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authorBruno de Oliveira Abinader <bruno@mapbox.com>2016-06-30 17:34:26 +0300
committerBruno de Oliveira Abinader <bruno@mapbox.com>2016-06-30 17:56:23 +0300
commitad081e698a463ed943327ee6a4457f92e9434dd1 (patch)
tree9cd8922e84af89374e83155126c9615db17f7782 /include
parent03f30f52078262c1dfaf60ffb35a287a63ff9a59 (diff)
downloadqtlocation-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.hpp55
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