// Copyright (c) 2020, The Monero Project
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#pragma once
#include <cassert>
#include <cstdint>
#include <cstring>
#include "byte_slice.h"
#include "span.h"
namespace epee
{
/*! \brief A partial drop-in replacement for `std::ostream`.
Only a few base `std::ostream` functions are implemented - enough for
rapidjson output currently.
Advantages over `std::stringstream` or `rapidjson::StringBuffer`:
- The internal buffer can be taken without a copy.
- The internal buffer can be given to `byte_slice` with zero
allocations for reference count.
- The internal buffer can be given to `zmq_msg_data_init` without a
copy or extra allocation.
an additional advantage over `std::stringstream`:
- Construction is significantly faster - the global `std::locale`
does not have to be acquired (global thread synchronization), and
an extra allocation for `std::stringbuf` is not needed (which is an
addition to the buffer inside of that object). */
class byte_stream
{
byte_buffer buffer_; //! Beginning of buffer
std::uint8_t* next_write_; //! Current write position
const std::uint8_t* end_; //! End of buffer
std::size_t increase_size_; //! Minimum buffer size increase
//! \post `requested <= available()`
void overflow(const std::size_t requested);
//! Ensures that at least `requested` bytes are available.
void check(const std::size_t requested)
{
const std::size_t remaining = available();
if (remaining < requested)
overflow(requested);
}
public:
using char_type = std::uint8_t;
using Ch = char_type;
//! \return Default minimum size increase on buffer overflow
static constexpr std::size_t default_increase() noexcept { return 4096; }
//! Increase internal buffer by at least `byte_stream_increase` bytes.
byte_stream() noexcept
: byte_stream(default_increase())
{}
//! Increase internal buffer by at least `increase` bytes.
explicit byte_stream(const std::size_t increase) noexcept
: buffer_(nullptr),
next_write_(nullptr),
end_(nullptr),
increase_size_(increase)
{}
byte_stream(byte_stream&& rhs) noexcept;
~byte_stream() noexcept = default;
byte_stream& operator=(byte_stream&& rhs) noexcept;
//! \return The minimum increase size on buffer overflow
std::size_t increase_size() const noexcept { return increase_size_; }
const std::uint8_t* data() const noexcept { return buffer_.get(); }
std::uint8_t* tellp() const noexcept { return next_write_; }
std::size_t available() const noexcept { return end_ - next_write_; }
std::size_t size() const noexcept { return next_write_ - buffer_.get(); }
std::size_t capacity() const noexcept { return end_ - buffer_.get(); }
//! Compatibility with rapidjson.
void Flush() const noexcept
{}
/*! Reserve at least `more` bytes.
\post `size() + more <= available()`.
\throw std::range_error if exceeding max `size_t` value.
\throw std::bad_alloc if allocation fails. */
void reserve(const std::size_t more)
{
check(more);
}
//! Reset write position, but do not release internal memory. \post `size() == 0`.
void clear() noexcept { next_write_ = buffer_.get(); }
/*! Copy `length` bytes starting at `ptr` to end of stream.
\throw std::range_error If exceeding max size_t value.
\throw std::bad_alloc If allocation fails. */
void write(const std::uint8_t* ptr, const std::size_t length)
{
check(length);
std::memcpy(tellp(), ptr, length);
next_write_ += length;
}
/*! Copy `length` bytes starting at `ptr` to end of stream.
\throw std::range_error if exceeding max `size_t` value.
\throw std::bad_alloc if allocation fails. */
void write(const char* ptr, const std::size_t length)
{
write(reinterpret_cast<const std::uint8_t*>(ptr), length);
}
/*! Copy `source` to end of stream.
\throw std::range_error if exceeding max `size_t` value.
\throw std::bad_alloc if allocation fails. */
void write(const epee::span<const std::uint8_t> source)
{
write(source.data(), source.size());
}
/*! Copy `source` to end of stream.
\throw std::range_error if exceeding max `size_t` value.
\throw std::bad_alloc if allocation fails. */
void write(const epee::span<const char> source)
{
write(source.data(), source.size());
}
/*! Copy `ch` to end of stream.
\throw std::range_error if exceeding max `size_t` value.
\throw std::bad_alloc if allocation fails. */
void put(const std::uint8_t ch)
{
check(1);
put_unsafe(ch);
}
/*! Copy `ch` to end of stream. Provides rapidjson compatability.
\throw std::range_error if exceeding max `size_t` value.
\throw std::bad_alloc if allocation fails. */
void Put(const std::uint8_t ch)
{
put(ch);
}
/*! Writes `ch` to end of stream without runtime capacity checks. Must use
`reserve` before calling this function. Primarily for use with
rapidjson, which writes characters at a time but reserves memory in
blocks. Most applications want to use `put` or `write`. */
void put_unsafe(const std::uint8_t ch) noexcept
{
assert(1 <= available());
*(tellp()) = ch;
++next_write_;
}
/*! Write `ch` to end of stream `count` times.
\throw std::range_error if exceeding max `size_t` value.
\throw std::bad_alloc if allocation fails. */
void put_n(const std::uint8_t ch, const std::size_t count)
{
check(count);
std::memset(tellp(), count, ch);
next_write_ += count;
}
/*! Copy `ch` to end of stream.
\throw std::range_error if exceeding max `size_t` value.
\throw std::bad_alloc if allocation fails. */
void push_back(const std::uint8_t ch)
{
put(ch);
}
//! \return The internal buffer. \post `size() == capacity() == 0`.
byte_buffer take_buffer() noexcept;
};
//! Compatability/optimization for rapidjson.
inline void PutReserve(byte_stream& dest, const std::size_t length)
{
dest.reserve(length);
}
//! Compatability/optimization for rapidjson.
inline void PutUnsafe(byte_stream& dest, const std::uint8_t ch)
{
dest.put_unsafe(ch);
}
//! Compability/optimization for rapidjson.
inline void PutN(byte_stream& dest, const std::uint8_t ch, const std::size_t count)
{
dest.put_n(ch, count);
}
} // epee
