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author | Bruno de Oliveira Abinader <bruno@mapbox.com> | 2016-06-30 17:34:26 +0300 |
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committer | Bruno de Oliveira Abinader <bruno@mapbox.com> | 2016-06-30 17:56:23 +0300 |
commit | ad081e698a463ed943327ee6a4457f92e9434dd1 (patch) | |
tree | 9cd8922e84af89374e83155126c9615db17f7782 /include | |
parent | 03f30f52078262c1dfaf60ffb35a287a63ff9a59 (diff) | |
download | qtlocation-mapboxgl-ad081e698a463ed943327ee6a4457f92e9434dd1.tar.gz |
[core] Added CharArrayBuffer
Implements a custom std::streambuf to avoid creating temporary
std::string objects and thus optimizing image decode.
Suggested by @artemp in
https://github.com/mapbox/mapbox-gl-native/pull/5417#issuecomment-227700063.
Diffstat (limited to 'include')
-rw-r--r-- | include/mbgl/util/char_array_buffer.hpp | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/include/mbgl/util/char_array_buffer.hpp b/include/mbgl/util/char_array_buffer.hpp new file mode 100644 index 0000000000..177f005477 --- /dev/null +++ b/include/mbgl/util/char_array_buffer.hpp @@ -0,0 +1,55 @@ +#pragma once + +#include <streambuf> + +namespace mbgl { +namespace util { + +// ref https://artofcode.wordpress.com/2010/12/12/deriving-from-stdstreambuf/ + +class CharArrayBuffer : public std::streambuf +{ +public: + CharArrayBuffer(char const* data, std::size_t size) + : begin_(data), end_(data + size), current_(data) {} + +private: + int_type underflow() final { + if (current_ == end_) { + return traits_type::eof(); + } + return traits_type::to_int_type(*current_); + } + + int_type uflow() final { + if (current_ == end_) { + return traits_type::eof(); + } + return traits_type::to_int_type(*current_++); + } + + int_type pbackfail(int_type ch) final { + if (current_ == begin_ || (ch != traits_type::eof() && ch != current_[-1])) { + return traits_type::eof(); + } + return traits_type::to_int_type(*--current_); + } + + std::streamsize showmanyc() final { + return end_ - current_; + } + + pos_type seekoff(off_type off, std::ios_base::seekdir dir, std::ios_base::openmode) final { + if (dir == std::ios_base::beg) current_ = std::min(begin_ + off, end_); + else if (dir == std::ios_base::cur) current_ = std::min(current_ + off, end_); + else current_ = std::max(end_ - off, begin_); // dir == std::ios_base::end + return pos_type(off_type(current_ - begin_)); + } + + char const * const begin_; + char const * const end_; + char const * current_; +}; + +} // namespace util +} // namespace mbgl |