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Avoid a parser allocation using non-flat buffer:

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When the parser is presented with an input buffer
sequence with length greater than one, the input is
flattened using stack space instead of dynamic
allocation if the buffer size is no greater than 8192.
This commit is contained in:
Vinnie Falco
2017-07-20 08:12:19 -07:00
parent 3c453209fe
commit ff8be0e931
3 changed files with 45 additions and 33 deletions
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include/beast/http/impl/basic_parser.ipp
+37 -30
View File
@@ -88,9 +88,35 @@ put(ConstBufferSequence const& buffers,
static_assert(is_const_buffer_sequence<
ConstBufferSequence>::value,
"ConstBufferSequence requirements not met");
auto const buffer = maybe_flatten(buffers);
using boost::asio::buffer_cast;
using boost::asio::buffer_copy;
using boost::asio::buffer_size;
auto const p = buffers.begin();
auto const last = buffers.end();
if(p == last)
return 0;
if(std::next(p) == last)
{
// single buffer
auto const b = *p;
return put(boost::asio::const_buffers_1{
buffer_cast<char const*>(b),
buffer_size(b)}, ec);
}
auto const size = buffer_size(buffers);
if(size <= max_stack_buffer)
return put_from_stack(size, buffers, ec);
if(size > buf_len_)
{
// reallocate
buf_.reset(new char[size]);
buf_len_ = size;
}
// flatten
buffer_copy(boost::asio::buffer(
buf_.get(), buf_len_), buffers);
return put(boost::asio::const_buffers_1{
buffer.data(), buffer.size()}, ec);
buf_.get(), buf_len_}, ec);
}
template<bool isRequest, class Derived>
@@ -209,37 +235,18 @@ put_eof(error_code& ec)
template<bool isRequest, class Derived>
template<class ConstBufferSequence>
inline
string_view
std::size_t
basic_parser<isRequest, Derived>::
maybe_flatten(
ConstBufferSequence const& buffers)
put_from_stack(std::size_t size,
ConstBufferSequence const& buffers,
error_code& ec)
{
using boost::asio::buffer_cast;
char buf[max_stack_buffer];
using boost::asio::buffer;
using boost::asio::buffer_copy;
using boost::asio::buffer_size;
auto const p = buffers.begin();
auto const last = buffers.end();
if(p == last)
return {nullptr, 0};
if(std::next(p) == last)
{
// single buffer
auto const b = *p;
return {buffer_cast<char const*>(b),
buffer_size(b)};
}
auto const len = buffer_size(buffers);
if(len > buf_len_)
{
// reallocate
buf_.reset(new char[len]);
buf_len_ = len;
}
// flatten
buffer_copy(boost::asio::buffer(
buf_.get(), buf_len_), buffers);
return {buf_.get(), len};
buffer_copy(buffer(buf, sizeof(buf)), buffers);
return put(boost::asio::const_buffers_1{
buf, size}, ec);
}
template<bool isRequest, class Derived>