include/pipe/SkGPipe.h

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */



#ifndef SkGPipe_DEFINED
#define SkGPipe_DEFINED

#include "SkWriter32.h"
#include "SkFlattenable.h"

class SkCanvas;

// XLib.h might have defined Status already (ugh)
#ifdef Status
    #undef Status
#endif

class SkGPipeReader {
public:
    SkGPipeReader();
    SkGPipeReader(SkCanvas* target);
    ~SkGPipeReader();

    enum Status {
        kDone_Status,   //!< no more data expected from reader
        kEOF_Status,    //!< need more data from reader
        kError_Status,  //!< encountered error
        kReadAtom_Status//!< finished reading an atom
    };

    enum PlaybackFlags {
        kReadAtom_PlaybackFlag = 0x1, //!< playback a single command from the stream
        kSilent_PlaybackFlag   = 0x2, //!< playback without drawing
    };

    void setCanvas(SkCanvas*);
    // data must be 4-byte aligned
    // length must be a multiple of 4
    Status playback(const void* data, size_t length, uint32_t playbackFlags = 0,
                    size_t* bytesRead = NULL);
private:
    SkCanvas*           fCanvas;
    class SkGPipeState* fState;
};

///////////////////////////////////////////////////////////////////////////////

class SkGPipeCanvas;

class SkGPipeController {
public:
    SkGPipeController() : fCanvas(NULL) {}
    virtual ~SkGPipeController();

    /**
     *  Called periodically by the writer, to get a working buffer of RAM to
     *  write into. The actual size of the block is also returned, and must be
     *  actual >= minRequest. If NULL is returned, then actual is ignored and
     *  writing will stop.
     *
     *  The returned block must be 4-byte aligned, and actual must be a
     *  multiple of 4.
     *  minRequest will always be a multiple of 4.
     */
    virtual void* requestBlock(size_t minRequest, size_t* actual) = 0;

    /**
     *  This is called each time some atomic portion of the data has been
     *  written to the block (most recently returned by requestBlock()).
     *  If bytes == 0, then the writer has finished.
     *
     *  bytes will always be a multiple of 4.
     */
    virtual void notifyWritten(size_t bytes) = 0;
    virtual int numberOfReaders() const { return 1; }

private:
    friend class SkGPipeWriter;
    void setCanvas(SkGPipeCanvas*);

    SkGPipeCanvas* fCanvas;
};

class SkGPipeWriter {
public:
    SkGPipeWriter();
    ~SkGPipeWriter();

    bool isRecording() const { return NULL != fCanvas; }

    enum Flags {
        /**
         *  Tells the writer that the reader will be in a different process, so
         *  (for example) we cannot put function pointers in the stream.
         */
        kCrossProcess_Flag              = 1 << 0,

        /**
         *  Only meaningful if kCrossProcess_Flag is set. Tells the writer that
         *  in spite of being cross process, it will have shared address space
         *  with the reader, so the two can share large objects (like SkBitmaps).
         */
        kSharedAddressSpace_Flag        = 1 << 1,

        /**
         *  Tells the writer that there will be multiple threads reading the stream
         *  simultaneously.
         */
        kSimultaneousReaders_Flag       = 1 << 2,
    };

    SkCanvas* startRecording(SkGPipeController*, uint32_t flags = 0,
        uint32_t width = kDefaultRecordingCanvasSize,
        uint32_t height = kDefaultRecordingCanvasSize);

    // called in destructor, but can be called sooner once you know there
    // should be no more drawing calls made into the recording canvas.
    void endRecording();

    /**
     *  Tells the writer to commit all recorded draw commands to the
     *  controller immediately.
     *  @param detachCurrentBlock Set to true to request that the next draw
     *      command be recorded in a new block.
     */
    void flushRecording(bool detachCurrentBlock);

    /**
     * Return the amount of bytes being used for recording. Note that this
     * does not include the amount of storage written to the stream, which is
     * controlled by the SkGPipeController.
     * Currently only returns the amount used for SkBitmaps, since they are
     * potentially unbounded (if the client is not calling playback).
     */
    size_t storageAllocatedForRecording() const;

    /**
     * Attempt to reduce the storage allocated for recording by evicting
     * cache resources.
     * @param bytesToFree minimum number of bytes that should be attempted to
     *   be freed.
     * @return number of bytes actually freed.
     */
    size_t freeMemoryIfPossible(size_t bytesToFree);

private:
    enum {
        kDefaultRecordingCanvasSize = 32767,
    };

    SkGPipeCanvas* fCanvas;
    SkWriter32     fWriter;
};

#endif