mirror of
https://github.com/kidfromjupiter/nearby.git
synced 2026-09-15 07:06:11 -04:00
Janusz Sobczak
1a78b33a89
Read() can return fewer bytes than requested. ReadExactly() will call Read() repeatedly until we have read as many bytes as we need. PiperOrigin-RevId: 518719418
78 lines
2.2 KiB
C++
78 lines
2.2 KiB
C++
// Copyright 2020 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "internal/platform/input_stream.h"
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#include <algorithm>
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#include <cstddef>
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#include <cstdint>
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#include <utility>
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#include "internal/platform/byte_array.h"
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#include "internal/platform/exception.h"
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namespace nearby {
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namespace {
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constexpr size_t kSkipBufferSize = 64 * 1024;
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} // namespace
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ExceptionOr<size_t> InputStream::Skip(size_t offset) {
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size_t bytes_left = offset;
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while (bytes_left > 0) {
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size_t chunk_size = std::min(bytes_left, kSkipBufferSize);
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ExceptionOr<ByteArray> result = Read(chunk_size);
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if (!result.ok()) {
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return result.GetException();
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}
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size_t bytes_read = result.GetResult().size();
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if (bytes_read == 0) {
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return ExceptionOr<size_t>(offset - bytes_left);
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}
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bytes_left -= bytes_read;
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}
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return ExceptionOr<size_t>(offset);
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}
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ExceptionOr<ByteArray> InputStream::ReadExactly(std::size_t size) {
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ByteArray buffer;
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std::size_t current_pos = 0;
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while (current_pos < size) {
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ExceptionOr<ByteArray> read_bytes = Read(size - current_pos);
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if (!read_bytes.ok()) {
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return read_bytes;
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}
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const ByteArray& result = read_bytes.result();
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if (result.Empty()) {
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return ExceptionOr<ByteArray>(Exception::kIo);
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}
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if (current_pos == 0) {
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if (result.size() == size) {
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// We have read the requested `size` bytes in one chunk. We can return
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// it directly.
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return read_bytes;
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} else {
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// Reserve space for in the buffer.
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buffer.SetData(size);
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}
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}
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buffer.CopyAt(current_pos, result);
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current_pos += result.size();
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}
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return ExceptionOr<ByteArray>(std::move(buffer));
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}
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} // namespace nearby
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