1// Copyright 2015 Google Inc.
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// http://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////////////////////////////////////////////////////////////////////////////////
16//
17// LRU cache decorator for binary_parse::PagedByteArray subclasses.
18
19#ifndef PIEX_BINARY_PARSE_CACHED_PAGED_BYTE_ARRAY_H_
20#define PIEX_BINARY_PARSE_CACHED_PAGED_BYTE_ARRAY_H_
21
22#include <mutex>
23#include <vector>
24
25#if !defined(WIN32_LEAN_AND_MEAN)
26#define WIN32_LEAN_AND_MEAN
27#endif
28#include "src/binary_parse/range_checked_byte_ptr.h"
29
30namespace piex {
31namespace binary_parse {
32
33class CachedPagedByteArray : public PagedByteArray {
34 public:
35 // Decorates 'paged_byte_array' with a LRU cache layer of the size
36 // 'cache_size'.
37 explicit CachedPagedByteArray(const PagedByteArray* paged_byte_array,
38 size_t cache_size);
39
40 virtual size_t length() const { return paged_byte_array_->length(); }
41
42 virtual size_t pageSize() const { return paged_byte_array_->pageSize(); }
43
44 virtual void getPage(size_t page_index, const unsigned char** begin,
45 const unsigned char** end,
46 PagedByteArray::PagePtr* page) const;
47
48 private:
49 struct CachedPage {
50 size_t index;
51 PagedByteArray::PagePtr page;
52 const unsigned char* begin;
53 const unsigned char* end;
54 };
55
56 // Disallow copy construction and assignment.
57 CachedPagedByteArray(const CachedPagedByteArray&);
58 void operator=(const CachedPagedByteArray&);
59
60 // Gets the index of the page if it is in the cache and returns true, else
61 // returns false.
62 bool getFromCache(size_t page_index, size_t* cache_index) const;
63
64 mutable std::mutex mutex_;
65 const PagedByteArray* paged_byte_array_;
66 const size_t cache_size_;
67 mutable std::vector<CachedPage> cached_pages_;
68};
69
70} // namespace binary_parse
71} // namespace piex
72
73#endif // PIEX_BINARY_PARSE_CACHED_PAGED_BYTE_ARRAY_H_
74