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/*
* Copyright (c) 2020-2021 Vasile Vilvoiu <vasi@vilvoiu.ro>
*
* specgram is free software; you can redistribute it and/or modify
* it under the terms of the MIT license. See LICENSE for details.
*/
#include "input-reader.hpp"
#include <csignal>
#include <cassert>
InputReader::InputReader(std::istream * stream, std::size_t block_size_bytes)
: stream_(stream), block_size_bytes_(block_size_bytes)
{
if (stream == nullptr) {
throw std::runtime_error("valid stream is required");
}
if (block_size_bytes == 0) {
throw std::runtime_error("block size in bytes must be positive");
}
}
SyncInputReader::SyncInputReader(std::istream * stream, std::size_t block_size_bytes)
: InputReader(stream, block_size_bytes)
{
}
bool
SyncInputReader::ReachedEOF() const
{
assert(this->stream_ != nullptr);
return this->stream_->eof();
}
std::optional<std::vector<char>>
SyncInputReader::GetBlock()
{
auto buffer = this->GetBuffer();
if (buffer.size() == this->block_size_bytes_) {
return buffer;
} else {
/* we assume the only time we're reading less than a block is at EOF */
assert(this->stream_->eof());
return {};
}
}
std::vector<char>
SyncInputReader::GetBuffer()
{
std::vector<char> local_buffer;
local_buffer.resize(this->block_size_bytes_);
assert(this->stream_ != nullptr);
this->stream_->read(local_buffer.data(), this->block_size_bytes_);
return std::vector<char>(local_buffer.data(), local_buffer.data() + this->stream_->gcount());
}
AsyncInputReader::AsyncInputReader(std::istream * stream, std::size_t block_size_bytes)
: InputReader(stream, block_size_bytes)
{
this->buffer_ = new char[block_size_bytes];
assert(this->buffer_ != nullptr);
this->bytes_in_buffer_ = 0;
/* start reader thread */
this->running_ = true;
this->reader_thread_ = std::thread(&AsyncInputReader::Read, this);
}
AsyncInputReader::~AsyncInputReader()
{
/* end reader thread */
this->mutex_.lock();
this->running_ = false;
this->mutex_.unlock();
/* send SIGINT so we interrupt any blocking reads */
pthread_kill(this->reader_thread_.native_handle(), SIGINT);
this->reader_thread_.join();
/* dealloc buffer */
if (this->buffer_ != nullptr) {
delete[] this->buffer_;
this->buffer_ = nullptr;
}
}
void
AsyncInputReader::Read()
{
char *local_buffer = new char[this->block_size_bytes_];
assert(local_buffer != nullptr);
while (true) {
/* find out how much we need to populate in the buffer */
this->mutex_.lock();
long long int to_read = this->block_size_bytes_ - this->bytes_in_buffer_;
if (!this->running_) {
this->mutex_.unlock();
break;
}
this->mutex_.unlock();
assert(to_read >= 0);
/* yield execution if nothing to read */
if (to_read == 0) {
std::this_thread::yield();
continue;
}
/* blocking read */
assert(this->stream_ != nullptr);
this->stream_->read(local_buffer, to_read);
if (this->stream_->fail()) {
break;
} else {
assert(this->stream_->gcount() == to_read);
}
/* write to buffer */
this->mutex_.lock();
if (!this->running_) {
this->mutex_.unlock();
break;
}
assert(to_read + this->bytes_in_buffer_ <= this->block_size_bytes_);
auto k = to_read;
assert(this->buffer_ != nullptr);
for (volatile char *a = local_buffer, *b = this->buffer_ + this->bytes_in_buffer_; k > 0; *b++ = *a++, k--) /* nop */;
this->bytes_in_buffer_ = this->bytes_in_buffer_ + to_read;
this->mutex_.unlock();
}
}
bool
AsyncInputReader::ReachedEOF() const
{
/* we will never reach end of file in async mode */
/* only way out is SIGINT from user */
return false;
}
std::optional<std::vector<char>>
AsyncInputReader::GetBlock()
{
const std::lock_guard<std::mutex> lock(this->mutex_);
if (this->bytes_in_buffer_ < this->block_size_bytes_) {
return {};
} else {
auto bcount = this->bytes_in_buffer_;
this->bytes_in_buffer_ = 0;
assert(this->buffer_);
return std::vector<char>(this->buffer_, this->buffer_ + bcount);
}
}
std::vector<char>
AsyncInputReader::GetBuffer()
{
const std::lock_guard<std::mutex> lock(this->mutex_);
assert(this->buffer_);
std::vector<char> wrapper(this->buffer_, this->buffer_ + this->bytes_in_buffer_);
this->bytes_in_buffer_ = 0;
return wrapper;
}
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