skia2/include/core/SkWriter32.h

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef SkWriter32_DEFINED
#define SkWriter32_DEFINED

#include "SkTypes.h"

#include "SkScalar.h"
#include "SkPoint.h"
#include "SkRect.h"

class SkStream;
class SkWStream;

class SkWriter32 : SkNoncopyable {
public:
    SkWriter32(size_t minSize) {
        fMinSize = minSize;
        fSize = 0;
        fHead = fTail = NULL;
        fSingleBlock = NULL;
    }
    ~SkWriter32();

    /**
     *  Returns the single block backing the writer, or NULL if the memory is
     *  to be dynamically allocated.
     */
    void* getSingleBlock() const { return fSingleBlock; }

    /**
     *  Specify the single block to back the writer, rathern than dynamically
     *  allocating the memory. If block == NULL, then the writer reverts to
     *  dynamic allocation (and resets).
     */
    void reset(void* block, size_t size);
                    
    bool writeBool(bool value) {
        this->writeInt(value);
        return value;
    }
    
    void writeInt(int32_t value) {
        *(int32_t*)this->reserve(sizeof(value)) = value;
    }
    
    void write8(int32_t value) {
        *(int32_t*)this->reserve(sizeof(value)) = value & 0xFF;
    }
    
    void write16(int32_t value) {
        *(int32_t*)this->reserve(sizeof(value)) = value & 0xFFFF;
    }
    
    void write32(int32_t value) {
        *(int32_t*)this->reserve(sizeof(value)) = value;
    }
    
    void writeScalar(SkScalar value) {
        *(SkScalar*)this->reserve(sizeof(value)) = value;
    }
    
    void writePoint(const SkPoint& pt) {
        *(SkPoint*)this->reserve(sizeof(pt)) = pt;
    }
    
    void writeRect(const SkRect& rect) {
        *(SkRect*)this->reserve(sizeof(rect)) = rect;
    }
    
    // write count bytes (must be a multiple of 4)
    void writeMul4(const void* values, size_t size) {
        this->write(values, size);
    }

    /**
     *  Write size bytes from values. size must be a multiple of 4, though
     *  values need not be 4-byte aligned.
     */
    void write(const void* values, size_t size) {
        SkASSERT(SkAlign4(size) == size);
        // if we could query how much is avail in the current block, we might
        // copy that much, and then alloc the rest. That would reduce the waste
        // in the current block
        memcpy(this->reserve(size), values, size);
    }
    
    void writePad(const void* src, size_t size);
    
    // return the current offset (will always be a multiple of 4)
    uint32_t  size() const { return fSize; }
    void      reset();
    uint32_t* reserve(size_t size); // size MUST be multiple of 4

    // return the address of the 4byte int at the specified offset (which must
    // be a multiple of 4. This does not allocate any new space, so the returned
    // address is only valid for 1 int.
    uint32_t* peek32(size_t offset);
    
    // copy into a single buffer (allocated by caller). Must be at least size()
    void flatten(void* dst) const;
    
    // read from the stream, and write up to length bytes. Return the actual
    // number of bytes written.
    size_t readFromStream(SkStream*, size_t length);
    
    bool writeToStream(SkWStream*);

private:
    size_t      fMinSize;
    uint32_t    fSize;

    char*       fSingleBlock;
    uint32_t    fSingleBlockSize;
    
    struct Block;
    Block*  fHead;
    Block*  fTail;

    Block* newBlock(size_t bytes);
};

#endif