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buffer: optimize writeInt* methods

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Remove unnecessary encoding within writeInt*
This commit is contained in:
Paul Loyd 2013-12-13 01:16:08 +04:00 committed by Fedor Indutny
parent 54da818e4b
commit 2ca6905160
1 changed files with 0 additions and 43 deletions
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43
lib/buffer.js
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@ -678,50 +678,11 @@ Buffer.prototype.writeUInt32BE = function(value, offset, noAssert) {
return writeUInt32(this, value, offset, true);
};
/*
* 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) {
value = +value;
offset = offset >>> 0;
if (!noAssert)
checkInt(this, value, offset, 1, 0x7f, -0x80);
if (value < 0) value = 0xff + value + 1;
this[offset] = value;
return offset + 1;
};
@ -732,7 +693,6 @@ Buffer.prototype.writeInt16LE = function(value, offset, noAssert) {
offset = offset >>> 0;
if (!noAssert)
checkInt(this, value, offset, 2, 0x7fff, -0x8000);
if (value < 0) value = 0xffff + value + 1;
return writeUInt16(this, value, offset, false);
};
@ -742,7 +702,6 @@ Buffer.prototype.writeInt16BE = function(value, offset, noAssert) {
offset = offset >>> 0;
if (!noAssert)
checkInt(this, value, offset, 2, 0x7fff, -0x8000);
if (value < 0) value = 0xffff + value + 1;
return writeUInt16(this, value, offset, true);
};
@ -752,7 +711,6 @@ Buffer.prototype.writeInt32LE = function(value, offset, noAssert) {
offset = offset >>> 0;
if (!noAssert)
checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000);
if (value < 0) value = 0xffffffff + value + 1;
return writeUInt32(this, value, offset, false);
};
@ -762,6 +720,5 @@ Buffer.prototype.writeInt32BE = function(value, offset, noAssert) {
offset = offset >>> 0;
if (!noAssert)
checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000);
if (value < 0) value = 0xffffffff + value + 1;
return writeUInt32(this, value, offset, true);
};