A C program to read and display key metadata of an HDF5 file, including its signature and superblock information

HDF5_Metadata_Reader.c

#include <stdio.h>
#include <string.h>  // For strncmp

#define SIGNATURE_SIZE 8
#define MAX_OFFSET 2048

int main() {
    FILE* file = fopen("data.h5", "rb");
    if (!file) {
        printf("Unable to open file!\n");
        return 1;
    }

    char signature[SIGNATURE_SIZE];
    int offset = 0;
    unsigned char version, size_of_offsets, size_of_lengths;
    unsigned short reserved, group_leaf_node_k, group_internal_node_k;
    unsigned int file_consistency_flags;
    unsigned long long base_address, freespace_info, end_of_file_address, driver_information_block_address;

    // Search for the HDF5 signature
    while (offset <= MAX_OFFSET) {
        if (fseek(file, offset, SEEK_SET) != 0 || fread(signature, sizeof(char), SIGNATURE_SIZE, file) != SIGNATURE_SIZE) {
            printf("File operation error.\n");
            fclose(file);
            return 1;
        }
        
        if (strncmp(signature, "\211HDF\r\n\032\n", SIGNATURE_SIZE) == 0) {
            printf("Found HDF5 signature at offset %d\n", offset);
            break;
        }

        offset *= 2;
        if (offset == 0) offset = 512;
    }

    // Read the superblock
    if (fread(&version, sizeof(unsigned char), 1, file) != 1 ||
        fread(&size_of_offsets, sizeof(unsigned char), 1, file) != 1 ||
        fread(&size_of_lengths, sizeof(unsigned char), 1, file) != 1 ||
        fread(&reserved, sizeof(unsigned short), 1, file) != 1 ||
        fread(&group_leaf_node_k, sizeof(unsigned short), 1, file) != 1 ||
        fread(&group_internal_node_k, sizeof(unsigned short), 1, file) != 1 ||
        fread(&file_consistency_flags, sizeof(unsigned int), 1, file) != 1 ||
        fread(&base_address, sizeof(unsigned long long), 1, file) != 1 ||
        fread(&freespace_info, sizeof(unsigned long long), 1, file) != 1 ||
        fread(&end_of_file_address, sizeof(unsigned long long), 1, file) != 1 ||
        fread(&driver_information_block_address, sizeof(unsigned long long), 1, file) != 1) {
        
        printf("File operation error.\n");
        fclose(file);
        return 1;
    }

    // Output superblock info
    printf("Superblock version: %d\n", version);
    printf("Size of Offsets: %d\n", size_of_offsets);
    printf("Size of Lengths: %d\n", size_of_lengths);
    printf("Group Leaf Node K: %d\n", group_leaf_node_k);
    printf("Group Internal Node K: %d\n", group_internal_node_k);
    printf("File Consistency Flags: %d\n", file_consistency_flags);
    printf("Base Address: %llu\n", base_address);
    printf("Freespace Info: %llu\n", freespace_info);
    printf("End of File Address: %llu\n", end_of_file_address);
    printf("Driver Information Block Address: %llu\n", driver_information_block_address);

    fclose(file);
    return 0;
}

Output example:

Found HDF5 signature at offset 0
Superblock version: 0
Size of Offsets: 0
Size of Lengths: 0
Group Leaf Node K: 2056
Group Internal Node K: 1024
File Consistency Flags: 4096
Base Address: 0
Freespace Info: 18446744073692774400
End of File Address: 302811971583
Driver Information Block Address: 18446744073692774400