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 
39 namespace 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  */
51 class CursorWindow {
52     CursorWindow(const String8& name, int ashmemFd,
53             void* data, size_t size, bool readOnly);
54 
55 public:
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 
name()88     inline String8 name() { return mName; }
size()89     inline size_t size() { return mSize; }
freeSpace()90     inline size_t freeSpace() { return mSize - mHeader->freeOffset; }
getNumRows()91     inline uint32_t getNumRows() { return mHeader->numRows; }
getNumColumns()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 
getFieldSlotType(FieldSlot * fieldSlot)116     inline int32_t getFieldSlotType(FieldSlot* fieldSlot) {
117         return fieldSlot->type;
118     }
119 
getFieldSlotValueLong(FieldSlot * fieldSlot)120     inline int64_t getFieldSlotValueLong(FieldSlot* fieldSlot) {
121         return fieldSlot->data.l;
122     }
123 
getFieldSlotValueDouble(FieldSlot * fieldSlot)124     inline double getFieldSlotValueDouble(FieldSlot* fieldSlot) {
125         return fieldSlot->data.d;
126     }
127 
getFieldSlotValueString(FieldSlot * fieldSlot,size_t * outSizeIncludingNull)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 
getFieldSlotValueBlob(FieldSlot * fieldSlot,size_t * outSize)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 
139 private:
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 
offsetToPtr(uint32_t offset)169     inline void* offsetToPtr(uint32_t offset) {
170         return static_cast<uint8_t*>(mData) + offset;
171     }
172 
offsetFromPtr(void * ptr)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