diff --git a/lib/buffer.js b/lib/buffer.js index afe5677b348df5..4b1f2288e35802 100644 --- a/lib/buffer.js +++ b/lib/buffer.js @@ -499,6 +499,15 @@ Buffer.concat = function(list, length) { buf.copy(buffer, pos); pos += buf.length; } + + // Note: `length` is always equal to `buffer.length` at this point + if (pos < length) { + // Zero-fill the remaining bytes if the specified `length` was more than + // the actual total length, i.e. if we have some remaining allocated bytes + // there were not initialized. + buffer.fill(0, pos, length); + } + return buffer; }; diff --git a/test/simple/test-buffer-concat.js b/test/simple/test-buffer-concat.js index 858d6924f95fac..ef5a56206635ef 100644 --- a/test/simple/test-buffer-concat.js +++ b/test/simple/test-buffer-concat.js @@ -38,4 +38,30 @@ assert(flatOne === one[0]); assert(flatLong.toString() === (new Array(10+1).join('asdf'))); assert(flatLongLen.toString() === (new Array(10+1).join('asdf'))); +var ones = new Buffer(10); +ones.fill('1'); +var empty = new Buffer(0); + +var short = ones.slice(5); // needed for 0.10.x, can't start past the length + +assert.equal(Buffer.concat([], 100).toString(), ''); +assert.equal(Buffer.concat([ones], 0).toString(), ones.toString()); // 0.10.x +assert.equal(Buffer.concat([ones], 10).toString(), ones.toString()); +assert.equal(Buffer.concat([short, ones], 10).toString(), ones.toString()); +assert.equal(Buffer.concat([empty, ones]).toString(), ones.toString()); +assert.equal(Buffer.concat([ones, empty, empty]).toString(), ones.toString()); + +var zeros100 = new Buffer(100); +zeros100.fill(0); +var zeros30 = new Buffer(30); +zeros30.fill(0); + +// The tail should be zero-filled +assert.equal( + Buffer.concat([empty, empty], 100).toString(), + zeros100.toString()); +assert.equal( + Buffer.concat([empty, ones], 40).toString(), + Buffer.concat([ones, zeros30]).toString()); + console.log("ok");