path: root/mp3_afh.c

/* SPDX-License-Identifier: GPL-2.0 */

/** \file mp3_afh.c para_server's mp3 audio format handler */

/*
 * This file is based in part on mp3tech.c and mp3tech.h, Copyright (C)
 * 2000-2001 Cedric Tefft <cedric@earthling.net>, which in turn is based
 * in part on
 *
 *	* MP3Info 0.5 by Ricardo Cerqueira <rmc@rccn.net>
 *	* MP3Stat 0.9 by Ed Sweetman <safemode@voicenet.com> and
 *			 Johannes Overmann <overmann@iname.com>
 */

#include <id3tag.h>

#include "para.h"
#include "error.h"
#include "afh.h"
#include "string.h"
#include "fd.h"

/*
 * MIN_CONSEC_GOOD_FRAMES defines how many consecutive valid MP3 frames we need
 * to see before we decide we are looking at a real MP3 file
 */
#define MIN_CONSEC_GOOD_FRAMES 4
#define FRAME_HEADER_SIZE 4
#define MIN_FRAME_SIZE 21

struct mp3header {
	unsigned long sync;
	unsigned int version;
	unsigned int layer;
	unsigned int crc;
	unsigned int bitrate;
	unsigned int freq;
	unsigned int padding;
	unsigned int mode;
};

static const int frequencies[3][4] = {
	{22050,24000,16000,50000}, /* MPEG 2.0 */
	{44100,48000,32000,50000}, /* MPEG 1.0 */
	{11025,12000,8000,50000} /* MPEG 2.5 */
};

static const int mp3info_bitrate[2][3][14] = {
{ /* MPEG 2.0 */
	{32,48,56,64,80,96,112,128,144,160,176,192,224,256}, /* layer 1 */
	{8,16,24,32,40,48,56,64,80,96,112,128,144,160}, /* layer 2 */
	{8,16,24,32,40,48,56,64,80,96,112,128,144,160} /* layer 3 */
},

{ /* MPEG 1.0 */
	{32,64,96,128,160,192,224,256,288,320,352,384,416,448}, /* layer 1 */
	{32,48,56,64,80,96,112,128,160,192,224,256,320,384}, /* layer 2 */
	{32,40,48,56,64,80,96,112,128,160,192,224,256,320} /* layer 3 */
}
};

static const int frame_size_index[] = {24000, 72000, 72000};

static char *get_utf8(id3_ucs4_t const *string)
{
	if (!string)
		return NULL;
	return (char *)id3_ucs4_utf8duplicate(string);
}

static char *get_stringlist(union id3_field *field)
{
	unsigned int k, nstrings = id3_field_getnstrings(field);
	char *result = NULL;

	for (k = 0; k < nstrings; k++) {
		char *tmp = (char *)get_utf8(id3_field_getstrings(field, k));
		if (result) {
			char *tmp2 = result;
			result = make_message("%s %s", tmp2, tmp);
			free(tmp);
			free(tmp2);
		} else
			result = tmp;
	}
	return result;
}

static char *get_string(union id3_field *field)
{
	id3_ucs4_t const *string = id3_field_getfullstring(field);

	return get_utf8(string);
}

static char *get_strings(struct id3_frame *fr)
{
	for (int j = 0; j < fr->nfields; j++) {
		union id3_field *field = id3_frame_field(fr, j);
		enum id3_field_type type = id3_field_type(field);

		if (type == ID3_FIELD_TYPE_STRINGLIST)
			return get_stringlist(field);
		if (type == ID3_FIELD_TYPE_STRINGFULL)
			return get_string(field);
	}
	return NULL;
}

/* this only sets values which are undefined so far */
static void parse_frames(struct id3_tag *id3_t, struct taginfo *tags)
{
	int i;

	for (i = 0; i < id3_t->nframes; i++) {
		struct id3_frame *fr = id3_t->frames[i];
		if (!strcmp(fr->id, ID3_FRAME_TITLE)) {
			if (!tags->title)
				tags->title = get_strings(fr);
			continue;
		}
		if (!strcmp(fr->id, ID3_FRAME_ARTIST)) {
			if (!tags->artist)
				tags->artist = get_strings(fr);
			continue;
		}
		if (!strcmp(fr->id, ID3_FRAME_ALBUM)) {
			if (!tags->album)
				tags->album = get_strings(fr);
			continue;
		}
		if (!strcmp(fr->id, ID3_FRAME_YEAR)) {
			if (!tags->year)
				tags->year = get_strings(fr);
			continue;
		}
		if (!strcmp(fr->id, ID3_FRAME_COMMENT)) {
			if (!tags->comment)
				tags->comment = get_strings(fr);
			continue;
		}
	}
}

static int get_id3(unsigned char *map, size_t numbytes,
		struct taginfo *tags)
{
	int ret = 0;
	struct id3_tag *id3_t;

	/* id3v2 tags are usually located at the beginning. */
	id3_t = id3_tag_parse(map, numbytes);
	if (id3_t) {
		parse_frames(id3_t, tags);
		ret |= 2;
		id3_tag_delete(id3_t);
	}
	/* Also look for an id3v1 tag at the end of the file. */
	if (numbytes >= 128) {
		id3_t = id3_tag_parse(map + numbytes - 128, 128);
		if (id3_t) {
			parse_frames(id3_t, tags);
			ret |= 1;
			id3_tag_delete(id3_t);
		}
	}
	return ret;
}

/*
 * The two helpers below are called during tag replacement if libid3tag is
 * present. They are implemented and exported in the library but libid3tag.h
 * does not declare them, so we declare them here.
 */

/** \cond libid3tag */

/*
 * To replace a tag with libid3tag one has to pass frames of id3 fields
 * to particular functions of the id3tag library. The various field types
 * specify text encoding, language, string, etc. This function initializes
 * a field to the default value for the given type. It does not allocate
 * memory and always succeeds.
 */
void id3_field_init(union id3_field *field, enum id3_field_type type);

/*
 * Reset a field, deallocating memory if necessary.
 *
 * This first frees any memory already allocated, then calls id3_field_init()
 * to initialize the field, re-using the old field type. The field pointer
 * must not be NULL.
 */
void id3_field_finish(union id3_field *field);

/** \endcond libid3tag */

/*
 * Frames of type ID3_FRAME_COMMENT contain three fields of type language,
 * string, and fullstring. The third field contains the actual comment.
 */
static int set_comment_fields(struct id3_frame *fr, id3_ucs4_t *ucs4_val)
{
	int ret;
	union id3_field *field;

	field = id3_frame_field(fr, 1);
	id3_field_init(field, ID3_FIELD_TYPE_LANGUAGE);

	field = id3_frame_field(fr, 2);
	id3_field_init(field, ID3_FIELD_TYPE_STRING);

	field = id3_frame_field(fr, 3);
	id3_field_init(field, ID3_FIELD_TYPE_STRINGFULL);
	ret = id3_field_setfullstring(field, ucs4_val);
	if (ret < 0)
		return -E_ID3_SETSTRING;
	return 1;
}

/*
 * UCS-4 stands for Universal Character Set where each character uses exactly
 * 32 bits. It is also known as UTF-32, see ISO 10646.
 *
 * We have to use UCS-4 as an intermediate representation because the functions
 * of libid3tag which set the tag content expect an array of UCS-4 characters.
 * Fortunately, libid3tag contains conversion functions from and to UTF-8.
 */
static int replace_tag(char const *id, const char *val, struct id3_tag *id3_t,
		int options)
{
	int ret;
	struct id3_frame *fr;
	union id3_field *field;
	id3_ucs4_t *ucs4_val;

	/* First, detach all frames that match the given id. */
	while ((fr = id3_tag_findframe(id3_t, id, 0))) {
		PARA_INFO_LOG("deleting %s frame\n", id);
		ret = id3_tag_detachframe(id3_t, fr);
		if (ret < 0)
			return -E_ID3_DETACH;
		id3_frame_delete(fr);
	}
	if (!val || !*val)
		return 0;
	fr = id3_frame_new(id);
	PARA_DEBUG_LOG("frame desc: %s, %u fields\n", fr->description, fr->nfields);

	/* Frame 0 contains the encoding. We always use UTF-8. */
	field = id3_frame_field(fr, 0);
	id3_field_init(field, ID3_FIELD_TYPE_TEXTENCODING);
	ret = id3_field_settextencoding(field, ID3_FIELD_TEXTENCODING_UTF_8);
	if (ret < 0)
		return -E_ID3_SETENCODING;
	/* create UCS-4 representation */
	ucs4_val = id3_utf8_ucs4duplicate((const id3_utf8_t *)val);

	if (strcmp(id, ID3_FRAME_COMMENT) == 0)
		ret = set_comment_fields(fr, ucs4_val);
	else {
		/* Non-comment frames contain the value in field 1. */
		field = id3_frame_field(fr, 1);
		if (options & ID3_TAG_OPTION_ID3V1) {
			id3_ucs4_t *ptr[] = {ucs4_val, NULL};
			id3_field_init(field, ID3_FIELD_TYPE_STRINGLIST);
			ret = id3_field_setstrings(field, 1, ptr);
		} else {
			id3_field_init(field, ID3_FIELD_TYPE_STRINGFULL);
			ret = id3_field_setfullstring(field, ucs4_val);
		}
	}
	free(ucs4_val);
	if (ret < 0)
		return -E_ID3_SETSTRING;

	PARA_INFO_LOG("attaching %s frame, value: %s\n", id, val);
	ret = id3_tag_attachframe(id3_t, fr);
	if (ret < 0)
		return -E_ID3_ATTACH;
	return 1;
}

static int replace_tags(struct id3_tag *id3_t, struct taginfo *tags)
{
	int ret, options = id3_tag_options(id3_t, 0, 0);

	ret = replace_tag(ID3_FRAME_ARTIST, tags->artist, id3_t, options);
	if (ret < 0)
		return ret;
	ret = replace_tag(ID3_FRAME_TITLE, tags->title, id3_t, options);
	if (ret < 0)
		return ret;
	ret = replace_tag(ID3_FRAME_ALBUM, tags->album, id3_t, options);
	if (ret < 0)
		return ret;
	ret = replace_tag(ID3_FRAME_YEAR, tags->year, id3_t, options);
	if (ret < 0)
		return ret;
	ret = replace_tag(ID3_FRAME_COMMENT, tags->comment, id3_t, options);
	if (ret < 0)
		return ret;
	return 1;
}

/* id3_tag_delete() does not seem to work due to refcount issues. */
static void free_tag(struct id3_tag *id3_t)
{
	int i, j;

	if (!id3_t)
		return;
	for (i = 0; i < id3_t->nframes; i++) {
		struct id3_frame *fr = id3_t->frames[i];
		for (j = 0; j < fr->nfields; j++) {
			union id3_field *field = &fr->fields[j];
			id3_field_finish(field);
		}
		free(fr);
	}
	free(id3_t->frames);
	free(id3_t);
}

static int mp3_rewrite_tags(const char *map, size_t mapsize,
		struct taginfo *tags, int fd)
{
	int ret;
	id3_length_t old_v2size, new_v2size;
	id3_byte_t v1_buffer[128], *v2_buffer;
	size_t data_sz;
	struct id3_tag *v1_tag = NULL, *v2_tag = NULL;

	if (mapsize >= 128) {
		v1_tag = id3_tag_parse((const id3_byte_t *)map + mapsize - 128,
			128);
		if (v1_tag) {
			PARA_NOTICE_LOG("replacing id3v1 tag\n");
			ret = replace_tags(v1_tag, tags);
			if (ret < 0)
				goto out;
			id3_tag_render(v1_tag, v1_buffer);
		}
	}
	old_v2size = 0;
	v2_tag = id3_tag_parse((const id3_byte_t *)map, mapsize);
	if (v2_tag) {
		PARA_NOTICE_LOG("replacing id3v2 tag\n");
		old_v2size = v2_tag->paddedsize;
	} else {
		PARA_NOTICE_LOG("adding id3v2 tag\n");
		v2_tag = id3_tag_new();
		assert(v2_tag);
	}
	/*
	 * Turn off all options to avoid creating an extended header.  id321
	 * does not understand it.
	 */
	id3_tag_options(v2_tag, ~0U, 0);
	ret = replace_tags(v2_tag, tags);
	if (ret < 0)
		goto out;
	new_v2size = id3_tag_render(v2_tag, NULL);
	v2_buffer = alloc(new_v2size);
	id3_tag_render(v2_tag, v2_buffer);
	PARA_INFO_LOG("writing v2 tag (%lu bytes)\n", new_v2size);
	ret = write_all(fd, (char *)v2_buffer, new_v2size);
	free(v2_buffer);
	if (ret < 0)
		goto out;
	data_sz = mapsize - old_v2size;
	if (v1_tag && data_sz >= 128)
		data_sz -= 128;
	PARA_INFO_LOG("writing data part (%zu bytes)\n", data_sz);
	ret = write_all(fd, map + old_v2size, data_sz);
	if (ret < 0)
		goto out;
	if (v1_tag) {
		PARA_INFO_LOG("writing v1 tag\n");
		ret = write_all(fd, (char *)v1_buffer, 128);
	}
out:
	free_tag(v1_tag);
	free_tag(v2_tag);
	return ret;
}

static int header_frequency(struct mp3header *h)
{
	if (h->version > 2 || h->freq > 3)
		return -E_HEADER_FREQ;
	return frequencies[h->version][h->freq];
}

static const char *header_mode(const struct mp3header *h)
{
	const char * const mode_text[] = {"stereo", "joint stereo",
		"dual channel", "mono"};

	if (h->mode >= ARRAY_SIZE(mode_text))
		return "invalid";
	return mode_text[h->mode];
}

static int header_channels(struct mp3header *h)
{
	if (h->mode > 3)
		return 0;
	if (h->mode < 3)
		return 2;
	return 1;
}

static int header_bitrate(struct mp3header *h)
{
	if (!h->layer || h->layer > 3 || h->bitrate > 14 || !h->bitrate)
		return -E_HEADER_BITRATE;
	return mp3info_bitrate[h->version & 1][3 - h->layer][h->bitrate - 1];
}

static int frame_length(struct mp3header *header)
{
	int hb, hf = header_frequency(header);

	if (hf < 0)
		return hf;
	hb = header_bitrate(header);
	if (hb < 0)
		return hb;
	if (header->sync != 0xFFE || header->layer > 3)
		return -E_FRAME;
	return frame_size_index[3 - header->layer] *
		((header->version & 1) + 1) * hb / hf
		+ header->padding;
}

static int compare_headers(struct mp3header *h1, struct mp3header *h2)
{
	if ((*(unsigned int*)h1) == (*(unsigned int*)h2))
		return 1;
	if ((h1->version == h2->version) &&
			(h1->layer == h2->layer) &&
			(h1->crc == h2->crc) &&
			(h1->freq == h2->freq) &&
			(h1->mode == h2->mode))
		return 1;
	return 0;
}

/*
 * get next MP3 frame header.
 *
 * On success, the header frame length is returned and the given header
 * structure that is filled in.  A return value of zero means that we did not
 * retrieve a valid frame header, and a negative return value indicates an
 * error.
 */
static int get_header(unsigned char *map, size_t numbytes, off_t *fpos,
	struct mp3header *header)
{
	int fl, ret;

	if (*fpos + FRAME_HEADER_SIZE > numbytes) {
		*fpos = numbytes - 1;
		header->sync = 0;
		return 0;
	}
	header->layer = (map[*fpos + 1] >> 1) & 3;
	header->sync = (((int)map[*fpos]<<4) | ((int)(map[*fpos + 1]&0xE0)>>4));
	if (map[*fpos + 1] & 0x10)
		header->version = (map[*fpos + 1] >> 3) & 1;
	else
		header->version = 2;
	if ((header->sync != 0xFFE) || (header->layer != 1)) {
		ret = 0;
		header->sync = 0;
		goto out;
	}
	header->crc = map[*fpos + 1] & 1;
	header->bitrate = (map[*fpos + 2] >> 4) & 0x0F;
	header->freq = (map[*fpos + 2] >> 2) & 0x3;
	header->padding = (map[*fpos + 2] >>1) & 0x1;
	header->mode = (map[*fpos + 3] >> 6) & 0x3;
	fl = frame_length(header);
	ret = (fl >= MIN_FRAME_SIZE)? fl : -E_FRAME_LENGTH;
out:
	*fpos += FRAME_HEADER_SIZE;
	return ret;
}

/*
 * find the next mp3 header
 *
 * Return the length of the next frame header or zero if the end of the file is
 * reached.
 */
static int seek_next_header(unsigned char *map, size_t numbytes, off_t *fpos,
	struct mp3header *result)
{
	int k, l = 0, first_len;
	struct mp3header h, h2;
	long valid_start = 0;

	for (; *fpos < numbytes; (*fpos)++) {
		if (map[*fpos] != 0xff)
			continue;
		valid_start = *fpos;
		first_len = get_header(map, numbytes, fpos, &h);
		if (first_len <= 0)
			continue;
		*fpos += first_len - FRAME_HEADER_SIZE;
		for (k = 1; k < MIN_CONSEC_GOOD_FRAMES; k++) {
			if ((l = get_header(map, numbytes, fpos, &h2)) <= 0)
				break;
			if (!compare_headers(&h, &h2))
				break;
			*fpos += l - FRAME_HEADER_SIZE;
		}
		if (k == MIN_CONSEC_GOOD_FRAMES) {
			*fpos = valid_start;
			*result = h2;
			return first_len;
		}
	}
	return 0;
}

static int find_valid_start(unsigned char *map, size_t numbytes, off_t *fpos,
	struct mp3header *header)
{
	int frame_len;

	frame_len = get_header(map, numbytes, fpos, header);
	if (frame_len < 0)
		return frame_len;
	if (!frame_len) {
		frame_len = seek_next_header(map, numbytes, fpos, header);
		if (frame_len <= 0)
			return frame_len;
	} else
		*fpos -= FRAME_HEADER_SIZE;
	if (frame_len <= 1)
		return -E_FRAME_LENGTH;
	return frame_len;
}

static int read_info(unsigned char *map, size_t numbytes,
		struct afh_info *afhi)
{
	uint64_t freq_sum = 0, br_sum = 0;
	int fl = 0, ret, len = 0, old_br = -1, vbr = 0;
	struct timeval total_time = {0, 0};
	unsigned chunk_table_size = 1000; /* gets increased on demand */
	off_t fpos = 0;
	struct mp3header header;
	const char *tag_versions[] = {"no", "id3v1", "id3v2", "id3v1+id3v2"};

	afhi->chunks_total = 0;
	afhi->chunk_table = arr_alloc(chunk_table_size, sizeof(uint32_t));
	while (1) {
		int freq, br;
		struct timeval tmp, cct; /* current chunk time */
		fpos += len;
		len = find_valid_start(map, numbytes, &fpos, &header);
		if (len <= 0) {
			size_t end;
			ret = -E_MP3_INFO;
			if (!afhi->chunks_total)
				goto err_out;
			end = afhi->chunk_table[afhi->chunks_total - 1] + fl;
			afhi->chunk_table[afhi->chunks_total]
				= PARA_MIN(end, numbytes);
			break;
		}
		ret = header_frequency(&header);
		if (ret < 0)
			continue;
		freq = ret;
		ret = header_bitrate(&header);
		if (ret < 0)
			continue;
		br = ret;
		ret = frame_length(&header);
		if (ret < 0)
			continue;
		fl = ret;
		tmp.tv_sec = fl - header.padding;
		tmp.tv_usec = 0;
		tv_divide(br * 125, &tmp, &cct);
		tv_add(&cct, &total_time, &tmp);
		total_time = tmp;
		if (afhi->chunks_total >= chunk_table_size) {
			chunk_table_size *= 2;
			afhi->chunk_table = arr_realloc(afhi->chunk_table,
				chunk_table_size, sizeof(uint32_t));
		}
		afhi->chunk_table[afhi->chunks_total] = fpos;
		afhi->chunks_total++;
		freq_sum += freq;
		br_sum += br;
		if (afhi->chunks_total != 1 && old_br != br)
			vbr = 1;
		old_br = br;
	}
	ret = -E_MP3_INFO;
	if (!freq_sum || !br_sum)
		goto err_out;
	afhi->bitrate = br_sum / afhi->chunks_total;
	afhi->frequency = freq_sum / afhi->chunks_total;
	afhi->channels = header_channels(&header);
	afhi->seconds_total = (tv2ms(&total_time) + 500) / 1000;
	tv_divide(afhi->chunks_total, &total_time, &afhi->chunk_tv);
	PARA_DEBUG_LOG("%" PRIu32 " chunks, each %lums\n", afhi->chunks_total,
		tv2ms(&afhi->chunk_tv));
	set_max_chunk_size(afhi);
	ret = get_id3(map, numbytes, &afhi->tags);
	afhi->techinfo = make_message("%cbr, %s, %s tags", vbr? 'v' : 'c',
		header_mode(&header), tag_versions[ret]);
	return 1;
err_out:
	free(afhi->chunk_table);
	return ret;
}

/*
 * Read mp3 information from audio file
 */
static int mp3_get_file_info(char *map, size_t numbytes, struct afh_info *afhi)
{
	int ret;

	ret = read_info((unsigned char *)map, numbytes, afhi);
	if (ret < 0)
		return ret;
	if (afhi->chunks_total == 0)
		return -E_MP3_INFO;
	return 1;
}

static const char * const mp3_suffixes[] = {"mp3", NULL};

/** The mp3 audio format handler. */
const struct audio_format_handler mp3_afh = {
	.get_file_info = mp3_get_file_info,
	.suffixes = mp3_suffixes,
	.rewrite_tags = mp3_rewrite_tags,
};