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/* Copyright 2024 Ján Sučan <jan@jansucan.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "buffered_stream.h"
#include "exception.h"
#include <algorithm>
#include <cassert>
#include <cstring>
#include <filesystem>
#include <fstream>
namespace BufferedStream
{
Reader::Reader(std::istream &istream, size_t buffer_capacity,
size_t buffer_count)
: m_buffer_count(buffer_count), m_buffer_capacity(buffer_capacity),
m_istream(istream), m_buffers(buffer_count),
m_buffer_index(buffer_count - 1), m_buffer_offset(buffer_capacity),
m_buffer_size(buffer_capacity)
{
for (size_t i = 0; i < m_buffer_count; ++i) {
try {
m_buffers[i] = std::shared_ptr<char[]>(new char[m_buffer_capacity]);
} catch (const std::bad_alloc &e) {
throw Error("cannot allocate buffer for input stream data");
}
}
refill_next_buffer();
};
size_t
Reader::read(size_t data_size, char *dest_buf)
{
size_t retry_count{0};
size_t offset{0};
size_t to_read{data_size};
while ((to_read > 0) && (retry_count < 2)) {
const DataPart dp{readMultipart(to_read)};
if (dp.size == 0) {
++retry_count;
continue;
}
retry_count = 0;
memcpy(dest_buf + offset, dp.data.get(), dp.size);
offset += dp.size;
to_read -= dp.size;
}
assert(offset <= data_size);
return offset;
}
DataPart
Reader::readMultipart(size_t data_size)
{
const size_t size_left{m_buffer_size - m_buffer_offset};
if (size_left == 0) {
refill_next_buffer();
if (m_buffer_size == 0) {
return DataPart{.size = 0, .data = std::shared_ptr<char[]>()};
}
}
// There is at least one byte in the buffer
const DataPart dp{read_current_buffer(data_size)};
assert(dp.size > 0);
return dp;
}
DataPart
Reader::read_current_buffer(size_t data_size)
{
DataPart dp;
// Set data
if (m_buffer_offset == 0) {
dp.data = std::shared_ptr<char[]>{m_buffers[m_buffer_index]};
} else {
dp.data = std::shared_ptr<char[]>{
m_buffers[m_buffer_index],
static_cast<char *>(m_buffers[m_buffer_index].get()) +
m_buffer_offset};
}
const size_t size_left{m_buffer_size - m_buffer_offset};
dp.size = std::min(data_size, size_left);
m_buffer_offset += dp.size;
return dp;
};
void
Reader::refill_next_buffer()
{
if (m_buffer_size == 0) {
// Current buffer is the last one. Don't fill the next one.
return;
}
// Current buffer must be completely read before filling the next one
assert(m_buffer_offset == m_buffer_size);
m_buffer_index = (m_buffer_index + 1) % m_buffer_count;
auto buf = m_buffers[m_buffer_index];
// Buffer for new data must not in use
assert(buf.use_count() == 2);
m_buffer_size = read_stream(buf, m_buffer_capacity);
m_buffer_offset = 0;
};
size_t
Reader::read_stream(std::shared_ptr<char[]> data, size_t data_size)
{
m_istream.read(data.get(), data_size);
if (!m_istream.good() && !m_istream.eof()) {
throw Error("cannot read from stream");
}
return m_istream.gcount();
};
Writer::Writer(std::ostream &ostream, size_t buffer_capacity)
: m_ostream(ostream), m_buffer_size(0), m_buffer_capacity(buffer_capacity)
{
try {
m_buffer = std::make_unique<char[]>(m_buffer_capacity);
} catch (const std::bad_alloc &e) {
throw Error("cannot allocate buffer for output stream data");
}
};
Writer::~Writer() { flush_buffer(); };
void
Writer::write(const char *data, size_t data_size)
{
size_t free{m_buffer_capacity - m_buffer_size};
if (data_size <= free) {
// There is free space in the buffer
write_buffer(data, data_size);
} else {
// No free space
flush_buffer();
if (data_size <= m_buffer_capacity) {
// Data fits into the buffer
write_buffer(data, data_size);
} else {
// Doesn't fit
write_stream(data, data_size);
}
}
};
void
Writer::write_buffer(const char *data, size_t data_size)
{
memcpy(reinterpret_cast<char *>(m_buffer.get()) + m_buffer_size, data,
data_size);
m_buffer_size += data_size;
};
void
Writer::flush_buffer()
{
write_stream(m_buffer.get(), m_buffer_size);
m_buffer_size = 0;
};
void
Writer::write_stream(const char *data, size_t data_size)
{
m_ostream.write(data, data_size);
if (!m_ostream) {
throw Error("cannot write to output stream");
}
};
} // namespace BufferedStream
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