http2, async-wrap: introduce AliasedBuffer class #15077
responding to PR feedback: cleaning up whitespace, snake-casing membe…
…r/variable names, adding const, some other stuff...
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -26,27 +26,24 @@ template <class NativeT, class V8T> | |
| class AliasedBuffer { | ||
| public: | ||
| AliasedBuffer(v8::Isolate* isolate, const size_t count) : | ||
| isolate_(isolate), | ||
| count_(count), | ||
| byte_offset_(0), | ||
| free_buffer_(true) { | ||
| const v8::HandleScope handle_scope(isolate_); | ||
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| const size_t sizeInBytes = sizeof(NativeT) * count; | ||
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| // allocate native buffer | ||
| buffer_ = Calloc<NativeT>(count); | ||
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| // allocate v8 ArrayBuffer | ||
| v8::Local<v8::ArrayBuffer> ab = v8::ArrayBuffer::New( | ||
| isolate_, buffer_, sizeInBytes); | ||
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| // allocate v8 TypedArray | ||
| v8::Local<V8T> js_array = V8T::New(ab, byte_offset_, count); | ||
| js_array_ = v8::Global<V8T>(isolate, js_array); | ||
| } | ||
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| /** | ||
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@@ -58,40 +55,40 @@ class AliasedBuffer { | |
| * Note that byte_offset must by aligned by sizeof(NativeT). | ||
| */ | ||
| AliasedBuffer( | ||
| v8::Isolate* isolate, | ||
| const size_t byte_offset, | ||
| const size_t count, | ||
| const AliasedBuffer<uint8_t, | ||
| v8::Uint8Array>& backing_buffer) : | ||
| isolate_(isolate), | ||
| count_(count), | ||
| byte_offset_(byte_offset), | ||
| free_buffer_(false) { | ||
| const v8::HandleScope handle_scope(isolate_); | ||
| // validate that the byte_offset is aligned with sizeof(NativeT) | ||
| CHECK_EQ(byte_offset & (sizeof(NativeT) - 1), 0); | ||
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Contributor
There was a problem hiding this comment. This is missing a range check to make sure the byte length of this instance fits within the CHECK_LE(sizeof(NativeT) * count, backing_buffer.GetArrayBuffer()->ByteLength() - byte_offset);
Member
There was a problem hiding this comment. Fwiw, both that check and the existing check are also verified within V8
Contributor
There was a problem hiding this comment. @addaleax Possibly in a debug build, but I just created a module that creates a |
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| buffer_ = reinterpret_cast<NativeT*>( | ||
| const_cast<uint8_t*>(backing_buffer.GetNativeBuffer() + byte_offset)); | ||
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| v8::Local<v8::ArrayBuffer> ab = backing_buffer.GetArrayBuffer(); | ||
| v8::Local<V8T> js_array = V8T::New(ab, byte_offset, count); | ||
| js_array_ = v8::Global<V8T>(isolate, js_array); | ||
| } | ||
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| AliasedBuffer(const AliasedBuffer& that) : | ||
| isolate_(that.isolate_), | ||
| count_(that.count_), | ||
| byte_offset_(that.byte_offset_), | ||
| buffer_(that.buffer_), | ||
| free_buffer_(false) { | ||
| js_array_ = v8::Global<V8T>(that.isolate_, that.GetJSArray()); | ||
| } | ||
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| ~AliasedBuffer() { | ||
| if (free_buffer_ && buffer_ != NULL) { | ||
| free(buffer_); | ||
| } | ||
| js_array_.Reset(); | ||
| } | ||
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| /** | ||
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@@ -100,74 +97,74 @@ class AliasedBuffer { | |
| */ | ||
| class Reference { | ||
| public: | ||
| Reference(AliasedBuffer<NativeT, V8T>* aliased_buffer, size_t index) : | ||
| aliased_buffer_(aliased_buffer), | ||
| index_(index) { | ||
| } | ||
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| Reference(const Reference& that) : | ||
| aliased_buffer_(that.aliased_buffer_), | ||
| index_(that.index_) { | ||
| } | ||
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| inline Reference& operator=(const NativeT &val) { | ||
| aliased_buffer_->SetValue(index_, val); | ||
| return *this; | ||
| } | ||
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| operator NativeT() const { | ||
| return aliased_buffer_->GetValue(index_); | ||
| } | ||
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| private: | ||
| AliasedBuffer<NativeT, V8T>* aliased_buffer_; | ||
| size_t index_; | ||
| }; | ||
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| /** | ||
| * Get the underlying v8 TypedArray overlayed on top of the native buffer | ||
| */ | ||
| v8::Local<V8T> GetJSArray() const { | ||
| return js_array_.Get(isolate_); | ||
| } | ||
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| /** | ||
| * Get the underlying v8::ArrayBuffer underlying the TypedArray and | ||
| * overlaying the native buffer | ||
| */ | ||
| v8::Local<v8::ArrayBuffer> GetArrayBuffer() const { | ||
| return GetJSArray()->Buffer(); | ||
| } | ||
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| /** | ||
| * Get the underlying native buffer. Note that all reads/writes should occur | ||
| * through the GetValue/SetValue/operator[] methods | ||
| */ | ||
| inline const NativeT* GetNativeBuffer() const { | ||
| return buffer_; | ||
| } | ||
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| /** | ||
| * Synonym for GetBuffer() | ||
| */ | ||
| inline const NativeT* operator * () const { | ||
| return GetNativeBuffer(); | ||
| } | ||
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| /** | ||
| * Set position index to given value. | ||
| */ | ||
| inline void SetValue(const size_t index, NativeT value) { | ||
| CHECK_LT(index, count_); | ||
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Member
There was a problem hiding this comment. (same goes for this one, I assume) |
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| buffer_[index] = value; | ||
| } | ||
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| /** | ||
| * Get value at position index | ||
| */ | ||
| inline const NativeT GetValue(const size_t index) const { | ||
| CHECK_LT(index, count_); | ||
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Member
There was a problem hiding this comment. @trevnorris I’m pretty sure the reported performance difference is due to this check, it’s the only visible difference in the generated machine code. I’d suggest wrapping it in
Contributor
There was a problem hiding this comment. confirmed. that is where the performance hit is coming from. wrapping it sounds good
Author
There was a problem hiding this comment. this and the SetValue check are now in debug-only builds. |
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| return buffer_[index]; | ||
| } | ||
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| /** | ||
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@@ -178,16 +175,16 @@ class AliasedBuffer { | |
| } | ||
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| NativeT operator[](size_t index) const { | ||
| return GetValue(index); | ||
| } | ||
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| private: | ||
| v8::Isolate* const isolate_; | ||
| size_t count_; | ||
| size_t byte_offset_; | ||
| NativeT* buffer_; | ||
| v8::Global<V8T> js_array_; | ||
| bool free_buffer_; | ||
| }; | ||
| } // namespace node | ||
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if we don't expect a value of
count == 0then pleaseCHECK_GT(count, 0). if we do expect that possibility then please directly assignnullptrbecauseUncheckedCalloc()will still force ancount = 1allocation.There was a problem hiding this comment.
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added
CHECK_GT(count, 0)