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// license:BSD-3-Clause
// copyright-holders:Vas Crabb
/***************************************************************************
ioprocsfill.h
Wrappers that automatically fill extra space
***************************************************************************/
#ifndef MAME_LIB_UTIL_IOPROCSFILL_H
#define MAME_LIB_UTIL_IOPROCSFILL_H
#pragma once
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <system_error>
namespace util {
template <std::uint8_t DefaultFiller>
class fill_wrapper_base
{
public:
std::uint8_t get_filler() const noexcept
{
return m_filler;
}
void set_filler(std::uint8_t filler) noexcept
{
m_filler = filler;
}
private:
std::uint8_t m_filler = DefaultFiller;
};
template <typename Base, std::uint8_t DefaultFiller = 0U>
class read_stream_fill_wrapper : public Base, public virtual fill_wrapper_base<DefaultFiller>
{
public:
using Base::Base;
virtual std::error_condition read_some(void *buffer, std::size_t length, std::size_t &actual) noexcept override
{
// not atomic with respect to other read/write calls
actual = 0U;
std::error_condition err;
std::size_t chunk;
do
{
err = Base::read_some(
reinterpret_cast<std::uint8_t *>(buffer) + actual,
length - actual,
chunk);
actual += chunk;
}
while ((length > actual) && ((!err && chunk) || (std::errc::interrupted == err)));
assert(length >= actual);
std::fill(
reinterpret_cast<std::uint8_t *>(buffer) + actual,
reinterpret_cast<std::uint8_t *>(buffer) + length,
fill_wrapper_base<DefaultFiller>::get_filler());
return err;
}
};
template <typename Base, std::uint8_t DefaultFiller = 0U>
class random_read_fill_wrapper : public read_stream_fill_wrapper<Base, DefaultFiller>
{
public:
using read_stream_fill_wrapper<Base, DefaultFiller>::read_stream_fill_wrapper;
virtual std::error_condition read_some_at(std::uint64_t offset, void *buffer, std::size_t length, std::size_t &actual) noexcept override
{
// not atomic with respect to other read/write calls
actual = 0U;
std::error_condition err;
std::size_t chunk;
do
{
err = Base::read_some_at(
offset,
reinterpret_cast<std::uint8_t *>(buffer) + actual,
length - actual,
chunk);
offset += chunk;
actual += chunk;
}
while ((length > actual) && ((!err && chunk) || (std::errc::interrupted == err)));
assert(length >= actual);
std::fill(
reinterpret_cast<std::uint8_t *>(buffer) + actual,
reinterpret_cast<std::uint8_t *>(buffer) + length,
fill_wrapper_base<DefaultFiller>::get_filler());
return err;
}
};
template <typename Base, std::uint8_t DefaultFiller = 0U, std::size_t FillBlock = 1024U>
class random_write_fill_wrapper : public Base, public virtual fill_wrapper_base<DefaultFiller>
{
public:
using Base::Base;
virtual std::error_condition write_some(void const *buffer, std::size_t length, std::size_t &actual) noexcept override
{
// not atomic with respect to other read/write calls
std::error_condition err;
actual = 0U;
std::uint64_t offset;
std::uint64_t current;
err = Base::tell(offset);
if (err)
return err;
err = Base::length(current);
if (err)
return err;
if (current < offset)
{
std::uint64_t unfilled = offset - current;
std::uint8_t fill_buffer[FillBlock];
std::fill(
fill_buffer,
fill_buffer + std::min<std::common_type_t<std::size_t, std::uint64_t> >(FillBlock, unfilled),
fill_wrapper_base<DefaultFiller>::get_filler());
do
{
std::size_t const chunk = std::min<std::common_type_t<std::size_t, std::uint64_t> >(FillBlock, unfilled);
std::size_t filled;
err = Base::write_some_at(current, fill_buffer, chunk, filled);
current += filled;
unfilled -= filled;
if (err && (std::errc::interrupted != err))
return err;
}
while (unfilled);
}
return Base::write_some(buffer, length, actual);
}
virtual std::error_condition write_some_at(std::uint64_t offset, void const *buffer, std::size_t length, std::size_t &actual) noexcept override
{
// not atomic with respect to other read/write calls
std::error_condition err;
std::uint64_t current;
err = Base::length(current);
if (!err && (current < offset))
{
std::uint64_t unfilled = offset - current;
std::uint8_t fill_buffer[FillBlock];
std::fill(
fill_buffer,
fill_buffer + std::min<std::common_type_t<std::size_t, std::uint64_t> >(FillBlock, unfilled),
fill_wrapper_base<DefaultFiller>::get_filler());
do
{
std::size_t const chunk = std::min<std::common_type_t<std::size_t, std::uint64_t> >(FillBlock, unfilled);
std::size_t filled;
err = Base::write_some_at(current, fill_buffer, chunk, filled);
current += filled;
unfilled -= filled;
}
while (unfilled && (!err || (std::errc::interrupted == err)));
}
if (err)
{
actual = 0U;
return err;
}
return Base::write_some_at(offset, buffer, length, actual);
}
};
template <typename Base, std::uint8_t DefaultFiller = 0U, std::size_t FillBlock = 1024U>
using random_read_write_fill_wrapper = random_write_fill_wrapper<random_read_fill_wrapper<Base, DefaultFiller>, DefaultFiller, FillBlock>;
} // namespace util
#endif // MAME_LIB_UTIL_IOPROCSFILL_H
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