diff options
Diffstat (limited to 'id3v2.c')
| -rw-r--r-- | id3v2.c | 245 |
1 files changed, 245 insertions, 0 deletions
@@ -0,0 +1,245 @@ +/* + * A simple id3 tag reader + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ + +#include <stdio.h> +#include <stdlib.h> +#include <stdint.h> +#include <string.h> + +#define MP3FILE "song2.mp3" + +struct HEADERV2 +{ + uint8_t id[3]; + uint8_t ver[2]; + uint8_t flags; + uint8_t size[4]; + uint32_t tagsize; /* does NOT include 10 byte header */ +} __attribute__((__packed__)); + +struct HEADERFRAME +{ + uint8_t id[4]; + uint8_t size[4]; + uint8_t flags[2]; + uint32_t framesize; +} __attribute__((__packed__)); + +struct HEADERV1 +{ + uint8_t id[3]; + uint8_t title[30]; + uint8_t artist[30]; + uint8_t album[30]; + uint8_t year[4]; + uint8_t comment[30]; + uint8_t genre; +} __attribute__((__packed__)); + +int synchsafe(int in); +int unsynchsafe(int in); +void readid3v2header(FILE *f, struct HEADERV2 *header); +void printid3v2headerinfo(struct HEADERV2 *header); +void readid3v2frames(FILE *f, struct HEADERV2 *header); +void printid3v2frameinfo(struct HEADERFRAME *frame); +void readid3v1header(FILE *f, struct HEADERV1 *header); +void printid3v1headerinfo(struct HEADERV1 *header); + +int +main(void) +{ + printf("parsing mp3 file %s\n", MP3FILE); + FILE *f = fopen(MP3FILE, "rb"); + if (!f) + { + fprintf(stderr, "fopen failed on %s\n", MP3FILE); + exit(1); + } + struct HEADERV2 *headerv2 = malloc(sizeof(struct HEADERV2)); + if (!headerv2) + { + fprintf(stderr, "malloc failed\n"); + exit(1); + } + struct HEADERV1 *headerv1 = malloc(sizeof(struct HEADERV1)); + if (!headerv1) + { + fprintf(stderr, "malloc failed\n"); + free(headerv2); + exit(1); + } + readid3v1header(f, headerv1); + printid3v1headerinfo(headerv1); + puts(""); + readid3v2header(f, headerv2); + printid3v2headerinfo(headerv2); + puts(""); + readid3v2frames(f, headerv2); + fclose(f); + free(headerv2); + free(headerv1); + return 0; +} + +int +synchsafe(int in) // not used yet +{ + int out, mask = 0x7F; + + while (mask ^ 0x7FFFFFFF) + { + out = in & ~mask; + out <<= 1; + out |= in & mask; + mask = ((mask + 1) << 8) - 1; + in = out; + } + + return out; +} + +int +unsynchsafe(int in) // not used yet +{ + int out = 0, mask = 0x7F000000; + + while (mask) + { + out >>= 1; + out |= in & mask; + mask >>= 8; + } + + return out; +} + +void +readid3v1header(FILE *f, struct HEADERV1 *header) +{ + /* read 128 byte id3v1 header */ + fpos_t oldpos; + /* save our file position */ + fgetpos(f, &oldpos); + + fseek(f, -128L, SEEK_END); + fread(header, 1, 128, f); + + /* restore our file position */ + fsetpos(f, &oldpos); + + +} + +void +printid3v1headerinfo(struct HEADERV1 *header) +{ + printf("TAG v1 header data\n"); + char title[31]; + char artist[31]; + char album[31]; + char year[5]; + char comment[31]; + strncpy(title, (char *)header->title, 30); + strncpy(artist, (char *)header->artist, 30); + strncpy(album, (char *)header->album, 30); + strncpy(year, (char *)header->year, 4); + strncpy(comment, (char *)header->comment, 30); + printf("title:\t%s\n", title); + printf("artist:\t%s\n", artist); + printf("album:\t%s\n", album); + printf("year:\t%c%c%c%c\n", year[0], year[1], year[2], year[3]); + printf("comment:\t%s\n", comment); +} + +void +readid3v2header(FILE *f, struct HEADERV2 *header) +{ + /* + * read 10 byte id3v2 header + * 3 bytes->id + * 2 bytes->version + * 1 bytes->flags + * 4 bytes->size + * the size is encoded into 4 bytes as a synchsafe integer, the most significant bit is ignored + * so we need to convert it + */ + fread(header, 1, 10, f); + /* + * the tag size does NOT include the 10 byte header + * so it is safe to read tagsize bytes from the file + * to obtain the entire header + */ + header->tagsize = header->size[0] << 21 | + header->size[1] << 14 | + header->size[2] << 7 | + header->size[3]; +} + +void +printid3v2headerinfo(struct HEADERV2 *header) +{ + puts("TAGv2 header raw bytes"); + int i; + printf("id:\t"); + for (i = 0; i < 3; i++) + printf("%02X ", header->id[i]); + printf("(%c%c%c)\n", header->id[0], header->id[1], header->id[2]); + printf("ver:\t"); + for (i = 0; i < 2; i++) + printf("%02X ", header->ver[i]); + puts(""); + + printf("flags:\t"); + printf("%02X\n", header->flags); + printf("size:\t"); + for (i = 0; i < 4; i++) + printf("%02X ", header->size[i]); + printf("(%u bytes)\n", header->tagsize); + +} + +void +readid3v2frames(FILE *f, struct HEADERV2 *header) +{ + /* we read at absolute most header->tagsize bytes */ + size_t bytesread = 0; + struct HEADERFRAME *frame = malloc(sizeof(struct HEADERFRAME)); + bytesread += fread(frame, 1, 10, f); + frame->framesize = frame->size[0] << 21 | + frame->size[1] << 14 | + frame->size[2] << 7 | + frame->size[3]; + + printid3v2frameinfo(frame); + free(frame); +} + +void +printid3v2frameinfo(struct HEADERFRAME *frame) +{ + puts("TAGv2 frame raw bytes"); + int i; + printf("id:\t"); + for (i = 0; i < 4; i++) + printf("%02X ", frame->id[i]); + printf("(%c%c%c%c)\n", frame->id[0], frame->id[1], frame->id[2], frame->id[3]); + printf("size:\t"); + for (i = 0; i < 4; i++) + printf("%02X ", frame->size[i]); + printf("(%u bytes)\n", frame->framesize); + +} |