1 // Copyright 2019 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "src/objects/string-comparator.h"
6
7 #include "src/objects/string-inl.h"
8
9 namespace v8 {
10 namespace internal {
11
Init(String string)12 void StringComparator::State::Init(String string) {
13 ConsString cons_string = String::VisitFlat(this, string);
14 iter_.Reset(cons_string);
15 if (!cons_string.is_null()) {
16 int offset;
17 string = iter_.Next(&offset);
18 String::VisitFlat(this, string, offset);
19 }
20 }
21
Advance(int consumed)22 void StringComparator::State::Advance(int consumed) {
23 DCHECK(consumed <= length_);
24 // Still in buffer.
25 if (length_ != consumed) {
26 if (is_one_byte_) {
27 buffer8_ += consumed;
28 } else {
29 buffer16_ += consumed;
30 }
31 length_ -= consumed;
32 return;
33 }
34 // Advance state.
35 int offset;
36 String next = iter_.Next(&offset);
37 DCHECK_EQ(0, offset);
38 DCHECK(!next.is_null());
39 String::VisitFlat(this, next);
40 }
41
Equals(String string_1,String string_2)42 bool StringComparator::Equals(String string_1, String string_2) {
43 int length = string_1.length();
44 state_1_.Init(string_1);
45 state_2_.Init(string_2);
46 while (true) {
47 int to_check = std::min(state_1_.length_, state_2_.length_);
48 DCHECK(to_check > 0 && to_check <= length);
49 bool is_equal;
50 if (state_1_.is_one_byte_) {
51 if (state_2_.is_one_byte_) {
52 is_equal = Equals<uint8_t, uint8_t>(&state_1_, &state_2_, to_check);
53 } else {
54 is_equal = Equals<uint8_t, uint16_t>(&state_1_, &state_2_, to_check);
55 }
56 } else {
57 if (state_2_.is_one_byte_) {
58 is_equal = Equals<uint16_t, uint8_t>(&state_1_, &state_2_, to_check);
59 } else {
60 is_equal = Equals<uint16_t, uint16_t>(&state_1_, &state_2_, to_check);
61 }
62 }
63 // Looping done.
64 if (!is_equal) return false;
65 length -= to_check;
66 // Exit condition. Strings are equal.
67 if (length == 0) return true;
68 state_1_.Advance(to_check);
69 state_2_.Advance(to_check);
70 }
71 }
72
73 } // namespace internal
74 } // namespace v8
75