From 4491d606df34c44efda47b6d17b605262f17e182 Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Thu, 21 Jun 2018 12:55:12 -0700 Subject: Export of internal Abseil changes. -- 70f43a482d7d4ae4a255f17ca02b0106653dd600 by Shaindel Schwartz : Internal change PiperOrigin-RevId: 201571193 -- 93e6e9c2e683158be49d9dd1f5cb1a91d0c0f556 by Abseil Team : Internal change. PiperOrigin-RevId: 201567108 -- fbd8ee94fbe9f2448e5adf5e88706f9c8216048f by Juemin Yang : str_format release PiperOrigin-RevId: 201565129 -- 387faa301555a8a888c4429df52734aa806dca46 by Abseil Team : Adds a defaulted allocator parameter to the size_type constructor of InlinedVector PiperOrigin-RevId: 201558711 -- 39b15ea2c68d7129d70cbde7e71af900032595ec by Matt Calabrese : Update the variant implementation to eliminate unnecessary checking on alternative access when the index is known or required to be correct. PiperOrigin-RevId: 201529535 -- adab77f1f7bb363aa534297f22aae2b0f08889ea by Abseil Team : Import of CCTZ from GitHub. PiperOrigin-RevId: 201458388 -- a701dc0ba62e3cadf0de14203415b91df4ee8151 by Greg Falcon : Internal cleanup PiperOrigin-RevId: 201394836 -- 8a7191410b8f440fdfa27f722ff05e451502ab61 by Abseil Team : Import of CCTZ from GitHub. PiperOrigin-RevId: 201369269 GitOrigin-RevId: 70f43a482d7d4ae4a255f17ca02b0106653dd600 Change-Id: I8ab073b30b4e27405a3b6da2c826bb4f3f0b9af6 --- absl/strings/internal/str_format/parser.h | 291 ++++++++++++++++++++++++++++++ 1 file changed, 291 insertions(+) create mode 100644 absl/strings/internal/str_format/parser.h (limited to 'absl/strings/internal/str_format/parser.h') diff --git a/absl/strings/internal/str_format/parser.h b/absl/strings/internal/str_format/parser.h new file mode 100644 index 0000000..5bebc95 --- /dev/null +++ b/absl/strings/internal/str_format/parser.h @@ -0,0 +1,291 @@ +#ifndef ABSL_STRINGS_INTERNAL_STR_FORMAT_PARSER_H_ +#define ABSL_STRINGS_INTERNAL_STR_FORMAT_PARSER_H_ + +#include +#include +#include + +#include +#include +#include +#include +#include +#include + +#include "absl/strings/internal/str_format/checker.h" +#include "absl/strings/internal/str_format/extension.h" + +namespace absl { +namespace str_format_internal { + +// The analyzed properties of a single specified conversion. +struct UnboundConversion { + UnboundConversion() + : flags() /* This is required to zero all the fields of flags. */ { + flags.basic = true; + } + + class InputValue { + public: + void set_value(int value) { + assert(value >= 0); + value_ = value; + } + int value() const { return value_; } + + // Marks the value as "from arg". aka the '*' format. + // Requires `value >= 1`. + // When set, is_from_arg() return true and get_from_arg() returns the + // original value. + // `value()`'s return value is unspecfied in this state. + void set_from_arg(int value) { + assert(value > 0); + value_ = -value - 1; + } + bool is_from_arg() const { return value_ < -1; } + int get_from_arg() const { + assert(is_from_arg()); + return -value_ - 1; + } + + private: + int value_ = -1; + }; + + // No need to initialize. It will always be set in the parser. + int arg_position; + + InputValue width; + InputValue precision; + + Flags flags; + LengthMod length_mod; + ConversionChar conv; +}; + +// Consume conversion spec prefix (not including '%') of '*src' if valid. +// Examples of valid specs would be e.g.: "s", "d", "-12.6f". +// If valid, the front of src is advanced such that src becomes the +// part following the conversion spec, and the spec part is broken down and +// returned in 'conv'. +// If invalid, returns false and leaves 'src' unmodified. +// For example: +// Given "d9", returns "d", and leaves src="9", +// Given "!", returns "" and leaves src="!". +bool ConsumeUnboundConversion(string_view* src, UnboundConversion* conv, + int* next_arg); + +// Parse the format std::string provided in 'src' and pass the identified items into +// 'consumer'. +// Text runs will be passed by calling +// Consumer::Append(string_view); +// ConversionItems will be passed by calling +// Consumer::ConvertOne(UnboundConversion, string_view); +// In the case of ConvertOne, the string_view that is passed is the +// portion of the format std::string corresponding to the conversion, not including +// the leading %. On success, it returns true. On failure, it stops and returns +// false. +template +bool ParseFormatString(string_view src, Consumer consumer) { + int next_arg = 0; + while (!src.empty()) { + const char* percent = + static_cast(memchr(src.begin(), '%', src.size())); + if (!percent) { + // We found the last substring. + return consumer.Append(src); + } + // We found a percent, so push the text run then process the percent. + size_t percent_loc = percent - src.data(); + if (!consumer.Append(string_view(src.data(), percent_loc))) return false; + if (percent + 1 >= src.end()) return false; + + UnboundConversion conv; + + switch (percent[1]) { + case '%': + if (!consumer.Append("%")) return false; + src.remove_prefix(percent_loc + 2); + continue; + +#define PARSER_CASE(ch) \ + case #ch[0]: \ + src.remove_prefix(percent_loc + 2); \ + conv.conv = ConversionChar::FromId(ConversionChar::ch); \ + conv.arg_position = ++next_arg; \ + break; + ABSL_CONVERSION_CHARS_EXPAND_(PARSER_CASE, ); +#undef PARSER_CASE + + default: + src.remove_prefix(percent_loc + 1); + if (!ConsumeUnboundConversion(&src, &conv, &next_arg)) return false; + break; + } + if (next_arg == 0) { + // This indicates an error in the format std::string. + // The only way to get next_arg == 0 is to have a positional argument + // first which sets next_arg to -1 and then a non-positional argument + // which does ++next_arg. + // Checking here seems to be the cheapeast place to do it. + return false; + } + if (!consumer.ConvertOne( + conv, string_view(percent + 1, src.data() - (percent + 1)))) { + return false; + } + } + return true; +} + +// Always returns true, or fails to compile in a constexpr context if s does not +// point to a constexpr char array. +constexpr bool EnsureConstexpr(string_view s) { + return s.empty() || s[0] == s[0]; +} + +class ParsedFormatBase { + public: + explicit ParsedFormatBase(string_view format, bool allow_ignored, + std::initializer_list convs); + + ParsedFormatBase(const ParsedFormatBase& other) { *this = other; } + + ParsedFormatBase(ParsedFormatBase&& other) { *this = std::move(other); } + + ParsedFormatBase& operator=(const ParsedFormatBase& other) { + if (this == &other) return *this; + has_error_ = other.has_error_; + items_ = other.items_; + size_t text_size = items_.empty() ? 0 : items_.back().text_end; + data_.reset(new char[text_size]); + memcpy(data_.get(), other.data_.get(), text_size); + return *this; + } + + ParsedFormatBase& operator=(ParsedFormatBase&& other) { + if (this == &other) return *this; + has_error_ = other.has_error_; + data_ = std::move(other.data_); + items_ = std::move(other.items_); + // Reset the vector to make sure the invariants hold. + other.items_.clear(); + return *this; + } + + template + bool ProcessFormat(Consumer consumer) const { + const char* const base = data_.get(); + string_view text(base, 0); + for (const auto& item : items_) { + text = string_view(text.end(), (base + item.text_end) - text.end()); + if (item.is_conversion) { + if (!consumer.ConvertOne(item.conv, text)) return false; + } else { + if (!consumer.Append(text)) return false; + } + } + return !has_error_; + } + + bool has_error() const { return has_error_; } + + private: + // Returns whether the conversions match and if !allow_ignored it verifies + // that all conversions are used by the format. + bool MatchesConversions(bool allow_ignored, + std::initializer_list convs) const; + + struct ParsedFormatConsumer; + + struct ConversionItem { + bool is_conversion; + // Points to the past-the-end location of this element in the data_ array. + size_t text_end; + UnboundConversion conv; + }; + + bool has_error_; + std::unique_ptr data_; + std::vector items_; +}; + + +// A value type representing a preparsed format. These can be created, copied +// around, and reused to speed up formatting loops. +// The user must specify through the template arguments the conversion +// characters used in the format. This will be checked at compile time. +// +// This class uses Conv enum values to specify each argument. +// This allows for more flexibility as you can specify multiple possible +// conversion characters for each argument. +// ParsedFormat is a simplified alias for when the user only +// needs to specify a single conversion character for each argument. +// +// Example: +// // Extended format supports multiple characters per argument: +// using MyFormat = ExtendedParsedFormat; +// 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); +// +// This class also supports runtime format checking with the ::New() and +// ::NewAllowIgnored() factory functions. +// This is the only API that allows the user to pass a runtime specified format +// std::string. These factory functions will return NULL if the format does not match +// the conversions requested by the user. +template +class ExtendedParsedFormat : public str_format_internal::ParsedFormatBase { + public: + explicit ExtendedParsedFormat(string_view format) +#if ABSL_INTERNAL_ENABLE_FORMAT_CHECKER + __attribute__(( + enable_if(str_format_internal::EnsureConstexpr(format), + "Format std::string is not constexpr."), + enable_if(str_format_internal::ValidFormatImpl(format), + "Format specified does not match the template arguments."))) +#endif // ABSL_INTERNAL_ENABLE_FORMAT_CHECKER + : ExtendedParsedFormat(format, false) { + } + + // ExtendedParsedFormat factory function. + // The user still has to specify the conversion characters, but they will not + // be checked at compile time. Instead, it will be checked at runtime. + // This delays the checking to runtime, but allows the user to pass + // dynamically sourced formats. + // It returns NULL if the format does not match the conversion characters. + // The user is responsible for checking the return value before using it. + // + // The 'New' variant will check that all the specified arguments are being + // consumed by the format and return NULL if any argument is being ignored. + // The 'NewAllowIgnored' variant will not verify this and will allow formats + // that ignore arguments. + static std::unique_ptr New(string_view format) { + return New(format, false); + } + static std::unique_ptr NewAllowIgnored( + string_view format) { + return New(format, true); + } + + private: + static std::unique_ptr New(string_view format, + bool allow_ignored) { + std::unique_ptr conv( + new ExtendedParsedFormat(format, allow_ignored)); + if (conv->has_error()) return nullptr; + return conv; + } + + ExtendedParsedFormat(string_view s, bool allow_ignored) + : ParsedFormatBase(s, allow_ignored, {C...}) {} +}; +} // namespace str_format_internal +} // namespace absl + +#endif // ABSL_STRINGS_INTERNAL_STR_FORMAT_PARSER_H_ -- cgit v1.2.3