diff options
author | Nick Apperson <apperson@gmail.com> | 2014-03-25 09:51:13 -0500 |
---|---|---|
committer | Trevor Norris <trev.norris@gmail.com> | 2014-06-23 16:58:55 -0700 |
commit | ee95e4f5f76cc2ac637ab53056a7c514bc49e13c (patch) | |
tree | 164ddb8b0d8f75a324e1473b2c706f368e50b171 | |
parent | 72dcc26c7af47fff906123f1afb3510a0c22b28c (diff) | |
download | node-new-ee95e4f5f76cc2ac637ab53056a7c514bc49e13c.tar.gz |
buffer: improve {read,write}{U}Int* methods
Increase the performance and simplify the logic of Buffer#write{U}Int*
and Buffer#read{U}Int* methods by placing the byte manipulation code
directly inline.
Also improve the speed of buffer-write benchmarks by creating a new
call directly to each method by using Function() instead of calling by
buff[fn].
Signed-off-by: Trevor Norris <trev.norris@gmail.com>
Conflicts:
lib/buffer.js
-rw-r--r-- | benchmark/buffers/buffer-read.js | 9 | ||||
-rw-r--r-- | benchmark/buffers/buffer-write.js | 24 | ||||
-rw-r--r-- | lib/buffer.js | 230 |
3 files changed, 71 insertions, 192 deletions
diff --git a/benchmark/buffers/buffer-read.js b/benchmark/buffers/buffer-read.js index fccd99dcd2..92138bccef 100644 --- a/benchmark/buffers/buffer-read.js +++ b/benchmark/buffers/buffer-read.js @@ -20,9 +20,12 @@ function main(conf) { var fn = 'read' + conf.type; buff.writeDoubleLE(0, 0, noAssert); + var testFunction = new Function('buff', [ + "for (var i = 0; i !== " + len + "; i++) {", + " buff." + fn + "(0, " + JSON.stringify(noAssert) + ");", + "}" + ].join("\n")); bench.start(); - for (var i = 0; i < len; i++) { - buff[fn](0, noAssert); - } + testFunction(buff); bench.end(len / 1e6); } diff --git a/benchmark/buffers/buffer-write.js b/benchmark/buffers/buffer-write.js index 4dbfcb6096..2a2a0e37e3 100644 --- a/benchmark/buffers/buffer-write.js +++ b/benchmark/buffers/buffer-write.js @@ -15,9 +15,9 @@ var bench = common.createBenchmark(main, { const INT8 = 0x7f; const INT16 = 0x7fff; const INT32 = 0x7fffffff; -const UINT8 = INT8 * 2; -const UINT16 = INT16 * 2; -const UINT32 = INT32 * 2; +const UINT8 = (INT8 * 2) + 1; +const UINT16 = (INT16 * 2) + 1; +const UINT32 = INT32; var mod = { writeInt8: INT8, @@ -47,17 +47,23 @@ function main(conf) { function benchInt(buff, fn, len, noAssert) { var m = mod[fn]; + var testFunction = new Function('buff', [ + "for (var i = 0; i !== " + len + "; i++) {", + " buff." + fn + "(i & " + m + ", 0, " + JSON.stringify(noAssert) + ");", + "}" + ].join("\n")); bench.start(); - for (var i = 0; i < len; i++) { - buff[fn](i % m, 0, noAssert); - } + testFunction(buff); bench.end(len / 1e6); } function benchFloat(buff, fn, len, noAssert) { + var testFunction = new Function('buff', [ + "for (var i = 0; i !== " + len + "; i++) {", + " buff." + fn + "(i, 0, " + JSON.stringify(noAssert) + ");", + "}" + ].join("\n")); bench.start(); - for (var i = 0; i < len; i++) { - buff[fn](i * 0.1, 0, noAssert); - } + testFunction(buff); bench.end(len / 1e6); } diff --git a/lib/buffer.js b/lib/buffer.js index 51406b6ed6..39facdecbb 100644 --- a/lib/buffer.js +++ b/lib/buffer.js @@ -590,112 +590,41 @@ Buffer.prototype.readUInt8 = function(offset, noAssert) { }; -function readUInt16(buffer, offset, isBigEndian) { - var val = 0; - if (isBigEndian) { - val = buffer[offset] << 8; - val |= buffer[offset + 1]; - } else { - val = buffer[offset]; - val |= buffer[offset + 1] << 8; - } - - return val; -} - - Buffer.prototype.readUInt16LE = function(offset, noAssert) { if (!noAssert) checkOffset(offset, 2, this.length); - return readUInt16(this, offset, false, noAssert); + return this[offset] | (this[offset + 1] << 8); }; Buffer.prototype.readUInt16BE = function(offset, noAssert) { if (!noAssert) checkOffset(offset, 2, this.length); - return readUInt16(this, offset, true, noAssert); + return (this[offset] << 8) | this[offset + 1]; }; -function readUInt32(buffer, offset, isBigEndian, noAssert) { - var val = 0; - - if (isBigEndian) { - val = buffer[offset + 1] << 16; - val |= buffer[offset + 2] << 8; - val |= buffer[offset + 3]; - val = val + (buffer[offset] << 24 >>> 0); - } else { - val = buffer[offset + 2] << 16; - val |= buffer[offset + 1] << 8; - val |= buffer[offset]; - val = val + (buffer[offset + 3] << 24 >>> 0); - } - - return val; -} - - Buffer.prototype.readUInt32LE = function(offset, noAssert) { if (!noAssert) checkOffset(offset, 4, this.length); - return readUInt32(this, offset, false, noAssert); + + return ((this[offset]) | + (this[offset + 1] << 8) | + (this[offset + 2] << 16)) + + (this[offset + 3] * 0x1000000); }; Buffer.prototype.readUInt32BE = function(offset, noAssert) { if (!noAssert) checkOffset(offset, 4, this.length); - return readUInt32(this, offset, true, noAssert); -}; + return (this[offset] * 0x1000000) + + ((this[offset + 1] << 16) | + (this[offset + 2] << 8)) | + (this[offset + 3]); +}; -/* - * Signed integer types, yay team! A reminder on how two's complement actually - * works. The first bit is the signed bit, i.e. tells us whether or not the - * number should be positive or negative. If the two's complement value is - * positive, then we're done, as it's equivalent to the unsigned representation. - * - * Now if the number is positive, you're pretty much done, you can just leverage - * the unsigned translations and return those. Unfortunately, negative numbers - * aren't quite that straightforward. - * - * At first glance, one might be inclined to use the traditional formula to - * translate binary numbers between the positive and negative values in two's - * complement. (Though it doesn't quite work for the most negative value) - * Mainly: - * - invert all the bits - * - add one to the result - * - * Of course, this doesn't quite work in Javascript. Take for example the value - * of -128. This could be represented in 16 bits (big-endian) as 0xff80. But of - * course, Javascript will do the following: - * - * > ~0xff80 - * -65409 - * - * Whoh there, Javascript, that's not quite right. But wait, according to - * Javascript that's perfectly correct. When Javascript ends up seeing the - * constant 0xff80, it has no notion that it is actually a signed number. It - * assumes that we've input the unsigned value 0xff80. Thus, when it does the - * binary negation, it casts it into a signed value, (positive 0xff80). Then - * when you perform binary negation on that, it turns it into a negative number. - * - * Instead, we're going to have to use the following general formula, that works - * in a rather Javascript friendly way. I'm glad we don't support this kind of - * weird numbering scheme in the kernel. - * - * (BIT-MAX - (unsigned)val + 1) * -1 - * - * The astute observer, may think that this doesn't make sense for 8-bit numbers - * (really it isn't necessary for them). However, when you get 16-bit numbers, - * you do. Let's go back to our prior example and see how this will look: - * - * (0xffff - 0xff80 + 1) * -1 - * (0x007f + 1) * -1 - * (0x0080) * -1 - */ Buffer.prototype.readInt8 = function(offset, noAssert) { if (!noAssert) @@ -706,49 +635,41 @@ Buffer.prototype.readInt8 = function(offset, noAssert) { }; -function readInt16(buffer, offset, isBigEndian) { - var val = readUInt16(buffer, offset, isBigEndian); - - if (!(val & 0x8000)) - return val; - return (0xffff - val + 1) * -1; -} - - Buffer.prototype.readInt16LE = function(offset, noAssert) { if (!noAssert) checkOffset(offset, 2, this.length); - return readInt16(this, offset, false); + var val = this[offset] | (this[offset + 1] << 8); + return (val & 0x8000) ? val | 0xFFFF0000 : val; }; Buffer.prototype.readInt16BE = function(offset, noAssert) { if (!noAssert) checkOffset(offset, 2, this.length); - return readInt16(this, offset, true); + var val = this[offset + 1] | (this[offset] << 8); + return (val & 0x8000) ? val | 0xFFFF0000 : val; }; -function readInt32(buffer, offset, isBigEndian) { - var val = readUInt32(buffer, offset, isBigEndian); - - if (!(val & 0x80000000)) - return (val); - return (0xffffffff - val + 1) * -1; -} - - Buffer.prototype.readInt32LE = function(offset, noAssert) { if (!noAssert) checkOffset(offset, 4, this.length); - return readInt32(this, offset, false); + + return (this[offset]) | + (this[offset + 1] << 8) | + (this[offset + 2] << 16) | + (this[offset + 3] << 24); }; Buffer.prototype.readInt32BE = function(offset, noAssert) { if (!noAssert) checkOffset(offset, 4, this.length); - return readInt32(this, offset, true); + + return (this[offset] << 24) | + (this[offset + 1] << 16) | + (this[offset + 2] << 8) | + (this[offset + 3]); }; Buffer.prototype.readFloatLE = function(offset, noAssert) { @@ -796,97 +717,42 @@ Buffer.prototype.writeUInt8 = function(value, offset, noAssert) { }; -function writeUInt16(buffer, value, offset, isBigEndian) { - if (isBigEndian) { - buffer[offset] = (value & 0xff00) >>> 8; - buffer[offset + 1] = value & 0x00ff; - } else { - buffer[offset + 1] = (value & 0xff00) >>> 8; - buffer[offset] = value & 0x00ff; - } -} - - Buffer.prototype.writeUInt16LE = function(value, offset, noAssert) { if (!noAssert) checkInt(this, value, offset, 2, 0xffff, 0); - writeUInt16(this, value, offset, false); + this[offset] = value; + this[offset + 1] = (value >>> 8); }; Buffer.prototype.writeUInt16BE = function(value, offset, noAssert) { if (!noAssert) checkInt(this, value, offset, 2, 0xffff, 0); - writeUInt16(this, value, offset, true); + this[offset] = (value >>> 8); + this[offset + 1] = value; }; -function writeUInt32(buffer, value, offset, isBigEndian) { - if (isBigEndian) { - buffer[offset] = (value >>> 24) & 0xff; - buffer[offset + 1] = (value >>> 16) & 0xff; - buffer[offset + 2] = (value >>> 8) & 0xff; - buffer[offset + 3] = value & 0xff; - } else { - buffer[offset + 3] = (value >>> 24) & 0xff; - buffer[offset + 2] = (value >>> 16) & 0xff; - buffer[offset + 1] = (value >>> 8) & 0xff; - buffer[offset] = value & 0xff; - } -} - - Buffer.prototype.writeUInt32LE = function(value, offset, noAssert) { if (!noAssert) checkInt(this, value, offset, 4, 0xffffffff, 0); - writeUInt32(this, value, offset, false); + this[offset + 3] = (value >>> 24); + this[offset + 2] = (value >>> 16); + this[offset + 1] = (value >>> 8); + this[offset] = value; }; Buffer.prototype.writeUInt32BE = function(value, offset, noAssert) { if (!noAssert) checkInt(this, value, offset, 4, 0xffffffff, 0); - writeUInt32(this, value, offset, true); + this[offset] = (value >>> 24); + this[offset + 1] = (value >>> 16); + this[offset + 2] = (value >>> 8); + this[offset + 3] = value; }; -/* - * We now move onto our friends in the signed number category. Unlike unsigned - * numbers, we're going to have to worry a bit more about how we put values into - * arrays. Since we are only worrying about signed 32-bit values, we're in - * slightly better shape. Unfortunately, we really can't do our favorite binary - * & in this system. It really seems to do the wrong thing. For example: - * - * > -32 & 0xff - * 224 - * - * What's happening above is really: 0xe0 & 0xff = 0xe0. However, the results of - * this aren't treated as a signed number. Ultimately a bad thing. - * - * What we're going to want to do is basically create the unsigned equivalent of - * our representation and pass that off to the wuint* functions. To do that - * we're going to do the following: - * - * - if the value is positive - * we can pass it directly off to the equivalent wuint - * - if the value is negative - * we do the following computation: - * mb + val + 1, where - * mb is the maximum unsigned value in that byte size - * val is the Javascript negative integer - * - * - * As a concrete value, take -128. In signed 16 bits this would be 0xff80. If - * you do out the computations: - * - * 0xffff - 128 + 1 - * 0xffff - 127 - * 0xff80 - * - * You can then encode this value as the signed version. This is really rather - * hacky, but it should work and get the job done which is our goal here. - */ - Buffer.prototype.writeInt8 = function(value, offset, noAssert) { if (!noAssert) checkInt(this, value, offset, 1, 0x7f, -0x80); @@ -898,32 +764,36 @@ Buffer.prototype.writeInt8 = function(value, offset, noAssert) { Buffer.prototype.writeInt16LE = function(value, offset, noAssert) { if (!noAssert) checkInt(this, value, offset, 2, 0x7fff, -0x8000); - if (value < 0) value = 0xffff + value + 1; - writeUInt16(this, value, offset, false); + this[offset] = value; + this[offset + 1] = (value >>> 8); }; Buffer.prototype.writeInt16BE = function(value, offset, noAssert) { if (!noAssert) checkInt(this, value, offset, 2, 0x7fff, -0x8000); - if (value < 0) value = 0xffff + value + 1; - writeUInt16(this, value, offset, true); + this[offset] = (value >>> 8); + this[offset + 1] = value; }; Buffer.prototype.writeInt32LE = function(value, offset, noAssert) { if (!noAssert) checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000); - if (value < 0) value = 0xffffffff + value + 1; - writeUInt32(this, value, offset, false); + this[offset] = value; + this[offset + 1] = (value >>> 8); + this[offset + 2] = (value >>> 16); + this[offset + 3] = (value >>> 24); }; Buffer.prototype.writeInt32BE = function(value, offset, noAssert) { if (!noAssert) checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000); - if (value < 0) value = 0xffffffff + value + 1; - writeUInt32(this, value, offset, true); + this[offset] = (value >>> 24); + this[offset + 1] = (value >>> 16); + this[offset + 2] = (value >>> 8); + this[offset + 3] = value; }; |