/// <summary>
/// Encodes the specified data.
/// </summary>
public byte[] Encode(byte[] data, PdfFlateEncodeMode mode)
{
MemoryStream ms = new MemoryStream();
// DeflateStream/GZipStream does not work immediately and I have not the leisure to work it out.
// So I keep on using SharpZipLib even with .NET 2.0.
int level = Deflater.DEFAULT_COMPRESSION;
switch (mode)
{
case PdfFlateEncodeMode.BestCompression:
level = Deflater.BEST_COMPRESSION;
break;
case PdfFlateEncodeMode.BestSpeed:
level = Deflater.BEST_SPEED;
break;
}
DeflaterOutputStream zip = new DeflaterOutputStream(ms, new Deflater(level, false));
zip.Write(data, 0, data.Length);
zip.Finish();
return(ms.ToArray());
}
/// <summary>
/// Encodes the specified data.
/// </summary>
public byte[] Encode(byte[] data, PdfFlateEncodeMode mode)
{
MemoryStream ms = new MemoryStream();
// DeflateStream/GZipStream does not work immediately and I have not the leisure to work it out.
// So I keep on using SharpZipLib even with .NET 2.0.
#if NET_ZIP
// See http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=97064
//
// Excerpt from the RFC 1950 specs for first byte:
//
// CMF (Compression Method and flags)
// This byte is divided into a 4-bit compression method and a 4-
// bit information field depending on the compression method.
//
// bits 0 to 3 CM Compression method
// bits 4 to 7 CINFO Compression info
//
// CM (Compression method)
// This identifies the compression method used in the file. CM = 8
// denotes the "deflate" compression method with a window size up
// to 32K. This is the method used by gzip and PNG (see
// references [1] and [2] in Chapter 3, below, for the reference
// documents). CM = 15 is reserved. It might be used in a future
// version of this specification to indicate the presence of an
// extra field before the compressed data.
//
// CINFO (Compression info)
// For CM = 8, CINFO is the base-2 logarithm of the LZ77 window
// size, minus eight (CINFO=7 indicates a 32K window size). Values
// of CINFO above 7 are not allowed in this version of the
// specification. CINFO is not defined in this specification for
// CM not equal to 8.
ms.WriteByte(0x78);
// Excerpt from the RFC 1950 specs for second byte:
//
// FLG (FLaGs)
// This flag byte is divided as follows:
//
// bits 0 to 4 FCHECK (check bits for CMF and FLG)
// bit 5 FDICT (preset dictionary)
// bits 6 to 7 FLEVEL (compression level)
//
// The FCHECK value must be such that CMF and FLG, when viewed as
// a 16-bit unsigned integer stored in MSB order (CMF*256 + FLG),
// is a multiple of 31.
//
// FDICT (Preset dictionary)
// If FDICT is set, a DICT dictionary identifier is present
// immediately after the FLG byte. The dictionary is a sequence of
// bytes which are initially fed to the compressor without
// producing any compressed output. DICT is the Adler-32 checksum
// of this sequence of bytes (see the definition of ADLER32
// below). The decompressor can use this identifier to determine
// which dictionary has been used by the compressor.
//
// FLEVEL (Compression level)
// These flags are available for use by specific compression
// methods. The "deflate" method (CM = 8) sets these flags as
// follows:
//
// 0 - compressor used fastest algorithm
// 1 - compressor used fast algorithm
// 2 - compressor used default algorithm
// 3 - compressor used maximum compression, slowest algorithm
//
// The information in FLEVEL is not needed for decompression; it
// is there to indicate if recompression might be worthwhile.
ms.WriteByte(0x01);
DeflateStream zip = new DeflateStream(ms, CompressionMode.Compress, true);
zip.Write(data, 0, data.Length);
zip.Close();
var checksum = CalcChecksum(data);
ms.WriteByte((byte)checksum);
ms.WriteByte((byte)(checksum >> 8));
ms.WriteByte((byte)(checksum >> 16));
ms.WriteByte((byte)(checksum >> 24));
#else
int level = Deflater.DEFAULT_COMPRESSION;
switch (mode)
{
case PdfFlateEncodeMode.BestCompression:
level = Deflater.BEST_COMPRESSION;
break;
case PdfFlateEncodeMode.BestSpeed:
level = Deflater.BEST_SPEED;
break;
}
DeflaterOutputStream zip = new DeflaterOutputStream(ms, new Deflater(level, false));
zip.Write(data, 0, data.Length);
zip.Finish();
#endif
#if !NETFX_CORE && !UWP
ms.Capacity = (int)ms.Length;
return(ms.GetBuffer());
#else
return(ms.ToArray());
#endif
}
/// <summary>
/// Encodes the specified data.
/// </summary>
public byte[] Encode(byte[] data, PdfFlateEncodeMode mode)
{
MemoryStream ms = new MemoryStream();
// DeflateStream/GZipStream does not work immediately and I have not the leisure to work it out.
// So I keep on using SharpZipLib even with .NET 2.0.
#if NET_ZIP
// See http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=97064
//
// Excerpt from the RFC 1950 specs for first byte:
//
// CMF (Compression Method and flags)
// This byte is divided into a 4-bit compression method and a 4-
// bit information field depending on the compression method.
//
// bits 0 to 3 CM Compression method
// bits 4 to 7 CINFO Compression info
//
// CM (Compression method)
// This identifies the compression method used in the file. CM = 8
// denotes the "deflate" compression method with a window size up
// to 32K. This is the method used by gzip and PNG (see
// references [1] and [2] in Chapter 3, below, for the reference
// documents). CM = 15 is reserved. It might be used in a future
// version of this specification to indicate the presence of an
// extra field before the compressed data.
//
// CINFO (Compression info)
// For CM = 8, CINFO is the base-2 logarithm of the LZ77 window
// size, minus eight (CINFO=7 indicates a 32K window size). Values
// of CINFO above 7 are not allowed in this version of the
// specification. CINFO is not defined in this specification for
// CM not equal to 8.
ms.WriteByte(0x78);
// Excerpt from the RFC 1950 specs for second byte:
//
// FLG (FLaGs)
// This flag byte is divided as follows:
//
// bits 0 to 4 FCHECK (check bits for CMF and FLG)
// bit 5 FDICT (preset dictionary)
// bits 6 to 7 FLEVEL (compression level)
//
// The FCHECK value must be such that CMF and FLG, when viewed as
// a 16-bit unsigned integer stored in MSB order (CMF*256 + FLG),
// is a multiple of 31.
//
// FDICT (Preset dictionary)
// If FDICT is set, a DICT dictionary identifier is present
// immediately after the FLG byte. The dictionary is a sequence of
// bytes which are initially fed to the compressor without
// producing any compressed output. DICT is the Adler-32 checksum
// of this sequence of bytes (see the definition of ADLER32
// below). The decompressor can use this identifier to determine
// which dictionary has been used by the compressor.
//
// FLEVEL (Compression level)
// These flags are available for use by specific compression
// methods. The "deflate" method (CM = 8) sets these flags as
// follows:
//
// 0 - compressor used fastest algorithm
// 1 - compressor used fast algorithm
// 2 - compressor used default algorithm
// 3 - compressor used maximum compression, slowest algorithm
//
// The information in FLEVEL is not needed for decompression; it
// is there to indicate if recompression might be worthwhile.
ms.WriteByte(0x49);
DeflateStream zip = new DeflateStream(ms, CompressionMode.Compress, true);
zip.Write(data, 0, data.Length);
zip.Close();
#else
int level = Deflater.DEFAULT_COMPRESSION;
switch (mode)
{
case PdfFlateEncodeMode.BestCompression:
level = Deflater.BEST_COMPRESSION;
break;
case PdfFlateEncodeMode.BestSpeed:
level = Deflater.BEST_SPEED;
break;
}
DeflaterOutputStream zip = new DeflaterOutputStream(ms, new Deflater(level, false));
zip.Write(data, 0, data.Length);
zip.Finish();
#endif
#if !NETFX_CORE && !UWP
ms.Capacity = (int)ms.Length;
return ms.GetBuffer();
#else
return ms.ToArray();
#endif
}