add flatbuffers

commit 6da1cf79d90eb242e7da5318241d42279a3df3ba
Author: Max Burke <max@urbanlogiq.com>
Date:   Sun Jan 19 14:47:28 2020 -0800

    [rust] Add use declarations to Rust-generated bindings for imported FB definitions (#5645)

    * Bugfix for Rust generation of union fields named with language keywords

flatbuffers/swift/Sources/FlatBuffers/Table.swift

@@ -0,0 +1,144 @@
+import Foundation
+
+public struct Table {
+    public private(set) var bb: ByteBuffer
+    public private(set) var postion: Int32
+    
+    public init(bb: ByteBuffer, position: Int32 = 0) {
+        guard isLitteEndian else {
+            fatalError("Reading/Writing a buffer in big endian machine is not supported on swift")
+        }
+        self.bb = bb
+        self.postion = position
+    }
+    
+    public func offset(_ o: Int32) -> Int32 {
+        let vtable = postion - bb.read(def: Int32.self, position: Int(postion))
+        return o < bb.read(def: VOffset.self, position: Int(vtable)) ? Int32(bb.read(def: Int16.self, position: Int(vtable + o))) : 0
+    }
+    
+    public func indirect(_ o: Int32) -> Int32 { return o + bb.read(def: Int32.self, position: Int(o)) }
+
+    /// String reads from the buffer with respect to position of the current table.
+    /// - Parameter offset: Offset of the string
+    public func string(at offset: Int32) -> String? {
+        return directString(at: offset + postion)
+    }
+    
+    /// Direct string reads from the buffer disregarding the position of the table.
+    /// It would be preferable to use string unless the current position of the table is not needed
+    /// - Parameter offset: Offset of the string
+    public func directString(at offset: Int32) -> String? {
+         var offset = offset
+         offset += bb.read(def: Int32.self, position: Int(offset))
+         let count = bb.read(def: Int32.self, position: Int(offset))
+         let position = offset + Int32(MemoryLayout<Int32>.size)
+         return bb.readString(at: position, count: count)
+    }
+    
+    /// Reads from the buffer with respect to the position in the table.
+    /// - Parameters:
+    ///   - type: Type of Scalar that needs to be read from the buffer
+    ///   - o: Offset of the Element
+    public func readBuffer<T: Scalar>(of type: T.Type, at o: Int32) -> T {
+        return directRead(of: T.self, offset: o + postion)
+    }
+    
+    /// Reads from the buffer disregarding the position of the table.
+    /// It would be used when reading from an
+    ///   ```
+    ///   let offset = __t.offset(10)
+    ///   //Only used when the we already know what is the
+    ///   // position in the table since __t.vector(at:)
+    ///   // returns the index with respect to the position
+    ///   __t.directRead(of: Byte.self,
+    ///                  offset: __t.vector(at: offset) + index * 1)
+    ///   ```
+    /// - Parameters:
+    ///   - type: Type of Scalar that needs to be read from the buffer
+    ///   - o: Offset of the Element
+    public func directRead<T: Scalar>(of type: T.Type, offset o: Int32) -> T {
+        let r = bb.read(def: T.self, position: Int(o))
+        return r
+    }
+    
+    public func union<T: FlatBufferObject>(_ o: Int32) -> T {
+        let o = o + postion
+        return directUnion(o)
+    }
+
+    public func directUnion<T: FlatBufferObject>(_ o: Int32) -> T {
+        return T.init(bb, o: o + bb.read(def: Int32.self, position: Int(o)))
+    }
+    
+    public func getVector<T>(at off: Int32) -> [T]? {
+        let o = offset(off)
+        guard o != 0 else { return nil }
+        return bb.readSlice(index: vector(at: o), count: vector(count: o))
+    }
+    
+    /// Vector count gets the count of Elements within the array
+    /// - Parameter o: start offset of the vector
+    /// - returns: Count of elements
+    public func vector(count o: Int32) -> Int32 {
+        var o = o
+        o += postion
+        o += bb.read(def: Int32.self, position: Int(o))
+        return bb.read(def: Int32.self, position: Int(o))
+    }
+    
+    /// Vector start index in the buffer
+    /// - Parameter o:start offset of the vector
+    /// - returns: the start index of the vector
+    public func vector(at o: Int32) -> Int32 {
+        var o = o
+        o += postion
+        return o + bb.read(def: Int32.self, position: Int(o)) + 4
+    }
+}
+
+extension Table {
+    
+    static public func indirect(_ o: Int32, _ fbb: ByteBuffer) -> Int32 { return o + fbb.read(def: Int32.self, position: Int(o)) }
+    
+    static public func offset(_ o: Int32, vOffset: Int32, fbb: ByteBuffer) -> Int32 {
+        let vTable = Int32(fbb.capacity) - o
+        return vTable + Int32(fbb.read(def: Int16.self, position: Int(vTable + vOffset - fbb.read(def: Int32.self, position: Int(vTable)))))
+    }
+    
+    static public func compare(_ off1: Int32, _ off2: Int32, fbb: ByteBuffer) -> Int32 {
+        let memorySize = Int32(MemoryLayout<Int32>.size)
+        let _off1 = off1 + fbb.read(def: Int32.self, position: Int(off1))
+        let _off2 = off2 + fbb.read(def: Int32.self, position: Int(off2))
+        let len1 = fbb.read(def: Int32.self, position: Int(_off1))
+        let len2 = fbb.read(def: Int32.self, position: Int(_off2))
+        let startPos1 = _off1 + memorySize
+        let startPos2 = _off2 + memorySize
+        let minValue = min(len1, len2)
+        for i in 0...minValue {
+            let b1 = fbb.read(def: Int8.self, position: Int(i + startPos1))
+            let b2 = fbb.read(def: Int8.self, position: Int(i + startPos2))
+            if b1 != b2 {
+                return Int32(b2 - b1)
+            }
+        }
+        return len1 - len2
+    }
+    
+    static public func compare(_ off1: Int32, _ key: [Byte], fbb: ByteBuffer) -> Int32 {
+        let memorySize = Int32(MemoryLayout<Int32>.size)
+        let _off1 = off1 + fbb.read(def: Int32.self, position: Int(off1))
+        let len1 = fbb.read(def: Int32.self, position: Int(_off1))
+        let len2 = Int32(key.count)
+        let startPos1 = _off1 + memorySize
+        let minValue = min(len1, len2)
+        for i in 0..<minValue {
+            let b = fbb.read(def: Int8.self, position: Int(i + startPos1))
+            let byte = key[Int(i)]
+            if b != byte {
+                return Int32(b - Int8(byte))
+            }
+        }
+        return len1 - len2
+    }
+}