folly-clib-20250713.1537: folly/folly/Conv.h
/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*
* 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.
*/
//
// Docs: https://fburl.com/fbcref_conv
//
/**
* Conv provides the ubiquitous method `to<TargetType>(source)`, along with
* a few other generic interfaces for converting objects to and from
* string-like types (std::string, fbstring, StringPiece), as well as
* range-checked conversions between numeric and enum types. The mechanisms are
* extensible, so that user-specified types can add folly::to support.
*
* folly::to<std::string>(123)
* // "123"
*
*******************************************************************************
* ## TYPE -> STRING CONVERSIONS
*******************************************************************************
* You can call the `to<std::string>` or `to<fbstring>`. These are variadic
* functions that convert their arguments to strings, and concatenate them to
* form a result. So, for example,
*
* auto str = to<std::string>(123, "456", 789);
*
* Sets str to `"123456789"`.
*
* In addition to just concatenating the arguments, related functions can
* delimit them with some string: `toDelim<std::string>(",", "123", 456, "789")`
* will return the string `"123,456,789"`.
*
* toAppend does not return a string; instead, it takes a pointer to a string as
* its last argument, and appends the result of the concatenation into it:
* std::string str = "123";
* toAppend(456, "789", &str); // Now str is "123456789".
*
* The toAppendFit function acts like toAppend, but it precalculates the size
* required to perform the append operation, and reserves that space in the
* output string before actually inserting its arguments. This can sometimes
* save on string expansion, but beware: appending to the same string many times
* with toAppendFit is likely a pessimization, since it will resize the string
* once per append.
*
* The combination of the append and delim variants also exist: toAppendDelim
* and toAppendDelimFit are defined, with the obvious semantics.
*
*******************************************************************************
* ## STRING -> TYPE CONVERSIONS
*******************************************************************************
* Going in the other direction, and parsing a string into a C++ type, is also
* supported:
* to<int>("123"); // Returns 123.
*
* Out of range (e.g. `to<std::uint8_t>("1000")`), or invalidly formatted (e.g.
* `to<int>("four")`) inputs will throw. If throw-on-error is undesirable (for
* instance: you're dealing with untrusted input, and want to protect yourself
* from users sending you down a very slow exception-throwing path), you can use
* `tryTo<T>`, which will return an `Expected<T, ConversionCode>`.
*
* There are overloads of to() and tryTo() that take a `StringPiece*`. These
* parse out a type from the beginning of a string, and modify the passed-in
* StringPiece to indicate the portion of the string not consumed.
*
*******************************************************************************
* ## NUMERIC / ENUM CONVERSIONS
*******************************************************************************
* Conv also supports a `to<T>(S)` overload, where T and S are numeric or enum
* types, that checks to see that the target type can represent its argument,
* and will throw if it cannot. This includes cases where a floating point to
* integral conversion is attempted on a value with a non-zero fractional
* component, and integral to floating point conversions that would lose
* precision. Enum conversions are range-checked for the underlying type of the
* enum, but there is no check that the input value is a valid choice of enum
* value.
*
*******************************************************************************
* ## CUSTOM TYPE CONVERSIONS
*******************************************************************************
* Users may customize the string conversion functionality for their own data
* types. The key functions you should implement are:
* // Two functions to allow conversion to your type from a string.
* Expected<StringPiece, ConversionCode> parseTo(folly::StringPiece in,
* YourType& out);
* YourErrorType makeConversionError(YourErrorType in, StringPiece in);
* // Two functions to allow conversion from your type to a string.
* template <class String>
* void toAppend(const YourType& in, String* out);
* size_t estimateSpaceNeeded(const YourType& in);
*
* These are documented below, inline.
*
* @file Conv.h
*/
#pragma once
#include <algorithm>
#include <cassert>
#include <cctype>
#include <climits>
#include <cmath>
#include <cstddef>
#include <limits>
#include <optional>
#include <stdexcept>
#include <string>
#include <system_error>
#include <tuple>
#include <type_traits>
#include <utility>
#if __has_include(<charconv>)
#include <charconv>
#endif
#include <double-conversion/double-conversion.h> // V8 JavaScript implementation
#include <folly/CPortability.h>
#include <folly/Demangle.h>
#include <folly/Expected.h>
#include <folly/FBString.h>
#include <folly/Likely.h>
#include <folly/Portability.h>
#include <folly/Range.h>
#include <folly/Traits.h>
#include <folly/Unit.h>
#include <folly/Utility.h>
#include <folly/lang/Exception.h>
#include <folly/lang/Pretty.h>
#include <folly/lang/ToAscii.h>
#include <folly/portability/Math.h>
namespace folly {
// Keep this in sync with kErrorStrings in Conv.cpp
enum class ConversionCode : unsigned char {
SUCCESS,
EMPTY_INPUT_STRING,
NO_DIGITS,
BOOL_OVERFLOW,
BOOL_INVALID_VALUE,
NON_DIGIT_CHAR,
INVALID_LEADING_CHAR,
POSITIVE_OVERFLOW,
NEGATIVE_OVERFLOW,
STRING_TO_FLOAT_ERROR,
NON_WHITESPACE_AFTER_END,
ARITH_POSITIVE_OVERFLOW,
ARITH_NEGATIVE_OVERFLOW,
ARITH_LOSS_OF_PRECISION,
SPLIT_ERROR,
CUSTOM,
NUM_ERROR_CODES, // has to be the last entry
};
struct FOLLY_EXPORT ConversionErrorBase : std::range_error {
using std::range_error::range_error;
};
class FOLLY_EXPORT ConversionError : public ConversionErrorBase {
public:
ConversionError(const std::string& str, ConversionCode code)
: ConversionErrorBase(str), code_(code) {}
ConversionError(const char* str, ConversionCode code)
: ConversionErrorBase(str), code_(code) {}
ConversionCode errorCode() const { return code_; }
private:
ConversionCode code_;
};
/**
* Custom Error Translation
*
* Your overloaded parseTo() function can return a custom error code on failure.
* ::folly::to() will call makeConversionError to translate that error code into
* an object to throw. makeConversionError is found by argument-dependent
* lookup. It should have this signature:
*
* namespace other_namespace {
* enum YourErrorCode { BAD_ERROR, WORSE_ERROR };
*
* struct YourConversionError : ConversionErrorBase {
* YourConversionError(const char* what) : ConversionErrorBase(what) {}
* };
*
* YourConversionError
* makeConversionError(YourErrorCode code, ::folly::StringPiece sp) {
* ...
* return YourConversionError(messageString);
* }
*/
ConversionError makeConversionError(ConversionCode code, StringPiece input);
namespace detail {
/**
* Enforce that the suffix following a number is made up only of whitespace.
*/
inline ConversionCode enforceWhitespaceErr(StringPiece sp) {
for (auto c : sp) {
if (FOLLY_UNLIKELY(!std::isspace(c))) {
return ConversionCode::NON_WHITESPACE_AFTER_END;
}
}
return ConversionCode::SUCCESS;
}
/**
* Keep this implementation around for prettyToDouble().
*/
inline void enforceWhitespace(StringPiece sp) {
auto err = enforceWhitespaceErr(sp);
if (err != ConversionCode::SUCCESS) {
throw_exception(makeConversionError(err, sp));
}
}
} // namespace detail
/**
* @overloadbrief to, but return an Expected
*
* The identity conversion function.
* tryTo<T>(T) returns itself for all types T.
*/
template <class Tgt, class Src>
typename std::enable_if<
std::is_same<Tgt, typename std::decay<Src>::type>::value,
Expected<Tgt, ConversionCode>>::type
tryTo(Src&& value) noexcept {
return static_cast<Src&&>(value);
}
/**
* @overloadbrief Convert from one type to another.
*/
template <class Tgt, class Src>
typename std::enable_if<
std::is_same<Tgt, typename std::decay<Src>::type>::value,
Tgt>::type
to(Src&& value) {
return static_cast<Src&&>(value);
}
/**
* Arithmetic to boolean
*/
/**
* Unchecked conversion from arithmetic to boolean. This is different from the
* other arithmetic conversions because we use the C convention of treating any
* non-zero value as true, instead of range checking.
*/
template <class Tgt, class Src>
typename std::enable_if<
is_arithmetic_v<Src> && !std::is_same<Tgt, Src>::value &&
std::is_same<Tgt, bool>::value,
Expected<Tgt, ConversionCode>>::type
tryTo(const Src& value) noexcept {
return value != Src();
}
template <class Tgt, class Src>
typename std::enable_if<
is_arithmetic_v<Src> && !std::is_same<Tgt, Src>::value &&
std::is_same<Tgt, bool>::value,
Tgt>::type
to(const Src& value) {
return value != Src();
}
/**
* Anything to string
*/
namespace detail {
template <class... T>
using LastElement = type_pack_element_t<sizeof...(T) - 1, T...>;
#ifdef _MSC_VER
// MSVC can't quite figure out the LastElementImpl::call() stuff
// in the base implementation, so we have to use tuples instead,
// which result in significantly more templates being compiled,
// though the runtime performance is the same.
template <typename... Ts, typename R = LastElement<Ts...>>
const R& getLastElement(const Ts&... ts) {
return std::get<sizeof...(Ts) - 1>(std::forward_as_tuple(ts...));
}
inline void getLastElement() {}
#else
template <typename...>
struct LastElementImpl;
template <>
struct LastElementImpl<> {
static void call() {}
};
template <typename Ign, typename... Igns>
struct LastElementImpl<Ign, Igns...> {
template <typename Last>
static const Last& call(Igns..., const Last& last) {
return last;
}
};
template <typename... Ts, typename R = LastElement<Ts...>>
const R& getLastElement(const Ts&... ts) {
return LastElementImpl<Ignored<Ts>...>::call(ts...);
}
#endif
} // namespace detail
/**
* Conversions from integral types to string types.
*/
#if FOLLY_HAVE_INT128_T
namespace detail {
template <typename IntegerType>
constexpr unsigned int digitsEnough() {
// digits10 returns the number of decimal digits that this type can represent,
// not the number of characters required for the max value, so we need to add
// one. ex: char digits10 returns 2, because 256-999 cannot be represented,
// but we need 3.
auto const digits10 = std::numeric_limits<IntegerType>::digits10;
return static_cast<unsigned int>(digits10) + 1;
}
inline size_t unsafeTelescope128(char* outb, char* oute, unsigned __int128 x) {
using Usrc = unsigned __int128;
// Decompose the input into at most 3 components using the largest power-of-10
// base that fits in a 64-bit unsigned integer, and then convert the
// components using 64-bit arithmetic and concatenate them.
constexpr static auto kBase = UINT64_C(10'000'000'000'000'000'000);
constexpr static size_t kBaseDigits = 19;
size_t p = 0;
const auto leading = [&](Usrc v) {
assert(v >> 64 == 0);
p = detail::to_ascii_with_route<10, to_ascii_alphabet_lower>(
outb, oute, static_cast<uint64_t>(v));
};
const auto append = [&](uint64_t v) {
assert(v < kBase);
assert(outb + p + kBaseDigits <= oute);
auto v64 = static_cast<uint64_t>(v);
detail::to_ascii_with_route<10, to_ascii_alphabet_lower>(
outb + p, kBaseDigits, v64);
p += kBaseDigits;
};
if (x >> 64 > 0) {
const auto rem = static_cast<uint64_t>(x % kBase);
x /= kBase;
if (x >> 64 > 0) {
const auto rem2 = static_cast<uint64_t>(x % kBase);
x /= kBase;
leading(x);
append(rem2);
append(rem);
return p;
}
leading(x);
append(rem);
return p;
}
leading(x);
return p;
}
} // namespace detail
#endif
/**
* @overloadbrief Appends conversion to string.
*
* A single char gets appended.
*/
template <class Tgt>
void toAppend(char value, Tgt* result) {
*result += value;
}
/**
* @overloadbrief Estimates the number of characters in a value's string
* representation.
*/
template <class T>
constexpr typename std::enable_if<std::is_same<T, char>::value, size_t>::type
estimateSpaceNeeded(T) {
return 1;
}
template <size_t N>
constexpr size_t estimateSpaceNeeded(const char (&)[N]) {
return N;
}
/**
* Everything implicitly convertible to const char* gets appended.
*/
template <class Tgt, class Src>
typename std::enable_if<
std::is_convertible<Src, const char*>::value &&
IsSomeString<Tgt>::value>::type
toAppend(Src value, Tgt* result) {
// Treat null pointers like an empty string, as in:
// operator<<(std::ostream&, const char*).
const char* c = value;
if (c) {
result->append(value);
}
}
template <class Src>
typename std::enable_if<std::is_convertible<Src, const char*>::value, size_t>::
type
estimateSpaceNeeded(Src value) {
const char* c = value;
return c ? std::strlen(c) : 0;
}
template <class Src>
typename std::enable_if<IsSomeString<Src>::value, size_t>::type
estimateSpaceNeeded(Src const& value) {
return value.size();
}
template <class Src>
typename std::enable_if<
std::is_convertible<Src, folly::StringPiece>::value &&
!IsSomeString<Src>::value &&
!std::is_convertible<Src, const char*>::value,
size_t>::type
estimateSpaceNeeded(Src value) {
return folly::StringPiece(value).size();
}
template <>
inline size_t estimateSpaceNeeded(std::nullptr_t /* value */) {
return 0;
}
template <class Src>
typename std::enable_if<
std::is_pointer<Src>::value &&
IsSomeString<std::remove_pointer<Src>>::value,
size_t>::type
estimateSpaceNeeded(Src value) {
return value->size();
}
/**
* Strings get appended, too.
*/
template <class Tgt, class Src>
typename std::enable_if<
IsSomeString<Src>::value && IsSomeString<Tgt>::value>::type
toAppend(const Src& value, Tgt* result) {
result->append(value);
}
/**
* and StringPiece objects too
*/
template <class Tgt>
typename std::enable_if<IsSomeString<Tgt>::value>::type toAppend(
StringPiece value, Tgt* result) {
result->append(value.data(), value.size());
}
/**
* There's no implicit conversion from fbstring to other string types,
* so make a specialization.
*/
template <class Tgt>
typename std::enable_if<IsSomeString<Tgt>::value>::type toAppend(
const fbstring& value, Tgt* result) {
result->append(value.data(), value.size());
}
#if FOLLY_HAVE_INT128_T
/**
* Special handling for 128 bit integers.
*/
template <class Tgt>
void toAppend(__int128 value, Tgt* result) {
typedef unsigned __int128 Usrc;
char buffer[detail::digitsEnough<unsigned __int128>() + 1];
const auto oute = buffer + sizeof(buffer);
size_t p;
if (value < 0) {
buffer[0] = '-';
p = 1 + detail::unsafeTelescope128(buffer + 1, oute, -Usrc(value));
} else {
p = detail::unsafeTelescope128(buffer, oute, value);
}
result->append(buffer, p);
}
template <class Tgt>
void toAppend(unsigned __int128 value, Tgt* result) {
char buffer[detail::digitsEnough<unsigned __int128>()];
size_t p = detail::unsafeTelescope128(buffer, buffer + sizeof(buffer), value);
result->append(buffer, p);
}
template <class T>
constexpr
typename std::enable_if<std::is_same<T, __int128>::value, size_t>::type
estimateSpaceNeeded(T) {
return detail::digitsEnough<__int128>();
}
template <class T>
constexpr typename std::
enable_if<std::is_same<T, unsigned __int128>::value, size_t>::type
estimateSpaceNeeded(T) {
return detail::digitsEnough<unsigned __int128>();
}
#endif
/**
* int32_t and int64_t to string (by appending) go through here. The
* result is APPENDED to a preexisting string passed as the second
* parameter. This should be efficient with fbstring because fbstring
* incurs no dynamic allocation below 23 bytes and no number has more
* than 22 bytes in its textual representation (20 for digits, one for
* sign, one for the terminating 0).
*/
template <class Tgt, class Src>
typename std::enable_if<
is_integral_v<Src> && is_signed_v<Src> && IsSomeString<Tgt>::value &&
sizeof(Src) >= 4>::type
toAppend(Src value, Tgt* result) {
char buffer[to_ascii_size_max_decimal<uint64_t>];
auto uvalue = value < 0
? ~static_cast<uint64_t>(value) + 1
: static_cast<uint64_t>(value);
if (value < 0) {
result->push_back('-');
}
result->append(buffer, to_ascii_decimal(buffer, uvalue));
}
template <class Src>
typename std::enable_if<
is_integral_v<Src> && is_signed_v<Src> && sizeof(Src) >= 4 &&
sizeof(Src) < 16,
size_t>::type
estimateSpaceNeeded(Src value) {
auto uvalue = value < 0
? ~static_cast<uint64_t>(value) + 1
: static_cast<uint64_t>(value);
return size_t(value < 0) + to_ascii_size_decimal(uvalue);
}
/**
* As above, but for uint32_t and uint64_t.
*/
template <class Tgt, class Src>
typename std::enable_if<
is_integral_v<Src> && !is_signed_v<Src> && IsSomeString<Tgt>::value &&
sizeof(Src) >= 4>::type
toAppend(Src value, Tgt* result) {
char buffer[to_ascii_size_max_decimal<uint64_t>];
result->append(buffer, to_ascii_decimal(buffer, value));
}
template <class Src>
typename std::enable_if<
is_integral_v<Src> && !is_signed_v<Src> && sizeof(Src) >= 4 &&
sizeof(Src) < 16,
size_t>::type
estimateSpaceNeeded(Src value) {
return to_ascii_size_decimal(value);
}
/**
* All small signed and unsigned integers to string go through 32-bit
* types int32_t and uint32_t, respectively.
*/
template <class Tgt, class Src>
typename std::enable_if<
is_integral_v<Src> && IsSomeString<Tgt>::value && sizeof(Src) < 4>::type
toAppend(Src value, Tgt* result) {
typedef typename std::conditional<is_signed_v<Src>, int64_t, uint64_t>::type
Intermediate;
toAppend<Tgt>(static_cast<Intermediate>(value), result);
}
template <class Src>
typename std::enable_if<
is_integral_v<Src> && sizeof(Src) < 4 && !std::is_same<Src, char>::value,
size_t>::type
estimateSpaceNeeded(Src value) {
typedef typename std::conditional<is_signed_v<Src>, int64_t, uint64_t>::type
Intermediate;
return estimateSpaceNeeded(static_cast<Intermediate>(value));
}
/**
* Enumerated values get appended as integers.
*/
template <class Tgt, class Src>
typename std::enable_if<
std::is_enum<Src>::value && IsSomeString<Tgt>::value>::type
toAppend(Src value, Tgt* result) {
toAppend(to_underlying(value), result);
}
template <class Src>
typename std::enable_if<std::is_enum<Src>::value, size_t>::type
estimateSpaceNeeded(Src value) {
return estimateSpaceNeeded(to_underlying(value));
}
/**
* Conversions from floating-point types to string types.
*/
/// Operating mode for the floating point type version of
/// `folly::ToAppend`. This is modeled after
/// `double_conversion::DoubleToStringConverter::DtoaMode`.
/// Dtoa is an acryonym for Double to ASCII.
enum class DtoaMode {
/// Outputs the shortest representation of a `double`.
/// The output is either in decimal or exponential notation; which ever is
/// shortest.
SHORTEST,
/// Outputs the shortest representation of a `float`.
/// This outputs in either decimal or exponential notation, which ever is
/// shortest.
SHORTEST_SINGLE,
/// Outputs fixed precision after the decimal point. Similar to
/// `printf`'s %f.
/// The output is in decimal notation.
/// Use the `numDigits` parameter to specify the precision.
FIXED,
/// Outputs with a precision that is independent of the decimal point.
/// The outputs is either decimal or exponential notation, depending on the
/// value and the precision.
/// Similar to `printf`'s %g formating.
/// Use the `numDigits` parameter to specify the precision.
PRECISION,
};
/// Flags for the floating point type version of `folly::ToAppend`.
/// This is modeled after `double_conversion::DoubleToStringConverter::Flags`.
/// Dtoa is an acryonym for Double to ASCII.
/// This enum is used to store bit wise flags, so a variable of this type may be
/// a bitwise combination of these definitions.
enum class DtoaFlags {
NO_FLAGS = 0,
/// Emits a plus sign for positive exponents. e.g., 1.2e+3
EMIT_POSITIVE_EXPONENT_SIGN = 1,
/// Emits a trailing decimal point. e.g., 123.
EMIT_TRAILING_DECIMAL_POINT = 2,
/// Emits a trailing decimal point. e.g., 123.0
/// Requires `EMIT_TRAILING_DECIMAL_POINT` to be set.
EMIT_TRAILING_ZERO_AFTER_POINT = 4,
/// -0.0 outputs as 0.0
UNIQUE_ZERO = 8,
/// Trailing zeros are removed from the fractional portion
/// of the result in precision mode. Matches `printf`'s %g.
/// When `EMIT_TRAILING_ZERO_AFTER_POINT` is also given, one trailing zero is
/// preserved.
NO_TRAILING_ZERO = 16,
};
constexpr DtoaFlags operator|(DtoaFlags a, DtoaFlags b) {
return static_cast<DtoaFlags>(to_underlying(a) | to_underlying(b));
}
constexpr DtoaFlags operator&(DtoaFlags a, DtoaFlags b) {
return static_cast<DtoaFlags>(to_underlying(a) & to_underlying(b));
}
namespace detail {
constexpr int kConvMaxDecimalInShortestLow = -6;
/// 10^kConvMaxDecimalInShortestLow. Replace with constexpr std::pow in C++26.
constexpr double kConvMaxDecimalInShortestLowValue = 0.000001;
constexpr int kConvMaxDecimalInShortestHigh = 21;
/// 10^kConvMaxDecimalInShortestHigh. Replace with constexpr std::pow in C++26.
constexpr double kConvMaxDecimalInShortestHighValue =
1'000'000'000'000'000'000'000.0;
constexpr int kBase10MaximalLength = 17;
constexpr int kConvMaxFixedDigitsAfterPoint =
double_conversion::DoubleToStringConverter::kMaxFixedDigitsAfterPoint;
constexpr int kConvMaxPrecisionDigits =
double_conversion::DoubleToStringConverter::kMaxPrecisionDigits;
/// Converts `DtoaMode` to
/// `double_conversion::DoubleToStringConverter::DtoaMode`.
/// This is temporary until
/// `double_conversion::DoubleToStringConverter::DtoaMode` is removed.
constexpr double_conversion::DoubleToStringConverter::DtoaMode convert(
DtoaMode mode) {
switch (mode) {
case DtoaMode::SHORTEST:
return double_conversion::DoubleToStringConverter::SHORTEST;
case DtoaMode::SHORTEST_SINGLE:
return double_conversion::DoubleToStringConverter::SHORTEST_SINGLE;
case DtoaMode::FIXED:
return double_conversion::DoubleToStringConverter::FIXED;
case DtoaMode::PRECISION:
return double_conversion::DoubleToStringConverter::PRECISION;
default: /* unexpected */
assert(false);
// Default to PRECISION per exising behavior.
return double_conversion::DoubleToStringConverter::PRECISION;
}
}
/// Converts `DtoaFlags` to
/// `double_conversion::DoubleToStringConverter::DtoaFlags`.
/// This is temporary until
/// `double_conversion::DoubleToStringConverter::DtoaFlags` is removed.
constexpr double_conversion::DoubleToStringConverter::Flags convert(
DtoaFlags flags) {
return static_cast<double_conversion::DoubleToStringConverter::Flags>(flags);
}
} // namespace detail
/**
* `numDigits` is only used with `FIXED` && `PRECISION`.
*/
template <class Tgt, class Src>
typename std::enable_if<
std::is_floating_point<Src>::value && IsSomeString<Tgt>::value>::type
toAppend(
Src value,
Tgt* result,
DtoaMode mode,
unsigned int numDigits,
DtoaFlags flags = DtoaFlags::NO_FLAGS) {
double_conversion::DoubleToStringConverter::Flags dcFlags =
detail::convert(flags);
double_conversion::DoubleToStringConverter conv(
dcFlags,
"Infinity",
"NaN",
'E',
detail::kConvMaxDecimalInShortestLow,
detail::kConvMaxDecimalInShortestHigh,
6, // max leading padding zeros
1); // max trailing padding zeros
char buffer[256];
double_conversion::StringBuilder builder(buffer, sizeof(buffer));
double_conversion::DoubleToStringConverter::DtoaMode dcMode =
detail::convert(mode);
FOLLY_PUSH_WARNING
FOLLY_CLANG_DISABLE_WARNING("-Wcovered-switch-default")
switch (dcMode) {
case double_conversion::DoubleToStringConverter::SHORTEST:
conv.ToShortest(value, &builder);
break;
case double_conversion::DoubleToStringConverter::SHORTEST_SINGLE:
conv.ToShortestSingle(static_cast<float>(value), &builder);
break;
case double_conversion::DoubleToStringConverter::FIXED:
conv.ToFixed(value, int(numDigits), &builder);
break;
case double_conversion::DoubleToStringConverter::PRECISION:
default:
assert(dcMode == double_conversion::DoubleToStringConverter::PRECISION);
conv.ToPrecision(value, int(numDigits), &builder);
break;
}
FOLLY_POP_WARNING
const size_t length = size_t(builder.position());
builder.Finalize();
result->append(buffer, length);
}
/**
* As above, but for floating point
*/
template <class Tgt, class Src>
typename std::enable_if<
std::is_floating_point<Src>::value && IsSomeString<Tgt>::value>::type
toAppend(Src value, Tgt* result) {
toAppend(value, result, DtoaMode::SHORTEST, 0);
}
/**
* Upper bound of the length of the output from
* DoubleToStringConverter::ToShortest(double, StringBuilder*),
* as used in toAppend(double, string*).
*/
template <class Src>
typename std::enable_if<std::is_floating_point<Src>::value, size_t>::type
estimateSpaceNeeded(Src value) {
// kBase10MaximalLength is 17. We add 1 for decimal point,
// e.g. 10.0/9 is 17 digits and 18 characters, including the decimal point.
constexpr int kMaxMantissaSpace = detail::kBase10MaximalLength + 1;
// strlen("E-") + digits10(numeric_limits<double>::max_exponent10)
constexpr int kMaxExponentSpace = 2 + 3;
static const int kMaxPositiveSpace = std::max({
// E.g. 1.1111111111111111E-100.
kMaxMantissaSpace + kMaxExponentSpace,
// E.g. 0.000001.1111111111111111, if kConvMaxDecimalInShortestLow is -6.
kMaxMantissaSpace - detail::kConvMaxDecimalInShortestLow,
// If kConvMaxDecimalInShortestHigh is 21, then 1e21 is the smallest
// number > 1 which ToShortest outputs in exponential notation,
// so 21 is the longest non-exponential number > 1.
detail::kConvMaxDecimalInShortestHigh,
});
return size_t(
kMaxPositiveSpace +
(value < 0 ? 1 : 0)); // +1 for minus sign, if negative
}
template <class Src>
constexpr typename std::enable_if<
!std::is_fundamental<Src>::value &&
#if FOLLY_HAVE_INT128_T
// On OSX 10.10, is_fundamental<__int128> is false :-O
!std::is_same<__int128, Src>::value &&
!std::is_same<unsigned __int128, Src>::value &&
#endif
!IsSomeString<Src>::value &&
!std::is_convertible<Src, const char*>::value &&
!std::is_convertible<Src, StringPiece>::value &&
!std::is_enum<Src>::value,
size_t>::type
estimateSpaceNeeded(const Src&) {
return sizeof(Src) + 1; // dumbest best effort ever?
}
#ifndef DOXYGEN_SHOULD_SKIP_THIS
namespace detail {
template <typename>
struct EstimateSpaceToReserveAll;
template <size_t... I>
struct EstimateSpaceToReserveAll<std::index_sequence<I...>> {
template <bool Tag, typename T>
FOLLY_ERASE static constexpr size_t one(const T& v) {
if constexpr (!Tag) {
return 0;
} else {
return estimateSpaceNeeded(v);
}
}
template <class... T>
static size_t call(const T&... v) {
const size_t sizes[] = {one<(I + 1 < sizeof...(I))>(v)...};
size_t size = 0;
for (const auto s : sizes) {
size += s;
}
return size;
}
};
template <class O>
void reserveInTarget(const O& o) {
(void)o;
}
template <class T, class O>
void reserveInTarget(const T& v, const O& o) {
o->reserve(estimateSpaceNeeded(v));
}
template <class T0, class T1, class... Ts>
void reserveInTarget(const T0& v0, const T1& v1, const Ts&... vs) {
using seq = std::index_sequence_for<T0, T1, Ts...>;
getLastElement(vs...)->reserve(
EstimateSpaceToReserveAll<seq>::call(v0, v1, vs...));
}
template <class Delimiter, class... Ts>
void reserveInTargetDelim(const Delimiter& d, const Ts&... vs) {
static_assert(sizeof...(vs) >= 2, "Needs at least 2 args");
using seq = std::index_sequence_for<Ts...>;
size_t fordelim = (sizeof...(vs) - 2) * estimateSpaceNeeded(d);
getLastElement(vs...)->reserve(
fordelim + EstimateSpaceToReserveAll<seq>::call(vs...));
}
template <typename>
struct ToAppendStrImplAll;
template <size_t... I>
struct ToAppendStrImplAll<std::index_sequence<I...>> {
template <bool Tag, class T, class Tgt>
FOLLY_ERASE static void one(const T& v, Tgt* result) {
if constexpr (Tag) {
toAppend(v, result);
}
}
template <class... T>
static void call(const T&... v) {
auto r = getLastElement(v...);
((one<I + 1 < sizeof...(T)>(v, r)), ...);
}
};
template <typename>
struct ToAppendDelimStrImplAll;
template <size_t... I>
struct ToAppendDelimStrImplAll<std::index_sequence<I...>> {
template <size_t Tag, class Delimiter, class T, class Tgt>
FOLLY_ERASE static void one(const Delimiter& d, const T& v, Tgt* result) {
if constexpr (Tag >= 1) {
toAppend(v, result);
}
if constexpr (Tag >= 2) {
toAppend(d, result);
}
}
template <class Delimiter, class... T>
static void call(const Delimiter& d, const T&... v) {
static_assert(sizeof...(I) > 0);
constexpr size_t N = sizeof...(I) - 1;
auto r = detail::getLastElement(v...);
((one<(N - I < 2 ? N - I : 2)>(d, v, r)), ...);
}
};
template <
class Delimiter,
class T,
class... Ts,
std::enable_if_t<
sizeof...(Ts) >= 2 &&
IsSomeString<typename std::remove_pointer<
detail::LastElement<Ts...>>::type>::value,
int> = 0>
void toAppendDelimStrImpl(const Delimiter& delim, const T& v, const Ts&... vs) {
using seq = std::index_sequence_for<T, Ts...>;
ToAppendDelimStrImplAll<seq>::call(delim, v, vs...);
}
} // namespace detail
#endif
/**
* Variadic conversion to string. Appends each element in turn.
* If we have two or more things to append, we will not reserve
* the space for them and will depend on strings exponential growth.
* If you just append once consider using toAppendFit which reserves
* the space needed (but does not have exponential as a result).
*
* Custom implementations of toAppend() can be provided in the same namespace as
* the type to customize printing. estimateSpaceNeed() may also be provided to
* avoid reallocations in toAppendFit():
*
* namespace other_namespace {
*
* template <class String>
* void toAppend(const OtherType&, String* out);
*
* // optional
* size_t estimateSpaceNeeded(const OtherType&);
*
* }
*/
template <
class... Ts,
std::enable_if_t<
sizeof...(Ts) >= 3 &&
IsSomeString<typename std::remove_pointer<
detail::LastElement<Ts...>>::type>::value,
int> = 0>
void toAppend(const Ts&... vs) {
using seq = std::index_sequence_for<Ts...>;
detail::ToAppendStrImplAll<seq>::call(vs...);
}
/**
* @overloadbrief toAppend, but pre-allocate the exact amount of space required.
*
* Special version of the call that preallocates exactly as much memory
* as need for arguments to be stored in target. This means we are
* not doing exponential growth when we append. If you are using it
* in a loop you are aiming at your foot with a big perf-destroying
* bazooka.
* On the other hand if you are appending to a string once, this
* will probably save a few calls to malloc.
*/
template <
class... Ts,
std::enable_if_t<
IsSomeString<typename std::remove_pointer<
detail::LastElement<Ts...>>::type>::value,
int> = 0>
void toAppendFit(const Ts&... vs) {
::folly::detail::reserveInTarget(vs...);
toAppend(vs...);
}
template <class Ts>
void toAppendFit(const Ts&) {}
/**
* Variadic base case: do nothing.
*/
template <class Tgt>
typename std::enable_if<IsSomeString<Tgt>::value>::type toAppend(
Tgt* /* result */) {}
/**
* @overloadbrief Use a specified delimiter between appendees.
*
* Variadic base case: do nothing.
*/
template <class Delimiter, class Tgt>
typename std::enable_if<IsSomeString<Tgt>::value>::type toAppendDelim(
const Delimiter& /* delim */, Tgt* /* result */) {}
/**
* 1 element: same as toAppend.
*/
template <class Delimiter, class T, class Tgt>
typename std::enable_if<IsSomeString<Tgt>::value>::type toAppendDelim(
const Delimiter& /* delim */, const T& v, Tgt* tgt) {
toAppend(v, tgt);
}
/**
* Append to string with a delimiter in between elements. Check out
* comments for toAppend for details about memory allocation.
*/
template <
class Delimiter,
class... Ts,
std::enable_if_t<
sizeof...(Ts) >= 3 &&
IsSomeString<typename std::remove_pointer<
detail::LastElement<Ts...>>::type>::value,
int> = 0>
void toAppendDelim(const Delimiter& delim, const Ts&... vs) {
detail::toAppendDelimStrImpl(delim, vs...);
}
/**
* @overloadbrief toAppend with custom delimiter and exact pre-allocation.
*
* Detail in comment for toAppendFit
*/
template <
class Delimiter,
class... Ts,
std::enable_if_t<
IsSomeString<typename std::remove_pointer<
detail::LastElement<Ts...>>::type>::value,
int> = 0>
void toAppendDelimFit(const Delimiter& delim, const Ts&... vs) {
detail::reserveInTargetDelim(delim, vs...);
toAppendDelim(delim, vs...);
}
template <class De, class Ts>
void toAppendDelimFit(const De&, const Ts&) {}
/**
* to<SomeString>(v1, v2, ...) uses toAppend() (see below) as back-end
* for all types.
*/
template <
class Tgt,
class... Ts,
std::enable_if_t<
IsSomeString<Tgt>::value &&
(sizeof...(Ts) != 1 ||
!std::is_same<Tgt, detail::LastElement<void, Ts...>>::value),
int> = 0>
Tgt to(const Ts&... vs) {
Tgt result;
toAppendFit(vs..., &result);
return result;
}
/**
* Special version of to<SomeString> for floating point. When calling
* folly::to<SomeString>(double), generic implementation above will
* firstly reserve 24 (or 25 when negative value) bytes. This will
* introduce a malloc call for most mainstream string implementations.
*
* But for most cases, a floating point doesn't need 24 (or 25) bytes to
* be converted as a string.
*
* This special version will not do string reserve.
*/
template <class Tgt, class Src>
typename std::enable_if<
IsSomeString<Tgt>::value && std::is_floating_point<Src>::value,
Tgt>::type
to(Src value) {
Tgt result;
toAppend(value, &result);
return result;
}
/**
* @overloadbrief Like `to`, but uses a custom delimiter.
*
* toDelim<SomeString>(SomeString str) returns itself.
*/
template <class Tgt, class Delim, class Src>
typename std::enable_if<
IsSomeString<Tgt>::value &&
std::is_same<Tgt, typename std::decay<Src>::type>::value,
Tgt>::type
toDelim(const Delim& /* delim */, Src&& value) {
return static_cast<Src&&>(value);
}
/**
* toDelim<SomeString>(delim, v1, v2, ...) uses toAppendDelim() as
* back-end for all types.
*/
template <
class Tgt,
class Delim,
class... Ts,
std::enable_if_t<
IsSomeString<Tgt>::value &&
(sizeof...(Ts) != 1 ||
!std::is_same<Tgt, detail::LastElement<void, Ts...>>::value),
int> = 0>
Tgt toDelim(const Delim& delim, const Ts&... vs) {
Tgt result;
toAppendDelimFit(delim, vs..., &result);
return result;
}
/**
* Conversions from string types to integral types.
*/
namespace detail {
Expected<bool, ConversionCode> str_to_bool(StringPiece* src) noexcept;
template <typename T>
Expected<T, ConversionCode> str_to_floating(StringPiece* src) noexcept;
extern template Expected<float, ConversionCode> str_to_floating<float>(
StringPiece* src) noexcept;
extern template Expected<double, ConversionCode> str_to_floating<double>(
StringPiece* src) noexcept;
template <typename T>
Expected<T, ConversionCode> str_to_floating_fast_float_from_chars(
StringPiece* src) noexcept;
extern template Expected<float, ConversionCode>
str_to_floating_fast_float_from_chars<float>(StringPiece* src) noexcept;
extern template Expected<double, ConversionCode>
str_to_floating_fast_float_from_chars<double>(StringPiece* src) noexcept;
template <class Tgt>
Expected<Tgt, ConversionCode> digits_to(const char* b, const char* e) noexcept;
extern template Expected<char, ConversionCode> digits_to<char>(
const char*, const char*) noexcept;
extern template Expected<signed char, ConversionCode> digits_to<signed char>(
const char*, const char*) noexcept;
extern template Expected<unsigned char, ConversionCode>
digits_to<unsigned char>(const char*, const char*) noexcept;
extern template Expected<short, ConversionCode> digits_to<short>(
const char*, const char*) noexcept;
extern template Expected<unsigned short, ConversionCode>
digits_to<unsigned short>(const char*, const char*) noexcept;
extern template Expected<int, ConversionCode> digits_to<int>(
const char*, const char*) noexcept;
extern template Expected<unsigned int, ConversionCode> digits_to<unsigned int>(
const char*, const char*) noexcept;
extern template Expected<long, ConversionCode> digits_to<long>(
const char*, const char*) noexcept;
extern template Expected<unsigned long, ConversionCode>
digits_to<unsigned long>(const char*, const char*) noexcept;
extern template Expected<long long, ConversionCode> digits_to<long long>(
const char*, const char*) noexcept;
extern template Expected<unsigned long long, ConversionCode>
digits_to<unsigned long long>(const char*, const char*) noexcept;
#if FOLLY_HAVE_INT128_T
extern template Expected<__int128, ConversionCode> digits_to<__int128>(
const char*, const char*) noexcept;
extern template Expected<unsigned __int128, ConversionCode>
digits_to<unsigned __int128>(const char*, const char*) noexcept;
#endif
template <class T>
Expected<T, ConversionCode> str_to_integral(StringPiece* src) noexcept;
extern template Expected<char, ConversionCode> str_to_integral<char>(
StringPiece* src) noexcept;
extern template Expected<signed char, ConversionCode>
str_to_integral<signed char>(StringPiece* src) noexcept;
extern template Expected<unsigned char, ConversionCode>
str_to_integral<unsigned char>(StringPiece* src) noexcept;
extern template Expected<short, ConversionCode> str_to_integral<short>(
StringPiece* src) noexcept;
extern template Expected<unsigned short, ConversionCode>
str_to_integral<unsigned short>(StringPiece* src) noexcept;
extern template Expected<int, ConversionCode> str_to_integral<int>(
StringPiece* src) noexcept;
extern template Expected<unsigned int, ConversionCode>
str_to_integral<unsigned int>(StringPiece* src) noexcept;
extern template Expected<long, ConversionCode> str_to_integral<long>(
StringPiece* src) noexcept;
extern template Expected<unsigned long, ConversionCode>
str_to_integral<unsigned long>(StringPiece* src) noexcept;
extern template Expected<long long, ConversionCode> str_to_integral<long long>(
StringPiece* src) noexcept;
extern template Expected<unsigned long long, ConversionCode>
str_to_integral<unsigned long long>(StringPiece* src) noexcept;
#if FOLLY_HAVE_INT128_T
extern template Expected<__int128, ConversionCode> str_to_integral<__int128>(
StringPiece* src) noexcept;
extern template Expected<unsigned __int128, ConversionCode>
str_to_integral<unsigned __int128>(StringPiece* src) noexcept;
#endif
template <typename T>
typename std::
enable_if<std::is_same<T, bool>::value, Expected<T, ConversionCode>>::type
convertTo(StringPiece* src) noexcept {
return str_to_bool(src);
}
template <typename T>
typename std::enable_if<
std::is_floating_point<T>::value,
Expected<T, ConversionCode>>::type
convertTo(StringPiece* src) noexcept {
return str_to_floating<T>(src);
}
template <typename T>
typename std::enable_if<
is_integral_v<T> && !std::is_same<T, bool>::value,
Expected<T, ConversionCode>>::type
convertTo(StringPiece* src) noexcept {
return str_to_integral<T>(src);
}
} // namespace detail
/**
* String represented as a pair of pointers to char to unsigned
* integrals. Assumes NO whitespace before or after.
*/
template <typename Tgt>
typename std::enable_if<
is_integral_v<Tgt> && !std::is_same<Tgt, bool>::value,
Expected<Tgt, ConversionCode>>::type
tryTo(const char* b, const char* e) noexcept {
return detail::digits_to<Tgt>(b, e);
}
template <typename Tgt>
typename std::enable_if< //
is_integral_v<Tgt> && !std::is_same<Tgt, bool>::value,
Tgt>::type
to(const char* b, const char* e) {
return tryTo<Tgt>(b, e).thenOrThrow(identity, [=](ConversionCode code) {
return makeConversionError(code, StringPiece(b, e));
});
}
/**
* Conversions from string types to arithmetic types.
*/
/**
* Parsing strings to numeric types.
*/
template <typename Tgt>
FOLLY_NODISCARD inline typename std::enable_if< //
is_arithmetic_v<Tgt>,
Expected<StringPiece, ConversionCode>>::type
parseTo(StringPiece src, Tgt& out) {
return detail::convertTo<Tgt>(&src).then([&](Tgt res) {
return void(out = res), src;
});
}
/**
* Integral / Floating Point to integral / Floating Point
*/
namespace detail {
/**
* Bool to integral/float doesn't need any special checks, and this
* overload means we aren't trying to see if a bool is less than
* an integer.
*/
template <class Tgt>
typename std::enable_if<
!std::is_same<Tgt, bool>::value &&
(is_integral_v<Tgt> || std::is_floating_point<Tgt>::value),
Expected<Tgt, ConversionCode>>::type
convertTo(const bool& value) noexcept {
return static_cast<Tgt>(value ? 1 : 0);
}
/**
* Checked conversion from integral to integral. The checks are only
* performed when meaningful, e.g. conversion from int to long goes
* unchecked.
*/
template <class Tgt, class Src>
typename std::enable_if<
is_integral_v<Src> && !std::is_same<Tgt, Src>::value &&
!std::is_same<Tgt, bool>::value && is_integral_v<Tgt>,
Expected<Tgt, ConversionCode>>::type
convertTo(const Src& value) noexcept {
if constexpr (
make_unsigned_t<Tgt>(std::numeric_limits<Tgt>::max()) <
make_unsigned_t<Src>(std::numeric_limits<Src>::max())) {
if (greater_than<Tgt, std::numeric_limits<Tgt>::max()>(value)) {
return makeUnexpected(ConversionCode::ARITH_POSITIVE_OVERFLOW);
}
}
if constexpr (
is_signed_v<Src> && (!is_signed_v<Tgt> || sizeof(Src) > sizeof(Tgt))) {
if (less_than<Tgt, std::numeric_limits<Tgt>::min()>(value)) {
return makeUnexpected(ConversionCode::ARITH_NEGATIVE_OVERFLOW);
}
}
return static_cast<Tgt>(value);
}
/**
* Checked conversion from floating to floating. The checks are only
* performed when meaningful, e.g. conversion from float to double goes
* unchecked.
*/
template <class Tgt, class Src>
typename std::enable_if<
std::is_floating_point<Tgt>::value && std::is_floating_point<Src>::value &&
!std::is_same<Tgt, Src>::value,
Expected<Tgt, ConversionCode>>::type
convertTo(const Src& value) noexcept {
if (FOLLY_UNLIKELY(std::isinf(value))) {
return static_cast<Tgt>(value);
}
if constexpr (
std::numeric_limits<Tgt>::max() < std::numeric_limits<Src>::max()) {
if (value > std::numeric_limits<Tgt>::max()) {
return makeUnexpected(ConversionCode::ARITH_POSITIVE_OVERFLOW);
}
if (value < std::numeric_limits<Tgt>::lowest()) {
return makeUnexpected(ConversionCode::ARITH_NEGATIVE_OVERFLOW);
}
}
return static_cast<Tgt>(value);
}
/**
* Check if a floating point value can safely be converted to an
* integer value without triggering undefined behaviour.
*/
template <typename Tgt, typename Src>
inline typename std::enable_if<
std::is_floating_point<Src>::value && is_integral_v<Tgt> &&
!std::is_same<Tgt, bool>::value,
bool>::type
checkConversion(const Src& value) {
constexpr Src tgtMaxAsSrc = static_cast<Src>(std::numeric_limits<Tgt>::max());
constexpr Src tgtMinAsSrc = static_cast<Src>(std::numeric_limits<Tgt>::min());
// NOTE: The following two comparisons also handle the case where value is
// NaN, as all comparisons with NaN are false.
if (!(value < tgtMaxAsSrc)) {
if (!(value <= tgtMaxAsSrc)) {
return false;
}
const Src mmax = folly::nextafter(tgtMaxAsSrc, Src());
if (static_cast<Tgt>(value - mmax) >
std::numeric_limits<Tgt>::max() - static_cast<Tgt>(mmax)) {
return false;
}
} else if (value <= tgtMinAsSrc) {
if (value < tgtMinAsSrc) {
return false;
}
const Src mmin = folly::nextafter(tgtMinAsSrc, Src());
if (static_cast<Tgt>(value - mmin) <
std::numeric_limits<Tgt>::min() - static_cast<Tgt>(mmin)) {
return false;
}
}
return true;
}
// Integers can always safely be converted to floating point values
template <typename Tgt, typename Src>
constexpr typename std::enable_if<
is_integral_v<Src> && std::is_floating_point<Tgt>::value,
bool>::type
checkConversion(const Src&) {
return true;
}
// Also, floating point values can always be safely converted to bool
// Per the standard, any floating point value that is not zero will yield true
template <typename Tgt, typename Src>
constexpr typename std::enable_if<
std::is_floating_point<Src>::value && std::is_same<Tgt, bool>::value,
bool>::type
checkConversion(const Src&) {
return true;
}
/**
* Checked conversion from integral to floating point and back. The
* result must be convertible back to the source type without loss of
* precision. This seems Draconian but sometimes is what's needed, and
* complements existing routines nicely. For various rounding
* routines, see <math>.
*/
template <typename Tgt, typename Src>
typename std::enable_if<
(is_integral_v<Src> && std::is_floating_point<Tgt>::value) ||
(std::is_floating_point<Src>::value && is_integral_v<Tgt>),
Expected<Tgt, ConversionCode>>::type
convertTo(const Src& value) noexcept {
if (FOLLY_LIKELY(checkConversion<Tgt>(value))) {
Tgt result = static_cast<Tgt>(value);
if (FOLLY_LIKELY(checkConversion<Src>(result))) {
Src witness = static_cast<Src>(result);
if (FOLLY_LIKELY(value == witness)) {
return result;
}
}
}
return makeUnexpected(ConversionCode::ARITH_LOSS_OF_PRECISION);
}
template <typename Tgt, typename Src>
inline std::string errorValue(const Src& value) {
return to<std::string>("(", pretty_name<Tgt>(), ") ", value);
}
template <typename Tgt, typename Src>
using IsArithToArith = std::bool_constant<
!std::is_same<Tgt, Src>::value && !std::is_same<Tgt, bool>::value &&
is_arithmetic_v<Src> && is_arithmetic_v<Tgt>>;
} // namespace detail
template <typename Tgt, typename Src>
typename std::enable_if<
detail::IsArithToArith<Tgt, Src>::value,
Expected<Tgt, ConversionCode>>::type
tryTo(const Src& value) noexcept {
return detail::convertTo<Tgt>(value);
}
template <typename Tgt, typename Src>
typename std::enable_if<detail::IsArithToArith<Tgt, Src>::value, Tgt>::type to(
const Src& value) {
return tryTo<Tgt>(value).thenOrThrow(identity, [&](ConversionCode e) {
return makeConversionError(e, detail::errorValue<Tgt>(value));
});
}
/**
* Custom Conversions
*
* Any type can be used with folly::to by implementing parseTo. The
* implementation should be provided in the namespace of the type to facilitate
* argument-dependent lookup:
*
* namespace other_namespace {
* ::folly::Expected<::folly::StringPiece, SomeErrorCode>
* parseTo(::folly::StringPiece, OtherType&) noexcept;
* }
*/
template <class T>
FOLLY_NODISCARD typename std::enable_if<
std::is_enum<T>::value,
Expected<StringPiece, ConversionCode>>::type
parseTo(StringPiece in, T& out) noexcept {
typename std::underlying_type<T>::type tmp{};
auto restOrError = parseTo(in, tmp);
out = static_cast<T>(tmp); // Harmless if parseTo fails
return restOrError;
}
FOLLY_NODISCARD
inline Expected<StringPiece, ConversionCode> parseTo(
StringPiece in, StringPiece& out) noexcept {
out = in;
return StringPiece{in.end(), in.end()};
}
namespace detail {
template <class Str>
FOLLY_ERASE Expected<StringPiece, ConversionCode> parseToStr(
StringPiece in, Str& out) {
out.clear();
out.append(in.data(), in.size()); // TODO try/catch?
return StringPiece{in.end(), in.end()};
}
} // namespace detail
FOLLY_NODISCARD
inline Expected<StringPiece, ConversionCode> parseTo(
StringPiece in, std::string& out) {
return detail::parseToStr(in, out);
}
FOLLY_NODISCARD
inline Expected<StringPiece, ConversionCode> parseTo(
StringPiece in, std::string_view& out) {
out = std::string_view(in.data(), in.size());
return StringPiece{in.end(), in.end()};
}
FOLLY_NODISCARD
inline Expected<StringPiece, ConversionCode> parseTo(
StringPiece in, fbstring& out) {
return detail::parseToStr(in, out);
}
template <class Str>
FOLLY_NODISCARD inline typename std::enable_if<
IsSomeString<Str>::value,
Expected<StringPiece, ConversionCode>>::type
parseTo(StringPiece in, Str& out) {
return detail::parseToStr(in, out);
}
namespace detail {
template <typename Tgt>
using ParseToResult = decltype(parseTo(StringPiece{}, std::declval<Tgt&>()));
struct CheckTrailingSpace {
Expected<Unit, ConversionCode> operator()(StringPiece sp) const {
auto e = enforceWhitespaceErr(sp);
if (FOLLY_UNLIKELY(e != ConversionCode::SUCCESS)) {
return makeUnexpected(e);
}
return unit;
}
};
template <class Error>
struct ReturnUnit {
template <class T>
constexpr Expected<Unit, Error> operator()(T&&) const {
return unit;
}
};
// Older versions of the parseTo customization point threw on error and
// returned void. Handle that.
template <class Tgt>
inline typename std::enable_if<
std::is_void<ParseToResult<Tgt>>::value,
Expected<StringPiece, ConversionCode>>::type
parseToWrap(StringPiece sp, Tgt& out) {
parseTo(sp, out);
return StringPiece(sp.end(), sp.end());
}
template <class Tgt>
inline typename std::enable_if<
!std::is_void<ParseToResult<Tgt>>::value,
ParseToResult<Tgt>>::type
parseToWrap(StringPiece sp, Tgt& out) {
return parseTo(sp, out);
}
template <typename Tgt>
using ParseToError = ExpectedErrorType<decltype(detail::parseToWrap(
StringPiece{}, std::declval<Tgt&>()))>;
} // namespace detail
/**
* String or StringPiece to target conversion. Accepts leading and trailing
* whitespace, but no non-space trailing characters.
*/
template <class Tgt>
inline typename std::enable_if<
!std::is_same<StringPiece, Tgt>::value,
Expected<Tgt, detail::ParseToError<Tgt>>>::type
tryTo(StringPiece src) noexcept {
Tgt result{};
using Error = detail::ParseToError<Tgt>;
using Check = typename std::conditional<
is_arithmetic_v<Tgt>,
detail::CheckTrailingSpace,
detail::ReturnUnit<Error>>::type;
return parseTo(src, result).then(Check(), [&](Unit) {
return std::move(result);
});
}
template <class Tgt, class Src>
inline typename std::enable_if<
IsSomeString<Src>::value && !std::is_same<StringPiece, Tgt>::value,
Tgt>::type
to(Src const& src) {
return to<Tgt>(StringPiece(src.data(), src.size()));
}
template <class Tgt>
inline
typename std::enable_if<!std::is_same<StringPiece, Tgt>::value, Tgt>::type
to(StringPiece src) {
Tgt result{};
using Error = detail::ParseToError<Tgt>;
using Check = typename std::conditional<
is_arithmetic_v<Tgt>,
detail::CheckTrailingSpace,
detail::ReturnUnit<Error>>::type;
auto tmp = detail::parseToWrap(src, result);
return tmp
.thenOrThrow(
Check(),
[&](Error e) { throw_exception(makeConversionError(e, src)); })
.thenOrThrow(
[&](Unit) { return std::move(result); },
[&](Error e) {
throw_exception(makeConversionError(e, tmp.value()));
});
}
/**
* tryTo/to that take the strings by pointer so the caller gets information
* about how much of the string was consumed by the conversion. These do not
* check for trailing whitespace.
*/
template <class Tgt>
Expected<Tgt, detail::ParseToError<Tgt>> tryTo(StringPiece* src) noexcept {
Tgt result;
return parseTo(*src, result).then([&, src](StringPiece sp) -> Tgt {
*src = sp;
return std::move(result);
});
}
template <class Tgt>
Tgt to(StringPiece* src) {
Tgt result{};
using Error = detail::ParseToError<Tgt>;
return parseTo(*src, result)
.thenOrThrow(
[&, src](StringPiece sp) -> Tgt {
*src = sp;
return std::move(result);
},
[=](Error e) { return makeConversionError(e, *src); });
}
/**
* Enum to anything and back
*/
template <class Tgt, class Src>
typename std::enable_if<
std::is_enum<Src>::value && !std::is_same<Src, Tgt>::value &&
!std::is_convertible<Tgt, StringPiece>::value,
Expected<Tgt, ConversionCode>>::type
tryTo(const Src& value) noexcept {
return tryTo<Tgt>(to_underlying(value));
}
template <class Tgt, class Src>
typename std::enable_if<
!std::is_convertible<Src, StringPiece>::value && std::is_enum<Tgt>::value &&
!std::is_same<Src, Tgt>::value,
Expected<Tgt, ConversionCode>>::type
tryTo(const Src& value) noexcept {
using I = typename std::underlying_type<Tgt>::type;
return tryTo<I>(value).then([](I i) { return static_cast<Tgt>(i); });
}
template <class Tgt, class Src>
typename std::enable_if<
std::is_enum<Src>::value && !std::is_same<Src, Tgt>::value &&
!std::is_convertible<Tgt, StringPiece>::value,
Tgt>::type
to(const Src& value) {
return to<Tgt>(to_underlying(value));
}
template <class Tgt, class Src>
typename std::enable_if<
!std::is_convertible<Src, StringPiece>::value && std::is_enum<Tgt>::value &&
!std::is_same<Src, Tgt>::value,
Tgt>::type
to(const Src& value) {
return static_cast<Tgt>(to<typename std::underlying_type<Tgt>::type>(value));
}
} // namespace folly