/*

 * csum-file.c

 *

 * Copyright (C) 2005 Linus Torvalds

 *

 * Simple file write infrastructure for writing SHA1-summed

 * files. Useful when you write a file that you want to be

 * able to verify hasn't been messed with afterwards.

 */

#include "git-compat-util.h"

#include "csum-file.h"

#include "git-zlib.h"

#include "hash.h"

#include "progress.h"

static void verify_buffer_or_die(struct hashfile *f,

         const void *buf,

         unsigned int count)

{

  ssize_t ret = read_in_full(f->check_fd, f->check_buffer, count);

  if (ret < 0)

    die_errno("%s: sha1 file read error", f->name);

  if ((size_t)ret != count)

    die("%s: sha1 file truncated", f->name);

  if (memcmp(buf, f->check_buffer, count))

    die("sha1 file '%s' validation error", f->name);

}

static void flush(struct hashfile *f, const void *buf, unsigned int count)

{

  if (0 <= f->check_fd && count)

    verify_buffer_or_die(f, buf, count);

  if (write_in_full(f->fd, buf, count) < 0) {

    if (errno == ENOSPC)

      die("sha1 file '%s' write error. Out of diskspace", f->name);

    die_errno("sha1 file '%s' write error", f->name);

  }

  f->total += count;

  display_throughput(f->tp, f->total);

}

void hashflush(struct hashfile *f)

{

  unsigned offset = f->offset;

  if (offset) {

    if (!f->skip_hash)

      git_hash_update(&f->ctx, f->buffer, offset);

    flush(f, f->buffer, offset);

    f->offset = 0;

  }

}

void free_hashfile(struct hashfile *f)

{

  free(f->buffer);

  free(f->check_buffer);

  free(f);

}

int finalize_hashfile(struct hashfile *f, unsigned char *result,

          enum fsync_component component, unsigned int flags)

{

  int fd;

  hashflush(f);

  if (f->skip_hash)

    hashclr(f->buffer, f->algop);

  else

    git_hash_final(f->buffer, &f->ctx);

  if (result)

    hashcpy(result, f->buffer, f->algop);

  if (flags & CSUM_HASH_IN_STREAM)

    flush(f, f->buffer, f->algop->rawsz);

  if (flags & CSUM_FSYNC)

    fsync_component_or_die(component, f->fd, f->name);

  if (flags & CSUM_CLOSE) {

    if (close(f->fd))

      die_errno("%s: sha1 file error on close", f->name);

    fd = 0;

  } else

    fd = f->fd;

  if (0 <= f->check_fd) {

    char discard;

    int cnt = read_in_full(f->check_fd, &discard, 1);

    if (cnt < 0)

      die_errno("%s: error when reading the tail of sha1 file",

          f->name);

    if (cnt)

      die("%s: sha1 file has trailing garbage", f->name);

    if (close(f->check_fd))

      die_errno("%s: sha1 file error on close", f->name);

  }

  free_hashfile(f);

  return fd;

}

void discard_hashfile(struct hashfile *f)

{

  if (0 <= f->check_fd)

    close(f->check_fd);

  if (0 <= f->fd)

    close(f->fd);

  free_hashfile(f);

}

void hashwrite(struct hashfile *f, const void *buf, unsigned int count)

{

  while (count) {

    unsigned left = f->buffer_len - f->offset;

    unsigned nr = count > left ? left : count;

    if (f->do_crc)

      f->crc32 = crc32(f->crc32, buf, nr);

    if (nr == f->buffer_len) {

      /*

       * Flush a full batch worth of data directly

       * from the input, skipping the memcpy() to

       * the hashfile's buffer. In this block,

       * f->offset is necessarily zero.

       */

      if (!f->skip_hash)

        git_hash_update(&f->ctx, buf, nr);

      flush(f, buf, nr);

    } else {

      /*

       * Copy to the hashfile's buffer, flushing only

       * if it became full.

       */

      memcpy(f->buffer + f->offset, buf, nr);

      f->offset += nr;

      left -= nr;

      if (!left)

        hashflush(f);

    }

    count -= nr;

    buf = (char *) buf + nr;

  }

}

struct hashfile *hashfd_check(const struct git_hash_algo *algop,

            const char *name)

{

  int sink, check;

  struct hashfile *f;

  sink = xopen("/dev/null", O_WRONLY);

  check = xopen(name, O_RDONLY);

  f = hashfd(algop, sink, name);

  f->check_fd = check;

  f->check_buffer = xmalloc(f->buffer_len);

  return f;

}

static struct hashfile *hashfd_internal(const struct git_hash_algo *algop,

          int fd, const char *name,

          struct progress *tp,

          size_t buffer_len)

{

  struct hashfile *f = xmalloc(sizeof(*f));

  f->fd = fd;

  f->check_fd = -1;

  f->offset = 0;

  f->total = 0;

  f->tp = tp;

  f->name = name;

  f->do_crc = 0;

  f->skip_hash = 0;

  f->algop = unsafe_hash_algo(algop);

  f->algop->init_fn(&f->ctx);

  f->buffer_len = buffer_len;

  f->buffer = xmalloc(buffer_len);

  f->check_buffer = NULL;

  return f;

}

struct hashfile *hashfd(const struct git_hash_algo *algop,

      int fd, const char *name)

{

  /*

   * Since we are not going to use a progress meter to

   * measure the rate of data passing through this hashfile,

   * use a larger buffer size to reduce fsync() calls.

   */

  return hashfd_internal(algop, fd, name, NULL, 128 * 1024);

}

struct hashfile *hashfd_throughput(const struct git_hash_algo *algop,

           int fd, const char *name, struct progress *tp)

{

  /*

   * Since we are expecting to report progress of the

   * write into this hashfile, use a smaller buffer

   * size so the progress indicators arrive at a more

   * frequent rate.

   */

  return hashfd_internal(algop, fd, name, tp, 8 * 1024);

}

void hashfile_checkpoint_init(struct hashfile *f,

            struct hashfile_checkpoint *checkpoint)

{

  memset(checkpoint, 0, sizeof(*checkpoint));

  f->algop->init_fn(&checkpoint->ctx);

}

void hashfile_checkpoint(struct hashfile *f, struct hashfile_checkpoint *checkpoint)

{

  hashflush(f);

  checkpoint->offset = f->total;

  git_hash_clone(&checkpoint->ctx, &f->ctx);

}

int hashfile_truncate(struct hashfile *f, struct hashfile_checkpoint *checkpoint)

{

  off_t offset = checkpoint->offset;

  if (ftruncate(f->fd, offset) ||

      lseek(f->fd, offset, SEEK_SET) != offset)

    return -1;

  f->total = offset;

  git_hash_clone(&f->ctx, &checkpoint->ctx);

  f->offset = 0; /* hashflush() was called in checkpoint */

  return 0;

}

void crc32_begin(struct hashfile *f)

{

  f->crc32 = crc32(0, NULL, 0);

  f->do_crc = 1;

}

uint32_t crc32_end(struct hashfile *f)

{

  f->do_crc = 0;

  return f->crc32;

}

int hashfile_checksum_valid(const struct git_hash_algo *algop,

          const unsigned char *data, size_t total_len)

{

  unsigned char got[GIT_MAX_RAWSZ];

  struct git_hash_ctx ctx;

  size_t data_len = total_len - algop->rawsz;

  algop = unsafe_hash_algo(algop);

  if (total_len < algop->rawsz)

    return 0; /* say "too short"? */

  algop->init_fn(&ctx);

  git_hash_update(&ctx, data, data_len);

  git_hash_final(got, &ctx);

  return hasheq(got, data + data_len, algop);

}