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buffer: optimize toString()
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PR-URL: #12361
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
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@mscdex @addaleax
mscdex authored and addaleax committed Apr 14, 2017
1 parent 4a86803 commit 3ee4a1a
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Showing 2 changed files with 98 additions and 73 deletions.
42 changes: 32 additions & 10 deletions benchmark/buffers/buffer-tostring.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3,25 +3,47 @@
const common = require('../common.js');

const bench = common.createBenchmark(main, {
arg: ['true', 'false'],
encoding: ['', 'utf8', 'ascii', 'latin1', 'binary', 'hex', 'UCS-2'],
args: [0, 1, 2, 3],
len: [0, 1, 64, 1024],
n: [1e7]
});

function main(conf) {
const arg = conf.arg === 'true';
var encoding = conf.encoding;
const args = conf.args | 0;
const len = conf.len | 0;
const n = conf.n | 0;
const buf = Buffer.alloc(len, 42);

if (encoding.length === 0)
encoding = undefined;

var i;
bench.start();
if (arg) {
for (i = 0; i < n; i += 1)
buf.toString('utf8');
} else {
for (i = 0; i < n; i += 1)
buf.toString();
switch (args) {
case 1:
bench.start();
for (i = 0; i < n; i += 1)
buf.toString(encoding);
bench.end(n);
break;
case 2:
bench.start();
for (i = 0; i < n; i += 1)
buf.toString(encoding, 0);
bench.end(n);
break;
case 3:
bench.start();
for (i = 0; i < n; i += 1)
buf.toString(encoding, 0, len);
bench.end(n);
break;
default:
bench.start();
for (i = 0; i < n; i += 1)
buf.toString();
bench.end(n);
break;
}
bench.end(n);
}
129 changes: 66 additions & 63 deletions lib/buffer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -483,82 +483,85 @@ Object.defineProperty(Buffer.prototype, 'offset', {
});


function slowToString(buf, encoding, start, end) {
var loweredCase = false;

// No need to verify that "buf.length <= MAX_UINT32" since it's a read-only
// property of a typed array.

// This behaves neither like String nor Uint8Array in that we set start/end
// to their upper/lower bounds if the value passed is out of range.
// undefined is handled specially as per ECMA-262 6th Edition,
// Section 13.3.3.7 Runtime Semantics: KeyedBindingInitialization.
if (start === undefined || start < 0)
start = 0;
// Return early if start > buf.length. Done here to prevent potential uint32
// coercion fail below.
if (start > buf.length)
return '';

if (end === undefined || end > buf.length)
end = buf.length;

if (end <= 0)
return '';

// Force coersion to uint32. This will also coerce falsey/NaN values to 0.
end >>>= 0;
start >>>= 0;

if (end <= start)
return '';

if (encoding === undefined) encoding = 'utf8';

while (true) {
switch (encoding) {
case 'hex':
return buf.hexSlice(start, end);

case 'utf8':
case 'utf-8':
return buf.utf8Slice(start, end);

case 'ascii':
return buf.asciiSlice(start, end);

case 'latin1':
case 'binary':
function stringSlice(buf, encoding, start, end) {
if (encoding === undefined) return buf.utf8Slice(start, end);
encoding += '';
switch (encoding.length) {
case 4:
if (encoding === 'utf8') return buf.utf8Slice(start, end);
if (encoding === 'ucs2') return buf.ucs2Slice(start, end);
encoding = encoding.toLowerCase();
if (encoding === 'utf8') return buf.utf8Slice(start, end);
if (encoding === 'ucs2') return buf.ucs2Slice(start, end);
break;
case 5:
if (encoding === 'utf-8') return buf.utf8Slice(start, end);
if (encoding === 'ascii') return buf.asciiSlice(start, end);
if (encoding === 'ucs-2') return buf.ucs2Slice(start, end);
encoding = encoding.toLowerCase();
if (encoding === 'utf-8') return buf.utf8Slice(start, end);
if (encoding === 'ascii') return buf.asciiSlice(start, end);
if (encoding === 'ucs-2') return buf.ucs2Slice(start, end);
break;
case 6:
if (encoding === 'latin1' || encoding === 'binary')
return buf.latin1Slice(start, end);

case 'base64':
return buf.base64Slice(start, end);

case 'ucs2':
case 'ucs-2':
case 'utf16le':
case 'utf-16le':
if (encoding === 'base64') return buf.base64Slice(start, end);
encoding = encoding.toLowerCase();
if (encoding === 'latin1' || encoding === 'binary')
return buf.latin1Slice(start, end);
if (encoding === 'base64') return buf.base64Slice(start, end);
break;
case 3:
if (encoding === 'hex' || encoding.toLowerCase() === 'hex')
return buf.hexSlice(start, end);
break;
case 7:
if (encoding === 'utf16le' || encoding.toLowerCase() === 'utf16le')
return buf.ucs2Slice(start, end);

default:
if (loweredCase)
throw new TypeError('Unknown encoding: ' + encoding);
encoding = (encoding + '').toLowerCase();
loweredCase = true;
}
break;
case 8:
if (encoding === 'utf-16le' || encoding.toLowerCase() === 'utf-16le')
return buf.ucs2Slice(start, end);
break;
}
throw new TypeError('Unknown encoding: ' + encoding);
}


Buffer.prototype.copy = function(target, targetStart, sourceStart, sourceEnd) {
return binding.copy(this, target, targetStart, sourceStart, sourceEnd);
};

// No need to verify that "buf.length <= MAX_UINT32" since it's a read-only
// property of a typed array.
// This behaves neither like String nor Uint8Array in that we set start/end
// to their upper/lower bounds if the value passed is out of range.
Buffer.prototype.toString = function(encoding, start, end) {
let result;
var result;
if (arguments.length === 0) {
result = this.utf8Slice(0, this.length);
} else {
result = slowToString(this, encoding, start, end);
const len = this.length;
if (len === 0)
return '';

if (!start || start < 0)
start = 0;
else if (start >= len)
return '';

if (end === undefined || end > len)
end = len;
else if (end <= 0)
return '';

start |= 0;
end |= 0;

if (end <= start)
return '';
result = stringSlice(this, encoding, start, end);
}
if (result === undefined)
throw new Error('"toString()" failed');
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