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 typename std::enable_if<
393 std::is_pointer<Src>::value &&
394 IsSomeString<std::remove_pointer<Src>>::value,
396 estimateSpaceNeeded(Src value) {
397 return value->size();
401 * Strings get appended, too.
403 template <class Tgt, class Src>
404 typename std::enable_if<
405 IsSomeString<Src>::value && IsSomeString<Tgt>::value>::type
406 toAppend(const Src& value, Tgt * result) {
407 result->append(value);
411 * and StringPiece objects too
414 typename std::enable_if<
415 IsSomeString<Tgt>::value>::type
416 toAppend(StringPiece value, Tgt * result) {
417 result->append(value.data(), value.size());
421 * There's no implicit conversion from fbstring to other string types,
422 * so make a specialization.
425 typename std::enable_if<
426 IsSomeString<Tgt>::value>::type
427 toAppend(const fbstring& value, Tgt * result) {
428 result->append(value.data(), value.size());
431 #if FOLLY_HAVE_INT128_T
433 * Special handling for 128 bit integers.
438 toAppend(__int128 value, Tgt * result) {
439 typedef unsigned __int128 Usrc;
440 char buffer[detail::digitsEnough<unsigned __int128>() + 1];
444 p = detail::unsafeTelescope128(buffer, sizeof(buffer), Usrc(-value));
447 p = detail::unsafeTelescope128(buffer, sizeof(buffer), value);
450 result->append(buffer + p, buffer + sizeof(buffer));
455 toAppend(unsigned __int128 value, Tgt * result) {
456 char buffer[detail::digitsEnough<unsigned __int128>()];
459 p = detail::unsafeTelescope128(buffer, sizeof(buffer), value);
461 result->append(buffer + p, buffer + sizeof(buffer));
465 constexpr typename std::enable_if<
466 std::is_same<T, __int128>::value,
468 estimateSpaceNeeded(T) {
469 return detail::digitsEnough<__int128>();
473 constexpr typename std::enable_if<
474 std::is_same<T, unsigned __int128>::value,
476 estimateSpaceNeeded(T) {
477 return detail::digitsEnough<unsigned __int128>();
483 * int32_t and int64_t to string (by appending) go through here. The
484 * result is APPENDED to a preexisting string passed as the second
485 * parameter. This should be efficient with fbstring because fbstring
486 * incurs no dynamic allocation below 23 bytes and no number has more
487 * than 22 bytes in its textual representation (20 for digits, one for
488 * sign, one for the terminating 0).
490 template <class Tgt, class Src>
491 typename std::enable_if<
492 std::is_integral<Src>::value && std::is_signed<Src>::value &&
493 IsSomeString<Tgt>::value && sizeof(Src) >= 4>::type
494 toAppend(Src value, Tgt * result) {
497 result->push_back('-');
498 result->append(buffer, uint64ToBufferUnsafe(-uint64_t(value), buffer));
500 result->append(buffer, uint64ToBufferUnsafe(value, buffer));
505 typename std::enable_if<
506 std::is_integral<Src>::value && std::is_signed<Src>::value
507 && sizeof(Src) >= 4 && sizeof(Src) < 16,
509 estimateSpaceNeeded(Src value) {
511 return 1 + digits10(static_cast<uint64_t>(-value));
514 return digits10(static_cast<uint64_t>(value));
518 * As above, but for uint32_t and uint64_t.
520 template <class Tgt, class Src>
521 typename std::enable_if<
522 std::is_integral<Src>::value && !std::is_signed<Src>::value
523 && IsSomeString<Tgt>::value && sizeof(Src) >= 4>::type
524 toAppend(Src value, Tgt * result) {
526 result->append(buffer, buffer + uint64ToBufferUnsafe(value, buffer));
530 typename std::enable_if<
531 std::is_integral<Src>::value && !std::is_signed<Src>::value
532 && sizeof(Src) >= 4 && sizeof(Src) < 16,
534 estimateSpaceNeeded(Src value) {
535 return digits10(value);
539 * All small signed and unsigned integers to string go through 32-bit
540 * types int32_t and uint32_t, respectively.
542 template <class Tgt, class Src>
543 typename std::enable_if<
544 std::is_integral<Src>::value
545 && IsSomeString<Tgt>::value && sizeof(Src) < 4>::type
546 toAppend(Src value, Tgt * result) {
548 std::conditional<std::is_signed<Src>::value, int64_t, uint64_t>::type
550 toAppend<Tgt>(static_cast<Intermediate>(value), result);
554 typename std::enable_if<
555 std::is_integral<Src>::value
557 && !std::is_same<Src, char>::value,
559 estimateSpaceNeeded(Src value) {
561 std::conditional<std::is_signed<Src>::value, int64_t, uint64_t>::type
563 return estimateSpaceNeeded(static_cast<Intermediate>(value));
567 * Enumerated values get appended as integers.
569 template <class Tgt, class Src>
570 typename std::enable_if<
571 std::is_enum<Src>::value && IsSomeString<Tgt>::value>::type
572 toAppend(Src value, Tgt * result) {
574 static_cast<typename std::underlying_type<Src>::type>(value), result);
578 typename std::enable_if<
579 std::is_enum<Src>::value, size_t>::type
580 estimateSpaceNeeded(Src value) {
581 return estimateSpaceNeeded(
582 static_cast<typename std::underlying_type<Src>::type>(value));
585 /*******************************************************************************
586 * Conversions from floating-point types to string types.
587 ******************************************************************************/
590 constexpr int kConvMaxDecimalInShortestLow = -6;
591 constexpr int kConvMaxDecimalInShortestHigh = 21;
594 /** Wrapper around DoubleToStringConverter **/
595 template <class Tgt, class Src>
596 typename std::enable_if<
597 std::is_floating_point<Src>::value
598 && IsSomeString<Tgt>::value>::type
602 double_conversion::DoubleToStringConverter::DtoaMode mode,
603 unsigned int numDigits) {
604 using namespace double_conversion;
605 DoubleToStringConverter
606 conv(DoubleToStringConverter::NO_FLAGS,
607 "Infinity", "NaN", 'E',
608 detail::kConvMaxDecimalInShortestLow,
609 detail::kConvMaxDecimalInShortestHigh,
610 6, // max leading padding zeros
611 1); // max trailing padding zeros
613 StringBuilder builder(buffer, sizeof(buffer));
615 case DoubleToStringConverter::SHORTEST:
616 conv.ToShortest(value, &builder);
618 case DoubleToStringConverter::FIXED:
619 conv.ToFixed(value, numDigits, &builder);
622 CHECK(mode == DoubleToStringConverter::PRECISION);
623 conv.ToPrecision(value, numDigits, &builder);
626 const size_t length = builder.position();
628 result->append(buffer, length);
632 * As above, but for floating point
634 template <class Tgt, class Src>
635 typename std::enable_if<
636 std::is_floating_point<Src>::value
637 && IsSomeString<Tgt>::value>::type
638 toAppend(Src value, Tgt * result) {
640 value, result, double_conversion::DoubleToStringConverter::SHORTEST, 0);
644 * Upper bound of the length of the output from
645 * DoubleToStringConverter::ToShortest(double, StringBuilder*),
646 * as used in toAppend(double, string*).
649 typename std::enable_if<
650 std::is_floating_point<Src>::value, size_t>::type
651 estimateSpaceNeeded(Src value) {
652 // kBase10MaximalLength is 17. We add 1 for decimal point,
653 // e.g. 10.0/9 is 17 digits and 18 characters, including the decimal point.
654 constexpr int kMaxMantissaSpace =
655 double_conversion::DoubleToStringConverter::kBase10MaximalLength + 1;
656 // strlen("E-") + digits10(numeric_limits<double>::max_exponent10)
657 constexpr int kMaxExponentSpace = 2 + 3;
658 static const int kMaxPositiveSpace = std::max({
659 // E.g. 1.1111111111111111E-100.
660 kMaxMantissaSpace + kMaxExponentSpace,
661 // E.g. 0.000001.1111111111111111, if kConvMaxDecimalInShortestLow is -6.
662 kMaxMantissaSpace - detail::kConvMaxDecimalInShortestLow,
663 // If kConvMaxDecimalInShortestHigh is 21, then 1e21 is the smallest
664 // number > 1 which ToShortest outputs in exponential notation,
665 // so 21 is the longest non-exponential number > 1.
666 detail::kConvMaxDecimalInShortestHigh
668 return kMaxPositiveSpace + (value < 0); // +1 for minus sign, if negative
672 * This can be specialized, together with adding specialization
673 * for estimateSpaceNeed for your type, so that we allocate
674 * as much as you need instead of the default
677 struct HasLengthEstimator : std::false_type {};
680 constexpr typename std::enable_if<
681 !std::is_fundamental<Src>::value
682 #ifdef FOLLY_HAVE_INT128_T
683 // On OSX 10.10, is_fundamental<__int128> is false :-O
684 && !std::is_same<__int128, Src>::value
685 && !std::is_same<unsigned __int128, Src>::value
687 && !IsSomeString<Src>::value
688 && !std::is_convertible<Src, const char*>::value
689 && !std::is_convertible<Src, StringPiece>::value
690 && !std::is_enum<Src>::value
691 && !HasLengthEstimator<Src>::value,
693 estimateSpaceNeeded(const Src&) {
694 return sizeof(Src) + 1; // dumbest best effort ever?
699 inline size_t estimateSpaceToReserve(size_t sofar) {
703 template <class T, class... Ts>
704 size_t estimateSpaceToReserve(size_t sofar, const T& v, const Ts&... vs) {
705 return estimateSpaceToReserve(sofar + estimateSpaceNeeded(v), vs...);
709 size_t estimateSpaceToReserve(size_t sofar, const T& v) {
710 return sofar + estimateSpaceNeeded(v);
714 void reserveInTarget(const Ts&...vs) {
715 getLastElement(vs...)->reserve(estimateSpaceToReserve(0, vs...));
718 template<class Delimiter, class...Ts>
719 void reserveInTargetDelim(const Delimiter& d, const Ts&...vs) {
720 static_assert(sizeof...(vs) >= 2, "Needs at least 2 args");
721 size_t fordelim = (sizeof...(vs) - 2) * estimateSpaceToReserve(0, d);
722 getLastElement(vs...)->reserve(estimateSpaceToReserve(fordelim, vs...));
726 * Variadic base case: append one element
728 template <class T, class Tgt>
729 typename std::enable_if<
730 IsSomeString<typename std::remove_pointer<Tgt>::type>
732 toAppendStrImpl(const T& v, Tgt result) {
736 template <class T, class... Ts>
737 typename std::enable_if<sizeof...(Ts) >= 2
739 typename std::remove_pointer<
740 typename detail::last_element<Ts...>::type
741 >::type>::value>::type
742 toAppendStrImpl(const T& v, const Ts&... vs) {
743 toAppend(v, getLastElement(vs...));
744 toAppendStrImpl(vs...);
747 template <class Delimiter, class T, class Tgt>
748 typename std::enable_if<
749 IsSomeString<typename std::remove_pointer<Tgt>::type>
751 toAppendDelimStrImpl(const Delimiter& delim, const T& v, Tgt result) {
755 template <class Delimiter, class T, class... Ts>
756 typename std::enable_if<sizeof...(Ts) >= 2
758 typename std::remove_pointer<
759 typename detail::last_element<Ts...>::type
760 >::type>::value>::type
761 toAppendDelimStrImpl(const Delimiter& delim, const T& v, const Ts&... vs) {
762 // we are really careful here, calling toAppend with just one element does
763 // not try to estimate space needed (as we already did that). If we call
764 // toAppend(v, delim, ....) we would do unnecesary size calculation
765 toAppend(v, detail::getLastElement(vs...));
766 toAppend(delim, detail::getLastElement(vs...));
767 toAppendDelimStrImpl(delim, vs...);
773 * Variadic conversion to string. Appends each element in turn.
774 * If we have two or more things to append, we it will not reserve
775 * the space for them and will depend on strings exponential growth.
776 * If you just append once consider using toAppendFit which reserves
777 * the space needed (but does not have exponential as a result).
779 template <class... Ts>
780 typename std::enable_if<sizeof...(Ts) >= 3
782 typename std::remove_pointer<
783 typename detail::last_element<Ts...>::type
784 >::type>::value>::type
785 toAppend(const Ts&... vs) {
786 ::folly::detail::toAppendStrImpl(vs...);
790 * Special version of the call that preallocates exaclty as much memory
791 * as need for arguments to be stored in target. This means we are
792 * not doing exponential growth when we append. If you are using it
793 * in a loop you are aiming at your foot with a big perf-destroying
795 * On the other hand if you are appending to a string once, this
796 * will probably save a few calls to malloc.
798 template <class... Ts>
799 typename std::enable_if<
801 typename std::remove_pointer<
802 typename detail::last_element<Ts...>::type
803 >::type>::value>::type
804 toAppendFit(const Ts&... vs) {
805 ::folly::detail::reserveInTarget(vs...);
810 void toAppendFit(const Ts&) {}
813 * Variadic base case: do nothing.
816 typename std::enable_if<IsSomeString<Tgt>::value>::type
817 toAppend(Tgt* result) {
821 * Variadic base case: do nothing.
823 template <class Delimiter, class Tgt>
824 typename std::enable_if<IsSomeString<Tgt>::value>::type
825 toAppendDelim(const Delimiter& delim, Tgt* result) {
829 * 1 element: same as toAppend.
831 template <class Delimiter, class T, class Tgt>
832 typename std::enable_if<IsSomeString<Tgt>::value>::type
833 toAppendDelim(const Delimiter& delim, const T& v, Tgt* tgt) {
838 * Append to string with a delimiter in between elements. Check out
839 * comments for toAppend for details about memory allocation.
841 template <class Delimiter, class... Ts>
842 typename std::enable_if<sizeof...(Ts) >= 3
844 typename std::remove_pointer<
845 typename detail::last_element<Ts...>::type
846 >::type>::value>::type
847 toAppendDelim(const Delimiter& delim, const Ts&... vs) {
848 detail::toAppendDelimStrImpl(delim, vs...);
852 * Detail in comment for toAppendFit
854 template <class Delimiter, class... Ts>
855 typename std::enable_if<
857 typename std::remove_pointer<
858 typename detail::last_element<Ts...>::type
859 >::type>::value>::type
860 toAppendDelimFit(const Delimiter& delim, const Ts&... vs) {
861 detail::reserveInTargetDelim(delim, vs...);
862 toAppendDelim(delim, vs...);
865 template <class De, class Ts>
866 void toAppendDelimFit(const De&, const Ts&) {}
869 * to<SomeString>(v1, v2, ...) uses toAppend() (see below) as back-end
872 template <class Tgt, class... Ts>
873 typename std::enable_if<
874 IsSomeString<Tgt>::value && (
875 sizeof...(Ts) != 1 ||
876 !std::is_same<Tgt, typename detail::last_element<Ts...>::type>::value),
878 to(const Ts&... vs) {
880 toAppendFit(vs..., &result);
885 * toDelim<SomeString>(SomeString str) returns itself.
887 template <class Tgt, class Delim, class Src>
888 typename std::enable_if<
889 IsSomeString<Tgt>::value && std::is_same<Tgt, Src>::value,
891 toDelim(const Delim& delim, const Src & value) {
896 * toDelim<SomeString>(delim, v1, v2, ...) uses toAppendDelim() as
897 * back-end for all types.
899 template <class Tgt, class Delim, class... Ts>
900 typename std::enable_if<
901 IsSomeString<Tgt>::value && (
902 sizeof...(Ts) != 1 ||
903 !std::is_same<Tgt, typename detail::last_element<Ts...>::type>::value),
905 toDelim(const Delim& delim, const Ts&... vs) {
907 toAppendDelimFit(delim, vs..., &result);
911 /*******************************************************************************
912 * Conversions from string types to integral types.
913 ******************************************************************************/
918 * Finds the first non-digit in a string. The number of digits
919 * searched depends on the precision of the Tgt integral. Assumes the
920 * string starts with NO whitespace and NO sign.
922 * The semantics of the routine is:
924 * if (b >= e || !isdigit(*b)) return b;
927 * Complete unrolling marks bottom-line (i.e. entire conversion)
928 * improvements of 20%.
931 const char* findFirstNonDigit(const char* b, const char* e) {
933 auto const c = static_cast<unsigned>(*b) - '0';
939 // Maximum value of number when represented as a string
940 template <class T> struct MaxString {
941 static const char*const value;
944 bool str_to_bool(StringPiece* src);
947 Tgt digits_to(const char* b, const char* e);
949 extern template unsigned char digits_to<unsigned char>(const char* b,
951 extern template unsigned short digits_to<unsigned short>(const char* b,
953 extern template unsigned int digits_to<unsigned int>(const char* b,
955 extern template unsigned long digits_to<unsigned long>(const char* b,
957 extern template unsigned long long digits_to<unsigned long long>(
958 const char* b, const char* e);
959 #if FOLLY_HAVE_INT128_T
960 extern template unsigned __int128 digits_to<unsigned __int128>(const char* b,
964 } // namespace detail
967 * String represented as a pair of pointers to char to unsigned
968 * integrals. Assumes NO whitespace before or after.
971 typename std::enable_if<
972 std::is_integral<Tgt>::value && !std::is_signed<Tgt>::value
973 && !std::is_same<typename std::remove_cv<Tgt>::type, bool>::value,
975 to(const char * b, const char * e) {
976 return detail::digits_to<Tgt>(b, e);
980 * String represented as a pair of pointers to char to signed
981 * integrals. Assumes NO whitespace before or after. Allows an
982 * optional leading sign.
985 typename std::enable_if<
986 std::is_integral<Tgt>::value && std::is_signed<Tgt>::value,
988 to(const char * b, const char * e) {
989 FOLLY_RANGE_CHECK(b < e, "Empty input string in conversion to integral",
990 to<std::string>("b: ", intptr_t(b), " e: ", intptr_t(e)));
993 Tgt result = -to<typename std::make_unsigned<Tgt>::type>(b + 1, e);
994 FOLLY_RANGE_CHECK_BEGIN_END(result <= 0, "Negative overflow.", b, e);
997 FOLLY_RANGE_CHECK_BEGIN_END(*b == '+', "Invalid lead character", b, e);
1000 Tgt result = to<typename std::make_unsigned<Tgt>::type>(b, e);
1001 FOLLY_RANGE_CHECK_BEGIN_END(result >= 0, "Overflow", b, e);
1006 * Parsing strings to integrals. These routines differ from
1007 * to<integral>(string) in that they take a POINTER TO a StringPiece
1008 * and alter that StringPiece to reflect progress information.
1012 * StringPiece to integrals, with progress information. Alters the
1013 * StringPiece parameter to munch the already-parsed characters.
1015 template <class Tgt>
1016 typename std::enable_if<
1017 std::is_integral<Tgt>::value
1018 && !std::is_same<typename std::remove_cv<Tgt>::type, bool>::value,
1020 to(StringPiece * src) {
1022 auto b = src->data(), past = src->data() + src->size();
1024 FOLLY_RANGE_CHECK_STRINGPIECE(b < past,
1025 "No digits found in input string", *src);
1026 if (!isspace(*b)) break;
1031 // First digit is customized because we test for sign
1032 bool negative = false;
1033 /* static */ if (std::is_signed<Tgt>::value) {
1038 FOLLY_RANGE_CHECK_STRINGPIECE(*m == '+', "Invalid leading character in "
1039 "conversion to integral", *src);
1045 FOLLY_RANGE_CHECK_STRINGPIECE(m < past, "No digits found in input string",
1047 FOLLY_RANGE_CHECK_STRINGPIECE(isdigit(*m), "Non-digit character found", *src);
1048 m = detail::findFirstNonDigit<Tgt>(m + 1, past);
1051 /* static */ if (!std::is_signed<Tgt>::value) {
1052 result = detail::digits_to<typename std::make_unsigned<Tgt>::type>(b, m);
1054 auto t = detail::digits_to<typename std::make_unsigned<Tgt>::type>(b, m);
1057 FOLLY_RANGE_CHECK_STRINGPIECE(is_non_positive(result),
1058 "Negative overflow", *src);
1061 FOLLY_RANGE_CHECK_STRINGPIECE(is_non_negative(result), "Overflow", *src);
1064 src->advance(m - src->data());
1069 * StringPiece to bool, with progress information. Alters the
1070 * StringPiece parameter to munch the already-parsed characters.
1072 template <class Tgt>
1073 typename std::enable_if<
1074 std::is_same<typename std::remove_cv<Tgt>::type, bool>::value,
1076 to(StringPiece * src) {
1077 return detail::str_to_bool(src);
1083 * Enforce that the suffix following a number is made up only of whitespace.
1085 inline void enforceWhitespace(const char* b, const char* e) {
1086 for (; b != e; ++b) {
1087 FOLLY_RANGE_CHECK_BEGIN_END(isspace(*b),
1088 to<std::string>("Non-whitespace: ", *b),
1093 } // namespace detail
1096 * String or StringPiece to integrals. Accepts leading and trailing
1097 * whitespace, but no non-space trailing characters.
1099 template <class Tgt>
1100 typename std::enable_if<
1101 std::is_integral<Tgt>::value,
1103 to(StringPiece src) {
1104 Tgt result = to<Tgt>(&src);
1105 detail::enforceWhitespace(src.data(), src.data() + src.size());
1109 /*******************************************************************************
1110 * Conversions from string types to floating-point types.
1111 ******************************************************************************/
1114 * StringPiece to double, with progress information. Alters the
1115 * StringPiece parameter to munch the already-parsed characters.
1117 template <class Tgt>
1118 inline typename std::enable_if<
1119 std::is_floating_point<Tgt>::value,
1121 to(StringPiece *const src) {
1122 using namespace double_conversion;
1123 static StringToDoubleConverter
1124 conv(StringToDoubleConverter::ALLOW_TRAILING_JUNK
1125 | StringToDoubleConverter::ALLOW_LEADING_SPACES,
1127 // return this for junk input string
1128 std::numeric_limits<double>::quiet_NaN(),
1131 FOLLY_RANGE_CHECK_STRINGPIECE(!src->empty(),
1132 "No digits found in input string", *src);
1135 auto result = conv.StringToDouble(src->data(),
1136 static_cast<int>(src->size()),
1137 &length); // processed char count
1139 if (!std::isnan(result)) {
1140 src->advance(length);
1144 for (;; src->advance(1)) {
1146 throw std::range_error("Unable to convert an empty string"
1147 " to a floating point value.");
1149 if (!isspace(src->front())) {
1154 // Was that "inf[inity]"?
1155 if (src->size() >= 3 && toupper((*src)[0]) == 'I'
1156 && toupper((*src)[1]) == 'N' && toupper((*src)[2]) == 'F') {
1157 if (src->size() >= 8 &&
1158 toupper((*src)[3]) == 'I' &&
1159 toupper((*src)[4]) == 'N' &&
1160 toupper((*src)[5]) == 'I' &&
1161 toupper((*src)[6]) == 'T' &&
1162 toupper((*src)[7]) == 'Y') {
1167 return std::numeric_limits<Tgt>::infinity();
1170 // Was that "-inf[inity]"?
1171 if (src->size() >= 4 && toupper((*src)[0]) == '-'
1172 && toupper((*src)[1]) == 'I' && toupper((*src)[2]) == 'N'
1173 && toupper((*src)[3]) == 'F') {
1174 if (src->size() >= 9 &&
1175 toupper((*src)[4]) == 'I' &&
1176 toupper((*src)[5]) == 'N' &&
1177 toupper((*src)[6]) == 'I' &&
1178 toupper((*src)[7]) == 'T' &&
1179 toupper((*src)[8]) == 'Y') {
1184 return -std::numeric_limits<Tgt>::infinity();
1188 if (src->size() >= 3 && toupper((*src)[0]) == 'N'
1189 && toupper((*src)[1]) == 'A' && toupper((*src)[2]) == 'N') {
1191 return std::numeric_limits<Tgt>::quiet_NaN();
1195 if (src->size() >= 4 &&
1196 toupper((*src)[0]) == '-' &&
1197 toupper((*src)[1]) == 'N' &&
1198 toupper((*src)[2]) == 'A' &&
1199 toupper((*src)[3]) == 'N') {
1201 return -std::numeric_limits<Tgt>::quiet_NaN();
1205 throw std::range_error("Unable to convert \"" + src->toString()
1206 + "\" to a floating point value.");
1210 * Any string, const char*, or StringPiece to double.
1212 template <class Tgt>
1213 typename std::enable_if<
1214 std::is_floating_point<Tgt>::value,
1216 to(StringPiece src) {
1217 Tgt result = to<double>(&src);
1218 detail::enforceWhitespace(src.data(), src.data() + src.size());
1222 /*******************************************************************************
1223 * Integral to floating point and back
1224 ******************************************************************************/
1227 * Checked conversion from integral to flating point and back. The
1228 * result must be convertible back to the source type without loss of
1229 * precision. This seems Draconian but sometimes is what's needed, and
1230 * complements existing routines nicely. For various rounding
1231 * routines, see <math>.
1233 template <class Tgt, class Src>
1234 typename std::enable_if<
1235 (std::is_integral<Src>::value && std::is_floating_point<Tgt>::value)
1237 (std::is_floating_point<Src>::value && std::is_integral<Tgt>::value),
1239 to(const Src & value) {
1241 auto witness = static_cast<Src>(result);
1242 if (value != witness) {
1243 throw std::range_error(
1244 to<std::string>("to<>: loss of precision when converting ", value,
1245 #ifdef FOLLY_HAS_RTTI
1246 " to type ", typeid(Tgt).name()
1255 /*******************************************************************************
1256 * Enum to anything and back
1257 ******************************************************************************/
1259 template <class Tgt, class Src>
1260 typename std::enable_if<
1261 std::is_enum<Src>::value && !std::is_same<Src, Tgt>::value, Tgt>::type
1262 to(const Src & value) {
1263 return to<Tgt>(static_cast<typename std::underlying_type<Src>::type>(value));
1266 template <class Tgt, class Src>
1267 typename std::enable_if<
1268 std::is_enum<Tgt>::value && !std::is_same<Src, Tgt>::value, Tgt>::type
1269 to(const Src & value) {
1270 return static_cast<Tgt>(to<typename std::underlying_type<Tgt>::type>(value));
1273 } // namespace folly
1275 // FOLLY_CONV_INTERNAL is defined by Conv.cpp. Keep the FOLLY_RANGE_CHECK
1276 // macro for use in Conv.cpp, but #undefine it everywhere else we are included,
1277 // to avoid defining this global macro name in other files that include Conv.h.
1278 #ifndef FOLLY_CONV_INTERNAL
1279 #undef FOLLY_RANGE_CHECK
1280 #undef FOLLY_RANGE_CHECK_BEGIN_END
1281 #undef FOLLY_RANGE_CHECK_STRINGPIECE
1282 #undef FOLLY_RANGE_CHECK_STRINGIZE
1283 #undef FOLLY_RANGE_CHECK_STRINGIZE2
1286 #endif /* FOLLY_BASE_CONV_H_ */