// Copyright (c) 2019, The Monero Project
//
// All rights reserved.
//
// 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.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// 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,
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include <atomic>
#include <cstdlib>
#include <cstring>
#include <limits>
#include <stdexcept>
#include <utility>
#include "byte_slice.h"
namespace epee
{
struct byte_slice_data
{
byte_slice_data() noexcept
: ref_count(1)
{}
virtual ~byte_slice_data() noexcept
{}
std::atomic<std::size_t> ref_count;
};
void release_byte_slice::operator()(byte_slice_data* ptr) const noexcept
{
if (ptr && --(ptr->ref_count) == 0)
{
ptr->~byte_slice_data();
free(ptr);
}
}
namespace
{
template<typename T>
struct adapted_byte_slice final : byte_slice_data
{
explicit adapted_byte_slice(T&& buffer)
: byte_slice_data(), buffer(std::move(buffer))
{}
virtual ~adapted_byte_slice() noexcept final override
{}
const T buffer;
};
// bytes "follow" this structure in memory slab
struct raw_byte_slice final : byte_slice_data
{
raw_byte_slice() noexcept
: byte_slice_data()
{}
virtual ~raw_byte_slice() noexcept final override
{}
};
/* This technique is not-standard, but allows for the reference count and
memory for the bytes (when given a list of spans) to be allocated in a
single call. In that situation, the dynamic sized bytes are after/behind
the raw_byte_slice class. The C runtime has to track the number of bytes
allocated regardless, so free'ing is relatively easy. */
template<typename T, typename... U>
std::unique_ptr<T, release_byte_slice> allocate_slice(std::size_t extra_bytes, U&&... args)
{
if (std::numeric_limits<std::size_t>::max() - sizeof(T) < extra_bytes)
throw std::bad_alloc{};
void* const ptr = malloc(sizeof(T) + extra_bytes);
if (ptr == nullptr)
throw std::bad_alloc{};
try
{
new (ptr) T{std::forward<U>(args)...};
}
catch (...)
{
free(ptr);
throw;
}
return std::unique_ptr<T, release_byte_slice>{reinterpret_cast<T*>(ptr)};
}
} // anonymous
byte_slice::byte_slice(byte_slice_data* storage, span<const std::uint8_t> portion) noexcept
: storage_(storage), portion_(portion)
{
if (storage_)
++(storage_->ref_count);
}
template<typename T>
byte_slice::byte_slice(const adapt_buffer, T&& buffer)
: storage_(nullptr), portion_(to_byte_span(to_span(buffer)))
{
if (!buffer.empty())
storage_ = allocate_slice<adapted_byte_slice<T>>(0, std::move(buffer));
}
byte_slice::byte_slice(std::initializer_list<span<const std::uint8_t>> sources)
: byte_slice()
{
std::size_t space_needed = 0;
for (const auto source : sources)
space_needed += source.size();
if (space_needed)
{
auto storage = allocate_slice<raw_byte_slice>(space_needed);
span<std::uint8_t> out{reinterpret_cast<std::uint8_t*>(storage.get() + 1), space_needed};
portion_ = {out.data(), out.size()};
for (const auto source : sources)
{
std::memcpy(out.data(), source.data(), source.size());
if (out.remove_prefix(source.size()) < source.size())
throw std::bad_alloc{}; // size_t overflow on space_needed
}
storage_ = std::move(storage);
}
}
byte_slice::byte_slice(std::string&& buffer)
: byte_slice(adapt_buffer{}, std::move(buffer))
{}
byte_slice::byte_slice(std::vector<std::uint8_t>&& buffer)
: byte_slice(adapt_buffer{}, std::move(buffer))
{}
byte_slice::byte_slice(byte_slice&& source) noexcept
: storage_(std::move(source.storage_)), portion_(source.portion_)
{
source.portion_ = epee::span<const std::uint8_t>{};
}
byte_slice& byte_slice::operator=(byte_slice&& source) noexcept
{
storage_ = std::move(source.storage_);
portion_ = source.portion_;
if (source.storage_ == nullptr)
source.portion_ = epee::span<const std::uint8_t>{};
return *this;
}
std::size_t byte_slice::remove_prefix(std::size_t max_bytes) noexcept
{
max_bytes = portion_.remove_prefix(max_bytes);
if (portion_.empty())
storage_ = nullptr;
return max_bytes;
}
byte_slice byte_slice::take_slice(const std::size_t max_bytes) noexcept
{
byte_slice out{};
std::uint8_t const* const ptr = data();
out.portion_ = {ptr, portion_.remove_prefix(max_bytes)};
if (portion_.empty())
out.storage_ = std::move(storage_); // no atomic inc/dec
else
out = {storage_.get(), out.portion_};
return out;
}
byte_slice byte_slice::get_slice(const std::size_t begin, const std::size_t end) const
{
if (end < begin || portion_.size() < end)
throw std::out_of_range{"bad slice range"};
if (begin == end)
return {};
return {storage_.get(), {portion_.begin() + begin, end - begin}};
}
} // epee
