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 #ifndef SkBuffer_DEFINED
9 #define SkBuffer_DEFINED
10 
11 #include "SkNoncopyable.h"
12 #include "SkSafeMath.h"
13 #include "SkScalar.h"
14 #include "SkTypes.h"
15 
16 #include <limits>
17 
18 /** \class SkRBuffer
19 
20     Light weight class for reading data from a memory block.
21     The RBuffer is given the buffer to read from, with either a specified size
22     or no size (in which case no range checking is performed). It is iillegal
23     to attempt to read a value from an empty RBuffer (data == null).
24 */
25 class SkRBuffer : SkNoncopyable {
26 public:
SkRBuffer()27     SkRBuffer() : fData(nullptr), fPos(nullptr), fStop(nullptr) {}
28 
29     /** Initialize RBuffer with a data point and length.
30     */
SkRBuffer(const void * data,size_t size)31     SkRBuffer(const void* data, size_t size) {
32         SkASSERT(data != nullptr || size == 0);
33         fData = (const char*)data;
34         fPos = (const char*)data;
35         fStop = (const char*)data + size;
36     }
37 
38     /** Return the number of bytes that have been read from the beginning
39         of the data pointer.
40     */
pos()41     size_t pos() const { return fPos - fData; }
42     /** Return the total size of the data pointer. Only defined if the length was
43         specified in the constructor or in a call to reset().
44     */
size()45     size_t size() const { return fStop - fData; }
46     /** Return true if the buffer has read to the end of the data pointer.
47         Only defined if the length was specified in the constructor or in a call
48         to reset(). Always returns true if the length was not specified.
49     */
eof()50     bool eof() const { return fPos >= fStop; }
51 
available()52     size_t available() const { return fStop - fPos; }
53 
isValid()54     bool isValid() const { return fValid; }
55 
56     /** Read the specified number of bytes from the data pointer. If buffer is not
57         null, copy those bytes into buffer.
58     */
59     bool read(void* buffer, size_t size);
60     bool skipToAlign4();
61 
readU8(uint8_t * x)62     bool readU8(uint8_t* x)   { return this->read(x, 1); }
readS32(int32_t * x)63     bool readS32(int32_t* x)  { return this->read(x, 4); }
readU32(uint32_t * x)64     bool readU32(uint32_t* x) { return this->read(x, 4); }
65 
66     // returns nullptr on failure
67     const void* skip(size_t bytes);
skipCount(size_t count)68     template <typename T> const T* skipCount(size_t count) {
69         return static_cast<const T*>(this->skip(SkSafeMath::Mul(count, sizeof(T))));
70     }
71 
72 private:
73     const char* fData;
74     const char* fPos;
75     const char* fStop;
76     bool        fValid = true;
77 };
78 
79 /** \class SkWBuffer
80 
81     Light weight class for writing data to a memory block.
82     The WBuffer is given the buffer to write into, with either a specified size
83     or no size, in which case no range checking is performed. An empty WBuffer
84     is legal, in which case no data is ever written, but the relative pos()
85     is updated.
86 */
87 class SkWBuffer : SkNoncopyable {
88 public:
SkWBuffer()89     SkWBuffer() : fData(nullptr), fPos(nullptr), fStop(nullptr) {}
SkWBuffer(void * data)90     SkWBuffer(void* data) { reset(data); }
SkWBuffer(void * data,size_t size)91     SkWBuffer(void* data, size_t size) { reset(data, size); }
92 
reset(void * data)93     void reset(void* data) {
94         fData = (char*)data;
95         fPos = (char*)data;
96         fStop = nullptr;  // no bounds checking
97     }
98 
reset(void * data,size_t size)99     void reset(void* data, size_t size) {
100         SkASSERT(data != nullptr || size == 0);
101         fData = (char*)data;
102         fPos = (char*)data;
103         fStop = (char*)data + size;
104     }
105 
pos()106     size_t  pos() const { return fPos - fData; }
107     void*   skip(size_t size); // return start of skipped data
108 
write(const void * buffer,size_t size)109     void write(const void* buffer, size_t size) {
110         if (size) {
111             this->writeNoSizeCheck(buffer, size);
112         }
113     }
114 
115     size_t  padToAlign4();
116 
writePtr(const void * x)117     void    writePtr(const void* x) { this->writeNoSizeCheck(&x, sizeof(x)); }
writeScalar(SkScalar x)118     void    writeScalar(SkScalar x) { this->writeNoSizeCheck(&x, 4); }
write32(int32_t x)119     void    write32(int32_t x) { this->writeNoSizeCheck(&x, 4); }
write16(int16_t x)120     void    write16(int16_t x) { this->writeNoSizeCheck(&x, 2); }
write8(int8_t x)121     void    write8(int8_t x) { this->writeNoSizeCheck(&x, 1); }
writeBool(bool x)122     void    writeBool(bool x) { this->write8(x); }
123 
124 private:
125     void    writeNoSizeCheck(const void* buffer, size_t size);
126 
127     char* fData;
128     char* fPos;
129     char* fStop;
130 };
131 
132 #endif
133