serenity/AK/Stream.h

/*
 * Copyright (c) 2020, the SerenityOS developers.
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <AK/Concepts.h>
#include <AK/Endian.h>
#include <AK/Forward.h>
#include <AK/Optional.h>
#include <AK/Span.h>
#include <AK/StdLibExtras.h>

namespace AK::Detail {

class Stream {
public:
    virtual ~Stream() { VERIFY(!has_any_error()); }

    virtual bool has_recoverable_error() const { return m_recoverable_error; }
    virtual bool has_fatal_error() const { return m_fatal_error; }
    virtual bool has_any_error() const { return has_recoverable_error() || has_fatal_error(); }

    virtual bool handle_recoverable_error()
    {
        VERIFY(!has_fatal_error());
        return exchange(m_recoverable_error, false);
    }
    virtual bool handle_fatal_error() { return exchange(m_fatal_error, false); }
    virtual bool handle_any_error()
    {
        if (has_any_error()) {
            m_recoverable_error = false;
            m_fatal_error = false;

            return true;
        }

        return false;
    }

    ErrorOr<void> try_handle_any_error()
    {
        if (!handle_any_error())
            return {};
        return Error::from_string_literal("Stream error");
    }

    virtual void set_recoverable_error() const { m_recoverable_error = true; }
    virtual void set_fatal_error() const { m_fatal_error = true; }

private:
    mutable bool m_recoverable_error { false };
    mutable bool m_fatal_error { false };
};

}

namespace AK {

class InputStream : public virtual Detail::Stream {
public:
    // Reads at least one byte unless none are requested or none are available. Does nothing
    // and returns zero if there is already an error.
    virtual size_t read(Bytes) = 0;

    // If this function returns true, then no more data can be read. If read(Bytes) previously
    // returned zero even though bytes were requested, then the inverse is true as well.
    virtual bool unreliable_eof() const = 0;

    // Some streams additionally define a method with the signature:
    //
    //     bool eof() const;
    //
    // This method has the same semantics as unreliable_eof() but returns true if and only if no
    // more data can be read. (A failed read is not necessary.)

    virtual bool read_or_error(Bytes) = 0;
    virtual bool discard_or_error(size_t count) = 0;
};

class OutputStream : public virtual Detail::Stream {
public:
    virtual size_t write(ReadonlyBytes) = 0;
    virtual bool write_or_error(ReadonlyBytes) = 0;
};

class DuplexStream
    : public InputStream
    , public OutputStream {
};

inline InputStream& operator>>(InputStream& stream, Bytes bytes)
{
    stream.read_or_error(bytes);
    return stream;
}
inline OutputStream& operator<<(OutputStream& stream, ReadonlyBytes bytes)
{
    stream.write_or_error(bytes);
    return stream;
}

template<typename T>
InputStream& operator>>(InputStream& stream, LittleEndian<T>& value)
{
    return stream >> Bytes { &value.m_value, sizeof(value.m_value) };
}
template<typename T>
OutputStream& operator<<(OutputStream& stream, LittleEndian<T> value)
{
    return stream << ReadonlyBytes { &value.m_value, sizeof(value.m_value) };
}

template<typename T>
InputStream& operator>>(InputStream& stream, BigEndian<T>& value)
{
    return stream >> Bytes { &value.m_value, sizeof(value.m_value) };
}
template<typename T>
OutputStream& operator<<(OutputStream& stream, BigEndian<T> value)
{
    return stream << ReadonlyBytes { &value.m_value, sizeof(value.m_value) };
}

template<typename T>
InputStream& operator>>(InputStream& stream, Optional<T>& value)
{
    T temporary;
    stream >> temporary;
    value = temporary;
    return stream;
}

template<Integral I>
InputStream& operator>>(InputStream& stream, I& value)
{
    stream.read_or_error({ &value, sizeof(value) });
    return stream;
}
template<Integral I>
OutputStream& operator<<(OutputStream& stream, I value)
{
    stream.write_or_error({ &value, sizeof(value) });
    return stream;
}

#ifndef KERNEL

template<FloatingPoint F>
InputStream& operator>>(InputStream& stream, F& value)
{
    stream.read_or_error({ &value, sizeof(value) });
    return stream;
}
template<FloatingPoint F>
OutputStream& operator<<(OutputStream& stream, F value)
{
    stream.write_or_error({ &value, sizeof(value) });
    return stream;
}

#endif

}