1 /* Copyright 2016 The TensorFlow Authors. All Rights Reserved.
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 #include "tensorflow/core/lib/io/random_inputstream.h"
17 #include <memory>
18
19 namespace tensorflow {
20 namespace io {
21
RandomAccessInputStream(RandomAccessFile * file,bool owns_file)22 RandomAccessInputStream::RandomAccessInputStream(RandomAccessFile* file,
23 bool owns_file)
24 : file_(file), owns_file_(owns_file) {}
25
~RandomAccessInputStream()26 RandomAccessInputStream::~RandomAccessInputStream() {
27 if (owns_file_) {
28 delete file_;
29 }
30 }
31
ReadNBytes(int64_t bytes_to_read,tstring * result)32 Status RandomAccessInputStream::ReadNBytes(int64_t bytes_to_read,
33 tstring* result) {
34 if (bytes_to_read < 0) {
35 return errors::InvalidArgument("Cannot read negative number of bytes");
36 }
37 result->clear();
38 result->resize_uninitialized(bytes_to_read);
39 char* result_buffer = &(*result)[0];
40 StringPiece data;
41 Status s = file_->Read(pos_, bytes_to_read, &data, result_buffer);
42 if (data.data() != result_buffer) {
43 memmove(result_buffer, data.data(), data.size());
44 }
45 result->resize(data.size());
46 if (s.ok() || errors::IsOutOfRange(s)) {
47 pos_ += data.size();
48 }
49 return s;
50 }
51
52 #if defined(TF_CORD_SUPPORT)
ReadNBytes(int64_t bytes_to_read,absl::Cord * result)53 Status RandomAccessInputStream::ReadNBytes(int64_t bytes_to_read,
54 absl::Cord* result) {
55 if (bytes_to_read < 0) {
56 return errors::InvalidArgument("Cannot read negative number of bytes");
57 }
58 int64_t current_size = result->size();
59 Status s = file_->Read(pos_, bytes_to_read, result);
60 if (s.ok() || errors::IsOutOfRange(s)) {
61 pos_ += result->size() - current_size;
62 }
63 return s;
64 }
65 #endif
66
67 // To limit memory usage, the default implementation of SkipNBytes() only reads
68 // 8MB at a time.
69 static constexpr int64_t kMaxSkipSize = 8 * 1024 * 1024;
70
SkipNBytes(int64_t bytes_to_skip)71 Status RandomAccessInputStream::SkipNBytes(int64_t bytes_to_skip) {
72 if (bytes_to_skip < 0) {
73 return errors::InvalidArgument("Can't skip a negative number of bytes");
74 }
75 std::unique_ptr<char[]> scratch(new char[kMaxSkipSize]);
76 // Try to read 1 bytes first, if we could complete the read then EOF is
77 // not reached yet and we could return.
78 if (bytes_to_skip > 0) {
79 StringPiece data;
80 Status s = file_->Read(pos_ + bytes_to_skip - 1, 1, &data, scratch.get());
81 if ((s.ok() || errors::IsOutOfRange(s)) && data.size() == 1) {
82 pos_ += bytes_to_skip;
83 return OkStatus();
84 }
85 }
86 // Read kDefaultSkipSize at a time till bytes_to_skip.
87 while (bytes_to_skip > 0) {
88 int64_t bytes_to_read = std::min<int64_t>(kMaxSkipSize, bytes_to_skip);
89 StringPiece data;
90 Status s = file_->Read(pos_, bytes_to_read, &data, scratch.get());
91 if (s.ok() || errors::IsOutOfRange(s)) {
92 pos_ += data.size();
93 } else {
94 return s;
95 }
96 if (data.size() < static_cast<size_t>(bytes_to_read)) {
97 return errors::OutOfRange("reached end of file");
98 }
99 bytes_to_skip -= bytes_to_read;
100 }
101 return OkStatus();
102 }
103
Tell() const104 int64_t RandomAccessInputStream::Tell() const { return pos_; }
105
106 } // namespace io
107 } // namespace tensorflow
108