[Swift] Improves vectors performance & arrays within lib (#8415)

* Improves vectors performance and adds a benchmark to vectors of offsets in swift

Improves performance for all arrays and for loops

Uses a tuple instead of allocating a struct each time we start iterating over fieldloc

Updates benchmark library

* Fixing swift Wasm ci

swift/Sources/FlatBuffers/ByteBuffer.swift

@@ -251,7 +251,7 @@ public struct ByteBuffer {
       ensureSpace(size: ptr.count)
       memcpy(
         _storage.memory.advanced(by: writerIndex &- ptr.count),
-        UnsafeRawPointer(ptr.baseAddress!),
+        ptr.baseAddress!,
         ptr.count)
       _writerSize = _writerSize &+ ptr.count
     }
@@ -264,9 +264,10 @@ public struct ByteBuffer {
   mutating func push<T: NativeStruct>(elements: [T]) {
     elements.withUnsafeBytes { ptr in
       ensureSpace(size: ptr.count)
-      _storage.memory
-        .advanced(by: writerIndex &- ptr.count)
-        .copyMemory(from: ptr.baseAddress!, byteCount: ptr.count)
+      memcpy(
+        _storage.memory.advanced(by: writerIndex &- ptr.count),
+        ptr.baseAddress!,
+        ptr.count)
       _writerSize = _writerSize &+ ptr.count
     }
   }
@@ -281,7 +282,7 @@ public struct ByteBuffer {
       ensureSpace(size: ptr.count)
       memcpy(
         _storage.memory.advanced(by: writerIndex &- ptr.count),
-        UnsafeRawPointer(ptr.baseAddress!),
+        ptr.baseAddress!,
         ptr.count)
       _writerSize = _writerSize &+ ptr.count
     }
@@ -296,11 +297,10 @@ public struct ByteBuffer {
   @inline(__always)
   mutating func push<T: NativeStruct>(struct value: T, size: Int) {
     ensureSpace(size: size)
-    var v = value
-    withUnsafeBytes(of: &v) {
+    withUnsafePointer(to: value) {
       memcpy(
         _storage.memory.advanced(by: writerIndex &- size),
-        $0.baseAddress!,
+        $0,
         size)
       _writerSize = _writerSize &+ size
     }
@@ -314,11 +314,10 @@ public struct ByteBuffer {
   @usableFromInline
   mutating func push<T: Scalar>(value: T, len: Int) {
     ensureSpace(size: len)
-    var v = value
-    withUnsafeBytes(of: &v) {
+    withUnsafePointer(to: value) {
       memcpy(
         _storage.memory.advanced(by: writerIndex &- len),
-        $0.baseAddress!,
+        $0,
         len)
       _writerSize = _writerSize &+ len
     }
@@ -355,7 +354,7 @@ public struct ByteBuffer {
   {
     memcpy(
       _storage.memory.advanced(by: writerIndex &- len),
-      UnsafeRawPointer(bytes.baseAddress!),
+      bytes.baseAddress!,
       len)
     _writerSize = _writerSize &+ len
     return true
@@ -377,7 +376,12 @@ public struct ByteBuffer {
     }
     assert(index < _storage.capacity, "Write index is out of writing bound")
     assert(index >= 0, "Writer index should be above zero")
-    _storage.memory.storeBytes(of: value, toByteOffset: index, as: T.self)
+    withUnsafePointer(to: value) {
+      memcpy(
+        _storage.memory.advanced(by: index),
+        $0,
+        MemoryLayout<T>.size)
+    }
   }
 
   /// Makes sure that buffer has enouch space for each of the objects that will be written into it

swift/Sources/FlatBuffers/FlatBufferBuilder.swift

@@ -146,12 +146,12 @@ public struct FlatBufferBuilder {
   /// by the generated code*
   @inline(__always)
   mutating public func require(table: Offset, fields: [Int32]) {
-    for field in fields {
+    for index in stride(from: 0, to: fields.count, by: 1) {
       let start = _bb.capacity &- Int(table.o)
       let startTable = start &- Int(_bb.read(def: Int32.self, position: start))
       let isOkay = _bb.read(
         def: VOffset.self,
-        position: startTable &+ Int(field)) != 0
+        position: startTable &+ Int(fields[index])) != 0
       assert(isOkay, "Flatbuffers requires the following field")
     }
   }
@@ -285,13 +285,13 @@ public struct FlatBufferBuilder {
     let vt2 = _bb.memory.advanced(by: _bb.writerIndex)
     let len2 = vt2.load(fromByteOffset: 0, as: Int16.self)
 
-    for table in _vtables {
-      let position = _bb.capacity &- Int(table)
+    for index in stride(from: 0, to: _vtables.count, by: 1) {
+      let position = _bb.capacity &- Int(_vtables[index])
       let vt1 = _bb.memory.advanced(by: position)
       let len1 = _bb.read(def: Int16.self, position: position)
       if len2 != len1 || 0 != memcmp(vt1, vt2, Int(len2)) { continue }
 
-      isAlreadyAdded = Int(table)
+      isAlreadyAdded = Int(_vtables[index])
       break
     }
 
@@ -380,7 +380,7 @@ public struct FlatBufferBuilder {
   @inline(__always)
   @usableFromInline
   mutating internal func track(offset: UOffset, at position: VOffset) {
-    _vtableStorage.add(loc: FieldLoc(offset: offset, position: position))
+    _vtableStorage.add(loc: (offset: offset, position: position))
   }
 
   // MARK: - Inserting Vectors
@@ -524,8 +524,8 @@ public struct FlatBufferBuilder {
   {
     let size = size
     startVector(size, elementSize: T.byteSize)
-    for e in elements.reversed() {
-      _bb.push(value: e.value, len: T.byteSize)
+    for index in stride(from: elements.count, to: 0, by: -1) {
+      _bb.push(value: elements[index &- 1].value, len: T.byteSize)
     }
     return endVector(len: size)
   }
@@ -569,8 +569,8 @@ public struct FlatBufferBuilder {
     len: Int) -> Offset
   {
     startVector(len, elementSize: MemoryLayout<Offset>.size)
-    for o in offsets.reversed() {
-      push(element: o)
+    for index in stride(from: offsets.count, to: 0, by: -1) {
+      push(element: offsets[index &- 1])
     }
     return endVector(len: len)
   }
@@ -593,8 +593,8 @@ public struct FlatBufferBuilder {
   @inline(__always)
   mutating public func createVector(ofStrings str: [String]) -> Offset {
     var offsets: [Offset] = []
-    for s in str {
-      offsets.append(create(string: s))
+    for index in stride(from: 0, to: str.count, by: 1) {
+      offsets.append(create(string: str[index]))
     }
     return createVector(ofOffsets: offsets)
   }
@@ -646,9 +646,8 @@ public struct FlatBufferBuilder {
     struct s: T, position: VOffset) -> Offset
   {
     let offset = create(struct: s)
-    _vtableStorage.add(loc: FieldLoc(
-      offset: _bb.size,
-      position: VOffset(position)))
+    _vtableStorage.add(
+      loc: (offset: _bb.size, position: VOffset(position)))
     return offset
   }
 
@@ -837,6 +836,8 @@ extension FlatBufferBuilder: CustomDebugStringConvertible {
     """
   }
 
+  typealias FieldLoc = (offset: UOffset, position: VOffset)
+
   /// VTableStorage is a class to contain the VTable buffer that would be serialized into buffer
   @usableFromInline
   internal class VTableStorage {
@@ -920,12 +921,5 @@ extension FlatBufferBuilder: CustomDebugStringConvertible {
     func load(at index: Int) -> FieldLoc {
       memory.load(fromByteOffset: index, as: FieldLoc.self)
     }
-
   }
-
-  internal struct FieldLoc {
-    var offset: UOffset
-    var position: VOffset
-  }
-
 }