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- /*
- * Copyright 2012-present Facebook, Inc.
- *
- * 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
- *
- * http://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.
- */
- #pragma once
- #define FOLLY_FORMAT_H_
- #include <cstdio>
- #include <stdexcept>
- #include <tuple>
- #include <type_traits>
- #include <folly/CPortability.h>
- #include <folly/Conv.h>
- #include <folly/FormatArg.h>
- #include <folly/Range.h>
- #include <folly/String.h>
- #include <folly/Traits.h>
- // Ignore shadowing warnings within this file, so includers can use -Wshadow.
- FOLLY_PUSH_WARNING
- FOLLY_GNU_DISABLE_WARNING("-Wshadow")
- namespace folly {
- // forward declarations
- template <bool containerMode, class... Args>
- class Formatter;
- template <class... Args>
- Formatter<false, Args...> format(StringPiece fmt, Args&&... args);
- template <class C>
- Formatter<true, C> vformat(StringPiece fmt, C&& container);
- template <class T, class Enable = void>
- class FormatValue;
- // meta-attribute to identify formatters in this sea of template weirdness
- namespace detail {
- class FormatterTag {};
- } // namespace detail
- /**
- * Formatter class.
- *
- * Note that this class is tricky, as it keeps *references* to its lvalue
- * arguments (while it takes ownership of the temporaries), and it doesn't
- * copy the passed-in format string. Thankfully, you can't use this
- * directly, you have to use format(...) below.
- */
- /* BaseFormatter class.
- * Overridable behaviours:
- * You may override the actual formatting of positional parameters in
- * `doFormatArg`. The Formatter class provides the default implementation.
- *
- * You may also override `doFormat` and `getSizeArg`. These override points were
- * added to permit static analysis of format strings, when it is inconvenient
- * or impossible to instantiate a BaseFormatter with the correct storage
- */
- template <class Derived, bool containerMode, class... Args>
- class BaseFormatter {
- public:
- /**
- * Append to output. out(StringPiece sp) may be called (more than once)
- */
- template <class Output>
- void operator()(Output& out) const;
- /**
- * Append to a string.
- */
- template <class Str>
- typename std::enable_if<IsSomeString<Str>::value>::type appendTo(
- Str& str) const {
- auto appender = [&str](StringPiece s) { str.append(s.data(), s.size()); };
- (*this)(appender);
- }
- /**
- * Conversion to string
- */
- std::string str() const {
- std::string s;
- appendTo(s);
- return s;
- }
- /**
- * Conversion to fbstring
- */
- fbstring fbstr() const {
- fbstring s;
- appendTo(s);
- return s;
- }
- /**
- * Metadata to identify generated children of BaseFormatter
- */
- typedef detail::FormatterTag IsFormatter;
- typedef BaseFormatter BaseType;
- private:
- typedef std::tuple<Args...> ValueTuple;
- static constexpr size_t valueCount = std::tuple_size<ValueTuple>::value;
- Derived const& asDerived() const {
- return *static_cast<const Derived*>(this);
- }
- template <size_t K, class Callback>
- typename std::enable_if<K == valueCount>::type
- doFormatFrom(size_t i, FormatArg& arg, Callback& /*cb*/) const {
- arg.error("argument index out of range, max=", i);
- }
- template <size_t K, class Callback>
- typename std::enable_if<(K < valueCount)>::type
- doFormatFrom(size_t i, FormatArg& arg, Callback& cb) const {
- if (i == K) {
- asDerived().template doFormatArg<K>(arg, cb);
- } else {
- doFormatFrom<K + 1>(i, arg, cb);
- }
- }
- template <class Callback>
- void doFormat(size_t i, FormatArg& arg, Callback& cb) const {
- return doFormatFrom<0>(i, arg, cb);
- }
- template <size_t K>
- typename std::enable_if<K == valueCount, int>::type getSizeArgFrom(
- size_t i,
- const FormatArg& arg) const {
- arg.error("argument index out of range, max=", i);
- }
- template <class T>
- typename std::enable_if<
- std::is_integral<T>::value && !std::is_same<T, bool>::value,
- int>::type
- getValue(const FormatValue<T>& format, const FormatArg&) const {
- return static_cast<int>(format.getValue());
- }
- template <class T>
- typename std::enable_if<
- !std::is_integral<T>::value || std::is_same<T, bool>::value,
- int>::type
- getValue(const FormatValue<T>&, const FormatArg& arg) const {
- arg.error("dynamic field width argument must be integral");
- }
- template <size_t K>
- typename std::enable_if <
- K<valueCount, int>::type getSizeArgFrom(size_t i, const FormatArg& arg)
- const {
- if (i == K) {
- return getValue(getFormatValue<K>(), arg);
- }
- return getSizeArgFrom<K + 1>(i, arg);
- }
- int getSizeArg(size_t i, const FormatArg& arg) const {
- return getSizeArgFrom<0>(i, arg);
- }
- StringPiece str_;
- protected:
- explicit BaseFormatter(StringPiece str, Args&&... args);
- // Not copyable
- BaseFormatter(const BaseFormatter&) = delete;
- BaseFormatter& operator=(const BaseFormatter&) = delete;
- // Movable, but the move constructor and assignment operator are private,
- // for the exclusive use of format() (below). This way, you can't create
- // a Formatter object, but can handle references to it (for streaming,
- // conversion to string, etc) -- which is good, as Formatter objects are
- // dangerous (they may hold references).
- BaseFormatter(BaseFormatter&&) = default;
- BaseFormatter& operator=(BaseFormatter&&) = default;
- template <size_t K>
- using ArgType = typename std::tuple_element<K, ValueTuple>::type;
- template <size_t K>
- FormatValue<typename std::decay<ArgType<K>>::type> getFormatValue() const {
- return FormatValue<typename std::decay<ArgType<K>>::type>(
- std::get<K>(values_));
- }
- ValueTuple values_;
- };
- template <bool containerMode, class... Args>
- class Formatter : public BaseFormatter<
- Formatter<containerMode, Args...>,
- containerMode,
- Args...> {
- private:
- explicit Formatter(StringPiece& str, Args&&... args)
- : BaseFormatter<
- Formatter<containerMode, Args...>,
- containerMode,
- Args...>(str, std::forward<Args>(args)...) {
- static_assert(
- !containerMode || sizeof...(Args) == 1,
- "Exactly one argument required in container mode");
- }
- template <size_t K, class Callback>
- void doFormatArg(FormatArg& arg, Callback& cb) const {
- this->template getFormatValue<K>().format(arg, cb);
- }
- friend class BaseFormatter<
- Formatter<containerMode, Args...>,
- containerMode,
- Args...>;
- template <class... A>
- friend Formatter<false, A...> format(StringPiece fmt, A&&... arg);
- template <class C>
- friend Formatter<true, C> vformat(StringPiece fmt, C&& container);
- };
- /**
- * Formatter objects can be written to streams.
- */
- template <bool containerMode, class... Args>
- std::ostream& operator<<(
- std::ostream& out,
- const Formatter<containerMode, Args...>& formatter) {
- auto writer = [&out](StringPiece sp) {
- out.write(sp.data(), std::streamsize(sp.size()));
- };
- formatter(writer);
- return out;
- }
- /**
- * Formatter objects can be written to stdio FILEs.
- */
- template <class Derived, bool containerMode, class... Args>
- void writeTo(
- FILE* fp,
- const BaseFormatter<Derived, containerMode, Args...>& formatter);
- /**
- * Create a formatter object.
- *
- * std::string formatted = format("{} {}", 23, 42).str();
- * LOG(INFO) << format("{} {}", 23, 42);
- * writeTo(stdout, format("{} {}", 23, 42));
- */
- template <class... Args>
- Formatter<false, Args...> format(StringPiece fmt, Args&&... args) {
- return Formatter<false, Args...>(fmt, std::forward<Args>(args)...);
- }
- /**
- * Like format(), but immediately returns the formatted string instead of an
- * intermediate format object.
- */
- template <class... Args>
- inline std::string sformat(StringPiece fmt, Args&&... args) {
- return format(fmt, std::forward<Args>(args)...).str();
- }
- /**
- * Create a formatter object that takes one argument (of container type)
- * and uses that container to get argument values from.
- *
- * std::map<string, string> map { {"hello", "world"}, {"answer", "42"} };
- *
- * The following are equivalent:
- * format("{0[hello]} {0[answer]}", map);
- *
- * vformat("{hello} {answer}", map);
- *
- * but the latter is cleaner.
- */
- template <class Container>
- Formatter<true, Container> vformat(StringPiece fmt, Container&& container) {
- return Formatter<true, Container>(fmt, std::forward<Container>(container));
- }
- /**
- * Like vformat(), but immediately returns the formatted string instead of an
- * intermediate format object.
- */
- template <class Container>
- inline std::string svformat(StringPiece fmt, Container&& container) {
- return vformat(fmt, std::forward<Container>(container)).str();
- }
- /**
- * Exception class thrown when a format key is not found in the given
- * associative container keyed by strings. We inherit std::out_of_range for
- * compatibility with callers that expect exception to be thrown directly
- * by std::map or std::unordered_map.
- *
- * Having the key be at the end of the message string, we can access it by
- * simply adding its offset to what(). Not storing separate std::string key
- * makes the exception type small and noexcept-copyable like std::out_of_range,
- * and therefore able to fit in-situ in exception_wrapper.
- */
- class FOLLY_EXPORT FormatKeyNotFoundException : public std::out_of_range {
- public:
- explicit FormatKeyNotFoundException(StringPiece key);
- char const* key() const noexcept {
- return what() + kMessagePrefix.size();
- }
- private:
- static constexpr StringPiece const kMessagePrefix = "format key not found: ";
- };
- /**
- * Wrap a sequence or associative container so that out-of-range lookups
- * return a default value rather than throwing an exception.
- *
- * Usage:
- * format("[no_such_key"], defaulted(map, 42)) -> 42
- */
- namespace detail {
- template <class Container, class Value>
- struct DefaultValueWrapper {
- DefaultValueWrapper(const Container& container, const Value& defaultValue)
- : container(container), defaultValue(defaultValue) {}
- const Container& container;
- const Value& defaultValue;
- };
- } // namespace detail
- template <class Container, class Value>
- detail::DefaultValueWrapper<Container, Value> defaulted(
- const Container& c,
- const Value& v) {
- return detail::DefaultValueWrapper<Container, Value>(c, v);
- }
- /**
- * Append formatted output to a string.
- *
- * std::string foo;
- * format(&foo, "{} {}", 42, 23);
- *
- * Shortcut for toAppend(format(...), &foo);
- */
- template <class Str, class... Args>
- typename std::enable_if<IsSomeString<Str>::value>::type
- format(Str* out, StringPiece fmt, Args&&... args) {
- format(fmt, std::forward<Args>(args)...).appendTo(*out);
- }
- /**
- * Append vformatted output to a string.
- */
- template <class Str, class Container>
- typename std::enable_if<IsSomeString<Str>::value>::type
- vformat(Str* out, StringPiece fmt, Container&& container) {
- vformat(fmt, std::forward<Container>(container)).appendTo(*out);
- }
- /**
- * Utilities for all format value specializations.
- */
- namespace format_value {
- /**
- * Format a string in "val", obeying appropriate alignment, padding, width,
- * and precision. Treats Align::DEFAULT as Align::LEFT, and
- * Align::PAD_AFTER_SIGN as Align::RIGHT; use formatNumber for
- * number-specific formatting.
- */
- template <class FormatCallback>
- void formatString(StringPiece val, FormatArg& arg, FormatCallback& cb);
- /**
- * Format a number in "val"; the first prefixLen characters form the prefix
- * (sign, "0x" base prefix, etc) which must be left-aligned if the alignment
- * is Align::PAD_AFTER_SIGN. Treats Align::DEFAULT as Align::LEFT. Ignores
- * arg.precision, as that has a different meaning for numbers (not "maximum
- * field width")
- */
- template <class FormatCallback>
- void formatNumber(
- StringPiece val,
- int prefixLen,
- FormatArg& arg,
- FormatCallback& cb);
- /**
- * Format a Formatter object recursively. Behaves just like
- * formatString(fmt.str(), arg, cb); but avoids creating a temporary
- * string if possible.
- */
- template <
- class FormatCallback,
- class Derived,
- bool containerMode,
- class... Args>
- void formatFormatter(
- const BaseFormatter<Derived, containerMode, Args...>& formatter,
- FormatArg& arg,
- FormatCallback& cb);
- } // namespace format_value
- /*
- * Specialize folly::FormatValue for your type.
- *
- * FormatValue<T> is constructed with a (reference-collapsed) T&&, which is
- * guaranteed to stay alive until the FormatValue object is destroyed, so you
- * may keep a reference (or pointer) to it instead of making a copy.
- *
- * You must define
- * template <class Callback>
- * void format(FormatArg& arg, Callback& cb) const;
- * with the following semantics: format the value using the given argument.
- *
- * arg is given by non-const reference for convenience -- it won't be reused,
- * so feel free to modify it in place if necessary. (For example, wrap an
- * existing conversion but change the default, or remove the "key" when
- * extracting an element from a container)
- *
- * Call the callback to append data to the output. You may call the callback
- * as many times as you'd like (or not at all, if you want to output an
- * empty string)
- */
- namespace detail {
- template <class T, class Enable = void>
- struct IsFormatter : public std::false_type {};
- template <class T>
- struct IsFormatter<
- T,
- typename std::enable_if<
- std::is_same<typename T::IsFormatter, detail::FormatterTag>::value>::
- type> : public std::true_type {};
- } // namespace detail
- // Deprecated API. formatChecked() et. al. now behave identically to their
- // non-Checked counterparts.
- template <class... Args>
- Formatter<false, Args...> formatChecked(StringPiece fmt, Args&&... args) {
- return format(fmt, std::forward<Args>(args)...);
- }
- template <class... Args>
- inline std::string sformatChecked(StringPiece fmt, Args&&... args) {
- return formatChecked(fmt, std::forward<Args>(args)...).str();
- }
- template <class Container>
- Formatter<true, Container> vformatChecked(
- StringPiece fmt,
- Container&& container) {
- return vformat(fmt, std::forward<Container>(container));
- }
- template <class Container>
- inline std::string svformatChecked(StringPiece fmt, Container&& container) {
- return vformatChecked(fmt, std::forward<Container>(container)).str();
- }
- template <class Str, class... Args>
- typename std::enable_if<IsSomeString<Str>::value>::type
- formatChecked(Str* out, StringPiece fmt, Args&&... args) {
- formatChecked(fmt, std::forward<Args>(args)...).appendTo(*out);
- }
- template <class Str, class Container>
- typename std::enable_if<IsSomeString<Str>::value>::type
- vformatChecked(Str* out, StringPiece fmt, Container&& container) {
- vformatChecked(fmt, std::forward<Container>(container)).appendTo(*out);
- }
- } // namespace folly
- #include <folly/Format-inl.h>
- FOLLY_POP_WARNING
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