Function svn_hash_diff 

pub unsafe extern "C" fn svn_hash_diff(
    hash_a: *mut apr_hash_t,
    hash_b: *mut apr_hash_t,
    diff_func: svn_hash_diff_func_t,
    diff_func_baton: *mut c_void,
    pool: *mut apr_pool_t,
) -> *mut svn_error_t

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.