Encoding GetOutputEncoding(EncodingInformation sourceEncodingInformation)
{
var outputEncoding = OutputEncoding;
if (null != outputEncoding)
{
return(outputEncoding);
}
switch (OutputBomPolicy)
{
case BomPolicy.Never:
return(Utf8WithoutBom);
case BomPolicy.CopySource:
return(sourceEncodingInformation.BomDetected ? Utf8WithBom : Utf8WithoutBom);
case BomPolicy.CopyUtf8OrForce:
if (sourceEncodingInformation.Encoding.CodePage == Encoding.UTF8.CodePage && !sourceEncodingInformation.BomDetected)
{
return(Utf8WithoutBom);
}
break;
case BomPolicy.Force:
default:
break;
}
return(Utf8WithBom);
}
Encoding GetOutputEncoding(EncodingInformation sourceEncodingInformation)
{
var outputEncoding = OutputEncoding;
if (null != outputEncoding)
return outputEncoding;
switch (OutputBomPolicy)
{
case BomPolicy.Never:
return Utf8WithoutBom;
case BomPolicy.CopySource:
return sourceEncodingInformation.BomDetected ? Utf8WithBom : Utf8WithoutBom;
case BomPolicy.CopyUtf8OrForce:
if (sourceEncodingInformation.Encoding.CodePage == Encoding.UTF8.CodePage && !sourceEncodingInformation.BomDetected)
return Utf8WithoutBom;
break;
case BomPolicy.Force:
default:
break;
}
return Utf8WithBom;
}
public async Task <bool> TransformFileAsync(Stream inputStream, Stream outputStream)
{
var encoding = await EncodingInformation.DetectEncodingAsync(inputStream).ConfigureAwait(false);
if (null == encoding)
{
throw new Exception("Unknown encoding");
}
inputStream.Seek(0, SeekOrigin.Begin);
using (var inputHash = SHA256.Create())
{
using (var outputHash = SHA256.Create())
{
using (var inputFilter = new CryptoStream(inputStream, inputHash, CryptoStreamMode.Read))
{
using (var outputFilter = new CryptoStream(outputStream, outputHash, CryptoStreamMode.Write))
{
using (var tr = new StreamReader(inputFilter, encoding.Encoding))
{
var outputEncoding = GetOutputEncoding(encoding);
using (var sw = new StreamWriter(outputFilter, outputEncoding, 4096, true))
{
await TransformCoreAsync(tr, sw).ConfigureAwait(false);
}
}
}
}
// Only return "true" if the files are the same (at least, they have the same SHA-256).
return(!inputHash.Hash.SequenceEqual(outputHash.Hash));
}
}
}
