chip8.c

编译后直接运行的ＭＰ３播放器全部Ｃ语言源代码 一个包含FAT文件系统、系统引导 Boot、FLASH Driver等内容的

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id: chip8.c,v 1.6 2004/02/21 22:30:07 hohensoh Exp $
 *
 * Orginal from Vision-8 Emulator / Copyright (C) 1997-1999  Marcel de Kogel
 * Modified for Archos by Blueloop ([e-mail])
 *
 * All files in this archive are subject to the GNU General Public License.
 * See the file COPYING in the source tree root for full license agreement.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/
#include "plugin.h"

/* Only build for (correct) target */
#ifdef HAVE_LCD_BITMAP 
#ifndef SIMULATOR /* not unless lcd_blit() is implemented and mp3_xx stubbed */

static struct plugin_api* rb; /* here is a global api struct pointer */
unsigned char lcd_framebuf[8][64]; /* frame buffer in hardware fomat */

typedef unsigned char byte;                     /* sizeof(byte)==1          */
typedef unsigned short word;                    /* sizeof(word)>=2          */

struct chip8_regs_struct
{
 byte alg[16];                                  /* 16 general registers     */
 byte delay,sound;                              /* delay and sound timer    */
 word i;                                        /* index register           */
 word pc;                                       /* program counter          */
 word sp;                                       /* stack pointer            */
};

static struct chip8_regs_struct chip8_regs;

#define chip8_iperiod 10                        /* number of opcodes per    */
                                                /* timeslice (1/50sec.)     */
static byte chip8_key_pressed;
static byte chip8_keys[16];                     /* if 1, key is held down   */
static byte chip8_display[64*32];               /* 0xff if pixel is set,    */
                                                /* 0x00 otherwise           */
static byte chip8_mem[4096];                    /* machine memory. program  */
                                                /* is loaded at 0x200       */

#define read_mem(a)     (chip8_mem[(a)&4095])
#define write_mem(a,v)  (chip8_mem[(a)&4095]=(v))

static byte chip8_running;                     /* Flag for End-of-Emulation */

#define get_reg_offset(opcode)          (chip8_regs.alg+(opcode>>8))
#define get_reg_value(opcode)           (*get_reg_offset(opcode))
#define get_reg_offset_2(opcode)        (chip8_regs.alg+((opcode>>4)&0x0f))
#define get_reg_value_2(opcode)         (*get_reg_offset_2(opcode))

typedef void (*opcode_fn) (word opcode);
typedef void (*math_fn) (byte *reg1,byte reg2);

static bool is_playing;

/* one frame of bitswapped mp3 data */
static unsigned char beep[]={255,
223, 28, 35,  0,192,210, 35,226, 72,188,242,  1,128,166, 16, 68,146,252,151, 19,
 10,180,245,127, 96,184,  3,184, 30,  0,118, 59,128,121,102,  6,212,  0, 97,  6,
 42, 65, 28,134,192,145, 57, 38,136, 73, 29, 38,132, 15, 21, 70, 91,185, 99,198,
 15,192, 83,  6, 33,129, 20,  6, 97, 33,  4,  6,245,128, 92,  6, 24,  0, 86,  6,
 56,129, 44, 24,224, 25, 13, 48, 50, 82,180, 11,251,106,249, 59, 24, 82,175,223,
252,119, 76,134,120,236,149,250,247,115,254,145,173,174,168,180,255,107,195, 89,
 24, 25, 48,131,192, 61, 48, 64, 10,176, 49, 64,  1,152, 50, 32,  8,140, 48, 16,
  5,129, 51,196,187, 41,177, 23,138, 70, 50,  8, 10,242, 48,192,  3,248,226,  0,
 20,100, 18, 96, 41, 96, 78,102,  7,201,122, 76,119, 20,137, 37,177, 15,132,224,
 20, 17,191, 67,147,187,116,211, 41,169, 63,172,182,186,217,155,111,140,104,254,
111,181,184,144, 17,148, 21,101,166,227,100, 86, 85, 85, 85}; 

/* callback to request more mp3 data */
void callback(unsigned char** start, int* size)
{
    *start = beep; /* give it the same frame again */
    *size = sizeof(beep);
}

/****************************************************************************/
/* Turn sound on                                                            */
/****************************************************************************/
static void chip8_sound_on (void) 
{
    if (!is_playing)
        rb->mp3_play_pause(true); /* kickoff audio */
}

/****************************************************************************/
/* Turn sound off                                                           */
/****************************************************************************/
static void chip8_sound_off (void) 
{ 
    if (!is_playing)
        rb->mp3_play_pause(false); /* pause audio */
}

static void op_call (word opcode)
{
    chip8_regs.sp--;
    write_mem (chip8_regs.sp,chip8_regs.pc&0xff);
    chip8_regs.sp--;
    write_mem (chip8_regs.sp,chip8_regs.pc>>8);
    chip8_regs.pc=opcode;
}

static void op_jmp (word opcode)
{
    chip8_regs.pc=opcode;
}

static void op_key (word opcode)
{
    byte key_value,cp_value;
    if ((opcode&0xff)==0x9e)
        cp_value=1;
    else if ((opcode&0xff)==0xa1)
        cp_value=0;
    else
        return;
    key_value=chip8_keys[get_reg_value(opcode)&0x0f];
    if (cp_value==key_value)
        chip8_regs.pc+=2;
}

static void op_skeq_const (word opcode)
{
    if (get_reg_value(opcode)==(opcode&0xff))
        chip8_regs.pc+=2;
}

static void op_skne_const (word opcode)
{
    if (get_reg_value(opcode)!=(opcode&0xff))
        chip8_regs.pc+=2;
}

static void op_skeq_reg (word opcode)
{
    if (get_reg_value(opcode)==get_reg_value_2(opcode))
        chip8_regs.pc+=2;
}

static void op_skne_reg (word opcode)
{
    if (get_reg_value(opcode)!=get_reg_value_2(opcode))
        chip8_regs.pc+=2;
}

static void op_mov_const (word opcode)
{
    *get_reg_offset(opcode)=opcode&0xff;
}

static void op_add_const (word opcode)
{
    *get_reg_offset(opcode)+=opcode&0xff;
}

static void op_mvi (word opcode)
{
    chip8_regs.i=opcode;
}

static void op_jmi (word opcode)
{
    chip8_regs.pc=opcode+chip8_regs.alg[0];
}

static void op_rand (word opcode)
{
    *get_reg_offset(opcode)=rb->rand()&(opcode&0xff);
}

static void math_or (byte *reg1,byte reg2)
{
    *reg1|=reg2;
}

static void math_mov (byte *reg1,byte reg2)
{
    *reg1=reg2;
}

static void math_nop (byte *reg1,byte reg2)
{
    (void)reg1;
    (void)reg2;
}

static void math_and (byte *reg1,byte reg2)
{
    *reg1&=reg2;
}

static void math_xor (byte *reg1,byte reg2)
{
 *reg1^=reg2;
}

static void math_add (byte *reg1,byte reg2)
{
    word tmp;
    tmp=*reg1+reg2;
    *reg1=(byte)tmp;
    chip8_regs.alg[15]=tmp>>8;
}

static void math_sub (byte *reg1,byte reg2)
{
    word tmp;
    tmp=*reg1-reg2;
    *reg1=(byte)tmp;
    chip8_regs.alg[15]=((byte)(tmp>>8))+1;
}

static void math_shr (byte *reg1,byte reg2)
{
    (void)reg2;
    chip8_regs.alg[15]=*reg1&1;
    *reg1>>=1;
}

static void math_shl (byte *reg1,byte reg2)
{
    (void)reg2;
    chip8_regs.alg[15]=*reg1>>7;
    *reg1<<=1;
}

static void math_rsb (byte *reg1,byte reg2)
{
    word tmp;
    tmp=reg2-*reg1;
    *reg1=(byte)tmp;
    chip8_regs.alg[15]=((byte)(tmp>>8))+1;
}

static void op_system (word opcode)
{
    switch ((byte)opcode)
    {
        case 0xe0:
            rb->memset (chip8_display,0,sizeof(chip8_display));
            break;
        case 0xee:
            chip8_regs.pc=read_mem(chip8_regs.sp)<<8;
            chip8_regs.sp++;
            chip8_regs.pc+=read_mem(chip8_regs.sp);
            chip8_regs.sp++;
            break;
    }
}

static void op_misc (word opcode)
{
    byte *reg,i,j;
    reg=get_reg_offset(opcode);
    switch ((byte)opcode)
    {
        case 0x07:
            *reg=chip8_regs.delay;
            break;
        case 0x0a:
            if (chip8_key_pressed)
                *reg=chip8_key_pressed-1;
            else
                chip8_regs.pc-=2;
            break;
        case 0x15:
            chip8_regs.delay=*reg;
            break;
        case 0x18:
            chip8_regs.sound=*reg;
            if (chip8_regs.sound)
                chip8_sound_on();
            break;
        case 0x1e:
            chip8_regs.i+=(*reg);
            break;
        case 0x29:
            chip8_regs.i=((word)(*reg&0x0f))*5;
            break;
        case 0x33:
            i=*reg;
            for (j=0;i>=100;i-=100)
                j++;
            write_mem (chip8_regs.i,j);
            for (j=0;i>=10;i-=10)
                j++;
            write_mem (chip8_regs.i+1,j);
            write_mem (chip8_regs.i+2,i);
            break;
        case 0x55: