/*
* Minimal in-memory VFS for SQLite WASM builds using SQLITE_OS_OTHER=1.
*
* Provides sqlite3_os_init() / sqlite3_os_end() which register a bare-minimum
* VFS that supports :memory: databases and temporary files stored in memory.
* No real filesystem access is performed.
*/
#include "sqlite3.h"
#include <string.h>
#include <stdlib.h>
/* ── In-memory file ────────────────────────────────────────────────── */
typedef struct MemFile {
sqlite3_file base;
char *buf;
int sz;
int cap;
} MemFile;
static int memClose(sqlite3_file *pFile) {
MemFile *p = (MemFile *)pFile;
free(p->buf);
p->buf = NULL;
p->sz = 0;
p->cap = 0;
return SQLITE_OK;
}
static int memRead(sqlite3_file *pFile, void *zBuf, int iAmt, sqlite3_int64 iOfst) {
MemFile *p = (MemFile *)pFile;
int avail = p->sz - (int)iOfst;
if (avail <= 0) {
memset(zBuf, 0, iAmt);
return SQLITE_IOERR_SHORT_READ;
}
if (avail < iAmt) {
memcpy(zBuf, p->buf + iOfst, avail);
memset((char *)zBuf + avail, 0, iAmt - avail);
return SQLITE_IOERR_SHORT_READ;
}
memcpy(zBuf, p->buf + iOfst, iAmt);
return SQLITE_OK;
}
static int memWrite(sqlite3_file *pFile, const void *zBuf, int iAmt, sqlite3_int64 iOfst) {
MemFile *p = (MemFile *)pFile;
int needed = (int)iOfst + iAmt;
if (needed > p->cap) {
int newCap = p->cap ? p->cap : 4096;
while (newCap < needed) newCap *= 2;
char *newBuf = (char *)realloc(p->buf, newCap);
if (!newBuf) return SQLITE_NOMEM;
/* Zero the gap between old size and the write offset */
if ((int)iOfst > p->sz) {
memset(newBuf + p->sz, 0, (int)iOfst - p->sz);
}
p->buf = newBuf;
p->cap = newCap;
}
memcpy(p->buf + iOfst, zBuf, iAmt);
if (needed > p->sz) p->sz = needed;
return SQLITE_OK;
}
static int memTruncate(sqlite3_file *pFile, sqlite3_int64 size) {
MemFile *p = (MemFile *)pFile;
if ((int)size < p->sz) p->sz = (int)size;
return SQLITE_OK;
}
static int memSync(sqlite3_file *pFile, int flags) {
(void)pFile; (void)flags;
return SQLITE_OK;
}
static int memFileSize(sqlite3_file *pFile, sqlite3_int64 *pSize) {
*pSize = ((MemFile *)pFile)->sz;
return SQLITE_OK;
}
static int memLock(sqlite3_file *f, int l) { (void)f; (void)l; return SQLITE_OK; }
static int memUnlock(sqlite3_file *f, int l) { (void)f; (void)l; return SQLITE_OK; }
static int memCheckReservedLock(sqlite3_file *f, int *pOut) { (void)f; *pOut = 0; return SQLITE_OK; }
static int memFileControl(sqlite3_file *f, int op, void *a) { (void)f; (void)op; (void)a; return SQLITE_NOTFOUND; }
static int memSectorSize(sqlite3_file *f) { (void)f; return 512; }
static int memDeviceCharacteristics(sqlite3_file *f) { (void)f; return 0; }
static const sqlite3_io_methods memIoMethods = {
1, /* iVersion */
memClose,
memRead,
memWrite,
memTruncate,
memSync,
memFileSize,
memLock,
memUnlock,
memCheckReservedLock,
memFileControl,
memSectorSize,
memDeviceCharacteristics,
};
/* ── VFS methods ───────────────────────────────────────────────────── */
static int memVfsOpen(sqlite3_vfs *pVfs, const char *zName,
sqlite3_file *pFile, int flags, int *pOutFlags) {
(void)pVfs; (void)zName; (void)flags;
MemFile *p = (MemFile *)pFile;
memset(p, 0, sizeof(*p));
p->base.pMethods = &memIoMethods;
if (pOutFlags) *pOutFlags = flags;
return SQLITE_OK;
}
static int memVfsDelete(sqlite3_vfs *v, const char *n, int s) {
(void)v; (void)n; (void)s;
return SQLITE_OK;
}
static int memVfsAccess(sqlite3_vfs *v, const char *zName, int flags, int *pResOut) {
(void)v; (void)zName; (void)flags;
*pResOut = 0; /* file does not exist */
return SQLITE_OK;
}
static int memVfsFullPathname(sqlite3_vfs *v, const char *zIn, int nOut, char *zOut) {
(void)v;
int n = (int)strlen(zIn);
if (n >= nOut) n = nOut - 1;
memcpy(zOut, zIn, n);
zOut[n] = '\0';
return SQLITE_OK;
}
static int memVfsRandomness(sqlite3_vfs *v, int nByte, char *zOut) {
(void)v;
memset(zOut, 0, nByte);
return nByte;
}
static int memVfsSleep(sqlite3_vfs *v, int microseconds) {
(void)v; (void)microseconds;
return 0;
}
static int memVfsCurrentTime(sqlite3_vfs *v, double *pOut) {
(void)v;
*pOut = 2460000.5; /* arbitrary Julian day number */
return SQLITE_OK;
}
static int memVfsGetLastError(sqlite3_vfs *v, int n, char *buf) {
(void)v; (void)n; (void)buf;
return 0;
}
static sqlite3_vfs memVfs = {
1, /* iVersion */
(int)sizeof(MemFile), /* szOsFile */
512, /* mxPathname */
0, /* pNext */
"memvfs", /* zName */
0, /* pAppData */
memVfsOpen,
memVfsDelete,
memVfsAccess,
memVfsFullPathname,
0, 0, 0, 0, /* xDlOpen, xDlError, xDlSym, xDlClose */
memVfsRandomness,
memVfsSleep,
memVfsCurrentTime,
memVfsGetLastError,
};
/* ── OS interface required by SQLITE_OS_OTHER ─────────────────────── */
int sqlite3_os_init(void) {
return sqlite3_vfs_register(&memVfs, 1 /* make default */);
}
int sqlite3_os_end(void) {
return SQLITE_OK;
}
