diff options
Diffstat (limited to 'abseil-cpp/absl/strings/str_cat.h')
| -rw-r--r-- | abseil-cpp/absl/strings/str_cat.h | 172 |
1 files changed, 147 insertions, 25 deletions
diff --git a/abseil-cpp/absl/strings/str_cat.h b/abseil-cpp/absl/strings/str_cat.h index a8a85c7..d5f71ff 100644 --- a/abseil-cpp/absl/strings/str_cat.h +++ b/abseil-cpp/absl/strings/str_cat.h @@ -48,18 +48,58 @@ // `StrCat()` or `StrAppend()`. You may specify a minimum hex field width using // a `PadSpec` enum. // +// User-defined types can be formatted with the `AbslStringify()` customization +// point. The API relies on detecting an overload in the user-defined type's +// namespace of a free (non-member) `AbslStringify()` function as a definition +// (typically declared as a friend and implemented in-line. +// with the following signature: +// +// class MyClass { ... }; +// +// template <typename Sink> +// void AbslStringify(Sink& sink, const MyClass& value); +// +// An `AbslStringify()` overload for a type should only be declared in the same +// file and namespace as said type. +// +// Note that `AbslStringify()` also supports use with `absl::StrFormat()` and +// `absl::Substitute()`. +// +// Example: +// +// struct Point { +// // To add formatting support to `Point`, we simply need to add a free +// // (non-member) function `AbslStringify()`. This method specifies how +// // Point should be printed when absl::StrCat() is called on it. You can add +// // such a free function using a friend declaration within the body of the +// // class. The sink parameter is a templated type to avoid requiring +// // dependencies. +// template <typename Sink> friend void AbslStringify(Sink& +// sink, const Point& p) { +// absl::Format(&sink, "(%v, %v)", p.x, p.y); +// } +// +// int x; +// int y; +// }; // ----------------------------------------------------------------------------- #ifndef ABSL_STRINGS_STR_CAT_H_ #define ABSL_STRINGS_STR_CAT_H_ +#include <algorithm> #include <array> #include <cstdint> +#include <cstring> #include <string> #include <type_traits> +#include <utility> #include <vector> +#include "absl/base/attributes.h" #include "absl/base/port.h" +#include "absl/strings/internal/has_absl_stringify.h" +#include "absl/strings/internal/stringify_sink.h" #include "absl/strings/numbers.h" #include "absl/strings/string_view.h" @@ -164,6 +204,27 @@ struct Hex { explicit Hex(Pointee* v, PadSpec spec = absl::kNoPad) : Hex(spec, reinterpret_cast<uintptr_t>(v)) {} + template <typename S> + friend void AbslStringify(S& sink, Hex hex) { + static_assert( + numbers_internal::kFastToBufferSize >= 32, + "This function only works when output buffer >= 32 bytes long"); + char buffer[numbers_internal::kFastToBufferSize]; + char* const end = &buffer[numbers_internal::kFastToBufferSize]; + auto real_width = + absl::numbers_internal::FastHexToBufferZeroPad16(hex.value, end - 16); + if (real_width >= hex.width) { + sink.Append(absl::string_view(end - real_width, real_width)); + } else { + // Pad first 16 chars because FastHexToBufferZeroPad16 pads only to 16 and + // max pad width can be up to 20. + std::memset(end - 32, hex.fill, 16); + // Patch up everything else up to the real_width. + std::memset(end - real_width - 16, hex.fill, 16); + sink.Append(absl::string_view(end - hex.width, hex.width)); + } + } + private: Hex(PadSpec spec, uint64_t v) : value(v), @@ -198,6 +259,38 @@ struct Dec { : spec - absl::kZeroPad2 + 2), fill(spec >= absl::kSpacePad2 ? ' ' : '0'), neg(v < 0) {} + + template <typename S> + friend void AbslStringify(S& sink, Dec dec) { + assert(dec.width <= numbers_internal::kFastToBufferSize); + char buffer[numbers_internal::kFastToBufferSize]; + char* const end = &buffer[numbers_internal::kFastToBufferSize]; + char* const minfill = end - dec.width; + char* writer = end; + uint64_t val = dec.value; + while (val > 9) { + *--writer = '0' + (val % 10); + val /= 10; + } + *--writer = '0' + static_cast<char>(val); + if (dec.neg) *--writer = '-'; + + ptrdiff_t fillers = writer - minfill; + if (fillers > 0) { + // Tricky: if the fill character is ' ', then it's <fill><+/-><digits> + // But...: if the fill character is '0', then it's <+/-><fill><digits> + bool add_sign_again = false; + if (dec.neg && dec.fill == '0') { // If filling with '0', + ++writer; // ignore the sign we just added + add_sign_again = true; // and re-add the sign later. + } + writer -= fillers; + std::fill_n(writer, fillers, dec.fill); + if (add_sign_again) *--writer = '-'; + } + + sink.Append(absl::string_view(writer, static_cast<size_t>(end - writer))); + } }; // ----------------------------------------------------------------------------- @@ -205,8 +298,10 @@ struct Dec { // ----------------------------------------------------------------------------- // // The `AlphaNum` class acts as the main parameter type for `StrCat()` and -// `StrAppend()`, providing efficient conversion of numeric, boolean, and -// hexadecimal values (through the `Hex` type) into strings. +// `StrAppend()`, providing efficient conversion of numeric, boolean, decimal, +// and hexadecimal values (through the `Dec` and `Hex` types) into strings. +// `AlphaNum` should only be used as a function parameter. Do not instantiate +// `AlphaNum` directly as a stack variable. class AlphaNum { public: @@ -214,43 +309,59 @@ class AlphaNum { // A bool ctor would also convert incoming pointers (bletch). AlphaNum(int x) // NOLINT(runtime/explicit) - : piece_(digits_, - numbers_internal::FastIntToBuffer(x, digits_) - &digits_[0]) {} + : piece_(digits_, static_cast<size_t>( + numbers_internal::FastIntToBuffer(x, digits_) - + &digits_[0])) {} AlphaNum(unsigned int x) // NOLINT(runtime/explicit) - : piece_(digits_, - numbers_internal::FastIntToBuffer(x, digits_) - &digits_[0]) {} + : piece_(digits_, static_cast<size_t>( + numbers_internal::FastIntToBuffer(x, digits_) - + &digits_[0])) {} AlphaNum(long x) // NOLINT(*) - : piece_(digits_, - numbers_internal::FastIntToBuffer(x, digits_) - &digits_[0]) {} + : piece_(digits_, static_cast<size_t>( + numbers_internal::FastIntToBuffer(x, digits_) - + &digits_[0])) {} AlphaNum(unsigned long x) // NOLINT(*) - : piece_(digits_, - numbers_internal::FastIntToBuffer(x, digits_) - &digits_[0]) {} + : piece_(digits_, static_cast<size_t>( + numbers_internal::FastIntToBuffer(x, digits_) - + &digits_[0])) {} AlphaNum(long long x) // NOLINT(*) - : piece_(digits_, - numbers_internal::FastIntToBuffer(x, digits_) - &digits_[0]) {} + : piece_(digits_, static_cast<size_t>( + numbers_internal::FastIntToBuffer(x, digits_) - + &digits_[0])) {} AlphaNum(unsigned long long x) // NOLINT(*) - : piece_(digits_, - numbers_internal::FastIntToBuffer(x, digits_) - &digits_[0]) {} + : piece_(digits_, static_cast<size_t>( + numbers_internal::FastIntToBuffer(x, digits_) - + &digits_[0])) {} AlphaNum(float f) // NOLINT(runtime/explicit) : piece_(digits_, numbers_internal::SixDigitsToBuffer(f, digits_)) {} AlphaNum(double f) // NOLINT(runtime/explicit) : piece_(digits_, numbers_internal::SixDigitsToBuffer(f, digits_)) {} - AlphaNum(Hex hex); // NOLINT(runtime/explicit) - AlphaNum(Dec dec); // NOLINT(runtime/explicit) - template <size_t size> AlphaNum( // NOLINT(runtime/explicit) - const strings_internal::AlphaNumBuffer<size>& buf) + const strings_internal::AlphaNumBuffer<size>& buf + ABSL_ATTRIBUTE_LIFETIME_BOUND) : piece_(&buf.data[0], buf.size) {} - AlphaNum(const char* c_str) : piece_(c_str) {} // NOLINT(runtime/explicit) - AlphaNum(absl::string_view pc) : piece_(pc) {} // NOLINT(runtime/explicit) + AlphaNum(const char* c_str // NOLINT(runtime/explicit) + ABSL_ATTRIBUTE_LIFETIME_BOUND) + : piece_(NullSafeStringView(c_str)) {} + AlphaNum(absl::string_view pc // NOLINT(runtime/explicit) + ABSL_ATTRIBUTE_LIFETIME_BOUND) + : piece_(pc) {} + + template <typename T, typename = typename std::enable_if< + strings_internal::HasAbslStringify<T>::value>::type> + AlphaNum( // NOLINT(runtime/explicit) + const T& v ABSL_ATTRIBUTE_LIFETIME_BOUND, + strings_internal::StringifySink&& sink ABSL_ATTRIBUTE_LIFETIME_BOUND = {}) + : piece_(strings_internal::ExtractStringification(sink, v)) {} template <typename Allocator> AlphaNum( // NOLINT(runtime/explicit) - const std::basic_string<char, std::char_traits<char>, Allocator>& str) + const std::basic_string<char, std::char_traits<char>, Allocator>& str + ABSL_ATTRIBUTE_LIFETIME_BOUND) : piece_(str) {} // Use string literals ":" instead of character literals ':'. @@ -263,13 +374,24 @@ class AlphaNum { const char* data() const { return piece_.data(); } absl::string_view Piece() const { return piece_; } - // Normal enums are already handled by the integer formatters. - // This overload matches only scoped enums. + // Match unscoped enums. Use integral promotion so that a `char`-backed + // enum becomes a wider integral type AlphaNum will accept. template <typename T, typename = typename std::enable_if< - std::is_enum<T>{} && !std::is_convertible<T, int>{}>::type> + std::is_enum<T>{} && std::is_convertible<T, int>{} && + !strings_internal::HasAbslStringify<T>::value>::type> + AlphaNum(T e) // NOLINT(runtime/explicit) + : AlphaNum(+e) {} + + // This overload matches scoped enums. We must explicitly cast to the + // underlying type, but use integral promotion for the same reason as above. + template <typename T, + typename std::enable_if< + std::is_enum<T>{} && !std::is_convertible<T, int>{} && + !strings_internal::HasAbslStringify<T>::value, + char*>::type = nullptr> AlphaNum(T e) // NOLINT(runtime/explicit) - : AlphaNum(static_cast<typename std::underlying_type<T>::type>(e)) {} + : AlphaNum(+static_cast<typename std::underlying_type<T>::type>(e)) {} // vector<bool>::reference and const_reference require special help to // convert to `AlphaNum` because it requires two user defined conversions. |