blob: 396c0e2cd83548bbf09aa45bcc84cd10266751c1 (
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
|
// Copyright 2021 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
//
// https://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.
#ifndef ABSL_STRINGS_INTERNAL_CORD_REP_RING_READER_H_
#define ABSL_STRINGS_INTERNAL_CORD_REP_RING_READER_H_
#include <cassert>
#include <cstddef>
#include <cstdint>
#include "absl/strings/internal/cord_internal.h"
#include "absl/strings/internal/cord_rep_ring.h"
#include "absl/strings/string_view.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace cord_internal {
// CordRepRingReader provides basic navigation over CordRepRing data.
class CordRepRingReader {
public:
// Returns true if this instance is not empty.
explicit operator bool() const { return ring_ != nullptr; }
// Returns the ring buffer reference for this instance, or nullptr if empty.
CordRepRing* ring() const { return ring_; }
// Returns the current node index inside the ring buffer for this instance.
// The returned value is undefined if this instance is empty.
CordRepRing::index_type index() const { return index_; }
// Returns the length of the referenced ring buffer.
// Requires the current instance to be non empty.
size_t length() const {
assert(ring_);
return ring_->length;
}
// Returns the end offset of the last navigated-to chunk, which represents the
// total bytes 'consumed' relative to the start of the ring. The returned
// value is never zero. For example, initializing a reader with a ring buffer
// with a first chunk of 19 bytes will return consumed() = 19.
// Requires the current instance to be non empty.
size_t consumed() const {
assert(ring_);
return ring_->entry_end_offset(index_);
}
// Returns the number of bytes remaining beyond the last navigated-to chunk.
// Requires the current instance to be non empty.
size_t remaining() const {
assert(ring_);
return length() - consumed();
}
// Resets this instance to an empty value
void Reset() { ring_ = nullptr; }
// Resets this instance to the start of `ring`. `ring` must not be null.
// Returns a reference into the first chunk of the provided ring.
absl::string_view Reset(CordRepRing* ring) {
assert(ring);
ring_ = ring;
index_ = ring_->head();
return ring_->entry_data(index_);
}
// Navigates to the next chunk inside the reference ring buffer.
// Returns a reference into the navigated-to chunk.
// Requires remaining() to be non zero.
absl::string_view Next() {
assert(remaining());
index_ = ring_->advance(index_);
return ring_->entry_data(index_);
}
// Navigates to the chunk at offset `offset`.
// Returns a reference into the navigated-to chunk, adjusted for the relative
// position of `offset` into that chunk. For example, calling Seek(13) on a
// ring buffer containing 2 chunks of 10 and 20 bytes respectively will return
// a string view into the second chunk starting at offset 3 with a size of 17.
// Requires `offset` to be less than `length()`
absl::string_view Seek(size_t offset) {
assert(offset < length());
size_t current = ring_->entry_end_offset(index_);
CordRepRing::index_type hint = (offset >= current) ? index_ : ring_->head();
const CordRepRing::Position head = ring_->Find(hint, offset);
index_ = head.index;
auto data = ring_->entry_data(head.index);
data.remove_prefix(head.offset);
return data;
}
private:
CordRepRing* ring_ = nullptr;
CordRepRing::index_type index_;
};
} // namespace cord_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_STRINGS_INTERNAL_CORD_REP_RING_READER_H_
|
