[Swift] Adds new API to reduce memory copying within swift (#8484)

* Adds new API to reduce memory copying within swift

Adds new storage container _InternalByteBuffer which
will be holding the data that will be created within the swift
lib, however reading data will be redirected to ByteBuffer, which
should be able to handle all types of data that swift provide without
the need to copy the data itself. This is due to holding a reference to
the data.

Replaces assumingMemoryBinding with bindMemory which is safer

Adds function that provides access to a UnsafeBufferPointer for
scalars and NativeStructs within swift

Updates docs

Suppress compilation warnings by replacing var with let

Using overflow operators within swift to improve performance

Adds tests for GRPC message creation from a retained _InternalByteBuffer

benchmarks/swift/Benchmarks/FlatbuffersBenchmarks/FlatbuffersBenchmarks.swift

@@ -15,8 +15,8 @@
  */
 
 import Benchmark
-import CoreFoundation
 import FlatBuffers
+import Foundation
 
 @usableFromInline
 struct AA: NativeStruct {
@@ -29,6 +29,15 @@ struct AA: NativeStruct {
 }
 
 let benchmarks = {
+  let oneGB: Int32 = 1_024_000_000
+  let data = {
+    var array = [8888.88, 8888.88]
+    var data = Data()
+    array.withUnsafeBytes { ptr in
+      data.append(contentsOf: ptr)
+    }
+    return data
+  }()
   let ints: [Int] = Array(repeating: 42, count: 100)
   let bytes: [UInt8] = Array(repeating: 42, count: 100)
   let str10 = (0...9).map { _ -> String in "x" }.joined()
@@ -73,12 +82,25 @@ let benchmarks = {
 
   Benchmark("Allocating 1GB", configuration: singleConfiguration) { benchmark in
     for _ in benchmark.scaledIterations {
-      blackHole(FlatBufferBuilder(initialSize: 1_024_000_000))
+      blackHole(FlatBufferBuilder(initialSize: oneGB))
+    }
+  }
+
+  Benchmark(
+    "Allocating ByteBuffer 1GB",
+    configuration: singleConfiguration)
+  { benchmark in
+    let memory = UnsafeMutableRawPointer.allocate(
+      byteCount: 1_024_000_000,
+      alignment: 1)
+    benchmark.startMeasurement()
+    for _ in benchmark.scaledIterations {
+      blackHole(ByteBuffer(assumingMemoryBound: memory, capacity: Int(oneGB)))
     }
   }
 
   Benchmark("Clearing 1GB", configuration: singleConfiguration) { benchmark in
-    var fb = FlatBufferBuilder(initialSize: 1_024_000_000)
+    var fb = FlatBufferBuilder(initialSize: oneGB)
     benchmark.startMeasurement()
     for _ in benchmark.scaledIterations {
       blackHole(fb.clear())
@@ -158,6 +180,26 @@ let benchmarks = {
     }
   }
 
+  Benchmark(
+    "FlatBufferBuilder Start table",
+    configuration: kiloConfiguration)
+  { benchmark in
+    var fb = FlatBufferBuilder(initialSize: 1024 * 1024 * 32)
+    benchmark.startMeasurement()
+    for _ in benchmark.scaledIterations {
+      let s = fb.startTable(with: 4)
+      blackHole(fb.endTable(at: s))
+    }
+  }
+
+  Benchmark("Struct") { benchmark in
+    var fb = FlatBufferBuilder(initialSize: 1024 * 1024 * 32)
+    benchmark.startMeasurement()
+    for _ in benchmark.scaledIterations {
+      blackHole(fb.create(struct: array.first!))
+    }
+  }
+
   Benchmark("Structs") { benchmark in
     let rawSize = ((16 * 5) * benchmark.scaledIterations.count) / 1024
     var fb = FlatBufferBuilder(initialSize: Int32(rawSize * 1600))
@@ -176,7 +218,7 @@ let benchmarks = {
     let start = fb.startTable(with: 1)
     fb.add(offset: vector, at: 4)
     let root = Offset(offset: fb.endTable(at: start))
-    fb.finish(offset: root)
+    blackHole(fb.finish(offset: root))
   }
 
   Benchmark("Vector of Offsets") { benchmark in
@@ -198,4 +240,11 @@ let benchmarks = {
       blackHole(fb.endTable(at: s))
     }
   }
+
+  Benchmark("Reading Doubles") { benchmark in
+    let byteBuffer = ByteBuffer(data: data)
+    for _ in benchmark.scaledIterations {
+      blackHole(byteBuffer.read(def: Double.self, position: 0))
+    }
+  }
 }