Layout: provide fix for node issue 3992

The common Buffer.writeInt{L,B}E methods have a bug; if it appears to be present in the running version of node substitute the fixed code. See: nodejs/node#3992
pabigot · Nov 23, 2015 · 1153acb · 1153acb
1 parent 97d7388
commit 1153acb
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diff --git a/lib/Layout.js b/lib/Layout.js
@@ -121,6 +121,79 @@
 
 var assert = require('assert');
 
+/* Determine whether node issue #3992 is fixed, and if not replace the
+ * Buffer functions with ones that work correctly.
+ *
+ * See: https://github.com/nodejs/node/issues/3992 */
+var issue_3992_is_resolved = (function () {
+    var buf = new Buffer(2);
+    buf.writeIntLE(-0x100, 0, 2);
+    return (0xFF === buf[1]);
+})();
+/* NB: Backfill code modified from node lib/buffer.js as of
+ * 8bc80386879538de63cd6f2aef288f59324eb004 (2015-11-20) */
+/* istanbul ignore next */
+function checkInt(buffer, value, offset, ext, max, min) {
+    if (!(buffer instanceof Buffer))
+        throw new TypeError('"buffer" argument must be a Buffer instance');
+    if (value > max || value < min)
+        throw new TypeError('"value" argument is out of bounds');
+    if (offset + ext > buffer.length)
+        throw new RangeError('Index out of range');
+}
+/* The grotesquery here is because jshint whines about strict mode
+ * violations if the function doesn't appear to be a method, and about
+ * defining functions within a block if the test is in an if
+ * statement. */
+Buffer.prototype.writeIntLE = issue_3992_is_resolved ? Buffer.prototype.writeIntLE : function(value, offset, byteLength, noAssert) {
+    value = +value;
+    offset = offset >>> 0;
+    if (!noAssert) {
+        checkInt(this,
+                 value,
+                 offset,
+                 byteLength,
+                 Math.pow(2, 8 * byteLength - 1) - 1,
+                 -Math.pow(2, 8 * byteLength - 1));
+    }
+
+    var i = 0;
+    var mul = 1;
+    var sub = 0;
+    this[offset] = value;
+    while (++i < byteLength && (mul *= 0x100)) {
+        if (value < 0 && sub === 0 && this[offset + i - 1] !== 0)
+            sub = 1;
+        this[offset + i] = ((value / mul) >> 0) - sub;
+    }
+
+    return offset + byteLength;
+};
+Buffer.prototype.writeIntBE = issue_3992_is_resolved ? Buffer.prototype.writeIntBE : function(value, offset, byteLength, noAssert) {
+    value = +value;
+    offset = offset >>> 0;
+    if (!noAssert) {
+        checkInt(this,
+                 value,
+                 offset,
+                 byteLength,
+                 Math.pow(2, 8 * byteLength - 1) - 1,
+                 -Math.pow(2, 8 * byteLength - 1));
+    }
+
+    var i = byteLength - 1;
+    var mul = 1;
+    var sub = 0;
+    this[offset + i] = value;
+    while (--i >= 0 && (mul *= 0x100)) {
+        if (value < 0 && sub === 0 && this[offset + i + 1] !== 0)
+            sub = 1;
+        this[offset + i] = ((value / mul) >> 0) - sub;
+    }
+
+    return offset + byteLength;
+};
+
 /* istanbul ignore next */
 /* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger */
 Number.isInteger = Number.isInteger || function(value) {

diff --git a/test/LayoutTest.js b/test/LayoutTest.js
@@ -3,6 +3,15 @@ var assert = require("assert"),
     lo = require("../lib/Layout");
 
 suite("Layout", function () {
+    suite("Buffer", function () {
+        test("issue 3992", function () {
+            var buf = new Buffer(4);
+            buf.writeIntLE(-0x120000, 0, 4);
+            assert.deepEqual(buf.toJSON().data, [ 0x00, 0x00, 0xee, 0xff ]);
+            buf.writeIntBE(-0x120000, 0, 4);
+            assert.deepEqual(buf.toJSON().data, [ 0xff, 0xee, 0x00, 0x00 ]);
+        });
+    });
     suite("Layout", function () {
         test("anonymous ctor", function () {
             var d = new lo.Layout(8);