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 
40 namespace 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  */
52 class CursorWindow {
53     CursorWindow(const String8& name, int ashmemFd,
54             void* data, size_t size, bool readOnly);
55 
56 public:
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 
name()89     inline String8 name() { return mName; }
size()90     inline size_t size() { return mSize; }
freeSpace()91     inline size_t freeSpace() { return mSize - mHeader->freeOffset; }
getNumRows()92     inline uint32_t getNumRows() { return mHeader->numRows; }
getNumColumns()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 
getFieldSlotType(FieldSlot * fieldSlot)117     inline int32_t getFieldSlotType(FieldSlot* fieldSlot) {
118         return fieldSlot->type;
119     }
120 
getFieldSlotValueLong(FieldSlot * fieldSlot)121     inline int64_t getFieldSlotValueLong(FieldSlot* fieldSlot) {
122         return fieldSlot->data.l;
123     }
124 
getFieldSlotValueDouble(FieldSlot * fieldSlot)125     inline double getFieldSlotValueDouble(FieldSlot* fieldSlot) {
126         return fieldSlot->data.d;
127     }
128 
getFieldSlotValueString(FieldSlot * fieldSlot,size_t * outSizeIncludingNull)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 
getFieldSlotValueBlob(FieldSlot * fieldSlot,size_t * outSize)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 
141 private:
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 
offsetFromPtr(void * ptr)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