ExifReader.cs

using System;
using System.Text;
 
namespace Waher.Content.Images.Exif
{
    public class ExifReader
    {
        private readonly byte[] data;
        private readonly int len;
        private int pos;
        private bool bigEndian = true;
 
        public int Position
        {
            get => this.pos;
            set
            {
                if (value < 0 || value >= this.len)
                    throw new ArgumentOutOfRangeException(nameof(Position), "Position out of range.");
 
                this.pos = value;
            }
        }
 
        public bool BigEndian
        {
            get => this.bigEndian;
            set => this.bigEndian = value;
        }
 
        public int Length => this.len;
 
        public bool EoF => this.pos >= this.len;
 
        public ExifReader(byte[] Data)
        {
            this.data = Data;
            this.len = Data.Length;
            this.pos = 0;
        }
 
        public int NextByte()
        {
            if (this.pos < this.len)
                return this.data[this.pos++];
            else
                return -1;
        }
 
        public int NextSHORT()
        {
            int i = this.NextByte();
            if (i < 0)
                return -1;
 
            int j = this.NextByte();
            if (j < 0)
                return -1;
 
            if (this.bigEndian)
            {
                i <<= 8;
                i |= j;
 
                return i;
            }
            else
            {
                j <<= 8;
                j |= i;
 
                return j;
            }
        }
 
        public uint? NextLONG()
        {
            int i = this.NextSHORT();
            if (i < 0)
                return null;
 
            int j = this.NextSHORT();
            if (j < 0)
                return null;
 
            if (this.bigEndian)
            {
                i <<= 16;
                i |= (ushort)j;
 
                return (uint)i;
            }
            else
            {
                j <<= 16;
                j |= (ushort)i;
 
                return (uint)j;
            }
        }
 
        public string NextASCIIString()
        {
            int Start = this.pos;
            while (this.pos < this.len && this.data[this.pos] != 0)
                this.pos++;
 
            string Result = Encoding.ASCII.GetString(this.data, Start, this.pos - Start);
            this.pos++;
 
            return Result;
        }
    }
}