lockstep/app/src/main/cpp/mp3file.cpp

//
// Created by david on 17.05.20.
//

#define LOG_TAG "mp3file"

#include "mp3file.h"
#include <string.h>
#include <cstdlib>
#include "logging.h"

MP3File* mp3file_init(mpg123_handle *handle) {
    MP3File* mp3file = (MP3File *) malloc(sizeof(MP3File));
    if(mp3file == NULL) return NULL;
    memset(mp3file, 0, sizeof(MP3File));
    mp3file->handle = handle;
    return mp3file;
}

void mp3file_delete(MP3File *mp3file) {
    if(mp3file == NULL) return;
    mpg123_close(mp3file->handle);
    mpg123_delete(mp3file->handle);
    if(mp3file->buffer) {
        free(mp3file->buffer);
        mp3file->buffer = 0;
    }
    free(mp3file);
}

MP3File* mp3file_open(const char *filename, int forceEncoding) {
    const char *errorText = "";
#define handleError(text) \
    do { \
        errorText = text; \
        goto on_error; \
    } while(0)

    int err = MPG123_OK;
    mpg123_handle *mh = mpg123_new(NULL, &err);
    if(err != MPG123_OK || mh == NULL) {
        LOGE("mpg123_new() failed: %s", mpg123_plain_strerror(err));
        return NULL;
    }

    MP3File* mp3 = mp3file_init(mh);
    if(mp3 == NULL) handleError("malloc() failed");
    err = mpg123_open(mh, filename);
    if(err != MPG123_OK) handleError("mpg123_open()");

    int encoding;
    err = mpg123_getformat(mh, &mp3->rate, &mp3->channels, &encoding);
    if(err != MPG123_OK) handleError("mpg123_getformat()");
    if(encoding != MPG123_ENC_SIGNED_16) handleError("unknown file encoding");

    if(forceEncoding != 0) {
        encoding = forceEncoding;
    }

    // Ensure that this output format will not change
    // (it could, when we allow it).
    mpg123_format_none(mh);
    err = mpg123_format(mh, mp3->rate, mp3->channels, encoding);
    if(err != MPG123_OK) handleError("could not set mpg123_format()");

    mp3->buffer_size = mpg123_outblock(mh);
    mp3->buffer = (unsigned char*) malloc(mp3->buffer_size);
    if(mp3->buffer == NULL) handleError("malloc() failed");

    mp3->num_samples = mpg123_length(mh);
    mp3->samples_per_frame = mpg123_spf(mh);
    mp3->secs_per_frame = mpg123_tpf(mh);

    if (mp3->num_samples == MPG123_ERR || mp3->samples_per_frame < 0)
        mp3->num_frames = 0;
    else
        mp3->num_frames = mp3->num_samples / mp3->samples_per_frame;

    if (mp3->num_samples == MPG123_ERR || mp3->samples_per_frame < 0 || mp3->secs_per_frame < 0)
        mp3->duration = 0;
    else
        mp3->duration = mp3->num_samples / mp3->samples_per_frame * mp3->secs_per_frame;

    mp3->offset = 0;
    mp3->remaining_samples = (int) mp3->num_samples;
    LOGV("channels: %d rate: %ld num_samples: %ld", mp3->channels, mp3->rate, mp3->num_samples);
    return mp3;

on_error:
    LOGE("%s, err = %s", errorText, mpg123_plain_strerror(err));
    mp3file_delete(mp3);
    return NULL;

#undef handleError
}