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src: only memcmp if length > 0 in Buffer::Compare #2544

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src: only memcmp if length > 0 in Buffer::Compare #2544

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src: only memcmp if length > 0 in Buffer::Compare 
Both pointer arguments to memcmp are defined as non-null
and compiler optimizes upon that
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@skomski
skomski committed Aug 27, 2015
commit 5de6a6ec0e06bb0a314f3150976db5503bb17235
3 changes: 2 additions & 1 deletion src/node_buffer.cc
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Expand Up @@ -835,7 +835,8 @@ void Compare(const FunctionCallbackInfo<Value> &args) {

size_t cmp_length = MIN(obj_a_length, obj_b_length);

int32_t val = memcmp(obj_a_data, obj_b_data, cmp_length);
int val = cmp_length > 0 ? memcmp(obj_a_data, obj_b_data, cmp_length)
: 0;

// Normalize val to be an integer in the range of [1, -1] since
// implementations of memcmp() can vary by platform.
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3 changes: 3 additions & 0 deletions test/parallel/test-buffer.js
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Expand Up @@ -1137,6 +1137,9 @@ assert.equal(Buffer.compare(d, b), 1);
assert.equal(Buffer.compare(b, d), -1);
assert.equal(Buffer.compare(c, c), 0);

assert.equal(Buffer.compare(Buffer(0), Buffer(0)), 0);
assert.equal(Buffer.compare(Buffer(0), Buffer(1)), -1);
assert.equal(Buffer.compare(Buffer(1), Buffer(0)), 1);
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@Fishrock123 Fishrock123 Aug 28, 2015

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-0 wouldn't change anything here, right?

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@trevnorris trevnorris Aug 28, 2015

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-0 only flips the signed bit on the double. Which is dropped when the value is converted to an int.


assert.throws(function() {
var b = new Buffer(1);
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