proxygen
String.cpp
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1 /*
2  * Copyright 2012-present Facebook, Inc.
3  *
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
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
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.
15  */
16 
17 #include <folly/String.h>
18 
19 #include <cctype>
20 #include <cerrno>
21 #include <cstdarg>
22 #include <cstring>
23 #include <iterator>
24 #include <sstream>
25 #include <stdexcept>
26 
27 #include <glog/logging.h>
28 
29 #include <folly/Portability.h>
30 #include <folly/ScopeGuard.h>
31 #include <folly/container/Array.h>
32 
33 namespace folly {
34 
35 static_assert(IsConvertible<float>::value, "");
36 static_assert(IsConvertible<int>::value, "");
37 static_assert(IsConvertible<bool>::value, "");
38 static_assert(IsConvertible<int>::value, "");
39 static_assert(!IsConvertible<std::vector<int>>::value, "");
40 
41 namespace detail {
42 
44  constexpr char operator()(std::size_t index) const {
45  // clang-format off
46  return
47  index == '"' ? '"' :
48  index == '\\' ? '\\' :
49  index == '?' ? '?' :
50  index == '\n' ? 'n' :
51  index == '\r' ? 'r' :
52  index == '\t' ? 't' :
53  index < 32 || index > 126 ? 'O' : // octal
54  'P'; // printable
55  // clang-format on
56  }
57 };
58 
60  constexpr char operator()(std::size_t index) const {
61  // clang-format off
62  return
63  index == '\'' ? '\'' :
64  index == '?' ? '?' :
65  index == '\\' ? '\\' :
66  index == '"' ? '"' :
67  index == 'a' ? '\a' :
68  index == 'b' ? '\b' :
69  index == 'f' ? '\f' :
70  index == 'n' ? '\n' :
71  index == 'r' ? '\r' :
72  index == 't' ? '\t' :
73  index == 'v' ? '\v' :
74  index >= '0' && index <= '7' ? 'O' : // octal
75  index == 'x' ? 'X' : // hex
76  'I'; // invalid
77  // clang-format on
78  }
79 };
80 
82  constexpr unsigned char operator()(std::size_t index) const {
83  // clang-format off
84  return
85  index >= '0' && index <= '9' ? index - '0' :
86  index >= 'a' && index <= 'f' ? index - 'a' + 10 :
87  index >= 'A' && index <= 'F' ? index - 'A' + 10 :
88  16;
89  // clang-format on
90  }
91 };
92 
94  // 0 = passthrough
95  // 1 = unused
96  // 2 = safe in path (/)
97  // 3 = space (replace with '+' in query)
98  // 4 = always percent-encode
99  constexpr unsigned char operator()(std::size_t index) const {
100  // clang-format off
101  return
102  index >= '0' && index <= '9' ? 0 :
103  index >= 'A' && index <= 'Z' ? 0 :
104  index >= 'a' && index <= 'z' ? 0 :
105  index == '-' ? 0 :
106  index == '_' ? 0 :
107  index == '.' ? 0 :
108  index == '~' ? 0 :
109  index == '/' ? 2 :
110  index == ' ' ? 3 :
111  4;
112  // clang-format on
113  }
114 };
115 
124 
125 } // namespace detail
126 
127 static inline bool is_oddspace(char c) {
128  return c == '\n' || c == '\t' || c == '\r';
129 }
130 
132  // Spaces other than ' ' characters are less common but should be
133  // checked. This configuration where we loop on the ' '
134  // separately from oddspaces was empirically fastest.
135 
136  while (true) {
137  while (!sp.empty() && sp.front() == ' ') {
138  sp.pop_front();
139  }
140  if (!sp.empty() && is_oddspace(sp.front())) {
141  sp.pop_front();
142  continue;
143  }
144 
145  return sp;
146  }
147 }
148 
150  // Spaces other than ' ' characters are less common but should be
151  // checked. This configuration where we loop on the ' '
152  // separately from oddspaces was empirically fastest.
153 
154  while (true) {
155  while (!sp.empty() && sp.back() == ' ') {
156  sp.pop_back();
157  }
158  if (!sp.empty() && is_oddspace(sp.back())) {
159  sp.pop_back();
160  continue;
161  }
162 
163  return sp;
164  }
165 }
166 
167 namespace {
168 
169 int stringAppendfImplHelper(
170  char* buf,
171  size_t bufsize,
172  const char* format,
173  va_list args) {
174  va_list args_copy;
175  va_copy(args_copy, args);
176  int bytes_used = vsnprintf(buf, bufsize, format, args_copy);
177  va_end(args_copy);
178  return bytes_used;
179 }
180 
181 void stringAppendfImpl(std::string& output, const char* format, va_list args) {
182  // Very simple; first, try to avoid an allocation by using an inline
183  // buffer. If that fails to hold the output string, allocate one on
184  // the heap, use it instead.
185  //
186  // It is hard to guess the proper size of this buffer; some
187  // heuristics could be based on the number of format characters, or
188  // static analysis of a codebase. Or, we can just pick a number
189  // that seems big enough for simple cases (say, one line of text on
190  // a terminal) without being large enough to be concerning as a
191  // stack variable.
192  std::array<char, 128> inline_buffer;
193 
194  int bytes_used = stringAppendfImplHelper(
195  inline_buffer.data(), inline_buffer.size(), format, args);
196  if (bytes_used < 0) {
197  throw std::runtime_error(to<std::string>(
198  "Invalid format string; snprintf returned negative "
199  "with format string: ",
200  format));
201  }
202 
203  if (static_cast<size_t>(bytes_used) < inline_buffer.size()) {
204  output.append(inline_buffer.data(), size_t(bytes_used));
205  return;
206  }
207 
208  // Couldn't fit. Heap allocate a buffer, oh well.
209  std::unique_ptr<char[]> heap_buffer(new char[size_t(bytes_used + 1)]);
210  int final_bytes_used = stringAppendfImplHelper(
211  heap_buffer.get(), size_t(bytes_used + 1), format, args);
212  // The second call can take fewer bytes if, for example, we were printing a
213  // string buffer with null-terminating char using a width specifier -
214  // vsnprintf("%.*s", buf.size(), buf)
215  CHECK(bytes_used >= final_bytes_used);
216 
217  // We don't keep the trailing '\0' in our output string
218  output.append(heap_buffer.get(), size_t(final_bytes_used));
219 }
220 
221 } // namespace
222 
223 std::string stringPrintf(const char* format, ...) {
224  va_list ap;
225  va_start(ap, format);
226  SCOPE_EXIT {
227  va_end(ap);
228  };
229  return stringVPrintf(format, ap);
230 }
231 
232 std::string stringVPrintf(const char* format, va_list ap) {
233  std::string ret;
234  stringAppendfImpl(ret, format, ap);
235  return ret;
236 }
237 
238 // Basic declarations; allow for parameters of strings and string
239 // pieces to be specified.
241  va_list ap;
242  va_start(ap, format);
243  SCOPE_EXIT {
244  va_end(ap);
245  };
246  return stringVAppendf(output, format, ap);
247 }
248 
250 stringVAppendf(std::string* output, const char* format, va_list ap) {
251  stringAppendfImpl(*output, format, ap);
252  return *output;
253 }
254 
255 void stringPrintf(std::string* output, const char* format, ...) {
256  va_list ap;
257  va_start(ap, format);
258  SCOPE_EXIT {
259  va_end(ap);
260  };
261  return stringVPrintf(output, format, ap);
262 }
263 
264 void stringVPrintf(std::string* output, const char* format, va_list ap) {
265  output->clear();
266  stringAppendfImpl(*output, format, ap);
267 }
268 
269 namespace {
270 
271 struct PrettySuffix {
272  const char* suffix;
273  double val;
274 };
275 
276 const PrettySuffix kPrettyTimeSuffixes[] = {
277  {"s ", 1e0L},
278  {"ms", 1e-3L},
279  {"us", 1e-6L},
280  {"ns", 1e-9L},
281  {"ps", 1e-12L},
282  {"s ", 0},
283  {nullptr, 0},
284 };
285 
286 const PrettySuffix kPrettyTimeHmsSuffixes[] = {
287  {"h ", 60L * 60L},
288  {"m ", 60L},
289  {"s ", 1e0L},
290  {"ms", 1e-3L},
291  {"us", 1e-6L},
292  {"ns", 1e-9L},
293  {"ps", 1e-12L},
294  {"s ", 0},
295  {nullptr, 0},
296 };
297 
298 const PrettySuffix kPrettyBytesMetricSuffixes[] = {
299  {"EB", 1e18L},
300  {"PB", 1e15L},
301  {"TB", 1e12L},
302  {"GB", 1e9L},
303  {"MB", 1e6L},
304  {"kB", 1e3L},
305  {"B ", 0L},
306  {nullptr, 0},
307 };
308 
309 const PrettySuffix kPrettyBytesBinarySuffixes[] = {
310  {"EB", int64_t(1) << 60},
311  {"PB", int64_t(1) << 50},
312  {"TB", int64_t(1) << 40},
313  {"GB", int64_t(1) << 30},
314  {"MB", int64_t(1) << 20},
315  {"kB", int64_t(1) << 10},
316  {"B ", 0L},
317  {nullptr, 0},
318 };
319 
320 const PrettySuffix kPrettyBytesBinaryIECSuffixes[] = {
321  {"EiB", int64_t(1) << 60},
322  {"PiB", int64_t(1) << 50},
323  {"TiB", int64_t(1) << 40},
324  {"GiB", int64_t(1) << 30},
325  {"MiB", int64_t(1) << 20},
326  {"KiB", int64_t(1) << 10},
327  {"B ", 0L},
328  {nullptr, 0},
329 };
330 
331 const PrettySuffix kPrettyUnitsMetricSuffixes[] = {
332  {"qntl", 1e18L},
333  {"qdrl", 1e15L},
334  {"tril", 1e12L},
335  {"bil", 1e9L},
336  {"M", 1e6L},
337  {"k", 1e3L},
338  {" ", 0},
339  {nullptr, 0},
340 };
341 
342 const PrettySuffix kPrettyUnitsBinarySuffixes[] = {
343  {"E", int64_t(1) << 60},
344  {"P", int64_t(1) << 50},
345  {"T", int64_t(1) << 40},
346  {"G", int64_t(1) << 30},
347  {"M", int64_t(1) << 20},
348  {"k", int64_t(1) << 10},
349  {" ", 0},
350  {nullptr, 0},
351 };
352 
353 const PrettySuffix kPrettyUnitsBinaryIECSuffixes[] = {
354  {"Ei", int64_t(1) << 60},
355  {"Pi", int64_t(1) << 50},
356  {"Ti", int64_t(1) << 40},
357  {"Gi", int64_t(1) << 30},
358  {"Mi", int64_t(1) << 20},
359  {"Ki", int64_t(1) << 10},
360  {" ", 0},
361  {nullptr, 0},
362 };
363 
364 const PrettySuffix kPrettySISuffixes[] = {
365  {"Y", 1e24L}, {"Z", 1e21L}, {"E", 1e18L}, {"P", 1e15L}, {"T", 1e12L},
366  {"G", 1e9L}, {"M", 1e6L}, {"k", 1e3L}, {"h", 1e2L}, {"da", 1e1L},
367  {"d", 1e-1L}, {"c", 1e-2L}, {"m", 1e-3L}, {"u", 1e-6L}, {"n", 1e-9L},
368  {"p", 1e-12L}, {"f", 1e-15L}, {"a", 1e-18L}, {"z", 1e-21L}, {"y", 1e-24L},
369  {" ", 0}, {nullptr, 0},
370 };
371 
372 const PrettySuffix* const kPrettySuffixes[PRETTY_NUM_TYPES] = {
373  kPrettyTimeSuffixes,
374  kPrettyTimeHmsSuffixes,
375  kPrettyBytesMetricSuffixes,
376  kPrettyBytesBinarySuffixes,
377  kPrettyBytesBinaryIECSuffixes,
378  kPrettyUnitsMetricSuffixes,
379  kPrettyUnitsBinarySuffixes,
380  kPrettyUnitsBinaryIECSuffixes,
381  kPrettySISuffixes,
382 };
383 
384 } // namespace
385 
386 std::string prettyPrint(double val, PrettyType type, bool addSpace) {
387  char buf[100];
388 
389  // pick the suffixes to use
390  assert(type >= 0);
391  assert(type < PRETTY_NUM_TYPES);
392  const PrettySuffix* suffixes = kPrettySuffixes[type];
393 
394  // find the first suffix we're bigger than -- then use it
395  double abs_val = fabs(val);
396  for (int i = 0; suffixes[i].suffix; ++i) {
397  if (abs_val >= suffixes[i].val) {
398  snprintf(
399  buf,
400  sizeof buf,
401  "%.4g%s%s",
402  (suffixes[i].val ? (val / suffixes[i].val) : val),
403  (addSpace ? " " : ""),
404  suffixes[i].suffix);
405  return std::string(buf);
406  }
407  }
408 
409  // no suffix, we've got a tiny value -- just print it in sci-notation
410  snprintf(buf, sizeof buf, "%.4g", val);
411  return std::string(buf);
412 }
413 
414 // TODO:
415 // 1) Benchmark & optimize
417  folly::StringPiece* const prettyString,
418  const PrettyType type) {
419  double value = folly::to<double>(prettyString);
420  while (prettyString->size() > 0 && std::isspace(prettyString->front())) {
421  prettyString->advance(1); // Skipping spaces between number and suffix
422  }
423  const PrettySuffix* suffixes = kPrettySuffixes[type];
424  int longestPrefixLen = -1;
425  int bestPrefixId = -1;
426  for (int j = 0; suffixes[j].suffix; ++j) {
427  if (suffixes[j].suffix[0] == ' ') { // Checking for " " -> number rule.
428  if (longestPrefixLen == -1) {
429  longestPrefixLen = 0; // No characters to skip
430  bestPrefixId = j;
431  }
432  } else if (prettyString->startsWith(suffixes[j].suffix)) {
433  int suffixLen = int(strlen(suffixes[j].suffix));
434  // We are looking for a longest suffix matching prefix of the string
435  // after numeric value. We need this in case suffixes have common prefix.
436  if (suffixLen > longestPrefixLen) {
437  longestPrefixLen = suffixLen;
438  bestPrefixId = j;
439  }
440  }
441  }
442  if (bestPrefixId == -1) { // No valid suffix rule found
443  throw std::invalid_argument(folly::to<std::string>(
444  "Unable to parse suffix \"", *prettyString, "\""));
445  }
446  prettyString->advance(size_t(longestPrefixLen));
447  return suffixes[bestPrefixId].val ? value * suffixes[bestPrefixId].val
448  : value;
449 }
450 
451 double prettyToDouble(folly::StringPiece prettyString, const PrettyType type) {
452  double result = prettyToDouble(&prettyString, type);
453  detail::enforceWhitespace(prettyString);
454  return result;
455 }
456 
457 std::string hexDump(const void* ptr, size_t size) {
458  std::ostringstream os;
459  hexDump(ptr, size, std::ostream_iterator<StringPiece>(os, "\n"));
460  return os.str();
461 }
462 
463 fbstring errnoStr(int err) {
464  int savedErrno = errno;
465 
466  // Ensure that we reset errno upon exit.
467  auto guard(makeGuard([&] { errno = savedErrno; }));
468 
469  char buf[1024];
470  buf[0] = '\0';
471 
472  fbstring result;
473 
474  // https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/strerror_r.3.html
475  // http://www.kernel.org/doc/man-pages/online/pages/man3/strerror.3.html
476 #if defined(_WIN32) && (defined(__MINGW32__) || defined(_MSC_VER))
477  // mingw64 has no strerror_r, but Windows has strerror_s, which C11 added
478  // as well. So maybe we should use this across all platforms (together
479  // with strerrorlen_s). Note strerror_r and _s have swapped args.
480  int r = strerror_s(buf, sizeof(buf), err);
481  if (r != 0) {
482  result = to<fbstring>(
483  "Unknown error ", err, " (strerror_r failed with error ", errno, ")");
484  } else {
485  result.assign(buf);
486  }
487 #elif FOLLY_HAVE_XSI_STRERROR_R || defined(__APPLE__)
488 
489  // Using XSI-compatible strerror_r
490  int r = strerror_r(err, buf, sizeof(buf));
491 
492  // OSX/FreeBSD use EINVAL and Linux uses -1 so just check for non-zero
493  if (r != 0) {
494  result = to<fbstring>(
495  "Unknown error ", err, " (strerror_r failed with error ", errno, ")");
496  } else {
497  result.assign(buf);
498  }
499 #else
500  // Using GNU strerror_r
501  result.assign(strerror_r(err, buf, sizeof(buf)));
502 #endif
503 
504  return result;
505 }
506 
507 namespace {
508 
509 void toLowerAscii8(char& c) {
510  // Branchless tolower, based on the input-rotating trick described
511  // at http://www.azillionmonkeys.com/qed/asmexample.html
512  //
513  // This algorithm depends on an observation: each uppercase
514  // ASCII character can be converted to its lowercase equivalent
515  // by adding 0x20.
516 
517  // Step 1: Clear the high order bit. We'll deal with it in Step 5.
518  uint8_t rotated = uint8_t(c & 0x7f);
519  // Currently, the value of rotated, as a function of the original c is:
520  // below 'A': 0- 64
521  // 'A'-'Z': 65- 90
522  // above 'Z': 91-127
523 
524  // Step 2: Add 0x25 (37)
525  rotated += 0x25;
526  // Now the value of rotated, as a function of the original c is:
527  // below 'A': 37-101
528  // 'A'-'Z': 102-127
529  // above 'Z': 128-164
530 
531  // Step 3: clear the high order bit
532  rotated &= 0x7f;
533  // below 'A': 37-101
534  // 'A'-'Z': 102-127
535  // above 'Z': 0- 36
536 
537  // Step 4: Add 0x1a (26)
538  rotated += 0x1a;
539  // below 'A': 63-127
540  // 'A'-'Z': 128-153
541  // above 'Z': 25- 62
542 
543  // At this point, note that only the uppercase letters have been
544  // transformed into values with the high order bit set (128 and above).
545 
546  // Step 5: Shift the high order bit 2 spaces to the right: the spot
547  // where the only 1 bit in 0x20 is. But first, how we ignored the
548  // high order bit of the original c in step 1? If that bit was set,
549  // we may have just gotten a false match on a value in the range
550  // 128+'A' to 128+'Z'. To correct this, need to clear the high order
551  // bit of rotated if the high order bit of c is set. Since we don't
552  // care about the other bits in rotated, the easiest thing to do
553  // is invert all the bits in c and bitwise-and them with rotated.
554  rotated &= ~c;
555  rotated >>= 2;
556 
557  // Step 6: Apply a mask to clear everything except the 0x20 bit
558  // in rotated.
559  rotated &= 0x20;
560 
561  // At this point, rotated is 0x20 if c is 'A'-'Z' and 0x00 otherwise
562 
563  // Step 7: Add rotated to c
564  c += char(rotated);
565 }
566 
567 void toLowerAscii32(uint32_t& c) {
568  // Besides being branchless, the algorithm in toLowerAscii8() has another
569  // interesting property: None of the addition operations will cause
570  // an overflow in the 8-bit value. So we can pack four 8-bit values
571  // into a uint32_t and run each operation on all four values in parallel
572  // without having to use any CPU-specific SIMD instructions.
573  uint32_t rotated = c & uint32_t(0x7f7f7f7fL);
574  rotated += uint32_t(0x25252525L);
575  rotated &= uint32_t(0x7f7f7f7fL);
576  rotated += uint32_t(0x1a1a1a1aL);
577 
578  // Step 5 involves a shift, so some bits will spill over from each
579  // 8-bit value into the next. But that's okay, because they're bits
580  // that will be cleared by the mask in step 6 anyway.
581  rotated &= ~c;
582  rotated >>= 2;
583  rotated &= uint32_t(0x20202020L);
584  c += rotated;
585 }
586 
587 void toLowerAscii64(uint64_t& c) {
588  // 64-bit version of toLower32
589  uint64_t rotated = c & uint64_t(0x7f7f7f7f7f7f7f7fL);
590  rotated += uint64_t(0x2525252525252525L);
591  rotated &= uint64_t(0x7f7f7f7f7f7f7f7fL);
592  rotated += uint64_t(0x1a1a1a1a1a1a1a1aL);
593  rotated &= ~c;
594  rotated >>= 2;
595  rotated &= uint64_t(0x2020202020202020L);
596  c += rotated;
597 }
598 
599 } // namespace
600 
601 void toLowerAscii(char* str, size_t length) {
602  static const size_t kAlignMask64 = 7;
603  static const size_t kAlignMask32 = 3;
604 
605  // Convert a character at a time until we reach an address that
606  // is at least 32-bit aligned
607  size_t n = (size_t)str;
608  n &= kAlignMask32;
609  n = std::min(n, length);
610  size_t offset = 0;
611  if (n != 0) {
612  n = std::min(4 - n, length);
613  do {
614  toLowerAscii8(str[offset]);
615  offset++;
616  } while (offset < n);
617  }
618 
619  n = (size_t)(str + offset);
620  n &= kAlignMask64;
621  if ((n != 0) && (offset + 4 <= length)) {
622  // The next address is 32-bit aligned but not 64-bit aligned.
623  // Convert the next 4 bytes in order to get to the 64-bit aligned
624  // part of the input.
625  toLowerAscii32(*(uint32_t*)(str + offset));
626  offset += 4;
627  }
628 
629  // Convert 8 characters at a time
630  while (offset + 8 <= length) {
631  toLowerAscii64(*(uint64_t*)(str + offset));
632  offset += 8;
633  }
634 
635  // Convert 4 characters at a time
636  while (offset + 4 <= length) {
637  toLowerAscii32(*(uint32_t*)(str + offset));
638  offset += 4;
639  }
640 
641  // Convert any characters remaining after the last 4-byte aligned group
642  while (offset < length) {
643  toLowerAscii8(str[offset]);
644  offset++;
645  }
646 }
647 
648 namespace detail {
649 
650 size_t
651 hexDumpLine(const void* ptr, size_t offset, size_t size, std::string& line) {
652  static char hexValues[] = "0123456789abcdef";
653  // Line layout:
654  // 8: address
655  // 1: space
656  // (1+2)*16: hex bytes, each preceded by a space
657  // 1: space separating the two halves
658  // 3: " |"
659  // 16: characters
660  // 1: "|"
661  // Total: 78
662  line.clear();
663  line.reserve(78);
664  const uint8_t* p = reinterpret_cast<const uint8_t*>(ptr) + offset;
665  size_t n = std::min(size - offset, size_t(16));
666  line.push_back(hexValues[(offset >> 28) & 0xf]);
667  line.push_back(hexValues[(offset >> 24) & 0xf]);
668  line.push_back(hexValues[(offset >> 20) & 0xf]);
669  line.push_back(hexValues[(offset >> 16) & 0xf]);
670  line.push_back(hexValues[(offset >> 12) & 0xf]);
671  line.push_back(hexValues[(offset >> 8) & 0xf]);
672  line.push_back(hexValues[(offset >> 4) & 0xf]);
673  line.push_back(hexValues[offset & 0xf]);
674  line.push_back(' ');
675 
676  for (size_t i = 0; i < n; i++) {
677  if (i == 8) {
678  line.push_back(' ');
679  }
680 
681  line.push_back(' ');
682  line.push_back(hexValues[(p[i] >> 4) & 0xf]);
683  line.push_back(hexValues[p[i] & 0xf]);
684  }
685 
686  // 3 spaces for each byte we're not printing, one separating the halves
687  // if necessary
688  line.append(3 * (16 - n) + (n <= 8), ' ');
689  line.append(" |");
690 
691  for (size_t i = 0; i < n; i++) {
692  char c = (p[i] >= 32 && p[i] <= 126 ? static_cast<char>(p[i]) : '.');
693  line.push_back(c);
694  }
695  line.append(16 - n, ' ');
696  line.push_back('|');
697  DCHECK_EQ(line.size(), 78u);
698 
699  return n;
700 }
701 
702 } // namespace detail
703 
705  std::vector<StringPiece> pieces;
706  split("\n", s, pieces);
707  auto piecer = range(pieces);
708 
709  auto piece = (piecer.end() - 1);
710  auto needle = std::find_if(piece->begin(), piece->end(), [](char c) {
711  return c != ' ' && c != '\t';
712  });
713  if (needle == piece->end()) {
714  (piecer.end() - 1)->clear();
715  }
716  piece = piecer.begin();
717  needle = std::find_if(piece->begin(), piece->end(), [](char c) {
718  return c != ' ' && c != '\t';
719  });
720  if (needle == piece->end()) {
721  piecer.erase(piecer.begin(), piecer.begin() + 1);
722  }
723 
724  const auto sentinel = std::numeric_limits<size_t>::max();
725  auto indent = sentinel;
726  size_t max_length = 0;
727  for (piece = piecer.begin(); piece != piecer.end(); piece++) {
728  needle = std::find_if(piece->begin(), piece->end(), [](char c) {
729  return c != ' ' && c != '\t';
730  });
731  if (needle != piece->end()) {
732  indent = std::min<size_t>(indent, size_t(needle - piece->begin()));
733  } else {
734  max_length = std::max<size_t>(piece->size(), max_length);
735  }
736  }
737  indent = indent == sentinel ? max_length : indent;
738  for (piece = piecer.begin(); piece != piecer.end(); piece++) {
739  if (piece->size() < indent) {
740  piece->clear();
741  } else {
742  piece->erase(piece->begin(), piece->begin() + indent);
743  }
744  }
745  return join("\n", piecer);
746 }
747 
748 } // namespace folly
749 
750 #ifdef FOLLY_DEFINED_DMGL
751 #undef FOLLY_DEFINED_DMGL
752 #undef DMGL_NO_OPTS
753 #undef DMGL_PARAMS
754 #undef DMGL_ANSI
755 #undef DMGL_JAVA
756 #undef DMGL_VERBOSE
757 #undef DMGL_TYPES
758 #undef DMGL_RET_POSTFIX
759 #endif
const string needle
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—— Concurrent Priority Queue Implementation ——
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constexpr char operator()(std::size_t index) const
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FOLLY_NODISCARD detail::ScopeGuardImplDecay< F, true > makeGuard(F &&f) noexcept(noexcept(detail::ScopeGuardImplDecay< F, true >(static_cast< F && >(f))))
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constexpr auto make_array_with(MakeItem const &make)
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