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buffer: optimize hex_decode
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PR-URL: #7602
Reviewed-By: Anna Henningsen <anna@addaleax.net>
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chjj authored and MylesBorins committed Oct 26, 2016
1 parent 58f3fa1 commit 17c4187
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Showing 3 changed files with 93 additions and 13 deletions.
26 changes: 26 additions & 0 deletions benchmark/buffers/buffer-hex.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
'use strict';

const common = require('../common.js');

const bench = common.createBenchmark(main, {
len: [0, 1, 64, 1024],
n: [1e7]
});

function main(conf) {
const len = conf.len | 0;
const n = conf.n | 0;
const buf = Buffer.alloc(len);

for (let i = 0; i < buf.length; i++)
buf[i] = i & 0xff;

const hex = buf.toString('hex');

bench.start();

for (let i = 0; i < n; i += 1)
Buffer.from(hex, 'hex');

bench.end(n);
}
37 changes: 24 additions & 13 deletions src/string_bytes.cc
Original file line number Diff line number Diff line change
Expand Up @@ -239,16 +239,27 @@ size_t base64_decode(char* const dst, const size_t dstlen,
}


template <typename TypeName>
unsigned hex2bin(TypeName c) {
if (c >= '0' && c <= '9')
return c - '0';
if (c >= 'A' && c <= 'F')
return 10 + (c - 'A');
if (c >= 'a' && c <= 'f')
return 10 + (c - 'a');
return static_cast<unsigned>(-1);
}
static const int8_t unhex_table[256] =
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
};

#define unhex(x) \
static_cast<unsigned>(unhex_table[static_cast<uint8_t>(x)])


template <typename TypeName>
Expand All @@ -258,11 +269,11 @@ size_t hex_decode(char* buf,
const size_t srcLen) {
size_t i;
for (i = 0; i < len && i * 2 + 1 < srcLen; ++i) {
unsigned a = hex2bin(src[i * 2 + 0]);
unsigned b = hex2bin(src[i * 2 + 1]);
unsigned a = unhex(src[i * 2 + 0]);
unsigned b = unhex(src[i * 2 + 1]);
if (!~a || !~b)
return i;
buf[i] = a * 16 + b;
buf[i] = (a << 4) | b;
}

return i;
Expand Down
43 changes: 43 additions & 0 deletions test/parallel/test-buffer-badhex.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,43 @@
'use strict';
require('../common');
const assert = require('assert');
const Buffer = require('buffer').Buffer;

// Test hex strings and bad hex strings
{
const buf1 = Buffer.alloc(4);
assert.strictEqual(buf1.length, 4);
assert.deepStrictEqual(buf1, new Buffer([0, 0, 0, 0]));
assert.strictEqual(buf1.write('abcdxx', 0, 'hex'), 2);
assert.deepStrictEqual(buf1, new Buffer([0xab, 0xcd, 0x00, 0x00]));
assert.strictEqual(buf1.toString('hex'), 'abcd0000');
assert.strictEqual(buf1.write('abcdef01', 0, 'hex'), 4);
assert.deepStrictEqual(buf1, new Buffer([0xab, 0xcd, 0xef, 0x01]));
assert.strictEqual(buf1.toString('hex'), 'abcdef01');

const buf2 = Buffer.from(buf1.toString('hex'), 'hex');
assert.strictEqual(buf1.toString('hex'), buf2.toString('hex'));

const buf3 = Buffer.alloc(5);
assert.strictEqual(buf3.write('abcdxx', 1, 'hex'), 2);
assert.strictEqual(buf3.toString('hex'), '00abcd0000');

const buf4 = Buffer.alloc(4);
assert.deepStrictEqual(buf4, new Buffer([0, 0, 0, 0]));
assert.strictEqual(buf4.write('xxabcd', 0, 'hex'), 0);
assert.deepStrictEqual(buf4, new Buffer([0, 0, 0, 0]));
assert.strictEqual(buf4.write('xxab', 1, 'hex'), 0);
assert.deepStrictEqual(buf4, new Buffer([0, 0, 0, 0]));
assert.strictEqual(buf4.write('cdxxab', 0, 'hex'), 1);
assert.deepStrictEqual(buf4, new Buffer([0xcd, 0, 0, 0]));

const buf5 = Buffer.alloc(256);
for (let i = 0; i < 256; i++)
buf5[i] = i;

const hex = buf5.toString('hex');
assert.deepStrictEqual(Buffer.from(hex, 'hex'), buf5);

const badHex = hex.slice(0, 256) + 'xx' + hex.slice(256, 510);
assert.deepStrictEqual(Buffer.from(badHex, 'hex'), buf5.slice(0, 128));
}

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