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+#ifndef ABSL_STRINGS_INTERNAL_STR_FORMAT_PARSER_H_
+#define ABSL_STRINGS_INTERNAL_STR_FORMAT_PARSER_H_
+
+#include <limits.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+#include <cassert>
+#include <initializer_list>
+#include <iosfwd>
+#include <iterator>
+#include <memory>
+#include <vector>
+
+#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 <typename Consumer>
+bool ParseFormatString(string_view src, Consumer consumer) {
+ int next_arg = 0;
+ while (!src.empty()) {
+ const char* percent =
+ static_cast<const char*>(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<Conv> 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 <typename Consumer>
+ 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<Conv> 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<char[]> data_;
+ std::vector<ConversionItem> 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<char...> 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<Conv::d | Conv::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);
+//
+// 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 <str_format_internal::Conv... C>
+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<C...>(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<ExtendedParsedFormat> New(string_view format) {
+ return New(format, false);
+ }
+ static std::unique_ptr<ExtendedParsedFormat> NewAllowIgnored(
+ string_view format) {
+ return New(format, true);
+ }
+
+ private:
+ static std::unique_ptr<ExtendedParsedFormat> New(string_view format,
+ bool allow_ignored) {
+ std::unique_ptr<ExtendedParsedFormat> 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_