/*

 * Copyright (c) 2011, Google Inc.

 */

#define USE_THE_REPOSITORY_VARIABLE

#include "git-compat-util.h"

#include "convert.h"

#include "environment.h"

#include "streaming.h"

#include "repository.h"

#include "object-file.h"

#include "odb.h"

#include "replace-object.h"

#include "packfile.h"

typedef int (*open_istream_fn)(struct git_istream *,

             struct repository *,

             const struct object_id *,

             enum object_type *);

typedef int (*close_istream_fn)(struct git_istream *);

typedef ssize_t (*read_istream_fn)(struct git_istream *, char *, size_t);

#define FILTER_BUFFER (1024*16)

struct filtered_istream {

  struct git_istream *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;

};

struct git_istream {

  open_istream_fn open;

  close_istream_fn close;

  read_istream_fn read;

  unsigned long size; /* inflated size of full object */

  git_zstream z;

  enum { z_unused, z_used, z_done, z_error } z_state;

  union {

    struct {

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

      unsigned long read_ptr;

    } incore;

    struct {

      void *mapped;

      unsigned long mapsize;

      char hdr[32];

      int hdr_avail;

      int hdr_used;

    } loose;

    struct {

      struct packed_git *pack;

      off_t pos;

    } in_pack;

    struct filtered_istream filtered;

  } u;

};

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

 *

 * Common helpers

 *

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

static void close_deflated_stream(struct git_istream *st)

{

  if (st->z_state == z_used)

    git_inflate_end(&st->z);

}

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

 *

 * Filtered stream

 *

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

static int close_istream_filtered(struct git_istream *st)

{

  free_stream_filter(st->u.filtered.filter);

  return close_istream(st->u.filtered.upstream);

}

static ssize_t read_istream_filtered(struct git_istream *st, char *buf,

             size_t sz)

{

  struct filtered_istream *fs = &(st->u.filtered);

  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 = read_istream(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 git_istream *attach_stream_filter(struct git_istream *st,

            struct stream_filter *filter)

{

  struct git_istream *ifs = xmalloc(sizeof(*ifs));

  struct filtered_istream *fs = &(ifs->u.filtered);

  ifs->close = close_istream_filtered;

  ifs->read = read_istream_filtered;

  fs->upstream = st;

  fs->filter = filter;

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

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

  fs->input_finished = 0;

  ifs->size = -1; /* unknown */

  return ifs;

}

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

 *

 * Loose object stream

 *

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

static ssize_t read_istream_loose(struct git_istream *st, char *buf, size_t sz)

{

  size_t total_read = 0;

  switch (st->z_state) {

  case z_done:

    return 0;

  case z_error:

    return -1;

  default:

    break;

  }

  if (st->u.loose.hdr_used < st->u.loose.hdr_avail) {

    size_t to_copy = st->u.loose.hdr_avail - st->u.loose.hdr_used;

    if (sz < to_copy)

      to_copy = sz;

    memcpy(buf, st->u.loose.hdr + st->u.loose.hdr_used, to_copy);

    st->u.loose.hdr_used += to_copy;

    total_read += to_copy;

  }

  while (total_read < sz) {

    int status;

    st->z.next_out = (unsigned char *)buf + total_read;

    st->z.avail_out = sz - total_read;

    status = git_inflate(&st->z, Z_FINISH);

    total_read = st->z.next_out - (unsigned char *)buf;

    if (status == Z_STREAM_END) {

      git_inflate_end(&st->z);

      st->z_state = z_done;

      break;

    }

    if (status != Z_OK && (status != Z_BUF_ERROR || total_read < sz)) {

      git_inflate_end(&st->z);

      st->z_state = z_error;

      return -1;

    }

  }

  return total_read;

}

static int close_istream_loose(struct git_istream *st)

{

  close_deflated_stream(st);

  munmap(st->u.loose.mapped, st->u.loose.mapsize);

  return 0;

}

static int open_istream_loose(struct git_istream *st, struct repository *r,

            const struct object_id *oid,

            enum object_type *type)

{

  struct object_info oi = OBJECT_INFO_INIT;

  struct odb_source *source;

  oi.sizep = &st->size;

  oi.typep = type;

  odb_prepare_alternates(r->objects);

  for (source = r->objects->sources; source; source = source->next) {

    st->u.loose.mapped = odb_source_loose_map_object(source, oid,

                 &st->u.loose.mapsize);

    if (st->u.loose.mapped)

      break;

  }

  if (!st->u.loose.mapped)

    return -1;

  switch (unpack_loose_header(&st->z, st->u.loose.mapped,

            st->u.loose.mapsize, st->u.loose.hdr,

            sizeof(st->u.loose.hdr))) {

  case ULHR_OK:

    break;

  case ULHR_BAD:

  case ULHR_TOO_LONG:

    goto error;

  }

  if (parse_loose_header(st->u.loose.hdr, &oi) < 0 || *type < 0)

    goto error;

  st->u.loose.hdr_used = strlen(st->u.loose.hdr) + 1;

  st->u.loose.hdr_avail = st->z.total_out;

  st->z_state = z_used;

  st->close = close_istream_loose;

  st->read = read_istream_loose;

  return 0;

error:

  git_inflate_end(&st->z);

  munmap(st->u.loose.mapped, st->u.loose.mapsize);

  return -1;

}

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

 *

 * Non-delta packed object stream

 *

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

static ssize_t read_istream_pack_non_delta(struct git_istream *st, char *buf,

             size_t sz)

{

  size_t total_read = 0;

  switch (st->z_state) {

  case z_unused:

    memset(&st->z, 0, sizeof(st->z));

    git_inflate_init(&st->z);

    st->z_state = z_used;

    break;

  case z_done:

    return 0;

  case z_error:

    return -1;

  case z_used:

    break;

  }

  while (total_read < sz) {

    int status;

    struct pack_window *window = NULL;

    unsigned char *mapped;

    mapped = use_pack(st->u.in_pack.pack, &window,

          st->u.in_pack.pos, &st->z.avail_in);

    st->z.next_out = (unsigned char *)buf + total_read;

    st->z.avail_out = sz - total_read;

    st->z.next_in = mapped;

    status = git_inflate(&st->z, Z_FINISH);

    st->u.in_pack.pos += st->z.next_in - mapped;

    total_read = st->z.next_out - (unsigned char *)buf;

    unuse_pack(&window);

    if (status == Z_STREAM_END) {

      git_inflate_end(&st->z);

      st->z_state = z_done;

      break;

    }

    /*

     * Unlike the loose object case, we do not have to worry here

     * about running out of input bytes and spinning infinitely. If

     * we get Z_BUF_ERROR due to too few input bytes, then we'll

     * replenish them in the next use_pack() call when we loop. If

     * we truly hit the end of the pack (i.e., because it's corrupt

     * or truncated), then use_pack() catches that and will die().

     */

    if (status != Z_OK && status != Z_BUF_ERROR) {

      git_inflate_end(&st->z);

      st->z_state = z_error;

      return -1;

    }

  }

  return total_read;

}

static int close_istream_pack_non_delta(struct git_istream *st)

{

  close_deflated_stream(st);

  return 0;

}

static int open_istream_pack_non_delta(struct git_istream *st,

               struct repository *r UNUSED,

               const struct object_id *oid UNUSED,

               enum object_type *type UNUSED)

{

  struct pack_window *window;

  enum object_type in_pack_type;

  window = NULL;

  in_pack_type = unpack_object_header(st->u.in_pack.pack,

              &window,

              &st->u.in_pack.pos,

              &st->size);

  unuse_pack(&window);

  switch (in_pack_type) {

  default:

    return -1; /* we do not do deltas for now */

  case OBJ_COMMIT:

  case OBJ_TREE:

  case OBJ_BLOB:

  case OBJ_TAG:

    break;

  }

  st->z_state = z_unused;

  st->close = close_istream_pack_non_delta;

  st->read = read_istream_pack_non_delta;

  return 0;

}

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

 *

 * In-core stream

 *

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

static int close_istream_incore(struct git_istream *st)

{

  free(st->u.incore.buf);

  return 0;

}

static ssize_t read_istream_incore(struct git_istream *st, char *buf, size_t sz)

{

  size_t read_size = sz;

  size_t remainder = st->size - st->u.incore.read_ptr;

  if (remainder <= read_size)

    read_size = remainder;

  if (read_size) {

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

    st->u.incore.read_ptr += read_size;

  }

  return read_size;

}

static int open_istream_incore(struct git_istream *st, struct repository *r,

             const struct object_id *oid, enum object_type *type)

{

  struct object_info oi = OBJECT_INFO_INIT;

  st->u.incore.read_ptr = 0;

  st->close = close_istream_incore;

  st->read = read_istream_incore;

  oi.typep = type;

  oi.sizep = &st->size;

  oi.contentp = (void **)&st->u.incore.buf;

  return odb_read_object_info_extended(r->objects, oid, &oi,

               OBJECT_INFO_DIE_IF_CORRUPT);

}

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

 * static helpers variables and functions for users of streaming interface

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

static int istream_source(struct git_istream *st,

        struct repository *r,

        const struct object_id *oid,

        enum object_type *type)

{

  unsigned long size;

  int status;

  struct object_info oi = OBJECT_INFO_INIT;

  oi.typep = type;

  oi.sizep = &size;

  status = odb_read_object_info_extended(r->objects, oid, &oi, 0);

  if (status < 0)

    return status;

  switch (oi.whence) {

  case OI_LOOSE:

    st->open = open_istream_loose;

    return 0;

  case OI_PACKED:

    if (!oi.u.packed.is_delta &&

        repo_settings_get_big_file_threshold(the_repository) < size) {

      st->u.in_pack.pack = oi.u.packed.pack;

      st->u.in_pack.pos = oi.u.packed.offset;

      st->open = open_istream_pack_non_delta;

      return 0;

    }

    /* fallthru */

  default:

    st->open = open_istream_incore;

    return 0;

  }

}

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

 * Users of streaming interface

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

int close_istream(struct git_istream *st)

{

  int r = st->close(st);

  free(st);

  return r;

}

ssize_t read_istream(struct git_istream *st, void *buf, size_t sz)

{

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

}

struct git_istream *open_istream(struct repository *r,

         const struct object_id *oid,

         enum object_type *type,

         unsigned long *size,

         struct stream_filter *filter)

{

  struct git_istream *st = xmalloc(sizeof(*st));

  const struct object_id *real = lookup_replace_object(r, oid);

  int ret = istream_source(st, r, real, type);

  if (ret) {

    free(st);

    return NULL;

  }

  if (st->open(st, r, real, type)) {

    if (open_istream_incore(st, r, real, type)) {

      free(st);

      return NULL;

    }

  }

  if (filter) {

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

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

    if (!nst) {

      close_istream(st);

      return NULL;

    }

    st = nst;

  }

  *size = st->size;

  return st;

}

int stream_blob_to_fd(int fd, const struct object_id *oid, struct stream_filter *filter,

          int can_seek)

{

  struct git_istream *st;

  enum object_type type;

  unsigned long sz;

  ssize_t kept = 0;

  int result = -1;

  st = open_istream(the_repository, oid, &type, &sz, filter);

  if (!st) {

    if (filter)

      free_stream_filter(filter);

    return result;

  }

  if (type != OBJ_BLOB)

    goto close_and_exit;

  for (;;) {

    char buf[1024 * 16];

    ssize_t wrote, holeto;

    ssize_t readlen = read_istream(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:

  close_istream(st);

  return result;

}