firebase-ios-sdk/Firestore/Port/string_util.h

/*
 * Copyright 2017 Google
 *
 * Licensed 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.
 */

// Useful string functions and so forth.  This is a grab-bag file.
//
// These functions work fine for UTF-8 strings as long as you can
// consider them to be just byte strings.  For example, due to the
// design of UTF-8 you do not need to worry about accidental matches,
// as long as all your inputs are valid UTF-8 (use \uHHHH, not \xHH or \oOOO).

#ifndef IPHONE_FIRESTORE_PORT_STRING_UTIL_H_
#define IPHONE_FIRESTORE_PORT_STRING_UTIL_H_

#include <string>

namespace leveldb {
class Slice;
}

namespace Firestore {

// Returns the smallest lexicographically larger string of equal or smaller
// length. Returns an empty string if there is no such successor (if the input
// is empty or consists entirely of 0xff bytes).
// Useful for calculating the smallest lexicographically larger string
// that will not be prefixed by the input string.
//
// Examples:
// "a" -> "b", "aaa" -> "aab", "aa\xff" -> "ab", "\xff" -> "", "" -> ""
std::string PrefixSuccessor(leveldb::Slice prefix);

// Returns the immediate lexicographically-following string. This is useful to
// turn an inclusive range into something that can be used with Bigtable's
// SetLimitRow():
//
//     // Inclusive range [min_element, max_element].
//     string min_element = ...;
//     string max_element = ...;
//
//     // Equivalent range [range_start, range_end).
//     string range_start = min_element;
//     string range_end = ImmediateSuccessor(max_element);
//
// WARNING: Returns the input string with a '\0' appended; if you call c_str()
// on the result, it will compare equal to s.
//
// WARNING: Transforms "" -> "\0"; this doesn't account for Bigtable's special
// treatment of "" as infinity.
std::string ImmediateSuccessor(leveldb::Slice s);

}  // namespace Firestore

#endif  // IPHONE_FIRESTORE_PORT_STRING_UTIL_H_