mapped-file.h revision 5b6dc79427b8f7eeb6a7ff68034ab8548ce670ea 
1
2// Licensed under the Apache License, Version 2.0 (the "License");
3// you may not use this file except in compliance with the License.
4// You may obtain a copy of the License at
5//
6//     http://www.apache.org/licenses/LICENSE-2.0
7//
8// Unless required by applicable law or agreed to in writing, software
9// distributed under the License is distributed on an "AS IS" BASIS,
10// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
11// See the License for the specific language governing permissions and
12// limitations under the License.
13//
14// Copyright 2005-2010 Google, Inc.
15// Author: sorenj@google.com (Jeffrey Sorensen)
16
17#ifndef FST_LIB_MAPPED_FILE_H_
18#define FST_LIB_MAPPED_FILE_H_
19
20#include <unistd.h>
21#include <sys/mman.h>
22
23#include <fst/fst.h>
24#include <iostream>
25#include <fstream>
26#include <sstream>
27
28DECLARE_int32(fst_arch_alignment);  // defined in mapped-file.h
29
30namespace fst {
31
32// A memory region is a simple abstraction for allocated memory or data from
33// mmap'ed files.  If mmap equals NULL, then data represents an owned region of
34// size bytes.  Otherwise, mmap and size refer to the mapping and data is a
35// casted pointer to a region contained within [mmap, mmap + size).
36// If size is 0, then mmap refers and data refer to a block of memory managed
37// externally by some other allocator.
38struct MemoryRegion {
39  void *data;
40  void *mmap;
41  size_t size;
42};
43
44class MappedFile {
45 public:
46  virtual ~MappedFile();
47
48  void* mutable_data() const {
49    return reinterpret_cast<void*>(region_.data);
50  }
51
52  const void* data() const {
53    return reinterpret_cast<void*>(region_.data);
54  }
55
56  // Returns a MappedFile object that contains the contents of the input
57  // stream s starting from the current file position with size bytes.
58  // The file name must also be provided in the FstReadOptions as opts.source
59  // or else mapping will fail.  If mapping is not possible, then a MappedFile
60  // object with a new[]'ed  block of memory will be created.
61  static MappedFile* Map(istream* s, const FstReadOptions& opts, size_t size);
62
63  // Creates a MappedFile object with a new[]'ed block of memory of size.
64  // RECOMMENDED FOR INTERNAL USE ONLY, may change in future releases.
65  static MappedFile* Allocate(size_t size);
66
67  // Creates a MappedFile object pointing to a borrowed reference to data.
68  // This block of memory is not owned by the MappedFile object and will not
69  // be freed.
70  // RECOMMENDED FOR INTERNAL USE ONLY, may change in future releases.
71  static MappedFile* Borrow(void *data);
72
73  static const int kArchAlignment;
74
75 private:
76  explicit MappedFile(const MemoryRegion &region);
77
78  MemoryRegion region_;
79  DISALLOW_COPY_AND_ASSIGN(MappedFile);
80};
81}  // namespace fst
82
83#endif  // FST_LIB_MAPPED_FILE_H_
84