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- /*
- * Copyright 2011-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.
- */
- /**
- * Converts anything to anything, with an emphasis on performance and
- * safety.
- *
- * @author Andrei Alexandrescu (andrei.alexandrescu@fb.com)
- */
- #pragma once
- #include <algorithm>
- #include <cctype>
- #include <climits>
- #include <cstddef>
- #include <limits>
- #include <stdexcept>
- #include <string>
- #include <tuple>
- #include <type_traits>
- #include <typeinfo>
- #include <utility>
- #include <double-conversion/double-conversion.h> // V8 JavaScript implementation
- #include <folly/Demangle.h>
- #include <folly/Expected.h>
- #include <folly/FBString.h>
- #include <folly/Likely.h>
- #include <folly/Range.h>
- #include <folly/Traits.h>
- #include <folly/Unit.h>
- #include <folly/lang/Exception.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,
- NUM_ERROR_CODES, // has to be the last entry
- };
- struct ConversionErrorBase : std::range_error {
- using std::range_error::range_error;
- };
- class 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 sp);
- 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 (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
- /**
- * 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) {
- return std::forward<Src>(value);
- }
- 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 std::forward<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<
- std::is_arithmetic<Src>::value && !std::is_same<Tgt, Src>::value &&
- std::is_same<Tgt, bool>::value,
- Expected<Tgt, ConversionCode>>::type
- tryTo(const Src& value) {
- return value != Src();
- }
- template <class Tgt, class Src>
- typename std::enable_if<
- std::is_arithmetic<Src>::value && !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 {
- #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>
- auto getLastElement(Ts&&... ts) -> decltype(std::get<sizeof...(Ts) - 1>(
- std::forward_as_tuple(std::forward<Ts>(ts)...))) {
- return std::get<sizeof...(Ts) - 1>(
- std::forward_as_tuple(std::forward<Ts>(ts)...));
- }
- inline void getLastElement() {}
- template <size_t size, typename... Ts>
- struct LastElementType : std::tuple_element<size - 1, std::tuple<Ts...>> {};
- template <>
- struct LastElementType<0> {
- using type = void;
- };
- template <class... Ts>
- struct LastElement
- : std::decay<typename LastElementType<sizeof...(Ts), Ts...>::type> {};
- #else
- template <typename... Ts>
- struct LastElementImpl {
- static void call(Ignored<Ts>...) {}
- };
- template <typename Head, typename... Ts>
- struct LastElementImpl<Head, Ts...> {
- template <typename Last>
- static Last call(Ignored<Ts>..., Last&& last) {
- return std::forward<Last>(last);
- }
- };
- template <typename... Ts>
- auto getLastElement(const Ts&... ts)
- -> decltype(LastElementImpl<Ts...>::call(ts...)) {
- return LastElementImpl<Ts...>::call(ts...);
- }
- template <class... Ts>
- struct LastElement : std::decay<decltype(
- LastElementImpl<Ts...>::call(std::declval<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() {
- return (unsigned int)(ceil(sizeof(IntegerType) * CHAR_BIT * M_LN2 / M_LN10));
- }
- inline size_t
- unsafeTelescope128(char* buffer, size_t room, unsigned __int128 x) {
- typedef unsigned __int128 Usrc;
- size_t p = room - 1;
- while (x >= (Usrc(1) << 64)) { // Using 128-bit division while needed
- const auto y = x / 10;
- const auto digit = x % 10;
- buffer[p--] = static_cast<char>('0' + digit);
- x = y;
- }
- uint64_t xx = static_cast<uint64_t>(x); // Rest uses faster 64-bit division
- while (xx >= 10) {
- const auto y = xx / 10ULL;
- const auto digit = xx % 10ULL;
- buffer[p--] = static_cast<char>('0' + digit);
- xx = y;
- }
- buffer[p] = static_cast<char>('0' + xx);
- return p;
- }
- } // namespace detail
- #endif
- /**
- * Returns the number of digits in the base 10 representation of an
- * uint64_t. Useful for preallocating buffers and such. It's also used
- * internally, see below. Measurements suggest that defining a
- * separate overload for 32-bit integers is not worthwhile.
- */
- inline uint32_t digits10(uint64_t v) {
- #ifdef __x86_64__
- // For this arch we can get a little help from specialized CPU instructions
- // which can count leading zeroes; 64 minus that is appx. log (base 2).
- // Use that to approximate base-10 digits (log_10) and then adjust if needed.
- // 10^i, defined for i 0 through 19.
- // This is 20 * 8 == 160 bytes, which fits neatly into 5 cache lines
- // (assuming a cache line size of 64).
- alignas(64) static const uint64_t powersOf10[20] = {
- 1,
- 10,
- 100,
- 1000,
- 10000,
- 100000,
- 1000000,
- 10000000,
- 100000000,
- 1000000000,
- 10000000000,
- 100000000000,
- 1000000000000,
- 10000000000000,
- 100000000000000,
- 1000000000000000,
- 10000000000000000,
- 100000000000000000,
- 1000000000000000000,
- 10000000000000000000UL,
- };
- // "count leading zeroes" operation not valid; for 0; special case this.
- if (UNLIKELY(!v)) {
- return 1;
- }
- // bits is in the ballpark of log_2(v).
- const uint32_t leadingZeroes = __builtin_clzll(v);
- const auto bits = 63 - leadingZeroes;
- // approximate log_10(v) == log_10(2) * bits.
- // Integer magic below: 77/256 is appx. 0.3010 (log_10(2)).
- // The +1 is to make this the ceiling of the log_10 estimate.
- const uint32_t minLength = 1 + ((bits * 77) >> 8);
- // return that log_10 lower bound, plus adjust if input >= 10^(that bound)
- // in case there's a small error and we misjudged length.
- return minLength + uint32_t(v >= powersOf10[minLength]);
- #else
- uint32_t result = 1;
- while (true) {
- if (LIKELY(v < 10)) {
- return result;
- }
- if (LIKELY(v < 100)) {
- return result + 1;
- }
- if (LIKELY(v < 1000)) {
- return result + 2;
- }
- if (LIKELY(v < 10000)) {
- return result + 3;
- }
- // Skip ahead by 4 orders of magnitude
- v /= 10000U;
- result += 4;
- }
- #endif
- }
- /**
- * Copies the ASCII base 10 representation of v into buffer and
- * returns the number of bytes written. Does NOT append a \0. Assumes
- * the buffer points to digits10(v) bytes of valid memory. Note that
- * uint64 needs at most 20 bytes, uint32_t needs at most 10 bytes,
- * uint16_t needs at most 5 bytes, and so on. Measurements suggest
- * that defining a separate overload for 32-bit integers is not
- * worthwhile.
- *
- * This primitive is unsafe because it makes the size assumption and
- * because it does not add a terminating \0.
- */
- inline uint32_t uint64ToBufferUnsafe(uint64_t v, char* const buffer) {
- auto const result = digits10(v);
- // WARNING: using size_t or pointer arithmetic for pos slows down
- // the loop below 20x. This is because several 32-bit ops can be
- // done in parallel, but only fewer 64-bit ones.
- uint32_t pos = result - 1;
- while (v >= 10) {
- // Keep these together so a peephole optimization "sees" them and
- // computes them in one shot.
- auto const q = v / 10;
- auto const r = v % 10;
- buffer[pos--] = static_cast<char>('0' + r);
- v = q;
- }
- // Last digit is trivial to handle
- buffer[pos] = static_cast<char>(v + '0');
- return result;
- }
- /**
- * A single char gets appended.
- */
- template <class Tgt>
- void toAppend(char value, Tgt* result) {
- *result += value;
- }
- 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;
- if (c) {
- return folly::StringPiece(value).size();
- };
- return 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];
- size_t p;
- if (value < 0) {
- p = detail::unsafeTelescope128(buffer, sizeof(buffer), -Usrc(value));
- buffer[--p] = '-';
- } else {
- p = detail::unsafeTelescope128(buffer, sizeof(buffer), value);
- }
- result->append(buffer + p, buffer + sizeof(buffer));
- }
- template <class Tgt>
- void toAppend(unsigned __int128 value, Tgt* result) {
- char buffer[detail::digitsEnough<unsigned __int128>()];
- size_t p;
- p = detail::unsafeTelescope128(buffer, sizeof(buffer), value);
- result->append(buffer + p, buffer + sizeof(buffer));
- }
- 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<
- std::is_integral<Src>::value && std::is_signed<Src>::value &&
- IsSomeString<Tgt>::value && sizeof(Src) >= 4>::type
- toAppend(Src value, Tgt* result) {
- char buffer[20];
- if (value < 0) {
- result->push_back('-');
- result->append(
- buffer,
- uint64ToBufferUnsafe(~static_cast<uint64_t>(value) + 1, buffer));
- } else {
- result->append(buffer, uint64ToBufferUnsafe(uint64_t(value), buffer));
- }
- }
- template <class Src>
- typename std::enable_if<
- std::is_integral<Src>::value && std::is_signed<Src>::value &&
- sizeof(Src) >= 4 && sizeof(Src) < 16,
- size_t>::type
- estimateSpaceNeeded(Src value) {
- if (value < 0) {
- // When "value" is the smallest negative, negating it would evoke
- // undefined behavior, so, instead of writing "-value" below, we write
- // "~static_cast<uint64_t>(value) + 1"
- return 1 + digits10(~static_cast<uint64_t>(value) + 1);
- }
- return digits10(static_cast<uint64_t>(value));
- }
- /**
- * As above, but for uint32_t and uint64_t.
- */
- template <class Tgt, class Src>
- typename std::enable_if<
- std::is_integral<Src>::value && !std::is_signed<Src>::value &&
- IsSomeString<Tgt>::value && sizeof(Src) >= 4>::type
- toAppend(Src value, Tgt* result) {
- char buffer[20];
- result->append(buffer, uint64ToBufferUnsafe(value, buffer));
- }
- template <class Src>
- typename std::enable_if<
- std::is_integral<Src>::value && !std::is_signed<Src>::value &&
- sizeof(Src) >= 4 && sizeof(Src) < 16,
- size_t>::type
- estimateSpaceNeeded(Src value) {
- return digits10(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<
- std::is_integral<Src>::value && IsSomeString<Tgt>::value &&
- sizeof(Src) < 4>::type
- toAppend(Src value, Tgt* result) {
- typedef
- typename std::conditional<std::is_signed<Src>::value, int64_t, uint64_t>::
- type Intermediate;
- toAppend<Tgt>(static_cast<Intermediate>(value), result);
- }
- template <class Src>
- typename std::enable_if<
- std::is_integral<Src>::value && sizeof(Src) < 4 &&
- !std::is_same<Src, char>::value,
- size_t>::type
- estimateSpaceNeeded(Src value) {
- typedef
- typename std::conditional<std::is_signed<Src>::value, 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(
- static_cast<typename std::underlying_type<Src>::type>(value), result);
- }
- template <class Src>
- typename std::enable_if<std::is_enum<Src>::value, size_t>::type
- estimateSpaceNeeded(Src value) {
- return estimateSpaceNeeded(
- static_cast<typename std::underlying_type<Src>::type>(value));
- }
- /*******************************************************************************
- * Conversions from floating-point types to string types.
- ******************************************************************************/
- namespace detail {
- constexpr int kConvMaxDecimalInShortestLow = -6;
- constexpr int kConvMaxDecimalInShortestHigh = 21;
- } // namespace detail
- /** Wrapper around DoubleToStringConverter **/
- template <class Tgt, class Src>
- typename std::enable_if<
- std::is_floating_point<Src>::value && IsSomeString<Tgt>::value>::type
- toAppend(
- Src value,
- Tgt* result,
- double_conversion::DoubleToStringConverter::DtoaMode mode,
- unsigned int numDigits) {
- using namespace double_conversion;
- DoubleToStringConverter conv(
- DoubleToStringConverter::NO_FLAGS,
- "Infinity",
- "NaN",
- 'E',
- detail::kConvMaxDecimalInShortestLow,
- detail::kConvMaxDecimalInShortestHigh,
- 6, // max leading padding zeros
- 1); // max trailing padding zeros
- char buffer[256];
- StringBuilder builder(buffer, sizeof(buffer));
- switch (mode) {
- case DoubleToStringConverter::SHORTEST:
- conv.ToShortest(value, &builder);
- break;
- case DoubleToStringConverter::SHORTEST_SINGLE:
- conv.ToShortestSingle(static_cast<float>(value), &builder);
- break;
- case DoubleToStringConverter::FIXED:
- conv.ToFixed(value, int(numDigits), &builder);
- break;
- default:
- CHECK(mode == DoubleToStringConverter::PRECISION);
- conv.ToPrecision(value, int(numDigits), &builder);
- break;
- }
- 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, double_conversion::DoubleToStringConverter::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 =
- double_conversion::DoubleToStringConverter::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
- }
- /**
- * This can be specialized, together with adding specialization
- * for estimateSpaceNeed for your type, so that we allocate
- * as much as you need instead of the default
- */
- template <class Src>
- struct HasLengthEstimator : std::false_type {};
- 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 && !HasLengthEstimator<Src>::value,
- size_t>::type
- estimateSpaceNeeded(const Src&) {
- return sizeof(Src) + 1; // dumbest best effort ever?
- }
- namespace detail {
- template <class Tgt>
- typename std::enable_if<IsSomeString<Tgt>::value, size_t>::type
- estimateSpaceToReserve(size_t sofar, Tgt*) {
- return sofar;
- }
- template <class T, class... Ts>
- size_t estimateSpaceToReserve(size_t sofar, const T& v, const Ts&... vs) {
- return estimateSpaceToReserve(sofar + estimateSpaceNeeded(v), vs...);
- }
- template <class... Ts>
- void reserveInTarget(const Ts&... vs) {
- getLastElement(vs...)->reserve(estimateSpaceToReserve(0, vs...));
- }
- template <class Delimiter, class... Ts>
- void reserveInTargetDelim(const Delimiter& d, const Ts&... vs) {
- static_assert(sizeof...(vs) >= 2, "Needs at least 2 args");
- size_t fordelim = (sizeof...(vs) - 2) *
- estimateSpaceToReserve(0, d, static_cast<std::string*>(nullptr));
- getLastElement(vs...)->reserve(estimateSpaceToReserve(fordelim, vs...));
- }
- /**
- * Variadic base case: append one element
- */
- template <class T, class Tgt>
- typename std::enable_if<
- IsSomeString<typename std::remove_pointer<Tgt>::type>::value>::type
- toAppendStrImpl(const T& v, Tgt result) {
- toAppend(v, result);
- }
- template <class T, class... Ts>
- typename std::enable_if<
- sizeof...(Ts) >= 2 &&
- IsSomeString<typename std::remove_pointer<
- typename detail::LastElement<const Ts&...>::type>::type>::value>::type
- toAppendStrImpl(const T& v, const Ts&... vs) {
- toAppend(v, getLastElement(vs...));
- toAppendStrImpl(vs...);
- }
- template <class Delimiter, class T, class Tgt>
- typename std::enable_if<
- IsSomeString<typename std::remove_pointer<Tgt>::type>::value>::type
- toAppendDelimStrImpl(const Delimiter& /* delim */, const T& v, Tgt result) {
- toAppend(v, result);
- }
- template <class Delimiter, class T, class... Ts>
- typename std::enable_if<
- sizeof...(Ts) >= 2 &&
- IsSomeString<typename std::remove_pointer<
- typename detail::LastElement<const Ts&...>::type>::type>::value>::type
- toAppendDelimStrImpl(const Delimiter& delim, const T& v, const Ts&... vs) {
- // we are really careful here, calling toAppend with just one element does
- // not try to estimate space needed (as we already did that). If we call
- // toAppend(v, delim, ....) we would do unnecesary size calculation
- toAppend(v, detail::getLastElement(vs...));
- toAppend(delim, detail::getLastElement(vs...));
- toAppendDelimStrImpl(delim, vs...);
- }
- } // namespace detail
- /**
- * 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>
- typename std::enable_if<
- sizeof...(Ts) >= 3 &&
- IsSomeString<typename std::remove_pointer<
- typename detail::LastElement<const Ts&...>::type>::type>::value>::type
- toAppend(const Ts&... vs) {
- ::folly::detail::toAppendStrImpl(vs...);
- }
- #ifdef _MSC_VER
- // Special case pid_t on MSVC, because it's a void* rather than an
- // integral type. We can't do a global special case because this is already
- // dangerous enough (as most pointers will implicitly convert to a void*)
- // just doing it for MSVC.
- template <class Tgt>
- void toAppend(const pid_t a, Tgt* res) {
- toAppend(uint64_t(a), res);
- }
- #endif
- /**
- * Special version of the call that preallocates exaclty 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>
- typename std::enable_if<IsSomeString<typename std::remove_pointer<
- typename detail::LastElement<const Ts&...>::type>::type>::value>::type
- 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 */) {}
- /**
- * 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>
- typename std::enable_if<
- sizeof...(Ts) >= 3 &&
- IsSomeString<typename std::remove_pointer<
- typename detail::LastElement<const Ts&...>::type>::type>::value>::type
- toAppendDelim(const Delimiter& delim, const Ts&... vs) {
- detail::toAppendDelimStrImpl(delim, vs...);
- }
- /**
- * Detail in comment for toAppendFit
- */
- template <class Delimiter, class... Ts>
- typename std::enable_if<IsSomeString<typename std::remove_pointer<
- typename detail::LastElement<const Ts&...>::type>::type>::value>::type
- 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>
- typename std::enable_if<
- IsSomeString<Tgt>::value &&
- (sizeof...(Ts) != 1 ||
- !std::is_same<Tgt, typename detail::LastElement<const Ts&...>::type>::
- value),
- Tgt>::type
- 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;
- }
- /**
- * 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 std::forward<Src>(value);
- }
- /**
- * toDelim<SomeString>(delim, v1, v2, ...) uses toAppendDelim() as
- * back-end for all types.
- */
- template <class Tgt, class Delim, class... Ts>
- typename std::enable_if<
- IsSomeString<Tgt>::value &&
- (sizeof...(Ts) != 1 ||
- !std::is_same<Tgt, typename detail::LastElement<const Ts&...>::type>::
- value),
- Tgt>::type
- 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 <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<
- std::is_integral<T>::value && !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<
- std::is_integral<Tgt>::value && !std::is_same<Tgt, bool>::value,
- Expected<Tgt, ConversionCode>>::type
- tryTo(const char* b, const char* e) {
- return detail::digits_to<Tgt>(b, e);
- }
- template <typename Tgt>
- typename std::enable_if<
- std::is_integral<Tgt>::value && !std::is_same<Tgt, bool>::value,
- Tgt>::type
- to(const char* b, const char* e) {
- return tryTo<Tgt>(b, e).thenOrThrow(
- [](Tgt res) { return res; },
- [=](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<
- std::is_arithmetic<Tgt>::value,
- 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 &&
- (std::is_integral<Tgt>::value || 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<
- std::is_integral<Src>::value && !std::is_same<Tgt, Src>::value &&
- !std::is_same<Tgt, bool>::value && std::is_integral<Tgt>::value,
- Expected<Tgt, ConversionCode>>::type
- convertTo(const Src& value) noexcept {
- if /* constexpr */ (
- folly::_t<std::make_unsigned<Tgt>>(std::numeric_limits<Tgt>::max()) <
- folly::_t<std::make_unsigned<Src>>(std::numeric_limits<Src>::max())) {
- if (greater_than<Tgt, std::numeric_limits<Tgt>::max()>(value)) {
- return makeUnexpected(ConversionCode::ARITH_POSITIVE_OVERFLOW);
- }
- }
- if /* constexpr */ (
- std::is_signed<Src>::value &&
- (!std::is_signed<Tgt>::value || 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 /* 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 && std::is_integral<Tgt>::value &&
- !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());
- 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 (std::is_signed<Tgt>::value && 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<
- std::is_integral<Src>::value && 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<
- (std::is_integral<Src>::value && std::is_floating_point<Tgt>::value) ||
- (std::is_floating_point<Src>::value && std::is_integral<Tgt>::value),
- Expected<Tgt, ConversionCode>>::type
- convertTo(const Src& value) noexcept {
- if (LIKELY(checkConversion<Tgt>(value))) {
- Tgt result = static_cast<Tgt>(value);
- if (LIKELY(checkConversion<Src>(result))) {
- Src witness = static_cast<Src>(result);
- if (LIKELY(value == witness)) {
- return result;
- }
- }
- }
- return makeUnexpected(ConversionCode::ARITH_LOSS_OF_PRECISION);
- }
- template <typename Tgt, typename Src>
- inline std::string errorValue(const Src& value) {
- #ifdef FOLLY_HAS_RTTI
- return to<std::string>("(", demangle(typeid(Tgt)), ") ", value);
- #else
- return to<std::string>(value);
- #endif
- }
- template <typename Tgt, typename Src>
- using IsArithToArith = bool_constant<
- !std::is_same<Tgt, Src>::value && !std::is_same<Tgt, bool>::value &&
- std::is_arithmetic<Src>::value && std::is_arithmetic<Tgt>::value>;
- } // 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(
- [](Tgt res) { return res; },
- [&](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()};
- }
- FOLLY_NODISCARD
- inline Expected<StringPiece, ConversionCode> parseTo(
- StringPiece in,
- std::string& out) {
- out.clear();
- out.append(in.data(), in.size()); // TODO try/catch?
- return StringPiece{in.end(), in.end()};
- }
- FOLLY_NODISCARD
- inline Expected<StringPiece, ConversionCode> parseTo(
- StringPiece in,
- fbstring& out) {
- out.clear();
- out.append(in.data(), in.size()); // TODO try/catch?
- return StringPiece{in.end(), in.end()};
- }
- 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 (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) {
- Tgt result{};
- using Error = detail::ParseToError<Tgt>;
- using Check = typename std::conditional<
- std::is_arithmetic<Tgt>::value,
- 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<
- std::is_arithmetic<Tgt>::value,
- 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 whitepsace.
- */
- template <class Tgt>
- Expected<Tgt, detail::ParseToError<Tgt>> tryTo(StringPiece* src) {
- 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) {
- using I = typename std::underlying_type<Src>::type;
- return tryTo<Tgt>(static_cast<I>(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) {
- 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>(static_cast<typename std::underlying_type<Src>::type>(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
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