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/*
* Copyright © 2019 Christian Persch
*
* This library is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published
* by the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library. If not, see <https://www.gnu.org/licenses/>.
*/
#pragma once
#include <memory>
#include <unicode/errorcode.h>
#include <unicode/ucnv.h>
namespace vte::base {
/*
* vte::base::Decoder:
*
* Converts input from any ICU-supported charset to UTF-32, one input byte at a time.
*/
class ICUDecoder {
public:
using converter_shared_type = std::shared_ptr<UConverter>;
ICUDecoder(converter_shared_type charset_converter,
converter_shared_type u32_converter)
: m_charset_converter{charset_converter},
m_u32_converter{u32_converter}
{ }
~ICUDecoder() noexcept { }
ICUDecoder(ICUDecoder const&) = delete;
ICUDecoder(ICUDecoder&&) = delete;
ICUDecoder& operator=(ICUDecoder const&) = delete;
ICUDecoder& operator=(ICUDecoder&&) = delete;
/*
* eNothing: there is no output character available
* eSomething: there is an output character available
* eError: an error occurred; you must call reset()
*/
enum class Result {
eNothing = 0,
eSomething = 1,
eError = 2,
};
constexpr auto const& error() const noexcept { return m_err; }
constexpr auto codepoint() const noexcept { return m_u32_buffer[m_index]; }
Result decode(uint8_t const** sptr,
bool flush = false) noexcept;
void reset() noexcept;
/*
* pending():
*
* Returns whether the converter has output pending (i.e. will produce more
* output without consuming more input.
*/
constexpr auto pending() const noexcept
{
/* Due to the way we drive the ICU converter and the way ICU converters work
* by first writing out any internally buffered output before consuming more
* input, this should be a safe guess about whether there is pending output.
*/
return m_index + 1 < m_available;
}
private:
enum class State {
eInput = 0,
eOutput = 1,
eError = 2,
};
State m_state{State::eInput};
converter_shared_type m_charset_converter;
converter_shared_type m_u32_converter;
icu::ErrorCode m_err{};
int m_available{0}; /* how many output characters are available */
int m_index{0}; /* index of current output character in m_u32_buffer */
/* 32 is large enough to avoid UCNV_EXT_MAX_UCHARS and UCNV_ERROR_BUFFER_LENGTH,
* see comment in icu4c/source/common/ucnv.cpp:ucnv_convertEx().
*/
char32_t m_u32_buffer[32];
char16_t m_u16_buffer[32];
constexpr auto u16_buffer() noexcept { return &m_u16_buffer[0]; }
constexpr auto u32_buffer() noexcept { return &m_u32_buffer[0]; }
constexpr auto u16_buffer_end() const noexcept { return &m_u16_buffer[0] + 32; }
constexpr auto u32_buffer_end() const noexcept { return &m_u32_buffer[0] + 32; }
}; // class ICUDecoder
} // namespace vte::base
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