core/jni/CursorWindow.h

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); 
 * you may not use this file except in compliance with the License. 
 * You may obtain a copy of the License at 
 *
 *      http://www.apache.org/licenses/LICENSE-2.0 
 *
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the License is distributed on an "AS IS" BASIS, 
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 * See the License for the specific language governing permissions and 
 * limitations under the License.
 */

#ifndef _ANDROID__DATABASE_WINDOW_H
#define _ANDROID__DATABASE_WINDOW_H

#include <cutils/log.h>
#include <stddef.h>
#include <stdint.h>

#include <binder/IMemory.h>
#include <utils/RefBase.h>

#include <jni.h>

#define DEFAULT_WINDOW_SIZE 4096
#define MAX_WINDOW_SIZE (1024 * 1024)
#define WINDOW_ALLOCATION_SIZE 4096

#define ROW_SLOT_CHUNK_NUM_ROWS 16

// Row slots are allocated in chunks of ROW_SLOT_CHUNK_NUM_ROWS,
// with an offset after the rows that points to the next chunk
#define ROW_SLOT_CHUNK_SIZE ((ROW_SLOT_CHUNK_NUM_ROWS * sizeof(row_slot_t)) + sizeof(uint32_t))


#if LOG_NDEBUG

#define IF_LOG_WINDOW() if (false)
#define LOG_WINDOW(...)

#else

#define IF_LOG_WINDOW() IF_LOG(LOG_DEBUG, "CursorWindow")
#define LOG_WINDOW(...) LOG(LOG_DEBUG, "CursorWindow", __VA_ARGS__)

#endif


// When defined to true strings are stored as UTF8, otherwise they're UTF16
#define WINDOW_STORAGE_UTF8 1

// When defined to true numberic values are stored inline in the field_slot_t, otherwise they're allocated in the window
#define WINDOW_STORAGE_INLINE_NUMERICS 1

namespace android {

typedef struct
{
    uint32_t numRows;
    uint32_t numColumns;
} window_header_t;

typedef struct
{
    uint32_t offset;
} row_slot_t;

typedef struct
{
    uint8_t type;
    union {
        double d;
        int64_t l;
        struct {
            uint32_t offset;
            uint32_t size;
        } buffer;
    } data;
} __attribute__((packed)) field_slot_t;

#define FIELD_TYPE_INTEGER 1
#define FIELD_TYPE_FLOAT 2
#define FIELD_TYPE_STRING 3
#define FIELD_TYPE_BLOB 4
#define FIELD_TYPE_NULL 5

/**
 * This class stores a set of rows from a database in a buffer. The begining of the
 * window has first chunk of row_slot_ts, which are offsets to the row directory, followed by
 * an offset to the next chunk in a linked-list of additional chunk of row_slot_ts in case
 * the pre-allocated chunk isn't big enough to refer to all rows. Each row directory has a
 * field_slot_t per column, which has the size, offset, and type of the data for that field.
 * Note that the data types come from sqlite3.h.
 */
class CursorWindow
{
public:
                        CursorWindow(size_t maxSize);
                        CursorWindow(){}
    bool                setMemory(const sp<IMemory>&);
                        ~CursorWindow();

    bool                initBuffer(bool localOnly);
    sp<IMemory>         getMemory() {return mMemory;}

    size_t              size() {return mSize;}
    uint8_t *           data() {return mData;}
    uint32_t            getNumRows() {return mHeader->numRows;}
    uint32_t            getNumColumns() {return mHeader->numColumns;}
    void                freeLastRow() {
                            if (mHeader->numRows > 0) {
                                mHeader->numRows--;
                            }
                        }
    bool                setNumColumns(uint32_t numColumns)
                            {
                                uint32_t cur = mHeader->numColumns;
                                if (cur > 0 && cur != numColumns) {
                                    LOGE("Trying to go from %d columns to %d", cur, numColumns);
                                    return false;
                                }
                                mHeader->numColumns = numColumns;
                                return true;
                            }

    int32_t             freeSpace();

    void                clear();

                        /**
                         * Allocate a row slot and its directory. The returned
                         * pointer points to the begining of the row's directory
                         * or NULL if there wasn't room. The directory is
                         * initialied with NULL entries for each field.
                         */
    field_slot_t *      allocRow();

                        /**
                         * Allocate a portion of the window. Returns the offset
                         * of the allocation, or 0 if there isn't enough space.
                         * If aligned is true, the allocation gets 4 byte alignment.
                         */
    uint32_t            alloc(size_t size, bool aligned = false);

    uint32_t            read_field_slot(int row, int column, field_slot_t * slot);

                        /**
                         * Copy data into the window at the given offset.
                         */
    void                copyIn(uint32_t offset, uint8_t const * data, size_t size);
    void                copyIn(uint32_t offset, int64_t data);
    void                copyIn(uint32_t offset, double data);

    void                copyOut(uint32_t offset, uint8_t * data, size_t size);
    int64_t             copyOutLong(uint32_t offset);
    double              copyOutDouble(uint32_t offset);

    bool                putLong(unsigned int row, unsigned int col, int64_t value);
    bool                putDouble(unsigned int row, unsigned int col, double value);
    bool                putNull(unsigned int row, unsigned int col);

    bool                getLong(unsigned int row, unsigned int col, int64_t * valueOut);
    bool                getDouble(unsigned int row, unsigned int col, double * valueOut);
    bool                getNull(unsigned int row, unsigned int col, bool * valueOut);

    uint8_t *           offsetToPtr(uint32_t offset) {return mData + offset;}

    row_slot_t *        allocRowSlot();

    row_slot_t *        getRowSlot(int row);
    
                        /**
                         * return NULL if Failed to find rowSlot or
                         * Invalid rowSlot
                         */
    field_slot_t *      getFieldSlotWithCheck(int row, int column);
    field_slot_t *      getFieldSlot(int row, int column)
                            {
                                int fieldDirOffset = getRowSlot(row)->offset;
                                return ((field_slot_t *)offsetToPtr(fieldDirOffset)) + column;
                            }

private:
    uint8_t * mData;
    size_t mSize;
    size_t mMaxSize;
    window_header_t * mHeader;
    sp<IMemory> mMemory;

    /**
     * Offset of the lowest unused data byte in the array.
     */
    uint32_t mFreeOffset;
};

}; // namespace android

#endif