/*

 * Copyright (c) 2005, 2006 Rene Scharfe

 */

#include "builtin.h"

#include "commit.h"

#include "tar.h"

static const char builtin_get_tar_commit_id_usage[] =

"git get-tar-commit-id";

/* ustar header + extended global header content */

#define RECORDSIZE  (512)

#define HEADERSIZE (2 * RECORDSIZE)

int cmd_get_tar_commit_id(int argc, const char **argv UNUSED, const char *prefix)

{

  char buffer[HEADERSIZE];

  struct ustar_header *header = (struct ustar_header *)buffer;

  char *content = buffer + RECORDSIZE;

  const char *comment;

  ssize_t n;

  long len;

  char *end;

  BUG_ON_NON_EMPTY_PREFIX(prefix);

  if (argc != 1)

    usage(builtin_get_tar_commit_id_usage);

  n = read_in_full(0, buffer, HEADERSIZE);

  if (n < 0)

    die_errno("git get-tar-commit-id: read error");

  if (n != HEADERSIZE)

    die_errno("git get-tar-commit-id: EOF before reading tar header");

  if (header->typeflag[0] != TYPEFLAG_GLOBAL_HEADER)

    return 1;

  errno = 0;

  len = strtol(content, &end, 10);

  if (errno == ERANGE || end == content || len < 0)

    return 1;

  if (!skip_prefix(end, " comment=", &comment))

    return 1;

  len -= comment - content;

  if (len < 1 || !(len % 2) ||

      hash_algo_by_length((len - 1) / 2) == GIT_HASH_UNKNOWN)

    return 1;

  if (write_in_full(1, comment, len) < 0)

    die_errno("git get-tar-commit-id: write error");

  return 0;

}