src/memory.js

"use strict";

/**
 * @constructor
 */
function Memory(buffer, memory_size)
{
    var mem8 = new Uint8Array(buffer),
        mem16 = new Uint16Array(buffer),
        mem8s = new Int8Array(buffer),
        mem32s = new Int32Array(buffer);

    this.mem8 = mem8;
    this.mem16 = mem16;
    this.mem8s = mem8s;
    this.mem32s = mem32s;

    this.buffer = buffer;

    this.size = memory_size;

    // this only supports a 32 bit address space
    var memory_map_registered = new Uint8Array(1 << (32 - MMAP_BLOCK_BITS)),
        memory_map_read = [],
        memory_map_write = [];

    // managed by IO() in io.js
    this.memory_map_registered = memory_map_registered;
    this.memory_map_read = memory_map_read;
    this.memory_map_write = memory_map_write;

    dbg_assert((memory_size & MMAP_BLOCK_SIZE - 1) === 0);
}

// called by all memory reads and writes
Memory.prototype.debug_write = function(addr, size, value)
{
    if(!DEBUG)
    {
        return;
    }

    //dbg_assert(typeof value === "number" && !isNaN(value));
    this.debug_read(addr, size, true);
}

/** @param {boolean=} is_write */
Memory.prototype.debug_read = function(addr, size, is_write)
{
    if(!DEBUG)
    {
        return;
    }

    dbg_assert(typeof addr === "number");
    dbg_assert(!isNaN(addr));
};


Memory.prototype.mmap_read8 = function(addr)
{
    return this.memory_map_read[addr >>> MMAP_BLOCK_BITS](addr);
}

Memory.prototype.mmap_write8 = function(addr, value)
{
    this.memory_map_write[addr >>> MMAP_BLOCK_BITS](addr, value);
}

Memory.prototype.mmap_read32 = function(addr)
{
    var aligned_addr = addr >>> MMAP_BLOCK_BITS,
        size = this.memory_map_registered[aligned_addr],
        fn = this.memory_map_read[aligned_addr];

    if(size & 4)
    {
        return fn(addr);
    }
    else
    {
        return fn(addr) | fn(addr + 1) << 8 | 
                fn(addr + 2) << 16 | fn(addr + 3) << 24;
    }
}

Memory.prototype.mmap_write32 = function(addr, value)
{
    var aligned_addr = addr >>> MMAP_BLOCK_BITS,
        size = this.memory_map_registered[aligned_addr],
        fn = this.memory_map_write[aligned_addr];

    if(size & 4)
    {
        fn(addr, value);
    }
    else
    {
        fn(addr, value & 0xFF);
        fn(addr + 1, value >> 8 & 0xFF);
        fn(addr + 2, value >> 16 & 0xFF);
        fn(addr + 3, value >>> 24);
    }
}

/**
 * @param addr {number}
 */
Memory.prototype.read8 = function(addr)
{
    this.debug_read(addr, 1);

    if(this.memory_map_registered[addr >>> MMAP_BLOCK_BITS])
    {
        return this.mmap_read8(addr);
    }
    else
    {
        return this.mem8[addr];
    }
};

/**
 * @param addr {number}
 */
Memory.prototype.read16 = function(addr)
{
    this.debug_read(addr, 2);

    if(this.memory_map_registered[addr >>> MMAP_BLOCK_BITS])
    {
        return this.mmap_read8(addr) | this.mmap_read8(addr + 1) << 8;
    }
    else
    {
        return this.mem8[addr] | this.mem8[addr + 1] << 8;
    }
};

/**
 * @param addr {number}
 */
Memory.prototype.read_aligned16 = function(addr)
{
    this.debug_read(addr << 1, 2);

    if(this.memory_map_registered[addr >>> MMAP_BLOCK_BITS - 1])
    {
        addr <<= 1;
        return this.mmap_read8(addr) | this.mmap_read8(addr + 1) << 8;
    }
    else
    {
        return this.mem16[addr];
    }
};

/**
 * @param addr {number}
 */
Memory.prototype.read32s = function(addr)
{
    this.debug_read(addr, 4);

    if(this.memory_map_registered[addr >>> MMAP_BLOCK_BITS])
    {
        return this.mmap_read32(addr);
    }
    else
    {
        return this.mem8[addr] | this.mem8[addr + 1] << 8 | 
            this.mem8[addr + 2] << 16 | this.mem8[addr + 3] << 24;
    }
};

/**
 * @param addr {number}
 */
Memory.prototype.read_aligned32 = function(addr)
{
    this.debug_read(addr << 2, 4);

    if(this.memory_map_registered[addr >>> MMAP_BLOCK_BITS - 2])
    {
        return this.mmap_read32(addr << 2);
    }
    else
    {
        return this.mem32s[addr];
    }
};

/**
 * @param addr {number}
 * @param value {number}
 */
Memory.prototype.write8 = function(addr, value)
{
    this.debug_write(addr, 1, value);

    if(this.memory_map_registered[addr >>> MMAP_BLOCK_BITS])
    {
        this.mmap_write8(addr, value);
    }
    else
    {
        this.mem8[addr] = value;
    }
};

/**
 * @param addr {number}
 * @param value {number}
 */
Memory.prototype.write16 = function(addr, value)
{
    this.debug_write(addr, 2, value);

    if(this.memory_map_registered[addr >>> MMAP_BLOCK_BITS])
    {
        this.mmap_write8(addr, value & 0xff);
        this.mmap_write8(addr + 1, value >> 8 & 0xff);
    }
    else
    {
        this.mem8[addr] = value;
        this.mem8[addr + 1] = value >> 8;
    }
};

/**
 * @param addr {number}
 * @param value {number}
 */
Memory.prototype.write_aligned16 = function(addr, value)
{
    this.debug_write(addr << 1, 2, value);

    if(this.memory_map_registered[addr >>> MMAP_BLOCK_BITS - 1])
    {
        addr <<= 1;
        this.mmap_write8(addr, value & 0xff);
        this.mmap_write8(addr + 1, value >> 8 & 0xff);
    }
    else
    {
        this.mem16[addr] = value;
    }
};

/**
 * @param addr {number}
 * @param value {number}
 */
Memory.prototype.write32 = function(addr, value)
{
    this.debug_write(addr, 4, value);

    if(this.memory_map_registered[addr >>> MMAP_BLOCK_BITS])
    {
        this.mmap_write32(addr, value);
    }
    else
    {
        this.mem8[addr] = value;
        this.mem8[addr + 1] = value >> 8;
        this.mem8[addr + 2] = value >> 16;
        this.mem8[addr + 3] = value >> 24;
    }
};

Memory.prototype.write_aligned32 = function(addr, value)
{
    this.debug_write(addr << 2, 4, value);

    if(this.memory_map_registered[addr >>> MMAP_BLOCK_BITS - 2])
    {
        this.mmap_write32(addr << 2, value);
    }
    else
    {
        this.mem32s[addr] = value;
    }
};

/**
 * @param offset {number}
 * @param blob {Array.<number>}
 */
Memory.prototype.write_blob = function(blob, offset)
{
    dbg_assert(blob && blob.length);
    this.mem8.set(blob, offset);
};

/**
 * zero byte terminated string
 */
Memory.prototype.read_string = function(addr)
{
    var str = "",
        data_byte;

    while(data_byte = this.read8(addr))
    {
        str += String.fromCharCode(data_byte);
        addr++;
    }

    return str;
};

Memory.prototype.write_string = function(str, addr)
{
    for(var i = 0; i < str.length; i++)
    {
        this.write8(addr + i, str.charCodeAt(i));
    }
};