LoadFile.cs

using System;
using System.IO;
using System.Threading.Tasks;
using Waher.Content;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
 
namespace Waher.Script.Content.Functions.InputOutput
{
    public class LoadFile : FunctionMultiVariate
    {
        public LoadFile(ScriptNode FileName, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { FileName }, argumentTypes1Scalar, Start, Length, Expression)
        {
        }
 
        public LoadFile(ScriptNode FileName, ScriptNode ContentType, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { FileName, ContentType }, argumentTypes2Scalar, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(LoadFile);
 
        public override string[] DefaultArgumentNames => new string[] { "FileName", "ContentType" };
 
        public override bool IsAsynchronous => true;
 
        public override IElement Evaluate(IElement[] Arguments, Variables Variables)
        {
            return this.EvaluateAsync(Arguments, Variables).Result;
        }
 
        public override async Task<IElement> EvaluateAsync(IElement[] Arguments, Variables Variables)
        {
            string FileName = Arguments[0].AssociatedObjectValue?.ToString();
            string ContentType;
 
            FileName = Path.Combine(Directory.GetCurrentDirectory(), FileName);
 
            if (Arguments.Length > 1)
                ContentType = Arguments[1].AssociatedObjectValue?.ToString();
            else
                ContentType = InternetContent.GetContentType(Path.GetExtension(FileName));
 
            byte[] Bin;
 
            try
            {
                using (FileStream fs = File.OpenRead(FileName))
                {
                    Bin = await this.LoadBin(fs);
                }
            }
            catch (IOException)
            {
                string TempFileName = Path.GetTempFileName();
                File.Copy(FileName, TempFileName, true);
 
                try
                {
                    using (FileStream fs = File.OpenRead(TempFileName))
                    {
                        Bin = await this.LoadBin(fs);
                    }
                }
                finally
                {
                    File.Delete(TempFileName);
                }
            }
 
            object Decoded = await InternetContent.DecodeAsync(ContentType, Bin, new Uri(FileName));
 
            return Expression.Encapsulate(Decoded);
        }
 
        private async Task<byte[]> LoadBin(FileStream fs)
        {
            long l = fs.Length;
            if (l > int.MaxValue)
                throw new ScriptRuntimeException("File too large.", this);
 
            int Len = (int)l;
            byte[] Bin = new byte[Len];
            int Pos = 0;
 
            while (Pos < Len)
            {
                int i = await fs.ReadAsync(Bin, Pos, Len - Pos);
                if (i < 0)
                    throw new ScriptRuntimeException("Unexpected end of file.", this);
 
                Pos += i;
            }
 
            return Bin;
        }
    }
}