/* Copyright (c) Dovecot authors, see top-level COPYING file */

#include "lib.h"

#include "istream-private.h"

#include "istream-sized.h"

struct sized_istream {

  struct istream_private istream;

  istream_sized_callback_t *error_callback;

  void *error_context;

  uoff_t size;

  bool min_size_only;

};

static void i_stream_sized_destroy(struct iostream_private *stream)

{

  struct sized_istream *sstream =

    container_of(stream, struct sized_istream, istream.iostream);

  uoff_t v_offset;

  v_offset = sstream->istream.parent_start_offset +

    sstream->istream.istream.v_offset;

  if (sstream->istream.parent->seekable ||

      v_offset > sstream->istream.parent->v_offset) {

    /* get to same position in parent stream */

    i_stream_seek(sstream->istream.parent, v_offset);

  }

}

static const char *

i_stream_create_sized_default_error_callback(

  const struct istream_sized_error_data *data, void *context ATTR_UNUSED)

{

  if (data->v_offset + data->new_bytes < data->wanted_size) {

    return t_strdup_printf("Stream is smaller than expected "

      "(%"PRIuUOFF_T" < %"PRIuUOFF_T")",

      data->v_offset + data->new_bytes, data->wanted_size);

  } else {

    return t_strdup_printf("Stream is larger than expected "

      "(%"PRIuUOFF_T" > %"PRIuUOFF_T", eof=%d)",

      data->v_offset + data->new_bytes, data->wanted_size,

      data->eof ? 1 : 0);

  }

}

static ssize_t

i_stream_sized_parent_read(struct istream_private *stream, size_t *pos_r)

{

  ssize_t ret;

  do {

    ret = i_stream_read_memarea(stream->parent);

    stream->istream.stream_errno = stream->parent->stream_errno;

    stream->istream.eof = stream->parent->eof;

    stream->buffer = i_stream_get_data(stream->parent, pos_r);

  } while (*pos_r <= stream->pos && ret > 0);

  return ret;

}

static ssize_t i_stream_sized_read(struct istream_private *stream)

{

  struct sized_istream *sstream =

    container_of(stream, struct sized_istream, istream);

  struct istream_sized_error_data data;

  const char *error;

  uoff_t left;

  ssize_t ret;

  size_t pos;

  i_stream_seek(stream->parent, sstream->istream.parent_start_offset +

          stream->istream.v_offset);

  stream->pos -= stream->skip;

  stream->skip = 0;

  stream->buffer = i_stream_get_data(stream->parent, &pos);

  if (pos > stream->pos)

    ret = 0;

  else {

    if ((ret = i_stream_sized_parent_read(stream, &pos)) == -2)

      return -2;

  }

  left = sstream->size - stream->istream.v_offset;

  if (pos == left && ret != -1) {

    /* we have exactly the wanted amount of data left, but we

       don't know yet if there is more data in parent. */

    ret = i_stream_sized_parent_read(stream, &pos);

  }

  i_zero(&data);

  data.v_offset = stream->istream.v_offset;

  data.new_bytes = pos;

  data.wanted_size = sstream->size;

  data.eof = stream->istream.eof;

  if (pos == left) {

    /* we may or may not be finished, depending on whether

       parent is at EOF. */

  } else if (pos > left) {

    /* parent has more data available than expected */

    if (!sstream->min_size_only) {

      error = sstream->error_callback(&data, sstream->error_context);

      io_stream_set_error(&stream->iostream, "%s", error);

      stream->istream.stream_errno = EINVAL;

      return -1;

    }

    pos = left;

    if (pos <= stream->pos) {

      stream->istream.eof = TRUE;

      ret = -1;

    }

  } else if (!stream->istream.eof) {

    /* still more to read */

  } else if (stream->istream.stream_errno != 0) {

    /* parent stream read() failed - preserve the error */

  } else {

    /* EOF before we reached the wanted size */

    error = sstream->error_callback(&data, sstream->error_context);

    io_stream_set_error(&stream->iostream, "%s", error);

    stream->istream.stream_errno = EPIPE;

  }

  ret = pos > stream->pos ? (ssize_t)(pos - stream->pos) :

    (ret == 0 ? 0 : -1);

  stream->pos = pos;

  i_assert(ret != -1 || stream->istream.eof ||

     stream->istream.stream_errno != 0);

  return ret;

}

static int

i_stream_sized_stat(struct istream_private *stream, bool exact ATTR_UNUSED)

{

  struct sized_istream *sstream =

    container_of(stream, struct sized_istream, istream);

  const struct stat *st;

  /* parent stream may be base64-decoder. don't waste time decoding the

     entire stream, since we already know what the size is supposed

     to be. */

  if (i_stream_stat(stream->parent, FALSE, &st) < 0) {

    stream->istream.stream_errno = stream->parent->stream_errno;

    return -1;

  }

  stream->statbuf = *st;

  stream->statbuf.st_size = sstream->size;

  return 0;

}

static struct sized_istream *

i_stream_create_sized_common(struct istream *input, uoff_t size)

{

  struct sized_istream *sstream;

  sstream = i_new(struct sized_istream, 1);

  sstream->size = size;

  sstream->istream.max_buffer_size = input->real_stream->max_buffer_size;

  sstream->istream.iostream.destroy = i_stream_sized_destroy;

  sstream->istream.read = i_stream_sized_read;

  sstream->istream.stat = i_stream_sized_stat;

  sstream->istream.istream.readable_fd = input->readable_fd;

  sstream->istream.istream.blocking = input->blocking;

  sstream->istream.istream.seekable = input->seekable;

  (void)i_stream_create(&sstream->istream, input,

            i_stream_get_fd(input),

            ISTREAM_HIDDEN_INPUTS_NONE, 0);

  return sstream;

}

struct istream *i_stream_create_sized(struct istream *input, uoff_t size)

{

  struct sized_istream *sstream;

  sstream = i_stream_create_sized_common(input, size);

  sstream->error_callback = i_stream_create_sized_default_error_callback;

  sstream->error_context = sstream;

  return &sstream->istream.istream;

}

struct istream *i_stream_create_sized_range(struct istream *input,

              uoff_t offset, uoff_t size)

{

  uoff_t orig_offset = input->v_offset;

  struct istream *ret;

  input->v_offset = offset;

  ret = i_stream_create_sized(input, size);

  input->v_offset = orig_offset;

  return ret;

}

struct istream *i_stream_create_min_sized(struct istream *input, uoff_t min_size)

{

  struct istream *ret;

  ret= i_stream_create_sized(input, min_size);

  struct sized_istream *ret_sstream =

    container_of(ret->real_stream, struct sized_istream, istream);

  ret_sstream->min_size_only = TRUE;

  return ret;

}

struct istream *i_stream_create_min_sized_range(struct istream *input,

            uoff_t offset, uoff_t min_size)

{

  struct istream *ret;

  ret = i_stream_create_sized_range(input, offset, min_size);

  struct sized_istream *ret_sstream =

    container_of(ret->real_stream, struct sized_istream, istream);

  ret_sstream->min_size_only = TRUE;

  return ret;

}

#undef i_stream_create_sized_with_callback

struct istream *

i_stream_create_sized_with_callback(struct istream *input, uoff_t size,

            istream_sized_callback_t *error_callback,

            void *context)

{

  struct sized_istream *sstream;

  sstream = i_stream_create_sized_common(input, size);

  sstream->error_callback = error_callback;

  sstream->error_context = context;

  return &sstream->istream.istream;

}