use extract method in decoder

Author: tanner0101

Sources/PostgreSQL/Message+Parse/PostgreSQLMessageDecoder.swift

@@ -105,24 +105,7 @@ fileprivate final class _PostgreSQLMessageDecoder: Decoder, SingleValueDecodingC
 
     /// Decodes a fixed width integer.
     func decode<B>(fixedWidthInteger type: B.Type) throws -> B where B: FixedWidthInteger {
-        guard data.count >= MemoryLayout<B>.size else {
-            fatalError("Unexpected end of data while decoding \(B.self).")
-        }
-
-
-        let int: B = data.withUnsafeBytes { (pointer: UnsafePointer<UInt8>) -> B in
-            return pointer.withMemoryRebound(to: B.self, capacity: 1) { (pointer: UnsafePointer<B>) -> B in
-                return pointer.pointee.bigEndian
-            }
-        }
-
-        if data.count == MemoryLayout<B>.size {
-            /// FIXME: safely advance elsewhere as well
-            data = Data()
-        } else {
-            data = data.advanced(by: MemoryLayout<B>.size)
-        }
-        return int
+        return data.extract(B.self).bigEndian
     }
 
     /// See SingleValueDecodingContainer.decode

Sources/PostgreSQL/Utilities.swift

@@ -49,7 +49,7 @@ extension Data {
 
     /// Casts data to a supplied type.
     internal mutating func extract<T>(_ type: T.Type = T.self) -> T {
-        assert(MemoryLayout<T>.size <= count, "Insufficient data to decode: \(T.self)")
+        assert(MemoryLayout<T>.size <= count, "Insufficient data to exctract: \(T.self)")
         defer { skip(sizeOf: T.self) }
         return withUnsafeBytes { (pointer: UnsafePointer<T>) -> T in
             return pointer.pointee
@@ -66,5 +66,5 @@ extension Data {
         }
     }
 
-    
+
 }