subversion/libsvn_subr/stream.c

/*
 * stream.c:   svn_stream operations
 *
 * ====================================================================
 *    Licensed to the Apache Software Foundation (ASF) under one
 *    or more contributor license agreements.  See the NOTICE file
 *    distributed with this work for additional information
 *    regarding copyright ownership.  The ASF licenses this file
 *    to you under the Apache License, Version 2.0 (the
 *    "License"); you may not use this file except in compliance
 *    with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing,
 *    software distributed under the License is distributed on an
 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *    KIND, either express or implied.  See the License for the
 *    specific language governing permissions and limitations
 *    under the License.
 * ====================================================================
 */

#include <assert.h>
#include <stdio.h>

#include <apr.h>
#include <apr_pools.h>
#include <apr_strings.h>
#include <apr_file_io.h>
#include <apr_errno.h>
#include <apr_md5.h>

#include <zlib.h>

#include "svn_pools.h"
#include "svn_io.h"
#include "svn_error.h"
#include "svn_string.h"
#include "svn_utf.h"
#include "svn_checksum.h"
#include "svn_path.h"
#include "svn_private_config.h"
#include "private/svn_error_private.h"
#include "private/svn_eol_private.h"
#include "private/svn_io_private.h"
#include "private/svn_subr_private.h"


struct svn_stream_t {
  void *baton;
  svn_read_fn_t read_fn;
  svn_stream_skip_fn_t skip_fn;
  svn_write_fn_t write_fn;
  svn_close_fn_t close_fn;
  svn_stream_mark_fn_t mark_fn;
  svn_stream_seek_fn_t seek_fn;
  svn_stream__is_buffered_fn_t is_buffered_fn;
  apr_file_t *file; /* Maybe NULL */
};


/*** Forward declarations. ***/

static svn_error_t *
skip_default_handler(void *baton, apr_size_t len, svn_read_fn_t read_fn);


/*** Generic streams. ***/

svn_stream_t *
svn_stream_create(void *baton, apr_pool_t *pool)
{
  svn_stream_t *stream;

  stream = apr_palloc(pool, sizeof(*stream));
  stream->baton = baton;
  stream->read_fn = NULL;
  stream->skip_fn = NULL;
  stream->write_fn = NULL;
  stream->close_fn = NULL;
  stream->mark_fn = NULL;
  stream->seek_fn = NULL;
  stream->is_buffered_fn = NULL;
  stream->file = NULL;
  return stream;
}


void
svn_stream_set_baton(svn_stream_t *stream, void *baton)
{
  stream->baton = baton;
}


void
svn_stream_set_read(svn_stream_t *stream, svn_read_fn_t read_fn)
{
  stream->read_fn = read_fn;
}

void
svn_stream_set_skip(svn_stream_t *stream, svn_stream_skip_fn_t skip_fn)
{
  stream->skip_fn = skip_fn;
}

void
svn_stream_set_write(svn_stream_t *stream, svn_write_fn_t write_fn)
{
  stream->write_fn = write_fn;
}

void
svn_stream_set_close(svn_stream_t *stream, svn_close_fn_t close_fn)
{
  stream->close_fn = close_fn;
}

void
svn_stream_set_mark(svn_stream_t *stream, svn_stream_mark_fn_t mark_fn)
{
  stream->mark_fn = mark_fn;
}

void
svn_stream_set_seek(svn_stream_t *stream, svn_stream_seek_fn_t seek_fn)
{
  stream->seek_fn = seek_fn;
}

void
svn_stream__set_is_buffered(svn_stream_t *stream,
                            svn_stream__is_buffered_fn_t is_buffered_fn)
{
  stream->is_buffered_fn = is_buffered_fn;
}

svn_error_t *
svn_stream_read(svn_stream_t *stream, char *buffer, apr_size_t *len)
{
  SVN_ERR_ASSERT(stream->read_fn != NULL);
  return svn_error_trace(stream->read_fn(stream->baton, buffer, len));
}


svn_error_t *
svn_stream_skip(svn_stream_t *stream, apr_size_t len)
{
  if (stream->skip_fn == NULL)
    return svn_error_trace(
            skip_default_handler(stream->baton, len, stream->read_fn));

  return svn_error_trace(stream->skip_fn(stream->baton, len));
}


svn_error_t *
svn_stream_write(svn_stream_t *stream, const char *data, apr_size_t *len)
{
  SVN_ERR_ASSERT(stream->write_fn != NULL);
  return svn_error_trace(stream->write_fn(stream->baton, data, len));
}


svn_error_t *
svn_stream_reset(svn_stream_t *stream)
{
  return svn_error_trace(
            svn_stream_seek(stream, NULL));
}

svn_boolean_t
svn_stream_supports_mark(svn_stream_t *stream)
{
  return stream->mark_fn != NULL;
}

svn_error_t *
svn_stream_mark(svn_stream_t *stream, svn_stream_mark_t **mark,
                apr_pool_t *pool)
{
  if (stream->mark_fn == NULL)
    return svn_error_create(SVN_ERR_STREAM_SEEK_NOT_SUPPORTED, NULL, NULL);

  return svn_error_trace(stream->mark_fn(stream->baton, mark, pool));
}

svn_error_t *
svn_stream_seek(svn_stream_t *stream, const svn_stream_mark_t *mark)
{
  if (stream->seek_fn == NULL)
    return svn_error_create(SVN_ERR_STREAM_SEEK_NOT_SUPPORTED, NULL, NULL);

  return svn_error_trace(stream->seek_fn(stream->baton, mark));
}

svn_boolean_t
svn_stream__is_buffered(svn_stream_t *stream)
{
  if (stream->is_buffered_fn == NULL)
    return FALSE;

  return stream->is_buffered_fn(stream->baton);
}

svn_error_t *
svn_stream_close(svn_stream_t *stream)
{
  if (stream->close_fn == NULL)
    return SVN_NO_ERROR;
  return svn_error_trace(stream->close_fn(stream->baton));
}

svn_error_t *
svn_stream_puts(svn_stream_t *stream,
                const char *str)
{
  apr_size_t len;
  len = strlen(str);
  return svn_error_trace(svn_stream_write(stream, str, &len));
}

svn_error_t *
svn_stream_printf(svn_stream_t *stream,
                  apr_pool_t *pool,
                  const char *fmt,
                  ...)
{
  const char *message;
  va_list ap;

  va_start(ap, fmt);
  message = apr_pvsprintf(pool, fmt, ap);
  va_end(ap);

  return svn_error_trace(svn_stream_puts(stream, message));
}


svn_error_t *
svn_stream_printf_from_utf8(svn_stream_t *stream,
                            const char *encoding,
                            apr_pool_t *pool,
                            const char *fmt,
                            ...)
{
  const char *message, *translated;
  va_list ap;

  va_start(ap, fmt);
  message = apr_pvsprintf(pool, fmt, ap);
  va_end(ap);

  SVN_ERR(svn_utf_cstring_from_utf8_ex2(&translated, message, encoding,
                                        pool));

  return svn_error_trace(svn_stream_puts(stream, translated));
}

/* Size that 90% of the lines we encounter will be not longer than.
   used by stream_readline_bytewise() and stream_readline_chunky().
 */
#define LINE_CHUNK_SIZE 80

/* Guts of svn_stream_readline().
 * Returns the line read from STREAM in *STRINGBUF, and indicates
 * end-of-file in *EOF.  If DETECT_EOL is TRUE, the end-of-line indicator
 * is detected automatically and returned in *EOL.
 * If DETECT_EOL is FALSE, *EOL must point to the desired end-of-line
 * indicator.  STRINGBUF is allocated in POOL. */
static svn_error_t *
stream_readline_bytewise(svn_stringbuf_t **stringbuf,
                         svn_boolean_t *eof,
                         const char *eol,
                         svn_stream_t *stream,
                         apr_pool_t *pool)
{
  svn_stringbuf_t *str;
  apr_size_t numbytes;
  const char *match;
  char c;

  /* Since we're reading one character at a time, let's at least
     optimize for the 90% case.  90% of the time, we can avoid the
     stringbuf ever having to realloc() itself if we start it out at
     80 chars.  */
  str = svn_stringbuf_create_ensure(LINE_CHUNK_SIZE, pool);

  /* Read into STR up to and including the next EOL sequence. */
  match = eol;
  while (*match)
    {
      numbytes = 1;
      SVN_ERR(svn_stream_read(stream, &c, &numbytes));
      if (numbytes != 1)
        {
          /* a 'short' read means the stream has run out. */
          *eof = TRUE;
          *stringbuf = str;
          return SVN_NO_ERROR;
        }

      if (c == *match)
        match++;
      else
        match = eol;

      svn_stringbuf_appendbyte(str, c);
    }

  *eof = FALSE;
  svn_stringbuf_chop(str, match - eol);
  *stringbuf = str;

  return SVN_NO_ERROR;
}

static svn_error_t *
stream_readline_chunky(svn_stringbuf_t **stringbuf,
                       svn_boolean_t *eof,
                       const char *eol,
                       svn_stream_t *stream,
                       apr_pool_t *pool)
{
  /* Read larger chunks of data at once into this buffer and scan
   * that for EOL. A good chunk size should be about 80 chars since
   * most text lines will be shorter. However, don't use a much
   * larger value because filling the buffer from the stream takes
   * time as well.
   */
  char buffer[LINE_CHUNK_SIZE+1];

  /* variables */
  svn_stream_mark_t *mark;
  apr_size_t numbytes;
  const char *eol_pos;
  apr_size_t total_parsed = 0;

  /* invariant for this call */
  const size_t eol_len = strlen(eol);

  /* Remember the line start so this plus the line length will be
   * the position to move to at the end of this function.
   */
  SVN_ERR(svn_stream_mark(stream, &mark, pool));

  /* Read the first chunk. */
  numbytes = LINE_CHUNK_SIZE;
  SVN_ERR(svn_stream_read(stream, buffer, &numbytes));
  buffer[numbytes] = '\0';

  /* Look for the EOL in this first chunk. If we find it, we are done here.
   */
  eol_pos = strstr(buffer, eol);
  if (eol_pos != NULL)
    {
      *stringbuf = svn_stringbuf_ncreate(buffer, eol_pos - buffer, pool);
      total_parsed = eol_pos - buffer + eol_len;
    }
  else if (numbytes < LINE_CHUNK_SIZE)
    {
      /* We hit EOF but not EOL.
       */
      *stringbuf = svn_stringbuf_ncreate(buffer, numbytes, pool);
      *eof = TRUE;
      return SVN_NO_ERROR;
     }
  else
    {
      /* A larger buffer for the string is needed. */
      svn_stringbuf_t *str;
      str = svn_stringbuf_create_ensure(2*LINE_CHUNK_SIZE, pool);
      svn_stringbuf_appendbytes(str, buffer, numbytes);
      *stringbuf = str;

      /* Loop reading chunks until an EOL was found. If we hit EOF, fall
       * back to the standard implementation. */
      do
      {
        /* Append the next chunk to the string read so far.
         */
        svn_stringbuf_ensure(str, str->len + LINE_CHUNK_SIZE);
        numbytes = LINE_CHUNK_SIZE;
        SVN_ERR(svn_stream_read(stream, str->data + str->len, &numbytes));
        str->len += numbytes;
        str->data[str->len] = '\0';

        /* Look for the EOL in the new data plus the last part of the
         * previous chunk because the EOL may span over the boundary
         * between both chunks.
         */
        eol_pos = strstr(str->data + str->len - numbytes - (eol_len-1), eol);

        if ((numbytes < LINE_CHUNK_SIZE) && (eol_pos == NULL))
        {
          /* We hit EOF instead of EOL. */
          *eof = TRUE;
          return SVN_NO_ERROR;
        }
      }
      while (eol_pos == NULL);

      /* Number of bytes we actually consumed (i.e. line + EOF).
       * We need to "return" the rest to the stream by moving its
       * read pointer.
       */
      total_parsed = eol_pos - str->data + eol_len;

      /* Terminate the string at the EOL postion and return it. */
      str->len = eol_pos - str->data;
      str->data[str->len] = 0;
    }

  /* Move the stream read pointer to the first position behind the EOL.
   */
  SVN_ERR(svn_stream_seek(stream, mark));
  return svn_error_trace(svn_stream_skip(stream, total_parsed));
}

/* Guts of svn_stream_readline().
 * Returns the line read from STREAM in *STRINGBUF, and indicates
 * end-of-file in *EOF.  EOL must point to the desired end-of-line
 * indicator.  STRINGBUF is allocated in POOL. */
static svn_error_t *
stream_readline(svn_stringbuf_t **stringbuf,
                svn_boolean_t *eof,
                const char *eol,
                svn_stream_t *stream,
                apr_pool_t *pool)
{
  *eof = FALSE;

  /* Often, we operate on APR file or string-based streams and know what
   * EOL we are looking for. Optimize that common case.
   */
  if (svn_stream_supports_mark(stream) &&
      svn_stream__is_buffered(stream))
    {
      /* We can efficiently read chunks speculatively and reposition the
       * stream pointer to the end of the line once we found that.
       */
      SVN_ERR(stream_readline_chunky(stringbuf,
                                     eof,
                                     eol,
                                     stream,
                                     pool));
    }
  else
    {
      /* Use the standard byte-byte implementation.
       */
      SVN_ERR(stream_readline_bytewise(stringbuf,
                                       eof,
                                       eol,
                                       stream,
                                       pool));
    }

  return SVN_NO_ERROR;
}

svn_error_t *
svn_stream_readline(svn_stream_t *stream,
                    svn_stringbuf_t **stringbuf,
                    const char *eol,
                    svn_boolean_t *eof,
                    apr_pool_t *pool)
{
  return svn_error_trace(stream_readline(stringbuf, eof, eol, stream,
                                         pool));
}

svn_error_t *svn_stream_copy3(svn_stream_t *from, svn_stream_t *to,
                              svn_cancel_func_t cancel_func,
                              void *cancel_baton,
                              apr_pool_t *scratch_pool)
{
  char *buf = apr_palloc(scratch_pool, SVN__STREAM_CHUNK_SIZE);
  svn_error_t *err;
  svn_error_t *err2;

  /* Read and write chunks until we get a short read, indicating the
     end of the stream.  (We can't get a short write without an
     associated error.) */
  while (1)
    {
      apr_size_t len = SVN__STREAM_CHUNK_SIZE;

      if (cancel_func)
        {
          err = cancel_func(cancel_baton);
          if (err)
             break;
        }

      err = svn_stream_read(from, buf, &len);
      if (err)
         break;

      if (len > 0)
        err = svn_stream_write(to, buf, &len);

      if (err || (len != SVN__STREAM_CHUNK_SIZE))
          break;
    }

  err2 = svn_error_compose_create(svn_stream_close(from),
                                  svn_stream_close(to));

  return svn_error_compose_create(err, err2);
}

svn_error_t *
svn_stream_contents_same2(svn_boolean_t *same,
                          svn_stream_t *stream1,
                          svn_stream_t *stream2,
                          apr_pool_t *pool)
{
  char *buf1 = apr_palloc(pool, SVN__STREAM_CHUNK_SIZE);
  char *buf2 = apr_palloc(pool, SVN__STREAM_CHUNK_SIZE);
  apr_size_t bytes_read1 = SVN__STREAM_CHUNK_SIZE;
  apr_size_t bytes_read2 = SVN__STREAM_CHUNK_SIZE;
  svn_error_t *err = NULL;

  *same = TRUE;  /* assume TRUE, until disproved below */
  while (bytes_read1 == SVN__STREAM_CHUNK_SIZE
         && bytes_read2 == SVN__STREAM_CHUNK_SIZE)
    {
      err = svn_stream_read(stream1, buf1, &bytes_read1);
      if (err)
        break;
      err = svn_stream_read(stream2, buf2, &bytes_read2);
      if (err)
        break;

      if ((bytes_read1 != bytes_read2)
          || (memcmp(buf1, buf2, bytes_read1)))
        {
          *same = FALSE;
          break;
        }
    }

  return svn_error_compose_create(err,
                                  svn_error_compose_create(
                                    svn_stream_close(stream1),
                                    svn_stream_close(stream2)));
}


/*** Stream implementation utilities ***/

/* Skip data from any stream by reading and simply discarding it. */
static svn_error_t *
skip_default_handler(void *baton, apr_size_t len, svn_read_fn_t read_fn)
{
  apr_size_t bytes_read = 1;
  char buffer[4096];
  apr_size_t to_read = len;

  while ((to_read > 0) && (bytes_read > 0))
    {
      bytes_read = sizeof(buffer) < to_read ? sizeof(buffer) : to_read;
      SVN_ERR(read_fn(baton, buffer, &bytes_read));
      to_read -= bytes_read;
    }

  return SVN_NO_ERROR;
}


/*** Generic readable empty stream ***/

static svn_error_t *
read_handler_empty(void *baton, char *buffer, apr_size_t *len)
{
  *len = 0;
  return SVN_NO_ERROR;
}

static svn_error_t *
write_handler_empty(void *baton, const char *data, apr_size_t *len)
{
  return SVN_NO_ERROR;
}

static svn_error_t *
mark_handler_empty(void *baton, svn_stream_mark_t **mark, apr_pool_t *pool)
{
  *mark = NULL; /* Seek to start of stream marker */
  return SVN_NO_ERROR;
}

static svn_error_t *
seek_handler_empty(void *baton, const svn_stream_mark_t *mark)
{
  return SVN_NO_ERROR;
}

static svn_boolean_t
is_buffered_handler_empty(void *baton)
{
  return FALSE;
}


svn_stream_t *
svn_stream_empty(apr_pool_t *pool)
{
  svn_stream_t *stream;

  stream = svn_stream_create(NULL, pool);
  svn_stream_set_read(stream, read_handler_empty);
  svn_stream_set_write(stream, write_handler_empty);
  svn_stream_set_mark(stream, mark_handler_empty);
  svn_stream_set_seek(stream, seek_handler_empty);
  svn_stream__set_is_buffered(stream, is_buffered_handler_empty);
  return stream;
}


/*** Stream duplication support ***/
struct baton_tee {
  svn_stream_t *out1;
  svn_stream_t *out2;
};


static svn_error_t *
write_handler_tee(void *baton, const char *data, apr_size_t *len)
{
  struct baton_tee *bt = baton;

  SVN_ERR(svn_stream_write(bt->out1, data, len));
  SVN_ERR(svn_stream_write(bt->out2, data, len));

  return SVN_NO_ERROR;
}


static svn_error_t *
close_handler_tee(void *baton)
{
  struct baton_tee *bt = baton;

  SVN_ERR(svn_stream_close(bt->out1));
  SVN_ERR(svn_stream_close(bt->out2));

  return SVN_NO_ERROR;
}


svn_stream_t *
svn_stream_tee(svn_stream_t *out1,
               svn_stream_t *out2,
               apr_pool_t *pool)
{
  struct baton_tee *baton;
  svn_stream_t *stream;

  if (out1 == NULL)
    return out2;

  if (out2 == NULL)
    return out1;

  baton = apr_palloc(pool, sizeof(*baton));
  baton->out1 = out1;
  baton->out2 = out2;
  stream = svn_stream_create(baton, pool);
  svn_stream_set_write(stream, write_handler_tee);
  svn_stream_set_close(stream, close_handler_tee);

  return stream;
}


/*** Ownership detaching stream ***/

static svn_error_t *
read_handler_disown(void *baton, char *buffer, apr_size_t *len)
{
  return svn_error_trace(svn_stream_read(baton, buffer, len));
}

static svn_error_t *
skip_handler_disown(void *baton, apr_size_t len)
{
  return svn_error_trace(svn_stream_skip(baton, len));
}

static svn_error_t *
write_handler_disown(void *baton, const char *buffer, apr_size_t *len)
{
  return svn_error_trace(svn_stream_write(baton, buffer, len));
}

static svn_error_t *
mark_handler_disown(void *baton, svn_stream_mark_t **mark, apr_pool_t *pool)
{
  return svn_error_trace(svn_stream_mark(baton, mark, pool));
}

static svn_error_t *
seek_handler_disown(void *baton, const svn_stream_mark_t *mark)
{
  return svn_error_trace(svn_stream_seek(baton, mark));
}

static svn_boolean_t
is_buffered_handler_disown(void *baton)
{
  return svn_stream__is_buffered(baton);
}

svn_stream_t *
svn_stream_disown(svn_stream_t *stream, apr_pool_t *pool)
{
  svn_stream_t *s = svn_stream_create(stream, pool);

  svn_stream_set_read(s, read_handler_disown);
  svn_stream_set_skip(s, skip_handler_disown);
  svn_stream_set_write(s, write_handler_disown);
  svn_stream_set_mark(s, mark_handler_disown);
  svn_stream_set_seek(s, seek_handler_disown);
  svn_stream__set_is_buffered(s, is_buffered_handler_disown);

  return s;
}


/*** Generic stream for APR files ***/
struct baton_apr {
  apr_file_t *file;
  apr_pool_t *pool;
};

/* svn_stream_mark_t for streams backed by APR files. */
struct mark_apr {
  apr_off_t off;
};

static svn_error_t *
read_handler_apr(void *baton, char *buffer, apr_size_t *len)
{
  struct baton_apr *btn = baton;
  svn_error_t *err;
  svn_boolean_t eof;

  if (*len == 1)
    {
      err = svn_io_file_getc(buffer, btn->file, btn->pool);
      if (err)
        {
          *len = 0;
          if (APR_STATUS_IS_EOF(err->apr_err))
            {
              svn_error_clear(err);
              err = SVN_NO_ERROR;
            }
        }
    }
  else
    err = svn_io_file_read_full2(btn->file, buffer, *len, len,
                                 &eof, btn->pool);

  return svn_error_trace(err);
}

static svn_error_t *
skip_handler_apr(void *baton, apr_size_t len)
{
  struct baton_apr *btn = baton;
  apr_off_t offset = len;

  return svn_error_trace(
            svn_io_file_seek(btn->file, APR_CUR, &offset, btn->pool));
}

static svn_error_t *
write_handler_apr(void *baton, const char *data, apr_size_t *len)
{
  struct baton_apr *btn = baton;
  svn_error_t *err;

  if (*len == 1)
    {
      err = svn_io_file_putc(*data, btn->file, btn->pool);
      if (err)
        *len = 0;
    }
  else
    err = svn_io_file_write_full(btn->file, data, *len, len, btn->pool);

  return svn_error_trace(err);
}

static svn_error_t *
close_handler_apr(void *baton)
{
  struct baton_apr *btn = baton;

  return svn_error_trace(svn_io_file_close(btn->file, btn->pool));
}

static svn_error_t *
mark_handler_apr(void *baton, svn_stream_mark_t **mark, apr_pool_t *pool)
{
  struct baton_apr *btn = baton;
  struct mark_apr *mark_apr;

  mark_apr = apr_palloc(pool, sizeof(*mark_apr));
  mark_apr->off = 0;
  SVN_ERR(svn_io_file_seek(btn->file, APR_CUR, &mark_apr->off, btn->pool));
  *mark = (svn_stream_mark_t *)mark_apr;
  return SVN_NO_ERROR;
}

static svn_error_t *
seek_handler_apr(void *baton, const svn_stream_mark_t *mark)
{
  struct baton_apr *btn = baton;
  apr_off_t offset = (mark != NULL) ? ((const struct mark_apr *)mark)->off : 0;

  SVN_ERR(svn_io_file_seek(btn->file, APR_SET, &offset, btn->pool));

  return SVN_NO_ERROR;
}

static svn_boolean_t
is_buffered_handler_apr(void *baton)
{
  struct baton_apr *btn = baton;
  return (apr_file_flags_get(btn->file) & APR_BUFFERED) != 0;
}

svn_error_t *
svn_stream_open_readonly(svn_stream_t **stream,
                         const char *path,
                         apr_pool_t *result_pool,
                         apr_pool_t *scratch_pool)
{
  apr_file_t *file;

  SVN_ERR(svn_io_file_open(&file, path, APR_READ | APR_BUFFERED,
                           APR_OS_DEFAULT, result_pool));
  *stream = svn_stream_from_aprfile2(file, FALSE, result_pool);

  return SVN_NO_ERROR;
}


svn_error_t *
svn_stream_open_writable(svn_stream_t **stream,
                         const char *path,
                         apr_pool_t *result_pool,
                         apr_pool_t *scratch_pool)
{
  apr_file_t *file;

  SVN_ERR(svn_io_file_open(&file, path,
                           APR_WRITE
                             | APR_BUFFERED
                             | APR_CREATE
                             | APR_EXCL,
                           APR_OS_DEFAULT, result_pool));
  *stream = svn_stream_from_aprfile2(file, FALSE, result_pool);

  return SVN_NO_ERROR;
}


svn_error_t *
svn_stream_open_unique(svn_stream_t **stream,
                       const char **temp_path,
                       const char *dirpath,
                       svn_io_file_del_t delete_when,
                       apr_pool_t *result_pool,
                       apr_pool_t *scratch_pool)
{
  apr_file_t *file;

  SVN_ERR(svn_io_open_unique_file3(&file, temp_path, dirpath,
                                   delete_when, result_pool, scratch_pool));
  *stream = svn_stream_from_aprfile2(file, FALSE, result_pool);

  return SVN_NO_ERROR;
}


svn_stream_t *
svn_stream_from_aprfile2(apr_file_t *file,
                         svn_boolean_t disown,
                         apr_pool_t *pool)
{
  struct baton_apr *baton;
  svn_stream_t *stream;

  if (file == NULL)
    return svn_stream_empty(pool);

  baton = apr_palloc(pool, sizeof(*baton));
  baton->file = file;
  baton->pool = pool;
  stream = svn_stream_create(baton, pool);
  svn_stream_set_read(stream, read_handler_apr);
  svn_stream_set_write(stream, write_handler_apr);
  svn_stream_set_skip(stream, skip_handler_apr);
  svn_stream_set_mark(stream, mark_handler_apr);
  svn_stream_set_seek(stream, seek_handler_apr);
  svn_stream__set_is_buffered(stream, is_buffered_handler_apr);
  stream->file = file;

  if (! disown)
    svn_stream_set_close(stream, close_handler_apr);

  return stream;
}

apr_file_t *
svn_stream__aprfile(svn_stream_t *stream)
{
  return stream->file;
}


/* Compressed stream support */

#define ZBUFFER_SIZE 4096       /* The size of the buffer the
                                   compressed stream uses to read from
                                   the substream. Basically an
                                   arbitrary value, picked to be about
                                   page-sized. */

struct zbaton {
  z_stream *in;                 /* compressed stream for reading */
  z_stream *out;                /* compressed stream for writing */
  svn_read_fn_t read;           /* substream's read function */
  svn_write_fn_t write;         /* substream's write function */
  svn_close_fn_t close;         /* substream's close function */
  void *read_buffer;            /* buffer   used   for  reading   from
                                   substream */
  int read_flush;               /* what flush mode to use while
                                   reading */
  apr_pool_t *pool;             /* The pool this baton is allocated
                                   on */
  void *subbaton;               /* The substream's baton */
};

/* zlib alloc function. opaque is the pool we need. */
static voidpf
zalloc(voidpf opaque, uInt items, uInt size)
{
  apr_pool_t *pool = opaque;

  return apr_palloc(pool, items * size);
}

/* zlib free function */
static void
zfree(voidpf opaque, voidpf address)
{
  /* Empty, since we allocate on the pool */
}

/* Helper function to figure out the sync mode */
static svn_error_t *
read_helper_gz(svn_read_fn_t read_fn,
               void *baton,
               char *buffer,
               uInt *len, int *zflush)
{
  uInt orig_len = *len;

  /* There's no reason this value should grow bigger than the range of
     uInt, but Subversion's API requires apr_size_t. */
  apr_size_t apr_len = (apr_size_t) *len;

  SVN_ERR((*read_fn)(baton, buffer, &apr_len));

  /* Type cast back to uInt type that zlib uses.  On LP64 platforms
     apr_size_t will be bigger than uInt. */
  *len = (uInt) apr_len;

  /* I wanted to use Z_FINISH here, but we need to know our buffer is
     big enough */
  *zflush = (*len) < orig_len ? Z_SYNC_FLUSH : Z_SYNC_FLUSH;

  return SVN_NO_ERROR;
}

/* Handle reading from a compressed stream */
static svn_error_t *
read_handler_gz(void *baton, char *buffer, apr_size_t *len)
{
  struct zbaton *btn = baton;
  int zerr;

  if (btn->in == NULL)
    {
      btn->in = apr_palloc(btn->pool, sizeof(z_stream));
      btn->in->zalloc = zalloc;
      btn->in->zfree = zfree;
      btn->in->opaque = btn->pool;
      btn->read_buffer = apr_palloc(btn->pool, ZBUFFER_SIZE);
      btn->in->next_in = btn->read_buffer;
      btn->in->avail_in = ZBUFFER_SIZE;

      SVN_ERR(read_helper_gz(btn->read, btn->subbaton, btn->read_buffer,
                             &btn->in->avail_in, &btn->read_flush));

      zerr = inflateInit(btn->in);
      SVN_ERR(svn_error__wrap_zlib(zerr, "inflateInit", btn->in->msg));
    }

  btn->in->next_out = (Bytef *) buffer;
  btn->in->avail_out = (uInt) *len;

  while (btn->in->avail_out > 0)
    {
      if (btn->in->avail_in <= 0)
        {
          btn->in->avail_in = ZBUFFER_SIZE;
          btn->in->next_in = btn->read_buffer;
          SVN_ERR(read_helper_gz(btn->read, btn->subbaton, btn->read_buffer,
                                 &btn->in->avail_in, &btn->read_flush));
        }

      /* Short read means underlying stream has run out. */
      if (btn->in->avail_in == 0)
        {
          *len = 0;
          return SVN_NO_ERROR;
        }

      zerr = inflate(btn->in, btn->read_flush);
      if (zerr == Z_STREAM_END)
        break;
      else if (zerr != Z_OK)
        return svn_error_trace(svn_error__wrap_zlib(zerr, "inflate",
                                                    btn->in->msg));
    }

  *len -= btn->in->avail_out;
  return SVN_NO_ERROR;
}

/* Compress data and write it to the substream */
static svn_error_t *
write_handler_gz(void *baton, const char *buffer, apr_size_t *len)
{
  struct zbaton *btn = baton;
  apr_pool_t *subpool;
  void *write_buf;
  apr_size_t buf_size, write_len;
  int zerr;

  if (btn->out == NULL)
    {
      btn->out = apr_palloc(btn->pool, sizeof(z_stream));
      btn->out->zalloc = zalloc;
      btn->out->zfree = zfree;
      btn->out->opaque =  btn->pool;

      zerr = deflateInit(btn->out, Z_DEFAULT_COMPRESSION);
      SVN_ERR(svn_error__wrap_zlib(zerr, "deflateInit", btn->out->msg));
    }

  /* The largest buffer we should need is 0.1% larger than the
     compressed data, + 12 bytes. This info comes from zlib.h.  */
  buf_size = *len + (*len / 1000) + 13;
  subpool = svn_pool_create(btn->pool);
  write_buf = apr_palloc(subpool, buf_size);

  btn->out->next_in = (Bytef *) buffer;  /* Casting away const! */
  btn->out->avail_in = (uInt) *len;

  while (btn->out->avail_in > 0)
    {
      btn->out->next_out = write_buf;
      btn->out->avail_out = (uInt) buf_size;

      zerr = deflate(btn->out, Z_NO_FLUSH);
      SVN_ERR(svn_error__wrap_zlib(zerr, "deflate", btn->out->msg));
      write_len = buf_size - btn->out->avail_out;
      if (write_len > 0)
        SVN_ERR(btn->write(btn->subbaton, write_buf, &write_len));
    }

  svn_pool_destroy(subpool);

  return SVN_NO_ERROR;
}

/* Handle flushing and closing the stream */
static svn_error_t *
close_handler_gz(void *baton)
{
  struct zbaton *btn = baton;
  int zerr;

  if (btn->in != NULL)
    {
      zerr = inflateEnd(btn->in);
      SVN_ERR(svn_error__wrap_zlib(zerr, "inflateEnd", btn->in->msg));
    }

  if (btn->out != NULL)
    {
      void *buf;
      apr_size_t write_len;

      buf = apr_palloc(btn->pool, ZBUFFER_SIZE);

      while (TRUE)
        {
          btn->out->next_out = buf;
          btn->out->avail_out = ZBUFFER_SIZE;

          zerr = deflate(btn->out, Z_FINISH);
          if (zerr != Z_STREAM_END && zerr != Z_OK)
            return svn_error_trace(svn_error__wrap_zlib(zerr, "deflate",
                                                        btn->out->msg));
          write_len = ZBUFFER_SIZE - btn->out->avail_out;
          if (write_len > 0)
            SVN_ERR(btn->write(btn->subbaton, buf, &write_len));
          if (zerr == Z_STREAM_END)
            break;
        }

      zerr = deflateEnd(btn->out);
      SVN_ERR(svn_error__wrap_zlib(zerr, "deflateEnd", btn->out->msg));
    }

  if (btn->close != NULL)
    return svn_error_trace(btn->close(btn->subbaton));
  else
    return SVN_NO_ERROR;
}


svn_stream_t *
svn_stream_compressed(svn_stream_t *stream, apr_pool_t *pool)
{
  struct svn_stream_t *zstream;
  struct zbaton *baton;

  assert(stream != NULL);

  baton = apr_palloc(pool, sizeof(*baton));
  baton->in = baton->out = NULL;
  baton->read = stream->read_fn;
  baton->write = stream->write_fn;
  baton->close = stream->close_fn;
  baton->subbaton = stream->baton;
  baton->pool = pool;
  baton->read_buffer = NULL;
  baton->read_flush = Z_SYNC_FLUSH;

  zstream = svn_stream_create(baton, pool);
  svn_stream_set_read(zstream, read_handler_gz);
  svn_stream_set_write(zstream, write_handler_gz);
  svn_stream_set_close(zstream, close_handler_gz);

  return zstream;
}


/* Checksummed stream support */

struct checksum_stream_baton
{
  svn_checksum_ctx_t *read_ctx, *write_ctx;
  svn_checksum_t **read_checksum;  /* Output value. */
  svn_checksum_t **write_checksum;  /* Output value. */
  svn_stream_t *proxy;

  /* True if more data should be read when closing the stream. */
  svn_boolean_t read_more;

  /* Pool to allocate read buffer and output values from. */
  apr_pool_t *pool;
};

static svn_error_t *
read_handler_checksum(void *baton, char *buffer, apr_size_t *len)
{
  struct checksum_stream_baton *btn = baton;
  apr_size_t saved_len = *len;

  SVN_ERR(svn_stream_read(btn->proxy, buffer, len));

  if (btn->read_checksum)
    SVN_ERR(svn_checksum_update(btn->read_ctx, buffer, *len));

  if (saved_len != *len)
    btn->read_more = FALSE;

  return SVN_NO_ERROR;
}


static svn_error_t *
write_handler_checksum(void *baton, const char *buffer, apr_size_t *len)
{
  struct checksum_stream_baton *btn = baton;

  if (btn->write_checksum && *len > 0)
    SVN_ERR(svn_checksum_update(btn->write_ctx, buffer, *len));

  return svn_error_trace(svn_stream_write(btn->proxy, buffer, len));
}


static svn_error_t *
close_handler_checksum(void *baton)
{
  struct checksum_stream_baton *btn = baton;

  /* If we're supposed to drain the stream, do so before finalizing the
     checksum. */
  if (btn->read_more)
    {
      char *buf = apr_palloc(btn->pool, SVN__STREAM_CHUNK_SIZE);
      apr_size_t len = SVN__STREAM_CHUNK_SIZE;

      do
        {
          SVN_ERR(read_handler_checksum(baton, buf, &len));
        }
      while (btn->read_more);
    }

  if (btn->read_ctx)
    SVN_ERR(svn_checksum_final(btn->read_checksum, btn->read_ctx, btn->pool));

  if (btn->write_ctx)
    SVN_ERR(svn_checksum_final(btn->write_checksum, btn->write_ctx, btn->pool));

  return svn_error_trace(svn_stream_close(btn->proxy));
}


svn_stream_t *
svn_stream_checksummed2(svn_stream_t *stream,
                        svn_checksum_t **read_checksum,
                        svn_checksum_t **write_checksum,
                        svn_checksum_kind_t checksum_kind,
                        svn_boolean_t read_all,
                        apr_pool_t *pool)
{
  svn_stream_t *s;
  struct checksum_stream_baton *baton;

  if (read_checksum == NULL && write_checksum == NULL)
    return stream;

  baton = apr_palloc(pool, sizeof(*baton));
  if (read_checksum)
    baton->read_ctx = svn_checksum_ctx_create(checksum_kind, pool);
  else
    baton->read_ctx = NULL;

  if (write_checksum)
    baton->write_ctx = svn_checksum_ctx_create(checksum_kind, pool);
  else
    baton->write_ctx = NULL;

  baton->read_checksum = read_checksum;
  baton->write_checksum = write_checksum;
  baton->proxy = stream;
  baton->read_more = read_all;
  baton->pool = pool;

  s = svn_stream_create(baton, pool);
  svn_stream_set_read(s, read_handler_checksum);
  svn_stream_set_write(s, write_handler_checksum);
  svn_stream_set_close(s, close_handler_checksum);
  return s;
}

struct md5_stream_baton
{
  const unsigned char **read_digest;
  const unsigned char **write_digest;
  svn_checksum_t *read_checksum;
  svn_checksum_t *write_checksum;
  svn_stream_t *proxy;
  apr_pool_t *pool;
};

static svn_error_t *
read_handler_md5(void *baton, char *buffer, apr_size_t *len)
{
  struct md5_stream_baton *btn = baton;
  return svn_error_trace(svn_stream_read(btn->proxy, buffer, len));
}

static svn_error_t *
skip_handler_md5(void *baton, apr_size_t len)
{
  struct md5_stream_baton *btn = baton;
  return svn_error_trace(svn_stream_skip(btn->proxy, len));
}

static svn_error_t *
write_handler_md5(void *baton, const char *buffer, apr_size_t *len)
{
  struct md5_stream_baton *btn = baton;
  return svn_error_trace(svn_stream_write(btn->proxy, buffer, len));
}

static svn_error_t *
close_handler_md5(void *baton)
{
  struct md5_stream_baton *btn = baton;

  SVN_ERR(svn_stream_close(btn->proxy));

  if (btn->read_digest)
    *btn->read_digest
      = apr_pmemdup(btn->pool, btn->read_checksum->digest,
                    APR_MD5_DIGESTSIZE);

  if (btn->write_digest)
    *btn->write_digest
      = apr_pmemdup(btn->pool, btn->write_checksum->digest,
                    APR_MD5_DIGESTSIZE);

  return SVN_NO_ERROR;
}


svn_stream_t *
svn_stream_checksummed(svn_stream_t *stream,
                       const unsigned char **read_digest,
                       const unsigned char **write_digest,
                       svn_boolean_t read_all,
                       apr_pool_t *pool)
{
  svn_stream_t *s;
  struct md5_stream_baton *baton;

  if (! read_digest && ! write_digest)
    return stream;

  baton = apr_palloc(pool, sizeof(*baton));
  baton->read_digest = read_digest;
  baton->write_digest = write_digest;
  baton->pool = pool;

  /* Set BATON->proxy to a stream that will fill in BATON->read_checksum
   * and BATON->write_checksum (if we want them) when it is closed. */
  baton->proxy
    = svn_stream_checksummed2(stream,
                              read_digest ? &baton->read_checksum : NULL,
                              write_digest ? &baton->write_checksum : NULL,
                              svn_checksum_md5,
                              read_all, pool);

  /* Create a stream that will forward its read/write/close operations to
   * BATON->proxy and will fill in *READ_DIGEST and *WRITE_DIGEST (if we
   * want them) after it closes BATON->proxy. */
  s = svn_stream_create(baton, pool);
  svn_stream_set_read(s, read_handler_md5);
  svn_stream_set_skip(s, skip_handler_md5);
  svn_stream_set_write(s, write_handler_md5);
  svn_stream_set_close(s, close_handler_md5);
  return s;
}


/* Miscellaneous stream functions. */
struct stringbuf_stream_baton
{
  svn_stringbuf_t *str;
  apr_size_t amt_read;
};

/* svn_stream_mark_t for streams backed by stringbufs. */
struct stringbuf_stream_mark {
    apr_size_t pos;
};

static svn_error_t *
read_handler_stringbuf(void *baton, char *buffer, apr_size_t *len)
{
  struct stringbuf_stream_baton *btn = baton;
  apr_size_t left_to_read = btn->str->len - btn->amt_read;

  *len = (*len > left_to_read) ? left_to_read : *len;
  memcpy(buffer, btn->str->data + btn->amt_read, *len);
  btn->amt_read += *len;
  return SVN_NO_ERROR;
}

static svn_error_t *
skip_handler_stringbuf(void *baton, apr_size_t len)
{
  struct stringbuf_stream_baton *btn = baton;
  apr_size_t left_to_read = btn->str->len - btn->amt_read;

  len = (len > left_to_read) ? left_to_read : len;
  btn->amt_read += len;
  return SVN_NO_ERROR;
}

static svn_error_t *
write_handler_stringbuf(void *baton, const char *data, apr_size_t *len)
{
  struct stringbuf_stream_baton *btn = baton;

  svn_stringbuf_appendbytes(btn->str, data, *len);
  return SVN_NO_ERROR;
}

static svn_error_t *
mark_handler_stringbuf(void *baton, svn_stream_mark_t **mark, apr_pool_t *pool)
{
  struct stringbuf_stream_baton *btn;
  struct stringbuf_stream_mark *stringbuf_stream_mark;

  btn = baton;

  stringbuf_stream_mark = apr_palloc(pool, sizeof(*stringbuf_stream_mark));
  stringbuf_stream_mark->pos = btn->amt_read;
  *mark = (svn_stream_mark_t *)stringbuf_stream_mark;
  return SVN_NO_ERROR;
}

static svn_error_t *
seek_handler_stringbuf(void *baton, const svn_stream_mark_t *mark)
{
  struct stringbuf_stream_baton *btn = baton;

  if (mark != NULL)
    {
      const struct stringbuf_stream_mark *stringbuf_stream_mark;

      stringbuf_stream_mark = (const struct stringbuf_stream_mark *)mark;
      btn->amt_read = stringbuf_stream_mark->pos;
    }
  else
    btn->amt_read = 0;

  return SVN_NO_ERROR;
}

static svn_boolean_t
is_buffered_handler_stringbuf(void *baton)
{
  return TRUE;
}

svn_stream_t *
svn_stream_from_stringbuf(svn_stringbuf_t *str,
                          apr_pool_t *pool)
{
  svn_stream_t *stream;
  struct stringbuf_stream_baton *baton;

  if (! str)
    return svn_stream_empty(pool);

  baton = apr_palloc(pool, sizeof(*baton));
  baton->str = str;
  baton->amt_read = 0;
  stream = svn_stream_create(baton, pool);
  svn_stream_set_read(stream, read_handler_stringbuf);
  svn_stream_set_skip(stream, skip_handler_stringbuf);
  svn_stream_set_write(stream, write_handler_stringbuf);
  svn_stream_set_mark(stream, mark_handler_stringbuf);
  svn_stream_set_seek(stream, seek_handler_stringbuf);
  svn_stream__set_is_buffered(stream, is_buffered_handler_stringbuf);
  return stream;
}

struct string_stream_baton
{
  const svn_string_t *str;
  apr_size_t amt_read;
};

/* svn_stream_mark_t for streams backed by stringbufs. */
struct string_stream_mark {
    apr_size_t pos;
};

static svn_error_t *
read_handler_string(void *baton, char *buffer, apr_size_t *len)
{
  struct string_stream_baton *btn = baton;
  apr_size_t left_to_read = btn->str->len - btn->amt_read;

  *len = (*len > left_to_read) ? left_to_read : *len;
  memcpy(buffer, btn->str->data + btn->amt_read, *len);
  btn->amt_read += *len;
  return SVN_NO_ERROR;
}

static svn_error_t *
mark_handler_string(void *baton, svn_stream_mark_t **mark, apr_pool_t *pool)
{
  struct string_stream_baton *btn;
  struct string_stream_mark *marker;

  btn = baton;

  marker = apr_palloc(pool, sizeof(*marker));
  marker->pos = btn->amt_read;
  *mark = (svn_stream_mark_t *)marker;
  return SVN_NO_ERROR;
}

static svn_error_t *
seek_handler_string(void *baton, const svn_stream_mark_t *mark)
{
  struct string_stream_baton *btn = baton;

  if (mark != NULL)
    {
      const struct string_stream_mark *marker;

      marker = (const struct string_stream_mark *)mark;
      btn->amt_read = marker->pos;
    }
  else
    btn->amt_read = 0;

  return SVN_NO_ERROR;
}

static svn_error_t *
skip_handler_string(void *baton, apr_size_t len)
{
  struct string_stream_baton *btn = baton;
  apr_size_t left_to_read = btn->str->len - btn->amt_read;

  len = (len > left_to_read) ? left_to_read : len;
  btn->amt_read += len;
  return SVN_NO_ERROR;
}

static svn_boolean_t
is_buffered_handler_string(void *baton)
{
  return TRUE;
}

svn_stream_t *
svn_stream_from_string(const svn_string_t *str,
                       apr_pool_t *pool)
{
  svn_stream_t *stream;
  struct string_stream_baton *baton;

  if (! str)
    return svn_stream_empty(pool);

  baton = apr_palloc(pool, sizeof(*baton));
  baton->str = str;
  baton->amt_read = 0;
  stream = svn_stream_create(baton, pool);
  svn_stream_set_read(stream, read_handler_string);
  svn_stream_set_mark(stream, mark_handler_string);
  svn_stream_set_seek(stream, seek_handler_string);
  svn_stream_set_skip(stream, skip_handler_string);
  svn_stream__set_is_buffered(stream, is_buffered_handler_string);
  return stream;
}


svn_error_t *
svn_stream_for_stdin(svn_stream_t **in, apr_pool_t *pool)
{
  apr_file_t *stdin_file;
  apr_status_t apr_err;

  apr_err = apr_file_open_stdin(&stdin_file, pool);
  if (apr_err)
    return svn_error_wrap_apr(apr_err, "Can't open stdin");

  *in = svn_stream_from_aprfile2(stdin_file, TRUE, pool);

  return SVN_NO_ERROR;
}


svn_error_t *
svn_stream_for_stdout(svn_stream_t **out, apr_pool_t *pool)
{
  apr_file_t *stdout_file;
  apr_status_t apr_err;

  apr_err = apr_file_open_stdout(&stdout_file, pool);
  if (apr_err)
    return svn_error_wrap_apr(apr_err, "Can't open stdout");

  *out = svn_stream_from_aprfile2(stdout_file, TRUE, pool);

  return SVN_NO_ERROR;
}


svn_error_t *
svn_stream_for_stderr(svn_stream_t **err, apr_pool_t *pool)
{
  apr_file_t *stderr_file;
  apr_status_t apr_err;

  apr_err = apr_file_open_stderr(&stderr_file, pool);
  if (apr_err)
    return svn_error_wrap_apr(apr_err, "Can't open stderr");

  *err = svn_stream_from_aprfile2(stderr_file, TRUE, pool);

  return SVN_NO_ERROR;
}


svn_error_t *
svn_string_from_stream(svn_string_t **result,
                       svn_stream_t *stream,
                       apr_pool_t *result_pool,
                       apr_pool_t *scratch_pool)
{
  svn_stringbuf_t *work = svn_stringbuf_create_ensure(SVN__STREAM_CHUNK_SIZE,
                                                      result_pool);
  char *buffer = apr_palloc(scratch_pool, SVN__STREAM_CHUNK_SIZE);

  while (1)
    {
      apr_size_t len = SVN__STREAM_CHUNK_SIZE;

      SVN_ERR(svn_stream_read(stream, buffer, &len));
      svn_stringbuf_appendbytes(work, buffer, len);

      if (len < SVN__STREAM_CHUNK_SIZE)
        break;
    }

  SVN_ERR(svn_stream_close(stream));

  *result = apr_palloc(result_pool, sizeof(**result));
  (*result)->data = work->data;
  (*result)->len = work->len;

  return SVN_NO_ERROR;
}


/* These are somewhat arbirary, if we ever get good empirical data as to
   actually valid values, feel free to update them. */
#define BUFFER_BLOCK_SIZE 1024
#define BUFFER_MAX_SIZE 100000

svn_stream_t *
svn_stream_buffered(apr_pool_t *result_pool)
{
  return svn_stream__from_spillbuf(BUFFER_BLOCK_SIZE, BUFFER_MAX_SIZE,
                                   result_pool);
}


/*** Lazyopen Streams ***/

/* Custom baton for lazyopen-style wrapper streams. */
typedef struct lazyopen_baton_t {

  /* Callback function and baton for opening the wrapped stream. */
  svn_stream_lazyopen_func_t open_func;
  void *open_baton;

  /* The wrapped stream, or NULL if the stream hasn't yet been
     opened. */
  svn_stream_t *real_stream;
  apr_pool_t *pool;

  /* Whether to open the wrapped stream on a close call. */
  svn_boolean_t open_on_close;

} lazyopen_baton_t;


/* Use B->open_func/baton to create and set B->real_stream iff it
   isn't already set. */
static svn_error_t *
lazyopen_if_unopened(lazyopen_baton_t *b)
{
  if (b->real_stream == NULL)
    {
      svn_stream_t *stream;
      apr_pool_t *scratch_pool = svn_pool_create(b->pool);

      SVN_ERR(b->open_func(&stream, b->open_baton,
                           b->pool, scratch_pool));

      svn_pool_destroy(scratch_pool);

      b->real_stream = stream;
    }

  return SVN_NO_ERROR;
}

/* Implements svn_read_fn_t */
static svn_error_t *
read_handler_lazyopen(void *baton,
                      char *buffer,
                      apr_size_t *len)
{
  lazyopen_baton_t *b = baton;

  SVN_ERR(lazyopen_if_unopened(b));
  SVN_ERR(svn_stream_read(b->real_stream, buffer, len));

  return SVN_NO_ERROR;
}

/* Implements svn_stream_skip_fn_t */
static svn_error_t *
skip_handler_lazyopen(void *baton,
                      apr_size_t len)
{
  lazyopen_baton_t *b = baton;

  SVN_ERR(lazyopen_if_unopened(b));
  SVN_ERR(svn_stream_skip(b->real_stream, len));

  return SVN_NO_ERROR;
}

/* Implements svn_write_fn_t */
static svn_error_t *
write_handler_lazyopen(void *baton,
                       const char *data,
                       apr_size_t *len)
{
  lazyopen_baton_t *b = baton;

  SVN_ERR(lazyopen_if_unopened(b));
  SVN_ERR(svn_stream_write(b->real_stream, data, len));

  return SVN_NO_ERROR;
}

/* Implements svn_close_fn_t */
static svn_error_t *
close_handler_lazyopen(void *baton)
{
  lazyopen_baton_t *b = baton;

  if (b->open_on_close)
    SVN_ERR(lazyopen_if_unopened(b));
  if (b->real_stream)
    SVN_ERR(svn_stream_close(b->real_stream));

  return SVN_NO_ERROR;
}

/* Implements svn_stream_mark_fn_t */
static svn_error_t *
mark_handler_lazyopen(void *baton,
                      svn_stream_mark_t **mark,
                      apr_pool_t *pool)
{
  lazyopen_baton_t *b = baton;

  SVN_ERR(lazyopen_if_unopened(b));
  SVN_ERR(svn_stream_mark(b->real_stream, mark, pool));

  return SVN_NO_ERROR;
}

/* Implements svn_stream_seek_fn_t */
static svn_error_t *
seek_handler_lazyopen(void *baton,
                      const svn_stream_mark_t *mark)
{
  lazyopen_baton_t *b = baton;

  SVN_ERR(lazyopen_if_unopened(b));
  SVN_ERR(svn_stream_seek(b->real_stream, mark));

  return SVN_NO_ERROR;
}

/* Implements svn_stream__is_buffered_fn_t */
static svn_boolean_t
is_buffered_lazyopen(void *baton)
{
  lazyopen_baton_t *b = baton;

  /* No lazy open as we cannot handle an open error. */
  if (!b->real_stream)
    return FALSE;

  return svn_stream__is_buffered(b->real_stream);
}

svn_stream_t *
svn_stream_lazyopen_create(svn_stream_lazyopen_func_t open_func,
                           void *open_baton,
                           svn_boolean_t open_on_close,
                           apr_pool_t *result_pool)
{
  lazyopen_baton_t *lob = apr_pcalloc(result_pool, sizeof(*lob));
  svn_stream_t *stream;

  lob->open_func = open_func;
  lob->open_baton = open_baton;
  lob->real_stream = NULL;
  lob->pool = result_pool;
  lob->open_on_close = open_on_close;

  stream = svn_stream_create(lob, result_pool);
  svn_stream_set_read(stream, read_handler_lazyopen);
  svn_stream_set_skip(stream, skip_handler_lazyopen);
  svn_stream_set_write(stream, write_handler_lazyopen);
  svn_stream_set_close(stream, close_handler_lazyopen);
  svn_stream_set_mark(stream, mark_handler_lazyopen);
  svn_stream_set_seek(stream, seek_handler_lazyopen);
  svn_stream__set_is_buffered(stream, is_buffered_lazyopen);

  return stream;
}