/" MASTER_NAME ".tbl", 0);
if( stat(zMaster, &statbuf)==0
&& access(zMaster, writeFlag ? (W_OK|R_OK) : R_OK)!=0 ){
sqliteSetString(pzErrMsg, "access permission denied for ", zMaster, 0);
sqliteFree(zMaster);
return 0;
}
sqliteFree(zMaster);
pNew = sqliteMalloc(sizeof(Dbbe) + strlen(zName) + 1);
if( pNew==0 ){
sqliteSetString(pzErrMsg, "out of memory", 0);
return 0;
}
pNew->zDir = (char*)&pNew[1];
strcpy(pNew->zDir, zName);
pNew->write = writeFlag;
pNew->pOpen = 0;
time(&statbuf.st_ctime);
rc4init(&pNew->rc4, (char*)&statbuf, sizeof(statbuf));
return pNew;
}
/*
** Completely shutdown the given database. Close all files. Free all memory.
*/
void sqliteDbbeClose(Dbbe *pBe){
BeFile *pFile, *pNext;
int i;
for(pFile=pBe->pOpen; pFile; pFile=pNext){
pNext = pFile->pNext;
gdbm_close(pFile->dbf);
memset(pFile, 0, sizeof(*pFile));
sqliteFree(pFile);
}
for(i=0; i<pBe->nTemp; i++){
if( pBe->apTemp[i]!=0 ){
unlink(pBe->azTemp[i]);
fclose(pBe->apTemp[i]);
sqliteFree(pBe->azTemp[i]);
pBe->apTemp[i] = 0;
pBe->azTemp[i] = 0;
break;
}
}
sqliteFree(pBe->azTemp);
sqliteFree(pBe->apTemp);
memset(pBe, 0, sizeof(*pBe));
sqliteFree(pBe);
}
/*
** Translate the name of an SQL table (or index) into the name
** of a file that holds the key/data pairs for that table or
** index. Space to hold the filename is obtained from
** sqliteMalloc() and must be freed by the calling function.
*/
static char *sqliteFileOfTable(Dbbe *pBe, const char *zTable){
char *zFile = 0;
int i;
sqliteSetString(&zFile, pBe->zDir, "/", zTable, ".tbl", 0);
if( zFile==0 ) return 0;
for(i=strlen(pBe->zDir)+1; zFile[i]; i++){
int c = zFile[i];
if( isupper(c) ){
zFile[i] = tolower(c);
}else if( !isalnum(c) && c!='-' && c!='_' && c!='.' ){
zFile[i] = '+';
}
}
return zFile;
}
/*
** Generate a random filename with the given prefix. The new filename
** is written into zBuf[]. The calling function must insure that
** zBuf[] is big enough to hold the prefix plus 20 or so extra
** characters.
**
** Very random names are chosen so that the chance of a
** collision with an existing filename is very very small.
*/
static void randomName(struct rc4 *pRc4, char *zBuf, char *zPrefix){
int i, j;
static const char zRandomChars[] = "abcdefghijklmnopqrstuvwxyz0123456789";
strcpy(zBuf, zPrefix);
j = strlen(zBuf);
for(i=0; i<15; i++){
int c = rc4byte(pRc4) % (sizeof(zRandomChars) - 1);
zBuf[j++] = zRandomChars[c];
}
zBuf[j] = 0;
}
/*
** Open a new table cursor. Write a pointer to the corresponding
** DbbeCursor structure into *ppCursr. Return an integer success
** code:
**
** SQLITE_OK It worked!
**
** SQLITE_NOMEM sqliteMalloc() failed
**
** SQLITE_PERM Attempt to access a file for which file
** access permission is denied
**
** SQLITE_BUSY Another thread or process is already using
** the corresponding file and has that file locked.
**
** SQLITE_READONLY The current thread already has this file open
** readonly but you are trying to open for writing.
** (This can happen if a SELECT callback tries to
** do an UPDATE or DELETE.)
**
** If zTable is 0 or "", then a temporary database file is created and
** a cursor to that temporary file is opened. The temporary file
** will be deleted from the disk when it is closed.
*/
int sqliteDbbeOpenCursor(
Dbbe *pBe, /* The database the table belongs to */
const char *zTable, /* The SQL name of the file to be opened */
int writeable, /* True to open for writing */
DbbeCursor **ppCursr /* Write the resulting table pointer here */
){
char *zFile; /* Name of the table file */
DbbeCursor *pCursr; /* The new table cursor */
BeFile *pFile; /* The underlying data file for this table */
int rc = SQLITE_OK; /* Return value */
int rw_mask; /* Permissions mask for opening a table */
int mode; /* Mode for opening a table */
*ppCursr = 0;
pCursr = sqliteMalloc( sizeof(*pCursr) );
if( pCursr==0 ) return SQLITE_NOMEM;
if( zTable ){
zFile = sqliteFileOfTable(pBe, zTable);
for(pFile=pBe->pOpen; pFile; pFile=pFile->pNext){
if( strcmp(pFile->zName,zFile)==0 ) break;
}
}else{
pFile = 0;
zFile = 0;
}
if( pFile==0 ){
if( writeable ){
rw_mask = GDBM_WRCREAT | GDBM_FAST;
mode = 0640;
}else{
rw_mask = GDBM_READER;
mode = 0640;
}
pFile = sqliteMalloc( sizeof(*pFile) );
if( pFile==0 ){
sqliteFree(zFile);
return SQLITE_NOMEM;
}
if( zFile ){
if( !writeable || pBe->write ){
pFile->dbf = gdbm_open(zFile, 0, rw_mask, mode, 0);
}else{
pFile->dbf = 0;
}
}else{
int limit;
struct rc4 *pRc4;
char zRandom[50];
pRc4 = &pBe->rc4;
zFile = 0;
limit = 5;
do {
randomName(&pBe->rc4, zRandom, "_temp_table_");
sqliteFree(zFile);
zFile = sqliteFileOfTable(pBe, zRandom);
pFile->dbf = gdbm_open(zFile, 0, rw_mask, mode, 0);
}while( pFile->dbf==0 && limit-- >= 0);
pFile->delOnClose = 1;
}
pFile->writeable = writeable;
pFile->zName = zFile;
pFile->nRef = 1;
pFile->pPrev = 0;
if( pBe->pOpen ){
pBe->pOpen->pPrev = pFile;
}
pFile->pNext = pBe->pOpen;
pBe->pOpen = pFile;
if( pFile->dbf==0 ){
if( !writeable && access(zFile,0) ){
/* Trying to read a non-existant file. This is OK. All the
** reads will return empty, which is what we want. */
rc = SQLITE_OK;
}else if( access(zFile,W_OK|R_OK) ){
rc = SQLITE_PERM;
}else{
rc = SQLITE_BUSY;
}
}
}else{
sqliteFree(zFile);
pFile->nRef++;
if( writeable && !pFile->writeable ){
rc = SQLITE_READONLY;
}
}
pCursr->pBe = pBe;
pCursr->pFile = pFile;
pCursr->readPending = 0;
pCursr->needRewind = 1;
*ppCursr = pCursr;
return rc;
}
/*
** Drop a table from the database. The file on the disk that corresponds
** to this table is deleted.
*/
void sqliteDbbeDropTable(Dbbe *pBe, const char *zTable){
char *zFile; /* Name of the table file */
zFile = sqliteFileOfTable(pBe, zTable);
unlink(zFile);
sqliteFree(zFile);
}
/*
** Reorganize a table to reduce search times and disk usage.
*/
void sqliteDbbeReorganizeTable(Dbbe *pBe, const char *zTable){
DbbeCursor *pCrsr;
if( sqliteDbbeOpenCursor(pBe, zTable, 1, &pCrsr)!=SQLITE_OK ){
return;
}
if( pCrsr && pCrsr->pFile && pCrsr->pFile->dbf ){
gdbm_reorganize(pCrsr->pFile->dbf);
}
if( pCrsr ){
sqliteDbbeCloseCursor(pCrsr);
}
}
/*
** Close a cursor previously opened by sqliteDbbeOpenCursor().
**
** There can be multiple cursors pointing to the same open file.
** The underlying file is not closed until all cursors have been
** closed. This routine decrements the BeFile.nref field of the
** underlying file and closes the file when nref reaches 0.
*/
void sqliteDbbeCloseCursor(DbbeCursor *pCursr){
BeFile *pFile;
Dbbe *pBe;
if( pCursr==0 ) return;
pFile = pCursr->pFile;
pBe = pCursr->pBe;
pFile->nRef--;
if( pFile->dbf!=NULL ){
gdbm_sync(pFile->dbf);
}
if( pFile->nRef<=0 ){
if( pFile->dbf!=NULL ){
gdbm_close(pFile->dbf);
}
if( pFile->pPrev ){
pFile->pPrev->pNext = pFile->pNext;
}else{
pBe->pOpen = pFile->pNext;
}
if( pFile->pNext ){
pFile->pNext->pPrev = pFile->pPrev;
}
if( pFile->delOnClose ){
unlink(pFile->zName);
}
sqliteFree(pFile->zName);
memset(pFile, 0, sizeof(*pFile));
sqliteFree(pFile);
}
if( pCursr->key.dptr ) free(pCursr->key.dptr);
if( pCursr->data.dptr ) free(pCursr->data.dptr);
memset(pCursr, 0, sizeof(*pCursr));
sqliteFree(pCursr);
}
/*
** Clear the given datum
*/
static void datumClear(datum *p){
if( p->dptr ) free(p->dptr);
p->dptr = 0;
p->dsize = 0;
}
/*
** Fetch a single record from an open cursor. Return 1 on success
** and 0 on failure.
*/
int sqliteDbbeFetch(DbbeCursor *pCursr, int nKey, char *pKey){
datum key;
key.dsize = nKey;
key.dptr = pKey;
datumClear(&pCursr->key);
datumClear(&pCursr->data);
if( pCursr->pFile && pCursr->pFile->dbf ){
pCursr->data = gdbm_fetch(pCursr->pFile->dbf, key);
}
return pCursr->data.dptr!=0;
}
/*
** Return 1 if the given key is already in the table. Return 0
** if it is not.
*/
int sqliteDbbeTest(DbbeCursor *pCursr, int nKey, char *pKey){
datum key;
int result = 0;
key.dsize = nKey;
key.dptr = pKey;
if( pCursr->pFile && pCursr->pFile->dbf ){
result = gdbm_exists(pCursr->pFile->dbf, key);
}
return result;
}
/*
** Copy bytes from the current key or data into a buffer supplied by
** the calling function. Return the number of bytes copied.
*/
int sqliteDbbeCopyKey(DbbeCursor *pCursr, int offset, int size, char *zBuf){
int n;
if( offset>=pCursr->key.dsize ) return 0;
if( offset+size>pCursr->key.dsize ){
n = pCursr->key.dsize - offset;
}else{
n = size;
}
memcpy(zBuf, &pCursr->key.dptr[offset], n);
return n;
}
int sqliteDbbeCopyData(DbbeCursor *pCursr, int offset, int size, char *zBuf){
int n;
if( pCursr->readPending && pCursr->pFile && pCursr->pFile->dbf ){
pCursr->data = gdbm_fetch(pCursr->pFile->dbf, pCursr->key);
pCursr->readPending = 0;
}
if( offset>=pCursr->data.dsize ) return 0;
if( offset+size>pCursr->data.dsize ){
n = pCursr->data.dsize - offset;
}else{
n = size;
}
memcpy(zBuf, &pCursr->data.dptr[offset], n);
return n;
}
/*
** Return a pointer to bytes from the key or data. The data returned
** is ephemeral.
*/
char *sqliteDbbeReadKey(DbbeCursor *pCursr, int offset){
if( offset<0 || offset>=pCursr->key.dsize ) return "";
return &pCursr->key.dptr[offset];
}
char *sqliteDbbeReadData(DbbeCursor *pCursr, int offset){
if( pCursr->readPending && pCursr->pFile && pCursr->pFile->dbf ){
pCursr->data = gdbm_fetch(pCursr->pFile->dbf, pCursr->key);
pCursr->readPending = 0;
}
if( offset<0 || offset>=pCursr->data.dsize ) return "";
return &pCursr->data.dptr[offset];
}
/*
** Return the total number of bytes in either data or key.
*/
int sqliteDbbeKeyLength(DbbeCursor *pCursr){
return pCursr->key.dsize;
}
int sqliteDbbeDataLength(DbbeCursor *pCursr){
if( pCursr->readPending && pCursr->pFile && pCursr->pFile->dbf ){
pCursr->data = gdbm_fetch(pCursr->pFile->dbf, pCursr->key);
pCursr->readPending = 0;
}
return pCursr->data.dsize;
}
/*
** Make is so that the next call to sqliteNextKey() finds the first
** key of the table.
*/
int sqliteDbbeRewind(DbbeCursor *pCursr){
pCursr->needRewind = 1;
return SQLITE_OK;
}
/*
** Read the next key from the table. Return 1 on success. Return
** 0 if there are no more keys.
*/
int sqliteDbbeNextKey(DbbeCursor *pCursr){
datum nextkey;
int rc;
if( pCursr==0 || pCursr->pFile==0 || pCursr->pFile->dbf==0 ){
pCursr->readPending = 0;
return 0;
}
if( pCursr->needRewind ){
nextkey = gdbm_firstkey(pCursr->pFile->dbf);
pCursr->needRewind = 0;
}else{
nextkey = gdbm_nextkey(pCursr->pFile->dbf, pCursr->key);
}
datumClear(&pCursr->key);
datumClear(&pCursr->data);
pCursr->key = nextkey;
if( pCursr->key.dptr ){
pCursr->readPending = 1;
rc = 1;
}else{
pCursr->needRewind = 1;
pCursr->readPending = 0;
rc = 0;
}
return rc;
}
/*
** Get a new integer key.
*/
int sqliteDbbeNew(DbbeCursor *pCursr){
int iKey;
datum key;
int go = 1;
int i;
struct rc4 *pRc4;
if( pCursr->pFile==0 || pCursr->pFile->dbf==0 ) return 1;
pRc4 = &pCursr->pBe->rc4;
while( go ){
iKey = 0;
for(i=0; i<4; i++){
iKey = (iKey<<8) + rc4byte(pRc4);
}
key.dptr = (char*)&iKey;
key.dsize = 4;
go = gdbm_exists(pCursr->pFile->dbf, key);
}
return iKey;
}
/*
** Write an entry into the table. Overwrite any prior entry with the
** same key.
*/
int sqliteDbbePut(DbbeCursor *pCursr, int nKey,char *pKey,int nData,char *pData){
datum data, key;
int rc;
if( pCursr->pFile==0 || pCursr->pFile->dbf==0 ) return SQLITE_ERROR;
data.dsize = nData;
data.dptr = pData;
key.dsize = nKey;
key.dptr = pKey;
rc = gdbm_store(pCursr->pFile->dbf, key, data, GDBM_REPLACE);
if( rc ) rc = SQLITE_ERROR;
datumClear(&pCursr->key);
datumClear(&pCursr->data);
return rc;
}
/*
** Remove an entry from a table, if the entry exists.
*/
int sqliteDbbeDelete(DbbeCursor *pCursr, int nKey, char *pKey){
datum key;
int rc;
datumClear(&pCursr->key);
datumClear(&pCursr->data);
if( pCursr->pFile==0 || pCursr->pFile->dbf==0 ) return SQLITE_ERROR;
key.dsize = nKey;
key.dptr = pKey;
rc = gdbm_delete(pCursr->pFile->dbf, key);
if( rc ) rc = SQLITE_ERROR;
return rc;
}
/*
** Open a temporary file. The file should be deleted when closed.
**
** Note that we can't use the old Unix trick of opening the file
** and then immediately unlinking the file. That works great
** under Unix, but fails when we try to port to Windows.
*/
int sqliteDbbeOpenTempFile(Dbbe *pBe, FILE **ppFile){
char *zFile; /* Full name of the temporary file */
char zBuf[50]; /* Base name of the temporary file */
int i; /* Loop counter */
int limit; /* Prevent an infinite loop */
int rc = SQLITE_OK; /* Value returned by this function */
for(i=0; i<pBe->nTemp; i++){
if( pBe->apTemp[i]==0 ) break;
}
if( i>=pBe->nTemp ){
pBe->nTemp++;
pBe->apTemp = sqliteRealloc(pBe->apTemp, pBe->nTemp*sizeof(FILE*) );
pBe->azTemp = sqliteRealloc(pBe->azTemp, pBe->nTemp*sizeof(char*) );
}
if( pBe->apTemp==0 ){
*ppFile = 0;
return SQLITE_NOMEM;
}
limit = 4;
zFile = 0;
do{
randomName(&pBe->rc4, zBuf, "/_temp_file_");
sqliteFree(zFile);
zFile = 0;
sqliteSetString(&zFile, pBe->zDir, zBuf, 0);
}while( access(zFile,0)==0 && limit-- >= 0 );
*ppFile = pBe->apTemp[i] = fopen(zFile, "w+");
if( pBe->apTemp[i]==0 ){
rc = SQLITE_ERROR;
sqliteFree(zFile);
pBe->azTemp[i] = 0;
}else{
pBe->azTemp[i] = zFile;
}
return rc;
}
/*
** Close a temporary file opened using sqliteDbbeOpenTempFile()
*/
void sqliteDbbeCloseTempFile(Dbbe *pBe, FILE *f){
int i;
for(i=0; i<pBe->nTemp; i++){
if( pBe->apTemp[i]==f ){
unlink(pBe->azTemp[i]);
sqliteFree(pBe->azTemp[i]);
pBe->apTemp[i] = 0;
pBe->azTemp[i] = 0;
break;
}
}
fclose(f);
}