string_decoder: reset decoder on end

This resets the StringDecoder's state after calling `#end`. Further writes to the decoder will act as if it were a brand new instance, allowing simple reuse. PR-URL: #18494Fixes: #16564 Refs: #16594 Reviewed-By: Tiancheng "Timothy" Gu <[email protected]> Reviewed-By: Sakthipriyan Vairamani <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Anna Henningsen <[email protected]>

Author: jridgewell

lib/string_decoder.js

@@ -210,8 +210,11 @@ function utf8Text(buf, i){
 // character.
 functionutf8End(buf){
 constr=(buf&&buf.length ? this.write(buf) : '');
-if(this.lastNeed)
+if(this.lastNeed){
+this.lastNeed=0;
+this.lastTotal=0;
 returnr+'\ufffd';
+}
 returnr;
 }
 
@@ -246,6 +249,8 @@ function utf16End(buf){
 constr=(buf&&buf.length ? this.write(buf) : '');
 if(this.lastNeed){
 constend=this.lastTotal-this.lastNeed;
+this.lastNeed=0;
+this.lastTotal=0;
 returnr+this.lastChar.toString('utf16le',0,end);
 }
 returnr;
@@ -269,8 +274,12 @@ function base64Text(buf, i){
 
 functionbase64End(buf){
 constr=(buf&&buf.length ? this.write(buf) : '');
-if(this.lastNeed)
-returnr+this.lastChar.toString('base64',0,3-this.lastNeed);
+if(this.lastNeed){
+constend=3-this.lastNeed;
+this.lastNeed=0;
+this.lastTotal=0;
+returnr+this.lastChar.toString('base64',0,end);
+}
 returnr;
 }
 

test/parallel/test-string-decoder-end.js

@@ -39,6 +39,46 @@ for (let i = 1; i <= 16; i++){
 
 encodings.forEach(testEncoding);
 
+testEnd('utf8',Buffer.of(0xE2),Buffer.of(0x61),'\uFFFDa');
+testEnd('utf8',Buffer.of(0xE2),Buffer.of(0x82),'\uFFFD\uFFFD');
+testEnd('utf8',Buffer.of(0xE2),Buffer.of(0xE2),'\uFFFD\uFFFD');
+testEnd('utf8',Buffer.of(0xE2,0x82),Buffer.of(0x61),'\uFFFDa');
+testEnd('utf8',Buffer.of(0xE2,0x82),Buffer.of(0xAC),'\uFFFD\uFFFD');
+testEnd('utf8',Buffer.of(0xE2,0x82),Buffer.of(0xE2),'\uFFFD\uFFFD');
+testEnd('utf8',Buffer.of(0xE2,0x82,0xAC),Buffer.of(0x61),'€a');
+
+testEnd('utf16le',Buffer.of(0x3D),Buffer.of(0x61,0x00),'a');
+testEnd('utf16le',Buffer.of(0x3D),Buffer.of(0xD8,0x4D,0xDC),'\u4DD8');
+testEnd('utf16le',Buffer.of(0x3D,0xD8),Buffer.of(),'\uD83D');
+testEnd('utf16le',Buffer.of(0x3D,0xD8),Buffer.of(0x61,0x00),'\uD83Da');
+testEnd(
+'utf16le',
+Buffer.of(0x3D,0xD8),
+Buffer.of(0x4D,0xDC),
+'\uD83D\uDC4D'
+);
+testEnd('utf16le',Buffer.of(0x3D,0xD8,0x4D),Buffer.of(),'\uD83D');
+testEnd(
+'utf16le',
+Buffer.of(0x3D,0xD8,0x4D),
+Buffer.of(0x61,0x00),
+'\uD83Da'
+);
+testEnd('utf16le',Buffer.of(0x3D,0xD8,0x4D),Buffer.of(0xDC),'\uD83D');
+testEnd(
+'utf16le',
+Buffer.of(0x3D,0xD8,0x4D,0xDC),
+Buffer.of(0x61,0x00),
+'👍a'
+);
+
+testEnd('base64',Buffer.of(0x61),Buffer.of(),'YQ==');
+testEnd('base64',Buffer.of(0x61),Buffer.of(0x61),'YQ==YQ==');
+testEnd('base64',Buffer.of(0x61,0x61),Buffer.of(),'YWE=');
+testEnd('base64',Buffer.of(0x61,0x61),Buffer.of(0x61),'YWE=YQ==');
+testEnd('base64',Buffer.of(0x61,0x61,0x61),Buffer.of(),'YWFh');
+testEnd('base64',Buffer.of(0x61,0x61,0x61),Buffer.of(0x61),'YWFhYQ==');
+
 functiontestEncoding(encoding){
 bufs.forEach((buf)=>{
 testBuf(encoding,buf);
@@ -66,3 +106,14 @@ function testBuf(encoding, buf){
 assert.strictEqual(res1,res3,'one byte at a time should match toString');
 assert.strictEqual(res2,res3,'all bytes at once should match toString');
 }
+
+functiontestEnd(encoding,incomplete,next,expected){
+letres='';
+consts=newSD(encoding);
+res+=s.write(incomplete);
+res+=s.end();
+res+=s.write(next);
+res+=s.end();
+
+assert.strictEqual(res,expected);
+}