mre-mos6502/src/memory.rs

// Copyright (C) 2014 The 6502-rs Developers
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
// 3. Neither the names of the copyright holders nor the names of any
//    contributors may be used to endorse or promote products derived from this
//    software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.

use address::Address;

// JAM: We can probably come up with a better way to represent address ranges.
//      Address range type?
// 
// // Address range -- inclusive on both sides
// pub struct AddressRangeIncl {
//     begin: Address,
//     end: Address,
// }

static ADDR_LO_BARE: u16 = 0x0000;
static ADDR_HI_BARE: u16 = 0xFFFF;

pub static MEMORY_ADDRESS_LO:       Address = Address(ADDR_LO_BARE);
pub static MEMORY_ADDRESS_HI:       Address = Address(ADDR_HI_BARE);
pub static STACK_ADDRESS_LO:        Address = Address(0x0100);
pub static STACK_ADDRESS_HI:        Address = Address(0x01FF);
pub static IRQ_INTERRUPT_VECTOR_LO: Address = Address(0xFFFE);
pub static IRQ_INTERRUPT_VECTOR_HI: Address = Address(0xFFFF);

static MEMORY_SIZE: uint = (ADDR_HI_BARE - ADDR_LO_BARE) as uint + 1u;

pub struct Memory {
    bytes: [u8, ..MEMORY_SIZE]
}

impl Memory {
    pub fn new() -> Memory {
        Memory { bytes: [0, ..MEMORY_SIZE] }
    }
    
    pub fn get_byte(&self, address: &Address) -> u8 {
        self.bytes[address.to_uint()]
    }
    
    // Sets the byte at the given address to the given value and returns the
    // previous value at the address.
    pub fn set_byte(&mut self, address: &Address, value: u8) -> u8 {
        let old_value = self.get_byte(address);
        self.bytes[address.to_uint()] = value;
        
        return old_value;
    }
    
    pub fn is_stack_address(address: &Address) -> bool {
        STACK_ADDRESS_LO <= *address && *address <= STACK_ADDRESS_HI
    }
}