Hide wasm implementation behind a native array

Author: mustiikhalil

swift/Sources/FlexBuffers/Reader/Reference.swift

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+import Common
 import Foundation
 
 enum FlexBuffersErrors: Error {
@@ -23,6 +24,10 @@ enum FlexBuffersErrors: Error {
 
 @inline(__always)
 public func getRoot(buffer: ByteBuffer) throws -> Reference? {
+  assert(
+    isLitteEndian,
+    "Swift FlexBuffers currently only supports little-endian systems")
+
   let end = buffer.count
   if buffer.count < 3 {
     throw FlexBuffersErrors.sizeOfBufferIsTooSmall

swift/Sources/FlexBuffers/Writer/FlexBuffersWriter.swift

@@ -37,12 +37,19 @@ public struct FlexBuffersWriter {
   private var hasDuplicatedKeys = false
   private var minBitWidth: BitWidth = .w8
   private var _bb: _InternalByteBuffer
+  #if os(Wasm)
+  private var stack: [Value] = []
+  #else
   private var stack: Stack = Stack()
+  #endif
   private var keyPool: [Int: UInt] = [:]
   private var stringPool: [Int: UInt] = [:]
   private var flags: BuilderFlag
 
   public init(initialSize: Int = 1024, flags: BuilderFlag = .shareKeys) {
+    assert(
+      isLitteEndian,
+      "Swift FlexBuffers currently only supports little-endian systems")
     _bb = _InternalByteBuffer(initialSize: initialSize)
     self.flags = flags
   }
@@ -899,6 +906,22 @@ extension FlexBuffersWriter {
   }
 }
 
+extension Array where Element == Value {
+  mutating func popLast(_ val: Int) {
+    self = Array(self[..<val])
+  }
+
+  @discardableResult
+  mutating func withUnsafeMutableBytes<R>(
+    start: Int,
+    _ body: (UnsafeMutableRawBufferPointer) throws -> R) rethrows -> R
+  {
+    try self[start...].withUnsafeMutableBytes { buffer in
+      try body(buffer)
+    }
+  }
+}
+
 fileprivate struct Stack: RandomAccessCollection {
   typealias Element = Value
   typealias Index = Int