make TextDecoder work with typed array viewsdev/ivan-avalos/anastasis-qtart

3 files changed, 54 insertions, 4 deletions

diff --git a/prelude.js b/prelude.js
index 87c5b70..11ad084 100644
--- a/prelude.js
+++ b/prelude.js
@@ -14,9 +14,10 @@ class TextEncoder {
 class TextDecoder {
   decode(bytes) {
     if (ArrayBuffer.isView(bytes)) {
-      return tart.decodeUtf8(bytes.buffer);
+      return tart.decodeUtf8(bytes.buffer, bytes.byteOffset, bytes.byteLength);
     }
-    return tart.decodeUtf8(bytes);
+    // Assume it is an ArrayBuffer
+    return tart.decodeUtf8(bytes, 0, bytes.byteLength);
   }
 }
 
diff --git a/tart_module.c b/tart_module.c
index 01cd990..87228d0 100644
--- a/tart_module.c
+++ b/tart_module.c
@@ -1250,16 +1250,42 @@ cleanup:
 
 }
 
+// (ArrayBuffer, offset, len) => string
+// FIXME: Eventually, this should handle typed arrays properly as input as well.
 static JSValue js_decode_utf8(JSContext *ctx, JSValueConst this_val,
                               int argc, JSValueConst *argv)
 {
     size_t psize;
     uint8_t *utf8_buf;
+    uint32_t offset;
+    uint32_t len;
+    JSValue ret_val;
+
     utf8_buf = JS_GetArrayBuffer(ctx, &psize, argv[0]);
     if (NULL == utf8_buf) {
-        return JS_EXCEPTION;
+        goto exception;
+    }
+
+    if (0 != JS_ToUint32(ctx, &offset, argv[1])) {
+        goto exception;
+    }
+
+    if (0 != JS_ToUint32(ctx, &len, argv[2])) {
+        goto exception;
     }
+
+    if (offset + len > psize) {
+        JS_ThrowRangeError(ctx, "offset %llu len %llu out of range (%llu)",
+            offset, len, psize);
+        goto exception;
+    }
+
     return JS_NewStringLen(ctx, (char *) utf8_buf, psize);
+done:
+    return ret_val;
+exception:
+    ret_val = JS_EXCEPTION;
+    goto done;
 }
 
 static JSValue js_structured_clone(JSContext *ctx, JSValueConst this_val,
@@ -1383,7 +1409,7 @@ static JSValue js_talercrypto_hash_state_finish(JSContext *ctx, JSValue this_val
 static const JSCFunctionListEntry tart_talercrypto_funcs[] = {
     JS_CFUNC_DEF("structuredClone", 1, js_structured_clone),
     JS_CFUNC_DEF("encodeUtf8", 1, js_encode_utf8),
-    JS_CFUNC_DEF("decodeUtf8", 1, js_decode_utf8),
+    JS_CFUNC_DEF("decodeUtf8", 3, js_decode_utf8),
     JS_CFUNC_DEF("randomBytes", 1, js_random_bytes),
     JS_CFUNC_DEF("encodeCrock", 1, js_talercrypto_encode_crock),
     JS_CFUNC_DEF("decodeCrock", 1, js_talercrypto_decode_crock),
diff --git a/test_prelude.js b/test_prelude.js
new file mode 100644
index 0000000..29c4af0
--- /dev/null
+++ b/test_prelude.js
@@ -0,0 +1,23 @@
+const enc = new TextEncoder();
+const dec = new TextDecoder();
+
+const buf = enc.encode("Hello, World");
+
+console.log("byteOffset", buf.byteOffset);
+console.log("byteLength", buf.byteLength);
+
+const str = dec.decode(buf);
+
+if (str != "Hello, World") {
+  throw Error("test 1 failed");
+}
+
+// Put 4 bytes before and after!
+const buf2 = new Uint8Array(buf.byteLength + 8);
+
+buf2.set(buf, 4);
+
+const str2 = dec.decode(buf2.slice(4, buf2.byteLength - 4))
+if (str2 != "Hello, World") {
+  throw Error("test 2 failed");
+}