/*

 * Copyright (c) 2011, Google Inc.

 */

#include "git-compat-util.h"

#include "convert.h"

#include "environment.h"

#include "repository.h"

#include "object-file.h"

#include "odb.h"

#include "odb/streaming.h"

#include "replace-object.h"

#include "packfile.h"

#define FILTER_BUFFER (1024*16)

/*****************************************************************

 *

 * Filtered stream

 *

 *****************************************************************/

struct odb_filtered_read_stream {

  struct odb_read_stream base;

  struct odb_read_stream *upstream;

  struct stream_filter *filter;

  char ibuf[FILTER_BUFFER];

  char obuf[FILTER_BUFFER];

  int i_end, i_ptr;

  int o_end, o_ptr;

  int input_finished;

};

static int close_istream_filtered(struct odb_read_stream *_fs)

{

  struct odb_filtered_read_stream *fs = (struct odb_filtered_read_stream *)_fs;

  free_stream_filter(fs->filter);

  return odb_read_stream_close(fs->upstream);

}

static ssize_t read_istream_filtered(struct odb_read_stream *_fs, char *buf,

             size_t sz)

{

  struct odb_filtered_read_stream *fs = (struct odb_filtered_read_stream *)_fs;

  size_t filled = 0;

  while (sz) {

    /* do we already have filtered output? */

    if (fs->o_ptr < fs->o_end) {

      size_t to_move = fs->o_end - fs->o_ptr;

      if (sz < to_move)

        to_move = sz;

      memcpy(buf + filled, fs->obuf + fs->o_ptr, to_move);

      fs->o_ptr += to_move;

      sz -= to_move;

      filled += to_move;

      continue;

    }

    fs->o_end = fs->o_ptr = 0;

    /* do we have anything to feed the filter with? */

    if (fs->i_ptr < fs->i_end) {

      size_t to_feed = fs->i_end - fs->i_ptr;

      size_t to_receive = FILTER_BUFFER;

      if (stream_filter(fs->filter,

            fs->ibuf + fs->i_ptr, &to_feed,

            fs->obuf, &to_receive))

        return -1;

      fs->i_ptr = fs->i_end - to_feed;

      fs->o_end = FILTER_BUFFER - to_receive;

      continue;

    }

    /* tell the filter to drain upon no more input */

    if (fs->input_finished) {

      size_t to_receive = FILTER_BUFFER;

      if (stream_filter(fs->filter,

            NULL, NULL,

            fs->obuf, &to_receive))

        return -1;

      fs->o_end = FILTER_BUFFER - to_receive;

      if (!fs->o_end)

        break;

      continue;

    }

    fs->i_end = fs->i_ptr = 0;

    /* refill the input from the upstream */

    if (!fs->input_finished) {

      fs->i_end = odb_read_stream_read(fs->upstream, fs->ibuf, FILTER_BUFFER);

      if (fs->i_end < 0)

        return -1;

      if (fs->i_end)

        continue;

    }

    fs->input_finished = 1;

  }

  return filled;

}

static struct odb_read_stream *attach_stream_filter(struct odb_read_stream *st,

                struct stream_filter *filter)

{

  struct odb_filtered_read_stream *fs;

  CALLOC_ARRAY(fs, 1);

  fs->base.close = close_istream_filtered;

  fs->base.read = read_istream_filtered;

  fs->upstream = st;

  fs->filter = filter;

  fs->base.size = -1; /* unknown */

  fs->base.type = st->type;

  return &fs->base;

}

/*****************************************************************

 *

 * In-core stream

 *

 *****************************************************************/

struct odb_incore_read_stream {

  struct odb_read_stream base;

  char *buf; /* from odb_read_object_info_extended() */

  unsigned long read_ptr;

};

static int close_istream_incore(struct odb_read_stream *_st)

{

  struct odb_incore_read_stream *st = (struct odb_incore_read_stream *)_st;

  free(st->buf);

  return 0;

}

static ssize_t read_istream_incore(struct odb_read_stream *_st, char *buf, size_t sz)

{

  struct odb_incore_read_stream *st = (struct odb_incore_read_stream *)_st;

  size_t read_size = sz;

  size_t remainder = st->base.size - st->read_ptr;

  if (remainder <= read_size)

    read_size = remainder;

  if (read_size) {

    memcpy(buf, st->buf + st->read_ptr, read_size);

    st->read_ptr += read_size;

  }

  return read_size;

}

static int open_istream_incore(struct odb_read_stream **out,

             struct object_database *odb,

             const struct object_id *oid)

{

  struct object_info oi = OBJECT_INFO_INIT;

  struct odb_incore_read_stream stream = {

    .base.close = close_istream_incore,

    .base.read = read_istream_incore,

  };

  struct odb_incore_read_stream *st;

  int ret;

  oi.typep = &stream.base.type;

  oi.sizep = &stream.base.size;

  oi.contentp = (void **)&stream.buf;

  ret = odb_read_object_info_extended(odb, oid, &oi,

              OBJECT_INFO_DIE_IF_CORRUPT);

  if (ret)

    return ret;

  CALLOC_ARRAY(st, 1);

  *st = stream;

  *out = &st->base;

  return 0;

}

/*****************************************************************************

 * static helpers variables and functions for users of streaming interface

 *****************************************************************************/

static int istream_source(struct odb_read_stream **out,

        struct object_database *odb,

        const struct object_id *oid)

{

  struct odb_source *source;

  if (!packfile_store_read_object_stream(out, odb->packfiles, oid))

    return 0;

  odb_prepare_alternates(odb);

  for (source = odb->sources; source; source = source->next)

    if (!odb_source_loose_read_object_stream(out, source, oid))

      return 0;

  return open_istream_incore(out, odb, oid);

}

/****************************************************************

 * Users of streaming interface

 ****************************************************************/

int odb_read_stream_close(struct odb_read_stream *st)

{

  int r = st->close(st);

  free(st);

  return r;

}

ssize_t odb_read_stream_read(struct odb_read_stream *st, void *buf, size_t sz)

{

  return st->read(st, buf, sz);

}

struct odb_read_stream *odb_read_stream_open(struct object_database *odb,

               const struct object_id *oid,

               struct stream_filter *filter)

{

  struct odb_read_stream *st;

  const struct object_id *real = lookup_replace_object(odb->repo, oid);

  int ret = istream_source(&st, odb, real);

  if (ret)

    return NULL;

  if (filter) {

    /* Add "&& !is_null_stream_filter(filter)" for performance */

    struct odb_read_stream *nst = attach_stream_filter(st, filter);

    if (!nst) {

      odb_read_stream_close(st);

      return NULL;

    }

    st = nst;

  }

  return st;

}

int odb_stream_blob_to_fd(struct object_database *odb,

        int fd,

        const struct object_id *oid,

        struct stream_filter *filter,

        int can_seek)

{

  struct odb_read_stream *st;

  ssize_t kept = 0;

  int result = -1;

  st = odb_read_stream_open(odb, oid, filter);

  if (!st) {

    if (filter)

      free_stream_filter(filter);

    return result;

  }

  if (st->type != OBJ_BLOB)

    goto close_and_exit;

  for (;;) {

    char buf[1024 * 16];

    ssize_t wrote, holeto;

    ssize_t readlen = odb_read_stream_read(st, buf, sizeof(buf));

    if (readlen < 0)

      goto close_and_exit;

    if (!readlen)

      break;

    if (can_seek && sizeof(buf) == readlen) {

      for (holeto = 0; holeto < readlen; holeto++)

        if (buf[holeto])

          break;

      if (readlen == holeto) {

        kept += holeto;

        continue;

      }

    }

    if (kept && lseek(fd, kept, SEEK_CUR) == (off_t) -1)

      goto close_and_exit;

    else

      kept = 0;

    wrote = write_in_full(fd, buf, readlen);

    if (wrote < 0)

      goto close_and_exit;

  }

  if (kept && (lseek(fd, kept - 1, SEEK_CUR) == (off_t) -1 ||

         xwrite(fd, "", 1) != 1))

    goto close_and_exit;

  result = 0;

 close_and_exit:

  odb_read_stream_close(st);

  return result;

}