emscripten/tools/crunch-worker.js

// From Brandon Jones' awesome WebGL texture utils,
// https://github.com/toji/webgl-texture-utils
// which in turn based off of Evan Parker's cool work,
// http://www-cs-students.stanford.edu/~eparker/files/crunch/decode_test.html
//
// This combines crunch-worker.js and crn_decomp.js. Minor changes
// to make it work that way, and to return all levels in one array

    /*
     * Copyright (c) 2012 Brandon Jones
     *
     * This software is provided 'as-is', without any express or implied
     * warranty. In no event will the authors be held liable for any damages
     * arising from the use of this software.
     *
     * Permission is granted to anyone to use this software for any purpose,
     * including commercial applications, and to alter it and redistribute it
     * freely, subject to the following restrictions:
     *
     *    1. The origin of this software must not be misrepresented; you must not
     *    claim that you wrote the original software. If you use this software
     *    in a product, an acknowledgment in the product documentation would be
     *    appreciated but is not required.
     *
     *    2. Altered source versions must be plainly marked as such, and must not
     *    be misrepresented as being the original software.
     *
     *    3. This notice may not be removed or altered from any source
     *    distribution.
     */

    // Taken from crnlib.h
    var cCRNFmtInvalid = -1;

    var cCRNFmtDXT1 = 0;
    var cCRNFmtDXT3 = 1;
    var cCRNFmtDXT5 = 2;

    // Various DXT5 derivatives
    var cCRNFmtDXT5_CCxY = 3;    // Luma-chroma
    var cCRNFmtDXT5_xGxR = 4;    // Swizzled 2-component
    var cCRNFmtDXT5_xGBR = 5;    // Swizzled 3-component
    var cCRNFmtDXT5_AGBR = 6;    // Swizzled 4-component

    // ATI 3DC and X360 DXN
    var cCRNFmtDXN_XY = 7;
    var cCRNFmtDXN_YX = 8;

    // DXT5 alpha blocks only
    var cCRNFmtDXT5A = 9;

    function arrayBufferCopy(src, dst, dstByteOffset, numBytes) {
        dst.set(src.subarray(0, numBytes), dstByteOffset);
    }

    function deCrunch(bytes, filename) {
        var srcSize = bytes.length;
        var src = Module._malloc(srcSize),
            format, internalFormat, dst, dstSize,
            width, height, levels, dxtData, rgb565Data, i;
        
        arrayBufferCopy(bytes, Module.HEAPU8, src, srcSize);

        format = Module._crn_get_dxt_format(src, srcSize);
        
        if(format != cCRNFmtDXT1 && format != cCRNFmtDXT3 && format != cCRNFmtDXT5) {
            throw "Unsupported image format " + format + " for " + filename;
        }
        width = Module._crn_get_width(src, srcSize);
        height = Module._crn_get_height(src, srcSize);
        levels = Module._crn_get_levels(src, srcSize);
        dstSize = Module._crn_get_uncompressed_size(src, srcSize, 0);
        dst = Module._malloc(dstSize);

        var totalSize = 0;
        var bytesPerPixel = format == cCRNFmtDXT1 ? 0.5 : 1;
        for(i = 0; i < levels; ++i) {
            totalSize += width * height * bytesPerPixel;
            width *= 0.5;
            height *= 0.5;
            width = Math.max(width, 4);
            height = Math.max(height, 4);
        }

        width = Module._crn_get_width(src, srcSize);
        height = Module._crn_get_height(src, srcSize);

        var ret = new Uint8Array(totalSize);
        var retIndex = 0;

        for(i = 0; i < levels; ++i) {
            if(i) {
                dstSize = Module._crn_get_uncompressed_size(src, srcSize, i);
            }
            Module._crn_decompress(src, srcSize, dst, dstSize, i);
            ret.set(Module.HEAPU8.subarray(dst, dst+dstSize), retIndex);
            retIndex += dstSize;

            width *= 0.5;
            height *= 0.5;
        }
        
        Module._free(src);
        Module._free(dst);

        return ret;
    }

    //===
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    //===

onmessage = function(msg) {
  var start = Date.now();
  var data = deCrunch(new Uint8Array(msg.data.data), msg.data.filename);
  postMessage({
    filename: msg.data.filename,
    data: data,
    callbackID: msg.data.callbackID,
    time: Date.now() - start
  });
};