summaryrefslogtreecommitdiff
path: root/absl/strings/escaping.cc
blob: c8f18d86079829386f0e59d209c3b1dde6b49ba0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "absl/strings/escaping.h"

#include <algorithm>
#include <cassert>
#include <cstdint>
#include <cstring>
#include <iterator>
#include <limits>
#include <string>

#include "absl/base/internal/endian.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/base/internal/unaligned_access.h"
#include "absl/strings/internal/char_map.h"
#include "absl/strings/internal/resize_uninitialized.h"
#include "absl/strings/internal/utf8.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/str_join.h"
#include "absl/strings/string_view.h"

namespace absl {
namespace {

// Digit conversion.
constexpr char kHexChar[] = "0123456789abcdef";

constexpr char kHexTable[513] =
    "000102030405060708090a0b0c0d0e0f"
    "101112131415161718191a1b1c1d1e1f"
    "202122232425262728292a2b2c2d2e2f"
    "303132333435363738393a3b3c3d3e3f"
    "404142434445464748494a4b4c4d4e4f"
    "505152535455565758595a5b5c5d5e5f"
    "606162636465666768696a6b6c6d6e6f"
    "707172737475767778797a7b7c7d7e7f"
    "808182838485868788898a8b8c8d8e8f"
    "909192939495969798999a9b9c9d9e9f"
    "a0a1a2a3a4a5a6a7a8a9aaabacadaeaf"
    "b0b1b2b3b4b5b6b7b8b9babbbcbdbebf"
    "c0c1c2c3c4c5c6c7c8c9cacbcccdcecf"
    "d0d1d2d3d4d5d6d7d8d9dadbdcdddedf"
    "e0e1e2e3e4e5e6e7e8e9eaebecedeeef"
    "f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff";

// These are used for the leave_nulls_escaped argument to CUnescapeInternal().
constexpr bool kUnescapeNulls = false;

inline bool is_octal_digit(char c) { return ('0' <= c) && (c <= '7'); }

inline int hex_digit_to_int(char c) {
  static_assert('0' == 0x30 && 'A' == 0x41 && 'a' == 0x61,
                "Character set must be ASCII.");
  assert(absl::ascii_isxdigit(c));
  int x = static_cast<unsigned char>(c);
  if (x > '9') {
    x += 9;
  }
  return x & 0xf;
}

inline bool IsSurrogate(char32_t c, absl::string_view src, std::string* error) {
  if (c >= 0xD800 && c <= 0xDFFF) {
    if (error) {
      *error = absl::StrCat("invalid surrogate character (0xD800-DFFF): \\",
                            src);
    }
    return true;
  }
  return false;
}

// ----------------------------------------------------------------------
// CUnescapeInternal()
//    Implements both CUnescape() and CUnescapeForNullTerminatedString().
//
//    Unescapes C escape sequences and is the reverse of CEscape().
//
//    If 'source' is valid, stores the unescaped string and its size in
//    'dest' and 'dest_len' respectively, and returns true. Otherwise
//    returns false and optionally stores the error description in
//    'error'. Set 'error' to nullptr to disable error reporting.
//
//    'dest' should point to a buffer that is at least as big as 'source'.
//    'source' and 'dest' may be the same.
//
//     NOTE: any changes to this function must also be reflected in the older
//     UnescapeCEscapeSequences().
// ----------------------------------------------------------------------
bool CUnescapeInternal(absl::string_view source, bool leave_nulls_escaped,
                       char* dest, ptrdiff_t* dest_len, std::string* error) {
  char* d = dest;
  const char* p = source.data();
  const char* end = source.end();
  const char* last_byte = end - 1;

  // Small optimization for case where source = dest and there's no escaping
  while (p == d && p < end && *p != '\\') p++, d++;

  while (p < end) {
    if (*p != '\\') {
      *d++ = *p++;
    } else {
      if (++p > last_byte) {  // skip past the '\\'
        if (error) *error = "String cannot end with \\";
        return false;
      }
      switch (*p) {
        case 'a':  *d++ = '\a';  break;
        case 'b':  *d++ = '\b';  break;
        case 'f':  *d++ = '\f';  break;
        case 'n':  *d++ = '\n';  break;
        case 'r':  *d++ = '\r';  break;
        case 't':  *d++ = '\t';  break;
        case 'v':  *d++ = '\v';  break;
        case '\\': *d++ = '\\';  break;
        case '?':  *d++ = '\?';  break;    // \?  Who knew?
        case '\'': *d++ = '\'';  break;
        case '"':  *d++ = '\"';  break;
        case '0':
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7': {
          // octal digit: 1 to 3 digits
          const char* octal_start = p;
          unsigned int ch = *p - '0';
          if (p < last_byte && is_octal_digit(p[1])) ch = ch * 8 + *++p - '0';
          if (p < last_byte && is_octal_digit(p[1]))
            ch = ch * 8 + *++p - '0';      // now points at last digit
          if (ch > 0xff) {
            if (error) {
              *error = "Value of \\" +
                       std::string(octal_start, p + 1 - octal_start) +
                       " exceeds 0xff";
            }
            return false;
          }
          if ((ch == 0) && leave_nulls_escaped) {
            // Copy the escape sequence for the null character
            const ptrdiff_t octal_size = p + 1 - octal_start;
            *d++ = '\\';
            memcpy(d, octal_start, octal_size);
            d += octal_size;
            break;
          }
          *d++ = ch;
          break;
        }
        case 'x':
        case 'X': {
          if (p >= last_byte) {
            if (error) *error = "String cannot end with \\x";
            return false;
          } else if (!absl::ascii_isxdigit(p[1])) {
            if (error) *error = "\\x cannot be followed by a non-hex digit";
            return false;
          }
          unsigned int ch = 0;
          const char* hex_start = p;
          while (p < last_byte && absl::ascii_isxdigit(p[1]))
            // Arbitrarily many hex digits
            ch = (ch << 4) + hex_digit_to_int(*++p);
          if (ch > 0xFF) {
            if (error) {
              *error = "Value of \\" + std::string(hex_start, p + 1 - hex_start) +
                       " exceeds 0xff";
            }
            return false;
          }
          if ((ch == 0) && leave_nulls_escaped) {
            // Copy the escape sequence for the null character
            const ptrdiff_t hex_size = p + 1 - hex_start;
            *d++ = '\\';
            memcpy(d, hex_start, hex_size);
            d += hex_size;
            break;
          }
          *d++ = ch;
          break;
        }
        case 'u': {
          // \uhhhh => convert 4 hex digits to UTF-8
          char32_t rune = 0;
          const char* hex_start = p;
          if (p + 4 >= end) {
            if (error) {
              *error = "\\u must be followed by 4 hex digits: \\" +
                       std::string(hex_start, p + 1 - hex_start);
            }
            return false;
          }
          for (int i = 0; i < 4; ++i) {
            // Look one char ahead.
            if (absl::ascii_isxdigit(p[1])) {
              rune = (rune << 4) + hex_digit_to_int(*++p);  // Advance p.
            } else {
              if (error) {
                *error = "\\u must be followed by 4 hex digits: \\" +
                         std::string(hex_start, p + 1 - hex_start);
              }
              return false;
            }
          }
          if ((rune == 0) && leave_nulls_escaped) {
            // Copy the escape sequence for the null character
            *d++ = '\\';
            memcpy(d, hex_start, 5);  // u0000
            d += 5;
            break;
          }
          if (IsSurrogate(rune, absl::string_view(hex_start, 5), error)) {
            return false;
          }
          d += strings_internal::EncodeUTF8Char(d, rune);
          break;
        }
        case 'U': {
          // \Uhhhhhhhh => convert 8 hex digits to UTF-8
          char32_t rune = 0;
          const char* hex_start = p;
          if (p + 8 >= end) {
            if (error) {
              *error = "\\U must be followed by 8 hex digits: \\" +
                       std::string(hex_start, p + 1 - hex_start);
            }
            return false;
          }
          for (int i = 0; i < 8; ++i) {
            // Look one char ahead.
            if (absl::ascii_isxdigit(p[1])) {
              // Don't change rune until we're sure this
              // is within the Unicode limit, but do advance p.
              uint32_t newrune = (rune << 4) + hex_digit_to_int(*++p);
              if (newrune > 0x10FFFF) {
                if (error) {
                  *error = "Value of \\" +
                           std::string(hex_start, p + 1 - hex_start) +
                           " exceeds Unicode limit (0x10FFFF)";
                }
                return false;
              } else {
                rune = newrune;
              }
            } else {
              if (error) {
                *error = "\\U must be followed by 8 hex digits: \\" +
                         std::string(hex_start, p + 1 - hex_start);
              }
              return false;
            }
          }
          if ((rune == 0) && leave_nulls_escaped) {
            // Copy the escape sequence for the null character
            *d++ = '\\';
            memcpy(d, hex_start, 9);  // U00000000
            d += 9;
            break;
          }
          if (IsSurrogate(rune, absl::string_view(hex_start, 9), error)) {
            return false;
          }
          d += strings_internal::EncodeUTF8Char(d, rune);
          break;
        }
        default: {
          if (error) *error = std::string("Unknown escape sequence: \\") + *p;
          return false;
        }
      }
      p++;                                 // read past letter we escaped
    }
  }
  *dest_len = d - dest;
  return true;
}

// ----------------------------------------------------------------------
// CUnescapeInternal()
//
//    Same as above but uses a C++ string for output. 'source' and 'dest'
//    may be the same.
// ----------------------------------------------------------------------
bool CUnescapeInternal(absl::string_view source, bool leave_nulls_escaped,
                       std::string* dest, std::string* error) {
  strings_internal::STLStringResizeUninitialized(dest, source.size());

  ptrdiff_t dest_size;
  if (!CUnescapeInternal(source,
                         leave_nulls_escaped,
                         const_cast<char*>(dest->data()),
                         &dest_size,
                         error)) {
    return false;
  }
  dest->erase(dest_size);
  return true;
}

// ----------------------------------------------------------------------
// CEscape()
// CHexEscape()
// Utf8SafeCEscape()
// Utf8SafeCHexEscape()
//    Escapes 'src' using C-style escape sequences.  This is useful for
//    preparing query flags.  The 'Hex' version uses hexadecimal rather than
//    octal sequences.  The 'Utf8Safe' version does not touch UTF-8 bytes.
//
//    Escaped chars: \n, \r, \t, ", ', \, and !absl::ascii_isprint().
// ----------------------------------------------------------------------
std::string CEscapeInternal(absl::string_view src, bool use_hex, bool utf8_safe) {
  std::string dest;
  bool last_hex_escape = false;  // true if last output char was \xNN.

  for (unsigned char c : src) {
    bool is_hex_escape = false;
    switch (c) {
      case '\n': dest.append("\\" "n"); break;
      case '\r': dest.append("\\" "r"); break;
      case '\t': dest.append("\\" "t"); break;
      case '\"': dest.append("\\" "\""); break;
      case '\'': dest.append("\\" "'"); break;
      case '\\': dest.append("\\" "\\"); break;
      default:
        // Note that if we emit \xNN and the src character after that is a hex
        // digit then that digit must be escaped too to prevent it being
        // interpreted as part of the character code by C.
        if ((!utf8_safe || c < 0x80) &&
            (!absl::ascii_isprint(c) ||
             (last_hex_escape && absl::ascii_isxdigit(c)))) {
          if (use_hex) {
            dest.append("\\" "x");
            dest.push_back(kHexChar[c / 16]);
            dest.push_back(kHexChar[c % 16]);
            is_hex_escape = true;
          } else {
            dest.append("\\");
            dest.push_back(kHexChar[c / 64]);
            dest.push_back(kHexChar[(c % 64) / 8]);
            dest.push_back(kHexChar[c % 8]);
          }
        } else {
          dest.push_back(c);
          break;
        }
    }
    last_hex_escape = is_hex_escape;
  }

  return dest;
}

/* clang-format off */
constexpr char c_escaped_len[256] = {
    4, 4, 4, 4, 4, 4, 4, 4, 4, 2, 2, 4, 4, 2, 4, 4,  // \t, \n, \r
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1,  // ", '
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // '0'..'9'
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 'A'..'O'
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1,  // 'P'..'Z', '\'
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 'a'..'o'
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4,  // 'p'..'z', DEL
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
};
/* clang-format on */

// Calculates the length of the C-style escaped version of 'src'.
// Assumes that non-printable characters are escaped using octal sequences, and
// that UTF-8 bytes are not handled specially.
inline size_t CEscapedLength(absl::string_view src) {
  size_t escaped_len = 0;
  for (unsigned char c : src) escaped_len += c_escaped_len[c];
  return escaped_len;
}

void CEscapeAndAppendInternal(absl::string_view src, std::string* dest) {
  size_t escaped_len = CEscapedLength(src);
  if (escaped_len == src.size()) {
    dest->append(src.data(), src.size());
    return;
  }

  size_t cur_dest_len = dest->size();
  strings_internal::STLStringResizeUninitialized(dest,
                                                 cur_dest_len + escaped_len);
  char* append_ptr = &(*dest)[cur_dest_len];

  for (unsigned char c : src) {
    int char_len = c_escaped_len[c];
    if (char_len == 1) {
      *append_ptr++ = c;
    } else if (char_len == 2) {
      switch (c) {
        case '\n':
          *append_ptr++ = '\\';
          *append_ptr++ = 'n';
          break;
        case '\r':
          *append_ptr++ = '\\';
          *append_ptr++ = 'r';
          break;
        case '\t':
          *append_ptr++ = '\\';
          *append_ptr++ = 't';
          break;
        case '\"':
          *append_ptr++ = '\\';
          *append_ptr++ = '\"';
          break;
        case '\'':
          *append_ptr++ = '\\';
          *append_ptr++ = '\'';
          break;
        case '\\':
          *append_ptr++ = '\\';
          *append_ptr++ = '\\';
          break;
      }
    } else {
      *append_ptr++ = '\\';
      *append_ptr++ = '0' + c / 64;
      *append_ptr++ = '0' + (c % 64) / 8;
      *append_ptr++ = '0' + c % 8;
    }
  }
}

bool Base64UnescapeInternal(const char* src_param, size_t szsrc, char* dest,
                            size_t szdest, const signed char* unbase64,
                            size_t* len) {
  static const char kPad64Equals = '=';
  static const char kPad64Dot = '.';

  size_t destidx = 0;
  int decode = 0;
  int state = 0;
  unsigned int ch = 0;
  unsigned int temp = 0;

  // If "char" is signed by default, using *src as an array index results in
  // accessing negative array elements. Treat the input as a pointer to
  // unsigned char to avoid this.
  const unsigned char* src = reinterpret_cast<const unsigned char*>(src_param);

  // The GET_INPUT macro gets the next input character, skipping
  // over any whitespace, and stopping when we reach the end of the
  // std::string or when we read any non-data character.  The arguments are
  // an arbitrary identifier (used as a label for goto) and the number
  // of data bytes that must remain in the input to avoid aborting the
  // loop.
#define GET_INPUT(label, remain)                                \
  label:                                                        \
  --szsrc;                                                      \
  ch = *src++;                                                  \
  decode = unbase64[ch];                                        \
  if (decode < 0) {                                             \
    if (absl::ascii_isspace(ch) && szsrc >= remain) goto label; \
    state = 4 - remain;                                         \
    break;                                                      \
  }

  // if dest is null, we're just checking to see if it's legal input
  // rather than producing output.  (I suspect this could just be done
  // with a regexp...).  We duplicate the loop so this test can be
  // outside it instead of in every iteration.

  if (dest) {
    // This loop consumes 4 input bytes and produces 3 output bytes
    // per iteration.  We can't know at the start that there is enough
    // data left in the std::string for a full iteration, so the loop may
    // break out in the middle; if so 'state' will be set to the
    // number of input bytes read.

    while (szsrc >= 4) {
      // We'll start by optimistically assuming that the next four
      // bytes of the std::string (src[0..3]) are four good data bytes
      // (that is, no nulls, whitespace, padding chars, or illegal
      // chars).  We need to test src[0..2] for nulls individually
      // before constructing temp to preserve the property that we
      // never read past a null in the std::string (no matter how long
      // szsrc claims the std::string is).

      if (!src[0] || !src[1] || !src[2] ||
          ((temp = ((unsigned(unbase64[src[0]]) << 18) |
                    (unsigned(unbase64[src[1]]) << 12) |
                    (unsigned(unbase64[src[2]]) << 6) |
                    (unsigned(unbase64[src[3]])))) &
           0x80000000)) {
        // Iff any of those four characters was bad (null, illegal,
        // whitespace, padding), then temp's high bit will be set
        // (because unbase64[] is -1 for all bad characters).
        //
        // We'll back up and resort to the slower decoder, which knows
        // how to handle those cases.

        GET_INPUT(first, 4);
        temp = decode;
        GET_INPUT(second, 3);
        temp = (temp << 6) | decode;
        GET_INPUT(third, 2);
        temp = (temp << 6) | decode;
        GET_INPUT(fourth, 1);
        temp = (temp << 6) | decode;
      } else {
        // We really did have four good data bytes, so advance four
        // characters in the std::string.

        szsrc -= 4;
        src += 4;
      }

      // temp has 24 bits of input, so write that out as three bytes.

      if (destidx + 3 > szdest) return false;
      dest[destidx + 2] = temp;
      temp >>= 8;
      dest[destidx + 1] = temp;
      temp >>= 8;
      dest[destidx] = temp;
      destidx += 3;
    }
  } else {
    while (szsrc >= 4) {
      if (!src[0] || !src[1] || !src[2] ||
          ((temp = ((unsigned(unbase64[src[0]]) << 18) |
                    (unsigned(unbase64[src[1]]) << 12) |
                    (unsigned(unbase64[src[2]]) << 6) |
                    (unsigned(unbase64[src[3]])))) &
           0x80000000)) {
        GET_INPUT(first_no_dest, 4);
        GET_INPUT(second_no_dest, 3);
        GET_INPUT(third_no_dest, 2);
        GET_INPUT(fourth_no_dest, 1);
      } else {
        szsrc -= 4;
        src += 4;
      }
      destidx += 3;
    }
  }

#undef GET_INPUT

  // if the loop terminated because we read a bad character, return
  // now.
  if (decode < 0 && ch != kPad64Equals && ch != kPad64Dot &&
      !absl::ascii_isspace(ch))
    return false;

  if (ch == kPad64Equals || ch == kPad64Dot) {
    // if we stopped by hitting an '=' or '.', un-read that character -- we'll
    // look at it again when we count to check for the proper number of
    // equals signs at the end.
    ++szsrc;
    --src;
  } else {
    // This loop consumes 1 input byte per iteration.  It's used to
    // clean up the 0-3 input bytes remaining when the first, faster
    // loop finishes.  'temp' contains the data from 'state' input
    // characters read by the first loop.
    while (szsrc > 0) {
      --szsrc;
      ch = *src++;
      decode = unbase64[ch];
      if (decode < 0) {
        if (absl::ascii_isspace(ch)) {
          continue;
        } else if (ch == kPad64Equals || ch == kPad64Dot) {
          // back up one character; we'll read it again when we check
          // for the correct number of pad characters at the end.
          ++szsrc;
          --src;
          break;
        } else {
          return false;
        }
      }

      // Each input character gives us six bits of output.
      temp = (temp << 6) | decode;
      ++state;
      if (state == 4) {
        // If we've accumulated 24 bits of output, write that out as
        // three bytes.
        if (dest) {
          if (destidx + 3 > szdest) return false;
          dest[destidx + 2] = temp;
          temp >>= 8;
          dest[destidx + 1] = temp;
          temp >>= 8;
          dest[destidx] = temp;
        }
        destidx += 3;
        state = 0;
        temp = 0;
      }
    }
  }

  // Process the leftover data contained in 'temp' at the end of the input.
  int expected_equals = 0;
  switch (state) {
    case 0:
      // Nothing left over; output is a multiple of 3 bytes.
      break;

    case 1:
      // Bad input; we have 6 bits left over.
      return false;

    case 2:
      // Produce one more output byte from the 12 input bits we have left.
      if (dest) {
        if (destidx + 1 > szdest) return false;
        temp >>= 4;
        dest[destidx] = temp;
      }
      ++destidx;
      expected_equals = 2;
      break;

    case 3:
      // Produce two more output bytes from the 18 input bits we have left.
      if (dest) {
        if (destidx + 2 > szdest) return false;
        temp >>= 2;
        dest[destidx + 1] = temp;
        temp >>= 8;
        dest[destidx] = temp;
      }
      destidx += 2;
      expected_equals = 1;
      break;

    default:
      // state should have no other values at this point.
      ABSL_RAW_LOG(FATAL, "This can't happen; base64 decoder state = %d",
                   state);
  }

  // The remainder of the std::string should be all whitespace, mixed with
  // exactly 0 equals signs, or exactly 'expected_equals' equals
  // signs.  (Always accepting 0 equals signs is an Abseil extension
  // not covered in the RFC, as is accepting dot as the pad character.)

  int equals = 0;
  while (szsrc > 0) {
    if (*src == kPad64Equals || *src == kPad64Dot)
      ++equals;
    else if (!absl::ascii_isspace(*src))
      return false;
    --szsrc;
    ++src;
  }

  const bool ok = (equals == 0 || equals == expected_equals);
  if (ok) *len = destidx;
  return ok;
}

// The arrays below were generated by the following code
// #include <sys/time.h>
// #include <stdlib.h>
// #include <string.h>
// main()
// {
//   static const char Base64[] =
//     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
//   char* pos;
//   int idx, i, j;
//   printf("    ");
//   for (i = 0; i < 255; i += 8) {
//     for (j = i; j < i + 8; j++) {
//       pos = strchr(Base64, j);
//       if ((pos == nullptr) || (j == 0))
//         idx = -1;
//       else
//         idx = pos - Base64;
//       if (idx == -1)
//         printf(" %2d,     ", idx);
//       else
//         printf(" %2d/*%c*/,", idx, j);
//     }
//     printf("\n    ");
//   }
// }
//
// where the value of "Base64[]" was replaced by one of the base-64 conversion
// tables from the functions below.
/* clang-format off */
constexpr signed char kUnBase64[] = {
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      62/*+*/, -1,      -1,      -1,      63/*/ */,
    52/*0*/, 53/*1*/, 54/*2*/, 55/*3*/, 56/*4*/, 57/*5*/, 58/*6*/, 59/*7*/,
    60/*8*/, 61/*9*/, -1,      -1,      -1,      -1,      -1,      -1,
    -1,       0/*A*/,  1/*B*/,  2/*C*/,  3/*D*/,  4/*E*/,  5/*F*/,  6/*G*/,
    07/*H*/,  8/*I*/,  9/*J*/, 10/*K*/, 11/*L*/, 12/*M*/, 13/*N*/, 14/*O*/,
    15/*P*/, 16/*Q*/, 17/*R*/, 18/*S*/, 19/*T*/, 20/*U*/, 21/*V*/, 22/*W*/,
    23/*X*/, 24/*Y*/, 25/*Z*/, -1,      -1,      -1,      -1,      -1,
    -1,      26/*a*/, 27/*b*/, 28/*c*/, 29/*d*/, 30/*e*/, 31/*f*/, 32/*g*/,
    33/*h*/, 34/*i*/, 35/*j*/, 36/*k*/, 37/*l*/, 38/*m*/, 39/*n*/, 40/*o*/,
    41/*p*/, 42/*q*/, 43/*r*/, 44/*s*/, 45/*t*/, 46/*u*/, 47/*v*/, 48/*w*/,
    49/*x*/, 50/*y*/, 51/*z*/, -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1
};

constexpr signed char kUnWebSafeBase64[] = {
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      62/*-*/, -1,      -1,
    52/*0*/, 53/*1*/, 54/*2*/, 55/*3*/, 56/*4*/, 57/*5*/, 58/*6*/, 59/*7*/,
    60/*8*/, 61/*9*/, -1,      -1,      -1,      -1,      -1,      -1,
    -1,       0/*A*/,  1/*B*/,  2/*C*/,  3/*D*/,  4/*E*/,  5/*F*/,  6/*G*/,
    07/*H*/,  8/*I*/,  9/*J*/, 10/*K*/, 11/*L*/, 12/*M*/, 13/*N*/, 14/*O*/,
    15/*P*/, 16/*Q*/, 17/*R*/, 18/*S*/, 19/*T*/, 20/*U*/, 21/*V*/, 22/*W*/,
    23/*X*/, 24/*Y*/, 25/*Z*/, -1,      -1,      -1,      -1,      63/*_*/,
    -1,      26/*a*/, 27/*b*/, 28/*c*/, 29/*d*/, 30/*e*/, 31/*f*/, 32/*g*/,
    33/*h*/, 34/*i*/, 35/*j*/, 36/*k*/, 37/*l*/, 38/*m*/, 39/*n*/, 40/*o*/,
    41/*p*/, 42/*q*/, 43/*r*/, 44/*s*/, 45/*t*/, 46/*u*/, 47/*v*/, 48/*w*/,
    49/*x*/, 50/*y*/, 51/*z*/, -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
    -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1
};
/* clang-format on */

size_t CalculateBase64EscapedLenInternal(size_t input_len, bool do_padding) {
  // Base64 encodes three bytes of input at a time. If the input is not
  // divisible by three, we pad as appropriate.
  //
  // (from http://tools.ietf.org/html/rfc3548)
  // Special processing is performed if fewer than 24 bits are available
  // at the end of the data being encoded.  A full encoding quantum is
  // always completed at the end of a quantity.  When fewer than 24 input
  // bits are available in an input group, zero bits are added (on the
  // right) to form an integral number of 6-bit groups.  Padding at the
  // end of the data is performed using the '=' character.  Since all base
  // 64 input is an integral number of octets, only the following cases
  // can arise:

  // Base64 encodes each three bytes of input into four bytes of output.
  size_t len = (input_len / 3) * 4;

  if (input_len % 3 == 0) {
    // (from http://tools.ietf.org/html/rfc3548)
    // (1) the final quantum of encoding input is an integral multiple of 24
    // bits; here, the final unit of encoded output will be an integral
    // multiple of 4 characters with no "=" padding,
  } else if (input_len % 3 == 1) {
    // (from http://tools.ietf.org/html/rfc3548)
    // (2) the final quantum of encoding input is exactly 8 bits; here, the
    // final unit of encoded output will be two characters followed by two
    // "=" padding characters, or
    len += 2;
    if (do_padding) {
      len += 2;
    }
  } else {  // (input_len % 3 == 2)
    // (from http://tools.ietf.org/html/rfc3548)
    // (3) the final quantum of encoding input is exactly 16 bits; here, the
    // final unit of encoded output will be three characters followed by one
    // "=" padding character.
    len += 3;
    if (do_padding) {
      len += 1;
    }
  }

  assert(len >= input_len);  // make sure we didn't overflow
  return len;
}

size_t Base64EscapeInternal(const unsigned char* src, size_t szsrc, char* dest,
                            size_t szdest, const char* base64,
                            bool do_padding) {
  static const char kPad64 = '=';

  if (szsrc * 4 > szdest * 3) return 0;

  char* cur_dest = dest;
  const unsigned char* cur_src = src;

  char* const limit_dest = dest + szdest;
  const unsigned char* const limit_src = src + szsrc;

  // Three bytes of data encodes to four characters of cyphertext.
  // So we can pump through three-byte chunks atomically.
  if (szsrc >= 3) {  // "limit_src - 3" is UB if szsrc < 3
    while (cur_src < limit_src - 3) {  // as long as we have >= 32 bits
      uint32_t in = absl::big_endian::Load32(cur_src) >> 8;

      cur_dest[0] = base64[in >> 18];
      in &= 0x3FFFF;
      cur_dest[1] = base64[in >> 12];
      in &= 0xFFF;
      cur_dest[2] = base64[in >> 6];
      in &= 0x3F;
      cur_dest[3] = base64[in];

      cur_dest += 4;
      cur_src += 3;
    }
  }
  // To save time, we didn't update szdest or szsrc in the loop.  So do it now.
  szdest = limit_dest - cur_dest;
  szsrc = limit_src - cur_src;

  /* now deal with the tail (<=3 bytes) */
  switch (szsrc) {
    case 0:
      // Nothing left; nothing more to do.
      break;
    case 1: {
      // One byte left: this encodes to two characters, and (optionally)
      // two pad characters to round out the four-character cypherblock.
      if (szdest < 2) return 0;
      uint32_t in = cur_src[0];
      cur_dest[0] = base64[in >> 2];
      in &= 0x3;
      cur_dest[1] = base64[in << 4];
      cur_dest += 2;
      szdest -= 2;
      if (do_padding) {
        if (szdest < 2) return 0;
        cur_dest[0] = kPad64;
        cur_dest[1] = kPad64;
        cur_dest += 2;
        szdest -= 2;
      }
      break;
    }
    case 2: {
      // Two bytes left: this encodes to three characters, and (optionally)
      // one pad character to round out the four-character cypherblock.
      if (szdest < 3) return 0;
      uint32_t in = absl::big_endian::Load16(cur_src);
      cur_dest[0] = base64[in >> 10];
      in &= 0x3FF;
      cur_dest[1] = base64[in >> 4];
      in &= 0x00F;
      cur_dest[2] = base64[in << 2];
      cur_dest += 3;
      szdest -= 3;
      if (do_padding) {
        if (szdest < 1) return 0;
        cur_dest[0] = kPad64;
        cur_dest += 1;
        szdest -= 1;
      }
      break;
    }
    case 3: {
      // Three bytes left: same as in the big loop above.  We can't do this in
      // the loop because the loop above always reads 4 bytes, and the fourth
      // byte is past the end of the input.
      if (szdest < 4) return 0;
      uint32_t in = (cur_src[0] << 16) + absl::big_endian::Load16(cur_src + 1);
      cur_dest[0] = base64[in >> 18];
      in &= 0x3FFFF;
      cur_dest[1] = base64[in >> 12];
      in &= 0xFFF;
      cur_dest[2] = base64[in >> 6];
      in &= 0x3F;
      cur_dest[3] = base64[in];
      cur_dest += 4;
      szdest -= 4;
      break;
    }
    default:
      // Should not be reached: blocks of 4 bytes are handled
      // in the while loop before this switch statement.
      ABSL_RAW_LOG(FATAL, "Logic problem? szsrc = %zu", szsrc);
      break;
  }
  return (cur_dest - dest);
}

constexpr char kBase64Chars[] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

constexpr char kWebSafeBase64Chars[] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";

void Base64EscapeInternal(const unsigned char* src, size_t szsrc, std::string* dest,
                          bool do_padding, const char* base64_chars) {
  const size_t calc_escaped_size =
      CalculateBase64EscapedLenInternal(szsrc, do_padding);
  strings_internal::STLStringResizeUninitialized(dest, calc_escaped_size);

  const size_t escaped_len = Base64EscapeInternal(
      src, szsrc, &(*dest)[0], dest->size(), base64_chars, do_padding);
  assert(calc_escaped_size == escaped_len);
  dest->erase(escaped_len);
}

bool Base64UnescapeInternal(const char* src, size_t slen, std::string* dest,
                            const signed char* unbase64) {
  // Determine the size of the output std::string.  Base64 encodes every 3 bytes into
  // 4 characters.  any leftover chars are added directly for good measure.
  // This is documented in the base64 RFC: http://tools.ietf.org/html/rfc3548
  const size_t dest_len = 3 * (slen / 4) + (slen % 4);

  strings_internal::STLStringResizeUninitialized(dest, dest_len);

  // We are getting the destination buffer by getting the beginning of the
  // std::string and converting it into a char *.
  size_t len;
  const bool ok =
      Base64UnescapeInternal(src, slen, &(*dest)[0], dest_len, unbase64, &len);
  if (!ok) {
    dest->clear();
    return false;
  }

  // could be shorter if there was padding
  assert(len <= dest_len);
  dest->erase(len);

  return true;
}

/* clang-format off */
constexpr char kHexValue[256] = {
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0,  1,  2,  3,  4,  5,  6, 7, 8, 9, 0, 0, 0, 0, 0, 0,  // '0'..'9'
    0, 10, 11, 12, 13, 14, 15, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 'A'..'F'
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 10, 11, 12, 13, 14, 15, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 'a'..'f'
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
/* clang-format on */

// This is a templated function so that T can be either a char*
// or a string.  This works because we use the [] operator to access
// individual characters at a time.
template <typename T>
void HexStringToBytesInternal(const char* from, T to, ptrdiff_t num) {
  for (int i = 0; i < num; i++) {
    to[i] = (kHexValue[from[i * 2] & 0xFF] << 4) +
            (kHexValue[from[i * 2 + 1] & 0xFF]);
  }
}

// This is a templated function so that T can be either a char* or a string.
template <typename T>
void BytesToHexStringInternal(const unsigned char* src, T dest, ptrdiff_t num) {
  auto dest_ptr = &dest[0];
  for (auto src_ptr = src; src_ptr != (src + num); ++src_ptr, dest_ptr += 2) {
    const char* hex_p = &kHexTable[*src_ptr * 2];
    std::copy(hex_p, hex_p + 2, dest_ptr);
  }
}

}  // namespace

// ----------------------------------------------------------------------
// CUnescape()
//
// See CUnescapeInternal() for implementation details.
// ----------------------------------------------------------------------
bool CUnescape(absl::string_view source, std::string* dest, std::string* error) {
  return CUnescapeInternal(source, kUnescapeNulls, dest, error);
}

std::string CEscape(absl::string_view src) {
  std::string dest;
  CEscapeAndAppendInternal(src, &dest);
  return dest;
}

std::string CHexEscape(absl::string_view src) {
  return CEscapeInternal(src, true, false);
}

std::string Utf8SafeCEscape(absl::string_view src) {
  return CEscapeInternal(src, false, true);
}

std::string Utf8SafeCHexEscape(absl::string_view src) {
  return CEscapeInternal(src, true, true);
}

// ----------------------------------------------------------------------
// ptrdiff_t Base64Unescape() - base64 decoder
// ptrdiff_t Base64Escape() - base64 encoder
// ptrdiff_t WebSafeBase64Unescape() - Google's variation of base64 decoder
// ptrdiff_t WebSafeBase64Escape() - Google's variation of base64 encoder
//
// Check out
// http://tools.ietf.org/html/rfc2045 for formal description, but what we
// care about is that...
//   Take the encoded stuff in groups of 4 characters and turn each
//   character into a code 0 to 63 thus:
//           A-Z map to 0 to 25
//           a-z map to 26 to 51
//           0-9 map to 52 to 61
//           +(- for WebSafe) maps to 62
//           /(_ for WebSafe) maps to 63
//   There will be four numbers, all less than 64 which can be represented
//   by a 6 digit binary number (aaaaaa, bbbbbb, cccccc, dddddd respectively).
//   Arrange the 6 digit binary numbers into three bytes as such:
//   aaaaaabb bbbbcccc ccdddddd
//   Equals signs (one or two) are used at the end of the encoded block to
//   indicate that the text was not an integer multiple of three bytes long.
// ----------------------------------------------------------------------

bool Base64Unescape(absl::string_view src, std::string* dest) {
  return Base64UnescapeInternal(src.data(), src.size(), dest, kUnBase64);
}

bool WebSafeBase64Unescape(absl::string_view src, std::string* dest) {
  return Base64UnescapeInternal(src.data(), src.size(), dest, kUnWebSafeBase64);
}

void Base64Escape(absl::string_view src, std::string* dest) {
  Base64EscapeInternal(reinterpret_cast<const unsigned char*>(src.data()),
                       src.size(), dest, true, kBase64Chars);
}

void WebSafeBase64Escape(absl::string_view src, std::string* dest) {
  Base64EscapeInternal(reinterpret_cast<const unsigned char*>(src.data()),
                       src.size(), dest, false, kWebSafeBase64Chars);
}

std::string HexStringToBytes(absl::string_view from) {
  std::string result;
  const auto num = from.size() / 2;
  strings_internal::STLStringResizeUninitialized(&result, num);
  absl::HexStringToBytesInternal<std::string&>(from.data(), result, num);
  return result;
}

std::string BytesToHexString(absl::string_view from) {
  std::string result;
  strings_internal::STLStringResizeUninitialized(&result, 2 * from.size());
  absl::BytesToHexStringInternal<std::string&>(
      reinterpret_cast<const unsigned char*>(from.data()), result, from.size());
  return result;
}

}  // namespace absl