CursorWindow.h revision 45e2e95c2ffeb2d978e2cce80b729ef6ada3b8d2 
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 <inttypes.h>
21#include <stddef.h>
22#include <stdint.h>
23
24#include <binder/Parcel.h>
25#include <log/log.h>
26#include <utils/String8.h>
27
28#if LOG_NDEBUG
29
30#define IF_LOG_WINDOW() if (false)
31#define LOG_WINDOW(...)
32
33#else
34
35#define IF_LOG_WINDOW() IF_ALOG(LOG_DEBUG, "CursorWindow")
36#define LOG_WINDOW(...) ALOG(LOG_DEBUG, "CursorWindow", __VA_ARGS__)
37
38#endif
39
40namespace android {
41
42/**
43 * This class stores a set of rows from a database in a buffer. The begining of the
44 * window has first chunk of RowSlots, which are offsets to the row directory, followed by
45 * an offset to the next chunk in a linked-list of additional chunk of RowSlots in case
46 * the pre-allocated chunk isn't big enough to refer to all rows. Each row directory has a
47 * FieldSlot per column, which has the size, offset, and type of the data for that field.
48 * Note that the data types come from sqlite3.h.
49 *
50 * Strings are stored in UTF-8.
51 */
52class CursorWindow {
53    CursorWindow(const String8& name, int ashmemFd,
54            void* data, size_t size, bool readOnly);
55
56public:
57    /* Field types. */
58    enum {
59        FIELD_TYPE_NULL = 0,
60        FIELD_TYPE_INTEGER = 1,
61        FIELD_TYPE_FLOAT = 2,
62        FIELD_TYPE_STRING = 3,
63        FIELD_TYPE_BLOB = 4,
64    };
65
66    /* Opaque type that describes a field slot. */
67    struct FieldSlot {
68    private:
69        int32_t type;
70        union {
71            double d;
72            int64_t l;
73            struct {
74                uint32_t offset;
75                uint32_t size;
76            } buffer;
77        } data;
78
79        friend class CursorWindow;
80    } __attribute((packed));
81
82    ~CursorWindow();
83
84    static status_t create(const String8& name, size_t size, CursorWindow** outCursorWindow);
85    static status_t createFromParcel(Parcel* parcel, CursorWindow** outCursorWindow);
86
87    status_t writeToParcel(Parcel* parcel);
88
89    inline String8 name() { return mName; }
90    inline size_t size() { return mSize; }
91    inline size_t freeSpace() { return mSize - mHeader->freeOffset; }
92    inline uint32_t getNumRows() { return mHeader->numRows; }
93    inline uint32_t getNumColumns() { return mHeader->numColumns; }
94
95    status_t clear();
96    status_t setNumColumns(uint32_t numColumns);
97
98    /**
99     * Allocate a row slot and its directory.
100     * The row is initialized will null entries for each field.
101     */
102    status_t allocRow();
103    status_t freeLastRow();
104
105    status_t putBlob(uint32_t row, uint32_t column, const void* value, size_t size);
106    status_t putString(uint32_t row, uint32_t column, const char* value, size_t sizeIncludingNull);
107    status_t putLong(uint32_t row, uint32_t column, int64_t value);
108    status_t putDouble(uint32_t row, uint32_t column, double value);
109    status_t putNull(uint32_t row, uint32_t column);
110
111    /**
112     * Gets the field slot at the specified row and column.
113     * Returns null if the requested row or column is not in the window.
114     */
115    FieldSlot* getFieldSlot(uint32_t row, uint32_t column);
116
117    inline int32_t getFieldSlotType(FieldSlot* fieldSlot) {
118        return fieldSlot->type;
119    }
120
121    inline int64_t getFieldSlotValueLong(FieldSlot* fieldSlot) {
122        return fieldSlot->data.l;
123    }
124
125    inline double getFieldSlotValueDouble(FieldSlot* fieldSlot) {
126        return fieldSlot->data.d;
127    }
128
129    inline const char* getFieldSlotValueString(FieldSlot* fieldSlot,
130            size_t* outSizeIncludingNull) {
131        *outSizeIncludingNull = fieldSlot->data.buffer.size;
132        return static_cast<char*>(offsetToPtr(
133                fieldSlot->data.buffer.offset, fieldSlot->data.buffer.size));
134    }
135
136    inline const void* getFieldSlotValueBlob(FieldSlot* fieldSlot, size_t* outSize) {
137        *outSize = fieldSlot->data.buffer.size;
138        return offsetToPtr(fieldSlot->data.buffer.offset, fieldSlot->data.buffer.size);
139    }
140
141private:
142    static const size_t ROW_SLOT_CHUNK_NUM_ROWS = 100;
143
144    struct Header {
145        // Offset of the lowest unused byte in the window.
146        uint32_t freeOffset;
147
148        // Offset of the first row slot chunk.
149        uint32_t firstChunkOffset;
150
151        uint32_t numRows;
152        uint32_t numColumns;
153    };
154
155    struct RowSlot {
156        uint32_t offset;
157    };
158
159    struct RowSlotChunk {
160        RowSlot slots[ROW_SLOT_CHUNK_NUM_ROWS];
161        uint32_t nextChunkOffset;
162    };
163
164    String8 mName;
165    int mAshmemFd;
166    void* mData;
167    size_t mSize;
168    bool mReadOnly;
169    Header* mHeader;
170
171    inline void* offsetToPtr(uint32_t offset, uint32_t bufferSize = 0) {
172        if (offset >= mSize) {
173            ALOGE("Offset %" PRIu32 " out of bounds, max value %zu", offset, mSize);
174            return NULL;
175        }
176        if (offset + bufferSize > mSize) {
177            ALOGE("End offset %" PRIu32 " out of bounds, max value %zu",
178                    offset + bufferSize, mSize);
179            return NULL;
180        }
181        return static_cast<uint8_t*>(mData) + offset;
182    }
183
184    inline uint32_t offsetFromPtr(void* ptr) {
185        return static_cast<uint8_t*>(ptr) - static_cast<uint8_t*>(mData);
186    }
187
188    /**
189     * Allocate a portion of the window. Returns the offset
190     * of the allocation, or 0 if there isn't enough space.
191     * If aligned is true, the allocation gets 4 byte alignment.
192     */
193    uint32_t alloc(size_t size, bool aligned = false);
194
195    RowSlot* getRowSlot(uint32_t row);
196    RowSlot* allocRowSlot();
197
198    status_t putBlobOrString(uint32_t row, uint32_t column,
199            const void* value, size_t size, int32_t type);
200};
201
202}; // namespace android
203
204#endif
205