CursorWindow.h revision 49d2b1864c3dfec6faff74d67cb2527a8f1af5a8 
1/*
2 * Copyright (C) 2006 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef _ANDROID__DATABASE_WINDOW_H
18#define _ANDROID__DATABASE_WINDOW_H
19
20#include <cutils/log.h>
21#include <stddef.h>
22#include <stdint.h>
23
24#include <binder/Parcel.h>
25#include <utils/String8.h>
26
27#if LOG_NDEBUG
28
29#define IF_LOG_WINDOW() if (false)
30#define LOG_WINDOW(...)
31
32#else
33
34#define IF_LOG_WINDOW() IF_ALOG(LOG_DEBUG, "CursorWindow")
35#define LOG_WINDOW(...) ALOG(LOG_DEBUG, "CursorWindow", __VA_ARGS__)
36
37#endif
38
39namespace android {
40
41/**
42 * This class stores a set of rows from a database in a buffer. The begining of the
43 * window has first chunk of RowSlots, which are offsets to the row directory, followed by
44 * an offset to the next chunk in a linked-list of additional chunk of RowSlots in case
45 * the pre-allocated chunk isn't big enough to refer to all rows. Each row directory has a
46 * FieldSlot per column, which has the size, offset, and type of the data for that field.
47 * Note that the data types come from sqlite3.h.
48 *
49 * Strings are stored in UTF-8.
50 */
51class CursorWindow {
52    CursorWindow(const String8& name, int ashmemFd,
53            void* data, size_t size, bool readOnly);
54
55public:
56    /* Field types. */
57    enum {
58        FIELD_TYPE_NULL = 0,
59        FIELD_TYPE_INTEGER = 1,
60        FIELD_TYPE_FLOAT = 2,
61        FIELD_TYPE_STRING = 3,
62        FIELD_TYPE_BLOB = 4,
63    };
64
65    /* Opaque type that describes a field slot. */
66    struct FieldSlot {
67    private:
68        int32_t type;
69        union {
70            double d;
71            int64_t l;
72            struct {
73                uint32_t offset;
74                uint32_t size;
75            } buffer;
76        } data;
77
78        friend class CursorWindow;
79    } __attribute((packed));
80
81    ~CursorWindow();
82
83    static status_t create(const String8& name, size_t size, CursorWindow** outCursorWindow);
84    static status_t createFromParcel(Parcel* parcel, CursorWindow** outCursorWindow);
85
86    status_t writeToParcel(Parcel* parcel);
87
88    inline String8 name() { return mName; }
89    inline size_t size() { return mSize; }
90    inline size_t freeSpace() { return mSize - mHeader->freeOffset; }
91    inline uint32_t getNumRows() { return mHeader->numRows; }
92    inline uint32_t getNumColumns() { return mHeader->numColumns; }
93
94    status_t clear();
95    status_t setNumColumns(uint32_t numColumns);
96
97    /**
98     * Allocate a row slot and its directory.
99     * The row is initialized will null entries for each field.
100     */
101    status_t allocRow();
102    status_t freeLastRow();
103
104    status_t putBlob(uint32_t row, uint32_t column, const void* value, size_t size);
105    status_t putString(uint32_t row, uint32_t column, const char* value, size_t sizeIncludingNull);
106    status_t putLong(uint32_t row, uint32_t column, int64_t value);
107    status_t putDouble(uint32_t row, uint32_t column, double value);
108    status_t putNull(uint32_t row, uint32_t column);
109
110    /**
111     * Gets the field slot at the specified row and column.
112     * Returns null if the requested row or column is not in the window.
113     */
114    FieldSlot* getFieldSlot(uint32_t row, uint32_t column);
115
116    inline int32_t getFieldSlotType(FieldSlot* fieldSlot) {
117        return fieldSlot->type;
118    }
119
120    inline int64_t getFieldSlotValueLong(FieldSlot* fieldSlot) {
121        return fieldSlot->data.l;
122    }
123
124    inline double getFieldSlotValueDouble(FieldSlot* fieldSlot) {
125        return fieldSlot->data.d;
126    }
127
128    inline const char* getFieldSlotValueString(FieldSlot* fieldSlot,
129            size_t* outSizeIncludingNull) {
130        *outSizeIncludingNull = fieldSlot->data.buffer.size;
131        return static_cast<char*>(offsetToPtr(fieldSlot->data.buffer.offset));
132    }
133
134    inline const void* getFieldSlotValueBlob(FieldSlot* fieldSlot, size_t* outSize) {
135        *outSize = fieldSlot->data.buffer.size;
136        return offsetToPtr(fieldSlot->data.buffer.offset);
137    }
138
139private:
140    static const size_t ROW_SLOT_CHUNK_NUM_ROWS = 100;
141
142    struct Header {
143        // Offset of the lowest unused byte in the window.
144        uint32_t freeOffset;
145
146        // Offset of the first row slot chunk.
147        uint32_t firstChunkOffset;
148
149        uint32_t numRows;
150        uint32_t numColumns;
151    };
152
153    struct RowSlot {
154        uint32_t offset;
155    };
156
157    struct RowSlotChunk {
158        RowSlot slots[ROW_SLOT_CHUNK_NUM_ROWS];
159        uint32_t nextChunkOffset;
160    };
161
162    String8 mName;
163    int mAshmemFd;
164    void* mData;
165    size_t mSize;
166    bool mReadOnly;
167    Header* mHeader;
168
169    inline void* offsetToPtr(uint32_t offset) {
170        return static_cast<uint8_t*>(mData) + offset;
171    }
172
173    inline uint32_t offsetFromPtr(void* ptr) {
174        return static_cast<uint8_t*>(ptr) - static_cast<uint8_t*>(mData);
175    }
176
177    /**
178     * Allocate a portion of the window. Returns the offset
179     * of the allocation, or 0 if there isn't enough space.
180     * If aligned is true, the allocation gets 4 byte alignment.
181     */
182    uint32_t alloc(size_t size, bool aligned = false);
183
184    RowSlot* getRowSlot(uint32_t row);
185    RowSlot* allocRowSlot();
186
187    status_t putBlobOrString(uint32_t row, uint32_t column,
188            const void* value, size_t size, int32_t type);
189};
190
191}; // namespace android
192
193#endif
194