implementing internet radio: trying to open '.au' file in c - c

Question

I am trying to implement an 'internet radio' in C. This requires a server that keeps on playing an audio file continuously and whenever a client request arrives, the server creates a thread that delivers the audio file to the user. The server , when started, spawns a thread that keeps on writing from an audio file onto a global buffer space and the user corresponding buffers keep on reading from the global buffer space and keep on sending the audio file in 'chunks' to the user. And the user tries to play the audio file through the help of '/dev/audio' (I am using ubuntu).
The problem is that when I try to open a '.au' file using 'open' function on the server, a file descriptor of 0 is assigned. So, I am unable to pull the contents out of the audio file and send it to the client(Rather whatever I type on the terminal is sent to the client).
Is there some way of open '.au' files with the 'open' function in C?? If not, then what file extensions does 'open' function support and what can I do, i.e., what type of file extension should I use to make the 'open' function open the file and send to the user?

Answer 1

assure you are using open file mode of binary - IE. given_mode = "rb" where r means read and b means binary - following code reads a binary file and outputs the first few bytes - enjoy
// gcc -o read_binary_au_file read_binary_au_file.c
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
int main() {
const char * given_mode = "rb";
const char * given_filename = "/home/scott/Documents/data/audio/sample.au";
FILE * fh;
fh = fopen(given_filename, given_mode);
if (fh == NULL) {
fprintf(stderr, "ERROR - failed to open file %s in mode %s\n",
given_filename, given_mode);
return (-2);
}
// --- identify file size --- //
off_t file_size;
struct stat stat_struct; // data structure to be returned from call to fstat on file descriptor
int fd = fileno(fh); // get file descriptor from file handle
if ((fstat(fd, & stat_struct) != 0) || (! S_ISREG(stat_struct.st_mode))) {
fprintf(stderr, "ERROR - failed to stat file");
return (-3);
}
file_size = stat_struct.st_size;
printf("file_size %lu\n", file_size);
// --- now read data from the binary file --- //
unsigned long MAX_READ_CHARS = 4096;
unsigned long desired_num_bytes_to_read = (file_size > MAX_READ_CHARS) ? MAX_READ_CHARS : file_size;
char * mem_buffer = malloc(sizeof(char) * desired_num_bytes_to_read);
unsigned long num_bytes_actually_io = 0;
// read initial bytes into memory buffer
num_bytes_actually_io = fread(mem_buffer, sizeof(char), desired_num_bytes_to_read, fh);
if (fclose(fh)) {
fprintf(stderr, "ERROR - failed to close file\n");
return (-4);
}
if (num_bytes_actually_io != desired_num_bytes_to_read) {
fprintf(stderr, "ERROR - failed to read desired_num_bytes_to_read %lu ... instead num_bytes_actually_io %lu\n",
desired_num_bytes_to_read, num_bytes_actually_io);
return (-1);
}
printf("num_bytes_actually_io %lu\n", num_bytes_actually_io);
// ... now do something with mem_buffer which contains data read from binary file
int num_bytes_to_show = 100;
num_bytes_to_show = (num_bytes_actually_io > num_bytes_to_show) ? num_bytes_to_show : num_bytes_actually_io;
printf("\nhere are the first %d characters from given binary file\n", num_bytes_to_show);
printf("-->");
int i = 0;
for (; i < num_bytes_to_show; i++) {
// printf("%c", mem_buffer[i]); // as chars
printf("%x", mem_buffer[i]); // as hex
}
printf("<--");
printf("\n");
free(mem_buffer);
printf("\nprocessing complete\n");
return 0;
}