1 import Foundation 2 3 public struct Table { 4 public private(set) var bb: ByteBuffer 5 public private(set) var postion: Int32 6 7 public init(bb: ByteBuffer, position: Int32 = 0) { 8 guard isLitteEndian else { 9 fatalError("Reading/Writing a buffer in big endian machine is not supported on swift") 10 } 11 self.bb = bb 12 self.postion = position 13 } 14 offsetnull15 public func offset(_ o: Int32) -> Int32 { 16 let vtable = postion - bb.read(def: Int32.self, position: Int(postion)) 17 return o < bb.read(def: VOffset.self, position: Int(vtable)) ? Int32(bb.read(def: Int16.self, position: Int(vtable + o))) : 0 18 } 19 indirectnull20 public func indirect(_ o: Int32) -> Int32 { return o + bb.read(def: Int32.self, position: Int(o)) } 21 22 /// String reads from the buffer with respect to position of the current table. 23 /// - Parameter offset: Offset of the string stringnull24 public func string(at offset: Int32) -> String? { 25 return directString(at: offset + postion) 26 } 27 28 /// Direct string reads from the buffer disregarding the position of the table. 29 /// It would be preferable to use string unless the current position of the table is not needed 30 /// - Parameter offset: Offset of the string directStringnull31 public func directString(at offset: Int32) -> String? { 32 var offset = offset 33 offset += bb.read(def: Int32.self, position: Int(offset)) 34 let count = bb.read(def: Int32.self, position: Int(offset)) 35 let position = offset + Int32(MemoryLayout<Int32>.size) 36 return bb.readString(at: position, count: count) 37 } 38 39 /// Reads from the buffer with respect to the position in the table. 40 /// - Parameters: 41 /// - type: Type of Scalar that needs to be read from the buffer 42 /// - o: Offset of the Element readBuffer<T: Scalar>null43 public func readBuffer<T: Scalar>(of type: T.Type, at o: Int32) -> T { 44 return directRead(of: T.self, offset: o + postion) 45 } 46 47 /// Reads from the buffer disregarding the position of the table. 48 /// It would be used when reading from an 49 /// ``` 50 /// let offset = __t.offset(10) 51 /// //Only used when the we already know what is the 52 /// // position in the table since __t.vector(at:) 53 /// // returns the index with respect to the position 54 /// __t.directRead(of: Byte.self, 55 /// offset: __t.vector(at: offset) + index * 1) 56 /// ``` 57 /// - Parameters: 58 /// - type: Type of Scalar that needs to be read from the buffer 59 /// - o: Offset of the Element directRead<T: Scalar>null60 public func directRead<T: Scalar>(of type: T.Type, offset o: Int32) -> T { 61 let r = bb.read(def: T.self, position: Int(o)) 62 return r 63 } 64 union<T: FlatBufferObject>null65 public func union<T: FlatBufferObject>(_ o: Int32) -> T { 66 let o = o + postion 67 return directUnion(o) 68 } 69 directUnion<T: FlatBufferObject>null70 public func directUnion<T: FlatBufferObject>(_ o: Int32) -> T { 71 return T.init(bb, o: o + bb.read(def: Int32.self, position: Int(o))) 72 } 73 getVector<T>null74 public func getVector<T>(at off: Int32) -> [T]? { 75 let o = offset(off) 76 guard o != 0 else { return nil } 77 return bb.readSlice(index: vector(at: o), count: vector(count: o)) 78 } 79 80 /// Vector count gets the count of Elements within the array 81 /// - Parameter o: start offset of the vector 82 /// - returns: Count of elements vectornull83 public func vector(count o: Int32) -> Int32 { 84 var o = o 85 o += postion 86 o += bb.read(def: Int32.self, position: Int(o)) 87 return bb.read(def: Int32.self, position: Int(o)) 88 } 89 90 /// Vector start index in the buffer 91 /// - Parameter o:start offset of the vector 92 /// - returns: the start index of the vector vectornull93 public func vector(at o: Int32) -> Int32 { 94 var o = o 95 o += postion 96 return o + bb.read(def: Int32.self, position: Int(o)) + 4 97 } 98 } 99 100 extension Table { 101 indirectnull102 static public func indirect(_ o: Int32, _ fbb: ByteBuffer) -> Int32 { return o + fbb.read(def: Int32.self, position: Int(o)) } 103 offsetnull104 static public func offset(_ o: Int32, vOffset: Int32, fbb: ByteBuffer) -> Int32 { 105 let vTable = Int32(fbb.capacity) - o 106 return vTable + Int32(fbb.read(def: Int16.self, position: Int(vTable + vOffset - fbb.read(def: Int32.self, position: Int(vTable))))) 107 } 108 comparenull109 static public func compare(_ off1: Int32, _ off2: Int32, fbb: ByteBuffer) -> Int32 { 110 let memorySize = Int32(MemoryLayout<Int32>.size) 111 let _off1 = off1 + fbb.read(def: Int32.self, position: Int(off1)) 112 let _off2 = off2 + fbb.read(def: Int32.self, position: Int(off2)) 113 let len1 = fbb.read(def: Int32.self, position: Int(_off1)) 114 let len2 = fbb.read(def: Int32.self, position: Int(_off2)) 115 let startPos1 = _off1 + memorySize 116 let startPos2 = _off2 + memorySize 117 let minValue = min(len1, len2) 118 for i in 0...minValue { 119 let b1 = fbb.read(def: Int8.self, position: Int(i + startPos1)) 120 let b2 = fbb.read(def: Int8.self, position: Int(i + startPos2)) 121 if b1 != b2 { 122 return Int32(b2 - b1) 123 } 124 } 125 return len1 - len2 126 } 127 comparenull128 static public func compare(_ off1: Int32, _ key: [Byte], fbb: ByteBuffer) -> Int32 { 129 let memorySize = Int32(MemoryLayout<Int32>.size) 130 let _off1 = off1 + fbb.read(def: Int32.self, position: Int(off1)) 131 let len1 = fbb.read(def: Int32.self, position: Int(_off1)) 132 let len2 = Int32(key.count) 133 let startPos1 = _off1 + memorySize 134 let minValue = min(len1, len2) 135 for i in 0..<minValue { 136 let b = fbb.read(def: Int8.self, position: Int(i + startPos1)) 137 let byte = key[Int(i)] 138 if b != byte { 139 return Int32(b - Int8(byte)) 140 } 141 } 142 return len1 - len2 143 } 144 } 145