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- // Copyright (c) 2012 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- //
- // A string-like object that points to a sized piece of memory.
- //
- // You can use StringPiece as a function or method parameter. A StringPiece
- // parameter can receive a double-quoted string literal argument, a "const
- // char*" argument, a string argument, or a StringPiece argument with no data
- // copying. Systematic use of StringPiece for arguments reduces data
- // copies and strlen() calls.
- //
- // Prefer passing StringPieces by value:
- // void MyFunction(StringPiece arg);
- // If circumstances require, you may also pass by const reference:
- // void MyFunction(const StringPiece& arg); // not preferred
- // Both of these have the same lifetime semantics. Passing by value
- // generates slightly smaller code. For more discussion, Googlers can see
- // the thread go/stringpiecebyvalue on c-users.
- #ifndef BASE_STRINGS_STRING_PIECE_H_
- #define BASE_STRINGS_STRING_PIECE_H_
- #include <stddef.h>
- #include <algorithm>
- #include <iosfwd>
- #include <limits>
- #include <string>
- #include <type_traits>
- #include "base/base_export.h"
- #include "base/check.h"
- #include "base/check_op.h"
- #include "base/compiler_specific.h"
- #include "base/strings/string_piece_forward.h" // IWYU pragma: export
- #include "build/build_config.h"
- namespace base {
- // internal --------------------------------------------------------------------
- // Many of the StringPiece functions use different implementations for the
- // 8-bit and 16-bit versions, and we don't want lots of template expansions in
- // this (very common) header that will slow down compilation.
- //
- // So here we define overloaded functions called by the StringPiece template.
- // For those that share an implementation, the two versions will expand to a
- // template internal to the .cc file.
- namespace internal {
- BASE_EXPORT size_t find(StringPiece self, StringPiece s, size_t pos);
- BASE_EXPORT size_t find(StringPiece16 self, StringPiece16 s, size_t pos);
- BASE_EXPORT size_t rfind(StringPiece self, StringPiece s, size_t pos);
- BASE_EXPORT size_t rfind(StringPiece16 self, StringPiece16 s, size_t pos);
- BASE_EXPORT size_t find_first_of(StringPiece self, StringPiece s, size_t pos);
- BASE_EXPORT size_t find_first_of(StringPiece16 self,
- StringPiece16 s,
- size_t pos);
- BASE_EXPORT size_t find_first_not_of(StringPiece self,
- StringPiece s,
- size_t pos);
- BASE_EXPORT size_t find_first_not_of(StringPiece16 self,
- StringPiece16 s,
- size_t pos);
- BASE_EXPORT size_t find_last_of(StringPiece self, StringPiece s, size_t pos);
- BASE_EXPORT size_t find_last_of(StringPiece16 self,
- StringPiece16 s,
- size_t pos);
- BASE_EXPORT size_t find_last_not_of(StringPiece self,
- StringPiece s,
- size_t pos);
- BASE_EXPORT size_t find_last_not_of(StringPiece16 self,
- StringPiece16 s,
- size_t pos);
- BASE_EXPORT size_t find(WStringPiece self, WStringPiece s, size_t pos);
- BASE_EXPORT size_t rfind(WStringPiece self, WStringPiece s, size_t pos);
- BASE_EXPORT size_t find_first_of(WStringPiece self, WStringPiece s, size_t pos);
- BASE_EXPORT size_t find_first_not_of(WStringPiece self,
- WStringPiece s,
- size_t pos);
- BASE_EXPORT size_t find_last_of(WStringPiece self, WStringPiece s, size_t pos);
- BASE_EXPORT size_t find_last_not_of(WStringPiece self,
- WStringPiece s,
- size_t pos);
- } // namespace internal
- // BasicStringPiece ------------------------------------------------------------
- // Mirrors the C++17 version of std::basic_string_view<> as closely as possible,
- // except where noted below.
- template <typename CharT, typename Traits>
- class GSL_POINTER BasicStringPiece {
- public:
- using traits_type = Traits;
- using value_type = CharT;
- using pointer = CharT*;
- using const_pointer = const CharT*;
- using reference = CharT&;
- using const_reference = const CharT&;
- using const_iterator = const CharT*;
- using iterator = const_iterator;
- using const_reverse_iterator = std::reverse_iterator<const_iterator>;
- using reverse_iterator = const_reverse_iterator;
- using size_type = size_t;
- using difference_type = ptrdiff_t;
- constexpr BasicStringPiece() noexcept : ptr_(nullptr), length_(0) {}
- constexpr BasicStringPiece(const BasicStringPiece& other) noexcept = default;
- constexpr BasicStringPiece& operator=(const BasicStringPiece& view) noexcept =
- default;
- constexpr BasicStringPiece(const CharT* s, size_type count)
- : ptr_(s), length_(count) {}
- constexpr BasicStringPiece(const CharT* s)
- : ptr_(s), length_(s ? traits_type::length(s) : 0) {
- // Intentional STL deviation: Null-check instead of UB.
- CHECK(s);
- }
- // Explicitly disallow construction from nullptr. Note that this does not
- // catch construction from runtime strings that might be null.
- // Note: The following is just a more elaborate way of spelling
- // `BasicStringPiece(nullptr_t) = delete`, but unfortunately the terse form is
- // not supported by the PNaCl toolchain.
- template <class T, class = std::enable_if_t<std::is_null_pointer<T>::value>>
- BasicStringPiece(T) {
- static_assert(sizeof(T) == 0, // Always false.
- "StringPiece does not support construction from nullptr, use "
- "the default constructor instead.");
- }
- // These are necessary because std::basic_string provides construction from
- // (an object convertible to) a std::basic_string_view, as well as an explicit
- // cast operator to a std::basic_string_view, but (obviously) not from/to a
- // BasicStringPiece.
- BasicStringPiece(const std::basic_string<CharT>& str)
- : ptr_(str.data()), length_(str.size()) {}
- explicit operator std::basic_string<CharT>() const {
- return std::basic_string<CharT>(data(), size());
- }
- constexpr const_iterator begin() const noexcept { return ptr_; }
- constexpr const_iterator cbegin() const noexcept { return ptr_; }
- constexpr const_iterator end() const noexcept { return ptr_ + length_; }
- constexpr const_iterator cend() const noexcept { return ptr_ + length_; }
- constexpr const_reverse_iterator rbegin() const noexcept {
- return const_reverse_iterator(ptr_ + length_);
- }
- constexpr const_reverse_iterator crbegin() const noexcept {
- return const_reverse_iterator(ptr_ + length_);
- }
- constexpr const_reverse_iterator rend() const noexcept {
- return const_reverse_iterator(ptr_);
- }
- constexpr const_reverse_iterator crend() const noexcept {
- return const_reverse_iterator(ptr_);
- }
- constexpr const_reference operator[](size_type pos) const {
- // Intentional STL deviation: Bounds-check instead of UB.
- return at(pos);
- }
- constexpr const_reference at(size_type pos) const {
- CHECK_LT(pos, size());
- return data()[pos];
- }
- constexpr const_reference front() const { return operator[](0); }
- constexpr const_reference back() const { return operator[](size() - 1); }
- constexpr const_pointer data() const noexcept { return ptr_; }
- constexpr size_type size() const noexcept { return length_; }
- constexpr size_type length() const noexcept { return length_; }
- constexpr size_type max_size() const {
- return std::numeric_limits<size_type>::max() / sizeof(CharT);
- }
- [[nodiscard]] constexpr bool empty() const noexcept { return size() == 0; }
- constexpr void remove_prefix(size_type n) {
- // Intentional STL deviation: Bounds-check instead of UB.
- CHECK_LE(n, size());
- ptr_ += n;
- length_ -= n;
- }
- constexpr void remove_suffix(size_type n) {
- // Intentional STL deviation: Bounds-check instead of UB.
- CHECK_LE(n, size());
- length_ -= n;
- }
- constexpr void swap(BasicStringPiece& v) noexcept {
- // Note: Cannot use std::swap() since it is not constexpr until C++20.
- const const_pointer ptr = ptr_;
- ptr_ = v.ptr_;
- v.ptr_ = ptr;
- const size_type length = length_;
- length_ = v.length_;
- v.length_ = length;
- }
- constexpr size_type copy(CharT* dest,
- size_type count,
- size_type pos = 0) const {
- CHECK_LE(pos, size());
- const size_type rcount = std::min(count, size() - pos);
- traits_type::copy(dest, data() + pos, rcount);
- return rcount;
- }
- constexpr BasicStringPiece substr(size_type pos = 0,
- size_type count = npos) const {
- CHECK_LE(pos, size());
- const size_type rcount = std::min(count, size() - pos);
- return {data() + pos, rcount};
- }
- constexpr int compare(BasicStringPiece v) const noexcept {
- const size_type rlen = std::min(size(), v.size());
- const int result = traits_type::compare(data(), v.data(), rlen);
- if (result != 0)
- return result;
- if (size() == v.size())
- return 0;
- return size() < v.size() ? -1 : 1;
- }
- constexpr int compare(size_type pos1,
- size_type count1,
- BasicStringPiece v) const {
- return substr(pos1, count1).compare(v);
- }
- constexpr int compare(size_type pos1,
- size_type count1,
- BasicStringPiece v,
- size_type pos2,
- size_type count2) const {
- return substr(pos1, count1).compare(v.substr(pos2, count2));
- }
- constexpr int compare(const CharT* s) const {
- return compare(BasicStringPiece(s));
- }
- constexpr int compare(size_type pos1,
- size_type count1,
- const CharT* s) const {
- return substr(pos1, count1).compare(BasicStringPiece(s));
- }
- constexpr int compare(size_type pos1,
- size_type count1,
- const CharT* s,
- size_type count2) const {
- return substr(pos1, count1).compare(BasicStringPiece(s, count2));
- }
- constexpr size_type find(BasicStringPiece v,
- size_type pos = 0) const noexcept {
- if (is_constant_evaluated()) {
- if (v.size() > size())
- return npos;
- for (size_type p = pos; p <= size() - v.size(); ++p) {
- if (!compare(p, v.size(), v))
- return p;
- }
- return npos;
- }
- return internal::find(*this, v, pos);
- }
- constexpr size_type find(CharT ch, size_type pos = 0) const noexcept {
- if (pos >= size())
- return npos;
- const const_pointer result =
- traits_type::find(data() + pos, size() - pos, ch);
- return result ? static_cast<size_type>(result - data()) : npos;
- }
- constexpr size_type find(const CharT* s,
- size_type pos,
- size_type count) const {
- return find(BasicStringPiece(s, count), pos);
- }
- constexpr size_type find(const CharT* s, size_type pos = 0) const {
- return find(BasicStringPiece(s), pos);
- }
- constexpr size_type rfind(BasicStringPiece v,
- size_type pos = npos) const noexcept {
- if (is_constant_evaluated()) {
- if (v.size() > size())
- return npos;
- for (size_type p = std::min(size() - v.size(), pos);; --p) {
- if (!compare(p, v.size(), v))
- return p;
- if (!p)
- break;
- }
- return npos;
- }
- return internal::rfind(*this, v, pos);
- }
- constexpr size_type rfind(CharT c, size_type pos = npos) const noexcept {
- if (empty())
- return npos;
- for (size_t i = std::min(pos, size() - 1);; --i) {
- if (data()[i] == c)
- return i;
- if (i == 0)
- break;
- }
- return npos;
- }
- constexpr size_type rfind(const CharT* s,
- size_type pos,
- size_type count) const {
- return rfind(BasicStringPiece(s, count), pos);
- }
- constexpr size_type rfind(const CharT* s, size_type pos = npos) const {
- return rfind(BasicStringPiece(s), pos);
- }
- constexpr size_type find_first_of(BasicStringPiece v,
- size_type pos = 0) const noexcept {
- if (is_constant_evaluated()) {
- if (empty() || v.empty())
- return npos;
- for (size_type p = pos; p < size(); ++p) {
- if (v.find(data()[p]) != npos)
- return p;
- }
- return npos;
- }
- return internal::find_first_of(*this, v, pos);
- }
- constexpr size_type find_first_of(CharT c, size_type pos = 0) const noexcept {
- return find(c, pos);
- }
- constexpr size_type find_first_of(const CharT* s,
- size_type pos,
- size_type count) const {
- return find_first_of(BasicStringPiece(s, count), pos);
- }
- constexpr size_type find_first_of(const CharT* s, size_type pos = 0) const {
- return find_first_of(BasicStringPiece(s), pos);
- }
- constexpr size_type find_last_of(BasicStringPiece v,
- size_type pos = npos) const noexcept {
- if (is_constant_evaluated()) {
- if (empty() || v.empty())
- return npos;
- for (size_type p = std::min(pos, size() - 1);; --p) {
- if (v.find(data()[p]) != npos)
- return p;
- if (!p)
- break;
- }
- return npos;
- }
- return internal::find_last_of(*this, v, pos);
- }
- constexpr size_type find_last_of(CharT c,
- size_type pos = npos) const noexcept {
- return rfind(c, pos);
- }
- constexpr size_type find_last_of(const CharT* s,
- size_type pos,
- size_type count) const {
- return find_last_of(BasicStringPiece(s, count), pos);
- }
- constexpr size_type find_last_of(const CharT* s, size_type pos = npos) const {
- return find_last_of(BasicStringPiece(s), pos);
- }
- constexpr size_type find_first_not_of(BasicStringPiece v,
- size_type pos = 0) const noexcept {
- if (is_constant_evaluated()) {
- if (empty())
- return npos;
- for (size_type p = pos; p < size(); ++p) {
- if (v.find(data()[p]) == npos)
- return p;
- }
- return npos;
- }
- return internal::find_first_not_of(*this, v, pos);
- }
- constexpr size_type find_first_not_of(CharT c,
- size_type pos = 0) const noexcept {
- if (empty())
- return npos;
- for (; pos < size(); ++pos) {
- if (data()[pos] != c)
- return pos;
- }
- return npos;
- }
- constexpr size_type find_first_not_of(const CharT* s,
- size_type pos,
- size_type count) const {
- return find_first_not_of(BasicStringPiece(s, count), pos);
- }
- constexpr size_type find_first_not_of(const CharT* s,
- size_type pos = 0) const {
- return find_first_not_of(BasicStringPiece(s), pos);
- }
- constexpr size_type find_last_not_of(BasicStringPiece v,
- size_type pos = npos) const noexcept {
- if (is_constant_evaluated()) {
- if (empty())
- return npos;
- for (size_type p = std::min(pos, size() - 1);; --p) {
- if (v.find(data()[p]) == npos)
- return p;
- if (!p)
- break;
- }
- return npos;
- }
- return internal::find_last_not_of(*this, v, pos);
- }
- constexpr size_type find_last_not_of(CharT c,
- size_type pos = npos) const noexcept {
- if (empty())
- return npos;
- for (size_t i = std::min(pos, size() - 1);; --i) {
- if (data()[i] != c)
- return i;
- if (i == 0)
- break;
- }
- return npos;
- }
- constexpr size_type find_last_not_of(const CharT* s,
- size_type pos,
- size_type count) const {
- return find_last_not_of(BasicStringPiece(s, count), pos);
- }
- constexpr size_type find_last_not_of(const CharT* s,
- size_type pos = npos) const {
- return find_last_not_of(BasicStringPiece(s), pos);
- }
- static constexpr size_type npos = size_type(-1);
- protected:
- const_pointer ptr_;
- size_type length_;
- };
- // static
- template <typename CharT, typename Traits>
- const typename BasicStringPiece<CharT, Traits>::size_type
- BasicStringPiece<CharT, Traits>::npos;
- // MSVC doesn't like complex extern templates and DLLs.
- #if !defined(COMPILER_MSVC)
- extern template class BASE_EXPORT BasicStringPiece<char>;
- extern template class BASE_EXPORT BasicStringPiece<char16_t>;
- #endif
- template <typename CharT, typename Traits>
- constexpr bool operator==(BasicStringPiece<CharT, Traits> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return lhs.size() == rhs.size() && lhs.compare(rhs) == 0;
- }
- // Here and below we make use of std::common_type_t to emulate
- // std::type_identity (part of C++20). This creates a non-deduced context, so
- // that we can compare StringPieces with types that implicitly convert to
- // StringPieces. See https://wg21.link/n3766 for details.
- // Furthermore, we require dummy template parameters for these overloads to work
- // around a name mangling issue on Windows.
- template <typename CharT, typename Traits, int = 1>
- constexpr bool operator==(
- BasicStringPiece<CharT, Traits> lhs,
- std::common_type_t<BasicStringPiece<CharT, Traits>> rhs) noexcept {
- return lhs.size() == rhs.size() && lhs.compare(rhs) == 0;
- }
- template <typename CharT, typename Traits, int = 2>
- constexpr bool operator==(
- std::common_type_t<BasicStringPiece<CharT, Traits>> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return lhs.size() == rhs.size() && lhs.compare(rhs) == 0;
- }
- template <typename CharT, typename Traits>
- constexpr bool operator!=(BasicStringPiece<CharT, Traits> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return !(lhs == rhs);
- }
- template <typename CharT, typename Traits, int = 1>
- constexpr bool operator!=(
- BasicStringPiece<CharT, Traits> lhs,
- std::common_type_t<BasicStringPiece<CharT, Traits>> rhs) noexcept {
- return !(lhs == rhs);
- }
- template <typename CharT, typename Traits, int = 2>
- constexpr bool operator!=(
- std::common_type_t<BasicStringPiece<CharT, Traits>> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return !(lhs == rhs);
- }
- template <typename CharT, typename Traits>
- constexpr bool operator<(BasicStringPiece<CharT, Traits> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return lhs.compare(rhs) < 0;
- }
- template <typename CharT, typename Traits, int = 1>
- constexpr bool operator<(
- BasicStringPiece<CharT, Traits> lhs,
- std::common_type_t<BasicStringPiece<CharT, Traits>> rhs) noexcept {
- return lhs.compare(rhs) < 0;
- }
- template <typename CharT, typename Traits, int = 2>
- constexpr bool operator<(
- std::common_type_t<BasicStringPiece<CharT, Traits>> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return lhs.compare(rhs) < 0;
- }
- template <typename CharT, typename Traits>
- constexpr bool operator>(BasicStringPiece<CharT, Traits> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return rhs < lhs;
- }
- template <typename CharT, typename Traits, int = 1>
- constexpr bool operator>(
- BasicStringPiece<CharT, Traits> lhs,
- std::common_type_t<BasicStringPiece<CharT, Traits>> rhs) noexcept {
- return rhs < lhs;
- }
- template <typename CharT, typename Traits, int = 2>
- constexpr bool operator>(
- std::common_type_t<BasicStringPiece<CharT, Traits>> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return rhs < lhs;
- }
- template <typename CharT, typename Traits>
- constexpr bool operator<=(BasicStringPiece<CharT, Traits> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return !(rhs < lhs);
- }
- template <typename CharT, typename Traits, int = 1>
- constexpr bool operator<=(
- BasicStringPiece<CharT, Traits> lhs,
- std::common_type_t<BasicStringPiece<CharT, Traits>> rhs) noexcept {
- return !(rhs < lhs);
- }
- template <typename CharT, typename Traits, int = 2>
- constexpr bool operator<=(
- std::common_type_t<BasicStringPiece<CharT, Traits>> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return !(rhs < lhs);
- }
- template <typename CharT, typename Traits>
- constexpr bool operator>=(BasicStringPiece<CharT, Traits> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return !(lhs < rhs);
- }
- template <typename CharT, typename Traits, int = 1>
- constexpr bool operator>=(
- BasicStringPiece<CharT, Traits> lhs,
- std::common_type_t<BasicStringPiece<CharT, Traits>> rhs) noexcept {
- return !(lhs < rhs);
- }
- template <typename CharT, typename Traits, int = 2>
- constexpr bool operator>=(
- std::common_type_t<BasicStringPiece<CharT, Traits>> lhs,
- BasicStringPiece<CharT, Traits> rhs) noexcept {
- return !(lhs < rhs);
- }
- BASE_EXPORT std::ostream& operator<<(std::ostream& o, StringPiece piece);
- // Not in the STL: convenience functions to output non-UTF-8 strings to an
- // 8-bit-width stream.
- BASE_EXPORT std::ostream& operator<<(std::ostream& o, StringPiece16 piece);
- BASE_EXPORT std::ostream& operator<<(std::ostream& o, WStringPiece piece);
- // Intentionally omitted (since Chromium does not use character literals):
- // operator""sv.
- // Stand-ins for the STL's std::hash<> specializations.
- template <typename StringPieceType>
- struct StringPieceHashImpl {
- // This is a custom hash function. We don't use the ones already defined for
- // string and std::u16string directly because it would require the string
- // constructors to be called, which we don't want.
- size_t operator()(StringPieceType sp) const {
- size_t result = 0;
- for (auto c : sp)
- result = (result * 131) + static_cast<size_t>(c);
- return result;
- }
- };
- using StringPieceHash = StringPieceHashImpl<StringPiece>;
- using StringPiece16Hash = StringPieceHashImpl<StringPiece16>;
- using WStringPieceHash = StringPieceHashImpl<WStringPiece>;
- } // namespace base
- #endif // BASE_STRINGS_STRING_PIECE_H_
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