1 // Copyright 2017 The Abseil Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include "absl/strings/match.h"
16
17 #include <algorithm>
18 #include <cstdint>
19
20 #include "absl/base/config.h"
21 #include "absl/base/internal/endian.h"
22 #include "absl/base/optimization.h"
23 #include "absl/numeric/bits.h"
24 #include "absl/strings/ascii.h"
25 #include "absl/strings/internal/memutil.h"
26 #include "absl/strings/string_view.h"
27
28 namespace absl {
29 ABSL_NAMESPACE_BEGIN
30
EqualsIgnoreCase(absl::string_view piece1,absl::string_view piece2)31 bool EqualsIgnoreCase(absl::string_view piece1,
32 absl::string_view piece2) noexcept {
33 return (piece1.size() == piece2.size() &&
34 0 == absl::strings_internal::memcasecmp(piece1.data(), piece2.data(),
35 piece1.size()));
36 // memcasecmp uses absl::ascii_tolower().
37 }
38
StrContainsIgnoreCase(absl::string_view haystack,absl::string_view needle)39 bool StrContainsIgnoreCase(absl::string_view haystack,
40 absl::string_view needle) noexcept {
41 while (haystack.size() >= needle.size()) {
42 if (StartsWithIgnoreCase(haystack, needle)) return true;
43 haystack.remove_prefix(1);
44 }
45 return false;
46 }
47
StrContainsIgnoreCase(absl::string_view haystack,char needle)48 bool StrContainsIgnoreCase(absl::string_view haystack,
49 char needle) noexcept {
50 char upper_needle = absl::ascii_toupper(static_cast<unsigned char>(needle));
51 char lower_needle = absl::ascii_tolower(static_cast<unsigned char>(needle));
52 if (upper_needle == lower_needle) {
53 return StrContains(haystack, needle);
54 } else {
55 const char both_cstr[3] = {lower_needle, upper_needle, '\0'};
56 return haystack.find_first_of(both_cstr) != absl::string_view::npos;
57 }
58 }
59
StartsWithIgnoreCase(absl::string_view text,absl::string_view prefix)60 bool StartsWithIgnoreCase(absl::string_view text,
61 absl::string_view prefix) noexcept {
62 return (text.size() >= prefix.size()) &&
63 EqualsIgnoreCase(text.substr(0, prefix.size()), prefix);
64 }
65
EndsWithIgnoreCase(absl::string_view text,absl::string_view suffix)66 bool EndsWithIgnoreCase(absl::string_view text,
67 absl::string_view suffix) noexcept {
68 return (text.size() >= suffix.size()) &&
69 EqualsIgnoreCase(text.substr(text.size() - suffix.size()), suffix);
70 }
71
FindLongestCommonPrefix(absl::string_view a,absl::string_view b)72 absl::string_view FindLongestCommonPrefix(absl::string_view a,
73 absl::string_view b) {
74 const absl::string_view::size_type limit = std::min(a.size(), b.size());
75 const char* const pa = a.data();
76 const char* const pb = b.data();
77 absl::string_view::size_type count = (unsigned) 0;
78
79 if (ABSL_PREDICT_FALSE(limit < 8)) {
80 while (ABSL_PREDICT_TRUE(count + 2 <= limit)) {
81 uint16_t xor_bytes = absl::little_endian::Load16(pa + count) ^
82 absl::little_endian::Load16(pb + count);
83 if (ABSL_PREDICT_FALSE(xor_bytes != 0)) {
84 if (ABSL_PREDICT_TRUE((xor_bytes & 0xff) == 0)) ++count;
85 return absl::string_view(pa, count);
86 }
87 count += 2;
88 }
89 if (ABSL_PREDICT_TRUE(count != limit)) {
90 if (ABSL_PREDICT_TRUE(pa[count] == pb[count])) ++count;
91 }
92 return absl::string_view(pa, count);
93 }
94
95 do {
96 uint64_t xor_bytes = absl::little_endian::Load64(pa + count) ^
97 absl::little_endian::Load64(pb + count);
98 if (ABSL_PREDICT_FALSE(xor_bytes != 0)) {
99 count += static_cast<uint64_t>(absl::countr_zero(xor_bytes) >> 3);
100 return absl::string_view(pa, count);
101 }
102 count += 8;
103 } while (ABSL_PREDICT_TRUE(count + 8 < limit));
104
105 count = limit - 8;
106 uint64_t xor_bytes = absl::little_endian::Load64(pa + count) ^
107 absl::little_endian::Load64(pb + count);
108 if (ABSL_PREDICT_TRUE(xor_bytes != 0)) {
109 count += static_cast<uint64_t>(absl::countr_zero(xor_bytes) >> 3);
110 return absl::string_view(pa, count);
111 }
112 return absl::string_view(pa, limit);
113 }
114
FindLongestCommonSuffix(absl::string_view a,absl::string_view b)115 absl::string_view FindLongestCommonSuffix(absl::string_view a,
116 absl::string_view b) {
117 const absl::string_view::size_type limit = std::min(a.size(), b.size());
118 if (limit == 0) return absl::string_view();
119
120 const char* pa = a.data() + a.size() - 1;
121 const char* pb = b.data() + b.size() - 1;
122 absl::string_view::size_type count = (unsigned) 0;
123 while (count < limit && *pa == *pb) {
124 --pa;
125 --pb;
126 ++count;
127 }
128
129 return absl::string_view(++pa, count);
130 }
131
132 ABSL_NAMESPACE_END
133 } // namespace absl
134