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Improved comments in os_kv.c. Better names for the key/value name spaces.

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FossilOrigin-Name: 8e1652a3856765c9146cc2a7e3b598a2dc7dc84c556b35eab9a35184514384b9
This commit is contained in:
drh
2022-09-10 18:38:21 +00:00
parent 7585f49a0a
commit c6c9c6aad0
3 changed files with 33 additions and 29 deletions
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48
src/os_kv.c
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@@ -165,26 +165,28 @@ static sqlite3_io_methods kvvfs_jrnl_io_methods = {
/* Forward declarations for the low-level storage engine
*/
#define KVSTORAGE_KEY_SZ 24
#define KVSTORAGE_KEY_PREFIX "kvvfs-"
#define KVSTORAGE_KEY_SZ 32
static int kvstorageWrite(const char*, const char *zKey, const char *zData);
static int kvstorageDelete(const char*, const char *zKey);
static int kvstorageRead(const char*, const char *zKey, char *zBuf, int nBuf);
/* Expand the key name with an appropriate prefix and put the result
** in pStore->zKey[]
** zKeyOut[]. The zKeyOut[] buffer is assumed to hold at least
** KVSTORAGE_KEY_SZ bytes.
*/
static void kvstorageMakeKey(
const char *zClass,
const char *zKeyIn,
char *zKeyOut
){
sqlite3_snprintf(KVSTORAGE_KEY_SZ, zKeyOut, "%s-%s", zClass, zKeyIn);
sqlite3_snprintf(KVSTORAGE_KEY_SZ, zKeyOut, "kvvfs-%s-%s", zClass, zKeyIn);
}
/* Write content into a key. zKey is of limited size. zData should be
** pure text. In other words, zData has already been encoded.
/* Write content into a key. zClass is the particular namespace of the
** underlying key/value store to use - either "local" or "session".
**
** Both zKey and zData are zero-terminated pure text strings.
**
** Return the number of errors.
*/
@@ -209,7 +211,9 @@ static int kvstorageWrite(
}
}
/* Delete a key
/* Delete a key (with its corresponding data) from the key/value
** namespace given by zClass. If the key does not previously exist,
** this routine is a no-op.
*/
static int kvstorageDelete(const char *zClass, const char *zKey){
char zXKey[KVSTORAGE_KEY_SZ];
@@ -219,16 +223,17 @@ static int kvstorageDelete(const char *zClass, const char *zKey){
return 0;
}
/* Read the value associated with a key and put the result in the first
/* Read the value associated with a zKey from the key/value namespace given
** by zClass and put the text data associated with that key in the first
** nBuf bytes of zBuf[]. The value might be truncated if zBuf is not large
** enough to hold it all. The value put into zBuf will always be zero
** terminated.
** enough to hold it all. The value put into zBuf must always be zero
** terminated, even if it gets truncated because nBuf is not large enough.
**
** Return the total number of bytes in the data, without truncation, and
** not counting the final zero terminator. Return -1 if the key does
** not exist.
**
** If nBuf==0 then this routine simply returns the size of the data without
** If nBuf<=0 then this routine simply returns the size of the data without
** actually reading it.
*/
static int kvstorageRead(
@@ -248,7 +253,7 @@ static int kvstorageRead(
SQLITE_KV_TRACE(("KVVFS-READ %-15s (-1)\n", zXKey));
return -1;
}
if( nBuf<0 ){
if( nBuf<=0 ){
return (int)buf.st_size;
}else if( nBuf==1 ){
zBuf[0] = 0;
@@ -275,7 +280,6 @@ static int kvstorageRead(
/****** Utility subroutines ************************************************/
/*
** Encode binary into the text encoded used to persist on disk.
** The output text is stored in aOut[], which must be at least
@@ -446,7 +450,7 @@ static int kvvfsReadJrnl(
assert( pFile->isJournal );
SQLITE_KV_LOG(("xRead('%s-journal',%d,%lld)\n", pFile->zClass, iAmt, iOfst));
if( pFile->aJrnl==0 ){
int szTxt = kvstorageRead(pFile->zClass, "jrnl", 0, -1);
int szTxt = kvstorageRead(pFile->zClass, "jrnl", 0, 0);
char *aTxt;
if( szTxt<=4 ){
return SQLITE_IOERR;
@@ -752,9 +756,9 @@ static int kvvfsOpen(
return SQLITE_CANTOPEN;
}
if( zName[0]=='s' ){
pFile->zClass = KVSTORAGE_KEY_PREFIX "ses";
pFile->zClass = "session";
}else{
pFile->zClass = KVSTORAGE_KEY_PREFIX "loc";
pFile->zClass = "local";
}
pFile->aJrnl = 0;
pFile->nJrnl = 0;
@@ -770,10 +774,10 @@ static int kvvfsOpen(
*/
static int kvvfsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
if( strcmp(zPath, "local-journal")==0 ){
kvstorageDelete(KVSTORAGE_KEY_PREFIX "loc", "jrnl");
kvstorageDelete("local", "jrnl");
}else
if( strcmp(zPath, "session-journal")==0 ){
kvstorageDelete(KVSTORAGE_KEY_PREFIX "ses", "jrnl");
kvstorageDelete("session", "jrnl");
}
return SQLITE_OK;
}
@@ -790,16 +794,16 @@ static int kvvfsAccess(
){
SQLITE_KV_LOG(("xAccess(\"%s\")\n", zPath));
if( strcmp(zPath, "local-journal")==0 ){
*pResOut = kvstorageRead(KVSTORAGE_KEY_PREFIX "loc", "jrnl", 0, -1)>0;
*pResOut = kvstorageRead("local", "jrnl", 0, 0)>0;
}else
if( strcmp(zPath, "session-journal")==0 ){
*pResOut = kvstorageRead(KVSTORAGE_KEY_PREFIX "ses", "jrnl", 0, -1)>0;
*pResOut = kvstorageRead("session", "jrnl", 0, 0)>0;
}else
if( strcmp(zPath, "local")==0 ){
*pResOut = kvstorageRead(KVSTORAGE_KEY_PREFIX "loc", "sz", 0, -1)>0;
*pResOut = kvstorageRead("local", "sz", 0, 0)>0;
}else
if( strcmp(zPath, "session")==0 ){
*pResOut = kvstorageRead(KVSTORAGE_KEY_PREFIX "ses", "sz", 0, -1)>0;
*pResOut = kvstorageRead("session", "sz", 0, 0)>0;
}else
{
*pResOut = 0;