buffer: add Buffer.prototype.compare by offset

Adds additional `targetStart`, `targetEnd`, `sourceStart,
and `sourceEnd` arguments to `Buffer.prototype.compare`
to allow comparison of sub-ranges of two Buffers without
requiring Buffer.prototype.slice()

Fixes: https://github.com/nodejs/node/issues/521
PR-URL: https://github.com/nodejs/node/pull/5880
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/test/parallel/test-buffer-compare-offset.js b/test/parallel/test-buffer-compare-offset.js
new file mode 100644
index 0000000000..540d644c28
--- /dev/null
+++ b/test/parallel/test-buffer-compare-offset.js
@@ -0,0 +1,63 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+
+const a = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]);
+const b = Buffer.from([5, 6, 7, 8, 9, 0, 1, 2, 3, 4]);
+
+assert.equal(-1, a.compare(b));
+
+// Equivalent to a.compare(b).
+assert.equal(-1, a.compare(b, 0));
+assert.equal(-1, a.compare(b, '0'));
+
+// Equivalent to a.compare(b).
+assert.equal(-1, a.compare(b, 0, undefined, 0));
+
+// Zero-length targer, return 1
+assert.equal(1, a.compare(b, 0, 0, 0));
+assert.equal(1, a.compare(b, '0', '0', '0'));
+
+// Equivalent to Buffer.compare(a, b.slice(6, 10))
+assert.equal(1, a.compare(b, 6, 10));
+
+// Zero-length source, return -1
+assert.equal(-1, a.compare(b, 6, 10, 0, 0));
+
+// Equivalent to Buffer.compare(a.slice(4), b.slice(0, 5))
+assert.equal(1, a.compare(b, 0, 5, 4));
+
+// Equivalent to Buffer.compare(a.slice(1), b.slice(5))
+assert.equal(1, a.compare(b, 5, undefined, 1));
+
+// Equivalent to Buffer.compare(a.slice(2), b.slice(2, 4))
+assert.equal(-1, a.compare(b, 2, 4, 2));
+
+// Equivalent to Buffer.compare(a.slice(4), b.slice(0, 7))
+assert.equal(-1, a.compare(b, 0, 7, 4));
+
+// Equivalent to Buffer.compare(a.slice(4, 6), b.slice(0, 7));
+assert.equal(-1, a.compare(b, 0, 7, 4, 6));
+
+// zero length target
+assert.equal(1, a.compare(b, 0, null));
+
+// coerces to targetEnd == 5
+assert.equal(-1, a.compare(b, 0, {valueOf: () => 5}));
+
+// zero length target
+assert.equal(1, a.compare(b, Infinity, -Infinity));
+
+// zero length target because default for targetEnd <= targetSource
+assert.equal(1, a.compare(b, '0xff'));
+
+const oor = /out of range index/;
+
+assert.throws(() => a.compare(b, 0, 100, 0), oor);
+assert.throws(() => a.compare(b, 0, 1, 0, 100), oor);
+assert.throws(() => a.compare(b, -1), oor);
+assert.throws(() => a.compare(b, 0, '0xff'), oor);
+assert.throws(() => a.compare(b, 0, Infinity), oor);
+assert.throws(() => a.compare(b, -Infinity, Infinity), oor);
+assert.throws(() => a.compare(), /Argument must be a Buffer/);