From 182115409ab3d4c76ea125c538c46ed38c332162 Mon Sep 17 00:00:00 2001
From: omar <omarcornut@gmail.com>
Date: Wed, 18 Mar 2020 12:20:53 +0100
Subject: [PATCH] Internals: added ImSpan helper structure + 2020/10/01
 stricter bound checking

---
 imgui_internal.h         | 29 +++++++++++++++++++++++++++++
 misc/natvis/imgui.natvis | 10 ++++++++++
 2 files changed, 39 insertions(+)

diff --git a/imgui_internal.h b/imgui_internal.h
index 3c6009d0..12e67fda 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -249,6 +249,7 @@ namespace ImStb
 // - Helper: ImRect
 // - Helper: ImBitArray
 // - Helper: ImBitVector
+// - Helper: ImSpan<>
 // - Helper: ImPool<>
 // - Helper: ImChunkStream<>
 //-----------------------------------------------------------------------------
@@ -502,6 +503,34 @@ struct IMGUI_API ImBitVector
     void            ClearBit(int n)             { IM_ASSERT(n < (Storage.Size << 5)); ImBitArrayClearBit(Storage.Data, n); }
 };
 
+// Helper: ImSpan<>
+// Pointing to a span of data we don't own.
+template<typename T>
+struct ImSpan
+{
+    T*                  Data;
+    T*                  DataEnd;
+
+    // Constructors, destructor
+    inline ImSpan()                                 { Data = DataEnd = NULL; }
+    inline ImSpan(T* data, int size)                { Data = data; DataEnd = data + size; }
+    inline ImSpan(T* data, T* data_end)             { Data = data; DataEnd = data_end; }
+
+    inline void         set(T* data, int size)      { Data = data; DataEnd = data + size; }
+    inline void         set(T* data, T* data_end)   { Data = data; DataEnd = data_end; }
+    inline int          size() const                { return (int)(ptrdiff_t)(DataEnd - Data); }
+    inline T&           operator[](int i)           { T* p = Data + i; IM_ASSERT(p >= Data && p < DataEnd); return *p; }
+    inline const T&     operator[](int i) const     { const T* p = Data + i; IM_ASSERT(p >= Data && p < DataEnd); return *p; }
+
+    inline T*           begin()                     { return Data; }
+    inline const T*     begin() const               { return Data; }
+    inline T*           end()                       { return DataEnd; }
+    inline const T*     end() const                 { return DataEnd; }
+
+    // Utilities
+    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: 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.
diff --git a/misc/natvis/imgui.natvis b/misc/natvis/imgui.natvis
index cc768bfb..25d72fb6 100644
--- a/misc/natvis/imgui.natvis
+++ b/misc/natvis/imgui.natvis
@@ -13,6 +13,16 @@
     </ArrayItems>
   </Expand>
 </Type>
+  
+<Type Name="ImSpan&lt;*&gt;">
+  <DisplayString>{{Size={DataEnd-Data} }}</DisplayString>
+  <Expand>
+    <ArrayItems>
+      <Size>DataEnd-Data</Size>
+      <ValuePointer>Data</ValuePointer>
+    </ArrayItems>
+  </Expand>
+</Type>
 
 <Type Name="ImVec2">
   <DisplayString>{{x={x,g} y={y,g}}}</DisplayString>