//
//  BinaryReader.swift
//  TerrainFun
//
//  Created by Rick Mann on 2020-07-28.
//  Copyright © 2020 Latency: Zero, LLC. All rights reserved.
//

import Foundation




struct
BinaryReader
{
    init(data inData: Data)
    {
        self.data = inData
    }

    mutating
    func
    get<T>()
        -> T where T : FixedWidthInteger
    {
        let size = MemoryLayout<T>.size
        let v: T = self.data.subdata(in: self.idx..<self.idx + size).withUnsafeBytes { $0.load(as: T.self) }
        self.idx += size
        if self.bigEndian
        {
            return T(bigEndian: v)
        }
        else
        {
            return T(littleEndian: v)
        }
    }

    mutating
    func
    seek(by inDelta: Int)
    {
        self.idx += inDelta
        precondition(self.idx >= 0 && self.idx < self.data.count, "seek(by: \(inDelta)) out of bounds")
    }

    mutating
    func
    seek(to inOffset: Int)
    {
        precondition(inOffset >= 0 && inOffset < self.data.count, "seek(to: \(inOffset)) out of bounds")
        self.idx = inOffset
    }

    mutating
    func
    seek(to inOffset: UInt32)
    {
        seek(to: Int(inOffset))
    }

    let data            :   Data
    var idx                         =   0
    var bigEndian                   =   true
}