capi – C library to read/write DiscoDBs

The C library is the native control application for reading and writing DiscoDBs

Opening a discodb

Likely want to check a few things when opening a ddb file.

static struct ddb *open_discodb(const char *file)
{
    struct ddb *db;
    int fd;
    if (!(db = ddb_new())){
        fprintf(stderr, "Couldn't initialize discodb: Out of memory\n");
        exit(1);
    }
    if ((fd = open(file, O_RDONLY)) == -1){
        fprintf(stderr, "Couldn't open discodb %s\n", file);
        exit(1);
    }
    if (ddb_load(db, fd)){
        const char *err;
        ddb_error(db, &err);
        fprintf(stderr, "Invalid discodb in %s: %s\n", file, err);
        exit(1);
    }
    return db;
}

Adding key/values to a ddb

You’ll need to create a ddb_entry from memory available on the stack or heap. During the ddb_cons_add call, the entries will be duplicated into the discodb and the original stack/heap memory can be reused or freed.

uint64_t flags = 0;
flags |= getenv("DONT_COMPRESS") ? DDB_OPT_DISABLE_COMPRESSION: 0;
flags |= getenv("UNIQUE_ITEMS") ? DDB_OPT_UNIQUE_ITEMS: 0;
flags |= DDB_OPT_UNIQUE_ITEMS;


char key[MAX_KV_SIZE] = "Key\0";
char val[MAX_KV_SIZE] = "Value\0";
struct ddb_entry key_e = {.data = key, .length = strlen(key)};
struct ddb_entry val_e = {.data = val, .length = strlen(val)};


if (ddb_cons_add(db, &key_e, &val_e)){
    fprintf(stderr, "Adding '%s':'%s' failed\n", key, val);
    exit(1);
}


if (!(data = ddb_cons_finalize(db, &size, flags))){
    fprintf(stderr, "Packing the index failed\n");
    exit(1);
}

ddb_cons_free(db);

if (!(out = fopen("/path/to/ddb", "w"))){
    fprintf(stderr, "Opening file %s failed\n", ddbfile);
    exit(1);
}
if (!fwrite(data, size, 1, out)){
    fprintf(stderr, "Writing file %s failed\n", ddbfile);
    exit(1);
}
fflush(out);
fclose(out);
free(data);