Hello everyone,
I am trying to write a code for my assignment in ID3 version 2 to read some data from an mp3 file. I found some information on the internet and I put together a program. I am beginner in programming and I can not find my mistake. The output is odd, the numbers of the version are not printed and also on the final print parts there are introduced some blank lines. I tried to flush it at the end maybe I was missing something in the buffer but the result is the same. Any help would be appreciated, thank you in advance for your time and effort to my question.
Here is the code:
[
I am trying to write a code for my assignment in ID3 version 2 to read some data from an mp3 file. I found some information on the internet and I put together a program. I am beginner in programming and I can not find my mistake. The output is odd, the numbers of the version are not printed and also on the final print parts there are introduced some blank lines. I tried to flush it at the end maybe I was missing something in the buffer but the result is the same. Any help would be appreciated, thank you in advance for your time and effort to my question.
Here is the code:
[
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <unistd.h>
typedef struct{
unsigned char header_id[3]; /* We indicate that this mp3 file is ID3 format 3 bytes */
uint8_t major_version; /* We set the size and type of unsigned integer of length 8 bits >to the Major Version, unsigned int minimum value is 0 */
uint8_t revision_number; /* We set the size and type of unsigned integer of length 8 >bits to the Revision Number, unsigned int minimum value is 0 */
unsigned char flags; /* We indicate two flag bytes, we use unsigned characters so they >can take values 0 - 255 and not -128 up to 127*/
uint32_t size; /* We the size is indicated by 4 bytes = 32 bits */
}mp3_Header;
typedef struct{
uint32_t extended_size;
unsigned char number_flags;
unsigned char extended_flags;
}mp3_Extended_Header;
typedef struct{
unsigned char frame_id[4];
uint32_t frame_size;
unsigned char frame_flags[2];
}mp3_Frame;
int main (int argc, char *argv[])
{
char a[] = "silence.mp3";
if ( argc != 1 ) /* Input from user argc should be 1 for correct
* execution. The argument count >variable
* stores the number of arguments plus one. >*/
{
/*We print argv[0], if the program that user has chosen for
* execution it is not correct as input if has more inputs*/
printf( "Please choose one file: %s <silence.mp3> \n", argv[0] );
}
else
{
mp3_Header first;
mp3_Extended_Header second;
mp3_Frame third;
unsigned char loop_memory[4], memory[4], new_flagg[2], characters;
int i,b=1;
unsigned long length_of_data = 0;
FILE *file; /* A file pointer is a variable of type FILE,
* we declare a file pointer.*/
file = fopen("silence.mp3", "rb"); /* Open the file
* silence.mp3 in
* "reading" mode "r". */
if (file == NULL)
{
/* If the file could not open for a variety of reasons
* the program should inform us by print the document
* and exit.*/
printf( "I couldn't open: %s for reading.\n", a );
exit(0);
}
else
{
/*Set the pointer at the possition at the beggining of the file,
* if the procedure is correct it will return 0 if not it will return -1. */
if ((int)fseek((FILE *) file, (long int) 0 , (int) SEEK_SET) == -1)
{
fprintf(stderr, "Not able to fseek at possition 0");
return EXIT_FAILURE;
}
/* The function fread() will read 4 bytes of data, each of them in size
* of 1 byte long and they will be stored in memory (givven name) . */
if ( (size_t) fread( (void *) memory , (size_t) 4 , (size_t) 1 , (FILE *) file) !=1)
{
printf("Could not read the file\n");
exit (0);
}
/* I will copy the string from location (memory) to the destination tag_id from first typedef stuct */
strncpy( (char *) first.header_id , (char *) memory , (size_t) 4);
if ( (size_t) fread( (void *) &first.major_version , (size_t) 1 , (size_t) 1 , (FILE *) file) != 1)
{
printf("Could not read the major_version\n");
exit (0);
}
if ( (size_t) fread( (void *) &first.revision_number , (size_t) 1, (size_t) 1 , (FILE *) file) != 1)
{
printf("Could not read the revision_number\n");
exit (0);
}
/* Read the total size of the header */
if ( (size_t) fread( (void *) memory , (size_t) sizeof(first.size) , (size_t) 1 , (FILE *) file) != 1)
{
printf("Could not read memory\n");
exit (0);
}
/* We break down the packet in bytes and allocate the bytes in memory in a sequence.
* After the first sequence is stored for the rest we have to shift them by one possition.
* Because the first bit determines the sign on the character/ intiger and we have set it to possitive.
* We shift the possition every 7 bits because 1 byte has 8 bits - 1 the sign ( + , - ). */
first.size = (memory[3] & 0xFF) |
((memory[2] & 0xFF) << 7 ) |
((memory[1] & 0xFF) << 14 ) |
((memory[0] & 0xFF) << 21 );
/* Store temporarilly the length of the data */
length_of_data = first.size;
/* Print the data that we have collect so far */
((int) fprintf( stdout , "%s version %d . %d\t Size %d\n", first.header_id , first.major_version , first.revision_number , first.size));
/* At this point we want to make sure that the whole header has been executed correctly */
if (( first.flags & (01000000) ) == 01000000 )
{
/* Extended Header 6 Bytes */
if ( (size_t) fread( (void *) memory , (size_t) sizeof(second.extended_size) , (size_t) 1 , (FILE *) file ) != 1)
{
printf("Could not read Memory\n");
exit (0);
}
/* Break down the packet in pieces and extrac the data */
second.extended_size = (memory[3] & 0xFF) |
((memory[2] & 0xFF) << 7 ) |
((memory[1] & 0xFF) << 14 ) |
((memory[0] & 0xFF) << 21 );
if ( (size_t) fread( (void *) &second.number_flags , (size_t) 1 , (size_t) 1 , (FILE *) file ) !=1)
{
printf("Could not read Number of Flags\n");
exit (0);
}
if ( (size_t) fread( (void *) &second.extended_flags , (size_t) 1 , (size_t) 1 , (FILE *) file ) !=1)
{
printf("Could not read Extended Flags\n");
exit (0);
}
fprintf( stdout,"Extended header size: %d\n", second.extended_size);
/* From the stored value we substract the Extended Header */
length_of_data = length_of_data - second.extended_size;
/* Reposition the seek pointer after the Extended Header */
if ((int)fseek ((FILE *) file , (long int) second.extended_size + 10 , (int) SEEK_SET ) == -1)
{
fprintf(stderr, "Not able at second.extended_size possition");
return EXIT_FAILURE;
}
}
else
{
/* If process has been executed correclty proceed and place reader after Extended Header (10 bytes) */
if ((int)fseek ((FILE *) file , (long int) 10 , (int) SEEK_SET ) == -1)
{
fprintf(stderr, "Not able to fseek at possition 10");
return EXIT_FAILURE;
}
}
while(b!=0) /* Read one by one character until the end of file, again and again. */
{
if ( (size_t) fread( (void *) loop_memory , (size_t) 4 , (size_t) 1 , (FILE *) file ) !=1)
{
printf("Could not read Header_id_1 \n");
exit (0);
}
strncpy( (char *) third.frame_id , (char *) loop_memory , (size_t) 4 );
if ( (size_t) fread( (void *) memory , (size_t) sizeof(third.frame_size) , (size_t) 1 , (FILE *) file ) !=1)
{
printf("Could not read Memory\n");
exit (0);
}
/* Extract data and store them */
third.frame_size = (memory[3] & 0xFF) |
((memory[2] & 0xFF) << 7 ) |
((memory[1] & 0xFF) << 14 ) |
((memory[0] & 0xFF) << 21 );
if ( (size_t) fread( (void *) new_flagg , (size_t) 2 , (size_t) 1 , (FILE *) file ) !=1)
{
printf("Could not read Memory\n");
exit (0);
}
strncpy( (char *) third.frame_flags , (char *) new_flagg , (size_t) 2 );
/* Print inforamtion of Frames */
printf("Third Part Frame id : %s Frame Size : %d Flags : ", third.frame_id , third.frame_size );
/* Compare the strings */
if ( strncmp( (char *) third.frame_id , "TPE1" , (size_t) 4 ) == 0 )
{
for ( i = 1; i <= third.frame_size; i++ )
{
characters = fgetc(file);
printf( "%c" , characters );
}
printf("\n");
}
else if ( strncmp( (char *) third.frame_id , "TALB" , (size_t) 4 ) == 0 )
{
for ( i=1 ; i <= third.frame_size; i++ )
{
characters = fgetc(file);
printf( "%c" , characters );
}
printf("\n");
}
else if ( strncmp ( (char *) third.frame_id , "TYER" , (size_t) 4 ) == 0 )
{
for ( i = 1; i <= third.frame_size; i++ )
{
characters = fgetc(file);
printf( "%c" , characters );
}
printf("\n");
}
else if ( strncmp ( (char *) third.frame_id , "TCON" , (size_t) 4 ) == 0 )
{
for ( i = 1; i <= third.frame_size; i++ )
{
characters = fgetc(file);
printf( "%c" , characters );
}
printf("\n");
}
else if ( strncmp ( (char *) third.frame_id , "TRCK" , (size_t) 4 ) == 0 )
{
for ( i = 1; i <= third.frame_size; i++ )
{
characters = fgetc(file);
printf( "%c" , characters );
}
printf("\n");
}
else if ( strncmp ( (char *) third.frame_id , "TIT2" , (size_t) 4 ) == 0 )
{
for ( i = 1; i <= third.frame_size; i++ )
{
characters = fgetc(file);
printf( "%c" , characters );
}
printf("\n");
}
else
{
printf("\n"); b=0;
}
}
if ((int) fflush ((FILE *) file) !=0)
{
printf("Could not Flush buffer at the end");
}
printf("\nFinished Reading, Clossing silence.mp3 file! Goodbye!\n");
fclose(file);
}
}
return 0;
}
]