Buffer#toString throw on unsupported encodings

src-input/duk_bi_buffer.c

@@ -1183,6 +1183,7 @@ DUK_INTERNAL duk_ret_t duk_bi_uint8array_plainof(duk_hthread *thr) {
 
 #if defined(DUK_USE_BUFFEROBJECT_SUPPORT)
 DUK_INTERNAL duk_ret_t duk_bi_nodejs_buffer_tostring(duk_hthread *thr) {
+	const char* encoding;
 	duk_hbufobj *h_this;
 	duk_int_t start_offset, end_offset;
 	duk_uint8_t *buf_slice;
@@ -1196,7 +1197,18 @@ DUK_INTERNAL duk_ret_t duk_bi_nodejs_buffer_tostring(duk_hthread *thr) {
 	}
 	DUK_HBUFOBJ_ASSERT_VALID(h_this);
 
-	/* Ignore encoding for now. */
+	/* TODO: support other encodings.  currently only 'utf8' is supported. */
+	if (duk_is_undefined(thr, 0)) {
+		encoding = "utf8";
+	} else if (duk_is_string(thr, 0)) {
+		encoding = duk_to_string(thr, 0);
+		DUK_ASSERT(duk_is_string(thr, 0));
+		if(DUK_STRCMP(encoding, "utf8") != 0) {
+			DUK_DCERROR_TYPE_INVALID_ARGS(thr);
+		}
+	} else {
+		DUK_DCERROR_TYPE_INVALID_ARGS(thr);
+	}
 
 	duk__clamp_startend_nonegidx_noshift(thr,
 	                                     (duk_int_t) h_this->length,

tests/ecmascript/test-bi-nodejs-buffer-tostring.js

@@ -23,7 +23,6 @@ false
 true
 "ABC"
 "ABC"
-"ABC"
 "DEFG"
 "EFG"
 "E"
@@ -241,20 +240,21 @@ function nodejsBufferToStringTest() {
     // buf.toString([encoding], [start], [end])
 
     // Without arguments encoding defaults to UTF-8 and the entire
-    // buffer is converted to string.  At least undefined and null
+    // buffer is converted to string.  At least undefined is 
     // are accepted as "not defined" for encoding.
     b = new Buffer('ABC');
     safePrintString(b.toString());
     safePrintString(b.toString(undefined));
-    safePrintString(b.toString(null));
+    // null is not a valid encoding
+    try { safePrintString(b.toString(null)); } catch(e) { }
 
     // If the buffer is a slice of an underlying buffer, only that slice
     // is string converted.  Offsets are relative to the slice.
     b = new Buffer('ABCDEFGH');
     b = b.slice(3, 7);  // DEFG
     safePrintString(b.toString());
-    safePrintString(b.toString(null, 1));
-    safePrintString(b.toString(null, 1, 2));
+    safePrintString(b.toString(undefined, 1));
+    safePrintString(b.toString(undefined, 1, 2));
 
     // When the buffer data is legal UTF-8 and the chosen encoding
     // is UTF-8 (default), Duktape internal representation is correct