src/browser/lib.js

"use strict";

(function()
{
    v86util.load_file = load_file;
    v86util.AsyncXHRBuffer = AsyncXHRBuffer;
    v86util.AsyncFileBuffer = AsyncFileBuffer;
    v86util.SyncFileBuffer = SyncFileBuffer;

    /** 
     * @param {?=} progress 
     * @param {?=} headers 
     */
    function load_file(filename, done, progress, headers)
    {
        var http = new XMLHttpRequest();

        http.open("get", filename, true);
        http.responseType = "arraybuffer";

        if(headers)
        {
            var header_names = Object.keys(headers);

            for(var i = 0; i < header_names.length; i++)
            {
                var name = header_names[i];

                http.setRequestHeader(name, headers[name]);
            }
        }

        http.onload = function(e)
        {
            if(http.readyState === 4)
            {
                if(http.status !== 200 && http.status !== 206)
                {
                    console.log("Loading the image `" + filename + "` failed");
                }
                else if(http.response)
                {
                    done(http.response);
                }
            }
        };

        if(progress)
        {
            http.onprogress = function(e)
            {
                progress(e);
            };
        }
        
        http.send(null);
    }

    /**
     * @this {AsyncFileBuffer|AsyncXHRBuffer}
     * Likewise, relies on this.byteLength, this.loaded_blocks and this.block_size
     */
    function async_buffer_set(offset, data, fn)
    {
        console.assert(offset + data.length <= this.byteLength);
        
        var len = data.length;

        // TODO: Unaligned write
        console.assert(offset % this.block_size === 0);
        console.assert(len % this.block_size === 0);
        console.assert(len);

        var start_block = offset / this.block_size;
        var block_count = len / this.block_size;

        for(var i = 0; i < block_count; i++)
        {
            var block = this.loaded_blocks[start_block + i];

            if(block === undefined)
            {
                block = this.loaded_blocks[start_block + i] = new Uint8Array(this.block_size);
            }

            var data_slice = data.subarray(i * this.block_size, (i + 1) * this.block_size);
            block.set(data_slice);

            console.assert(block.byteLength === data_slice.length);
        }

        fn();
    }

    /**
     * Asynchronous access to ArrayBuffer, loading blocks lazily as needed.
     * This is just a prototype and partly incomplete.
     *
     * @constructor
     * @param {string} filename   Name of the file to download parts
     *                            from. Replaces %d with the block number (padded)
     */
    function AsyncXHRBuffer(filename, block_size, size)
    {
        this.filename = filename;
        this.block_size = block_size;
        this.block_count = size / block_size;
        console.assert(this.block_count === (this.block_count | 0));

        this.loaded_blocks = {};
        
        this.byteLength = size;

        this.get_buffer = function(fn)
        {
            // We must download all parts, unlikely a good idea for big files
        };
    }
    AsyncXHRBuffer.prototype.get = function(offset, len, fn)
    {
        console.assert(offset % this.block_size === 0);
        console.assert(len % this.block_size === 0);
        console.assert(len);

        var range_start = offset,
            range_end = offset + len - 1;

        load_file(this.filename, 
            function(buffer)
            {
                var block = new Uint8Array(buffer);
                
                this.handle_read(offset, len, block);
                fn(block);
            }.bind(this), 
            null,
            {
                Range: "bytes=" + range_start + "-" + range_end,
            }
        );
    }
    AsyncXHRBuffer.prototype.set = async_buffer_set;

    AsyncXHRBuffer.prototype.handle_read = function(offset, len, block)
    {
        // Used by AsyncXHRBuffer and AsyncFileBuffer
        // Overwrites blocks from the original source that have been written since
        
        var start_block = offset / this.block_size,
            block_count = len / this.block_size;

        for(var i = 0; i < block_count; i++)
        {
            var written_block = this.loaded_blocks[start_block + i];

            if(written_block)
            {
                block.set(written_block, i * this.block_size);
            }
            //else
            //{
            //    var cached = this.loaded_blocks[start_block + i] = new Uint8Array(this.block_size);
            //    cached.set(block.subarray(i * this.block_size, (i + 1) * this.block_size));
            //}
        }
    };

    /**
     * Synchronous access to File, loading blocks from the input type=file
     * The whole file is loaded into memory during initialisation
     *
     * @constructor
     */
    function SyncFileBuffer(file)
    {
        var PART_SIZE = 4 << 20,
            ready = false,
            me = this;

        this.byteLength = file.size;

        if(file.size > (1 << 30))
        {
            console.log("Warning: Allocating buffer of " + (file.size >> 20) + " MB ...");
        }

        var buffer = new ArrayBuffer(file.size),
            pointer = 0,
            filereader = new FileReader();

        this.load = function()
        {
            // Here: Read all parts sequentially
            // Other option: Read all parts in parallel
            filereader.onload = function(e)
            {
                new Uint8Array(buffer, pointer).set(new Uint8Array(e.target.result));
                pointer += PART_SIZE;
                next();
            };

            next();

            function next()
            {
                if(me.onprogress)
                {
                    me.onprogress({
                        loaded: pointer,   
                        total: file.size,
                        lengthComputable: true,
                    });
                }

                if(pointer < file.size)
                {
                    filereader.readAsArrayBuffer(file.slice(pointer, Math.min(pointer + PART_SIZE, file.size)));
                }
                else
                {
                    ready = true;

                    if(me.onload)
                    {
                        me.onload({
                            
                        });
                    }
                }
            }
        }

        this.get = function(offset, len, fn)
        {
            if(ready)
            {
                console.assert(offset + len <= buffer.byteLength);

                fn(new Uint8Array(buffer, offset, len));
            }
            else
            {
                throw "SyncFileBuffer: Wait for ready";
            }
        };

        this.get_buffer = function(fn)
        {
            if(ready)
            {
                fn(buffer);
            }
            else
            {
                throw "SyncFileBuffer: Wait for ready";
            }
        };

        /** @param data {Uint8Array] */
        this.set = function(offset, data, fn)
        {
            if(ready)
            {
                console.assert(offset + data.byteLength <= buffer.byteLength);

                new Uint8Array(buffer, offset, data.byteLength).set(data);
                fn();
            }
            else
            {
                throw "SyncFileBuffer: Wait for ready";
            }
        };
    }

    /**
     * Asynchronous access to File, loading blocks from the input type=file
     *
     * @constructor
     */
    function AsyncFileBuffer(file)
    {
        var BLOCK_SHIFT = 9,
            BLOCK_SIZE = 1 << BLOCK_SHIFT;

        this.file = file;
        this.byteLength = file.size;

        this.block_count = file.size >> BLOCK_SHIFT;
        this.block_size = BLOCK_SIZE;

        this.loaded_blocks = {};

        this.get_buffer = function(fn)
        {
        };

        this.load = function()
        {
            this.onload && this.onload({});
        };
    }

    AsyncFileBuffer.prototype.get = function(offset, len, fn)
    {
        console.assert(offset % this.block_size === 0);
        console.assert(len % this.block_size === 0);
        console.assert(len);

        var fr = new FileReader();

        fr.onload = function(e)
        {
            var buffer = e.target.result;
            var block = new Uint8Array(buffer);

            this.handle_read(offset, len, block);
            fn(block);
        }.bind(this);

        fr.readAsArrayBuffer(this.file.slice(offset, offset + len));
    }
    AsyncFileBuffer.prototype.set = async_buffer_set;
    AsyncFileBuffer.prototype.handle_read = AsyncXHRBuffer.prototype.handle_read;

})();