"use strict";
  /*
     Copyright (C) 2012 by Jeremy P. White <jwhite@codeweavers.com>
  
     This file is part of spice-html5.
  
     spice-html5 is free software: you can redistribute it and/or modify
     it under the terms of the GNU Lesser General Public License as published by
     the Free Software Foundation, either version 3 of the License, or
     (at your option) any later version.
  
     spice-html5 is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU Lesser General Public License for more details.
  
     You should have received a copy of the GNU Lesser General Public License
     along with spice-html5.  If not, see <http://www.gnu.org/licenses/>.
  */
  
  /*----------------------------------------------------------------------------
  **  crc logic from rfc2083 ported to Javascript
  **--------------------------------------------------------------------------*/
  
  var rfc2083_crc_table = Array(256);
  var rfc2083_crc_table_computed = 0;
  /* Make the table for a fast CRC. */
  function rfc2083_make_crc_table()
  {
      var c;
      var n, k;
      for (n = 0; n < 256; n++)
      {
          c = n;
          for (k = 0; k < 8; k++)
          {
              if (c & 1)
                  c = ((0xedb88320 ^ (c >>> 1)) >>> 0) & 0xffffffff;
              else
                  c = c >>> 1;
          }
          rfc2083_crc_table[n] = c;
      }
  
      rfc2083_crc_table_computed = 1;
  }
  
  /* Update a running CRC with the bytes buf[0..len-1]--the CRC
       should be initialized to all 1's, and the transmitted value
       is the 1's complement of the final running CRC (see the
       crc() routine below)). */
  
  function rfc2083_update_crc(crc, u8buf, at, len)
  {
      var c = crc;
      var n;
  
      if (!rfc2083_crc_table_computed)
          rfc2083_make_crc_table();
  
      for (n = 0; n < len; n++)
      {
          c = rfc2083_crc_table[(c ^ u8buf[at + n]) & 0xff] ^ (c >>> 8);
      }
  
      return c;
  }
  
  function rfc2083_crc(u8buf, at, len)
  {
      return rfc2083_update_crc(0xffffffff, u8buf, at, len) ^ 0xffffffff;
  }
  
  function crc32(mb, at, len)
  {
      var u8 = new Uint8Array(mb);
      return rfc2083_crc(u8, at, len);
  }
  
  function PngIHDR(width, height)
  {
      this.width = width;
      this.height = height;
      this.depth = 8;
      this.type = 6;
      this.compression = 0;
      this.filter = 0;
      this.interlace = 0;
  }
  
  PngIHDR.prototype =
  {
      to_buffer: function(a, at)
      {
          at = at || 0;
          var orig = at;
          var dv = new SpiceDataView(a);
          dv.setUint32(at, this.buffer_size() - 12); at += 4;
          dv.setUint8(at, 'I'.charCodeAt(0)); at++;
          dv.setUint8(at, 'H'.charCodeAt(0)); at++;
          dv.setUint8(at, 'D'.charCodeAt(0)); at++;
          dv.setUint8(at, 'R'.charCodeAt(0)); at++;
          dv.setUint32(at, this.width); at += 4;
          dv.setUint32(at, this.height); at += 4;
          dv.setUint8(at, this.depth); at++;
          dv.setUint8(at, this.type); at++;
          dv.setUint8(at, this.compression); at++;
          dv.setUint8(at, this.filter); at++;
          dv.setUint8(at, this.interlace); at++;
          dv.setUint32(at, crc32(a, orig + 4, this.buffer_size() - 8)); at += 4;
          return at;
      },
      buffer_size: function()
      {
          return 12 + 13;
      }
  }
  
  
  function adler()
  {
      this.s1 = 1;
      this.s2 = 0;
  }
  
  adler.prototype.update = function(b)
  {
      this.s1 += b;
      this.s1 %= 65521;
      this.s2 += this.s1;
      this.s2 %= 65521;
  }
  
  function PngIDAT(width, height, bytes)
  {
      if (bytes.byteLength > 65535)
      {
          throw new Error("Cannot handle more than 64K");
      }
      this.data = bytes;
      this.width = width;
      this.height = height;
  }
  
  PngIDAT.prototype =
  {
      to_buffer: function(a, at)
      {
          at = at || 0;
          var orig = at;
          var x, y, i, j;
          var dv = new SpiceDataView(a);
          var zsum = new adler();
          dv.setUint32(at, this.buffer_size() - 12); at += 4;
          dv.setUint8(at, 'I'.charCodeAt(0)); at++;
          dv.setUint8(at, 'D'.charCodeAt(0)); at++;
          dv.setUint8(at, 'A'.charCodeAt(0)); at++;
          dv.setUint8(at, 'T'.charCodeAt(0)); at++;
  
          /* zlib header.  */
          dv.setUint8(at, 0x78); at++;
          dv.setUint8(at, 0x01); at++;
  
          /* Deflate header.  Specifies uncompressed, final bit */
          dv.setUint8(at, 0x80); at++;
          dv.setUint16(at, this.data.byteLength + this.height); at += 2;
          dv.setUint16(at, ~(this.data.byteLength + this.height)); at += 2;
          var u8 = new Uint8Array(this.data);
          for (i = 0, y = 0; y < this.height; y++)
          {
              /* Filter type 0 - uncompressed */
              dv.setUint8(at, 0); at++;
              zsum.update(0);
              for (x = 0; x < this.width && i < this.data.byteLength; x++)
              {
                  zsum.update(u8[i]);
                  dv.setUint8(at, u8[i++]); at++;
                  zsum.update(u8[i]);
                  dv.setUint8(at, u8[i++]); at++;
                  zsum.update(u8[i]);
                  dv.setUint8(at, u8[i++]); at++;
                  zsum.update(u8[i]);
                  dv.setUint8(at, u8[i++]); at++;
              }
          }
  
          /* zlib checksum.   */
          dv.setUint16(at, zsum.s2); at+=2;
          dv.setUint16(at, zsum.s1); at+=2;
  
          /* FIXME - something is not quite right with the zlib code;
                     you get an error from libpng if you open the image in
                     gimp.  But it works, so it's good enough for now... */
  
          dv.setUint32(at, crc32(a, orig + 4, this.buffer_size() - 8)); at += 4;
          return at;
      },
      buffer_size: function()
      {
          return 12 + this.data.byteLength + this.height + 4 + 2 + 1 + 2 + 2;
      }
  }
  
  
  function PngIEND()
  {
  }
  
  PngIEND.prototype =
  {
      to_buffer: function(a, at)
      {
          at = at || 0;
          var orig = at;
          var i;
          var dv = new SpiceDataView(a);
          dv.setUint32(at, this.buffer_size() - 12); at += 4;
          dv.setUint8(at, 'I'.charCodeAt(0)); at++;
          dv.setUint8(at, 'E'.charCodeAt(0)); at++;
          dv.setUint8(at, 'N'.charCodeAt(0)); at++;
          dv.setUint8(at, 'D'.charCodeAt(0)); at++;
          dv.setUint32(at, crc32(a, orig + 4, this.buffer_size() - 8)); at += 4;
          return at;
      },
      buffer_size: function()
      {
          return 12;
      }
  }
  
  
  function create_rgba_png(width, height, bytes)
  {
      var i;
      var ihdr = new PngIHDR(width, height);
      var idat = new PngIDAT(width, height, bytes);
      var iend = new PngIEND;
  
      var mb = new ArrayBuffer(ihdr.buffer_size() + idat.buffer_size() + iend.buffer_size());
      var at = ihdr.to_buffer(mb);
      at = idat.to_buffer(mb, at);
      at = iend.to_buffer(mb, at);
  
      var u8 = new Uint8Array(mb);
      var str = "";
      for (i = 0; i < at; i++)
      {
          str += "%";
          if (u8[i] < 16)
              str += "0";
          str += u8[i].toString(16);
      }
  
  
      return "%89PNG%0D%0A%1A%0A" + str;
  }