francois-berder / fat16

This is a FAT16 driver.

FAT16 driver

This aim of this project is to create a small program able to read FAT16 image on Linux. This project has also been ported to a PIC24, see BoatController. The data folder contains images used to test the program.

Features

The driver can:

• list files in a directory
• read to a file (a file can be opened several times in reading mode)
• write to a file: any previous contents are erased. A file cannot be read while it is opened in write mode.
• append to a file: similar to write mode but any previous content is preserved and writing happen at the end.
• create/delete directories

This driver cannot handle long names.

Names of files and directories must respect the format described here: https://en.wikipedia.org/wiki/8.3_filename. Hence, all valid names can be stored as an array of char of length 13 characters (12 bytes for the filename and one byte for the null character).

Build instructions

make

This creates a shared library libfat16_driver.so in the lib folder. The test suite must be run as root:

sudo ./bin/run_test

Integration in an application

You will need to implement the following functions to construct a struct storage_dev_t:

    int (*read)(void *buffer, uint32_t length);
    int (*read_byte)(void *data);
    int (*write)(const void *buffer, uint32_t length);
    int (*seek)(uint32_t offset);

You will also need to find out where the fat16 partition starts. If it is a FAT16 image, the address is most likely 0. Otherwise, read the MBR to get the first sector of a FAT16 partition, multiplied by 512 (bytes per sector) and pass it to fat16_init.

On some compilers such as Microchip XC16, some features from C99 such as printing uint32_t are not supported so you may have to change the format in debug print.

Examples

Printing content of a file:

void print_file_content(void)
{
    int fd = fat16_open("DATA.TXT", 'r');
    if (fd < 0) {
        fprintf(stderr, "Failed to read DATA.TXT\n");
        return;
    }

    while (1) {
        char buffer[256];
        int i, n;
        n = fat16_read(fd, buffer, sizeof(buffer));
        if (n == 0) {   /* End of file reached */
            break;
        } else if (n < 0) {
            fprintf(stderr, "Error %d while reading\n", -n);
            break;
        } else {
            for (i = 0; i < n; ++i)
                printf("%c", buffer[i]);
        }
    }

    fat16_close(fd);
}

Listing files in root directory:

void list_files(void)
{
    char filename[13];
    uint32_t i = 0;
    while(fat16_ls(&i, filename, "/") == 1) {
        printf("%s\n", filename);
    }
}