2 * Copyright 2015 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
18 * Converts anything to anything, with an emphasis on performance and
21 * @author Andrei Alexandrescu (andrei.alexandrescu@fb.com)
24 #ifndef FOLLY_BASE_CONV_H_
25 #define FOLLY_BASE_CONV_H_
27 #include <folly/FBString.h>
28 #include <folly/Likely.h>
29 #include <folly/Preprocessor.h>
30 #include <folly/Range.h>
32 #include <boost/implicit_cast.hpp>
34 #include <type_traits>
43 // V8 JavaScript implementation
44 #include <double-conversion/double-conversion.h>
46 #define FOLLY_RANGE_CHECK_STRINGIZE(x) #x
47 #define FOLLY_RANGE_CHECK_STRINGIZE2(x) FOLLY_RANGE_CHECK_STRINGIZE(x)
49 // Android doesn't support std::to_string so just use a placeholder there.
51 #define FOLLY_RANGE_CHECK_TO_STRING(x) std::string("N/A")
53 #define FOLLY_RANGE_CHECK_TO_STRING(x) std::to_string(x)
56 #define FOLLY_RANGE_CHECK(condition, message, src) \
57 ((condition) ? (void)0 : throw std::range_error( \
58 (std::string(__FILE__ "(" FOLLY_RANGE_CHECK_STRINGIZE2(__LINE__) "): ") \
59 + (message) + ": '" + (src) + "'").c_str()))
61 #define FOLLY_RANGE_CHECK_BEGIN_END(condition, message, b, e) \
62 FOLLY_RANGE_CHECK(condition, message, std::string((b), (e) - (b)))
64 #define FOLLY_RANGE_CHECK_STRINGPIECE(condition, message, sp) \
65 FOLLY_RANGE_CHECK(condition, message, std::string((sp).data(), (sp).size()))
70 * The identity conversion function.
71 * to<T>(T) returns itself for all types T.
73 template <class Tgt, class Src>
74 typename std::enable_if<std::is_same<Tgt, Src>::value, Tgt>::type
75 to(const Src & value) {
79 template <class Tgt, class Src>
80 typename std::enable_if<std::is_same<Tgt, Src>::value, Tgt>::type
82 return std::move(value);
85 /*******************************************************************************
86 * Integral to integral
87 ******************************************************************************/
90 * Unchecked conversion from integral to boolean. This is different from the
91 * other integral conversions because we use the C convention of treating any
92 * non-zero value as true, instead of range checking.
94 template <class Tgt, class Src>
95 typename std::enable_if<
96 std::is_integral<Src>::value
97 && !std::is_same<Tgt, Src>::value
98 && std::is_same<Tgt, bool>::value,
100 to(const Src & value) {
105 * Checked conversion from integral to integral. The checks are only
106 * performed when meaningful, e.g. conversion from int to long goes
109 template <class Tgt, class Src>
110 typename std::enable_if<
111 std::is_integral<Src>::value
112 && !std::is_same<Tgt, Src>::value
113 && !std::is_same<Tgt, bool>::value
114 && std::is_integral<Tgt>::value,
116 to(const Src & value) {
117 /* static */ if (std::numeric_limits<Tgt>::max()
118 < std::numeric_limits<Src>::max()) {
120 (!greater_than<Tgt, std::numeric_limits<Tgt>::max()>(value)),
122 FOLLY_RANGE_CHECK_TO_STRING(value));
124 /* static */ if (std::is_signed<Src>::value &&
125 (!std::is_signed<Tgt>::value || sizeof(Src) > sizeof(Tgt))) {
127 (!less_than<Tgt, std::numeric_limits<Tgt>::min()>(value)),
129 FOLLY_RANGE_CHECK_TO_STRING(value));
131 return static_cast<Tgt>(value);
134 /*******************************************************************************
135 * Floating point to floating point
136 ******************************************************************************/
138 template <class Tgt, class Src>
139 typename std::enable_if<
140 std::is_floating_point<Tgt>::value
141 && std::is_floating_point<Src>::value
142 && !std::is_same<Tgt, Src>::value,
144 to(const Src & value) {
145 /* static */ if (std::numeric_limits<Tgt>::max() <
146 std::numeric_limits<Src>::max()) {
147 FOLLY_RANGE_CHECK(value <= std::numeric_limits<Tgt>::max(),
149 FOLLY_RANGE_CHECK_TO_STRING(value));
150 FOLLY_RANGE_CHECK(value >= -std::numeric_limits<Tgt>::max(),
152 FOLLY_RANGE_CHECK_TO_STRING(value));
154 return boost::implicit_cast<Tgt>(value);
157 /*******************************************************************************
159 ******************************************************************************/
164 const T& getLastElement(const T & v) {
168 template <class T, class... Ts>
169 typename std::tuple_element<
171 std::tuple<T, Ts...> >::type const&
172 getLastElement(const T&, const Ts&... vs) {
173 return getLastElement(vs...);
176 // This class exists to specialize away std::tuple_element in the case where we
177 // have 0 template arguments. Without this, Clang/libc++ will blow a
178 // static_assert even if tuple_element is protected by an enable_if.
179 template <class... Ts>
180 struct last_element {
181 typedef typename std::enable_if<
183 typename std::tuple_element<
184 sizeof...(Ts) - 1, std::tuple<Ts...>
189 struct last_element<> {
193 } // namespace detail
195 /*******************************************************************************
196 * Conversions from integral types to string types.
197 ******************************************************************************/
199 #if FOLLY_HAVE_INT128_T
202 template <typename IntegerType>
203 constexpr unsigned int
205 return ceil((double(sizeof(IntegerType) * CHAR_BIT) * M_LN2) / M_LN10);
209 unsafeTelescope128(char * buffer, size_t room, unsigned __int128 x) {
210 typedef unsigned __int128 Usrc;
213 while (x >= (Usrc(1) << 64)) { // Using 128-bit division while needed
214 const auto y = x / 10;
215 const auto digit = x % 10;
217 buffer[p--] = '0' + digit;
221 uint64_t xx = x; // Moving to faster 64-bit division thereafter
224 const auto y = xx / 10ULL;
225 const auto digit = xx % 10ULL;
227 buffer[p--] = '0' + digit;
231 buffer[p] = '0' + xx;
240 * Returns the number of digits in the base 10 representation of an
241 * uint64_t. Useful for preallocating buffers and such. It's also used
242 * internally, see below. Measurements suggest that defining a
243 * separate overload for 32-bit integers is not worthwhile.
246 inline uint32_t digits10(uint64_t v) {
249 // For this arch we can get a little help from specialized CPU instructions
250 // which can count leading zeroes; 64 minus that is appx. log (base 2).
251 // Use that to approximate base-10 digits (log_10) and then adjust if needed.
253 // 10^i, defined for i 0 through 19.
254 // This is 20 * 8 == 160 bytes, which fits neatly into 5 cache lines
255 // (assuming a cache line size of 64).
256 static const uint64_t powersOf10[20] FOLLY_ALIGNED(64) = {
257 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000,
258 10000000000, 100000000000, 1000000000000, 10000000000000, 100000000000000,
259 1000000000000000, 10000000000000000, 100000000000000000,
260 1000000000000000000, 10000000000000000000UL
263 // "count leading zeroes" operation not valid; for 0; special case this.
268 // bits is in the ballpark of log_2(v).
269 const uint8_t leadingZeroes = __builtin_clzll(v);
270 const auto bits = 63 - leadingZeroes;
272 // approximate log_10(v) == log_10(2) * bits.
273 // Integer magic below: 77/256 is appx. 0.3010 (log_10(2)).
274 // The +1 is to make this the ceiling of the log_10 estimate.
275 const uint32_t minLength = 1 + ((bits * 77) >> 8);
277 // return that log_10 lower bound, plus adjust if input >= 10^(that bound)
278 // in case there's a small error and we misjudged length.
279 return minLength + (uint32_t) (UNLIKELY (v >= powersOf10[minLength]));
285 if (LIKELY(v < 10)) return result;
286 if (LIKELY(v < 100)) return result + 1;
287 if (LIKELY(v < 1000)) return result + 2;
288 if (LIKELY(v < 10000)) return result + 3;
289 // Skip ahead by 4 orders of magnitude
298 * Copies the ASCII base 10 representation of v into buffer and
299 * returns the number of bytes written. Does NOT append a \0. Assumes
300 * the buffer points to digits10(v) bytes of valid memory. Note that
301 * uint64 needs at most 20 bytes, uint32_t needs at most 10 bytes,
302 * uint16_t needs at most 5 bytes, and so on. Measurements suggest
303 * that defining a separate overload for 32-bit integers is not
306 * This primitive is unsafe because it makes the size assumption and
307 * because it does not add a terminating \0.
310 inline uint32_t uint64ToBufferUnsafe(uint64_t v, char *const buffer) {
311 auto const result = digits10(v);
312 // WARNING: using size_t or pointer arithmetic for pos slows down
313 // the loop below 20x. This is because several 32-bit ops can be
314 // done in parallel, but only fewer 64-bit ones.
315 uint32_t pos = result - 1;
317 // Keep these together so a peephole optimization "sees" them and
318 // computes them in one shot.
319 auto const q = v / 10;
320 auto const r = static_cast<uint32_t>(v % 10);
321 buffer[pos--] = '0' + r;
324 // Last digit is trivial to handle
325 buffer[pos] = static_cast<uint32_t>(v) + '0';
330 * A single char gets appended.
333 void toAppend(char value, Tgt * result) {
338 constexpr typename std::enable_if<
339 std::is_same<T, char>::value,
341 estimateSpaceNeeded(T) {
346 * Ubiquitous helper template for writing string appenders
348 template <class T> struct IsSomeString {
349 enum { value = std::is_same<T, std::string>::value
350 || std::is_same<T, fbstring>::value };
354 * Everything implicitly convertible to const char* gets appended.
356 template <class Tgt, class Src>
357 typename std::enable_if<
358 std::is_convertible<Src, const char*>::value
359 && IsSomeString<Tgt>::value>::type
360 toAppend(Src value, Tgt * result) {
361 // Treat null pointers like an empty string, as in:
362 // operator<<(std::ostream&, const char*).
363 const char* c = value;
365 result->append(value);
370 typename std::enable_if<
371 std::is_convertible<Src, const char*>::value,
373 estimateSpaceNeeded(Src value) {
374 const char *c = value;
376 return folly::StringPiece(value).size();
382 typename std::enable_if<
383 (std::is_convertible<Src, folly::StringPiece>::value ||
384 IsSomeString<Src>::value) &&
385 !std::is_convertible<Src, const char*>::value,
387 estimateSpaceNeeded(Src value) {
388 return folly::StringPiece(value).size();
392 inline size_t estimateSpaceNeeded(std::nullptr_t value) {
397 typename std::enable_if<
398 std::is_pointer<Src>::value &&
399 IsSomeString<std::remove_pointer<Src>>::value,
401 estimateSpaceNeeded(Src value) {
402 return value->size();
406 * Strings get appended, too.
408 template <class Tgt, class Src>
409 typename std::enable_if<
410 IsSomeString<Src>::value && IsSomeString<Tgt>::value>::type
411 toAppend(const Src& value, Tgt * result) {
412 result->append(value);
416 * and StringPiece objects too
419 typename std::enable_if<
420 IsSomeString<Tgt>::value>::type
421 toAppend(StringPiece value, Tgt * result) {
422 result->append(value.data(), value.size());
426 * There's no implicit conversion from fbstring to other string types,
427 * so make a specialization.
430 typename std::enable_if<
431 IsSomeString<Tgt>::value>::type
432 toAppend(const fbstring& value, Tgt * result) {
433 result->append(value.data(), value.size());
436 #if FOLLY_HAVE_INT128_T
438 * Special handling for 128 bit integers.
443 toAppend(__int128 value, Tgt * result) {
444 typedef unsigned __int128 Usrc;
445 char buffer[detail::digitsEnough<unsigned __int128>() + 1];
449 p = detail::unsafeTelescope128(buffer, sizeof(buffer), Usrc(-value));
452 p = detail::unsafeTelescope128(buffer, sizeof(buffer), value);
455 result->append(buffer + p, buffer + sizeof(buffer));
460 toAppend(unsigned __int128 value, Tgt * result) {
461 char buffer[detail::digitsEnough<unsigned __int128>()];
464 p = detail::unsafeTelescope128(buffer, sizeof(buffer), value);
466 result->append(buffer + p, buffer + sizeof(buffer));
470 constexpr typename std::enable_if<
471 std::is_same<T, __int128>::value,
473 estimateSpaceNeeded(T) {
474 return detail::digitsEnough<__int128>();
478 constexpr typename std::enable_if<
479 std::is_same<T, unsigned __int128>::value,
481 estimateSpaceNeeded(T) {
482 return detail::digitsEnough<unsigned __int128>();
488 * int32_t and int64_t to string (by appending) go through here. The
489 * result is APPENDED to a preexisting string passed as the second
490 * parameter. This should be efficient with fbstring because fbstring
491 * incurs no dynamic allocation below 23 bytes and no number has more
492 * than 22 bytes in its textual representation (20 for digits, one for
493 * sign, one for the terminating 0).
495 template <class Tgt, class Src>
496 typename std::enable_if<
497 std::is_integral<Src>::value && std::is_signed<Src>::value &&
498 IsSomeString<Tgt>::value && sizeof(Src) >= 4>::type
499 toAppend(Src value, Tgt * result) {
502 result->push_back('-');
503 result->append(buffer, uint64ToBufferUnsafe(-uint64_t(value), buffer));
505 result->append(buffer, uint64ToBufferUnsafe(value, buffer));
510 typename std::enable_if<
511 std::is_integral<Src>::value && std::is_signed<Src>::value
512 && sizeof(Src) >= 4 && sizeof(Src) < 16,
514 estimateSpaceNeeded(Src value) {
516 return 1 + digits10(static_cast<uint64_t>(-value));
519 return digits10(static_cast<uint64_t>(value));
523 * As above, but for uint32_t and uint64_t.
525 template <class Tgt, class Src>
526 typename std::enable_if<
527 std::is_integral<Src>::value && !std::is_signed<Src>::value
528 && IsSomeString<Tgt>::value && sizeof(Src) >= 4>::type
529 toAppend(Src value, Tgt * result) {
531 result->append(buffer, buffer + uint64ToBufferUnsafe(value, buffer));
535 typename std::enable_if<
536 std::is_integral<Src>::value && !std::is_signed<Src>::value
537 && sizeof(Src) >= 4 && sizeof(Src) < 16,
539 estimateSpaceNeeded(Src value) {
540 return digits10(value);
544 * All small signed and unsigned integers to string go through 32-bit
545 * types int32_t and uint32_t, respectively.
547 template <class Tgt, class Src>
548 typename std::enable_if<
549 std::is_integral<Src>::value
550 && IsSomeString<Tgt>::value && sizeof(Src) < 4>::type
551 toAppend(Src value, Tgt * result) {
553 std::conditional<std::is_signed<Src>::value, int64_t, uint64_t>::type
555 toAppend<Tgt>(static_cast<Intermediate>(value), result);
559 typename std::enable_if<
560 std::is_integral<Src>::value
562 && !std::is_same<Src, char>::value,
564 estimateSpaceNeeded(Src value) {
566 std::conditional<std::is_signed<Src>::value, int64_t, uint64_t>::type
568 return estimateSpaceNeeded(static_cast<Intermediate>(value));
572 * Enumerated values get appended as integers.
574 template <class Tgt, class Src>
575 typename std::enable_if<
576 std::is_enum<Src>::value && IsSomeString<Tgt>::value>::type
577 toAppend(Src value, Tgt * result) {
579 static_cast<typename std::underlying_type<Src>::type>(value), result);
583 typename std::enable_if<
584 std::is_enum<Src>::value, size_t>::type
585 estimateSpaceNeeded(Src value) {
586 return estimateSpaceNeeded(
587 static_cast<typename std::underlying_type<Src>::type>(value));
590 /*******************************************************************************
591 * Conversions from floating-point types to string types.
592 ******************************************************************************/
595 constexpr int kConvMaxDecimalInShortestLow = -6;
596 constexpr int kConvMaxDecimalInShortestHigh = 21;
599 /** Wrapper around DoubleToStringConverter **/
600 template <class Tgt, class Src>
601 typename std::enable_if<
602 std::is_floating_point<Src>::value
603 && IsSomeString<Tgt>::value>::type
607 double_conversion::DoubleToStringConverter::DtoaMode mode,
608 unsigned int numDigits) {
609 using namespace double_conversion;
610 DoubleToStringConverter
611 conv(DoubleToStringConverter::NO_FLAGS,
612 "Infinity", "NaN", 'E',
613 detail::kConvMaxDecimalInShortestLow,
614 detail::kConvMaxDecimalInShortestHigh,
615 6, // max leading padding zeros
616 1); // max trailing padding zeros
618 StringBuilder builder(buffer, sizeof(buffer));
620 case DoubleToStringConverter::SHORTEST:
621 conv.ToShortest(value, &builder);
623 case DoubleToStringConverter::FIXED:
624 conv.ToFixed(value, numDigits, &builder);
627 CHECK(mode == DoubleToStringConverter::PRECISION);
628 conv.ToPrecision(value, numDigits, &builder);
631 const size_t length = builder.position();
633 result->append(buffer, length);
637 * As above, but for floating point
639 template <class Tgt, class Src>
640 typename std::enable_if<
641 std::is_floating_point<Src>::value
642 && IsSomeString<Tgt>::value>::type
643 toAppend(Src value, Tgt * result) {
645 value, result, double_conversion::DoubleToStringConverter::SHORTEST, 0);
649 * Upper bound of the length of the output from
650 * DoubleToStringConverter::ToShortest(double, StringBuilder*),
651 * as used in toAppend(double, string*).
654 typename std::enable_if<
655 std::is_floating_point<Src>::value, size_t>::type
656 estimateSpaceNeeded(Src value) {
657 // kBase10MaximalLength is 17. We add 1 for decimal point,
658 // e.g. 10.0/9 is 17 digits and 18 characters, including the decimal point.
659 constexpr int kMaxMantissaSpace =
660 double_conversion::DoubleToStringConverter::kBase10MaximalLength + 1;
661 // strlen("E-") + digits10(numeric_limits<double>::max_exponent10)
662 constexpr int kMaxExponentSpace = 2 + 3;
663 static const int kMaxPositiveSpace = std::max({
664 // E.g. 1.1111111111111111E-100.
665 kMaxMantissaSpace + kMaxExponentSpace,
666 // E.g. 0.000001.1111111111111111, if kConvMaxDecimalInShortestLow is -6.
667 kMaxMantissaSpace - detail::kConvMaxDecimalInShortestLow,
668 // If kConvMaxDecimalInShortestHigh is 21, then 1e21 is the smallest
669 // number > 1 which ToShortest outputs in exponential notation,
670 // so 21 is the longest non-exponential number > 1.
671 detail::kConvMaxDecimalInShortestHigh
673 return kMaxPositiveSpace + (value < 0); // +1 for minus sign, if negative
677 * This can be specialized, together with adding specialization
678 * for estimateSpaceNeed for your type, so that we allocate
679 * as much as you need instead of the default
682 struct HasLengthEstimator : std::false_type {};
685 constexpr typename std::enable_if<
686 !std::is_fundamental<Src>::value
687 #ifdef FOLLY_HAVE_INT128_T
688 // On OSX 10.10, is_fundamental<__int128> is false :-O
689 && !std::is_same<__int128, Src>::value
690 && !std::is_same<unsigned __int128, Src>::value
692 && !IsSomeString<Src>::value
693 && !std::is_convertible<Src, const char*>::value
694 && !std::is_convertible<Src, StringPiece>::value
695 && !std::is_enum<Src>::value
696 && !HasLengthEstimator<Src>::value,
698 estimateSpaceNeeded(const Src&) {
699 return sizeof(Src) + 1; // dumbest best effort ever?
704 inline size_t estimateSpaceToReserve(size_t sofar) {
708 template <class T, class... Ts>
709 size_t estimateSpaceToReserve(size_t sofar, const T& v, const Ts&... vs) {
710 return estimateSpaceToReserve(sofar + estimateSpaceNeeded(v), vs...);
714 size_t estimateSpaceToReserve(size_t sofar, const T& v) {
715 return sofar + estimateSpaceNeeded(v);
719 void reserveInTarget(const Ts&...vs) {
720 getLastElement(vs...)->reserve(estimateSpaceToReserve(0, vs...));
723 template<class Delimiter, class...Ts>
724 void reserveInTargetDelim(const Delimiter& d, const Ts&...vs) {
725 static_assert(sizeof...(vs) >= 2, "Needs at least 2 args");
726 size_t fordelim = (sizeof...(vs) - 2) * estimateSpaceToReserve(0, d);
727 getLastElement(vs...)->reserve(estimateSpaceToReserve(fordelim, vs...));
731 * Variadic base case: append one element
733 template <class T, class Tgt>
734 typename std::enable_if<
735 IsSomeString<typename std::remove_pointer<Tgt>::type>
737 toAppendStrImpl(const T& v, Tgt result) {
741 template <class T, class... Ts>
742 typename std::enable_if<sizeof...(Ts) >= 2
744 typename std::remove_pointer<
745 typename detail::last_element<Ts...>::type
746 >::type>::value>::type
747 toAppendStrImpl(const T& v, const Ts&... vs) {
748 toAppend(v, getLastElement(vs...));
749 toAppendStrImpl(vs...);
752 template <class Delimiter, class T, class Tgt>
753 typename std::enable_if<
754 IsSomeString<typename std::remove_pointer<Tgt>::type>
756 toAppendDelimStrImpl(const Delimiter& delim, const T& v, Tgt result) {
760 template <class Delimiter, class T, class... Ts>
761 typename std::enable_if<sizeof...(Ts) >= 2
763 typename std::remove_pointer<
764 typename detail::last_element<Ts...>::type
765 >::type>::value>::type
766 toAppendDelimStrImpl(const Delimiter& delim, const T& v, const Ts&... vs) {
767 // we are really careful here, calling toAppend with just one element does
768 // not try to estimate space needed (as we already did that). If we call
769 // toAppend(v, delim, ....) we would do unnecesary size calculation
770 toAppend(v, detail::getLastElement(vs...));
771 toAppend(delim, detail::getLastElement(vs...));
772 toAppendDelimStrImpl(delim, vs...);
778 * Variadic conversion to string. Appends each element in turn.
779 * If we have two or more things to append, we it will not reserve
780 * the space for them and will depend on strings exponential growth.
781 * If you just append once consider using toAppendFit which reserves
782 * the space needed (but does not have exponential as a result).
784 template <class... Ts>
785 typename std::enable_if<sizeof...(Ts) >= 3
787 typename std::remove_pointer<
788 typename detail::last_element<Ts...>::type
789 >::type>::value>::type
790 toAppend(const Ts&... vs) {
791 ::folly::detail::toAppendStrImpl(vs...);
795 * Special version of the call that preallocates exaclty as much memory
796 * as need for arguments to be stored in target. This means we are
797 * not doing exponential growth when we append. If you are using it
798 * in a loop you are aiming at your foot with a big perf-destroying
800 * On the other hand if you are appending to a string once, this
801 * will probably save a few calls to malloc.
803 template <class... Ts>
804 typename std::enable_if<
806 typename std::remove_pointer<
807 typename detail::last_element<Ts...>::type
808 >::type>::value>::type
809 toAppendFit(const Ts&... vs) {
810 ::folly::detail::reserveInTarget(vs...);
815 void toAppendFit(const Ts&) {}
818 * Variadic base case: do nothing.
821 typename std::enable_if<IsSomeString<Tgt>::value>::type
822 toAppend(Tgt* result) {
826 * Variadic base case: do nothing.
828 template <class Delimiter, class Tgt>
829 typename std::enable_if<IsSomeString<Tgt>::value>::type
830 toAppendDelim(const Delimiter& delim, Tgt* result) {
834 * 1 element: same as toAppend.
836 template <class Delimiter, class T, class Tgt>
837 typename std::enable_if<IsSomeString<Tgt>::value>::type
838 toAppendDelim(const Delimiter& delim, const T& v, Tgt* tgt) {
843 * Append to string with a delimiter in between elements. Check out
844 * comments for toAppend for details about memory allocation.
846 template <class Delimiter, class... Ts>
847 typename std::enable_if<sizeof...(Ts) >= 3
849 typename std::remove_pointer<
850 typename detail::last_element<Ts...>::type
851 >::type>::value>::type
852 toAppendDelim(const Delimiter& delim, const Ts&... vs) {
853 detail::toAppendDelimStrImpl(delim, vs...);
857 * Detail in comment for toAppendFit
859 template <class Delimiter, class... Ts>
860 typename std::enable_if<
862 typename std::remove_pointer<
863 typename detail::last_element<Ts...>::type
864 >::type>::value>::type
865 toAppendDelimFit(const Delimiter& delim, const Ts&... vs) {
866 detail::reserveInTargetDelim(delim, vs...);
867 toAppendDelim(delim, vs...);
870 template <class De, class Ts>
871 void toAppendDelimFit(const De&, const Ts&) {}
874 * to<SomeString>(v1, v2, ...) uses toAppend() (see below) as back-end
877 template <class Tgt, class... Ts>
878 typename std::enable_if<
879 IsSomeString<Tgt>::value && (
880 sizeof...(Ts) != 1 ||
881 !std::is_same<Tgt, typename detail::last_element<Ts...>::type>::value),
883 to(const Ts&... vs) {
885 toAppendFit(vs..., &result);
890 * toDelim<SomeString>(SomeString str) returns itself.
892 template <class Tgt, class Delim, class Src>
893 typename std::enable_if<
894 IsSomeString<Tgt>::value && std::is_same<Tgt, Src>::value,
896 toDelim(const Delim& delim, const Src & value) {
901 * toDelim<SomeString>(delim, v1, v2, ...) uses toAppendDelim() as
902 * back-end for all types.
904 template <class Tgt, class Delim, class... Ts>
905 typename std::enable_if<
906 IsSomeString<Tgt>::value && (
907 sizeof...(Ts) != 1 ||
908 !std::is_same<Tgt, typename detail::last_element<Ts...>::type>::value),
910 toDelim(const Delim& delim, const Ts&... vs) {
912 toAppendDelimFit(delim, vs..., &result);
916 /*******************************************************************************
917 * Conversions from string types to integral types.
918 ******************************************************************************/
923 * Finds the first non-digit in a string. The number of digits
924 * searched depends on the precision of the Tgt integral. Assumes the
925 * string starts with NO whitespace and NO sign.
927 * The semantics of the routine is:
929 * if (b >= e || !isdigit(*b)) return b;
932 * Complete unrolling marks bottom-line (i.e. entire conversion)
933 * improvements of 20%.
936 const char* findFirstNonDigit(const char* b, const char* e) {
938 auto const c = static_cast<unsigned>(*b) - '0';
944 // Maximum value of number when represented as a string
945 template <class T> struct MaxString {
946 static const char*const value;
949 bool str_to_bool(StringPiece* src);
952 Tgt digits_to(const char* b, const char* e);
954 extern template unsigned char digits_to<unsigned char>(const char* b,
956 extern template unsigned short digits_to<unsigned short>(const char* b,
958 extern template unsigned int digits_to<unsigned int>(const char* b,
960 extern template unsigned long digits_to<unsigned long>(const char* b,
962 extern template unsigned long long digits_to<unsigned long long>(
963 const char* b, const char* e);
964 #if FOLLY_HAVE_INT128_T
965 extern template unsigned __int128 digits_to<unsigned __int128>(const char* b,
969 } // namespace detail
972 * String represented as a pair of pointers to char to unsigned
973 * integrals. Assumes NO whitespace before or after.
976 typename std::enable_if<
977 std::is_integral<Tgt>::value && !std::is_signed<Tgt>::value
978 && !std::is_same<typename std::remove_cv<Tgt>::type, bool>::value,
980 to(const char * b, const char * e) {
981 return detail::digits_to<Tgt>(b, e);
985 * String represented as a pair of pointers to char to signed
986 * integrals. Assumes NO whitespace before or after. Allows an
987 * optional leading sign.
990 typename std::enable_if<
991 std::is_integral<Tgt>::value && std::is_signed<Tgt>::value,
993 to(const char * b, const char * e) {
994 FOLLY_RANGE_CHECK(b < e, "Empty input string in conversion to integral",
995 to<std::string>("b: ", intptr_t(b), " e: ", intptr_t(e)));
998 Tgt result = -to<typename std::make_unsigned<Tgt>::type>(b + 1, e);
999 FOLLY_RANGE_CHECK_BEGIN_END(result <= 0, "Negative overflow.", b, e);
1002 FOLLY_RANGE_CHECK_BEGIN_END(*b == '+', "Invalid lead character", b, e);
1005 Tgt result = to<typename std::make_unsigned<Tgt>::type>(b, e);
1006 FOLLY_RANGE_CHECK_BEGIN_END(result >= 0, "Overflow", b, e);
1011 * Parsing strings to integrals. These routines differ from
1012 * to<integral>(string) in that they take a POINTER TO a StringPiece
1013 * and alter that StringPiece to reflect progress information.
1017 * StringPiece to integrals, with progress information. Alters the
1018 * StringPiece parameter to munch the already-parsed characters.
1020 template <class Tgt>
1021 typename std::enable_if<
1022 std::is_integral<Tgt>::value
1023 && !std::is_same<typename std::remove_cv<Tgt>::type, bool>::value,
1025 to(StringPiece * src) {
1027 auto b = src->data(), past = src->data() + src->size();
1029 FOLLY_RANGE_CHECK_STRINGPIECE(b < past,
1030 "No digits found in input string", *src);
1031 if (!isspace(*b)) break;
1036 // First digit is customized because we test for sign
1037 bool negative = false;
1038 /* static */ if (std::is_signed<Tgt>::value) {
1043 FOLLY_RANGE_CHECK_STRINGPIECE(*m == '+', "Invalid leading character in "
1044 "conversion to integral", *src);
1050 FOLLY_RANGE_CHECK_STRINGPIECE(m < past, "No digits found in input string",
1052 FOLLY_RANGE_CHECK_STRINGPIECE(isdigit(*m), "Non-digit character found", *src);
1053 m = detail::findFirstNonDigit<Tgt>(m + 1, past);
1056 /* static */ if (!std::is_signed<Tgt>::value) {
1057 result = detail::digits_to<typename std::make_unsigned<Tgt>::type>(b, m);
1059 auto t = detail::digits_to<typename std::make_unsigned<Tgt>::type>(b, m);
1062 FOLLY_RANGE_CHECK_STRINGPIECE(is_non_positive(result),
1063 "Negative overflow", *src);
1066 FOLLY_RANGE_CHECK_STRINGPIECE(is_non_negative(result), "Overflow", *src);
1069 src->advance(m - src->data());
1074 * StringPiece to bool, with progress information. Alters the
1075 * StringPiece parameter to munch the already-parsed characters.
1077 template <class Tgt>
1078 typename std::enable_if<
1079 std::is_same<typename std::remove_cv<Tgt>::type, bool>::value,
1081 to(StringPiece * src) {
1082 return detail::str_to_bool(src);
1088 * Enforce that the suffix following a number is made up only of whitespace.
1090 inline void enforceWhitespace(const char* b, const char* e) {
1091 for (; b != e; ++b) {
1092 FOLLY_RANGE_CHECK_BEGIN_END(isspace(*b),
1093 to<std::string>("Non-whitespace: ", *b),
1098 } // namespace detail
1101 * String or StringPiece to integrals. Accepts leading and trailing
1102 * whitespace, but no non-space trailing characters.
1104 template <class Tgt>
1105 typename std::enable_if<
1106 std::is_integral<Tgt>::value,
1108 to(StringPiece src) {
1109 Tgt result = to<Tgt>(&src);
1110 detail::enforceWhitespace(src.data(), src.data() + src.size());
1114 /*******************************************************************************
1115 * Conversions from string types to floating-point types.
1116 ******************************************************************************/
1119 * StringPiece to double, with progress information. Alters the
1120 * StringPiece parameter to munch the already-parsed characters.
1122 template <class Tgt>
1123 inline typename std::enable_if<
1124 std::is_floating_point<Tgt>::value,
1126 to(StringPiece *const src) {
1127 using namespace double_conversion;
1128 static StringToDoubleConverter
1129 conv(StringToDoubleConverter::ALLOW_TRAILING_JUNK
1130 | StringToDoubleConverter::ALLOW_LEADING_SPACES,
1132 // return this for junk input string
1133 std::numeric_limits<double>::quiet_NaN(),
1136 FOLLY_RANGE_CHECK_STRINGPIECE(!src->empty(),
1137 "No digits found in input string", *src);
1140 auto result = conv.StringToDouble(src->data(),
1141 static_cast<int>(src->size()),
1142 &length); // processed char count
1144 if (!std::isnan(result)) {
1145 src->advance(length);
1149 for (;; src->advance(1)) {
1151 throw std::range_error("Unable to convert an empty string"
1152 " to a floating point value.");
1154 if (!isspace(src->front())) {
1159 // Was that "inf[inity]"?
1160 if (src->size() >= 3 && toupper((*src)[0]) == 'I'
1161 && toupper((*src)[1]) == 'N' && toupper((*src)[2]) == 'F') {
1162 if (src->size() >= 8 &&
1163 toupper((*src)[3]) == 'I' &&
1164 toupper((*src)[4]) == 'N' &&
1165 toupper((*src)[5]) == 'I' &&
1166 toupper((*src)[6]) == 'T' &&
1167 toupper((*src)[7]) == 'Y') {
1172 return std::numeric_limits<Tgt>::infinity();
1175 // Was that "-inf[inity]"?
1176 if (src->size() >= 4 && toupper((*src)[0]) == '-'
1177 && toupper((*src)[1]) == 'I' && toupper((*src)[2]) == 'N'
1178 && toupper((*src)[3]) == 'F') {
1179 if (src->size() >= 9 &&
1180 toupper((*src)[4]) == 'I' &&
1181 toupper((*src)[5]) == 'N' &&
1182 toupper((*src)[6]) == 'I' &&
1183 toupper((*src)[7]) == 'T' &&
1184 toupper((*src)[8]) == 'Y') {
1189 return -std::numeric_limits<Tgt>::infinity();
1193 if (src->size() >= 3 && toupper((*src)[0]) == 'N'
1194 && toupper((*src)[1]) == 'A' && toupper((*src)[2]) == 'N') {
1196 return std::numeric_limits<Tgt>::quiet_NaN();
1200 if (src->size() >= 4 &&
1201 toupper((*src)[0]) == '-' &&
1202 toupper((*src)[1]) == 'N' &&
1203 toupper((*src)[2]) == 'A' &&
1204 toupper((*src)[3]) == 'N') {
1206 return -std::numeric_limits<Tgt>::quiet_NaN();
1210 throw std::range_error("Unable to convert \"" + src->toString()
1211 + "\" to a floating point value.");
1215 * Any string, const char*, or StringPiece to double.
1217 template <class Tgt>
1218 typename std::enable_if<
1219 std::is_floating_point<Tgt>::value,
1221 to(StringPiece src) {
1222 Tgt result = to<double>(&src);
1223 detail::enforceWhitespace(src.data(), src.data() + src.size());
1227 /*******************************************************************************
1228 * Integral to floating point and back
1229 ******************************************************************************/
1232 * Checked conversion from integral to flating point and back. The
1233 * result must be convertible back to the source type without loss of
1234 * precision. This seems Draconian but sometimes is what's needed, and
1235 * complements existing routines nicely. For various rounding
1236 * routines, see <math>.
1238 template <class Tgt, class Src>
1239 typename std::enable_if<
1240 (std::is_integral<Src>::value && std::is_floating_point<Tgt>::value)
1242 (std::is_floating_point<Src>::value && std::is_integral<Tgt>::value),
1244 to(const Src & value) {
1246 auto witness = static_cast<Src>(result);
1247 if (value != witness) {
1248 throw std::range_error(
1249 to<std::string>("to<>: loss of precision when converting ", value,
1250 #ifdef FOLLY_HAS_RTTI
1251 " to type ", typeid(Tgt).name()
1260 /*******************************************************************************
1261 * Enum to anything and back
1262 ******************************************************************************/
1264 template <class Tgt, class Src>
1265 typename std::enable_if<
1266 std::is_enum<Src>::value && !std::is_same<Src, Tgt>::value, Tgt>::type
1267 to(const Src & value) {
1268 return to<Tgt>(static_cast<typename std::underlying_type<Src>::type>(value));
1271 template <class Tgt, class Src>
1272 typename std::enable_if<
1273 std::is_enum<Tgt>::value && !std::is_same<Src, Tgt>::value, Tgt>::type
1274 to(const Src & value) {
1275 return static_cast<Tgt>(to<typename std::underlying_type<Tgt>::type>(value));
1278 } // namespace folly
1280 // FOLLY_CONV_INTERNAL is defined by Conv.cpp. Keep the FOLLY_RANGE_CHECK
1281 // macro for use in Conv.cpp, but #undefine it everywhere else we are included,
1282 // to avoid defining this global macro name in other files that include Conv.h.
1283 #ifndef FOLLY_CONV_INTERNAL
1284 #undef FOLLY_RANGE_CHECK
1285 #undef FOLLY_RANGE_CHECK_BEGIN_END
1286 #undef FOLLY_RANGE_CHECK_STRINGPIECE
1287 #undef FOLLY_RANGE_CHECK_STRINGIZE
1288 #undef FOLLY_RANGE_CHECK_STRINGIZE2
1291 #endif /* FOLLY_BASE_CONV_H_ */