packer.c

#define NOB_IMPLEMENTATION
#include "nob.h"

#include "tar.h"

typedef struct {
    Header *items;
    size_t count;
    size_t capacity;
} Headers;

void print_usage(const char *program_name)
{
    fprintf(stderr, "Usage: %s <output.tar>\n", program_name);
}

void octal_field(void *buf, size_t n, size_t value)
{
    snprintf(buf, n, "%0*zo", (int)n - 1, value);
}

void checksum_header(Header *header)
{
    size_t checksum = 0;
    memset(header->checksum, ' ', sizeof(header->checksum));
    Record *record = (void*)header;
    for (size_t i = 0; i < sizeof(record->bytes); ++i) {
        checksum += record->bytes[i];
    }
    octal_field(header->checksum, sizeof(header->checksum), checksum);
}

void make_folder(Headers *headers, const char *folder_path)
{
    Header header = {0};

    snprintf(header.file_path, sizeof(header.file_path), "%s", folder_path);
    octal_field(header.file_size, sizeof(header.file_size), 0);
    octal_field(header.file_mode, sizeof(header.file_mode), 0755);

    checksum_header(&header);
    da_append(headers, header);

    nob_log(INFO, "archived folder `%s`", folder_path);
}

void make_file(Headers *headers, const char *file_path, const char *content)
{
    size_t content_size = strlen(content);

    {
        Header header = {0};

        snprintf(header.file_path, sizeof(header.file_path), "%s", file_path);
        octal_field(header.file_size, sizeof(header.file_size), content_size);
        octal_field(header.file_mode, sizeof(header.file_mode), 0644);

        checksum_header(&header);
        da_append(headers, header);
    }

    {
        Header header = {0};

        assert(content_size <= sizeof(header));

        memcpy(&header, content, content_size);
        da_append(headers, header);
    }

    nob_log(INFO, "archived file `%s`", file_path);
}

int main(int argc, char **argv)
{
    const char *program_name = shift(argv, argc);

    if (argc <= 0) {
        print_usage(program_name);
        fprintf(stderr, "ERROR: no output is provided\n");
        return 1;
    }
    const char *output_path = shift(argv, argc);

    Headers headers = {0};

    make_folder(&headers, "bar/");
    make_file  (&headers, "bar/single_file.txt", "Hello from the manually created tar file\n");
    make_folder(&headers, "bar/empty_folder/");
    make_file  (&headers, "bar/not_empty_folder/single_file_in_not_empty_folder.txt", "Hello from a single file in a not empty folder\n");
    make_file  (&headers, "bar/not_empty_folder/another_file_in_not_empty_folder.txt", "Hello from another file in a not empty folder\n");
    make_folder(&headers, "bar/not_empty_folder/");

    // EOF
    for (size_t i = 0; i < 2; ++i) {
        Header header = {0};

        da_append(&headers, header);
    }

    if (!write_entire_file(output_path, headers.items, headers.count*sizeof(*headers.items))) return 1;
    nob_log(INFO, "created file `%s`", output_path);

    return 0;
}