skia2/include/core/SkBuffer.h

/*
 * Copyright (C) 2006 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 SkBuffer_DEFINED
#define SkBuffer_DEFINED

#include "SkScalar.h"

/** \class SkRBuffer

    Light weight class for reading data from a memory block.
    The RBuffer is given the buffer to read from, with either a specified size
    or no size (in which case no range checking is performed). It is iillegal
    to attempt to read a value from an empty RBuffer (data == null). 
*/
class SkRBuffer : SkNoncopyable {
public:
    SkRBuffer() : fData(0), fPos(0), fStop(0) {}
    /** Initialize RBuffer with a data pointer, but no specified length.
        This signals the RBuffer to not perform range checks during reading.
    */
    SkRBuffer(const void* data) {
        fData = (const char*)data;
        fPos = (const char*)data;
        fStop = 0;  // no bounds checking
    }
    /** Initialize RBuffer with a data point and length.
    */
    SkRBuffer(const void* data, size_t size) {
        SkASSERT(data != 0 || size == 0);
        fData = (const char*)data;
        fPos = (const char*)data;
        fStop = (const char*)data + size;
    }
    
    /** Return the number of bytes that have been read from the beginning
        of the data pointer.
    */
    size_t  pos() const { return fPos - fData; }
    /** Return the total size of the data pointer. Only defined if the length was
        specified in the constructor or in a call to reset().
    */
    size_t  size() const { return fStop - fData; }
    /** Return true if the buffer has read to the end of the data pointer.
        Only defined if the length was specified in the constructor or in a call
        to reset(). Always returns true if the length was not specified.
    */
    bool    eof() const { return fPos >= fStop; }

    /** Read the specified number of bytes from the data pointer. If buffer is not
        null, copy those bytes into buffer.
    */
    void read(void* buffer, size_t size) {
        if (size) {
            this->readNoSizeCheck(buffer, size);
        }
    }

    const void* skip(size_t size); // return start of skipped data
    size_t  skipToAlign4();

    void*       readPtr() { void* ptr; read(&ptr, sizeof(ptr)); return ptr; }
    SkScalar    readScalar() { SkScalar x; read(&x, 4); return x; }
    uint32_t    readU32() { uint32_t x; read(&x, 4); return x; }
    int32_t     readS32() { int32_t x; read(&x, 4); return x; }
    uint16_t    readU16() { uint16_t x; read(&x, 2); return x; }
    int16_t     readS16() { int16_t x; read(&x, 2); return x; }
    uint8_t     readU8() { uint8_t x; read(&x, 1); return x; }
    bool        readBool() { return this->readU8() != 0; }

protected:
    void    readNoSizeCheck(void* buffer, size_t size);

    const char* fData;
    const char* fPos;
    const char* fStop;
};

/** \class SkWBuffer

    Light weight class for writing data to a memory block.
    The WBuffer is given the buffer to write into, with either a specified size
    or no size, in which case no range checking is performed. An empty WBuffer
    is legal, in which case no data is ever written, but the relative pos()
    is updated.
*/
class SkWBuffer : SkNoncopyable {
public:
    SkWBuffer() : fData(0), fPos(0), fStop(0) {}
    SkWBuffer(void* data) { reset(data); }
    SkWBuffer(void* data, size_t size) { reset(data, size); }

    void reset(void* data) {
        fData = (char*)data;
        fPos = (char*)data;
        fStop = 0;  // no bounds checking
    }

    void reset(void* data, size_t size) {
        SkASSERT(data != 0 || size == 0);
        fData = (char*)data;
        fPos = (char*)data;
        fStop = (char*)data + size;
    }
    
    size_t  pos() const { return fPos - fData; }
    void*   skip(size_t size); // return start of skipped data

    void write(const void* buffer, size_t size) {
        if (size) {
            this->writeNoSizeCheck(buffer, size);
        }
    }

    size_t  padToAlign4();

    void    writePtr(const void* x) { this->writeNoSizeCheck(&x, sizeof(x)); }
    void    writeScalar(SkScalar x) { this->writeNoSizeCheck(&x, 4); }
    void    write32(int32_t x) { this->writeNoSizeCheck(&x, 4); }
    void    write16(int16_t x) { this->writeNoSizeCheck(&x, 2); }
    void    write8(int8_t x) { this->writeNoSizeCheck(&x, 1); }
    void    writeBool(bool x) { this->write8(x); }

protected:
    void    writeNoSizeCheck(const void* buffer, size_t size);

    char* fData;
    char* fPos;
    char* fStop;
};

#endif