映射C语言编码至Oracle类库中的实现（c oracle类库）

映射C语言编码至Oracle类库中的实现

Oracle是世界上最流行的企业级数据库之一，它提供了丰富的类库来支持各种编程语言，包括C语言。在使用Oracle类库时，需要将C语言编码映射到Oracle类库中，本文将介绍如何在C语言中实现这一过程。

Oracle提供了OCI（Oracle Call Interface）类库来支持C语言与Oracle数据库的交互。OCI类库是一组C语言接口，它提供了访问Oracle数据库的功能，在使用OCI类库时，需要先连接到Oracle数据库。下面是连接Oracle数据库的示例代码：

“`C

#include

int mn(){

OCIEnv *envhp;

OCIError *errhp;

OCIServer *srvhp;

OCISession *authp;

OCISvcCtx *svchp;

sword status;

OCIInitialize(OCI_THREADED, (dvoid *)0, (dvoid * (*)(dvoid *, size_t)) 0,

(dvoid * (*)(dvoid *, dvoid *, size_t))0, (void (*)(dvoid *, dvoid *))0 );

OCIEnvInit( &envhp, OCI_DEFAULT, (size_t) 0, (dvoid **) 0);

OCIHandleAlloc( (dvoid *) envhp, (dvoid **) &errhp, OCI_HTYPE_ERROR,

(size_t) 0, (dvoid **) 0);

status = OCIHandleAlloc( (dvoid *) envhp, (dvoid **) &srvhp, OCI_HTYPE_SERVER,

(size_t) 0, (dvoid **) 0);

status = OCIServerAttach( srvhp, errhp, (text *)”database_name”, strlen(“database_name”), OCI_DEFAULT);

status = OCIHandleAlloc( (dvoid *) envhp, (dvoid **) &svchp, OCI_HTYPE_SVCCTX,

(size_t) 0, (dvoid **) 0);

status = OCIAttrSet( (dvoid *) svchp, OCI_HTYPE_SVCCTX, (dvoid *) srvhp, (ub4) 0, OCI_ATTR_SERVER, errhp);

OCIHandleAlloc( (dvoid *) envhp, (dvoid **) &authp, (ub4) OCI_HTYPE_SESSION,

(size_t) 0, (dvoid **) 0);

OCIAttrSet( (dvoid *) authp, (ub4) OCI_HTYPE_SESSION, (dvoid *)”username”,

(ub4) strlen(“username”), OCI_ATTR_USERNAME, errhp);

OCIAttrSet( (dvoid *) authp, (ub4) OCI_HTYPE_SESSION, (dvoid *)”password”,

(ub4) strlen(“password”), OCI_ATTR_PASSWORD, errhp);

status = OCISessionBegin ( svchp, errhp, authp, OCI_CRED_RDBMS, OCI_DEFAULT);

status = OCIAttrSet((dvoid*)svchp, OCI_HTYPE_SVCCTX, (dvoid*)authp, 0, OCI_ATTR_SESSION, errhp);

status = OCIHandleFree((dvoid *) authp, OCI_HTYPE_SESSION);

return 0;

}

在连接Oracle数据库之后，需要将C语言的变量映射到Oracle类库中的变量。OCI类库提供了一些类型映射函数，可以将C语言中的类型转换为Oracle类库中相应的类型。下面是一个将C语言整型变量映射到Oracle类库中的变量的示例：

```C
#include 
 
int mn(){
 
    OCIEnv *envhp;
    OCIError *errhp;
    OCIServer *srvhp;
    OCISession *authp;
    OCISvcCtx *svchp;
    sword status;
 
    OCIInitialize(OCI_THREADED, (dvoid *)0, (dvoid * (*)(dvoid *, size_t)) 0,
                  (dvoid * (*)(dvoid *, dvoid *, size_t))0,  (void (*)(dvoid *, dvoid *))0 );
 
    OCIEnvInit( &envhp, OCI_DEFAULT, (size_t) 0, (dvoid **) 0);
    OCIHandleAlloc( (dvoid *) envhp, (dvoid **) &errhp, OCI_HTYPE_ERROR,
                     (size_t) 0, (dvoid **) 0);
    status = OCIHandleAlloc( (dvoid *) envhp, (dvoid **) &srvhp, OCI_HTYPE_SERVER,
                              (size_t) 0, (dvoid **) 0);
 
    status = OCIServerAttach( srvhp, errhp, (text *)"database_name", strlen("database_name"), OCI_DEFAULT);
 
    status = OCIHandleAlloc( (dvoid *) envhp, (dvoid **) &svchp, OCI_HTYPE_SVCCTX,
                              (size_t) 0, (dvoid **) 0);
 
    status = OCIAttrSet( (dvoid *) svchp, OCI_HTYPE_SVCCTX, (dvoid *) srvhp, (ub4) 0, OCI_ATTR_SERVER, errhp);
 
    OCIHandleAlloc( (dvoid *) envhp, (dvoid **) &authp, (ub4) OCI_HTYPE_SESSION,
                     (size_t) 0, (dvoid **) 0);
 
    OCIAttrSet( (dvoid *) authp, (ub4) OCI_HTYPE_SESSION, (dvoid *)"username", 
                (ub4) strlen("username"), OCI_ATTR_USERNAME, errhp);
    OCIAttrSet( (dvoid *) authp, (ub4) OCI_HTYPE_SESSION, (dvoid *)"password",  
                (ub4) strlen("password"), OCI_ATTR_PASSWORD, errhp);
 
    status = OCISessionBegin ( svchp,  errhp, authp, OCI_CRED_RDBMS, OCI_DEFAULT);
 
    status = OCIAttrSet((dvoid*)svchp, OCI_HTYPE_SVCCTX, (dvoid*)authp, 0, OCI_ATTR_SESSION, errhp);
 
    int c_int_ = 42;
    OCINumber oci_int_numb;
 
    OCINumberFromInt((OCIError *) errhp, (dvoid *) &c_int_, sizeof(c_int_), OCI_NUMBER_SIGNED, (OCINumber *) &oci_int_numb);
 
    return 0;
}

在以上示例中，使用了OCINumberFromInt函数将C语言整型变量42映射到OCI类库中。OCINumberFromInt函数将C语言整型变量转换为OCINumber类型。OCINumber类型是Oracle类库中表示数字的一种类型。在使用oci_int_numb变量时，需要使用OCI类型映射函数将OCINumber类型转换为C语言类型，如下所示：

“`C

int c_int_;

OCINumberToInt((OCIError *) errhp, (const OCINumber *) &oci_int_numb, sizeof(c_int_), OCI_NUMBER_SIGNED, (void *) &c_int_);

printf(“%d\n”, c_int_);

OCI类库提供了丰富的类型映射函数，包括将布尔值、字符数组、日期时间等类型映射到Oracle类库中的类型。在使用OCI类库时，可以根据具体需求选择合适的类型映射函数。

本文介绍了在C语言中将变量映射到Oracle类库中的实现。通过使用OCI类库提供的类型映射函数，可以方便地将C语言编码映射到Oracle类库中，实现与Oracle数据库的交互。