Code cosmetics comic reader
Ozzieisaacs
6 years ago
parent
405a3909b0
commit
be64961de5
@ -1,483 +0,0 @@
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/*
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* io.js
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*
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* Provides readers for bit/byte streams (reading) and a byte buffer (writing).
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*
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* Licensed under the MIT License
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*
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* Copyright(c) 2011 Google Inc.
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* Copyright(c) 2011 antimatter15
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*/
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/* global bitjs, Uint8Array */
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var bitjs = bitjs || {};
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bitjs.io = bitjs.io || {};
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(function() {
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// mask for getting the Nth bit (zero-based)
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bitjs.BIT = [ 0x01, 0x02, 0x04, 0x08,
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0x10, 0x20, 0x40, 0x80,
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0x100, 0x200, 0x400, 0x800,
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0x1000, 0x2000, 0x4000, 0x8000];
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// mask for getting N number of bits (0-8)
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var BITMASK = [0, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF ];
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/**
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* This bit stream peeks and consumes bits out of a binary stream.
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*
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* @param {ArrayBuffer} ab An ArrayBuffer object or a Uint8Array.
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* @param {boolean} rtl Whether the stream reads bits from the byte starting
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* from bit 7 to 0 (true) or bit 0 to 7 (false).
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* @param {Number} optOffset The offset into the ArrayBuffer
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* @param {Number} optLength The length of this BitStream
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*/
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bitjs.io.BitStream = function(ab, rtl, optOffset, optLength) {
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if (!ab || !ab.toString || ab.toString() !== "[object ArrayBuffer]") {
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throw "Error! BitArray constructed with an invalid ArrayBuffer object";
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}
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var offset = optOffset || 0;
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var length = optLength || ab.byteLength;
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this.bytes = new Uint8Array(ab, offset, length);
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this.bytePtr = 0; // tracks which byte we are on
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this.bitPtr = 0; // tracks which bit we are on (can have values 0 through 7)
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this.peekBits = rtl ? this.peekBitsRtl : this.peekBitsLtr;
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};
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/**
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* byte0 byte1 byte2 byte3
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* 7......0 | 7......0 | 7......0 | 7......0
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*
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* The bit pointer starts at bit0 of byte0 and moves left until it reaches
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* bit7 of byte0, then jumps to bit0 of byte1, etc.
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* @param {number} n The number of bits to peek.
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* @param {boolean=} movePointers Whether to move the pointer, defaults false.
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* @return {number} The peeked bits, as an unsigned number.
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*/
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bitjs.io.BitStream.prototype.peekBitsLtr = function(n, movePointers) {
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if (n <= 0 || typeof n !== typeof 1) {
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return 0;
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}
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movePointers = movePointers || false;
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var bytePtr = this.bytePtr;
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var bitPtr = this.bitPtr;
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var result = 0;
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var bitsIn = 0;
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var bytes = this.bytes;
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// keep going until we have no more bits left to peek at
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// TODO: Consider putting all bits from bytes we will need into a variable and then
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// shifting/masking it to just extract the bits we want.
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// This could be considerably faster when reading more than 3 or 4 bits at a time.
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while (n > 0) {
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if (bytePtr >= bytes.length) {
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throw "Error! Overflowed the bit stream! n=" + n + ", bytePtr=" + bytePtr + ", bytes.length=" +
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bytes.length + ", bitPtr=" + bitPtr;
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}
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var numBitsLeftInThisByte = (8 - bitPtr);
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var mask;
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if (n >= numBitsLeftInThisByte) {
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mask = (BITMASK[numBitsLeftInThisByte] << bitPtr);
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result |= (((bytes[bytePtr] & mask) >> bitPtr) << bitsIn);
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bytePtr++;
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bitPtr = 0;
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bitsIn += numBitsLeftInThisByte;
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n -= numBitsLeftInThisByte;
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} else {
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mask = (BITMASK[n] << bitPtr);
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result |= (((bytes[bytePtr] & mask) >> bitPtr) << bitsIn);
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bitPtr += n;
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bitsIn += n;
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n = 0;
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}
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}
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if (movePointers) {
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this.bitPtr = bitPtr;
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this.bytePtr = bytePtr;
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}
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return result;
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};
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/**
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* byte0 byte1 byte2 byte3
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* 7......0 | 7......0 | 7......0 | 7......0
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*
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* The bit pointer starts at bit7 of byte0 and moves right until it reaches
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* bit0 of byte0, then goes to bit7 of byte1, etc.
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* @param {number} n The number of bits to peek.
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* @param {boolean=} movePointers Whether to move the pointer, defaults false.
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* @return {number} The peeked bits, as an unsigned number.
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*/
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bitjs.io.BitStream.prototype.peekBitsRtl = function(n, movePointers) {
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if (n <= 0 || typeof n !== typeof 1) {
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return 0;
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}
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movePointers = movePointers || false;
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var bytePtr = this.bytePtr;
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var bitPtr = this.bitPtr;
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var result = 0;
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var bytes = this.bytes;
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// keep going until we have no more bits left to peek at
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// TODO: Consider putting all bits from bytes we will need into a variable and then
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// shifting/masking it to just extract the bits we want.
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// This could be considerably faster when reading more than 3 or 4 bits at a time.
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while (n > 0) {
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if (bytePtr >= bytes.length) {
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throw "Error! Overflowed the bit stream! n=" + n + ", bytePtr=" + bytePtr + ", bytes.length=" +
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bytes.length + ", bitPtr=" + bitPtr;
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// return -1;
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}
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var numBitsLeftInThisByte = (8 - bitPtr);
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if (n >= numBitsLeftInThisByte) {
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result <<= numBitsLeftInThisByte;
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result |= (BITMASK[numBitsLeftInThisByte] & bytes[bytePtr]);
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bytePtr++;
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bitPtr = 0;
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n -= numBitsLeftInThisByte;
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} else {
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result <<= n;
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result |= ((bytes[bytePtr] & (BITMASK[n] << (8 - n - bitPtr))) >> (8 - n - bitPtr));
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bitPtr += n;
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n = 0;
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}
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}
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if (movePointers) {
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this.bitPtr = bitPtr;
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this.bytePtr = bytePtr;
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}
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return result;
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};
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/**
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* Some voodoo magic.
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*/
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bitjs.io.BitStream.prototype.getBits = function() {
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return (((((this.bytes[this.bytePtr] & 0xff) << 16) +
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((this.bytes[this.bytePtr + 1] & 0xff) << 8) +
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((this.bytes[this.bytePtr + 2] & 0xff))) >>> (8 - this.bitPtr)) & 0xffff);
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};
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/**
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* Reads n bits out of the stream, consuming them (moving the bit pointer).
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* @param {number} n The number of bits to read.
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* @return {number} The read bits, as an unsigned number.
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*/
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bitjs.io.BitStream.prototype.readBits = function(n) {
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return this.peekBits(n, true);
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};
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/**
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* This returns n bytes as a sub-array, advancing the pointer if movePointers
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* is true. Only use this for uncompressed blocks as this throws away remaining
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* bits in the current byte.
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* @param {number} n The number of bytes to peek.
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* @param {boolean=} movePointers Whether to move the pointer, defaults false.
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* @return {Uint8Array} The subarray.
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*/
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bitjs.io.BitStream.prototype.peekBytes = function(n, movePointers) {
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if (n <= 0 || typeof n !== typeof 1) {
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return 0;
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}
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// from http://tools.ietf.org/html/rfc1951#page-11
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// "Any bits of input up to the next byte boundary are ignored."
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while (this.bitPtr !== 0) {
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this.readBits(1);
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}
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movePointers = movePointers || false;
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var bytePtr = this.bytePtr;
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// var bitPtr = this.bitPtr;
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var result = this.bytes.subarray(bytePtr, bytePtr + n);
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if (movePointers) {
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this.bytePtr += n;
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}
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return result;
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};
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/**
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* @param {number} n The number of bytes to read.
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* @return {Uint8Array} The subarray.
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*/
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bitjs.io.BitStream.prototype.readBytes = function(n) {
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return this.peekBytes(n, true);
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};
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/**
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* This object allows you to peek and consume bytes as numbers and strings
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* out of an ArrayBuffer. In this buffer, everything must be byte-aligned.
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*
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* @param {ArrayBuffer} ab The ArrayBuffer object.
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* @param {number=} optOffset The offset into the ArrayBuffer
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* @param {number=} optLength The length of this BitStream
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* @constructor
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*/
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bitjs.io.ByteStream = function(ab, optOffset, optLength) {
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var offset = optOffset || 0;
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var length = optLength || ab.byteLength;
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this.bytes = new Uint8Array(ab, offset, length);
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this.ptr = 0;
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};
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/**
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* Peeks at the next n bytes as an unsigned number but does not advance the
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* pointer
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* TODO: This apparently cannot read more than 4 bytes as a number?
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* @param {number} n The number of bytes to peek at.
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* @return {number} The n bytes interpreted as an unsigned number.
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*/
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bitjs.io.ByteStream.prototype.peekNumber = function(n) {
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// TODO: return error if n would go past the end of the stream?
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if (n <= 0 || typeof n !== typeof 1) {
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return -1;
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}
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var result = 0;
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// read from last byte to first byte and roll them in
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var curByte = this.ptr + n - 1;
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while (curByte >= this.ptr) {
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result <<= 8;
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result |= this.bytes[curByte];
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--curByte;
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}
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return result;
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};
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/**
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* Returns the next n bytes as an unsigned number (or -1 on error)
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* and advances the stream pointer n bytes.
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* @param {number} n The number of bytes to read.
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* @return {number} The n bytes interpreted as an unsigned number.
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*/
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bitjs.io.ByteStream.prototype.readNumber = function(n) {
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var num = this.peekNumber( n );
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this.ptr += n;
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return num;
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};
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/**
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* Returns the next n bytes as a signed number but does not advance the
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* pointer.
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* @param {number} n The number of bytes to read.
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* @return {number} The bytes interpreted as a signed number.
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*/
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bitjs.io.ByteStream.prototype.peekSignedNumber = function(n) {
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var num = this.peekNumber(n);
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var HALF = Math.pow(2, (n * 8) - 1);
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var FULL = HALF * 2;
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if (num >= HALF) num -= FULL;
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return num;
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};
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/**
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* Returns the next n bytes as a signed number and advances the stream pointer.
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* @param {number} n The number of bytes to read.
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* @return {number} The bytes interpreted as a signed number.
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*/
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bitjs.io.ByteStream.prototype.readSignedNumber = function(n) {
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var num = this.peekSignedNumber(n);
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this.ptr += n;
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return num;
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};
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/**
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* This returns n bytes as a sub-array, advancing the pointer if movePointers
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* is true.
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* @param {number} n The number of bytes to read.
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* @param {boolean} movePointers Whether to move the pointers.
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* @return {Uint8Array} The subarray.
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*/
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bitjs.io.ByteStream.prototype.peekBytes = function(n, movePointers) {
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if (n <= 0 || typeof n !== typeof 1) {
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return null;
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}
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var result = this.bytes.subarray(this.ptr, this.ptr + n);
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if (movePointers) {
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this.ptr += n;
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}
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return result;
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};
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/**
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* Reads the next n bytes as a sub-array.
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* @param {number} n The number of bytes to read.
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* @return {Uint8Array} The subarray.
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*/
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bitjs.io.ByteStream.prototype.readBytes = function(n) {
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return this.peekBytes(n, true);
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};
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/**
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* Peeks at the next n bytes as a string but does not advance the pointer.
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* @param {number} n The number of bytes to peek at.
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* @return {string} The next n bytes as a string.
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*/
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bitjs.io.ByteStream.prototype.peekString = function(n) {
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if (n <= 0 || typeof n !== typeof 1) {
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return "";
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}
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var result = "";
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for (var p = this.ptr, end = this.ptr + n; p < end; ++p) {
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result += String.fromCharCode(this.bytes[p]);
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}
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return result;
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};
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/**
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* Returns the next n bytes as an ASCII string and advances the stream pointer
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* n bytes.
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* @param {number} n The number of bytes to read.
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* @return {string} The next n bytes as a string.
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*/
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bitjs.io.ByteStream.prototype.readString = function(n) {
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var strToReturn = this.peekString(n);
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this.ptr += n;
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return strToReturn;
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};
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/**
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* A write-only Byte buffer which uses a Uint8 Typed Array as a backing store.
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* @param {number} numBytes The number of bytes to allocate.
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* @constructor
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*/
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bitjs.io.ByteBuffer = function(numBytes) {
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if (typeof numBytes !== typeof 1 || numBytes <= 0) {
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throw "Error! ByteBuffer initialized with '" + numBytes + "'";
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}
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this.data = new Uint8Array(numBytes);
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this.ptr = 0;
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};
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/**
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* @param {number} b The byte to insert.
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*/
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bitjs.io.ByteBuffer.prototype.insertByte = function(b) {
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// TODO: throw if byte is invalid?
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this.data[this.ptr++] = b;
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};
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/**
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* @param {Array.<number>|Uint8Array|Int8Array} bytes The bytes to insert.
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*/
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bitjs.io.ByteBuffer.prototype.insertBytes = function(bytes) {
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// TODO: throw if bytes is invalid?
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this.data.set(bytes, this.ptr);
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this.ptr += bytes.length;
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};
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/**
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* Writes an unsigned number into the next n bytes. If the number is too large
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* to fit into n bytes or is negative, an error is thrown.
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* @param {number} num The unsigned number to write.
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* @param {number} numBytes The number of bytes to write the number into.
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*/
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bitjs.io.ByteBuffer.prototype.writeNumber = function(num, numBytes) {
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if (numBytes < 1) {
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throw "Trying to write into too few bytes: " + numBytes;
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}
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if (num < 0) {
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throw "Trying to write a negative number (" + num +
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") as an unsigned number to an ArrayBuffer";
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}
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if (num > (Math.pow(2, numBytes * 8) - 1)) {
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throw "Trying to write " + num + " into only " + numBytes + " bytes";
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}
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// Roll 8-bits at a time into an array of bytes.
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var bytes = [];
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while (numBytes-- > 0) {
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var eightBits = num & 255;
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bytes.push(eightBits);
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num >>= 8;
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}
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this.insertBytes(bytes);
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};
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/**
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* Writes a signed number into the next n bytes. If the number is too large
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* to fit into n bytes, an error is thrown.
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* @param {number} num The signed number to write.
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* @param {number} numBytes The number of bytes to write the number into.
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*/
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bitjs.io.ByteBuffer.prototype.writeSignedNumber = function(num, numBytes) {
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if (numBytes < 1) {
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throw "Trying to write into too few bytes: " + numBytes;
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}
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var HALF = Math.pow(2, (numBytes * 8) - 1);
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if (num >= HALF || num < -HALF) {
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throw "Trying to write " + num + " into only " + numBytes + " bytes";
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}
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// Roll 8-bits at a time into an array of bytes.
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var bytes = [];
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while (numBytes-- > 0) {
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var eightBits = num & 255;
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bytes.push(eightBits);
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num >>= 8;
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}
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this.insertBytes(bytes);
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};
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/**
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* @param {string} str The ASCII string to write.
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*/
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bitjs.io.ByteBuffer.prototype.writeASCIIString = function(str) {
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for (var i = 0; i < str.length; ++i) {
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var curByte = str.charCodeAt(i);
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if (curByte < 0 || curByte > 255) {
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throw "Trying to write a non-ASCII string!";
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}
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this.insertByte(curByte);
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}
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};
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})();
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Reference in New Issue