eXtremeDB DLL 笔记

DLL 例子

// 预处理
#define int1 signed<1>
#define int2 signed<2>
#define int4 signed<4>
#define uint4 unsigned<4>
#define uint2 unsigned<2>
#define uint1 unsigned<1>

// 结构体声明
struct SampleStruct {
    uint2 s1;
    char<20> s2;
};
struct BigStruct {
    string      str;
    uint2       u2;
    uint4       u4;
    vector     <SampleStruct> vss;
};

// DDL 声明语句
declare database simple;

/*
* estimated number of class instances is in square brackets
* 方括号中为估计的实例数
*/
declare OID SampleStruct[20000];

/*
* “compact” keyword: Total object size, including overhead is less than 64K.
* Size calculation does NOT count size of blob(s) fields
* embedded in the class
*
* compact 关键字：总对象大小，包括开销小于 64K
* 大小计算不计算 Blob 字段的大小
*
*/
compact class SampleClass {

    /* basic data types 基本数据类型 */
    uint1 a = 0;
    uint2 b;
    uint4 c;

    /* oid reference  */
    ref   d;

    /* vectors - could be made of any type */
    vector <uint2>        numbers;
    vector <SampleStruct> ss;

    /* strings are limited to 64K */
    string                str;

    /* Binary data object, blobs are unlimited*/
    blob                  blo;

    /* optional structure, the value could be missing */
    optional BigStruct big_struct;

    /* voluntary means could be initiated and dropped at runtime
    * unique    means unique
    * tree      means tree-based index (sort order is
    * supported)
    * hash      means hash-based index
    * list      means the objects could be sequentially scanned
    */
    voluntary unique tree< a,b,ss.s2> SAM;

    /* estimated number of class instances is in square brackets */
    hash <a>     AAAA[10000];
    hash <ss.s2> SSS2[10000];
    hash <numbers> NNNN[10000];

    event <new> new;
    event <delete> delete;
    event <a update> update;

    autoid;
    oid;
    list;
};