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Internals: added ImSpanAllocator<> helper.

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This commit is contained in:
omar
2020-03-18 17:49:13 +01:00
committed by ocornut
parent 182115409a
commit 6dff061309
1 changed files with 21 additions and 1 deletions
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22
imgui_internal.h
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@@ -249,7 +249,7 @@ namespace ImStb
// - Helper: ImRect
// - Helper: ImBitArray
// - Helper: ImBitVector
// - Helper: ImSpan<>
// - Helper: ImSpan<>, ImSpanAllocator<>
// - Helper: ImPool<>
// - Helper: ImChunkStream<>
//-----------------------------------------------------------------------------
@@ -531,6 +531,26 @@ struct ImSpan
inline int index_from_ptr(const T* it) const { IM_ASSERT(it >= Data && it < DataEnd); const ptrdiff_t off = it - Data; return (int)off; }
};
// Helper: ImSpanAllocator<>
// Facilitate storing multiple chunks into a single large block (the "arena")
template<int CHUNKS>
struct ImSpanAllocator
{
char* BasePtr;
int TotalSize;
int CurrSpan;
int Offsets[CHUNKS];
ImSpanAllocator() { memset(this, 0, sizeof(*this)); }
inline void ReserveBytes(int n, size_t sz) { IM_ASSERT(n == CurrSpan && n < CHUNKS); Offsets[CurrSpan++] = TotalSize; TotalSize += (int)sz; }
inline int GetArenaSizeInBytes() { return TotalSize; }
inline void SetArenaBasePtr(void* base_ptr) { BasePtr = (char*)base_ptr; }
inline void* GetSpanPtrBegin(int n) { IM_ASSERT(n >= 0 && n < CHUNKS && CurrSpan == CHUNKS); return (void*)(BasePtr + Offsets[n]); }
inline void* GetSpanPtrEnd(int n) { IM_ASSERT(n >= 0 && n < CHUNKS && CurrSpan == CHUNKS); return (n + 1 < CHUNKS) ? BasePtr + Offsets[n + 1] : (void*)(BasePtr + TotalSize); }
template<typename T>
inline void GetSpan(int n, ImSpan<T>* span) { span->set((T*)GetSpanPtrBegin(n), (T*)GetSpanPtrEnd(n)); }
};
// Helper: ImPool<>
// Basic keyed storage for contiguous instances, slow/amortized insertion, O(1) indexable, O(Log N) queries by ID over a dense/hot buffer,
// Honor constructor/destructor. Add/remove invalidate all pointers. Indexes have the same lifetime as the associated object.