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Minor cleanups and docs for the EM_JS() impls of the kvvfs read/write/delete ops.

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FossilOrigin-Name: 53b7572e441be4b4b29b4228d0f95b24457d7faaf6c0b568ed5c970a55e21ffb
This commit is contained in:
stephan
2022-09-11 05:38:39 +00:00
parent e99f742a32
commit ade4f4d645
3 changed files with 51 additions and 20 deletions
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57
ext/wasm/api/sqlite3-wasm.c
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@ -503,7 +503,7 @@ static void kvstorageMakeKey(
** An internal level of indirection for accessing the static
** kvstorageMakeKey() from EM_JS()-generated functions. This must be
** made available for export via Emscripten but is not intended to be
** used from client code. If called with a NULL zClass it is a no-op.
** used from client code. If called with a NULL zKeyOut it is a no-op.
** It returns KVSTORAGE_KEY_SZ, so JS code (which cannot see that
** constant) may call it with NULL arguments to get the size of the
** allocation they'll need for a kvvfs key.
@ -514,7 +514,7 @@ static void kvstorageMakeKey(
int sqlite3_wasm__kvvfsMakeKey(const char *zClass,
const char *zKeyIn,
char *zKeyOut){
if(zClass) kvstorageMakeKey(zClass, zKeyIn, zKeyOut);
if(zKeyOut) kvstorageMakeKey(zClass, zKeyIn, zKeyOut);
return KVSTORAGE_KEY_SZ;
}
@ -559,14 +559,33 @@ EM_JS(void, kvstorageMakeKeyJS,
});
#endif
/*
** Internal helper for kvstorageWrite/Read/Delete() which creates a
** storage key for the given zClass/zKeyIn combination. Returns a
** pointer to the key: a C string allocated on the WASM stack, or 0 if
** allocation fails. It is up to the caller to save/restore the stack
** before/after this operation.
*/
EM_JS(const char *, kvstorageMakeKeyOnJSStack,
(const char *zClass, const char *zKeyIn),{
if( 0==zClass || 0==zKeyIn) return 0;
const zXKey = stackAlloc(_sqlite3_wasm__kvvfsMakeKey(0,0,0));
if(zXKey) _sqlite3_wasm__kvvfsMakeKey(zClass, zKeyIn, zXKey);
return zXKey;
});
/*
** JS impl of kvstorageWrite(). Main docs are in the C impl. This impl
** writes zData to the global sessionStorage (if zClass starts with
** 's') or localStorage, using a storage key derived from zClass and
** zKey.
*/
EM_JS(int, kvstorageWrite,
(const char *zClass, const char *zKey, const char *zData),{
const stack = stackSave();
try {
//const zXKey = stackAlloc(kvstorageMakeKeyJS());
//kvstorageMakeKeyJS(zClass, zKey, zXKey);
const zXKey = stackAlloc(_sqlite3_wasm__kvvfsMakeKey(0,0,0));
_sqlite3_wasm__kvvfsMakeKey(zClass, zKey, zXKey);
const zXKey = kvstorageMakeKeyOnJSStack(zClass,zKey);
if(!zXKey) return 1/*OOM*/;
const jKey = UTF8ToString(zXKey);
/**
We could simplify this function and eliminate the
@ -586,11 +605,18 @@ EM_JS(int, kvstorageWrite,
return 0;
});
/*
** JS impl of kvstorageDelete(). Main docs are in the C impl. This
** impl generates a key derived from zClass and zKey, and removes the
** matching entry (if any) from global sessionStorage (if zClass
** starts with 's') or localStorage.
*/
EM_JS(int, kvstorageDelete,
(const char *zClass, const char *zKey),{
const stack = stackSave();
try {
const zXKey = stackAlloc(_sqlite3_wasm__kvvfsMakeKey(0,0,0));
const zXKey = kvstorageMakeKeyOnJSStack(zClass,zKey);
if(!zXKey) return 1/*OOM*/;
_sqlite3_wasm__kvvfsMakeKey(zClass, zKey, zXKey);
const jKey = UTF8ToString(zXKey);
((115/*=='s'*/===getValue(zClass))
@ -604,16 +630,21 @@ EM_JS(int, kvstorageDelete,
return 0;
});
/*
** JS impl of kvstorageRead(). Main docs are in the C impl. This impl
** reads its data from the global sessionStorage (if zClass starts
** with 's') or localStorage, using a storage key derived from zClass
** and zKey.
*/
EM_JS(int, kvstorageRead,
(const char *zClass, const char *zKey, char *zBuf, int nBuf),{
const stack = stackSave();
try {
const zXKey = stackAlloc(_sqlite3_wasm__kvvfsMakeKey(0,0,0));
_sqlite3_wasm__kvvfsMakeKey(zClass, zKey, zXKey);
const zXKey = kvstorageMakeKeyOnJSStack(zClass,zKey);
if(!zXKey) return 1/*OOM*/;
const jKey = UTF8ToString(zXKey);
const storage = (115/*=='s'*/===getValue(zClass))
? sessionStorage : localStorage;
const jV = storage.getItem(jKey);
const jV = ((115/*=='s'*/===getValue(zClass))
? sessionStorage : localStorage).getItem(jKey);
if(!jV) return -1;
const nV = jV.length /* Note that we are relying 100% on v being
ASCII so that jV.length is equal to the
@ -661,7 +692,7 @@ int sqlite3_wasm__emjs_test(int whichOp){
kvstorageDelete(zClass, zKey);
break;
default:
//kvstorageMakeKeyJS(0,0,0) /* force Emscripten to include this */;
kvstorageMakeKeyOnJSStack(0,0) /* force Emscripten to include this */;
break;
}
return rc;