base/strings/string_split.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_STRINGS_STRING_SPLIT_H_
#define BASE_STRINGS_STRING_SPLIT_H_

#include <optional>
#include <string>
#include <string_view>
#include <utility>
#include <vector>

#include "base/base_export.h"
#include "base/compiler_specific.h"
#include "build/build_config.h"

namespace base {

// Splits a string at the first instance of `separator`, returning a pair of
// `std::string_view`: `first` is the (potentially empty) part that comes before
// the separator, and `second` is the (potentially empty) part that comes after.
// If `separator` is not in `input`, returns `std::nullopt`.
BASE_EXPORT std::optional<std::pair<std::string_view, std::string_view>>
SplitStringOnce(std::string_view input LIFETIME_BOUND, char separator);

// Similar to the above, but splits the string at the first instance of any
// separator in `separators`.
BASE_EXPORT std::optional<std::pair<std::string_view, std::string_view>>
SplitStringOnce(std::string_view input LIFETIME_BOUND,
                std::string_view separators);

// Splits a string at the last instance of `separator`, returning a pair of
// `std::string_view`: `first` is the (potentially empty) part that comes before
// the separator, and `second` is the (potentially empty) part that comes after.
// If `separator` is not in `input`, returns `std::nullopt`.
BASE_EXPORT std::optional<std::pair<std::string_view, std::string_view>>
RSplitStringOnce(std::string_view input LIFETIME_BOUND, char separator);

// Similar to the above, but splits the string at the last instance of any
// separator in `separators`.
BASE_EXPORT std::optional<std::pair<std::string_view, std::string_view>>
RSplitStringOnce(std::string_view input LIFETIME_BOUND,
                 std::string_view separators);

enum WhitespaceHandling {
  KEEP_WHITESPACE,
  TRIM_WHITESPACE,
};

enum SplitResult {
  // Strictly return all results.
  //
  // If the input is ",," and the separator is ',' this will return a
  // vector of three empty strings.
  SPLIT_WANT_ALL,

  // Only nonempty results will be added to the results. Multiple separators
  // will be coalesced. Separators at the beginning and end of the input will
  // be ignored. With TRIM_WHITESPACE, whitespace-only results will be dropped.
  //
  // If the input is ",," and the separator is ',', this will return an empty
  // vector.
  SPLIT_WANT_NONEMPTY,
};

}  // namespace base

// This file is only included after here so it can have visibility at
// compile-time of the enums defined above.
#include "base/strings/string_split_internal.h"

namespace base {

// Split the given string on ANY of the given separators, returning copies of
// the result.
//
// Note this is inverse of JoinString() defined in string_util.h.
//
// To split on either commas or semicolons, keeping all whitespace:
//
//   std::vector<std::string> tokens = base::SplitString(
//       input, ",;", base::KEEP_WHITESPACE, base::SPLIT_WANT_ALL);
[[nodiscard]] BASE_EXPORT constexpr std::vector<std::string> SplitString(
    std::string_view input,
    std::string_view separators,
    WhitespaceHandling whitespace,
    SplitResult result_type) {
  return internal::SplitStringT<std::string>(input, separators, whitespace,
                                             result_type);
}

[[nodiscard]] BASE_EXPORT constexpr std::vector<std::u16string> SplitString(
    std::u16string_view input,
    std::u16string_view separators,
    WhitespaceHandling whitespace,
    SplitResult result_type) {
  return internal::SplitStringT<std::u16string>(input, separators, whitespace,
                                                result_type);
}

// Like SplitString above except it returns a vector of std::string_views which
// reference the original buffer without copying. Although you have to be
// careful to keep the original string unmodified, this provides an efficient
// way to iterate through tokens in a string.
//
// Note this is inverse of JoinString() defined in string_util.h.
//
// To iterate through all whitespace-separated tokens in an input string:
//
//   for (const auto& cur :
//        base::SplitStringPiece(input, base::kWhitespaceASCII,
//                               base::KEEP_WHITESPACE,
//                               base::SPLIT_WANT_NONEMPTY)) {
//     ...
//   }
[[nodiscard]] BASE_EXPORT constexpr std::vector<std::string_view>
SplitStringPiece(std::string_view input LIFETIME_BOUND,
                 std::string_view separators,
                 WhitespaceHandling whitespace,
                 SplitResult result_type) {
  return internal::SplitStringT<std::string_view>(input, separators, whitespace,
                                                  result_type);
}

[[nodiscard]] BASE_EXPORT constexpr std::vector<std::u16string_view>
SplitStringPiece(std::u16string_view input LIFETIME_BOUND,
                 std::u16string_view separators,
                 WhitespaceHandling whitespace,
                 SplitResult result_type) {
  return internal::SplitStringT<std::u16string_view>(input, separators,
                                                     whitespace, result_type);
}

using StringPairs = std::vector<std::pair<std::string, std::string>>;
using StringViewPairs =
    std::vector<std::pair<std::string_view, std::string_view>>;

// Splits |line| into key value pairs according to the given delimiters and
// removes whitespace leading each key and trailing each value. Returns true
// only if each pair has a non-empty key and value. |key_value_pairs| will
// include ("","") pairs for entries without |key_value_delimiter|.
BASE_EXPORT bool SplitStringIntoKeyValuePairs(std::string_view input,
                                              char key_value_delimiter,
                                              char key_value_pair_delimiter,
                                              StringPairs* key_value_pairs);

// Like SplitStringIntoKeyValuePairs above except it uses a vector of
// std::string_views which reference the original buffer without copying.
BASE_EXPORT bool SplitStringIntoKeyValueViewPairs(
    std::string_view input,
    char key_value_delimiter,
    char key_value_pair_delimiter,
    StringViewPairs* key_value_pairs);

// Similar to SplitStringIntoKeyValuePairs, but use a substring
// |key_value_pair_delimiter| instead of a single char.
BASE_EXPORT bool SplitStringIntoKeyValuePairsUsingSubstr(
    std::string_view input,
    char key_value_delimiter,
    std::string_view key_value_pair_delimiter,
    StringPairs* key_value_pairs);

// Like SplitStringIntoKeyValuePairsUsingSubstr above except it uses a vector of
// std::string_views which reference the original buffer without copying.
BASE_EXPORT bool SplitStringIntoKeyValueViewPairsUsingSubstr(
    std::string_view input,
    char key_value_delimiter,
    std::string_view key_value_pair_delimiter,
    StringViewPairs* key_value_pairs);

// Similar to SplitString, but use a substring delimiter instead of a list of
// characters that are all possible delimiters.
[[nodiscard]] BASE_EXPORT constexpr std::vector<std::u16string>
SplitStringUsingSubstr(std::u16string_view input,
                       std::u16string_view delimiter,
                       WhitespaceHandling whitespace,
                       SplitResult result_type) {
  return internal::SplitStringUsingSubstrT<std::u16string>(
      input, delimiter, whitespace, result_type);
}

[[nodiscard]] BASE_EXPORT constexpr std::vector<std::string>
SplitStringUsingSubstr(std::string_view input,
                       std::string_view delimiter,
                       WhitespaceHandling whitespace,
                       SplitResult result_type) {
  return internal::SplitStringUsingSubstrT<std::string>(
      input, delimiter, whitespace, result_type);
}

// Like SplitStringUsingSubstr above except it returns a vector of StringPieces
// which reference the original buffer without copying. Although you have to be
// careful to keep the original string unmodified, this provides an efficient
// way to iterate through tokens in a string.
//
// To iterate through all newline-separated tokens in an input string:
//
//   for (std::string_view token :
//        base::SplitStringUsingSubstr(input, "\r\n",
//                                     base::KEEP_WHITESPACE,
//                                     base::SPLIT_WANT_NONEMPTY)) {
//     ...
[[nodiscard]] BASE_EXPORT constexpr std::vector<std::u16string_view>
SplitStringPieceUsingSubstr(std::u16string_view input LIFETIME_BOUND,
                            std::u16string_view delimiter,
                            WhitespaceHandling whitespace,
                            SplitResult result_type) {
  return internal::SplitStringUsingSubstrT<std::u16string_view>(
      input, delimiter, whitespace, result_type);
}

[[nodiscard]] BASE_EXPORT constexpr std::vector<std::string_view>
SplitStringPieceUsingSubstr(std::string_view input LIFETIME_BOUND,
                            std::string_view delimiter,
                            WhitespaceHandling whitespace,
                            SplitResult result_type) {
  return internal::SplitStringUsingSubstrT<std::string_view>(
      input, delimiter, whitespace, result_type);
}

}  // namespace base

#if BUILDFLAG(IS_WIN)
#include "base/strings/string_split_win.h"
#endif

#endif  // BASE_STRINGS_STRING_SPLIT_H_