--- /dev/null
+//
+// Copyright 2017 The Abseil Authors.
+//
+// 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
+//
+// https://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.
+//
+// -----------------------------------------------------------------------------
+// File: string_view.h
+// -----------------------------------------------------------------------------
+//
+// This file contains the definition of the `absl::string_view` class. A
+// `string_view` points to a contiguous span of characters, often part or all of
+// another `std::string`, double-quoted string literal, character array, or even
+// another `string_view`.
+//
+// This `absl::string_view` abstraction is designed to be a drop-in
+// replacement for the C++17 `std::string_view` abstraction.
+#ifndef ABSL_STRINGS_STRING_VIEW_H_
+#define ABSL_STRINGS_STRING_VIEW_H_
+
+#include <algorithm>
+#include "absl/base/config.h"
+
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+
+#include <string_view> // IWYU pragma: export
+
+namespace absl {
+using std::string_view;
+} // namespace absl
+
+#else // ABSL_HAVE_STD_STRING_VIEW
+
+#include <cassert>
+#include <cstddef>
+#include <cstring>
+#include <iosfwd>
+#include <iterator>
+#include <limits>
+#include <string>
+
+#include "absl/base/internal/throw_delegate.h"
+#include "absl/base/macros.h"
+#include "absl/base/port.h"
+
+namespace absl {
+
+// absl::string_view
+//
+// A `string_view` provides a lightweight view into the string data provided by
+// a `std::string`, double-quoted string literal, character array, or even
+// another `string_view`. A `string_view` does *not* own the string to which it
+// points, and that data cannot be modified through the view.
+//
+// You can use `string_view` as a function or method parameter anywhere a
+// parameter can receive a double-quoted string literal, `const char*`,
+// `std::string`, or another `absl::string_view` argument with no need to copy
+// the string data. Systematic use of `string_view` within function arguments
+// reduces data copies and `strlen()` calls.
+//
+// Because of its small size, prefer passing `string_view` by value:
+//
+// void MyFunction(absl::string_view arg);
+//
+// If circumstances require, you may also pass one by const reference:
+//
+// void MyFunction(const absl::string_view& arg); // not preferred
+//
+// Passing by value generates slightly smaller code for many architectures.
+//
+// In either case, the source data of the `string_view` must outlive the
+// `string_view` itself.
+//
+// A `string_view` is also suitable for local variables if you know that the
+// lifetime of the underlying object is longer than the lifetime of your
+// `string_view` variable. However, beware of binding a `string_view` to a
+// temporary value:
+//
+// // BAD use of string_view: lifetime problem
+// absl::string_view sv = obj.ReturnAString();
+//
+// // GOOD use of string_view: str outlives sv
+// std::string str = obj.ReturnAString();
+// absl::string_view sv = str;
+//
+// Due to lifetime issues, a `string_view` is sometimes a poor choice for a
+// return value and usually a poor choice for a data member. If you do use a
+// `string_view` this way, it is your responsibility to ensure that the object
+// pointed to by the `string_view` outlives the `string_view`.
+//
+// A `string_view` may represent a whole string or just part of a string. For
+// example, when splitting a string, `std::vector<absl::string_view>` is a
+// natural data type for the output.
+//
+// When constructed from a source which is nul-terminated, the `string_view`
+// itself will not include the nul-terminator unless a specific size (including
+// the nul) is passed to the constructor. As a result, common idioms that work
+// on nul-terminated strings do not work on `string_view` objects. If you write
+// code that scans a `string_view`, you must check its length rather than test
+// for nul, for example. Note, however, that nuls may still be embedded within
+// a `string_view` explicitly.
+//
+// You may create a null `string_view` in two ways:
+//
+// absl::string_view sv();
+// absl::string_view sv(nullptr, 0);
+//
+// For the above, `sv.data() == nullptr`, `sv.length() == 0`, and
+// `sv.empty() == true`. Also, if you create a `string_view` with a non-null
+// pointer then `sv.data() != nullptr`. Thus, you can use `string_view()` to
+// signal an undefined value that is different from other `string_view` values
+// in a similar fashion to how `const char* p1 = nullptr;` is different from
+// `const char* p2 = "";`. However, in practice, it is not recommended to rely
+// on this behavior.
+//
+// Be careful not to confuse a null `string_view` with an empty one. A null
+// `string_view` is an empty `string_view`, but some empty `string_view`s are
+// not null. Prefer checking for emptiness over checking for null.
+//
+// There are many ways to create an empty string_view:
+//
+// const char* nullcp = nullptr;
+// // string_view.size() will return 0 in all cases.
+// absl::string_view();
+// absl::string_view(nullcp, 0);
+// absl::string_view("");
+// absl::string_view("", 0);
+// absl::string_view("abcdef", 0);
+// absl::string_view("abcdef" + 6, 0);
+//
+// All empty `string_view` objects whether null or not, are equal:
+//
+// absl::string_view() == absl::string_view("", 0)
+// absl::string_view(nullptr, 0) == absl::string_view("abcdef"+6, 0)
+class string_view {
+ public:
+ using traits_type = std::char_traits<char>;
+ using value_type = char;
+ using pointer = char*;
+ using const_pointer = const char*;
+ using reference = char&;
+ using const_reference = const char&;
+ using const_iterator = const char*;
+ 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 = std::ptrdiff_t;
+
+ static constexpr size_type npos = static_cast<size_type>(-1);
+
+ // Null `string_view` constructor
+ constexpr string_view() noexcept : ptr_(nullptr), length_(0) {}
+
+ // Implicit constructors
+
+ template <typename Allocator>
+ string_view( // NOLINT(runtime/explicit)
+ const std::basic_string<char, std::char_traits<char>, Allocator>&
+ str) noexcept
+ : ptr_(str.data()), length_(CheckLengthInternal(str.size())) {}
+
+ // Implicit constructor of a `string_view` from nul-terminated `str`. When
+ // accepting possibly null strings, use `absl::NullSafeStringView(str)`
+ // instead (see below).
+#if ABSL_HAVE_BUILTIN(__builtin_strlen) || \
+ (defined(__GNUC__) && !defined(__clang__))
+ // GCC has __builtin_strlen according to
+ // https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Other-Builtins.html, but
+ // ABSL_HAVE_BUILTIN doesn't detect that, so we use the extra checks above.
+ // __builtin_strlen is constexpr.
+ constexpr string_view(const char* str) // NOLINT(runtime/explicit)
+ : ptr_(str),
+ length_(CheckLengthInternal(str ? __builtin_strlen(str) : 0)) {}
+#else
+ constexpr string_view(const char* str) // NOLINT(runtime/explicit)
+ : ptr_(str), length_(CheckLengthInternal(str ? strlen(str) : 0)) {}
+#endif
+
+ // Implicit constructor of a `string_view` from a `const char*` and length.
+ constexpr string_view(const char* data, size_type len)
+ : ptr_(data), length_(CheckLengthInternal(len)) {}
+
+ // NOTE: Harmlessly omitted to work around gdb bug.
+ // constexpr string_view(const string_view&) noexcept = default;
+ // string_view& operator=(const string_view&) noexcept = default;
+
+ // Iterators
+
+ // string_view::begin()
+ //
+ // Returns an iterator pointing to the first character at the beginning of the
+ // `string_view`, or `end()` if the `string_view` is empty.
+ constexpr const_iterator begin() const noexcept { return ptr_; }
+
+ // string_view::end()
+ //
+ // Returns an iterator pointing just beyond the last character at the end of
+ // the `string_view`. This iterator acts as a placeholder; attempting to
+ // access it results in undefined behavior.
+ constexpr const_iterator end() const noexcept { return ptr_ + length_; }
+
+ // string_view::cbegin()
+ //
+ // Returns a const iterator pointing to the first character at the beginning
+ // of the `string_view`, or `end()` if the `string_view` is empty.
+ constexpr const_iterator cbegin() const noexcept { return begin(); }
+
+ // string_view::cend()
+ //
+ // Returns a const iterator pointing just beyond the last character at the end
+ // of the `string_view`. This pointer acts as a placeholder; attempting to
+ // access its element results in undefined behavior.
+ constexpr const_iterator cend() const noexcept { return end(); }
+
+ // string_view::rbegin()
+ //
+ // Returns a reverse iterator pointing to the last character at the end of the
+ // `string_view`, or `rend()` if the `string_view` is empty.
+ const_reverse_iterator rbegin() const noexcept {
+ return const_reverse_iterator(end());
+ }
+
+ // string_view::rend()
+ //
+ // Returns a reverse iterator pointing just before the first character at the
+ // beginning of the `string_view`. This pointer acts as a placeholder;
+ // attempting to access its element results in undefined behavior.
+ const_reverse_iterator rend() const noexcept {
+ return const_reverse_iterator(begin());
+ }
+
+ // string_view::crbegin()
+ //
+ // Returns a const reverse iterator pointing to the last character at the end
+ // of the `string_view`, or `crend()` if the `string_view` is empty.
+ const_reverse_iterator crbegin() const noexcept { return rbegin(); }
+
+ // string_view::crend()
+ //
+ // Returns a const reverse iterator pointing just before the first character
+ // at the beginning of the `string_view`. This pointer acts as a placeholder;
+ // attempting to access its element results in undefined behavior.
+ const_reverse_iterator crend() const noexcept { return rend(); }
+
+ // Capacity Utilities
+
+ // string_view::size()
+ //
+ // Returns the number of characters in the `string_view`.
+ constexpr size_type size() const noexcept {
+ return length_;
+ }
+
+ // string_view::length()
+ //
+ // Returns the number of characters in the `string_view`. Alias for `size()`.
+ constexpr size_type length() const noexcept { return size(); }
+
+ // string_view::max_size()
+ //
+ // Returns the maximum number of characters the `string_view` can hold.
+ constexpr size_type max_size() const noexcept { return kMaxSize; }
+
+ // string_view::empty()
+ //
+ // Checks if the `string_view` is empty (refers to no characters).
+ constexpr bool empty() const noexcept { return length_ == 0; }
+
+ // string_view::operator[]
+ //
+ // Returns the ith element of an `string_view` using the array operator.
+ // Note that this operator does not perform any bounds checking.
+ constexpr const_reference operator[](size_type i) const { return ptr_[i]; }
+
+ // string_view::front()
+ //
+ // Returns the first element of a `string_view`.
+ constexpr const_reference front() const { return ptr_[0]; }
+
+ // string_view::back()
+ //
+ // Returns the last element of a `string_view`.
+ constexpr const_reference back() const { return ptr_[size() - 1]; }
+
+ // string_view::data()
+ //
+ // Returns a pointer to the underlying character array (which is of course
+ // stored elsewhere). Note that `string_view::data()` may contain embedded nul
+ // characters, but the returned buffer may or may not be nul-terminated;
+ // therefore, do not pass `data()` to a routine that expects a nul-terminated
+ // std::string.
+ constexpr const_pointer data() const noexcept { return ptr_; }
+
+ // Modifiers
+
+ // string_view::remove_prefix()
+ //
+ // Removes the first `n` characters from the `string_view`. Note that the
+ // underlying std::string is not changed, only the view.
+ void remove_prefix(size_type n) {
+ assert(n <= length_);
+ ptr_ += n;
+ length_ -= n;
+ }
+
+ // string_view::remove_suffix()
+ //
+ // Removes the last `n` characters from the `string_view`. Note that the
+ // underlying std::string is not changed, only the view.
+ void remove_suffix(size_type n) {
+ assert(n <= length_);
+ length_ -= n;
+ }
+
+ // string_view::swap()
+ //
+ // Swaps this `string_view` with another `string_view`.
+ void swap(string_view& s) noexcept {
+ auto t = *this;
+ *this = s;
+ s = t;
+ }
+
+ // Explicit conversion operators
+
+ // Converts to `std::basic_string`.
+ template <typename A>
+ explicit operator std::basic_string<char, traits_type, A>() const {
+ if (!data()) return {};
+ return std::basic_string<char, traits_type, A>(data(), size());
+ }
+
+ // string_view::copy()
+ //
+ // Copies the contents of the `string_view` at offset `pos` and length `n`
+ // into `buf`.
+ size_type copy(char* buf, size_type n, size_type pos = 0) const;
+
+ // string_view::substr()
+ //
+ // Returns a "substring" of the `string_view` (at offset `pos` and length
+ // `n`) as another string_view. This function throws `std::out_of_bounds` if
+ // `pos > size`.
+ string_view substr(size_type pos, size_type n = npos) const {
+ if (ABSL_PREDICT_FALSE(pos > length_))
+ base_internal::ThrowStdOutOfRange("absl::string_view::substr");
+ n = (std::min)(n, length_ - pos);
+ return string_view(ptr_ + pos, n);
+ }
+
+ // string_view::compare()
+ //
+ // Performs a lexicographical comparison between the `string_view` and
+ // another `absl::string_view`, returning -1 if `this` is less than, 0 if
+ // `this` is equal to, and 1 if `this` is greater than the passed std::string
+ // view. Note that in the case of data equality, a further comparison is made
+ // on the respective sizes of the two `string_view`s to determine which is
+ // smaller, equal, or greater.
+ int compare(string_view x) const noexcept {
+ auto min_length = (std::min)(length_, x.length_);
+ if (min_length > 0) {
+ int r = memcmp(ptr_, x.ptr_, min_length);
+ if (r < 0) return -1;
+ if (r > 0) return 1;
+ }
+ if (length_ < x.length_) return -1;
+ if (length_ > x.length_) return 1;
+ return 0;
+ }
+
+ // Overload of `string_view::compare()` for comparing a substring of the
+ // 'string_view` and another `absl::string_view`.
+ int compare(size_type pos1, size_type count1, string_view v) const {
+ return substr(pos1, count1).compare(v);
+ }
+
+ // Overload of `string_view::compare()` for comparing a substring of the
+ // `string_view` and a substring of another `absl::string_view`.
+ int compare(size_type pos1, size_type count1, string_view v, size_type pos2,
+ size_type count2) const {
+ return substr(pos1, count1).compare(v.substr(pos2, count2));
+ }
+
+ // Overload of `string_view::compare()` for comparing a `string_view` and a
+ // a different C-style std::string `s`.
+ int compare(const char* s) const { return compare(string_view(s)); }
+
+ // Overload of `string_view::compare()` for comparing a substring of the
+ // `string_view` and a different std::string C-style std::string `s`.
+ int compare(size_type pos1, size_type count1, const char* s) const {
+ return substr(pos1, count1).compare(string_view(s));
+ }
+
+ // Overload of `string_view::compare()` for comparing a substring of the
+ // `string_view` and a substring of a different C-style std::string `s`.
+ int compare(size_type pos1, size_type count1, const char* s,
+ size_type count2) const {
+ return substr(pos1, count1).compare(string_view(s, count2));
+ }
+
+ // Find Utilities
+
+ // string_view::find()
+ //
+ // Finds the first occurrence of the substring `s` within the `string_view`,
+ // returning the position of the first character's match, or `npos` if no
+ // match was found.
+ size_type find(string_view s, size_type pos = 0) const noexcept;
+
+ // Overload of `string_view::find()` for finding the given character `c`
+ // within the `string_view`.
+ size_type find(char c, size_type pos = 0) const noexcept;
+
+ // string_view::rfind()
+ //
+ // Finds the last occurrence of a substring `s` within the `string_view`,
+ // returning the position of the first character's match, or `npos` if no
+ // match was found.
+ size_type rfind(string_view s, size_type pos = npos) const
+ noexcept;
+
+ // Overload of `string_view::rfind()` for finding the last given character `c`
+ // within the `string_view`.
+ size_type rfind(char c, size_type pos = npos) const noexcept;
+
+ // string_view::find_first_of()
+ //
+ // Finds the first occurrence of any of the characters in `s` within the
+ // `string_view`, returning the start position of the match, or `npos` if no
+ // match was found.
+ size_type find_first_of(string_view s, size_type pos = 0) const
+ noexcept;
+
+ // Overload of `string_view::find_first_of()` for finding a character `c`
+ // within the `string_view`.
+ size_type find_first_of(char c, size_type pos = 0) const
+ noexcept {
+ return find(c, pos);
+ }
+
+ // string_view::find_last_of()
+ //
+ // Finds the last occurrence of any of the characters in `s` within the
+ // `string_view`, returning the start position of the match, or `npos` if no
+ // match was found.
+ size_type find_last_of(string_view s, size_type pos = npos) const
+ noexcept;
+
+ // Overload of `string_view::find_last_of()` for finding a character `c`
+ // within the `string_view`.
+ size_type find_last_of(char c, size_type pos = npos) const
+ noexcept {
+ return rfind(c, pos);
+ }
+
+ // string_view::find_first_not_of()
+ //
+ // Finds the first occurrence of any of the characters not in `s` within the
+ // `string_view`, returning the start position of the first non-match, or
+ // `npos` if no non-match was found.
+ size_type find_first_not_of(string_view s, size_type pos = 0) const noexcept;
+
+ // Overload of `string_view::find_first_not_of()` for finding a character
+ // that is not `c` within the `string_view`.
+ size_type find_first_not_of(char c, size_type pos = 0) const noexcept;
+
+ // string_view::find_last_not_of()
+ //
+ // Finds the last occurrence of any of the characters not in `s` within the
+ // `string_view`, returning the start position of the last non-match, or
+ // `npos` if no non-match was found.
+ size_type find_last_not_of(string_view s,
+ size_type pos = npos) const noexcept;
+
+ // Overload of `string_view::find_last_not_of()` for finding a character
+ // that is not `c` within the `string_view`.
+ size_type find_last_not_of(char c, size_type pos = npos) const
+ noexcept;
+
+ private:
+ static constexpr size_type kMaxSize =
+ (std::numeric_limits<difference_type>::max)();
+
+ static constexpr size_type CheckLengthInternal(size_type len) {
+ return ABSL_ASSERT(len <= kMaxSize), len;
+ }
+
+ const char* ptr_;
+ size_type length_;
+};
+
+// This large function is defined inline so that in a fairly common case where
+// one of the arguments is a literal, the compiler can elide a lot of the
+// following comparisons.
+inline bool operator==(string_view x, string_view y) noexcept {
+ auto len = x.size();
+ if (len != y.size()) {
+ return false;
+ }
+
+ return x.data() == y.data() || len <= 0 ||
+ memcmp(x.data(), y.data(), len) == 0;
+}
+
+inline bool operator!=(string_view x, string_view y) noexcept {
+ return !(x == y);
+}
+
+inline bool operator<(string_view x, string_view y) noexcept {
+ auto min_size = (std::min)(x.size(), y.size());
+ const int r = min_size == 0 ? 0 : memcmp(x.data(), y.data(), min_size);
+ return (r < 0) || (r == 0 && x.size() < y.size());
+}
+
+inline bool operator>(string_view x, string_view y) noexcept { return y < x; }
+
+inline bool operator<=(string_view x, string_view y) noexcept {
+ return !(y < x);
+}
+
+inline bool operator>=(string_view x, string_view y) noexcept {
+ return !(x < y);
+}
+
+// IO Insertion Operator
+std::ostream& operator<<(std::ostream& o, string_view piece);
+
+} // namespace absl
+
+#endif // ABSL_HAVE_STD_STRING_VIEW
+
+namespace absl {
+
+// ClippedSubstr()
+//
+// Like `s.substr(pos, n)`, but clips `pos` to an upper bound of `s.size()`.
+// Provided because std::string_view::substr throws if `pos > size()`
+inline string_view ClippedSubstr(string_view s, size_t pos,
+ size_t n = string_view::npos) {
+ pos = (std::min)(pos, static_cast<size_t>(s.size()));
+ return s.substr(pos, n);
+}
+
+// NullSafeStringView()
+//
+// Creates an `absl::string_view` from a pointer `p` even if it's null-valued.
+// This function should be used where an `absl::string_view` can be created from
+// a possibly-null pointer.
+inline string_view NullSafeStringView(const char* p) {
+ return p ? string_view(p) : string_view();
+}
+
+} // namespace absl
+
+#endif // ABSL_STRINGS_STRING_VIEW_H_
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