readid3.c

e1c0df5d-c8bc-48a5-bc02-a2b7c51c0dbf是做mp3的源代码

#include <stdio.h>
#include <string.h>

#define TITLE 1
#define INTERPRET 2
#define GENRE 3

FILE * infile;
int i, size;
char b;
char buf[512];
char string[60];
char * bufp;
int offset;
int parse_tag(int * offset);

int main()
{
  infile = fopen("test.mp3", "r");
  bufp = buf;
  for (i = 0; i < 512; i++)
  {
    buf[i] = getc(infile);
  }
  fclose(infile);
  if (buf[0]=='I' && buf[1]=='D' && buf[2]=='3') printf("ID3-Tag gefunden!\n");
  size = buf[6] << 21 | buf[7] << 14 | buf[8] << 7 | buf[9];
  printf("Gr鲞e: %x\n", size);
  offset = 10;
  while (offset < 512)
  {
    size = parse_tag(&offset);
    switch (size)
    {
      case 0:
        printf ("Genre: %s\n", string);
	break;
      case 1:
        printf("Track: %s\n", string);
	break;
      case 2:
        printf("Album: %s\n", string);
	break;
      case 3:
        printf("Interpret: %s\n", string);
	break;
      case 4:
        printf("Titel: %s\n", string);
	break;
    }
  }

//  for (i=0; i<3; i++) printf("%2x", buf[i]);
}

int parse_tag(int *offset)
{
  int tsize, encoding, numid;
  char fid[5];
  const char valid_tags[] = "TCONTRCKTALBTPE1TIT2";

  numid = -1;
  fid[4]='\0';
  strncpy(fid, &buf[*offset],4);		// get frame identifier as string
//  numid =
  *offset +=  4;
  tsize = ((unsigned char) buf[*offset]) << 21 | ((unsigned char) buf[*offset+1]) << 14 | ((unsigned char) buf[*offset+2]) << 7 | (unsigned char) buf[*offset+3];

  *offset += 6;		// jump over flags...

  char * strpos = strstr(valid_tags,fid);

  if (strpos)
  {
    numid = ((int) strpos - (int) &valid_tags) / 4;
    encoding = buf[*offset];
    if (encoding == 0) *offset += 1; else *offset += 3;
    if (encoding == 0) tsize -= 1; else tsize -= 3;
    for (i=0; i<tsize; i++)
    {
      string[i/(encoding+1)]=buf[*offset+i];
      if (encoding != 0) i++;
    }
    *offset += i;
    string[i/(encoding+1)]='\0';
  }
  else
  { *offset += tsize; }
  return numid;
}