svn_hash.h

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/**
 * @copyright
 * ====================================================================
 * Copyright (c) 2000-2004, 2008 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_hash.h
 * @brief Dumping and reading hash tables to/from files.
 */


#ifndef SVN_HASH_H
#define SVN_HASH_H

#include <apr.h>
#include <apr_pools.h>
#include <apr_hash.h>
#include <apr_tables.h>
#include <apr_file_io.h>  /* for apr_file_t */

#include "svn_types.h"
#include "svn_io.h"       /* for svn_stream_t */


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


/** The longest the "K <number>" line can be in one of our hashdump files. */
#define SVN_KEYLINE_MAXLEN 100

/**
 * @defgroup svn_hash_support Hash table serialization support
 * @{
 */

/*----------------------------------------------------*/

/** Reading/writing hashtables to disk
 *
 * @defgroup svn_hash_read_write Reading and writing hashtables to disk
 * @{
 */

/**
 * The conventional terminator for hash dumps.
 *
 * @since New in 1.1.
 */
#define SVN_HASH_TERMINATOR "END"

/**
 * Read a hash table from @a stream, storing the resultants names and
 * values in @a hash.  Use a @a pool for all allocations.  @a hash will
 * have <tt>const char *</tt> keys and <tt>svn_string_t *</tt> values.
 * If @a terminator is NULL, expect the hash to be terminated by the
 * end of the stream; otherwise, expect the hash to be terminated by a
 * line containing @a terminator.  Pass @c SVN_HASH_TERMINATOR to use
 * the conventional terminator "END".
 *
 * @since New in 1.1.
 */
svn_error_t *
svn_hash_read2(apr_hash_t *hash,
               svn_stream_t *stream,
               const char *terminator,
               apr_pool_t *pool);

/**
 * Dump @a hash to @a stream.  Use @a pool for all allocations.  @a
 * hash has <tt>const char *</tt> keys and <tt>svn_string_t *</tt>
 * values.  If @a terminator is not NULL, terminate the hash with a
 * line containing @a terminator.
 *
 * @since New in 1.1.
 */
svn_error_t *
svn_hash_write2(apr_hash_t *hash,
                svn_stream_t *stream,
                const char *terminator,
                apr_pool_t *pool);

/**
 * Similar to svn_hash_read2(), but allows @a stream to contain
 * deletion lines which remove entries from @a hash as well as adding
 * to it.
 *
 * @since New in 1.1.
 */
svn_error_t *
svn_hash_read_incremental(apr_hash_t *hash,
                          svn_stream_t *stream,
                          const char *terminator,
                          apr_pool_t *pool);

/**
 * Similar to svn_hash_write2(), but only writes out entries for
 * keys which differ between @a hash and @a oldhash, and also writes
 * out deletion lines for keys which are present in @a oldhash but not
 * in @a hash.
 *
 * @since New in 1.1.
 */
svn_error_t *
svn_hash_write_incremental(apr_hash_t *hash,
                           apr_hash_t *oldhash,
                           svn_stream_t *stream,
                           const char *terminator,
                           apr_pool_t *pool);

/**
 * This function behaves like svn_hash_read2(), but it only works
 * on an apr_file_t input, empty files are accepted, and the hash is
 * expected to be terminated with a line containing "END" or
 * "PROPS-END".
 *
 * @deprecated Provided for backward compatibility with the 1.0 API.
 */
SVN_DEPRECATED
svn_error_t *
svn_hash_read(apr_hash_t *hash,
              apr_file_t *srcfile,
              apr_pool_t *pool);

/**
 * This function behaves like svn_hash_write2(), but it only works
 * on an apr_file_t output, and the terminator is always "END".
 *
 * @deprecated Provided for backward compatibility with the 1.0 API.
 */
SVN_DEPRECATED
svn_error_t *
svn_hash_write(apr_hash_t *hash,
               apr_file_t *destfile,
               apr_pool_t *pool);

/** @} */


/** Taking the "diff" of two hash tables.
 *
 * @defgroup svn_hash_diff Taking the diff of two hash tables.
 * @{
 */

/** Hash key status indicator for svn_hash_diff_func_t.  */
enum svn_hash_diff_key_status
  {
    /* Key is present in both hashes. */
    svn_hash_diff_key_both,

    /* Key is present in first hash only. */
    svn_hash_diff_key_a,

    /* Key is present in second hash only. */
    svn_hash_diff_key_b
  };


/** Function type for expressing a key's status between two hash tables. */
typedef svn_error_t *(*svn_hash_diff_func_t)
  (const void *key, apr_ssize_t klen,
   enum svn_hash_diff_key_status status,
   void *baton);


/** Take the diff of two hashtables.
 *
 * For each key in the union of @a hash_a's and @a hash_b's keys, invoke
 * @a diff_func exactly once, passing the key, the key's length, an enum
 * @c svn_hash_diff_key_status indicating which table(s) the key appears
 * in, and @a diff_func_baton.
 *
 * Process all keys of @a hash_a first, then all remaining keys of @a hash_b.
 *
 * If @a diff_func returns error, return that error immediately, without
 * applying @a diff_func to anything else.
 *
 * @a hash_a or @a hash_b or both may be NULL; treat a null table as though
 * empty.
 *
 * Use @a pool for temporary allocation.
 */
svn_error_t *
svn_hash_diff(apr_hash_t *hash_a,
              apr_hash_t *hash_b,
              svn_hash_diff_func_t diff_func,
              void *diff_func_baton,
              apr_pool_t *pool);

/** @} */


/**
 * @defgroup svn_hash_misc Miscellaneous hash APIs
 * @{
 */

/**
 * Return the keys to @a hash in @a *array.  The keys are assumed to be
 * (const char *).  The keys are in no particular order.
 *
 * @a *array itself is allocated in @a pool; however, the keys are not
 * copied from the hash.
 *
 * @since New in 1.5.
 */
svn_error_t *
svn_hash_keys(apr_array_header_t **array,
              apr_hash_t *hash,
              apr_pool_t *pool);

/**
 * Set @a *hash to a new hash whose keys come from the items in @a keys
 * (an array of <tt>const char *</tt> items), and whose values are
 * match their corresponding key.  Use @a pool for all allocations
 * (including @a *hash, its keys, and its values).
 *
 * @since New in 1.5.
 */
svn_error_t *
svn_hash_from_cstring_keys(apr_hash_t **hash,
                           const apr_array_header_t *keys,
                           apr_pool_t *pool);

/**
 * Clear any key/value pairs in the hash table.  A wrapper for a
 * apr_hash_clear(), which isn't available until APR 1.3.0.
 *
 * @since New in 1.5.
 */
svn_error_t *
svn_hash__clear(apr_hash_t *hash);

/** @} */

/** @} */

#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif /* SVN_HASH_H */