marshal.c   [plain text]

/*
 * marshal.c :  Marshalling routines for Subversion protocol
 *
 * ====================================================================
 * Copyright (c) 2000-2007 CollabNet.  All rights reserved.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution.  The terms
 * are also available at http://subversion.tigris.org/license-1.html.
 * If newer versions of this license are posted there, you may use a
 * newer version instead, at your option.
 *
 * This software consists of voluntary contributions made by many
 * individuals.  For exact contribution history, see the revision
 * history and logs, available at http://subversion.tigris.org/.
 * ====================================================================
 */



#include <assert.h>
#include <stdlib.h>

#define APR_WANT_STRFUNC
#include <apr_want.h>
#include <apr_general.h>
#include <apr_lib.h>
#include <apr_strings.h>

#include "svn_types.h"
#include "svn_string.h"
#include "svn_error.h"
#include "svn_pools.h"
#include "svn_ra_svn.h"
#include "svn_private_config.h"

#include "ra_svn.h"

#define svn_iswhitespace(c) ((c) == ' ' || (c) == '\n')

/* --- CONNECTION INITIALIZATION --- */

svn_ra_svn_conn_t *svn_ra_svn_create_conn(apr_socket_t *sock,
                                          apr_file_t *in_file,
                                          apr_file_t *out_file,
                                          apr_pool_t *pool)
{
  svn_ra_svn_conn_t *conn = apr_palloc(pool, sizeof(*conn));

  assert((sock && !in_file && !out_file) || (!sock && in_file && out_file));
#ifdef SVN_HAVE_SASL
  conn->sock = sock;
  conn->encrypted = FALSE;
#endif
  conn->session = NULL;
  conn->read_ptr = conn->read_buf;
  conn->read_end = conn->read_buf;
  conn->write_pos = 0;
  conn->block_handler = NULL;
  conn->block_baton = NULL;
  conn->capabilities = apr_hash_make(pool);
  conn->pool = pool;

  if (sock != NULL)
    {
      apr_sockaddr_t *sa;
      conn->stream = svn_ra_svn__stream_from_sock(sock, pool);
      if (!(apr_socket_addr_get(&sa, APR_REMOTE, sock) == APR_SUCCESS
            && apr_sockaddr_ip_get(&conn->remote_ip, sa) == APR_SUCCESS))
        conn->remote_ip = NULL;
    }
  else
    {
      conn->stream = svn_ra_svn__stream_from_files(in_file, out_file, pool);
      conn->remote_ip = NULL;
    }

  return conn;
}

svn_error_t *svn_ra_svn_set_capabilities(svn_ra_svn_conn_t *conn,
                                         apr_array_header_t *list)
{
  int i;
  svn_ra_svn_item_t *item;
  const char *word;

  for (i = 0; i < list->nelts; i++)
    {
      item = &APR_ARRAY_IDX(list, i, svn_ra_svn_item_t);
      if (item->kind != SVN_RA_SVN_WORD)
        return svn_error_create(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                                _("Capability entry is not a word"));
      word = apr_pstrdup(conn->pool, item->u.word);
      apr_hash_set(conn->capabilities, word, APR_HASH_KEY_STRING, word);
    }
  return SVN_NO_ERROR;
}

svn_boolean_t svn_ra_svn_has_capability(svn_ra_svn_conn_t *conn,
                                        const char *capability)
{
  return (apr_hash_get(conn->capabilities, capability,
                       APR_HASH_KEY_STRING) != NULL);
}

const char *svn_ra_svn_conn_remote_host(svn_ra_svn_conn_t *conn)
{
  return conn->remote_ip;
}

void
svn_ra_svn__set_block_handler(svn_ra_svn_conn_t *conn,
                              ra_svn_block_handler_t handler,
                              void *baton)
{
  apr_interval_time_t interval = (handler) ? 0 : -1;

  conn->block_handler = handler;
  conn->block_baton = baton;
  svn_ra_svn__stream_timeout(conn->stream, interval);
}

svn_boolean_t svn_ra_svn__input_waiting(svn_ra_svn_conn_t *conn,
                                        apr_pool_t *pool)
{
  return svn_ra_svn__stream_pending(conn->stream);
}

/* --- WRITE BUFFER MANAGEMENT --- */

/* Write bytes into the write buffer until either the write buffer is
 * full or we reach END. */
static const char *writebuf_push(svn_ra_svn_conn_t *conn, const char *data,
                                 const char *end)
{
  apr_ssize_t buflen, copylen;

  buflen = sizeof(conn->write_buf) - conn->write_pos;
  copylen = (buflen < end - data) ? buflen : end - data;
  memcpy(conn->write_buf + conn->write_pos, data, copylen);
  conn->write_pos += copylen;
  return data + copylen;
}

/* Write data to socket or output file as appropriate. */
static svn_error_t *writebuf_output(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                    const char *data, apr_size_t len)
{
  const char *end = data + len;
  apr_size_t count;
  apr_pool_t *subpool = NULL;
  svn_ra_svn__session_baton_t *session = conn->session;

  while (data < end)
    {
      count = end - data;

      if (session && session->callbacks &&
          session->callbacks->cancel_func)
        SVN_ERR((session->callbacks->cancel_func)
                   (session->callbacks_baton));

      SVN_ERR(svn_ra_svn__stream_write(conn->stream, data, &count));
      if (count == 0)
        {
          if (!subpool)
            subpool = svn_pool_create(pool);
          else
            svn_pool_clear(subpool);
          SVN_ERR(conn->block_handler(conn, subpool, conn->block_baton));
        }
      data += count;

      if (session)
        {
          const svn_ra_callbacks2_t *cb = session->callbacks;
          session->bytes_written += count;

          if (cb && cb->progress_func)
            (cb->progress_func)(session->bytes_written + session->bytes_read,
                                -1, cb->progress_baton, subpool);
        }
    }

  if (subpool)
    svn_pool_destroy(subpool);
  return SVN_NO_ERROR;
}

/* Write data from the write buffer out to the socket. */
static svn_error_t *writebuf_flush(svn_ra_svn_conn_t *conn, apr_pool_t *pool)
{
  int write_pos = conn->write_pos;

  /* Clear conn->write_pos first in case the block handler does a read. */
  conn->write_pos = 0;
  SVN_ERR(writebuf_output(conn, pool, conn->write_buf, write_pos));
  return SVN_NO_ERROR;
}

static svn_error_t *writebuf_write(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                   const char *data, apr_size_t len)
{
  const char *end = data + len;

  if (conn->write_pos > 0 && conn->write_pos + len > sizeof(conn->write_buf))
    {
      /* Fill and then empty the write buffer. */
      data = writebuf_push(conn, data, end);
      SVN_ERR(writebuf_flush(conn, pool));
    }

  if (end - data > (apr_ssize_t)sizeof(conn->write_buf))
    SVN_ERR(writebuf_output(conn, pool, data, end - data));
  else
    writebuf_push(conn, data, end);
  return SVN_NO_ERROR;
}

static svn_error_t *writebuf_printf(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                    const char *fmt, ...)
  __attribute__ ((format(printf, 3, 4)));
static svn_error_t *writebuf_printf(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                    const char *fmt, ...)
{
  va_list ap;
  char *str;

  va_start(ap, fmt);
  str = apr_pvsprintf(pool, fmt, ap);
  va_end(ap);
  return writebuf_write(conn, pool, str, strlen(str));
}

/* --- READ BUFFER MANAGEMENT --- */

/* Read bytes into DATA until either the read buffer is empty or
 * we reach END. */
static char *readbuf_drain(svn_ra_svn_conn_t *conn, char *data, char *end)
{
  apr_ssize_t buflen, copylen;

  buflen = conn->read_end - conn->read_ptr;
  copylen = (buflen < end - data) ? buflen : end - data;
  memcpy(data, conn->read_ptr, copylen);
  conn->read_ptr += copylen;
  return data + copylen;
}

/* Read data from socket or input file as appropriate. */
static svn_error_t *readbuf_input(svn_ra_svn_conn_t *conn, char *data,
                                  apr_size_t *len, apr_pool_t *pool)
{
  svn_ra_svn__session_baton_t *session = conn->session;

  if (session && session->callbacks &&
      session->callbacks->cancel_func)
    SVN_ERR((session->callbacks->cancel_func)
              (session->callbacks_baton));

  SVN_ERR(svn_ra_svn__stream_read(conn->stream, data, len));
  if (*len == 0)
    return svn_error_create(SVN_ERR_RA_SVN_CONNECTION_CLOSED, NULL, NULL);

  if (session)
    {
      const svn_ra_callbacks2_t *cb = session->callbacks;
      session->bytes_read += *len;

      if (cb && cb->progress_func)
        (cb->progress_func)(session->bytes_read + session->bytes_written,
                            -1, cb->progress_baton, pool);
    }

  return SVN_NO_ERROR;
}

/* Read data from the socket into the read buffer, which must be empty. */
static svn_error_t *readbuf_fill(svn_ra_svn_conn_t *conn, apr_pool_t *pool)
{
  apr_size_t len;

  SVN_ERR_ASSERT(conn->read_ptr == conn->read_end);
  SVN_ERR(writebuf_flush(conn, pool));
  len = sizeof(conn->read_buf);
  SVN_ERR(readbuf_input(conn, conn->read_buf, &len, pool));
  conn->read_ptr = conn->read_buf;
  conn->read_end = conn->read_buf + len;
  return SVN_NO_ERROR;
}

static svn_error_t *readbuf_getchar(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                    char *result)
{
  if (conn->read_ptr == conn->read_end)
    SVN_ERR(readbuf_fill(conn, pool));
  *result = *conn->read_ptr++;
  return SVN_NO_ERROR;
}

static svn_error_t *readbuf_getchar_skip_whitespace(svn_ra_svn_conn_t *conn,
                                                    apr_pool_t *pool,
                                                    char *result)
{
  do
    SVN_ERR(readbuf_getchar(conn, pool, result));
  while (svn_iswhitespace(*result));
  return SVN_NO_ERROR;
}

static svn_error_t *readbuf_read(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                 char *data, apr_size_t len)
{
  char *end = data + len;
  apr_size_t count;

  /* Copy in an appropriate amount of data from the buffer. */
  data = readbuf_drain(conn, data, end);

  /* Read large chunks directly into buffer. */
  while (end - data > (apr_ssize_t)sizeof(conn->read_buf))
    {
      SVN_ERR(writebuf_flush(conn, pool));
      count = end - data;
      SVN_ERR(readbuf_input(conn, data, &count, pool));
      data += count;
    }

  while (end > data)
    {
      /* The remaining amount to read is small; fill the buffer and
       * copy from that. */
      SVN_ERR(readbuf_fill(conn, pool));
      data = readbuf_drain(conn, data, end);
    }

  return SVN_NO_ERROR;
}

static svn_error_t *readbuf_skip_leading_garbage(svn_ra_svn_conn_t *conn,
                                                 apr_pool_t *pool)
{
  char buf[256];  /* Must be smaller than sizeof(conn->read_buf) - 1. */
  const char *p, *end;
  apr_size_t len;
  svn_boolean_t lparen = FALSE;

  SVN_ERR_ASSERT(conn->read_ptr == conn->read_end);
  while (1)
    {
      /* Read some data directly from the connection input source. */
      len = sizeof(buf);
      SVN_ERR(readbuf_input(conn, buf, &len, pool));
      end = buf + len;

      /* Scan the data for '(' WS with a very simple state machine. */
      for (p = buf; p < end; p++)
        {
          if (lparen && svn_iswhitespace(*p))
            break;
          else
            lparen = (*p == '(');
        }
      if (p < end)
        break;
    }

  /* p now points to the whitespace just after the left paren.  Fake
   * up the left paren and then copy what we have into the read
   * buffer. */
  conn->read_buf[0] = '(';
  memcpy(conn->read_buf + 1, p, end - p);
  conn->read_ptr = conn->read_buf;
  conn->read_end = conn->read_buf + 1 + (end - p);
  return SVN_NO_ERROR;
}

/* --- WRITING DATA ITEMS --- */

svn_error_t *svn_ra_svn_write_number(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                     apr_uint64_t number)
{
  return writebuf_printf(conn, pool, "%" APR_UINT64_T_FMT " ", number);
}

svn_error_t *svn_ra_svn_write_string(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                     const svn_string_t *str)
{
  SVN_ERR(writebuf_printf(conn, pool, "%" APR_SIZE_T_FMT ":", str->len));
  SVN_ERR(writebuf_write(conn, pool, str->data, str->len));
  SVN_ERR(writebuf_write(conn, pool, " ", 1));
  return SVN_NO_ERROR;
}

svn_error_t *svn_ra_svn_write_cstring(svn_ra_svn_conn_t *conn,
                                      apr_pool_t *pool, const char *s)
{
  return writebuf_printf(conn, pool, "%" APR_SIZE_T_FMT ":%s ", strlen(s), s);
}

svn_error_t *svn_ra_svn_write_word(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                   const char *word)
{
  return writebuf_printf(conn, pool, "%s ", word);
}

svn_error_t *svn_ra_svn_write_proplist(svn_ra_svn_conn_t *conn,
                                       apr_pool_t *pool, apr_hash_t *props)
{
  apr_pool_t *iterpool;
  apr_hash_index_t *hi;
  const void *key;
  void *val;
  const char *propname;
  svn_string_t *propval;

  if (props)
    {
      iterpool = svn_pool_create(pool);
      for (hi = apr_hash_first(pool, props); hi; hi = apr_hash_next(hi))
        {
          svn_pool_clear(iterpool);
          apr_hash_this(hi, &key, NULL, &val);
          propname = key;
          propval = val;
          SVN_ERR(svn_ra_svn_write_tuple(conn, iterpool, "cs",
                                         propname, propval));
        }
      svn_pool_destroy(iterpool);
    }

  return SVN_NO_ERROR;
}

svn_error_t *svn_ra_svn_start_list(svn_ra_svn_conn_t *conn, apr_pool_t *pool)
{
  return writebuf_write(conn, pool, "( ", 2);
}

svn_error_t *svn_ra_svn_end_list(svn_ra_svn_conn_t *conn, apr_pool_t *pool)
{
  return writebuf_write(conn, pool, ") ", 2);
}

svn_error_t *svn_ra_svn_flush(svn_ra_svn_conn_t *conn, apr_pool_t *pool)
{
  return writebuf_flush(conn, pool);
}

/* --- WRITING TUPLES --- */

static svn_error_t *vwrite_tuple(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                 const char *fmt, va_list ap)
{
  svn_boolean_t opt = FALSE;
  svn_revnum_t rev;
  const char *cstr;
  const svn_string_t *str;

  if (*fmt == '!')
    fmt++;
  else
    SVN_ERR(svn_ra_svn_start_list(conn, pool));
  for (; *fmt; fmt++)
    {
      if (*fmt == 'n' && !opt)
        SVN_ERR(svn_ra_svn_write_number(conn, pool, va_arg(ap, apr_uint64_t)));
      else if (*fmt == 'r')
        {
          rev = va_arg(ap, svn_revnum_t);
          SVN_ERR_ASSERT(opt || SVN_IS_VALID_REVNUM(rev));
          if (SVN_IS_VALID_REVNUM(rev))
            SVN_ERR(svn_ra_svn_write_number(conn, pool, rev));
        }
      else if (*fmt == 's')
        {
          str = va_arg(ap, const svn_string_t *);
          SVN_ERR_ASSERT(opt || str);
          if (str)
            SVN_ERR(svn_ra_svn_write_string(conn, pool, str));
        }
      else if (*fmt == 'c')
        {
          cstr = va_arg(ap, const char *);
          SVN_ERR_ASSERT(opt || cstr);
          if (cstr)
            SVN_ERR(svn_ra_svn_write_cstring(conn, pool, cstr));
        }
      else if (*fmt == 'w')
        {
          cstr = va_arg(ap, const char *);
          SVN_ERR_ASSERT(opt || cstr);
          if (cstr)
            SVN_ERR(svn_ra_svn_write_word(conn, pool, cstr));
        }
      else if (*fmt == 'b' && !opt)
        {
          cstr = va_arg(ap, svn_boolean_t) ? "true" : "false";
          SVN_ERR(svn_ra_svn_write_word(conn, pool, cstr));
        }
      else if (*fmt == '?')
        opt = TRUE;
      else if (*fmt == '(' && !opt)
        SVN_ERR(svn_ra_svn_start_list(conn, pool));
      else if (*fmt == ')')
        {
          SVN_ERR(svn_ra_svn_end_list(conn, pool));
          opt = FALSE;
        }
      else if (*fmt == '!' && !*(fmt + 1))
        return SVN_NO_ERROR;
      else
        SVN_ERR_MALFUNCTION();
    }
  SVN_ERR(svn_ra_svn_end_list(conn, pool));
  return SVN_NO_ERROR;
}

svn_error_t *svn_ra_svn_write_tuple(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                    const char *fmt, ...)
{
  svn_error_t *err;
  va_list ap;

  va_start(ap, fmt);
  err = vwrite_tuple(conn, pool, fmt, ap);
  va_end(ap);
  return err;
}

/* --- READING DATA ITEMS --- */

/* Read LEN bytes from CONN into already-allocated structure ITEM.
 * Afterwards, *ITEM is of type 'SVN_RA_SVN_STRING', and its string
 * data is allocated in POOL. */
static svn_error_t *read_string(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                svn_ra_svn_item_t *item, apr_uint64_t len)
{
  char readbuf[4096];
  apr_size_t readbuf_len;
  svn_stringbuf_t *stringbuf = svn_stringbuf_create("", pool);

  /* We can't store strings longer than the maximum size of apr_size_t,
   * so check for wrapping */
  if (((apr_size_t) len) < len)
    return svn_error_create(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                            _("String length larger than maximum"));

  while (len)
    {
      readbuf_len = len > sizeof(readbuf) ? sizeof(readbuf) : (apr_size_t)len;

      SVN_ERR(readbuf_read(conn, pool, readbuf, readbuf_len));
      /* Read into a stringbuf_t to so we don't allow the sender to allocate
       * an arbitrary amount of memory without actually sending us that much
       * data */
      svn_stringbuf_appendbytes(stringbuf, readbuf, readbuf_len);
      len -= readbuf_len;
    }

  item->kind = SVN_RA_SVN_STRING;
  item->u.string = apr_palloc(pool, sizeof(*item->u.string));
  item->u.string->data = stringbuf->data;
  item->u.string->len = stringbuf->len;

  return SVN_NO_ERROR;
}

/* Given the first non-whitespace character FIRST_CHAR, read an item
 * into the already allocated structure ITEM.  LEVEL should be set
 * to 0 for the first call and is used to enforce a recurssion limit
 * on the parser. */
static svn_error_t *read_item(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                              svn_ra_svn_item_t *item, char first_char,
                              int level)
{
  char c = first_char;
  apr_uint64_t val, prev_val=0;
  svn_stringbuf_t *str;
  svn_ra_svn_item_t *listitem;

  if (++level >= 64)
    return svn_error_create(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                            _("Too many nested items"));


  /* Determine the item type and read it in.  Make sure that c is the
   * first character at the end of the item so we can test to make
   * sure it's whitespace. */
  if (apr_isdigit(c))
    {
      /* It's a number or a string.  Read the number part, either way. */
      val = c - '0';
      while (1)
        {
          prev_val = val;
          SVN_ERR(readbuf_getchar(conn, pool, &c));
          if (!apr_isdigit(c))
            break;
          val = val * 10 + (c - '0');
          if ((val / 10) != prev_val) /* val wrapped past maximum value */
            return svn_error_create(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                                    _("Number is larger than maximum"));
        }
      if (c == ':')
        {
          /* It's a string. */
          SVN_ERR(read_string(conn, pool, item, val));
          SVN_ERR(readbuf_getchar(conn, pool, &c));
        }
      else
        {
          /* It's a number. */
          item->kind = SVN_RA_SVN_NUMBER;
          item->u.number = val;
        }
    }
  else if (apr_isalpha(c))
    {
      /* It's a word. */
      str = svn_stringbuf_ncreate(&c, 1, pool);
      while (1)
        {
          SVN_ERR(readbuf_getchar(conn, pool, &c));
          if (!apr_isalnum(c) && c != '-')
            break;
          svn_stringbuf_appendbytes(str, &c, 1);
        }
      item->kind = SVN_RA_SVN_WORD;
      item->u.word = str->data;
    }
  else if (c == '(')
    {
      /* Read in the list items. */
      item->kind = SVN_RA_SVN_LIST;
      item->u.list = apr_array_make(pool, 0, sizeof(svn_ra_svn_item_t));
      while (1)
        {
          SVN_ERR(readbuf_getchar_skip_whitespace(conn, pool, &c));
          if (c == ')')
            break;
          listitem = apr_array_push(item->u.list);
          SVN_ERR(read_item(conn, pool, listitem, c, level));
        }
      SVN_ERR(readbuf_getchar(conn, pool, &c));
    }

  if (!svn_iswhitespace(c))
    return svn_error_create(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                            _("Malformed network data"));
  return SVN_NO_ERROR;
}

svn_error_t *svn_ra_svn_read_item(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                  svn_ra_svn_item_t **item)
{
  char c;

  /* Allocate space, read the first character, and then do the rest of
   * the work.  This makes sense because of the way lists are read. */
  *item = apr_palloc(pool, sizeof(**item));
  SVN_ERR(readbuf_getchar_skip_whitespace(conn, pool, &c));
  return read_item(conn, pool, *item, c, 0);
}

svn_error_t *svn_ra_svn_skip_leading_garbage(svn_ra_svn_conn_t *conn,
                                             apr_pool_t *pool)
{
  return readbuf_skip_leading_garbage(conn, pool);
}

/* --- READING AND PARSING TUPLES --- */

/* Parse a tuple of svn_ra_svn_item_t *'s.  Advance *FMT to the end of the
 * tuple specification and advance AP by the corresponding arguments. */
static svn_error_t *vparse_tuple(apr_array_header_t *items, apr_pool_t *pool,
                                 const char **fmt, va_list *ap)
{
  int count, nesting_level;
  svn_ra_svn_item_t *elt;

  for (count = 0; **fmt && count < items->nelts; (*fmt)++, count++)
    {
      /* '?' just means the tuple may stop; skip past it. */
      if (**fmt == '?')
        (*fmt)++;
      elt = &APR_ARRAY_IDX(items, count, svn_ra_svn_item_t);
      if (**fmt == 'n' && elt->kind == SVN_RA_SVN_NUMBER)
        *va_arg(*ap, apr_uint64_t *) = elt->u.number;
      else if (**fmt == 'r' && elt->kind == SVN_RA_SVN_NUMBER)
        *va_arg(*ap, svn_revnum_t *) = (svn_revnum_t) elt->u.number;
      else if (**fmt == 's' && elt->kind == SVN_RA_SVN_STRING)
        *va_arg(*ap, svn_string_t **) = elt->u.string;
      else if (**fmt == 'c' && elt->kind == SVN_RA_SVN_STRING)
        *va_arg(*ap, const char **) = elt->u.string->data;
      else if (**fmt == 'w' && elt->kind == SVN_RA_SVN_WORD)
        *va_arg(*ap, const char **) = elt->u.word;
      else if (**fmt == 'b' && elt->kind == SVN_RA_SVN_WORD)
        {
          if (strcmp(elt->u.word, "true") == 0)
            *va_arg(*ap, svn_boolean_t *) = TRUE;
          else if (strcmp(elt->u.word, "false") == 0)
            *va_arg(*ap, svn_boolean_t *) = FALSE;
          else
            break;
        }
      else if (**fmt == 'B' && elt->kind == SVN_RA_SVN_WORD)
        {
          if (strcmp(elt->u.word, "true") == 0)
            *va_arg(*ap, apr_uint64_t *) = TRUE;
          else if (strcmp(elt->u.word, "false") == 0)
            *va_arg(*ap, apr_uint64_t *) = FALSE;
          else
            break;
        }
      else if (**fmt == 'l' && elt->kind == SVN_RA_SVN_LIST)
        *va_arg(*ap, apr_array_header_t **) = elt->u.list;
      else if (**fmt == '(' && elt->kind == SVN_RA_SVN_LIST)
        {
          (*fmt)++;
          SVN_ERR(vparse_tuple(elt->u.list, pool, fmt, ap));
        }
      else if (**fmt == ')')
        return SVN_NO_ERROR;
      else
        break;
    }
  if (**fmt == '?')
    {
      nesting_level = 0;
      for (; **fmt; (*fmt)++)
        {
          switch (**fmt)
            {
            case '?':
              break;
            case 'r':
              *va_arg(*ap, svn_revnum_t *) = SVN_INVALID_REVNUM;
              break;
            case 's':
              *va_arg(*ap, svn_string_t **) = NULL;
              break;
            case 'c':
            case 'w':
              *va_arg(*ap, const char **) = NULL;
              break;
            case 'l':
              *va_arg(*ap, apr_array_header_t **) = NULL;
              break;
            case 'B':
            case 'n':
              *va_arg(*ap, apr_uint64_t *) = SVN_RA_SVN_UNSPECIFIED_NUMBER;
              break;
            case '(':
              nesting_level++;
              break;
            case ')':
              if (--nesting_level < 0)
                return SVN_NO_ERROR;
              break;
            default:
              SVN_ERR_MALFUNCTION();
            }
        }
    }
  if (**fmt && **fmt != ')')
    return svn_error_create(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                            _("Malformed network data"));
  return SVN_NO_ERROR;
}

svn_error_t *svn_ra_svn_parse_tuple(apr_array_header_t *list,
                                    apr_pool_t *pool,
                                    const char *fmt, ...)
{
  svn_error_t *err;
  va_list ap;

  va_start(ap, fmt);
  err = vparse_tuple(list, pool, &fmt, &ap);
  va_end(ap);
  return err;
}

svn_error_t *svn_ra_svn_read_tuple(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                   const char *fmt, ...)
{
  va_list ap;
  svn_ra_svn_item_t *item;
  svn_error_t *err;

  SVN_ERR(svn_ra_svn_read_item(conn, pool, &item));
  if (item->kind != SVN_RA_SVN_LIST)
    return svn_error_create(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                            _("Malformed network data"));
  va_start(ap, fmt);
  err = vparse_tuple(item->u.list, pool, &fmt, &ap);
  va_end(ap);
  return err;
}

svn_error_t *svn_ra_svn_parse_proplist(apr_array_header_t *list,
                                       apr_pool_t *pool,
                                       apr_hash_t **props)
{
  char *name;
  svn_string_t *value;
  svn_ra_svn_item_t *elt;
  int i;

  *props = apr_hash_make(pool);
  for (i = 0; i < list->nelts; i++)
    {
      elt = &APR_ARRAY_IDX(list, i, svn_ra_svn_item_t);
      if (elt->kind != SVN_RA_SVN_LIST)
        return svn_error_create(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                                _("Proplist element not a list"));
      SVN_ERR(svn_ra_svn_parse_tuple(elt->u.list, pool, "cs", &name, &value));
      apr_hash_set(*props, name, APR_HASH_KEY_STRING, value);
    }

  return SVN_NO_ERROR;
}


/* --- READING AND WRITING COMMANDS AND RESPONSES --- */

svn_error_t *svn_ra_svn__locate_real_error_child(svn_error_t *err)
{
  svn_error_t *this_link;

  SVN_ERR_ASSERT(err);

  for (this_link = err;
       this_link && (this_link->apr_err == SVN_ERR_RA_SVN_CMD_ERR);
       this_link = this_link->child)
    ;

  SVN_ERR_ASSERT(this_link);
  return this_link;
}

svn_error_t *svn_ra_svn__handle_failure_status(apr_array_header_t *params,
                                               apr_pool_t *pool)
{
  const char *message, *file;
  svn_error_t *err = NULL;
  svn_ra_svn_item_t *elt;
  int i;
  apr_uint64_t apr_err, line;
  apr_pool_t *subpool = svn_pool_create(pool);

  if (params->nelts == 0)
    return svn_error_create(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                            _("Empty error list"));

  /* Rebuild the error list from the end, to avoid reversing the order. */
  for (i = params->nelts - 1; i >= 0; i--)
    {
      svn_pool_clear(subpool);
      elt = &APR_ARRAY_IDX(params, i, svn_ra_svn_item_t);
      if (elt->kind != SVN_RA_SVN_LIST)
        return svn_error_create(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                                _("Malformed error list"));
      SVN_ERR(svn_ra_svn_parse_tuple(elt->u.list, subpool, "nccn", &apr_err,
                                      &message, &file, &line));
      /* The message field should have been optional, but we can't
         easily change that, so "" means a nonexistent message. */
      if (!*message)
        message = NULL;
      
      /* Skip over links in the error chain that were intended only to
         exist on the server (to wrap real errors intended for the
         client) but accidentally got included in the server's actual
         response. */
      if ((apr_status_t)apr_err != SVN_ERR_RA_SVN_CMD_ERR)
        {
          err = svn_error_create((apr_status_t)apr_err, err, message);
          err->file = apr_pstrdup(err->pool, file);
          err->line = (long)line;
        }
    }

  svn_pool_destroy(subpool);

  /* If we get here, then we failed to find a real error in the error
     chain that the server proported to be sending us.  That's bad. */
  if (! err)
    err = svn_error_create(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                           _("Malformed error list"));
    
  return err;
}

svn_error_t *svn_ra_svn_read_cmd_response(svn_ra_svn_conn_t *conn,
                                          apr_pool_t *pool,
                                          const char *fmt, ...)
{
  va_list ap;
  const char *status;
  apr_array_header_t *params;
  svn_error_t *err;

  SVN_ERR(svn_ra_svn_read_tuple(conn, pool, "wl", &status, &params));
  if (strcmp(status, "success") == 0)
    {
      va_start(ap, fmt);
      err = vparse_tuple(params, pool, &fmt, &ap);
      va_end(ap);
      return err;
    }
  else if (strcmp(status, "failure") == 0)
    {
      return svn_ra_svn__handle_failure_status(params, pool);
    }

  return svn_error_createf(SVN_ERR_RA_SVN_MALFORMED_DATA, NULL,
                           _("Unknown status '%s' in command response"),
                           status);
}

svn_error_t *svn_ra_svn_handle_commands2(svn_ra_svn_conn_t *conn,
                                         apr_pool_t *pool,
                                         const svn_ra_svn_cmd_entry_t *commands,
                                         void *baton,
                                         svn_boolean_t error_on_disconnect)
{
  apr_pool_t *subpool = svn_pool_create(pool);
  apr_pool_t *iterpool = svn_pool_create(subpool);
  const char *cmdname;
  const svn_ra_svn_cmd_entry_t *command;
  svn_error_t *err, *write_err;
  apr_array_header_t *params;
  apr_hash_t *cmd_hash = apr_hash_make(subpool);

  for (command = commands; command->cmdname; command++)
    apr_hash_set(cmd_hash, command->cmdname, APR_HASH_KEY_STRING, command);

  while (1)
    {
      svn_pool_clear(iterpool);
      err = svn_ra_svn_read_tuple(conn, iterpool, "wl", &cmdname, &params);
      if (err)
        {
          if (!error_on_disconnect
              && err->apr_err == SVN_ERR_RA_SVN_CONNECTION_CLOSED)
            {
              svn_error_clear(err);
              svn_pool_destroy(subpool);
              return SVN_NO_ERROR;
            }
          return err;
        }
      command = apr_hash_get(cmd_hash, cmdname, APR_HASH_KEY_STRING);

      if (command)
        err = (*command->handler)(conn, iterpool, params, baton);
      else
        {
          err = svn_error_createf(SVN_ERR_RA_SVN_UNKNOWN_CMD, NULL,
                                  _("Unknown command '%s'"), cmdname);
          err = svn_error_create(SVN_ERR_RA_SVN_CMD_ERR, err, NULL);
        }

      if (err && err->apr_err == SVN_ERR_RA_SVN_CMD_ERR)
        {
          write_err = svn_ra_svn_write_cmd_failure(
                          conn, iterpool,
                          svn_ra_svn__locate_real_error_child(err));
          svn_error_clear(err);
          if (write_err)
            return write_err;
        }
      else if (err)
        return err;

      if (command && command->terminate)
        break;
    }
  svn_pool_destroy(iterpool);
  svn_pool_destroy(subpool);
  return SVN_NO_ERROR;
}

svn_error_t *svn_ra_svn_handle_commands(svn_ra_svn_conn_t *conn,
                                        apr_pool_t *pool,
                                        const svn_ra_svn_cmd_entry_t *commands,
                                        void *baton)
{
  return svn_ra_svn_handle_commands2(conn, pool, commands, baton, TRUE);
}

svn_error_t *svn_ra_svn_write_cmd(svn_ra_svn_conn_t *conn, apr_pool_t *pool,
                                  const char *cmdname, const char *fmt, ...)
{
  va_list ap;
  svn_error_t *err;

  SVN_ERR(svn_ra_svn_start_list(conn, pool));
  SVN_ERR(svn_ra_svn_write_word(conn, pool, cmdname));
  va_start(ap, fmt);
  err = vwrite_tuple(conn, pool, fmt, ap);
  va_end(ap);
  if (err)
    return err;
  SVN_ERR(svn_ra_svn_end_list(conn, pool));
  return SVN_NO_ERROR;
}

svn_error_t *svn_ra_svn_write_cmd_response(svn_ra_svn_conn_t *conn,
                                           apr_pool_t *pool,
                                           const char *fmt, ...)
{
  va_list ap;
  svn_error_t *err;

  SVN_ERR(svn_ra_svn_start_list(conn, pool));
  SVN_ERR(svn_ra_svn_write_word(conn, pool, "success"));
  va_start(ap, fmt);
  err = vwrite_tuple(conn, pool, fmt, ap);
  va_end(ap);
  if (err)
    return err;
  SVN_ERR(svn_ra_svn_end_list(conn, pool));
  return SVN_NO_ERROR;
}

svn_error_t *svn_ra_svn_write_cmd_failure(svn_ra_svn_conn_t *conn,
                                          apr_pool_t *pool, svn_error_t *err)
{
  char buffer[128];
  SVN_ERR(svn_ra_svn_start_list(conn, pool));
  SVN_ERR(svn_ra_svn_write_word(conn, pool, "failure"));
  SVN_ERR(svn_ra_svn_start_list(conn, pool));
  for (; err; err = err->child)
    {
      const char *msg = err->message;

      if (msg == NULL)
        msg = svn_strerror(err->apr_err, buffer, sizeof(buffer));

      /* The message string should have been optional, but we can't
         easily change that, so marshal nonexistent messages as "". */
      SVN_ERR(svn_ra_svn_write_tuple(conn, pool, "nccn",
                                     (apr_uint64_t) err->apr_err,
                                     msg ? msg : "",
                                     err->file ? err->file : "",
                                     (apr_uint64_t) err->line));
    }
  SVN_ERR(svn_ra_svn_end_list(conn, pool));
  SVN_ERR(svn_ra_svn_end_list(conn, pool));
  return SVN_NO_ERROR;
}