/* Compile with: cc bdb-get.c -ldb */
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <db.h>

static DB_ENV *env = NULL;
static DB *db = NULL;
static DBT dkey, ddata;

static void
dberr(const char *msg, int rc)
{
    fprintf(stderr, "%s: %s\n", msg, db_strerror(rc));
}

static void
cleanup()
{
    int rc;
    free(ddata.data);
    if (db)
        if (rc = db->close(db, 0))
            dberr("cleanup: DB->close failed", rc);
    if (env)
        if (rc = env->close(env, 0))
            dberr("cleanup: DB_ENV->close failed", rc);
}

static void
stdfatal(const char *msg)
{
    perror(msg);
    cleanup();
    exit(EXIT_FAILURE);
}

static void
dbfatal(const char *msg, int rc)
{
    dberr(msg, rc);
    cleanup();
    exit(EXIT_FAILURE);
}

static int
digittoint(int c)
{
    if ('0' <= c && c <= '9')
        return c - '0';
    if ('A' <= c && c <= 'Z')
        return c - 'A' + 10;
    if ('a' <= c && c <= 'z')
        return c - 'a' + 10;
    abort();
}

int
main(int argc, char **argv)
{
    if (argc != 4) {
        fprintf(stderr, "usage: %s <db-home> <db-name> <hex-key>\n", argv[0]);
        exit(EXIT_FAILURE);
    }
    const char *home = argv[1];
    const char *name = argv[2];
    const char *key = argv[3];
    unsigned char *data;
    if (key[0] == '0' && key[1] == 'x')
        key += 2;
    if (strlen(key) % 2) {
        fprintf(stderr, "Invalid key, not even sized\n");
        cleanup();
        exit(EXIT_FAILURE);
    }

    dkey.size = dkey.ulen = strlen(key) / 2;
    dkey.data = data = malloc(dkey.ulen);
    if (!data)
        stdfatal("malloc failed");
    while (isxdigit(key[0]) && isxdigit(key[1])) {
        *data++ = digittoint(key[0]) * 16 + digittoint(key[1]);
        key += 2;
    }

    int rc;
    if (rc = db_env_create(&env, 0))
        dbfatal("db_env_create failed", rc);
    if (rc = env->open(env, home, 0, 0))
        dbfatal("DB_ENV->open failed", rc);
    if (rc = db_create(&db, env, 0))
        dbfatal("db_create failed", rc);
    if (rc = db->open(db, NULL, name, NULL, DB_UNKNOWN, DB_RDONLY, 0))
        dbfatal("DB->open failed", rc);

    ddata.flags = DB_DBT_MALLOC;
    if (rc = db->get(db, NULL, &dkey, &ddata, 0))
        dbfatal("DB->get failed", rc);

    if (fwrite(ddata.data, 1, ddata.size, stdout) != ddata.size)
        stdfatal("fwrite failed");

    cleanup();
    exit(EXIT_SUCCESS);
}