来一份eXtremeDB使用笔记．1、准备工作：下载eXtremeDB安装包(/)然后将安装或解压至磁盘。

此时可以看到其目录下有host、include、platform和target等目录。

2、用你喜欢的文本编辑器构建一数据库结构，文本内容如下：（举例说明，保存文件名为test.mco）#define int1 signed<1>#define int2 signed<2>#define int4 signed<4>#define int8 signed<8>#define uint8 unsigned<8>#define uint4 unsigned<4>#define uint2 unsigned<2>#define uint1 unsigned<1>// db over shm memory testdeclare database shmdb; //数据名字compact class MyClass //表名字{unsigned<4> id;string str1;char<20> str2;unique tree<id> pkey; //索引};3、用host in目录里的mcocomp.exe程序在DOS命令行模式下将test.mco编译生成，用法如：》mcocomp test.mco编译成功后将会生成shmdb.h和shmdb.c文件。

当然了，可以根据需要生成所需的文件，具体请见mcocomp命令的参数(mcocomp -help)。

至此，生成的文件里就含有数据库操作所需要API函数了。

4、新建一控制台程序工程为shmdb，在链接库里加上mcolib_shm.lib（此处为共享内存LIB库），此处需要注意LIB的路径，最简单的办法就是将eXtremeDB的库文件拷贝至工程目录下包含其就可以了。

5、将编译生成的shmdb.h和shmdb.c添加至此工程中。

然后新建一C文件shmdemo.c（当然了，也可以是.cpp文件），下面将分别讲解shmdemo.c文件代码。

先看此文件的全部代码：/*标准库*/#include <ctype.h> /*ctype.h*/#include <stdlib.h> /*stdlib.h*/#include <stdio.h> /*stdio.h*/#include <string.h> /*string.h*/#include "shmdb.h" /*用mcocomp生成的shmdb.h文件*/const char * dbname = "demoShmDb"; //DB名称const int SEGSZ = 1024 * 1024 * 10; //10M大小的数据库const uint2 PAGESIZE = 90; //页面大小const int MAP_ADDRESS = 0x20000000; //内存地址void SH(void) {char text[] = {"This sample demonstrates eXtremeDB shared memory interfaces"};char text1[] = {"Copyright (c) 2001-2005 McObject LLC. All Right Reserved."};printf("%seXtremeDB runtime version %d.%d, build %d%sPress Enter to start",text, MCO_COMP_VER_MAJOR, MCO_COMP_VER_MINOR, MCO_COMP_BUILD_NUM,text1); getchar();}static int askNumber(const char *prompt) {char buf[300];printf("%s ", prompt);fgets(buf, sizeof (buf), stdin);if(isdigit(buf[0]))return atoi(buf);return -1;}/*16进制转换成10进制*/static int hex2num(const char *s) { unsigned int a = 0;while(*s) {int n;if( *s >= '0' && *s <= '9' )n = *s - '0';else if( *s >='a' && *s <= 'f')n = *s - 'a' + 10;else if( *s >='A' && *s <= 'F')n = *s - 'A' + 10;else return a;a = (a << 4) | n;s++;}return a;}static int askHex(const char *prompt) { char buf[300];printf("%s ", prompt);fgets(buf, sizeof (buf), stdin);return hex2num(buf);}/*插入记录*/static void insertRec(mco_db_h db) { MyClass c;MCO_RET rc;mco_trans_h t;int id;char str1[100], str2[100];id = askNumber("Enter new record's id:";mco_trans_start( db, MCO_READ_WRITE, MCO_TRANS_FOREGROUND,&t ); //事务startMyClass_new(t, &c); //新建一条记录sprintf(str1,"String1: %d", id);sprintf(str2,"String2: %d", id);MyClass_id_put(&c,(uint4)id); //插入MyClass_str1_put(&c, str1, (uint2)strlen(str1) );MyClass_str2_put(&c, str2, (uint2)strlen(str2) );rc = mco_trans_commit(t); //事务commitif(rc==MCO_S_OK)printf("insert done for %d (%s, %s)",(int)id,str1,str2);elseprintf("insert failed (%d) for %d (%s, %s)",rc,(int)id,str1,str2);}/*删除记录*/static void deleteRec(mco_db_h db) {MyClass c;MCO_RET rc;mco_trans_h t;int id;char str1[100]= {0}, str2[100]= {0};id = askNumber("deleting record, Enter record's id:";mco_trans_start( db, MCO_READ_WRITE, MCO_TRANS_FOREGROUND, &t ); rc = MyClass_pkey_find(t, (uint4)id, &c); //通过索引查找idif(rc != MCO_S_OK) {printf("Record with id = %d not found", (int)id);mco_trans_rollback(t); //如果没有找到回滚return;}MyClass_str1_get(&c,str1,(uint2)sizeof(str1),0);MyClass_str2_get(&c,str2,(uint2)sizeof(str2) );rc = MyClass_delete(&c);if(rc == MCO_S_OK)rc = mco_trans_commit(t);elsemco_trans_rollback(t);if(rc==MCO_S_OK)printf("delete done for %d (%s, %s)",id,str1,str2);elseprintf("delete failed (%d) for %d (%s, %s)",rc,id,str1,str2);}/*查找记录*/static void searchRec(mco_db_h db) {MyClass c;MCO_RET rc;mco_trans_h t;int id;char str1[100]= {0}, str2[100]= {0};id = askNumber("searching record, Enter record's id:";mco_trans_start( db, MCO_READ_ONLY, MCO_TRANS_FOREGROUND, &t ); rc = MyClass_pkey_find(t, (uint4)id, &c); //通过索引查找idif(rc != MCO_S_OK) {printf("Record with id = %d not found", id);mco_trans_rollback(t);return;}MyClass_str1_get(&c,str1,(uint2)sizeof(str1),0);MyClass_str2_get(&c,str2,(uint2)sizeof(str2) );mco_trans_rollback(t);printf("record found: %d (%s, %s)",id,str1,str2);}/*显示数据库中的记录信息*/static void listRecs(mco_db_h db) {MyClass c;MCO_RET rc;mco_trans_h t;uint4 id;char str1[100]= {0}, str2[100]= {0};mco_cursor_t csr;mco_trans_start( db, MCO_READ_ONLY, MCO_TRANS_FOREGROUND, &t ); /*用游标的方法遍历数据*/MyClass_pkey_index_cursor( t, & csr );rc = mco_cursor_first(t, &csr); //置游标为第一条记录printf("----------- All records of type MyClass: --------" );/*遍历数据库*/for( ; rc == MCO_S_OK; rc = mco_cursor_next(t, &csr) ) {rc = MyClass_from_cursor(t, &csr, &c);if(rc) {printf("Unexpected error %d",rc); break;}MyClass_id_get(&c, &id);MyClass_str1_get(&c,str1,(uint2)sizeof(str1),0);MyClass_str2_get(&c,str2,(uint2)sizeof(str2) );printf("record: %7d (%s, %s)",(int)id,str1,str2);}printf( "------------------------ end of list ------------";mco_trans_rollback(t);}/*数据库操作选择*/static void menu( mco_db_h db ) {char ibuf[300];int ch; // menu choicefor(;{printf("----------------------------Menu:""0: exit""1: insert a record""2: delete a record""3: search a record""4: list records""5: print db statistics""$ ");fgets(ibuf, sizeof (ibuf), stdin);if( ! isdigit( ibuf[0] ) )continue;ch = atoi(ibuf);switch(ch) {default:break;case 0:return;case 1:insertRec(db); break;case 2:deleteRec(db); break;case 3:searchRec(db); break;case 4:listRecs(db); break;case 5:{uint4 freepg, totalpg, nused;mco_db_free_pages (db, &freepg); //求数据库剩余空间大小mco_db_total_pages (db, &totalpg); //求数据库总大小nused = totalpg - freepg;printf("Memory:"" %dKb available, %dKb used",(int)(freepg * PAGESIZE / 1024), (int)(nused * PAGESIZE / 1024) ); //求最后大小需要乘以页面大小}break;}} // end for}/*出错处理*/static void errhandler( int n ) {printf( "eXtremeDB fatal error: %d", n );getchar();exit( -1 );}/*主程序*/int main( int na, char **aa) {MCO_RET rc;mco_db_h db; //数据库句柄void * start_mem = 0;char prompt[300], buf[100];mco_runtime_info_t info; //数据库信息SH();mco_get_runtime_info( &info); //获取可运行数据库信息if ( !info.mco_shm_supported ) { //是否有多线程支持printf("This program requires shared memory database runtime";exit(1);};mco_runtime_start(); //初始化运行环境/* set fatal error handler */mco_error_set_handler( &errhandler );printf("Would you like to create a new database [Y] or attach [N] -- [Y/N] ?" );fgets(buf, sizeof (buf), stdin);if(buf[0] == 'y' || buf[0] == 'Y') {sprintf(prompt,"Enter hint address (default is %x):",(int) MAP_ADDRESS );start_mem = (void*) askHex(prompt);if( start_mem == 0 )start_mem = (void*) MAP_ADDRESS;printf("SHM Map address is %x", (int) start_mem );/*创建数据库*//*MCO_RET mco_db_open( IN const char * dbname, IN mco_dictionary_h dict, IN void * mem, IN uint4 total_size, IN uint2 page_size)*//*参数: *//* dbname 要打开的数据库名。