npm_modules: Fork bower_components into Polymer 0.4.0 and 0.5.0 versions

bower_components/gif.js/src/LZWEncoder.js

-/*
-  LZWEncoder.js
-
-  Authors
-  Kevin Weiner (original Java version - kweiner@fmsware.com)
-  Thibault Imbert (AS3 version - bytearray.org)
-  Johan Nordberg (JS version - code@johan-nordberg.com)
-
-  Acknowledgements
-  GIFCOMPR.C - GIF Image compression routines
-  Lempel-Ziv compression based on 'compress'. GIF modifications by
-  David Rowley (mgardi@watdcsu.waterloo.edu)
-  GIF Image compression - modified 'compress'
-  Based on: compress.c - File compression ala IEEE Computer, June 1984.
-  By Authors: Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
-  Jim McKie (decvax!mcvax!jim)
-  Steve Davies (decvax!vax135!petsd!peora!srd)
-  Ken Turkowski (decvax!decwrl!turtlevax!ken)
-  James A. Woods (decvax!ihnp4!ames!jaw)
-  Joe Orost (decvax!vax135!petsd!joe)
-*/
-
-var EOF = -1;
-var BITS = 12;
-var HSIZE = 5003; // 80% occupancy
-var masks = [0x0000, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F,
-             0x003F, 0x007F, 0x00FF, 0x01FF, 0x03FF, 0x07FF,
-             0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF];
-
-function LZWEncoder(width, height, pixels, colorDepth) {
-  var initCodeSize = Math.max(2, colorDepth);
-
-  var accum = new Uint8Array(256);
-  var htab = new Int32Array(HSIZE);
-  var codetab = new Int32Array(HSIZE);
-
-  var cur_accum, cur_bits = 0;
-  var a_count;
-  var free_ent = 0; // first unused entry
-  var maxcode;
-
-  // block compression parameters -- after all codes are used up,
-  // and compression rate changes, start over.
-  var clear_flg = false;
-
-  // Algorithm: use open addressing double hashing (no chaining) on the
-  // prefix code / next character combination. We do a variant of Knuth's
-  // algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
-  // secondary probe. Here, the modular division first probe is gives way
-  // to a faster exclusive-or manipulation. Also do block compression with
-  // an adaptive reset, whereby the code table is cleared when the compression
-  // ratio decreases, but after the table fills. The variable-length output
-  // codes are re-sized at this point, and a special CLEAR code is generated
-  // for the decompressor. Late addition: construct the table according to
-  // file size for noticeable speed improvement on small files. Please direct
-  // questions about this implementation to ames!jaw.
-  var g_init_bits, ClearCode, EOFCode;
-
-  // Add a character to the end of the current packet, and if it is 254
-  // characters, flush the packet to disk.
-  function char_out(c, outs) {
-    accum[a_count++] = c;
-    if (a_count >= 254) flush_char(outs);
-  }
-
-  // Clear out the hash table
-  // table clear for block compress
-  function cl_block(outs) {
-    cl_hash(HSIZE);
-    free_ent = ClearCode + 2;
-    clear_flg = true;
-    output(ClearCode, outs);
-  }
-
-  // Reset code table
-  function cl_hash(hsize) {
-    for (var i = 0; i < hsize; ++i) htab[i] = -1;
-  }
-
-  function compress(init_bits, outs) {
-    var fcode, c, i, ent, disp, hsize_reg, hshift;
-
-    // Set up the globals: g_init_bits - initial number of bits
-    g_init_bits = init_bits;
-
-    // Set up the necessary values
-    clear_flg = false;
-    n_bits = g_init_bits;
-    maxcode = MAXCODE(n_bits);
-
-    ClearCode = 1 << (init_bits - 1);
-    EOFCode = ClearCode + 1;
-    free_ent = ClearCode + 2;
-
-    a_count = 0; // clear packet
-
-    ent = nextPixel();
-
-    hshift = 0;
-    for (fcode = HSIZE; fcode < 65536; fcode *= 2) ++hshift;
-    hshift = 8 - hshift; // set hash code range bound
-    hsize_reg = HSIZE;
-    cl_hash(hsize_reg); // clear hash table
-
-    output(ClearCode, outs);
-
-    outer_loop: while ((c = nextPixel()) != EOF) {
-      fcode = (c << BITS) + ent;
-      i = (c << hshift) ^ ent; // xor hashing
-      if (htab[i] === fcode) {
-        ent = codetab[i];
-        continue;
-      } else if (htab[i] >= 0) { // non-empty slot
-        disp = hsize_reg - i; // secondary hash (after G. Knott)
-        if (i === 0) disp = 1;
-        do {
-          if ((i -= disp) < 0) i += hsize_reg;
-          if (htab[i] === fcode) {
-            ent = codetab[i];
-            continue outer_loop;
-          }
-        } while (htab[i] >= 0);
-      }
-      output(ent, outs);
-      ent = c;
-      if (free_ent < 1 << BITS) {
-        codetab[i] = free_ent++; // code -> hashtable
-        htab[i] = fcode;
-      } else {
-        cl_block(outs);
-      }
-    }
-
-    // Put out the final code.
-    output(ent, outs);
-    output(EOFCode, outs);
-  }
-
-  function encode(outs) {
-    outs.writeByte(initCodeSize); // write "initial code size" byte
-    remaining = width * height; // reset navigation variables
-    curPixel = 0;
-    compress(initCodeSize + 1, outs); // compress and write the pixel data
-    outs.writeByte(0); // write block terminator
-  }
-
-  // Flush the packet to disk, and reset the accumulator
-  function flush_char(outs) {
-    if (a_count > 0) {
-      outs.writeByte(a_count);
-      outs.writeBytes(accum, 0, a_count);
-      a_count = 0;
-    }
-  }
-
-  function MAXCODE(n_bits) {
-    return (1 << n_bits) - 1;
-  }
-
-  // Return the next pixel from the image
-  function nextPixel() {
-    if (remaining === 0) return EOF;
-    --remaining;
-    var pix = pixels[curPixel++];
-    return pix & 0xff;
-  }
-
-  function output(code, outs) {
-    cur_accum &= masks[cur_bits];
-
-    if (cur_bits > 0) cur_accum |= (code << cur_bits);
-    else cur_accum = code;
-
-    cur_bits += n_bits;
-
-    while (cur_bits >= 8) {
-      char_out((cur_accum & 0xff), outs);
-      cur_accum >>= 8;
-      cur_bits -= 8;
-    }
-
-    // If the next entry is going to be too big for the code size,
-    // then increase it, if possible.
-    if (free_ent > maxcode || clear_flg) {
-      if (clear_flg) {
-        maxcode = MAXCODE(n_bits = g_init_bits);
-        clear_flg = false;
-      } else {
-        ++n_bits;
-        if (n_bits == BITS) maxcode = 1 << BITS;
-        else maxcode = MAXCODE(n_bits);
-      }
-    }
-
-    if (code == EOFCode) {
-      // At EOF, write the rest of the buffer.
-      while (cur_bits > 0) {
-        char_out((cur_accum & 0xff), outs);
-        cur_accum >>= 8;
-        cur_bits -= 8;
-      }
-      flush_char(outs);
-    }
-  }
-
-  this.encode = encode;
-}
-
-module.exports = LZWEncoder;