C Standard Library File I/O - moerjielovecookie

1 Function Introduction#

1.1 Library Variables#

Variable	Description
size_t	An unsigned integer type, the result of the sizeof keyword, representing the size of an object
FILE	A file stream type, suitable for storing file stream information

1.2 Library Macros#

Macro	Description
NULL	Null pointer constant
EOF	A negative integer indicating the end of a file
stderr, stdin, stdout	Pointers to FILE type, corresponding to standard error, standard input, and standard output streams

1.3 Library Functions#

1.3.1 fopen#

FILE *fopen(const char *filename, const char *mode) 
// Opens the file pointed to by filename with the given mode mode

mode	Description
"r"	Opens a file for reading; the file must exist
"w"	Creates an empty file for writing. If a file with the same name exists, its contents are deleted
"a"	Appends to a file; write operations append data to the end of the file, creating the file if it does not exist
"r+"	Opens a file for update; can read and write. The file must exist
"w+"	Creates an empty file for reading and writing
"a+"	Opens a file for reading and appending

The function returns a FILE pointer, or NULL on failure

1.3.2 fread#

Declaration:

size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream)
// ptr: Pointer to a memory block with a minimum size of size*nmemb bytes
// size: Size of each element to be read, in bytes
// nmemb: Number of elements
// stream: Pointer to a FILE object that specifies an input stream

The number of successfully read elements is returned as a size_t object

1.3.3 fwrite#

size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream)
// ptr: Pointer to the array of elements to be written
// size: Size of each element to be written, in bytes
// nmemb: Number of elements
// stream: Pointer to a FILE object that specifies an output stream

1.3.4 fseek#

int fseek(FILE *stream, long int offset, int whence)
// stream: Pointer to a FILE object
// offset: Offset in bytes relative to whence
// whence: Indicates the position from which to add the offset

whence is generally one of the following three constants

Constant	Description
SEEK_SET	Beginning of the file
SEEK_CUR	Current position of the file pointer
SEEK_END	End of the file

Returns the number of bytes from the whence position

1.3.5 ftell#

long int ftell(FILE *stream)

Returns the current value of the position identifier

2 Using the C Standard Library to Read TS Files and Write to TXT#

#include <stdio.h>
#include <stdlib.h>

int main() {
    FILE *fileInput, *fileOutput;
    unsigned char buffer[188];  // The standard packet size for TS streams is 188 bytes
    size_t bytesRead;

    // Open TS file
    fileInput = fopen("/home/sawen/my_test_pcie/test.ts", "rb");
    if (!fileInput) {
        perror("Failed to open input file");
        return EXIT_FAILURE;
    } else {
        printf("Input file opened successfully.\n");
    }

    // Check file size
    fseek(fileInput, 0, SEEK_END);
    long fileSize = ftell(fileInput);
    rewind(fileInput);
    if (fileSize == 0) {
        printf("Input file is empty.\n");
        fclose(fileInput);
        return EXIT_FAILURE;
    } else {
        printf("Input file size: %ld bytes.\n", fileSize);
    }

    // Open TXT file
    fileOutput = fopen("output.txt", "w");
    if (!fileOutput) {
        perror("Failed to open output file");
        fclose(fileInput);
        return EXIT_FAILURE;
    } else {
        printf("Output file opened successfully.\n");
    }

    // Read data and write to TXT file
    int packetCount = 0;
    while ((bytesRead = fread(buffer, 1, sizeof(buffer), fileInput)) > 0) {
        for (size_t i = 0; i < bytesRead; ++i) {
            fprintf(fileOutput, "%02x ", buffer[i]); // Write bytes in hexadecimal format
        }
        fprintf(fileOutput, "\n");  // New line after each TS packet
        packetCount++;
    }

    // Check if any data was read
    if (packetCount == 0) {
        printf("No data read from file.\n");
    } else {
        printf("Processed %d TS packets.\n", packetCount);
    }

    // Close files
    fclose(fileInput);
    fclose(fileOutput);

    printf("Data transfer complete.\n");
    return EXIT_SUCCESS;
}

The output is as follows

You can see that it writes to the txt file in lines of 188 bytes.