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parallel-library/cps/static/js/io/bytebuffer.js

125 lines
3.5 KiB
JavaScript

/*
* bytestream.js
*
* Provides a writer for bytes.
*
* Licensed under the MIT License
*
* Copyright(c) 2011 Google Inc.
* Copyright(c) 2011 antimatter15
*/
/* global bitjs, Uint8Array */
var bitjs = bitjs || {};
bitjs.io = bitjs.io || {};
(function() {
/**
* A write-only Byte buffer which uses a Uint8 Typed Array as a backing store.
* @param {number} numBytes The number of bytes to allocate.
* @constructor
*/
bitjs.io.ByteBuffer = function(numBytes) {
if (typeof numBytes !== typeof 1 || numBytes <= 0) {
throw "Error! ByteBuffer initialized with '" + numBytes + "'";
}
this.data = new Uint8Array(numBytes);
this.ptr = 0;
};
/**
* @param {number} b The byte to insert.
*/
bitjs.io.ByteBuffer.prototype.insertByte = function(b) {
// TODO: throw if byte is invalid?
this.data[this.ptr++] = b;
};
/**
* @param {Array.<number>|Uint8Array|Int8Array} bytes The bytes to insert.
*/
bitjs.io.ByteBuffer.prototype.insertBytes = function(bytes) {
// TODO: throw if bytes is invalid?
this.data.set(bytes, this.ptr);
this.ptr += bytes.length;
};
/**
* Writes an unsigned number into the next n bytes. If the number is too large
* to fit into n bytes or is negative, an error is thrown.
* @param {number} num The unsigned number to write.
* @param {number} numBytes The number of bytes to write the number into.
*/
bitjs.io.ByteBuffer.prototype.writeNumber = function(num, numBytes) {
if (numBytes < 1) {
throw "Trying to write into too few bytes: " + numBytes;
}
if (num < 0) {
throw "Trying to write a negative number (" + num +
") as an unsigned number to an ArrayBuffer";
}
if (num > (Math.pow(2, numBytes * 8) - 1)) {
throw "Trying to write " + num + " into only " + numBytes + " bytes";
}
// Roll 8-bits at a time into an array of bytes.
var bytes = [];
while (numBytes-- > 0) {
var eightBits = num & 255;
bytes.push(eightBits);
num >>= 8;
}
this.insertBytes(bytes);
};
/**
* Writes a signed number into the next n bytes. If the number is too large
* to fit into n bytes, an error is thrown.
* @param {number} num The signed number to write.
* @param {number} numBytes The number of bytes to write the number into.
*/
bitjs.io.ByteBuffer.prototype.writeSignedNumber = function(num, numBytes) {
if (numBytes < 1) {
throw "Trying to write into too few bytes: " + numBytes;
}
var HALF = Math.pow(2, (numBytes * 8) - 1);
if (num >= HALF || num < -HALF) {
throw "Trying to write " + num + " into only " + numBytes + " bytes";
}
// Roll 8-bits at a time into an array of bytes.
var bytes = [];
while (numBytes-- > 0) {
var eightBits = num & 255;
bytes.push(eightBits);
num >>= 8;
}
this.insertBytes(bytes);
};
/**
* @param {string} str The ASCII string to write.
*/
bitjs.io.ByteBuffer.prototype.writeASCIIString = function(str) {
for (var i = 0; i < str.length; ++i) {
var curByte = str.charCodeAt(i);
if (curByte < 0 || curByte > 255) {
throw "Trying to write a non-ASCII string!";
}
this.insertByte(curByte);
}
};
})();