[ios] Using UnsafeBufferPointer to skip data copying and boost performance. (#2686)

* [ios] Using UnsafeBufferPointer to skip data copying and boost performance.

* [ios] Fix the extra data copying caused by using  and move the guard let condition to be earlier

Author: kikiloveswift

spine-cpp/spine-cpp-lite/spine-cpp-lite-codegen.py

@@ -239,8 +239,6 @@ def write(self):
 
     if swift_return_type_is_array:
       body += self.write_array_call(num_function_name, function_call)
-      body += inset + inset
-      body += "}"
     else:
       if not self.spine_function.return_type == "void":
         body += "return "
@@ -305,24 +303,46 @@ def write_c_function_call(self, spine_params):
          function_call += " != 0"
 
       return function_call
-    
-  def write_array_call(self, num_function_name, function_call):
-    array_call = f"let num = Int({num_function_name}({self.spine_object.var_name}))"
+  
+  def write_array_spine_class(self, num_function_name, function_call):
+    array_call = f"let ptr = {function_call}"
     array_call += "\n"
     array_call += inset + inset
-    array_call += f"let ptr = {function_call}"
+    array_call += "guard let validPtr = ptr else { return [] }"
     array_call += "\n"
     array_call += inset + inset
-    array_call += "return (0..<num).compactMap {"
+    array_call += f"let num = Int({num_function_name}({self.spine_object.var_name}))"
+    array_call += "\n"
+    array_call += inset + inset
+    array_call += "let buffer = UnsafeBufferPointer(start: validPtr, count: num)"
+    array_call += "\n"
+    array_call += inset + inset
+    array_call += "return buffer.compactMap {"
     array_call += "\n"
     array_call += inset + inset + inset
-
+    array_call += "$0.flatMap { .init($0) }"
+    array_call += "\n"
+    array_call += inset + inset
+    array_call += "}"
+    return array_call
+    
+  def write_array_call(self, num_function_name, function_call):
     if self.spine_function.isReturningSpineClass():
-        array_call += "ptr?[$0].flatMap { .init($0) }" 
-    else:
-      array_call += "ptr?[$0]"
+       return self.write_array_spine_class(num_function_name, function_call)
+    array_call = f"let ptr = {function_call}"
+    array_call += "\n"
+    array_call += inset + inset
+    array_call += "guard let validPtr = ptr else { return [] }"
+    array_call += "\n"
+    array_call += inset + inset
+    array_call += f"let num = Int({num_function_name}({self.spine_object.var_name}))"
+    array_call += "\n"
+    array_call += inset + inset
 
+    array_call += "let buffer = UnsafeBufferPointer(start: validPtr, count: num)"
     array_call += "\n"
+    array_call += inset + inset
+    array_call += "return Array(buffer)"
     return array_call
 
   def write_dispose_call(self):

spine-ios/Sources/Spine/Extensions/RenderCommand+Vertices.swift

@@ -10,7 +10,7 @@ extension RenderCommand {
         let positions = positions(numVertices: numVertices)
         let uvs = uvs(numVertices: numVertices)
         let colors = colors(numVertices: numVertices)
-        
+        vertices.reserveCapacity(indices.count)
         for i in 0..<indices.count {
             let index = Int(indices[i])
 

spine-ios/Sources/Spine/Spine.Generated+Extensions.swift

@@ -215,19 +215,25 @@ internal extension RenderCommand {
     func positions(numVertices: Int) -> [Float] {
         let num = numVertices * 2
         let ptr = spine_render_command_get_positions(wrappee)
-        return (0..<num).compactMap { ptr?[$0] }
+        guard let validPtr = ptr else { return [] }
+        let buffer = UnsafeBufferPointer(start: validPtr, count: num)
+        return Array(buffer)
     }
 
     func uvs(numVertices: Int) -> [Float] {
         let num = numVertices * 2
         let ptr = spine_render_command_get_uvs(wrappee)
-        return (0..<num).compactMap { ptr?[$0] }
+        guard let validPtr = ptr else { return [] }
+        let buffer = UnsafeBufferPointer(start: validPtr, count: num)
+        return Array(buffer)
     }
 
     func colors(numVertices: Int) ->[Int32] {
         let num = numVertices
         let ptr = spine_render_command_get_colors(wrappee)
-        return (0..<num).compactMap { ptr?[$0] }
+        guard let validPtr = ptr else { return [] }
+        let buffer = UnsafeBufferPointer(start: validPtr, count: num)
+        return Array(buffer)
     }
 }