---

svn_io.h

Go to the documentation of this file.

/**
 * @copyright
 * ====================================================================
 * Copyright (c) 2000-2004 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/.
 * ====================================================================
 * @endcopyright
 *
 * @file svn_io.h
 * @brief general Subversion I/O definitions
 */

/* ==================================================================== */


#ifndef SVN_IO_H
#define SVN_IO_H

#include <apr.h>
#include <apr_pools.h>
#include <apr_file_io.h>
#include <apr_thread_proc.h>

#include "svn_types.h"
#include "svn_error.h"
#include "svn_string.h"

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */



/** Determine the @a kind of @a path.
 *
 * If utf8-encoded @a path exists, set @a *kind to the appropriate kind,
 * else set it to @c svn_node_unknown. 
 *
 * If @a path is a file, @a *kind is set to @c svn_node_file.
 *
 * If @a path is a directory, @a *kind is set to @c svn_node_dir.
 *
 * If @a path does not exist in its final component, @a *kind is set to
 * @c svn_node_none.  
 *
 * If intermediate directories on the way to @a path don't exist, an
 * error is returned, and @a *kind's value is undefined.
 */
svn_error_t *svn_io_check_path (const char *path,
                                svn_node_kind_t *kind,
                                apr_pool_t *pool);

/**
 * @since New in 1.1.
 *
 * Like svn_io_check_path(), but also set *is_special to @c TRUE if
 * the path is not a normal file.
 */
svn_error_t *svn_io_check_special_path (const char *path,
                                        svn_node_kind_t *kind,
                                        svn_boolean_t *is_special,
                                        apr_pool_t *pool);

/** Like svn_io_check_path(), but resolve symlinks.  This returns the
    same varieties of @a kind as svn_io_check_path(). */ 
svn_error_t *svn_io_check_resolved_path (const char *path,
                                         svn_node_kind_t *kind,
                                         apr_pool_t *pool);


/** Open a new file (for writing) with a unique name based on utf-8
 * encoded @a path, in the same directory as @a path.  The file handle is
 * returned in @a *f, and the name, which ends with @a suffix, is returned
 * in @a *unique_name_p, also utf8-encoded.  If @a delete_on_close is set,
 * then the @c APR_DELONCLOSE flag will be used when opening the file. The
 * @c APR_BUFFERED flag will always be used.
 *
 * @a suffix may not be null.
 *
 * The first attempt will just append @a suffix.  If the result is not
 * a unique name, then subsequent attempts will append a dot,
 * followed by an iteration number ("2", then "3", and so on),
 * followed by the suffix.  For example, if @a path is
 *
 *    tests/t1/A/D/G/pi
 *
 * then successive calls to
 *
 *    @c svn_io_open_unique_file(&f, &unique_name, @a path, ".tmp", pool) 
 *
 * will open
 *
 *    tests/t1/A/D/G/pi.tmp
 *    tests/t1/A/D/G/pi.2.tmp
 *    tests/t1/A/D/G/pi.3.tmp
 *    tests/t1/A/D/G/pi.4.tmp
 *    tests/t1/A/D/G/pi.5.tmp
 *    ...
 *
 * @a *unique_name_p will never be exactly the same as @a path, even
 * if @a path does not exist.
 * 
 * It doesn't matter if @a path is a file or directory, the unique name will
 * be in @a path's parent either way.
 *
 * Allocate @a *f and @a *unique_name_p in @a pool.
 *
 * If no unique name can be found, @c SVN_ERR_IO_UNIQUE_NAMES_EXHAUSTED is
 * the error returned.
 *
 * Claim of Historical Inevitability: this function was written
 * because 
 *
 *    - @c tmpnam() is not thread-safe.
 *    - @c tempname() tries standard system tmp areas first.
 */
svn_error_t *svn_io_open_unique_file (apr_file_t **f,
                                      const char **unique_name_p,
                                      const char *path,
                                      const char *suffix,
                                      svn_boolean_t delete_on_close,
                                      apr_pool_t *pool);

/**
 * @since New in 1.1.
 *
 * Like svn_io_open_unique_file, except that instead of creating a
 * file, a symlink is generated that references the path @a dest.
 */
svn_error_t *svn_io_create_unique_link (const char **unique_name_p,
                                        const char *path,
                                        const char *dest,
                                        const char *suffix,
                                        apr_pool_t *pool);


/**
 * @since New in 1.1.
 *
 * Set @a dest to the path that the symlink at @a path references.
 * Allocate the string from @a pool.
 */
svn_error_t *svn_io_read_link (svn_string_t **dest,
                               const char *path,
                               apr_pool_t *pool);


/** Set @a dir to a directory path (allocated in @a pool) deemed
 * usable for the creation of temporary files and subdirectories.
 */
svn_error_t *svn_io_temp_dir (const char **dir,
                              apr_pool_t *pool);


/** Copy @a src to @a dst atomically.  Overwrite @a dst if it exists, else
 * create it.  Both @a src and @a dst are utf8-encoded filenames.  If
 * @a copy_perms is true, set @a dst's permissions to match those of @a src.
 */
svn_error_t *svn_io_copy_file (const char *src,
                               const char *dst,
                               svn_boolean_t copy_perms,
                               apr_pool_t *pool);

/** 
 * @since New in 1.1.
 *
 * Copy symbolic link @a src to @a dst atomically.  Overwrite @a dst
 * if it exists, else create it.  Both @a src and @a dst are
 * utf8-encoded filenames.  After copying, the @a dst link will point
 * to the same thing @a src does.
 */
svn_error_t *svn_io_copy_link (const char *src,
                               const char *dst,
                               apr_pool_t *pool);


/** Recursively copy directory @a src into @a dst_parent, as a new entry named
 * @a dst_basename.  If @a dst_basename already exists in @a dst_parent, 
 * return error.  @a copy_perms will be passed through to @c svn_io_copy_file 
 * when any files are copied.  @a src, @a dst_parent, and @a dst_basename are 
 * all utf8-encoded.
 *
 * If @a cancel_func is non-null, invoke it with @a cancel_baton at
 * various points during the operation.  If it returns any error
 * (typically @c SVN_ERR_CANCELLED), return that error immediately.
 */ 
svn_error_t *svn_io_copy_dir_recursively (const char *src,
                                          const char *dst_parent,
                                          const char *dst_basename,
                                          svn_boolean_t copy_perms,
                                          svn_cancel_func_t cancel_func,
                                          void *cancel_baton,
                                          apr_pool_t *pool);



/** Create directory @a path on the file system, creating intermediate
 * directories as required, like <tt>mkdir -p</tt>.  Report no error if @a 
 * path already exists.  @a path is utf8-encoded.
 *
 * This is essentially a wrapper for @c apr_dir_make_recursive(), passing
 * @c APR_OS_DEFAULT as the permissions.
 */
svn_error_t *svn_io_make_dir_recursively (const char *path, apr_pool_t *pool);


/** Set @a *is_empty_p to @c TRUE if directory @a path is empty, else to 
 * @c FALSE if it is not empty.  @a path must be a directory, and is
 * utf8-encoded.  Use @a pool for temporary allocation.
 */
svn_error_t *
svn_io_dir_empty (svn_boolean_t *is_empty_p,
                  const char *path,
                  apr_pool_t *pool);


/** Append @a src to @a dst.  @a dst will be appended to if it exists, else it
 * will be created.  Both @a src and @a dst are utf8-encoded.
 */
svn_error_t *svn_io_append_file (const char *src,
                                 const char *dst,
                                 apr_pool_t *pool);


/** Make a file as read-only as the operating system allows.
 * @a path is the utf8-encoded path to the file. If @a ignore_enoent is
 * @c TRUE, don't fail if the target file doesn't exist.
 */
svn_error_t *svn_io_set_file_read_only (const char *path,
                                        svn_boolean_t ignore_enoent,
                                        apr_pool_t *pool);


/** Make a file as writable as the operating system allows.
 * @a path is the utf8-encoded path to the file.  If @a ignore_enoent is
 * @c TRUE, don't fail if the target file doesn't exist.
 * @warning On Unix this function will do the equivlanet of chmod a+w path.
 * If this is not what you want you should not use this function, but rather
 * use apr_file_perms_set().
 */
svn_error_t *svn_io_set_file_read_write (const char *path,
                                         svn_boolean_t ignore_enoent,
                                         apr_pool_t *pool);

/** Toggle a file's "executability".
 *
 * When making the file executable on operating systems with unix style
 * permissions, never add an execute permission where there is not
 * already a read permission: that is, only make the file executable
 * for the user, group or world if the corresponding read permission
 * is already set for user, group or world.
 *
 * When making the file non-executable on operating systems with unix style
 * permissions, remove all execute permissions.
 *
 * On other operating systems, toggle the file's "executability" as much as
 * the operating system allows.
 *
 * @a path is the utf8-encoded path to the file.  If @a executable
 * is @c TRUE, then make the file executable.  If @c FALSE, make in
 * non-executable.  If @a ignore_enoent is @c TRUE, don't fail if the target
 * file doesn't exist.
 */
svn_error_t *svn_io_set_file_executable (const char *path,
                                         svn_boolean_t executable,
                                         svn_boolean_t ignore_enoent,
                                         apr_pool_t *pool);

/** Determine whether a file is executable by the current user.  
 * Set @a *executable to @c TRUE if the file @a path is executable by the 
 * current user, otherwise set it to @c FALSE.  
 * 
 * On Windows and on platforms without userids, always returns @c FALSE.
 */
svn_error_t *svn_io_is_file_executable(svn_boolean_t *executable, 
                                       const char *path, 
                                       apr_pool_t *pool);


/** Read a line from @a file into @a buf, but not exceeding @a *limit bytes.
 * Does not include newline, instead '\\0' is put there.
 * Length (as in strlen) is returned in @a *limit.
 * @a buf should be pre-allocated.
 * @a file should be already opened. 
 *
 * When the file is out of lines, @c APR_EOF will be returned.
 */
svn_error_t *
svn_io_read_length_line (apr_file_t *file, char *buf, apr_size_t *limit,
                         apr_pool_t *pool);


/** Set @a *apr_time to the time of last modification of the contents of the
 * file @a path.  @a path is utf8-encoded.
 *
 * Note: this is the APR mtime which corresponds to the traditional mtime
 * on Unix, and the last write time on Windows.
 */
svn_error_t *svn_io_file_affected_time (apr_time_t *apr_time,
                                        const char *path,
                                        apr_pool_t *pool);

/** Set the timestamp of file @a path to @a apr_time.  @a path is
 *  utf8-encoded.
 *
 * Note: this is the APR mtime which corresponds to the traditional mtime
 * on Unix, and the last write time on Windows.
 */
svn_error_t *svn_io_set_file_affected_time (apr_time_t apr_time,
                                            const char *path,
                                            apr_pool_t *pool);



/** Set @a *different_p to non-zero if @a file1 and @a file2 have different
 * sizes, else set to zero.  Both @a file1 and @a file2 are utf8-encoded.
 *
 * Setting @a *different_p to zero does not mean the files definitely
 * have the same size, it merely means that the sizes are not
 * definitely different.  That is, if the size of one or both files
 * cannot be determined, then the sizes are not known to be different,
 * so @a *different_p is set to 0.
 */
svn_error_t *svn_io_filesizes_different_p (svn_boolean_t *different_p,
                                           const char *file1,
                                           const char *file2,
                                           apr_pool_t *pool);


/** Put the md5 checksum of @a file into @a digest.
 * @a digest points to @c APR_MD5_DIGESTSIZE bytes of storage.
 * Use @a pool only for temporary allocations.
 */
svn_error_t *svn_io_file_checksum (unsigned char digest[],
                                   const char *file,
                                   apr_pool_t *pool);


/* Set @a *same to non-zero if @a file1 and @a file2 have the same
 * contents, else set it to zero.  Use @a pool for temporary allocations.
 */
svn_error_t *svn_io_files_contents_same_p (svn_boolean_t *same,
                                           const char *file1,
                                           const char *file2,
                                           apr_pool_t *pool);

/** Create file at @a file with contents @a contents.
 * will be created.  Path @a file is utf8-encoded.
 * Use @a pool for memory allocations.
 */
svn_error_t *svn_io_file_create (const char *file,
                                 const char *contents,
                                 apr_pool_t *pool);

/**
 * @deprecated Provided for backward compatibility with the 1.0.0 API.
 *
 * Lock file at @a lock_file. If @exclusive is TRUE,
 * obtain exclusive lock, otherwise obtain shared lock.
 * Lock will be automaticaly released when @a pool is cleared or destroyed.
 * Use @a pool for memory allocations.
 */
svn_error_t *svn_io_file_lock (const char *lock_file,
                               svn_boolean_t exclusive,
                               apr_pool_t *pool);

/**
 * @since New in 1.1.
 *
 * Lock file at @a lock_file. If @exclusive is TRUE,
 * obtain exclusive lock, otherwise obtain shared lock.
 *
 * If @a nonblocking is TRUE, do not wait for the lock if it
 * is not available: throw an error instead.
 *
 * Lock will be automaticaly released when @a pool is cleared or destroyed.
 * Use @a pool for memory allocations.
 */
svn_error_t *svn_io_file_lock2 (const char *lock_file,
                                svn_boolean_t exclusive,
                                svn_boolean_t nonblocking,
                                apr_pool_t *pool);
/**
 * @since New in 1.1.
 *
 * Flush any unwritten data from @a file to disk.  Use @a pool for
 *  memory allocations.
 */
svn_error_t *svn_io_file_flush_to_disk (apr_file_t *file,
                                        apr_pool_t *pool);

/** Copy file @a file from location @a src_path to location @a dest_path.
 * Use @a pool for memory allocations.
 */
svn_error_t *svn_io_dir_file_copy (const char *src_path, 
                                   const char *dest_path, 
                                   const char *file,
                                   apr_pool_t *pool);


/** Generic byte-streams
 *
 * @defgroup svn_io_byte_streams generic byte streams
 * @{
 */

/** An abstract stream of bytes--either incoming or outgoing or both.
 *
 * The creator of a stream sets functions to handle read and write.
 * Both of these handlers accept a baton whose value is determined at
 * stream creation time; this baton can point to a structure
 * containing data associated with the stream.  If a caller attempts
 * to invoke a handler which has not been set, it will generate a
 * runtime assertion failure.  The creator can also set a handler for
 * close requests so that it can flush buffered data or whatever;
 * if a close handler is not specified, a close request on the stream
 * will simply be ignored.  Note that svn_stream_close() does not
 * deallocate the memory used to allocate the stream structure; free
 * the pool you created the stream in to free that memory.
 *
 * The read and write handlers accept length arguments via pointer.
 * On entry to the handler, the pointed-to value should be the amount
 * of data which can be read or the amount of data to write.  When the
 * handler returns, the value is reset to the amount of data actually
 * read or written.  Handlers are obliged to complete a read or write
 * to the maximum extent possible; thus, a short read with no
 * associated error implies the end of the input stream, and a short
 * write should never occur without an associated error.
 */
typedef struct svn_stream_t svn_stream_t;



/** Read handler function for a generic stream.  */
typedef svn_error_t *(*svn_read_fn_t) (void *baton,
                                       char *buffer,
                                       apr_size_t *len);

/** Write handler function for a generic stream.  */
typedef svn_error_t *(*svn_write_fn_t) (void *baton,
                                        const char *data,
                                        apr_size_t *len);

/** Close handler function for a generic stream.  */
typedef svn_error_t *(*svn_close_fn_t) (void *baton);


/** Creating a generic stream.  */
svn_stream_t *svn_stream_create (void *baton, apr_pool_t *pool);

/** Set @a stream's baton to @a baton */
void svn_stream_set_baton (svn_stream_t *stream, void *baton);

/** Set @a stream's read function to @a read_fn */
void svn_stream_set_read (svn_stream_t *stream, svn_read_fn_t read_fn);

/** Set @a stream's write function to @a write_fn */
void svn_stream_set_write (svn_stream_t *stream, svn_write_fn_t write_fn);

/** Set @a stream's close function to @a close_fn */
void svn_stream_set_close (svn_stream_t *stream, svn_close_fn_t close_fn);


/** Convenience function to create a generic stream which is empty.  */
svn_stream_t *svn_stream_empty (apr_pool_t *pool);


/** Convenience function for creating streams which operate on APR
 * files.  For convenience, if @a file is NULL then @c svn_stream_empty(pool) 
 * is returned.  Note that the stream returned by these operations is not 
 * considered to "own" the underlying file, meaning that @c svn_stream_close() 
 * on the stream will not close the file.
 */
svn_stream_t *svn_stream_from_aprfile (apr_file_t *file, apr_pool_t *pool);

/** Set @a *out to a generic stream connected to stdout, allocated in 
 * @a pool.  The stream and its underlying APR handle will be closed
 * when @a pool is cleared or destroyed.
 */
svn_error_t *svn_stream_for_stdout (svn_stream_t **out, apr_pool_t *pool);

/** Return a generic stream connected to stringbuf @a str.  Allocate the
 * stream in @a pool.
 */
svn_stream_t *svn_stream_from_stringbuf (svn_stringbuf_t *str,
                                         apr_pool_t *pool);

/** Return a stream that decompresses all data read and compresses all
 * data written. The stream @a stream is used to read and write all
 * compressed data. All compression data structures are allocated on
 * @a pool. If compression support is not compiled in then @c
 * svn_stream_compressed() returns @a stream unmodified. Make sure you
 * call @c svn_stream_close() on the stream returned by this function,
 * so that all data are flushed and cleaned up.
 */
svn_stream_t *svn_stream_compressed (svn_stream_t *stream, 
                                     apr_pool_t *pool);

/** Read from a generic stream. */
svn_error_t *svn_stream_read (svn_stream_t *stream, char *buffer,
                              apr_size_t *len);

/** Write to a generic stream. */
svn_error_t *svn_stream_write (svn_stream_t *stream, const char *data,
                               apr_size_t *len);

/** Close a generic stream. */
svn_error_t *svn_stream_close (svn_stream_t *stream);


/** Write to @a stream using a printf-style @a fmt specifier, passed through
 * @c apr_psprintf using memory from @a pool.
 */
svn_error_t *svn_stream_printf (svn_stream_t *stream,
                                apr_pool_t *pool,
                                const char *fmt,
                                ...)
       __attribute__ ((format(printf, 3, 4)));

/** Allocate @a *stringbuf in @a pool, and read into it one line (terminated
 * by @a eol) from @a stream. The line-terminator is read from the stream,
 * but is not added to the end of the stringbuf.  Instead, the stringbuf
 * ends with a usual '\\0'.
 *
 * If @a stream runs out of bytes before encountering a line-terminator,
 * then set @a *eof to @c TRUE, otherwise set @a *eof to FALSE.
 */
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);

/**
 * @since New in 1.1.
 *
 * Read the contents of the readable stream @a from and write them to the
 * writable stream @a to.
 */
svn_error_t *svn_stream_copy (svn_stream_t *from, svn_stream_t *to,
                              apr_pool_t *pool);

/** @} */

/** Sets @a *result to a string containing the contents of @a filename, a
 * utf8-encoded path. 
 *
 * If @a filename is "-", return the error @c SVN_ERR_UNSUPPORTED_FEATURE
 * and don't touch @a *result.
 *
 * ### Someday, "-" will fill @a *result from stdin.  The problem right
 * now is that if the same command invokes the editor, stdin is crap,
 * and the editor acts funny or dies outright.  One solution is to
 * disallow stdin reading and invoking the editor, but how to do that
 * reliably?
 */
svn_error_t *svn_stringbuf_from_file (svn_stringbuf_t **result, 
                                      const char *filename, 
                                      apr_pool_t *pool);

/** Sets @a *result to a string containing the contents of the already opened
 * @a file.  Reads from the current position in file to the end.  Does not
 * close the file or reset the cursor position.
 */
svn_error_t *svn_stringbuf_from_aprfile (svn_stringbuf_t **result,
                                         apr_file_t *file,
                                         apr_pool_t *pool);

/** Remove file @a path, a utf8-encoded path.  This wraps @c apr_file_remove(), 
 * converting any error to a Subversion error.
 */
svn_error_t *svn_io_remove_file (const char *path, apr_pool_t *pool);

/** Recursively remove directory @a path.  @a path is utf8-encoded. */
svn_error_t *svn_io_remove_dir (const char *path, apr_pool_t *pool);


/** Read all of the disk entries in directory @a path, a utf8-encoded
 * path.  Return a @a dirents hash mapping dirent names (<tt>char *</tt>) to
 * enumerated dirent filetypes (@c svn_node_kind_t *).
 *
 * Note:  the `.' and `..' directories normally returned by
 * @c apr_dir_read are NOT returned in the hash.
 */
svn_error_t *svn_io_get_dirents (apr_hash_t **dirents,
                                 const char *path,
                                 apr_pool_t *pool);


/** Callback function type for @c svn_io_dir_walk  */
typedef svn_error_t * (*svn_io_walk_func_t) (void *baton,
                                             const char *path,
                                             const apr_finfo_t *finfo,
                                             apr_pool_t *pool);

/** This function will recursively walk over the files and directories
 * rooted at @a dirname, a utf8-encoded path. For each file or directory,
 * @a walk_func is invoked, passing in the @a walk_baton, the utf8-encoded
 * full path to the entry, an @c apr_finfo_t structure, and a temporary
 * pool for allocations.  For any directory, @a walk_func will be invoked
 * on the directory itself before being invoked on any subdirectories or
 * files within the directory.
 *
 * The set of information passed to @a walk_func is specified by @a wanted,
 * and the items specified by @c APR_FINFO_TYPE and @c APR_FINFO_NAME.
 *
 * All allocations will be performed in @a pool.
 */
svn_error_t *svn_io_dir_walk (const char *dirname,
                              apr_int32_t wanted,
                              svn_io_walk_func_t walk_func,
                              void *walk_baton,
                              apr_pool_t *pool);

/** Invoke @a cmd with @a args, using utf8-encoded @a path as working 
 * directory.  Connect @a cmd's stdin, stdout, and stderr to @a infile, 
 * @a outfile, and @a errfile, except where they are null.
 *
 * If set, @a exitcode will contain the exit code of the process upon return,
 * and @a exitwhy will indicate why the process terminated. If @a exitwhy is 
 * not set and the exit reason is not @c APR_PROC_CHECK_EXIT(), or if 
 * @a exitcode is not set and the exit code is non-zero, then an 
 * @c SVN_ERR_EXTERNAL_PROGRAM error will be returned.
 *
 * @a args is a list of utf8-encoded (<tt>const char *</tt>)'s, terminated by
 * @c NULL.  @c ARGS[0] is the name of the program, though it need not be
 * the same as @a cmd.
 *
 * @a inherit sets whether the invoked program shall inherit its environment or
 * run "clean".
 */
svn_error_t *svn_io_run_cmd (const char *path,
                             const char *cmd,
                             const char *const *args,
                             int *exitcode,
                             apr_exit_why_e *exitwhy,
                             svn_boolean_t inherit,
                             apr_file_t *infile,
                             apr_file_t *outfile,
                             apr_file_t *errfile,
                             apr_pool_t *pool);

/** Invoke @c the configured diff program, with @a user_args (an array
 * of utf8-encoded @a num_user_args arguments), if they are specified,
 * or "-u" if they are not.
 *
 * Diff runs in utf8-encoded @a dir, and its exit status is stored in
 * @a exitcode, if it is not @c NULL.  
 *
 * If @a label1 and/or @a label2 are not null they will be passed to the diff
 * process as the arguments of "-L" options.  @a label1 and @a label2 are also 
 * in utf8, and will be converted to native charset along with the other args.
 *
 * @a from is the first file passed to diff, and @a to is the second.  The
 * stdout of diff will be sent to @a outfile, and the stderr to @a errfile.
 *
 * @a diff_cmd must be non-null.
 *
 * Do all allocation in @a pool. 
 */
svn_error_t *svn_io_run_diff (const char *dir,
                              const char *const *user_args,
                              int num_user_args,
                              const char *label1,
                              const char *label2,
                              const char *from,
                              const char *to,
                              int *exitcode,
                              apr_file_t *outfile,
                              apr_file_t *errfile,
                              const char *diff_cmd,
                              apr_pool_t *pool);


/** Invoke @c the configured diff3 program, in utf8-encoded @a dir
 * like this:
 *
 *          diff3 -Em @a mine @a older @a yours > @a merged
 *
 * (See the diff3 documentation for details.)
 *
 * @a mine, @a older, and @a yours are utf8-encoded paths, relative to @a dir, 
 * to three files that already exist.  @a merged is an open file handle, and
 * is left open after the merge result is written to it. (@a merged
 * should *not* be the same file as @a mine, or nondeterministic things
 * may happen!)
 *
 * @a mine_label, @a older_label, @a yours_label are utf8-encoded label
 * parameters for diff3's -L option.  Any of them may be @c NULL, in
 * which case the corresponding @a mine, @a older, or @a yours parameter is
 * used instead.
 *
 * Set @a *exitcode to diff3's exit status.  If @a *exitcode is anything
 * other than 0 or 1, then return @c SVN_ERR_EXTERNAL_PROGRAM.  (Note the
 * following from the diff3 info pages: "An exit status of 0 means
 * `diff3' was successful, 1 means some conflicts were found, and 2
 * means trouble.") 
 *
 * @a diff3_cmd must be non-null.
 *
 * Do all allocation in @a pool. 
 */
svn_error_t *svn_io_run_diff3 (const char *dir,
                               const char *mine,
                               const char *older,
                               const char *yours,
                               const char *mine_label,
                               const char *older_label,
                               const char *yours_label,
                               apr_file_t *merged,
                               int *exitcode,
                               const char *diff3_cmd,
                               apr_pool_t *pool);


/** Examine utf8-encoded @a file to determine if it can be described by a
 * known (as in, known by this function) Multipurpose Internet Mail
 * Extension (MIME) type.  If so, set @a mimetype to a character string
 * describing the MIME type, else set it to @c NULL.  Use @a pool for any
 * necessary allocations.
 */
svn_error_t *svn_io_detect_mimetype (const char **mimetype,
                                     const char *file,
                                     apr_pool_t *pool);
                                      

/** Wrapper for @c apr_file_open(), which see.  @a fname is utf8-encoded. */
svn_error_t *
svn_io_file_open (apr_file_t **new_file, const char *fname,
                  apr_int32_t flag, apr_fileperms_t perm,
                  apr_pool_t *pool);


/** Wrapper for @c apr_file_close(), which see. */
svn_error_t *
svn_io_file_close (apr_file_t *file, apr_pool_t *pool);


/** Wrapper for @c apr_file_getc(), which see. */
svn_error_t *
svn_io_file_getc (char *ch, apr_file_t *file, apr_pool_t *pool);


/** Wrapper for @c apr_file_info_get(), which see. */
svn_error_t *
svn_io_file_info_get (apr_finfo_t *finfo, apr_int32_t wanted, 
                      apr_file_t *file, apr_pool_t *pool);


/** Wrapper for @c apr_file_read(), which see. */
svn_error_t *
svn_io_file_read (apr_file_t *file, void *buf, 
                  apr_size_t *nbytes, apr_pool_t *pool);


/** Wrapper for @c apr_file_read_full(), which see. */
svn_error_t *
svn_io_file_read_full (apr_file_t *file, void *buf, 
                       apr_size_t nbytes, apr_size_t *bytes_read,
                       apr_pool_t *pool);


/** Wrapper for @c apr_file_seek(), which see. */
svn_error_t *
svn_io_file_seek (apr_file_t *file, apr_seek_where_t where, 
                  apr_off_t *offset, apr_pool_t *pool);


/** Wrapper for @c apr_file_write(), which see. */
svn_error_t *
svn_io_file_write (apr_file_t *file, const void *buf, 
                   apr_size_t *nbytes, apr_pool_t *pool);


/** Wrapper for @c apr_file_write_full(), which see. */
svn_error_t *
svn_io_file_write_full (apr_file_t *file, const void *buf, 
                        apr_size_t nbytes, apr_size_t *bytes_written,
                        apr_pool_t *pool);


/** Wrapper for @c apr_stat(), which see.  @a fname is utf8-encoded. */
svn_error_t *
svn_io_stat (apr_finfo_t *finfo, const char *fname,
             apr_int32_t wanted, apr_pool_t *pool);


/** Wrapper for @c apr_file_rename(), which see.  @a from_path and @a to_path
 * are utf8-encoded.
 */
svn_error_t *
svn_io_file_rename (const char *from_path, const char *to_path,
                    apr_pool_t *pool);


/** Wrapper for @c apr_dir_make(), which see.  @a path is utf8-encoded. */
svn_error_t *
svn_io_dir_make (const char *path, apr_fileperms_t perm, apr_pool_t *pool);

/** Same as svn_io_dir_make, but sets the hidden attribute on the
    directory on systems that support it. */
svn_error_t *
svn_io_dir_make_hidden (const char *path, apr_fileperms_t perm,
                        apr_pool_t *pool);

/**
 * @since New in 1.1.
 *
 * Same as svn_io_dir_make, but attempts to set the sgid on the
 * directory on systems that support it.  Does not return an error if
 * the attempt to set the sgid bit fails.  On Unix filesystems,
 * setting the sgid bit on a directory ensures that files and
 * subdirectories created within inherit group ownership from the
 * parent instead of from the primary gid. */
svn_error_t *
svn_io_dir_make_sgid (const char *path, apr_fileperms_t perm,
                      apr_pool_t *pool);

/** Wrapper for @c apr_dir_open(), which see.  @a dirname is utf8-encoded. */
svn_error_t *
svn_io_dir_open (apr_dir_t **new_dir, const char *dirname, apr_pool_t *pool);


/** Wrapper for @c apr_dir_remove(), which see.  @a dirname is utf8-encoded.
 * Note: this function has this name to avoid confusion with
 * @c svn_io_remove_dir, which is recursive.
 */
svn_error_t *
svn_io_dir_remove_nonrecursive (const char *dirname, apr_pool_t *pool);


/** Wrapper for @c apr_dir_read, which see.  Ensures that @a finfo->name is
 * utf8-encoded, which means allocating @a finfo->name in @a pool, which may
 * or may not be the same as @a finfo's pool.  Use @a pool for error allocation
 * as well.
 */
svn_error_t *
svn_io_dir_read (apr_finfo_t *finfo,
                 apr_int32_t wanted,
                 apr_dir_t *thedir,
                 apr_pool_t *pool);



/** Version/format files. 
 *
 * @defgroup svn_io_format_files version/format files
 * @{
 */

/** Set @a *version to the integer that starts the file at @a path.  If the
 * file does not begin with a series of digits followed by a newline,
 * return the error @c SVN_ERR_BAD_VERSION_FILE_FORMAT.  Use @a pool for
 * all allocations.
 */
svn_error_t *
svn_io_read_version_file (int *version, const char *path, apr_pool_t *pool);

/** Create (or overwrite) the file at @a path with new contents,
 * formatted as a non-negative integer @a version followed by a single
 * newline.  On successful completion the file will be read-only.  Use
 * @a pool for all allocations.
 */
svn_error_t *
svn_io_write_version_file (const char *path, int version, apr_pool_t *pool);

/** @} */

#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif /* SVN_IO_H */

---