SkDeflateWStream Class Reference

#include <SkDeflate.h>

Inheritance diagram for SkDeflateWStream:

Classes
struct	Impl

Public Member Functions
	SkDeflateWStream (SkWStream *, int compressionLevel, bool gzip=false)
	~SkDeflateWStream () override
void	finalize ()
bool	write (const void *, size_t) override
size_t	bytesWritten () const override
Public Member Functions inherited from SkWStream
virtual	~SkWStream ()
	SkWStream ()
virtual void	flush ()
bool	write8 (U8CPU value)
bool	write16 (U16CPU value)
bool	write32 (uint32_t v)
bool	writeText (const char text[])
bool	newline ()
bool	writeDecAsText (int32_t)
bool	writeBigDecAsText (int64_t, int minDigits=0)
bool	writeHexAsText (uint32_t, int minDigits=0)
bool	writeScalarAsText (SkScalar)
bool	writeBool (bool v)
bool	writeScalar (SkScalar)
bool	writePackedUInt (size_t)
bool	writeStream (SkStream *input, size_t length)

Additional Inherited Members
Static Public Member Functions inherited from SkWStream
static int	SizeOfPackedUInt (size_t value)

Detailed Description

Wrap a stream in this class to compress the information written to this stream using the Deflate algorithm.

See http://en.wikipedia.org/wiki/DEFLATE

Definition at line 20 of file SkDeflate.h.

Constructor & Destructor Documentation

SkDeflateWStream()

SkDeflateWStream::SkDeflateWStream	(	SkWStream *	out,
		int	compressionLevel,
		bool	gzip = false
	)

Does not take ownership of the stream.

Parameters

compressionLevel	1 is best speed; 9 is best compression. The default, -1, is to use zlib's Z_DEFAULT_COMPRESSION level. 0 would be no compression, but due to broken zlibs, users should handle that themselves.
gzip	iff true, output a gzip file. "The gzip format is a wrapper, documented in RFC 1952, around a deflate stream." gzip adds a header with a magic number to the beginning of the stream, allowing a client to identify a gzip file.

Definition at line 67 of file SkDeflate.cpp.

    : fImpl(std::make_unique<SkDeflateWStream::Impl>()) {
 
    // There has existed at some point at least one zlib implementation which thought it was being
    // clever by randomizing the compression level. This is actually not entirely incorrect, except
    // for the no-compression level which should always be deterministically pass-through.
    // Users should instead consider the zero compression level broken and handle it themselves.
    SkASSERT(compressionLevel != 0);
 
    fImpl->fOut = out;
    fImpl->fInBufferIndex = 0;
    if (!fImpl->fOut) {
        return;
    }
    fImpl->fZStream.next_in = nullptr;
    fImpl->fZStream.zalloc = &skia_alloc_func;
    fImpl->fZStream.zfree = &skia_free_func;
    fImpl->fZStream.opaque = nullptr;
    SkASSERT(compressionLevel <= 9 && compressionLevel >= -1);
    SkDEBUGCODE(int r =) deflateInit2(&fImpl->fZStream, compressionLevel,
                                      Z_DEFLATED, gzip ? 0x1F : 0x0F,
                                      8, Z_DEFAULT_STRATEGY);
    SkASSERT(Z_OK == r);
}

~SkDeflateWStream()

SkDeflateWStream::~SkDeflateWStream ( )

override

The destructor calls finalize().

Definition at line 94 of file SkDeflate.cpp.

{ this->finalize(); }

Member Function Documentation

bytesWritten()

size_t SkDeflateWStream::bytesWritten ( ) const

overridevirtual

Implements SkWStream.

Definition at line 132 of file SkDeflate.cpp.

                                            {
    return fImpl->fZStream.total_in + fImpl->fInBufferIndex;
}

finalize()

void SkDeflateWStream::finalize

(

)

Write the end of the compressed stream. All subsequent calls to write() will fail. Subsequent calls to finalize() do nothing.

Definition at line 96 of file SkDeflate.cpp.

                                {
    TRACE_EVENT0("skia", TRACE_FUNC);
    if (!fImpl->fOut) {
        return;
    }
    do_deflate(Z_FINISH, &fImpl->fZStream, fImpl->fOut, fImpl->fInBuffer,
               fImpl->fInBufferIndex);
    (void)deflateEnd(&fImpl->fZStream);
    fImpl->fOut = nullptr;
}

write()

bool SkDeflateWStream::write ( const void *  buffer, size_t  size  )

overridevirtual

Called to write bytes to a SkWStream. Returns true on success

Parameters

buffer	the address of at least size bytes to be written to the stream
size	The number of bytes in buffer to write to the stream

Returns

true on success

Implements SkWStream.

Definition at line 107 of file SkDeflate.cpp.

                                                                {
    TRACE_EVENT0("skia", TRACE_FUNC);
    if (!fImpl->fOut) {
        return false;
    }
    const char* buffer = (const char*)void_buffer;
    while (len > 0) {
        size_t tocopy =
                std::min(len, sizeof(fImpl->fInBuffer) - fImpl->fInBufferIndex);
        memcpy(fImpl->fInBuffer + fImpl->fInBufferIndex, buffer, tocopy);
        len -= tocopy;
        buffer += tocopy;
        fImpl->fInBufferIndex += tocopy;
        SkASSERT(fImpl->fInBufferIndex <= sizeof(fImpl->fInBuffer));
 
        // if the buffer isn't filled, don't call into zlib yet.
        if (sizeof(fImpl->fInBuffer) == fImpl->fInBufferIndex) {
            do_deflate(Z_NO_FLUSH, &fImpl->fZStream, fImpl->fOut,
                       fImpl->fInBuffer, fImpl->fInBufferIndex);
            fImpl->fInBufferIndex = 0;
        }
    }
    return true;
}

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The documentation for this class was generated from the following files:

• third_party/skia/src/pdf/SkDeflate.h
• third_party/skia/src/pdf/SkDeflate.cpp