Add a setting option -s TEXTDECODER=0/1 which can be used to control whether the TextDecoder API is used or not. Enabled by default.

Author: juj

src/preamble.js

@@ -515,8 +515,11 @@ function stringToAscii(str, outPtr) {
 // Given a pointer 'ptr' to a null-terminated UTF8-encoded string in the given array that contains uint8 values, returns
 // a copy of that string as a Javascript String object.
 
+#if TEXTDECODER
 var UTF8Decoder = typeof TextDecoder !== 'undefined' ? new TextDecoder('utf8') : undefined;
+#endif
 function UTF8ArrayToString(u8Array, idx) {
+#if TEXTDECODER
   var endPtr = idx;
   // TextDecoder needs to know the byte length in advance, it doesn't stop on null terminator by itself.
   // Also, use the length info to avoid running tiny strings through TextDecoder, since .subarray() allocates garbage.
@@ -525,6 +528,7 @@ function UTF8ArrayToString(u8Array, idx) {
   if (endPtr - idx > 16 && u8Array.subarray && UTF8Decoder) {
     return UTF8Decoder.decode(u8Array.subarray(idx, endPtr));
   } else {
+#endif
     var u0, u1, u2, u3, u4, u5;
 
     var str = '';
@@ -559,7 +563,9 @@ function UTF8ArrayToString(u8Array, idx) {
         str += String.fromCharCode(0xD800 | (ch >> 10), 0xDC00 | (ch & 0x3FF));
       }
     }
+#if TEXTDECODER
   }
+#endif
 }
 {{{ maybeExport('UTF8ArrayToString') }}}
 
@@ -684,6 +690,7 @@ function UTF16ToString(ptr) {
 #if ASSERTIONS
   assert(ptr % 2 == 0, 'Pointer passed to UTF16ToString must be aligned to two bytes!');
 #endif
+#if TEXTDECODER
   var endPtr = ptr;
   // TextDecoder needs to know the byte length in advance, it doesn't stop on null terminator by itself.
   // Also, use the length info to avoid running tiny strings through TextDecoder, since .subarray() allocates garbage.
@@ -694,6 +701,7 @@ function UTF16ToString(ptr) {
   if (endPtr - ptr > 32 && UTF16Decoder) {
     return UTF16Decoder.decode(HEAPU8.subarray(ptr, endPtr));
   } else {
+#endif
     var i = 0;
 
     var str = '';
@@ -704,7 +712,9 @@ function UTF16ToString(ptr) {
       // fromCharCode constructs a character from a UTF-16 code unit, so we can pass the UTF16 string right through.
       str += String.fromCharCode(codeUnit);
     }
+#if TEXTDECODER
   }
+#endif
 }
 {{{ maybeExport('UTF16ToString') }}}
 

src/settings.js

@@ -754,4 +754,6 @@ var CYBERDWARF = 0; // see http://kripken.github.io/emscripten-site/docs/debuggi
 
 var BUNDLED_CD_DEBUG_FILE = ""; // Path to the CyberDWARF debug file passed to the compiler
 
+var TEXTDECODER = 1; // Is enabled, use the JavaScript TextDecoder API for string marshalling.
+                     // Enabled by default, set this to 0 to disable.
 // Reserved: variables containing POINTER_MASKING.