1 // Copyright 2020 The Pigweed Authors
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License"); you may not
4 // use this file except in compliance with the License. You may obtain a copy of
5 // the License at
6 //
7 // https://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, WITHOUT
11 // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
12 // License for the specific language governing permissions and limitations under
13 // the License.
14
15 #include "pw_stream/memory_stream.h"
16
17 #include <cstddef>
18 #include <cstring>
19
20 #include "pw_status/status_with_size.h"
21
22 namespace pw::stream {
23
DoWrite(ConstByteSpan data)24 Status MemoryWriter::DoWrite(ConstByteSpan data) {
25 if (ConservativeWriteLimit() == 0) {
26 return Status::OutOfRange();
27 }
28 if (ConservativeWriteLimit() < data.size_bytes()) {
29 return Status::ResourceExhausted();
30 }
31
32 size_t bytes_to_write = data.size_bytes();
33 if (bytes_to_write == 0) {
34 // Calling memmove with a null pointer is undefined behavior, even when zero
35 // bytes are moved. We must return early here to avoid performing such a
36 // call when data is an empty span.
37 return OkStatus();
38 }
39 std::memmove(dest_.data() + position_, data.data(), bytes_to_write);
40 position_ += bytes_to_write;
41
42 return OkStatus();
43 }
44
DoRead(ByteSpan dest)45 StatusWithSize MemoryReader::DoRead(ByteSpan dest) {
46 if (source_.size_bytes() == position_) {
47 return StatusWithSize::OutOfRange();
48 }
49
50 size_t bytes_to_read =
51 std::min(dest.size_bytes(), source_.size_bytes() - position_);
52 if (bytes_to_read == 0) {
53 // Calling memcpy with a null pointer is undefined behavior, even when zero
54 // bytes are copied. We must return early here to avoid performing such a
55 // call when the dest span is empty.
56 return StatusWithSize(0);
57 }
58
59 std::memcpy(dest.data(), source_.data() + position_, bytes_to_read);
60 position_ += bytes_to_read;
61
62 return StatusWithSize(bytes_to_read);
63 }
64
65 } // namespace pw::stream
66