Plays Interplay's ACM files in SDL2

play_acm.c

#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <SDL2/SDL.h>
#include <dataio/BigEndian.h>
#include <acm/libacm.h>

/* Written circa 2014 by grepwood@sucs.org */

/* This program will utilize libacm and some string logic
 * in order to absolutely correctly decode an ACM at all times,
 * without user hints.
 */

// prototype for our audio callback
// see the implementation for more information
 
// variable declarations
static uint8_t *audio_pos; // global pointer to the audio buffer to be played
static uint32_t audio_len; // remaining length of the sample we have to play

// audio callback function
// here you have to copy the data of your audio buffer into the
// requesting audio buffer (stream)
// you should only copy as much as the requested length (len)
void my_audio_callback(void *userdata, Uint8 *stream, int len) {
	if (audio_len ==0)
		return;
	len = ( len > audio_len ? audio_len : len );
//SDL_memcpy (stream, audio_pos, len); // simply copy from one buffer into the other
	SDL_MixAudio(stream, audio_pos, len, SDL_MIX_MAXVOLUME);// mix from one buffer into another

	audio_pos += len;
	audio_len -= len;
}

char * decode_file_mem(const char *fn, unsigned * wavsize);
 
int main(int argc, char* argv[]){
	static uint32_t wav_length;
	static uint8_t *wav_buffer;
	static SDL_AudioSpec wav_spec;
	uint32_t wavsize;
	char * fn2 = NULL;
	SDL_RWops * WavFromACM;
	if (SDL_Init(SDL_INIT_AUDIO) < 0) {
		return 1;
	}
/* Convert the ACM to WAV */
	fn2 = decode_file_mem(argv[1],&wavsize);
	WavFromACM = SDL_RWFromConstMem(fn2,wavsize);
/* Load the WAV
   the specs, length and buffer of our wav are filled
*/	if(SDL_LoadWAV_RW(WavFromACM,1,&wav_spec,&wav_buffer, &wav_length) == NULL) {
		free(fn2);
		return 2;
	}
// set the callback function
	wav_spec.callback = my_audio_callback;
	wav_spec.userdata = NULL;
// set our global static variables
	audio_pos = wav_buffer; // copy sound buffer
	audio_len = wav_length; // copy file length
/* Open the audio device */
	if ( SDL_OpenAudio(&wav_spec, NULL) < 0 ){
		fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError());
		free(fn2);
		exit(-1);
	}
/* Start playing */
	SDL_PauseAudio(0);

// wait until we're don't playing
	while ( audio_len > 0 ) {
		SDL_Delay(100);
	}
// shut everything down
	SDL_CloseAudio();
	SDL_FreeWAV(wav_buffer);
	FILE * dotwav = fopen("HAKUN.wav","wb");
	fwrite(fn2,wavsize,1,dotwav);
	fclose(dotwav);
	free(fn2);
	return 0;
}