Vector Downward GetSize optimization (#6925)
* Added Google benchmarks (and gtests)
* Separate benchmark CMakeLists.txt to its own file
* Move output directory to target just flatbenchmark
* Reduced from encoding 210ns -> 188ns
* store size_ as uoffset_t
* fixed windows c4267 warning
diff --git a/benchmarks/CMakeLists.txt b/benchmarks/CMakeLists.txt
index 3d3032c..8d49c35 100644
--- a/benchmarks/CMakeLists.txt
+++ b/benchmarks/CMakeLists.txt
@@ -37,6 +37,7 @@
${CPP_BENCH_DIR}/benchmark_main.cpp
${CPP_FB_BENCH_DIR}/fb_bench.cpp
${CPP_RAW_BENCH_DIR}/raw_bench.cpp
+ ${CPP_BENCH_FB_GEN}
)
# Generate the flatbuffers benchmark code from the flatbuffers schema using
diff --git a/benchmarks/cpp/benchmark_main.cpp b/benchmarks/cpp/benchmark_main.cpp
index 720f94e..63807a5 100644
--- a/benchmarks/cpp/benchmark_main.cpp
+++ b/benchmarks/cpp/benchmark_main.cpp
@@ -93,4 +93,4 @@
std::unique_ptr<Bench> bench = NewRawBench();
Use(state, bench, buffer, 218812692406581874);
}
-BENCHMARK(BM_Raw_Use);
\ No newline at end of file
+BENCHMARK(BM_Raw_Use);
diff --git a/include/flatbuffers/flatbuffer_builder.h b/include/flatbuffers/flatbuffer_builder.h
index 7db48e3..ce40f7b 100644
--- a/include/flatbuffers/flatbuffer_builder.h
+++ b/include/flatbuffers/flatbuffer_builder.h
@@ -285,20 +285,20 @@
FieldLoc fl = { off, field };
buf_.scratch_push_small(fl);
num_field_loc++;
- max_voffset_ = (std::max)(max_voffset_, field);
+ if (field > max_voffset_) {
+ max_voffset_ = field;
+ }
}
// Like PushElement, but additionally tracks the field this represents.
template<typename T> void AddElement(voffset_t field, T e, T def) {
// We don't serialize values equal to the default.
if (IsTheSameAs(e, def) && !force_defaults_) return;
- auto off = PushElement(e);
- TrackField(field, off);
+ TrackField(field, PushElement(e));
}
template<typename T> void AddElement(voffset_t field, T e) {
- auto off = PushElement(e);
- TrackField(field, off);
+ TrackField(field, PushElement(e));
}
template<typename T> void AddOffset(voffset_t field, Offset<T> off) {
@@ -324,8 +324,9 @@
// Align to ensure GetSize() below is correct.
Align(sizeof(uoffset_t));
// Offset must refer to something already in buffer.
- FLATBUFFERS_ASSERT(off && off <= GetSize());
- return GetSize() - off + static_cast<uoffset_t>(sizeof(uoffset_t));
+ const uoffset_t size = GetSize();
+ FLATBUFFERS_ASSERT(off && off <= size);
+ return size - off + static_cast<uoffset_t>(sizeof(uoffset_t));
}
void NotNested() {
diff --git a/include/flatbuffers/vector_downward.h b/include/flatbuffers/vector_downward.h
index 8088b10..3391391 100644
--- a/include/flatbuffers/vector_downward.h
+++ b/include/flatbuffers/vector_downward.h
@@ -38,6 +38,7 @@
initial_size_(initial_size),
buffer_minalign_(buffer_minalign),
reserved_(0),
+ size_(0),
buf_(nullptr),
cur_(nullptr),
scratch_(nullptr) {}
@@ -49,6 +50,7 @@
initial_size_(other.initial_size_),
buffer_minalign_(other.buffer_minalign_),
reserved_(other.reserved_),
+ size_(other.size_),
buf_(other.buf_),
cur_(other.cur_),
scratch_(other.scratch_) {
@@ -86,6 +88,7 @@
reserved_ = 0;
cur_ = nullptr;
}
+ size_ = 0;
clear_scratch();
}
@@ -139,17 +142,18 @@
}
inline uint8_t *make_space(size_t len) {
- size_t space = ensure_space(len);
- cur_ -= space;
+ if (len) {
+ ensure_space(len);
+ cur_ -= len;
+ size_ += static_cast<uoffset_t>(len);
+ }
return cur_;
}
// Returns nullptr if using the DefaultAllocator.
Allocator *get_custom_allocator() { return allocator_; }
- uoffset_t size() const {
- return static_cast<uoffset_t>(reserved_ - static_cast<size_t>(cur_ - buf_));
- }
+ inline uoffset_t size() const { return size_; }
uoffset_t scratch_size() const {
return static_cast<uoffset_t>(scratch_ - buf_);
@@ -203,7 +207,11 @@
memset(make_space(zero_pad_bytes), 0, zero_pad_bytes);
}
- void pop(size_t bytes_to_remove) { cur_ += bytes_to_remove; }
+ void pop(size_t bytes_to_remove) {
+ cur_ += bytes_to_remove;
+ size_ -= static_cast<uoffset_t>(bytes_to_remove);
+ }
+
void scratch_pop(size_t bytes_to_remove) { scratch_ -= bytes_to_remove; }
void swap(vector_downward &other) {
@@ -213,6 +221,7 @@
swap(initial_size_, other.initial_size_);
swap(buffer_minalign_, other.buffer_minalign_);
swap(reserved_, other.reserved_);
+ swap(size_, other.size_);
swap(buf_, other.buf_);
swap(cur_, other.cur_);
swap(scratch_, other.scratch_);
@@ -234,6 +243,7 @@
size_t initial_size_;
size_t buffer_minalign_;
size_t reserved_;
+ uoffset_t size_;
uint8_t *buf_;
uint8_t *cur_; // Points at location between empty (below) and used (above).
uint8_t *scratch_; // Points to the end of the scratchpad in use.
