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      1 /*
      2  * Copyright 2006 The Android Open Source Project
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 
      9 #ifndef SkBuffer_DEFINED
     10 #define SkBuffer_DEFINED
     11 
     12 #include "SkScalar.h"
     13 #include "SkTypes.h"
     14 
     15 /** \class SkRBuffer
     16 
     17     Light weight class for reading data from a memory block.
     18     The RBuffer is given the buffer to read from, with either a specified size
     19     or no size (in which case no range checking is performed). It is iillegal
     20     to attempt to read a value from an empty RBuffer (data == null).
     21 */
     22 class SkRBuffer : SkNoncopyable {
     23 public:
     24     SkRBuffer() : fData(nullptr), fPos(nullptr), fStop(nullptr) {}
     25 
     26     /** Initialize RBuffer with a data point and length.
     27     */
     28     SkRBuffer(const void* data, size_t size) {
     29         SkASSERT(data != nullptr || size == 0);
     30         fData = (const char*)data;
     31         fPos = (const char*)data;
     32         fStop = (const char*)data + size;
     33     }
     34 
     35     /** Return the number of bytes that have been read from the beginning
     36         of the data pointer.
     37     */
     38     size_t pos() const { return fPos - fData; }
     39     /** Return the total size of the data pointer. Only defined if the length was
     40         specified in the constructor or in a call to reset().
     41     */
     42     size_t size() const { return fStop - fData; }
     43     /** Return true if the buffer has read to the end of the data pointer.
     44         Only defined if the length was specified in the constructor or in a call
     45         to reset(). Always returns true if the length was not specified.
     46     */
     47     bool eof() const { return fPos >= fStop; }
     48 
     49     size_t available() const { return fStop - fPos; }
     50 
     51     bool isValid() const { return fValid; }
     52 
     53     /** Read the specified number of bytes from the data pointer. If buffer is not
     54         null, copy those bytes into buffer.
     55     */
     56     bool read(void* buffer, size_t size);
     57     bool skipToAlign4();
     58 
     59     bool readU8(uint8_t* x)   { return this->read(x, 1); }
     60     bool readS32(int32_t* x)  { return this->read(x, 4); }
     61     bool readU32(uint32_t* x) { return this->read(x, 4); }
     62 
     63 private:
     64     const char* fData;
     65     const char* fPos;
     66     const char* fStop;
     67     bool        fValid = true;
     68 };
     69 
     70 /** \class SkWBuffer
     71 
     72     Light weight class for writing data to a memory block.
     73     The WBuffer is given the buffer to write into, with either a specified size
     74     or no size, in which case no range checking is performed. An empty WBuffer
     75     is legal, in which case no data is ever written, but the relative pos()
     76     is updated.
     77 */
     78 class SkWBuffer : SkNoncopyable {
     79 public:
     80     SkWBuffer() : fData(nullptr), fPos(nullptr), fStop(nullptr) {}
     81     SkWBuffer(void* data) { reset(data); }
     82     SkWBuffer(void* data, size_t size) { reset(data, size); }
     83 
     84     void reset(void* data) {
     85         fData = (char*)data;
     86         fPos = (char*)data;
     87         fStop = nullptr;  // no bounds checking
     88     }
     89 
     90     void reset(void* data, size_t size) {
     91         SkASSERT(data != nullptr || size == 0);
     92         fData = (char*)data;
     93         fPos = (char*)data;
     94         fStop = (char*)data + size;
     95     }
     96 
     97     size_t  pos() const { return fPos - fData; }
     98     void*   skip(size_t size); // return start of skipped data
     99 
    100     void write(const void* buffer, size_t size) {
    101         if (size) {
    102             this->writeNoSizeCheck(buffer, size);
    103         }
    104     }
    105 
    106     size_t  padToAlign4();
    107 
    108     void    writePtr(const void* x) { this->writeNoSizeCheck(&x, sizeof(x)); }
    109     void    writeScalar(SkScalar x) { this->writeNoSizeCheck(&x, 4); }
    110     void    write32(int32_t x) { this->writeNoSizeCheck(&x, 4); }
    111     void    write16(int16_t x) { this->writeNoSizeCheck(&x, 2); }
    112     void    write8(int8_t x) { this->writeNoSizeCheck(&x, 1); }
    113     void    writeBool(bool x) { this->write8(x); }
    114 
    115 private:
    116     void    writeNoSizeCheck(const void* buffer, size_t size);
    117 
    118     char* fData;
    119     char* fPos;
    120     char* fStop;
    121 };
    122 
    123 #endif
    124