1
2/*
3 * Copyright 2008 The Android Open Source Project
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10#ifndef SkReader32_DEFINED
11#define SkReader32_DEFINED
12
13#include "SkMatrix.h"
14#include "SkPath.h"
15#include "SkRegion.h"
16#include "SkRRect.h"
17#include "SkScalar.h"
18
19class SkString;
20
21class SkReader32 : SkNoncopyable {
22public:
23    SkReader32() : fCurr(NULL), fStop(NULL), fBase(NULL) {}
24    SkReader32(const void* data, size_t size)  {
25        this->setMemory(data, size);
26    }
27
28    void setMemory(const void* data, size_t size) {
29        SkASSERT(ptr_align_4(data));
30        SkASSERT(SkAlign4(size) == size);
31
32        fBase = fCurr = (const char*)data;
33        fStop = (const char*)data + size;
34    }
35
36    size_t size() const { return fStop - fBase; }
37    size_t offset() const { return fCurr - fBase; }
38    bool eof() const { return fCurr >= fStop; }
39    const void* base() const { return fBase; }
40    const void* peek() const { return fCurr; }
41
42    size_t available() const { return fStop - fCurr; }
43    bool isAvailable(size_t size) const { return size <= this->available(); }
44
45    void rewind() { fCurr = fBase; }
46
47    void setOffset(size_t offset) {
48        SkASSERT(SkAlign4(offset) == offset);
49        SkASSERT(offset <= this->size());
50        fCurr = fBase + offset;
51    }
52
53    bool readBool() { return this->readInt() != 0; }
54
55    int32_t readInt() {
56        SkASSERT(ptr_align_4(fCurr));
57        int32_t value = *(const int32_t*)fCurr;
58        fCurr += sizeof(value);
59        SkASSERT(fCurr <= fStop);
60        return value;
61    }
62
63    void* readPtr() {
64        void* ptr;
65        // we presume this "if" is resolved at compile-time
66        if (4 == sizeof(void*)) {
67            ptr = *(void**)fCurr;
68        } else {
69            memcpy(&ptr, fCurr, sizeof(void*));
70        }
71        fCurr += sizeof(void*);
72        return ptr;
73    }
74
75    SkScalar readScalar() {
76        SkASSERT(ptr_align_4(fCurr));
77        SkScalar value = *(const SkScalar*)fCurr;
78        fCurr += sizeof(value);
79        SkASSERT(fCurr <= fStop);
80        return value;
81    }
82
83    const void* skip(size_t size) {
84        SkASSERT(ptr_align_4(fCurr));
85        const void* addr = fCurr;
86        fCurr += SkAlign4(size);
87        SkASSERT(fCurr <= fStop);
88        return addr;
89    }
90
91    template <typename T> const T& skipT() {
92        SkASSERT(SkAlign4(sizeof(T)) == sizeof(T));
93        return *(const T*)this->skip(sizeof(T));
94    }
95
96    void read(void* dst, size_t size) {
97        SkASSERT(0 == size || dst != NULL);
98        SkASSERT(ptr_align_4(fCurr));
99        memcpy(dst, fCurr, size);
100        fCurr += SkAlign4(size);
101        SkASSERT(fCurr <= fStop);
102    }
103
104    uint8_t readU8() { return (uint8_t)this->readInt(); }
105    uint16_t readU16() { return (uint16_t)this->readInt(); }
106    int32_t readS32() { return this->readInt(); }
107    uint32_t readU32() { return this->readInt(); }
108
109    bool readPath(SkPath* path) {
110        return readObjectFromMemory(path);
111    }
112
113    bool readMatrix(SkMatrix* matrix) {
114        return readObjectFromMemory(matrix);
115    }
116
117    bool readRRect(SkRRect* rrect) {
118        return readObjectFromMemory(rrect);
119    }
120
121    bool readRegion(SkRegion* rgn) {
122        return readObjectFromMemory(rgn);
123    }
124
125    /**
126     *  Read the length of a string (written by SkWriter32::writeString) into
127     *  len (if len is not NULL) and return the null-ternimated address of the
128     *  string within the reader's buffer.
129     */
130    const char* readString(size_t* len = NULL);
131
132    /**
133     *  Read the string (written by SkWriter32::writeString) and return it in
134     *  copy (if copy is not null). Return the length of the string.
135     */
136    size_t readIntoString(SkString* copy);
137
138private:
139    template <typename T> bool readObjectFromMemory(T* obj) {
140        size_t size = obj->readFromMemory(this->peek(), this->available());
141        // If readFromMemory() fails (which means that available() was too small), it returns 0
142        bool success = (size > 0) && (size <= this->available()) && (SkAlign4(size) == size);
143        // In case of failure, we want to skip to the end
144        (void)this->skip(success ? size : this->available());
145        return success;
146    }
147
148    // these are always 4-byte aligned
149    const char* fCurr;  // current position within buffer
150    const char* fStop;  // end of buffer
151    const char* fBase;  // beginning of buffer
152
153#ifdef SK_DEBUG
154    static bool ptr_align_4(const void* ptr) {
155        return (((const char*)ptr - (const char*)NULL) & 3) == 0;
156    }
157#endif
158};
159
160#endif
161