diff options
Diffstat (limited to 'absl/strings/string_view.h')
| -rw-r--r-- | absl/strings/string_view.h | 65 |
1 files changed, 30 insertions, 35 deletions
diff --git a/absl/strings/string_view.h b/absl/strings/string_view.h index 4a5e4d8a..df6f1ae4 100644 --- a/absl/strings/string_view.h +++ b/absl/strings/string_view.h @@ -19,7 +19,7 @@ // // 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 std::string literal, character array, or even +// 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 @@ -35,9 +35,9 @@ #include <string_view> namespace absl { -inline namespace lts_2018_06_20 { +inline namespace lts_2018_12_18 { using std::string_view; -} // inline namespace lts_2018_06_20 +} // inline namespace lts_2018_12_18 } // namespace absl #else // ABSL_HAVE_STD_STRING_VIEW @@ -55,19 +55,19 @@ using std::string_view; #include "absl/base/port.h" namespace absl { -inline namespace lts_2018_06_20 { +inline namespace lts_2018_12_18 { // absl::string_view // -// A `string_view` provides a lightweight view into the std::string data provided by -// a `std::string`, double-quoted std::string literal, character array, or even -// another `string_view`. A `string_view` does *not* own the std::string to which it +// 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 std::string literal, `const char*`, +// parameter can receive a double-quoted string literal, `const char*`, // `std::string`, or another `absl::string_view` argument with no need to copy -// the std::string data. Systematic use of `string_view` within function arguments +// 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: @@ -100,8 +100,8 @@ inline namespace lts_2018_06_20 { // `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 std::string or just part of a std::string. For -// example, when splitting a std::string, `std::vector<absl::string_view>` is a +// 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. // // @@ -144,7 +144,7 @@ inline namespace lts_2018_06_20 { // 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) +// absl::string_view(nullptr, 0) == absl::string_view("abcdef"+6, 0) class string_view { public: using traits_type = std::char_traits<char>; @@ -176,8 +176,19 @@ class string_view { // 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(StrLenInternal(str))) {} + : 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) @@ -343,7 +354,7 @@ class string_view { // // 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'. + // `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"); @@ -354,7 +365,7 @@ class string_view { // 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 + // 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 @@ -482,23 +493,7 @@ class string_view { private: static constexpr size_type kMaxSize = - std::numeric_limits<difference_type>::max(); - - // check whether __builtin_strlen is provided by the compiler. - // GCC doesn't have __has_builtin() - // (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66970), - // but has __builtin_strlen according to - // https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Other-Builtins.html. -#if ABSL_HAVE_BUILTIN(__builtin_strlen) || \ - (defined(__GNUC__) && !defined(__clang__)) - static constexpr size_type StrLenInternal(const char* str) { - return str ? __builtin_strlen(str) : 0; - } -#else - static constexpr size_type StrLenInternal(const char* str) { - return str ? strlen(str) : 0; - } -#endif + (std::numeric_limits<difference_type>::max)(); static constexpr size_type CheckLengthInternal(size_type len) { return ABSL_ASSERT(len <= kMaxSize), len; @@ -543,13 +538,13 @@ inline bool operator>=(string_view x, string_view y) noexcept { // IO Insertion Operator std::ostream& operator<<(std::ostream& o, string_view piece); -} // inline namespace lts_2018_06_20 +} // inline namespace lts_2018_12_18 } // namespace absl #endif // ABSL_HAVE_STD_STRING_VIEW namespace absl { -inline namespace lts_2018_06_20 { +inline namespace lts_2018_12_18 { // ClippedSubstr() // @@ -570,7 +565,7 @@ inline string_view NullSafeStringView(const char* p) { return p ? string_view(p) : string_view(); } -} // inline namespace lts_2018_06_20 +} // inline namespace lts_2018_12_18 } // namespace absl #endif // ABSL_STRINGS_STRING_VIEW_H_ |