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Diffstat (limited to 'third_party/abseil_cpp/absl/strings/str_format.h')
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diff --git a/third_party/abseil_cpp/absl/strings/str_format.h b/third_party/abseil_cpp/absl/strings/str_format.h new file mode 100644 index 0000000000..01465107e1 --- /dev/null +++ b/third_party/abseil_cpp/absl/strings/str_format.h @@ -0,0 +1,813 @@ +// +// Copyright 2018 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: str_format.h +// ----------------------------------------------------------------------------- +// +// The `str_format` library is a typesafe replacement for the family of +// `printf()` string formatting routines within the `<cstdio>` standard library +// header. Like the `printf` family, `str_format` uses a "format string" to +// perform argument substitutions based on types. See the `FormatSpec` section +// below for format string documentation. +// +// Example: +// +// std::string s = absl::StrFormat( +// "%s %s You have $%d!", "Hello", name, dollars); +// +// The library consists of the following basic utilities: +// +// * `absl::StrFormat()`, a type-safe replacement for `std::sprintf()`, to +// write a format string to a `string` value. +// * `absl::StrAppendFormat()` to append a format string to a `string` +// * `absl::StreamFormat()` to more efficiently write a format string to a +// stream, such as`std::cout`. +// * `absl::PrintF()`, `absl::FPrintF()` and `absl::SNPrintF()` as +// replacements for `std::printf()`, `std::fprintf()` and `std::snprintf()`. +// +// Note: a version of `std::sprintf()` is not supported as it is +// generally unsafe due to buffer overflows. +// +// Additionally, you can provide a format string (and its associated arguments) +// using one of the following abstractions: +// +// * A `FormatSpec` class template fully encapsulates a format string and its +// type arguments and is usually provided to `str_format` functions as a +// variadic argument of type `FormatSpec<Arg...>`. The `FormatSpec<Args...>` +// template is evaluated at compile-time, providing type safety. +// * A `ParsedFormat` instance, which encapsulates a specific, pre-compiled +// format string for a specific set of type(s), and which can be passed +// between API boundaries. (The `FormatSpec` type should not be used +// directly except as an argument type for wrapper functions.) +// +// The `str_format` library provides the ability to output its format strings to +// arbitrary sink types: +// +// * A generic `Format()` function to write outputs to arbitrary sink types, +// which must implement a `FormatRawSink` interface. +// +// * A `FormatUntyped()` function that is similar to `Format()` except it is +// loosely typed. `FormatUntyped()` is not a template and does not perform +// any compile-time checking of the format string; instead, it returns a +// boolean from a runtime check. +// +// In addition, the `str_format` library provides extension points for +// augmenting formatting to new types. See "StrFormat Extensions" below. + +#ifndef ABSL_STRINGS_STR_FORMAT_H_ +#define ABSL_STRINGS_STR_FORMAT_H_ + +#include <cstdio> +#include <string> + +#include "absl/strings/internal/str_format/arg.h" // IWYU pragma: export +#include "absl/strings/internal/str_format/bind.h" // IWYU pragma: export +#include "absl/strings/internal/str_format/checker.h" // IWYU pragma: export +#include "absl/strings/internal/str_format/extension.h" // IWYU pragma: export +#include "absl/strings/internal/str_format/parser.h" // IWYU pragma: export + +namespace absl { +ABSL_NAMESPACE_BEGIN + +// UntypedFormatSpec +// +// A type-erased class that can be used directly within untyped API entry +// points. An `UntypedFormatSpec` is specifically used as an argument to +// `FormatUntyped()`. +// +// Example: +// +// absl::UntypedFormatSpec format("%d"); +// std::string out; +// CHECK(absl::FormatUntyped(&out, format, {absl::FormatArg(1)})); +class UntypedFormatSpec { + public: + UntypedFormatSpec() = delete; + UntypedFormatSpec(const UntypedFormatSpec&) = delete; + UntypedFormatSpec& operator=(const UntypedFormatSpec&) = delete; + + explicit UntypedFormatSpec(string_view s) : spec_(s) {} + + protected: + explicit UntypedFormatSpec(const str_format_internal::ParsedFormatBase* pc) + : spec_(pc) {} + + private: + friend str_format_internal::UntypedFormatSpecImpl; + str_format_internal::UntypedFormatSpecImpl spec_; +}; + +// FormatStreamed() +// +// Takes a streamable argument and returns an object that can print it +// with '%s'. Allows printing of types that have an `operator<<` but no +// intrinsic type support within `StrFormat()` itself. +// +// Example: +// +// absl::StrFormat("%s", absl::FormatStreamed(obj)); +template <typename T> +str_format_internal::StreamedWrapper<T> FormatStreamed(const T& v) { + return str_format_internal::StreamedWrapper<T>(v); +} + +// FormatCountCapture +// +// This class provides a way to safely wrap `StrFormat()` captures of `%n` +// conversions, which denote the number of characters written by a formatting +// operation to this point, into an integer value. +// +// This wrapper is designed to allow safe usage of `%n` within `StrFormat(); in +// the `printf()` family of functions, `%n` is not safe to use, as the `int *` +// buffer can be used to capture arbitrary data. +// +// Example: +// +// int n = 0; +// std::string s = absl::StrFormat("%s%d%n", "hello", 123, +// absl::FormatCountCapture(&n)); +// EXPECT_EQ(8, n); +class FormatCountCapture { + public: + explicit FormatCountCapture(int* p) : p_(p) {} + + private: + // FormatCountCaptureHelper is used to define FormatConvertImpl() for this + // class. + friend struct str_format_internal::FormatCountCaptureHelper; + // Unused() is here because of the false positive from -Wunused-private-field + // p_ is used in the templated function of the friend FormatCountCaptureHelper + // class. + int* Unused() { return p_; } + int* p_; +}; + +// FormatSpec +// +// The `FormatSpec` type defines the makeup of a format string within the +// `str_format` library. It is a variadic class template that is evaluated at +// compile-time, according to the format string and arguments that are passed to +// it. +// +// You should not need to manipulate this type directly. You should only name it +// if you are writing wrapper functions which accept format arguments that will +// be provided unmodified to functions in this library. Such a wrapper function +// might be a class method that provides format arguments and/or internally uses +// the result of formatting. +// +// For a `FormatSpec` to be valid at compile-time, it must be provided as +// either: +// +// * A `constexpr` literal or `absl::string_view`, which is how it most often +// used. +// * A `ParsedFormat` instantiation, which ensures the format string is +// valid before use. (See below.) +// +// Example: +// +// // Provided as a string literal. +// absl::StrFormat("Welcome to %s, Number %d!", "The Village", 6); +// +// // Provided as a constexpr absl::string_view. +// constexpr absl::string_view formatString = "Welcome to %s, Number %d!"; +// absl::StrFormat(formatString, "The Village", 6); +// +// // Provided as a pre-compiled ParsedFormat object. +// // Note that this example is useful only for illustration purposes. +// absl::ParsedFormat<'s', 'd'> formatString("Welcome to %s, Number %d!"); +// absl::StrFormat(formatString, "TheVillage", 6); +// +// A format string generally follows the POSIX syntax as used within the POSIX +// `printf` specification. +// +// (See http://pubs.opengroup.org/onlinepubs/9699919799/functions/fprintf.html.) +// +// In specific, the `FormatSpec` supports the following type specifiers: +// * `c` for characters +// * `s` for strings +// * `d` or `i` for integers +// * `o` for unsigned integer conversions into octal +// * `x` or `X` for unsigned integer conversions into hex +// * `u` for unsigned integers +// * `f` or `F` for floating point values into decimal notation +// * `e` or `E` for floating point values into exponential notation +// * `a` or `A` for floating point values into hex exponential notation +// * `g` or `G` for floating point values into decimal or exponential +// notation based on their precision +// * `p` for pointer address values +// * `n` for the special case of writing out the number of characters +// written to this point. The resulting value must be captured within an +// `absl::FormatCountCapture` type. +// +// Implementation-defined behavior: +// * A null pointer provided to "%s" or "%p" is output as "(nil)". +// * A non-null pointer provided to "%p" is output in hex as if by %#x or +// %#lx. +// +// NOTE: `o`, `x\X` and `u` will convert signed values to their unsigned +// counterpart before formatting. +// +// Examples: +// "%c", 'a' -> "a" +// "%c", 32 -> " " +// "%s", "C" -> "C" +// "%s", std::string("C++") -> "C++" +// "%d", -10 -> "-10" +// "%o", 10 -> "12" +// "%x", 16 -> "10" +// "%f", 123456789 -> "123456789.000000" +// "%e", .01 -> "1.00000e-2" +// "%a", -3.0 -> "-0x1.8p+1" +// "%g", .01 -> "1e-2" +// "%p", (void*)&value -> "0x7ffdeb6ad2a4" +// +// int n = 0; +// std::string s = absl::StrFormat( +// "%s%d%n", "hello", 123, absl::FormatCountCapture(&n)); +// EXPECT_EQ(8, n); +// +// The `FormatSpec` intrinsically supports all of these fundamental C++ types: +// +// * Characters: `char`, `signed char`, `unsigned char` +// * Integers: `int`, `short`, `unsigned short`, `unsigned`, `long`, +// `unsigned long`, `long long`, `unsigned long long` +// * Floating-point: `float`, `double`, `long double` +// +// However, in the `str_format` library, a format conversion specifies a broader +// C++ conceptual category instead of an exact type. For example, `%s` binds to +// any string-like argument, so `std::string`, `absl::string_view`, and +// `const char*` are all accepted. Likewise, `%d` accepts any integer-like +// argument, etc. + +template <typename... Args> +using FormatSpec = str_format_internal::FormatSpecTemplate< + str_format_internal::ArgumentToConv<Args>()...>; + +// ParsedFormat +// +// A `ParsedFormat` is a class template representing a preparsed `FormatSpec`, +// with template arguments specifying the conversion characters used within the +// format string. Such characters must be valid format type specifiers, and +// these type specifiers are checked at compile-time. +// +// Instances of `ParsedFormat` can be created, copied, and reused to speed up +// formatting loops. A `ParsedFormat` may either be constructed statically, or +// dynamically through its `New()` factory function, which only constructs a +// runtime object if the format is valid at that time. +// +// Example: +// +// // Verified at compile time. +// absl::ParsedFormat<'s', 'd'> formatString("Welcome to %s, Number %d!"); +// absl::StrFormat(formatString, "TheVillage", 6); +// +// // Verified at runtime. +// auto format_runtime = absl::ParsedFormat<'d'>::New(format_string); +// if (format_runtime) { +// value = absl::StrFormat(*format_runtime, i); +// } else { +// ... error case ... +// } + +#if defined(__cpp_nontype_template_parameter_auto) +// If C++17 is available, an 'extended' format is also allowed that can specify +// multiple conversion characters per format argument, using a combination of +// `absl::FormatConversionCharSet` enum values (logically a set union) +// via the `|` operator. (Single character-based arguments are still accepted, +// but cannot be combined). Some common conversions also have predefined enum +// values, such as `absl::FormatConversionCharSet::kIntegral`. +// +// Example: +// // Extended format supports multiple conversion characters per argument, +// // specified via a combination of `FormatConversionCharSet` enums. +// using MyFormat = absl::ParsedFormat<absl::FormatConversionCharSet::d | +// absl::FormatConversionCharSet::x>; +// MyFormat GetFormat(bool use_hex) { +// if (use_hex) return MyFormat("foo %x bar"); +// return MyFormat("foo %d bar"); +// } +// // `format` can be used with any value that supports 'd' and 'x', +// // like `int`. +// auto format = GetFormat(use_hex); +// value = StringF(format, i); +template <auto... Conv> +using ParsedFormat = absl::str_format_internal::ExtendedParsedFormat< + absl::str_format_internal::ToFormatConversionCharSet(Conv)...>; +#else +template <char... Conv> +using ParsedFormat = str_format_internal::ExtendedParsedFormat< + absl::str_format_internal::ToFormatConversionCharSet(Conv)...>; +#endif // defined(__cpp_nontype_template_parameter_auto) + +// StrFormat() +// +// Returns a `string` given a `printf()`-style format string and zero or more +// additional arguments. Use it as you would `sprintf()`. `StrFormat()` is the +// primary formatting function within the `str_format` library, and should be +// used in most cases where you need type-safe conversion of types into +// formatted strings. +// +// The format string generally consists of ordinary character data along with +// one or more format conversion specifiers (denoted by the `%` character). +// Ordinary character data is returned unchanged into the result string, while +// each conversion specification performs a type substitution from +// `StrFormat()`'s other arguments. See the comments for `FormatSpec` for full +// information on the makeup of this format string. +// +// Example: +// +// std::string s = absl::StrFormat( +// "Welcome to %s, Number %d!", "The Village", 6); +// EXPECT_EQ("Welcome to The Village, Number 6!", s); +// +// Returns an empty string in case of error. +template <typename... Args> +ABSL_MUST_USE_RESULT std::string StrFormat(const FormatSpec<Args...>& format, + const Args&... args) { + return str_format_internal::FormatPack( + str_format_internal::UntypedFormatSpecImpl::Extract(format), + {str_format_internal::FormatArgImpl(args)...}); +} + +// StrAppendFormat() +// +// Appends to a `dst` string given a format string, and zero or more additional +// arguments, returning `*dst` as a convenience for chaining purposes. Appends +// nothing in case of error (but possibly alters its capacity). +// +// Example: +// +// std::string orig("For example PI is approximately "); +// std::cout << StrAppendFormat(&orig, "%12.6f", 3.14); +template <typename... Args> +std::string& StrAppendFormat(std::string* dst, + const FormatSpec<Args...>& format, + const Args&... args) { + return str_format_internal::AppendPack( + dst, str_format_internal::UntypedFormatSpecImpl::Extract(format), + {str_format_internal::FormatArgImpl(args)...}); +} + +// StreamFormat() +// +// Writes to an output stream given a format string and zero or more arguments, +// generally in a manner that is more efficient than streaming the result of +// `absl:: StrFormat()`. The returned object must be streamed before the full +// expression ends. +// +// Example: +// +// std::cout << StreamFormat("%12.6f", 3.14); +template <typename... Args> +ABSL_MUST_USE_RESULT str_format_internal::Streamable StreamFormat( + const FormatSpec<Args...>& format, const Args&... args) { + return str_format_internal::Streamable( + str_format_internal::UntypedFormatSpecImpl::Extract(format), + {str_format_internal::FormatArgImpl(args)...}); +} + +// PrintF() +// +// Writes to stdout given a format string and zero or more arguments. This +// function is functionally equivalent to `std::printf()` (and type-safe); +// prefer `absl::PrintF()` over `std::printf()`. +// +// Example: +// +// std::string_view s = "Ulaanbaatar"; +// absl::PrintF("The capital of Mongolia is %s", s); +// +// Outputs: "The capital of Mongolia is Ulaanbaatar" +// +template <typename... Args> +int PrintF(const FormatSpec<Args...>& format, const Args&... args) { + return str_format_internal::FprintF( + stdout, str_format_internal::UntypedFormatSpecImpl::Extract(format), + {str_format_internal::FormatArgImpl(args)...}); +} + +// FPrintF() +// +// Writes to a file given a format string and zero or more arguments. This +// function is functionally equivalent to `std::fprintf()` (and type-safe); +// prefer `absl::FPrintF()` over `std::fprintf()`. +// +// Example: +// +// std::string_view s = "Ulaanbaatar"; +// absl::FPrintF(stdout, "The capital of Mongolia is %s", s); +// +// Outputs: "The capital of Mongolia is Ulaanbaatar" +// +template <typename... Args> +int FPrintF(std::FILE* output, const FormatSpec<Args...>& format, + const Args&... args) { + return str_format_internal::FprintF( + output, str_format_internal::UntypedFormatSpecImpl::Extract(format), + {str_format_internal::FormatArgImpl(args)...}); +} + +// SNPrintF() +// +// Writes to a sized buffer given a format string and zero or more arguments. +// This function is functionally equivalent to `std::snprintf()` (and +// type-safe); prefer `absl::SNPrintF()` over `std::snprintf()`. +// +// In particular, a successful call to `absl::SNPrintF()` writes at most `size` +// bytes of the formatted output to `output`, including a NUL-terminator, and +// returns the number of bytes that would have been written if truncation did +// not occur. In the event of an error, a negative value is returned and `errno` +// is set. +// +// Example: +// +// std::string_view s = "Ulaanbaatar"; +// char output[128]; +// absl::SNPrintF(output, sizeof(output), +// "The capital of Mongolia is %s", s); +// +// Post-condition: output == "The capital of Mongolia is Ulaanbaatar" +// +template <typename... Args> +int SNPrintF(char* output, std::size_t size, const FormatSpec<Args...>& format, + const Args&... args) { + return str_format_internal::SnprintF( + output, size, str_format_internal::UntypedFormatSpecImpl::Extract(format), + {str_format_internal::FormatArgImpl(args)...}); +} + +// ----------------------------------------------------------------------------- +// Custom Output Formatting Functions +// ----------------------------------------------------------------------------- + +// FormatRawSink +// +// FormatRawSink is a type erased wrapper around arbitrary sink objects +// specifically used as an argument to `Format()`. +// +// All the object has to do define an overload of `AbslFormatFlush()` for the +// sink, usually by adding a ADL-based free function in the same namespace as +// the sink: +// +// void AbslFormatFlush(MySink* dest, absl::string_view part); +// +// where `dest` is the pointer passed to `absl::Format()`. The function should +// append `part` to `dest`. +// +// FormatRawSink does not own the passed sink object. The passed object must +// outlive the FormatRawSink. +class FormatRawSink { + public: + // Implicitly convert from any type that provides the hook function as + // described above. + template <typename T, + typename = typename std::enable_if<std::is_constructible< + str_format_internal::FormatRawSinkImpl, T*>::value>::type> + FormatRawSink(T* raw) // NOLINT + : sink_(raw) {} + + private: + friend str_format_internal::FormatRawSinkImpl; + str_format_internal::FormatRawSinkImpl sink_; +}; + +// Format() +// +// Writes a formatted string to an arbitrary sink object (implementing the +// `absl::FormatRawSink` interface), using a format string and zero or more +// additional arguments. +// +// By default, `std::string`, `std::ostream`, and `absl::Cord` are supported as +// destination objects. If a `std::string` is used the formatted string is +// appended to it. +// +// `absl::Format()` is a generic version of `absl::StrAppendFormat()`, for +// custom sinks. The format string, like format strings for `StrFormat()`, is +// checked at compile-time. +// +// On failure, this function returns `false` and the state of the sink is +// unspecified. +template <typename... Args> +bool Format(FormatRawSink raw_sink, const FormatSpec<Args...>& format, + const Args&... args) { + return str_format_internal::FormatUntyped( + str_format_internal::FormatRawSinkImpl::Extract(raw_sink), + str_format_internal::UntypedFormatSpecImpl::Extract(format), + {str_format_internal::FormatArgImpl(args)...}); +} + +// FormatArg +// +// A type-erased handle to a format argument specifically used as an argument to +// `FormatUntyped()`. You may construct `FormatArg` by passing +// reference-to-const of any printable type. `FormatArg` is both copyable and +// assignable. The source data must outlive the `FormatArg` instance. See +// example below. +// +using FormatArg = str_format_internal::FormatArgImpl; + +// FormatUntyped() +// +// Writes a formatted string to an arbitrary sink object (implementing the +// `absl::FormatRawSink` interface), using an `UntypedFormatSpec` and zero or +// more additional arguments. +// +// This function acts as the most generic formatting function in the +// `str_format` library. The caller provides a raw sink, an unchecked format +// string, and (usually) a runtime specified list of arguments; no compile-time +// checking of formatting is performed within this function. As a result, a +// caller should check the return value to verify that no error occurred. +// On failure, this function returns `false` and the state of the sink is +// unspecified. +// +// The arguments are provided in an `absl::Span<const absl::FormatArg>`. +// Each `absl::FormatArg` object binds to a single argument and keeps a +// reference to it. The values used to create the `FormatArg` objects must +// outlive this function call. (See `str_format_arg.h` for information on +// the `FormatArg` class.)_ +// +// Example: +// +// std::optional<std::string> FormatDynamic( +// const std::string& in_format, +// const vector<std::string>& in_args) { +// std::string out; +// std::vector<absl::FormatArg> args; +// for (const auto& v : in_args) { +// // It is important that 'v' is a reference to the objects in in_args. +// // The values we pass to FormatArg must outlive the call to +// // FormatUntyped. +// args.emplace_back(v); +// } +// absl::UntypedFormatSpec format(in_format); +// if (!absl::FormatUntyped(&out, format, args)) { +// return std::nullopt; +// } +// return std::move(out); +// } +// +ABSL_MUST_USE_RESULT inline bool FormatUntyped( + FormatRawSink raw_sink, const UntypedFormatSpec& format, + absl::Span<const FormatArg> args) { + return str_format_internal::FormatUntyped( + str_format_internal::FormatRawSinkImpl::Extract(raw_sink), + str_format_internal::UntypedFormatSpecImpl::Extract(format), args); +} + +//------------------------------------------------------------------------------ +// StrFormat Extensions +//------------------------------------------------------------------------------ +// +// AbslFormatConvert() +// +// The StrFormat library provides a customization API for formatting +// user-defined types using absl::StrFormat(). The API relies on detecting an +// overload in the user-defined type's namespace of a free (non-member) +// `AbslFormatConvert()` function, usually as a friend definition with the +// following signature: +// +// absl::FormatConvertResult<...> AbslFormatConvert( +// const X& value, +// const absl::FormatConversionSpec& spec, +// absl::FormatSink *sink); +// +// An `AbslFormatConvert()` overload for a type should only be declared in the +// same file and namespace as said type. +// +// The abstractions within this definition include: +// +// * An `absl::FormatConversionSpec` to specify the fields to pull from a +// user-defined type's format string +// * An `absl::FormatSink` to hold the converted string data during the +// conversion process. +// * An `absl::FormatConvertResult` to hold the status of the returned +// formatting operation +// +// The return type encodes all the conversion characters that your +// AbslFormatConvert() routine accepts. The return value should be {true}. +// A return value of {false} will result in `StrFormat()` returning +// an empty string. This result will be propagated to the result of +// `FormatUntyped`. +// +// Example: +// +// struct Point { +// // To add formatting support to `Point`, we simply need to add a free +// // (non-member) function `AbslFormatConvert()`. This method interprets +// // `spec` to print in the request format. The allowed conversion characters +// // can be restricted via the type of the result, in this example +// // string and integral formatting are allowed (but not, for instance +// // floating point characters like "%f"). You can add such a free function +// // using a friend declaration within the body of the class: +// friend absl::FormatConvertResult<absl::FormatConversionCharSet::kString | +// absl::FormatConversionCharSet::kIntegral> +// AbslFormatConvert(const Point& p, const absl::FormatConversionSpec& spec, +// absl::FormatSink* s) { +// if (spec.conversion_char() == absl::FormatConversionChar::s) { +// s->Append(absl::StrCat("x=", p.x, " y=", p.y)); +// } else { +// s->Append(absl::StrCat(p.x, ",", p.y)); +// } +// return {true}; +// } +// +// int x; +// int y; +// }; + +// clang-format off + +// FormatConversionChar +// +// Specifies the formatting character provided in the format string +// passed to `StrFormat()`. +enum class FormatConversionChar : uint8_t { + c, s, // text + d, i, o, u, x, X, // int + f, F, e, E, g, G, a, A, // float + n, p // misc +}; +// clang-format on + +// FormatConversionSpec +// +// Specifies modifications to the conversion of the format string, through use +// of one or more format flags in the source format string. +class FormatConversionSpec { + public: + // FormatConversionSpec::is_basic() + // + // Indicates that width and precision are not specified, and no additional + // flags are set for this conversion character in the format string. + bool is_basic() const { return impl_.is_basic(); } + + // FormatConversionSpec::has_left_flag() + // + // Indicates whether the result should be left justified for this conversion + // character in the format string. This flag is set through use of a '-' + // character in the format string. E.g. "%-s" + bool has_left_flag() const { return impl_.has_left_flag(); } + + // FormatConversionSpec::has_show_pos_flag() + // + // Indicates whether a sign column is prepended to the result for this + // conversion character in the format string, even if the result is positive. + // This flag is set through use of a '+' character in the format string. + // E.g. "%+d" + bool has_show_pos_flag() const { return impl_.has_show_pos_flag(); } + + // FormatConversionSpec::has_sign_col_flag() + // + // Indicates whether a mandatory sign column is added to the result for this + // conversion character. This flag is set through use of a space character + // (' ') in the format string. E.g. "% i" + bool has_sign_col_flag() const { return impl_.has_sign_col_flag(); } + + // FormatConversionSpec::has_alt_flag() + // + // Indicates whether an "alternate" format is applied to the result for this + // conversion character. Alternative forms depend on the type of conversion + // character, and unallowed alternatives are undefined. This flag is set + // through use of a '#' character in the format string. E.g. "%#h" + bool has_alt_flag() const { return impl_.has_alt_flag(); } + + // FormatConversionSpec::has_zero_flag() + // + // Indicates whether zeroes should be prepended to the result for this + // conversion character instead of spaces. This flag is set through use of the + // '0' character in the format string. E.g. "%0f" + bool has_zero_flag() const { return impl_.has_zero_flag(); } + + // FormatConversionSpec::conversion_char() + // + // Returns the underlying conversion character. + FormatConversionChar conversion_char() const { + return impl_.conversion_char(); + } + + // FormatConversionSpec::width() + // + // Returns the specified width (indicated through use of a non-zero integer + // value or '*' character) of the conversion character. If width is + // unspecified, it returns a negative value. + int width() const { return impl_.width(); } + + // FormatConversionSpec::precision() + // + // Returns the specified precision (through use of the '.' character followed + // by a non-zero integer value or '*' character) of the conversion character. + // If precision is unspecified, it returns a negative value. + int precision() const { return impl_.precision(); } + + private: + explicit FormatConversionSpec( + str_format_internal::FormatConversionSpecImpl impl) + : impl_(impl) {} + + friend str_format_internal::FormatConversionSpecImpl; + + absl::str_format_internal::FormatConversionSpecImpl impl_; +}; + +// Type safe OR operator for FormatConversionCharSet to allow accepting multiple +// conversion chars in custom format converters. +constexpr FormatConversionCharSet operator|(FormatConversionCharSet a, + FormatConversionCharSet b) { + return static_cast<FormatConversionCharSet>(static_cast<uint64_t>(a) | + static_cast<uint64_t>(b)); +} + +// FormatConversionCharSet +// +// Specifies the _accepted_ conversion types as a template parameter to +// FormatConvertResult for custom implementations of `AbslFormatConvert`. +// Note the helper predefined alias definitions (kIntegral, etc.) below. +enum class FormatConversionCharSet : uint64_t { + // text + c = str_format_internal::FormatConversionCharToConvInt('c'), + s = str_format_internal::FormatConversionCharToConvInt('s'), + // integer + d = str_format_internal::FormatConversionCharToConvInt('d'), + i = str_format_internal::FormatConversionCharToConvInt('i'), + o = str_format_internal::FormatConversionCharToConvInt('o'), + u = str_format_internal::FormatConversionCharToConvInt('u'), + x = str_format_internal::FormatConversionCharToConvInt('x'), + X = str_format_internal::FormatConversionCharToConvInt('X'), + // Float + f = str_format_internal::FormatConversionCharToConvInt('f'), + F = str_format_internal::FormatConversionCharToConvInt('F'), + e = str_format_internal::FormatConversionCharToConvInt('e'), + E = str_format_internal::FormatConversionCharToConvInt('E'), + g = str_format_internal::FormatConversionCharToConvInt('g'), + G = str_format_internal::FormatConversionCharToConvInt('G'), + a = str_format_internal::FormatConversionCharToConvInt('a'), + A = str_format_internal::FormatConversionCharToConvInt('A'), + // misc + n = str_format_internal::FormatConversionCharToConvInt('n'), + p = str_format_internal::FormatConversionCharToConvInt('p'), + + // Used for width/precision '*' specification. + kStar = static_cast<uint64_t>( + absl::str_format_internal::FormatConversionCharSetInternal::kStar), + // Some predefined values: + kIntegral = d | i | u | o | x | X, + kFloating = a | e | f | g | A | E | F | G, + kNumeric = kIntegral | kFloating, + kString = s, + kPointer = p, +}; + +// FormatSink +// +// An abstraction to which conversions write their string data. +// +class FormatSink { + public: + // Appends `count` copies of `ch`. + void Append(size_t count, char ch) { sink_->Append(count, ch); } + + void Append(string_view v) { sink_->Append(v); } + + // Appends the first `precision` bytes of `v`. If this is less than + // `width`, spaces will be appended first (if `left` is false), or + // after (if `left` is true) to ensure the total amount appended is + // at least `width`. + bool PutPaddedString(string_view v, int width, int precision, bool left) { + return sink_->PutPaddedString(v, width, precision, left); + } + + private: + friend str_format_internal::FormatSinkImpl; + explicit FormatSink(str_format_internal::FormatSinkImpl* s) : sink_(s) {} + str_format_internal::FormatSinkImpl* sink_; +}; + +// FormatConvertResult +// +// Indicates whether a call to AbslFormatConvert() was successful. +// This return type informs the StrFormat extension framework (through +// ADL but using the return type) of what conversion characters are supported. +// It is strongly discouraged to return {false}, as this will result in an +// empty string in StrFormat. +template <FormatConversionCharSet C> +struct FormatConvertResult { + bool value; +}; + +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_STRINGS_STR_FORMAT_H_ |