private static string GetPartHeaderLine(YencHeader header)
{
long begin = header.PartOffset + 1;
long end = header.PartOffset + header.PartSize;
return($"{YencKeywords.YPart} {YencKeywords.Begin}={begin} {YencKeywords.End}={end}");
}
private static void ValidatePart(YencArticle article, ICollection <ValidationFailure> failures)
{
YencHeader header = article.Header;
YencFooter footer = article.Footer;
if (header.PartNumber != footer.PartNumber)
{
failures.Add(new ValidationFailure(
YencValidationErrorCodes.PartMismatch, Resources.Yenc.PartMismatch,
new { HeaderPart = header.PartNumber, FooterPart = footer.PartNumber }));
}
if (!(footer.PartSize == article.Data.Length && footer.PartSize == header.PartSize))
{
failures.Add(new ValidationFailure(
YencValidationErrorCodes.SizeMismatch, Resources.Yenc.PartSizeMismatch,
new { DataSize = article.Data.Length, HeaderSize = header.PartSize, FooterSize = footer.PartSize }));
}
if (!footer.PartCrc32.HasValue)
{
failures.Add(new ValidationFailure(
YencValidationErrorCodes.MissingChecksum, Resources.Yenc.MissingPartChecksum));
return;
}
uint calculatedCrc32 = Crc32.CalculateChecksum(article.Data);
if (calculatedCrc32 != footer.PartCrc32.Value)
{
failures.Add(new ValidationFailure(
YencValidationErrorCodes.ChecksumMismatch, Resources.Yenc.PartChecksumMismatch,
new { CalculatedChecksum = calculatedCrc32, FooterChecksum = footer.PartCrc32 }));
}
}
private static string GetHeaderLine(YencHeader header)
{
var builder = new StringBuilder(YencKeywords.YBegin);
if (header.IsFilePart)
{
builder.Append(' ').Append(YencKeywords.Part).Append('=').Append(header.PartNumber);
builder.Append(' ').Append(YencKeywords.Total).Append('=').Append(header.TotalParts);
}
builder.Append(' ').Append(YencKeywords.Line).Append('=').Append(header.LineLength);
builder.Append(' ').Append(YencKeywords.Size).Append('=').Append(header.FileSize);
builder.Append(' ').Append(YencKeywords.Name).Append('=').Append(header.FileName);
return(builder.ToString());
}
/// <summary>
/// Decodes yEnc-encoded text into a <see cref="YencArticle"/>
/// using the specified charcter encoding.
/// </summary>
/// <param name="encodedLines">The yEnc-encoded lines to decode.</param>
/// <param name="encoding">The charcter encoding to use.</param>
/// <returns>A <see cref="YencArticle"/> containing the decoded binary data and meta-data.</returns>
public static YencArticle Decode(IEnumerable <string> encodedLines, Encoding encoding)
{
Guard.ThrowIfNull(encodedLines, nameof(encodedLines));
Guard.ThrowIfNull(encoding, nameof(encoding));
using (IEnumerator <string> enumerator = encodedLines.GetEnumerator())
{
IDictionary <string, string> headers = YencMeta.GetHeaders(enumerator);
int part = headers.GetAndConvert(YencKeywords.Part, int.Parse);
if (part > 0)
{
headers.Merge(YencMeta.GetPartHeaders(enumerator), false);
}
YencHeader header = YencMeta.ParseHeader(headers);
YencFooter footer = null;
// create buffer for part or entire file if single part
var decodedBytes = new byte[header.PartSize];
var decodedBytesIndex = 0;
while (enumerator.MoveNext())
{
if (enumerator.Current == null)
{
continue;
}
if (enumerator.Current.StartsWith(yEnd))
{
footer = YencMeta.ParseFooter(YencMeta.ParseLine(enumerator.Current));
// skip remainder if there is some
while (enumerator.MoveNext())
{
}
break;
}
byte[] encodedBytes = encoding.GetBytes(enumerator.Current);
decodedBytesIndex += YencLineDecoder.Decode(encodedBytes, decodedBytes, decodedBytesIndex);
}
return(new YencArticle(header, footer, decodedBytes));
}
}
private static string GetFooterLine(YencHeader header, uint checksum)
{
var builder = new StringBuilder(YencKeywords.YEnd);
if (header.IsFilePart)
{
builder.Append(' ').Append(YencKeywords.Size).Append('=').Append(header.PartSize);
builder.Append(' ').Append(YencKeywords.Part).Append('=').Append(header.PartNumber);
builder.Append(' ').Append(YencKeywords.PartCrc32).Append('=').AppendFormat("{0:x}", checksum);
}
else
{
builder.Append(' ').Append(YencKeywords.Size).Append('=').Append(header.FileSize);
builder.Append(' ').Append(YencKeywords.Crc32).Append('=').AppendFormat("{0:x}", checksum);
}
return(builder.ToString());
}
/// <summary>
/// Validates the specified <see cref="YencArticle"/>.
/// </summary>
/// <param name="article">The yEnc-encoded article to validate.</param>
/// <returns>A <see cref="ValidationResult"/> containing a list of 0 or more validation failures.</returns>
public static ValidationResult Validate(YencArticle article)
{
var failures = new List <ValidationFailure>();
YencHeader header = article.Header;
YencFooter footer = article.Footer;
if (footer == null)
{
// nothing to validate
return(new ValidationResult(failures));
}
if (header.PartNumber > 0)
{
ValidatePart(article, failures);
return(new ValidationResult(failures));
}
if (footer.PartSize != article.Data.Length)
{
failures.Add(new ValidationFailure(
YencValidationErrorCodes.SizeMismatch, Resources.Yenc.SizeMismatch,
new { DataSize = article.Data.Length, FooterSize = footer.PartSize }));
}
if (!footer.Crc32.HasValue)
{
failures.Add(new ValidationFailure(
YencValidationErrorCodes.MissingChecksum, Resources.Yenc.MissingChecksum));
return(new ValidationResult(failures));
}
uint calculatedCrc32 = Crc32.CalculateChecksum(article.Data);
if (calculatedCrc32 != footer.Crc32.Value)
{
failures.Add(new ValidationFailure(
YencValidationErrorCodes.ChecksumMismatch, Resources.Yenc.ChecksumMismatch,
new { CalculatedChecksum = calculatedCrc32, FooterChecksum = footer.Crc32.Value }));
}
return(new ValidationResult(failures));
}
/// <summary>
/// Creates a new instance of the <see cref="YencArticle"/> class.
/// </summary>
/// <param name="header">The header of the Yenc-encoded article.</param>
/// <param name="footer">The optional footer of the Yenc-encoded article.</param>
/// <param name="data">The binary data obtained by decoding the Yenc-decoded article.</param>
public YencArticle(YencHeader header, YencFooter footer, byte[] data)
{
Header = header.ThrowIfNull(nameof(header));
Footer = footer;
Data = data.ThrowIfNull(nameof(data));
}
/// <summary>
/// Creates a new instance of the <see cref="YencStream"/> class.
/// </summary>
/// <param name="header">The header of the Yenc-encoded article.</param>
/// <param name="input">An enumeration of byte chunks from the decoded Yenc-encoded article.</param>
public YencStream(YencHeader header, IEnumerable <byte[]> input) : base(input)
{
Guard.ThrowIfNull(header, nameof(header));
Guard.ThrowIfNull(input, nameof(input));
Header = header;
}
/// <summary>
/// Encodes the binary data in the specified stream into yEnc-encoded text
/// using the specified character encoding.
/// </summary>
/// <param name="header">The yEnc header.</param>
/// <param name="stream">The stream containing the binary data to encode.</param>
/// <param name="encoding">The character encoding to use.</param>
/// <returns>The yEnc-encoded text.</returns>
public static IEnumerable <string> Encode(YencHeader header, Stream stream, Encoding encoding)
{
yield return(GetHeaderLine(header));
if (header.IsFilePart)
{
yield return(GetPartHeaderLine(header));
}
var encodedBytes = new byte[1024];
var encodedOffset = 0;
int lastCol = header.LineLength - 1;
uint checksum = Crc32.Initialize();
for (var offset = 0; offset < header.PartSize; offset++)
{
int @byte = stream.ReadByte();
if (@byte == -1)
{
// end of stream
break;
}
checksum = Crc32.Calculate(checksum, @byte);
int val = (@byte + 42) % 256;
// encode dot only in first column
bool encodeDot = encodedOffset == 0;
// encode white space only in first and last column
bool encodeWhitespace = encodedOffset == 0 || encodedOffset == lastCol;
// encode critical characters
if (val == YencCharacters.Null ||
val == YencCharacters.Lf ||
val == YencCharacters.Cr ||
val == YencCharacters.Equal ||
val == YencCharacters.Dot && encodeDot ||
val == YencCharacters.Space && encodeWhitespace ||
val == YencCharacters.Tab && encodeWhitespace)
{
encodedBytes[encodedOffset++] = YencCharacters.Equal;
val = (val + 64) % 256;
}
encodedBytes[encodedOffset++] = (byte)val;
if (encodedOffset < header.LineLength)
{
continue;
}
// return encoded line
yield return(encoding.GetString(encodedBytes, 0, encodedOffset));
// reset offset
encodedOffset = 0;
}
if (encodedOffset > 0)
{
// return remainder
yield return(encoding.GetString(encodedBytes, 0, encodedOffset));
}
checksum = Crc32.Finalize(checksum);
yield return(GetFooterLine(header, checksum));
}
/// <summary> /// Encodes the binary data in the specified stream into yEnc-encoded text /// using the default Usenet character encoding. /// </summary> /// <param name="header">The yEnc header.</param> /// <param name="stream">The stream containing the binary data to encode.</param> /// <returns>The yEnc-encoded text.</returns> public static IEnumerable <string> Encode(YencHeader header, Stream stream) => Encode(header, stream, UsenetEncoding.Default);
