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-rw-r--r--src/memdb.c345
1 files changed, 292 insertions, 53 deletions
diff --git a/src/memdb.c b/src/memdb.c
index b25e13cbc..965ec36d4 100644
--- a/src/memdb.c
+++ b/src/memdb.c
@@ -17,32 +17,89 @@
** sqlite3_deserialize().
*/
#include "sqliteInt.h"
-#ifdef SQLITE_ENABLE_DESERIALIZE
+#ifndef SQLITE_OMIT_DESERIALIZE
/*
** Forward declaration of objects used by this utility
*/
typedef struct sqlite3_vfs MemVfs;
typedef struct MemFile MemFile;
+typedef struct MemStore MemStore;
/* Access to a lower-level VFS that (might) implement dynamic loading,
** access to randomness, etc.
*/
#define ORIGVFS(p) ((sqlite3_vfs*)((p)->pAppData))
-/* An open file */
-struct MemFile {
- sqlite3_file base; /* IO methods */
+/* Storage for a memdb file.
+**
+** An memdb object can be shared or separate. Shared memdb objects can be
+** used by more than one database connection. Mutexes are used by shared
+** memdb objects to coordinate access. Separate memdb objects are only
+** connected to a single database connection and do not require additional
+** mutexes.
+**
+** Shared memdb objects have .zFName!=0 and .pMutex!=0. They are created
+** using "file:/name?vfs=memdb". The first character of the name must be
+** "/" or else the object will be a separate memdb object. All shared
+** memdb objects are stored in memdb_g.apMemStore[] in an arbitrary order.
+**
+** Separate memdb objects are created using a name that does not begin
+** with "/" or using sqlite3_deserialize().
+**
+** Access rules for shared MemStore objects:
+**
+** * .zFName is initialized when the object is created and afterwards
+** is unchanged until the object is destroyed. So it can be accessed
+** at any time as long as we know the object is not being destroyed,
+** which means while either the SQLITE_MUTEX_STATIC_VFS1 or
+** .pMutex is held or the object is not part of memdb_g.apMemStore[].
+**
+** * Can .pMutex can only be changed while holding the
+** SQLITE_MUTEX_STATIC_VFS1 mutex or while the object is not part
+** of memdb_g.apMemStore[].
+**
+** * Other fields can only be changed while holding the .pMutex mutex
+** or when the .nRef is less than zero and the object is not part of
+** memdb_g.apMemStore[].
+**
+** * The .aData pointer has the added requirement that it can can only
+** be changed (for resizing) when nMmap is zero.
+**
+*/
+struct MemStore {
sqlite3_int64 sz; /* Size of the file */
sqlite3_int64 szAlloc; /* Space allocated to aData */
sqlite3_int64 szMax; /* Maximum allowed size of the file */
unsigned char *aData; /* content of the file */
+ sqlite3_mutex *pMutex; /* Used by shared stores only */
int nMmap; /* Number of memory mapped pages */
unsigned mFlags; /* Flags */
+ int nRdLock; /* Number of readers */
+ int nWrLock; /* Number of writers. (Always 0 or 1) */
+ int nRef; /* Number of users of this MemStore */
+ char *zFName; /* The filename for shared stores */
+};
+
+/* An open file */
+struct MemFile {
+ sqlite3_file base; /* IO methods */
+ MemStore *pStore; /* The storage */
int eLock; /* Most recent lock against this file */
};
/*
+** File-scope variables for holding the memdb files that are accessible
+** to multiple database connections in separate threads.
+**
+** Must hold SQLITE_MUTEX_STATIC_VFS1 to access any part of this object.
+*/
+static struct MemFS {
+ int nMemStore; /* Number of shared MemStore objects */
+ MemStore **apMemStore; /* Array of all shared MemStore objects */
+} memdb_g;
+
+/*
** Methods for MemFile
*/
static int memdbClose(sqlite3_file*);
@@ -95,7 +152,10 @@ static sqlite3_vfs memdb_vfs = {
memdbSleep, /* xSleep */
0, /* memdbCurrentTime, */ /* xCurrentTime */
memdbGetLastError, /* xGetLastError */
- memdbCurrentTimeInt64 /* xCurrentTimeInt64 */
+ memdbCurrentTimeInt64, /* xCurrentTimeInt64 */
+ 0, /* xSetSystemCall */
+ 0, /* xGetSystemCall */
+ 0, /* xNextSystemCall */
};
static const sqlite3_io_methods memdb_io_methods = {
@@ -120,19 +180,67 @@ static const sqlite3_io_methods memdb_io_methods = {
memdbUnfetch /* xUnfetch */
};
+/*
+** Enter/leave the mutex on a MemStore
+*/
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE==0
+static void memdbEnter(MemStore *p){
+ UNUSED_PARAMETER(p);
+}
+static void memdbLeave(MemStore *p){
+ UNUSED_PARAMETER(p);
+}
+#else
+static void memdbEnter(MemStore *p){
+ sqlite3_mutex_enter(p->pMutex);
+}
+static void memdbLeave(MemStore *p){
+ sqlite3_mutex_leave(p->pMutex);
+}
+#endif
+
/*
** Close an memdb-file.
-**
-** The pData pointer is owned by the application, so there is nothing
-** to free. Unless the SQLITE_DESERIALIZE_FREEONCLOSE flag is set,
-** in which case we own the pData pointer and need to free it.
+** Free the underlying MemStore object when its refcount drops to zero
+** or less.
*/
static int memdbClose(sqlite3_file *pFile){
- MemFile *p = (MemFile *)pFile;
- if( p->mFlags & SQLITE_DESERIALIZE_FREEONCLOSE ){
- sqlite3_free(p->aData);
+ MemStore *p = ((MemFile*)pFile)->pStore;
+ if( p->zFName ){
+ int i;
+#ifndef SQLITE_MUTEX_OMIT
+ sqlite3_mutex *pVfsMutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1);
+#endif
+ sqlite3_mutex_enter(pVfsMutex);
+ for(i=0; ALWAYS(i<memdb_g.nMemStore); i++){
+ if( memdb_g.apMemStore[i]==p ){
+ memdbEnter(p);
+ if( p->nRef==1 ){
+ memdb_g.apMemStore[i] = memdb_g.apMemStore[--memdb_g.nMemStore];
+ if( memdb_g.nMemStore==0 ){
+ sqlite3_free(memdb_g.apMemStore);
+ memdb_g.apMemStore = 0;
+ }
+ }
+ break;
+ }
+ }
+ sqlite3_mutex_leave(pVfsMutex);
+ }else{
+ memdbEnter(p);
+ }
+ p->nRef--;
+ if( p->nRef<=0 ){
+ if( p->mFlags & SQLITE_DESERIALIZE_FREEONCLOSE ){
+ sqlite3_free(p->aData);
+ }
+ memdbLeave(p);
+ sqlite3_mutex_free(p->pMutex);
+ sqlite3_free(p);
+ }else{
+ memdbLeave(p);
}
return SQLITE_OK;
}
@@ -146,20 +254,23 @@ static int memdbRead(
int iAmt,
sqlite_int64 iOfst
){
- MemFile *p = (MemFile *)pFile;
+ MemStore *p = ((MemFile*)pFile)->pStore;
+ memdbEnter(p);
if( iOfst+iAmt>p->sz ){
memset(zBuf, 0, iAmt);
if( iOfst<p->sz ) memcpy(zBuf, p->aData+iOfst, p->sz - iOfst);
+ memdbLeave(p);
return SQLITE_IOERR_SHORT_READ;
}
memcpy(zBuf, p->aData+iOfst, iAmt);
+ memdbLeave(p);
return SQLITE_OK;
}
/*
** Try to enlarge the memory allocation to hold at least sz bytes
*/
-static int memdbEnlarge(MemFile *p, sqlite3_int64 newSz){
+static int memdbEnlarge(MemStore *p, sqlite3_int64 newSz){
unsigned char *pNew;
if( (p->mFlags & SQLITE_DESERIALIZE_RESIZEABLE)==0 || p->nMmap>0 ){
return SQLITE_FULL;
@@ -185,19 +296,27 @@ static int memdbWrite(
int iAmt,
sqlite_int64 iOfst
){
- MemFile *p = (MemFile *)pFile;
- if( NEVER(p->mFlags & SQLITE_DESERIALIZE_READONLY) ) return SQLITE_READONLY;
+ MemStore *p = ((MemFile*)pFile)->pStore;
+ memdbEnter(p);
+ if( NEVER(p->mFlags & SQLITE_DESERIALIZE_READONLY) ){
+ /* Can't happen: memdbLock() will return SQLITE_READONLY before
+ ** reaching this point */
+ memdbLeave(p);
+ return SQLITE_IOERR_WRITE;
+ }
if( iOfst+iAmt>p->sz ){
int rc;
if( iOfst+iAmt>p->szAlloc
&& (rc = memdbEnlarge(p, iOfst+iAmt))!=SQLITE_OK
){
+ memdbLeave(p);
return rc;
}
if( iOfst>p->sz ) memset(p->aData+p->sz, 0, iOfst-p->sz);
p->sz = iOfst+iAmt;
}
memcpy(p->aData+iOfst, z, iAmt);
+ memdbLeave(p);
return SQLITE_OK;
}
@@ -209,16 +328,24 @@ static int memdbWrite(
** the size of a file, never to increase the size.
*/
static int memdbTruncate(sqlite3_file *pFile, sqlite_int64 size){
- MemFile *p = (MemFile *)pFile;
- if( NEVER(size>p->sz) ) return SQLITE_FULL;
- p->sz = size;
- return SQLITE_OK;
+ MemStore *p = ((MemFile*)pFile)->pStore;
+ int rc = SQLITE_OK;
+ memdbEnter(p);
+ if( NEVER(size>p->sz) ){
+ rc = SQLITE_FULL;
+ }else{
+ p->sz = size;
+ }
+ memdbLeave(p);
+ return rc;
}
/*
** Sync an memdb-file.
*/
static int memdbSync(sqlite3_file *pFile, int flags){
+ UNUSED_PARAMETER(pFile);
+ UNUSED_PARAMETER(flags);
return SQLITE_OK;
}
@@ -226,8 +353,10 @@ static int memdbSync(sqlite3_file *pFile, int flags){
** Return the current file-size of an memdb-file.
*/
static int memdbFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
- MemFile *p = (MemFile *)pFile;
+ MemStore *p = ((MemFile*)pFile)->pStore;
+ memdbEnter(p);
*pSize = p->sz;
+ memdbLeave(p);
return SQLITE_OK;
}
@@ -235,19 +364,48 @@ static int memdbFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
** Lock an memdb-file.
*/
static int memdbLock(sqlite3_file *pFile, int eLock){
- MemFile *p = (MemFile *)pFile;
- if( eLock>SQLITE_LOCK_SHARED
- && (p->mFlags & SQLITE_DESERIALIZE_READONLY)!=0
- ){
- return SQLITE_READONLY;
+ MemFile *pThis = (MemFile*)pFile;
+ MemStore *p = pThis->pStore;
+ int rc = SQLITE_OK;
+ if( eLock==pThis->eLock ) return SQLITE_OK;
+ memdbEnter(p);
+ if( eLock>SQLITE_LOCK_SHARED ){
+ if( p->mFlags & SQLITE_DESERIALIZE_READONLY ){
+ rc = SQLITE_READONLY;
+ }else if( pThis->eLock<=SQLITE_LOCK_SHARED ){
+ if( p->nWrLock ){
+ rc = SQLITE_BUSY;
+ }else{
+ p->nWrLock = 1;
+ }
+ }
+ }else if( eLock==SQLITE_LOCK_SHARED ){
+ if( pThis->eLock > SQLITE_LOCK_SHARED ){
+ assert( p->nWrLock==1 );
+ p->nWrLock = 0;
+ }else if( p->nWrLock ){
+ rc = SQLITE_BUSY;
+ }else{
+ p->nRdLock++;
+ }
+ }else{
+ assert( eLock==SQLITE_LOCK_NONE );
+ if( pThis->eLock>SQLITE_LOCK_SHARED ){
+ assert( p->nWrLock==1 );
+ p->nWrLock = 0;
+ }
+ assert( p->nRdLock>0 );
+ p->nRdLock--;
}
- p->eLock = eLock;
- return SQLITE_OK;
+ if( rc==SQLITE_OK ) pThis->eLock = eLock;
+ memdbLeave(p);
+ return rc;
}
-#if 0 /* Never used because memdbAccess() always returns false */
+#if 0
/*
-** Check if another file-handle holds a RESERVED lock on an memdb-file.
+** This interface is only used for crash recovery, which does not
+** occur on an in-memory database.
*/
static int memdbCheckReservedLock(sqlite3_file *pFile, int *pResOut){
*pResOut = 0;
@@ -255,12 +413,14 @@ static int memdbCheckReservedLock(sqlite3_file *pFile, int *pResOut){
}
#endif
+
/*
** File control method. For custom operations on an memdb-file.
*/
static int memdbFileControl(sqlite3_file *pFile, int op, void *pArg){
- MemFile *p = (MemFile *)pFile;
+ MemStore *p = ((MemFile*)pFile)->pStore;
int rc = SQLITE_NOTFOUND;
+ memdbEnter(p);
if( op==SQLITE_FCNTL_VFSNAME ){
*(char**)pArg = sqlite3_mprintf("memdb(%p,%lld)", p->aData, p->sz);
rc = SQLITE_OK;
@@ -278,6 +438,7 @@ static int memdbFileControl(sqlite3_file *pFile, int op, void *pArg){
*(sqlite3_int64*)pArg = iLimit;
rc = SQLITE_OK;
}
+ memdbLeave(p);
return rc;
}
@@ -294,6 +455,7 @@ static int memdbSectorSize(sqlite3_file *pFile){
** Return the device characteristic flags supported by an memdb-file.
*/
static int memdbDeviceCharacteristics(sqlite3_file *pFile){
+ UNUSED_PARAMETER(pFile);
return SQLITE_IOCAP_ATOMIC |
SQLITE_IOCAP_POWERSAFE_OVERWRITE |
SQLITE_IOCAP_SAFE_APPEND |
@@ -307,20 +469,26 @@ static int memdbFetch(
int iAmt,
void **pp
){
- MemFile *p = (MemFile *)pFile;
+ MemStore *p = ((MemFile*)pFile)->pStore;
+ memdbEnter(p);
if( iOfst+iAmt>p->sz ){
*pp = 0;
}else{
p->nMmap++;
*pp = (void*)(p->aData + iOfst);
}
+ memdbLeave(p);
return SQLITE_OK;
}
/* Release a memory-mapped page */
static int memdbUnfetch(sqlite3_file *pFile, sqlite3_int64 iOfst, void *pPage){
- MemFile *p = (MemFile *)pFile;
+ MemStore *p = ((MemFile*)pFile)->pStore;
+ UNUSED_PARAMETER(iOfst);
+ UNUSED_PARAMETER(pPage);
+ memdbEnter(p);
p->nMmap--;
+ memdbLeave(p);
return SQLITE_OK;
}
@@ -330,20 +498,79 @@ static int memdbUnfetch(sqlite3_file *pFile, sqlite3_int64 iOfst, void *pPage){
static int memdbOpen(
sqlite3_vfs *pVfs,
const char *zName,
- sqlite3_file *pFile,
+ sqlite3_file *pFd,
int flags,
int *pOutFlags
){
- MemFile *p = (MemFile*)pFile;
+ MemFile *pFile = (MemFile*)pFd;
+ MemStore *p = 0;
+ int szName;
if( (flags & SQLITE_OPEN_MAIN_DB)==0 ){
- return ORIGVFS(pVfs)->xOpen(ORIGVFS(pVfs), zName, pFile, flags, pOutFlags);
+ return ORIGVFS(pVfs)->xOpen(ORIGVFS(pVfs), zName, pFd, flags, pOutFlags);
}
- memset(p, 0, sizeof(*p));
- p->mFlags = SQLITE_DESERIALIZE_RESIZEABLE | SQLITE_DESERIALIZE_FREEONCLOSE;
+ memset(pFile, 0, sizeof(*p));
+ szName = sqlite3Strlen30(zName);
+ if( szName>1 && zName[0]=='/' ){
+ int i;
+#ifndef SQLITE_MUTEX_OMIT
+ sqlite3_mutex *pVfsMutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1);
+#endif
+ sqlite3_mutex_enter(pVfsMutex);
+ for(i=0; i<memdb_g.nMemStore; i++){
+ if( strcmp(memdb_g.apMemStore[i]->zFName,zName)==0 ){
+ p = memdb_g.apMemStore[i];
+ break;
+ }
+ }
+ if( p==0 ){
+ MemStore **apNew;
+ p = sqlite3Malloc( sizeof(*p) + szName + 3 );
+ if( p==0 ){
+ sqlite3_mutex_leave(pVfsMutex);
+ return SQLITE_NOMEM;
+ }
+ apNew = sqlite3Realloc(memdb_g.apMemStore,
+ sizeof(apNew[0])*(memdb_g.nMemStore+1) );
+ if( apNew==0 ){
+ sqlite3_free(p);
+ sqlite3_mutex_leave(pVfsMutex);
+ return SQLITE_NOMEM;
+ }
+ apNew[memdb_g.nMemStore++] = p;
+ memdb_g.apMemStore = apNew;
+ memset(p, 0, sizeof(*p));
+ p->mFlags = SQLITE_DESERIALIZE_RESIZEABLE|SQLITE_DESERIALIZE_FREEONCLOSE;
+ p->szMax = sqlite3GlobalConfig.mxMemdbSize;
+ p->zFName = (char*)&p[1];
+ memcpy(p->zFName, zName, szName+1);
+ p->pMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+ if( p->pMutex==0 ){
+ memdb_g.nMemStore--;
+ sqlite3_free(p);
+ sqlite3_mutex_leave(pVfsMutex);
+ return SQLITE_NOMEM;
+ }
+ p->nRef = 1;
+ memdbEnter(p);
+ }else{
+ memdbEnter(p);
+ p->nRef++;
+ }
+ sqlite3_mutex_leave(pVfsMutex);
+ }else{
+ p = sqlite3Malloc( sizeof(*p) );
+ if( p==0 ){
+ return SQLITE_NOMEM;
+ }
+ memset(p, 0, sizeof(*p));
+ p->mFlags = SQLITE_DESERIALIZE_RESIZEABLE | SQLITE_DESERIALIZE_FREEONCLOSE;
+ p->szMax = sqlite3GlobalConfig.mxMemdbSize;
+ }
+ pFile->pStore = p;
assert( pOutFlags!=0 ); /* True because flags==SQLITE_OPEN_MAIN_DB */
*pOutFlags = flags | SQLITE_OPEN_MEMORY;
- pFile->pMethods = &memdb_io_methods;
- p->szMax = sqlite3GlobalConfig.mxMemdbSize;
+ pFd->pMethods = &memdb_io_methods;
+ memdbLeave(p);
return SQLITE_OK;
}
@@ -371,6 +598,9 @@ static int memdbAccess(
int flags,
int *pResOut
){
+ UNUSED_PARAMETER(pVfs);
+ UNUSED_PARAMETER(zPath);
+ UNUSED_PARAMETER(flags);
*pResOut = 0;
return SQLITE_OK;
}
@@ -386,6 +616,7 @@ static int memdbFullPathname(
int nOut,
char *zOut
){
+ UNUSED_PARAMETER(pVfs);
sqlite3_snprintf(nOut, zOut, "%s", zPath);
return SQLITE_OK;
}
@@ -458,9 +689,14 @@ static int memdbCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *p){
*/
static MemFile *memdbFromDbSchema(sqlite3 *db, const char *zSchema){
MemFile *p = 0;
+ MemStore *pStore;
int rc = sqlite3_file_control(db, zSchema, SQLITE_FCNTL_FILE_POINTER, &p);
if( rc ) return 0;
if( p->base.pMethods!=&memdb_io_methods ) return 0;
+ pStore = p->pStore;
+ memdbEnter(pStore);
+ if( pStore->zFName!=0 ) p = 0;
+ memdbLeave(pStore);
return p;
}
@@ -496,12 +732,14 @@ unsigned char *sqlite3_serialize(
if( piSize ) *piSize = -1;
if( iDb<0 ) return 0;
if( p ){
- if( piSize ) *piSize = p->sz;
+ MemStore *pStore = p->pStore;
+ assert( pStore->pMutex==0 );
+ if( piSize ) *piSize = pStore->sz;
if( mFlags & SQLITE_SERIALIZE_NOCOPY ){
- pOut = p->aData;
+ pOut = pStore->aData;
}else{
- pOut = sqlite3_malloc64( p->sz );
- if( pOut ) memcpy(pOut, p->aData, p->sz);
+ pOut = sqlite3_malloc64( pStore->sz );
+ if( pOut ) memcpy(pOut, pStore->aData, pStore->sz);
}
return pOut;
}
@@ -595,15 +833,16 @@ int sqlite3_deserialize(
if( p==0 ){
rc = SQLITE_ERROR;
}else{
- p->aData = pData;
+ MemStore *pStore = p->pStore;
+ pStore->aData = pData;
pData = 0;
- p->sz = szDb;
- p->szAlloc = szBuf;
- p->szMax = szBuf;
- if( p->szMax<sqlite3GlobalConfig.mxMemdbSize ){
- p->szMax = sqlite3GlobalConfig.mxMemdbSize;
+ pStore->sz = szDb;
+ pStore->szAlloc = szBuf;
+ pStore->szMax = szBuf;
+ if( pStore->szMax<sqlite3GlobalConfig.mxMemdbSize ){
+ pStore->szMax = sqlite3GlobalConfig.mxMemdbSize;
}
- p->mFlags = mFlags;
+ pStore->mFlags = mFlags;
rc = SQLITE_OK;
}
@@ -622,7 +861,7 @@ end_deserialize:
*/
int sqlite3MemdbInit(void){
sqlite3_vfs *pLower = sqlite3_vfs_find(0);
- int sz = pLower->szOsFile;
+ unsigned int sz = pLower->szOsFile;
memdb_vfs.pAppData = pLower;
/* The following conditional can only be true when compiled for
** Windows x86 and SQLITE_MAX_MMAP_SIZE=0. We always leave
@@ -632,4 +871,4 @@ int sqlite3MemdbInit(void){
memdb_vfs.szOsFile = sz;
return sqlite3_vfs_register(&memdb_vfs, 0);
}
-#endif /* SQLITE_ENABLE_DESERIALIZE */
+#endif /* SQLITE_OMIT_DESERIALIZE */
generated by cgit v1.2.3 (git 2.25.1) at 2025-07-21 20:02:31 +0000