c语言轻松实现Oracle中存储大文件（c 存大文件oracle）

C语言轻松实现Oracle中存储大文件

传统的关系型数据库在存储大型文件时表现并不出色，而Oracle数据库则可以轻松存储大文件。本文将介绍如何使用C语言轻松实现Oracle中存储大文件。

Oracle数据库支持以下两种存储大型文件的方式：

1. 通过BLOB（二进制大型对象）数据类型存储文件：BLOB是一种可以存储任意形式大型数据的数据库对象类型。它可以存储数据流（如音视频、PDF文档等）或图像数据（如JPG、PNG等）等。

2. 通过BFILE（二进制文件）数据类型存储文件：BFILE是Oracle中存储二进制文件的特殊数据类型。它是指一个数据库对象，存储在硬盘上。

下面是使用C语言存储BLOB类型文件的示例代码：

#include 
#include 
#include 
#define DATA_SIZE 1024

void checkerr(OCIError *errhp, sword status)
{
    text errbuf[512];
    sb4 errcode = 0;
 
    switch (status)
    {
        case OCI_SUCCESS:
            break;
        case OCI_SUCCESS_WITH_INFO:
            printf("Warning: %s\n", OCIErrorGet((dvoid *)errhp, (ub4)1, (text *)NULL, &errcode, errbuf, (ub4)sizeof(errbuf), OCI_HTYPE_ERROR));
            break;
        case OCI_NEED_DATA:
            printf("Warning: OCI_NEED_DATA\n");
            break;
        case OCI_NO_DATA:
            printf("Warning: OCI_NO_DATA\n");
            break;
        case OCI_ERROR:
            OCIErrorGet((dvoid *)errhp, (ub4)1, (text *)&errcode, errbuf, (ub4)sizeof(errbuf), OCI_HTYPE_ERROR);
            printf("Error - Code: %d, Message: %s\n", errcode, errbuf);
            exit(1);
            break;
        case OCI_INVALID_HANDLE:
            printf("Warning: OCI_INVALID_HANDLE\n");
            break;
        case OCI_STILL_EXECUTING:
            printf("Warning: OCI_STILL_EXECUTE\n");
            break;
        case OCI_CONTINUE:
            printf("Warning: OCI_CONTINUE\n");
            break;
        default:
            break;
    }
}
int mn(int argc, char *argv[])
{
    OCIEnv *envhp = NULL;
    OCIServer *srvhp = NULL;
    OCIError *errhp = NULL;
    OCISession *authp = NULL;
    OCIStmt *stmthp = NULL;
    OCILobLocator *lobp = NULL;
    OCILobLocator *lobLen = NULL;

    oratext *username = (oratext *) "username";
    oratext *password = (oratext *) "password";
    oratext *dbname = (oratext *) "dbname";
    oratext *tblname = (oratext *) "tblname";
    char * filename = "test.png";

    ub4 stmttype = OCI_STMT_SELECT;
    ub4 mode = OCI_DEFAULT;
    ub4 prefetchrows = 1;

    OCILogon2(envhp, errhp, &authp, username, strlen(username), password, strlen(password), dbname, strlen(dbname), OCI_DEFAULT);

    OCIHandleAlloc((dvoid *) envhp, (dvoid **) &srvhp, OCI_HTYPE_SERVER, (size_t) 0, (dvoid **) 0);
    checkerr(errhp, OCIHandleAlloc((dvoid *) envhp, (dvoid **) &srvhp, OCI_HTYPE_SERVER, (size_t) 0, (dvoid **) 0));
    checkerr(errhp, OCIServerAttach(srvhp, errhp, (text *) dbname, strlen(dbname), OCI_DEFAULT));

    OCIHandleAlloc(envhp, (void **)&stmthp, OCI_HTYPE_STMT, 0, NULL);
    checkerr(errhp, OCIStmtPrepare(stmthp, errhp, (text *) "select * from tablename", strlen("select * from tablename"), OCI_NTV_SYNTAX, OCI_DEFAULT));
    if (OCIDefineByPos(stmthp, &defhp, errhp, 1, (dvoid *) &lobp, -1, SQLT_BLOB, (dvoid *) 0, (ub2 *) 0, (ub2 *) 0, OCI_DEFAULT) != OCI_SUCCESS)
    {
        printf("OCIDefineByPos fled\n");
        exit(1);
    }

    checkerr(errhp, OCILogon2(envhp, errhp, &authp, username, strlen(username), password, strlen(password), dbname, strlen(dbname), OCI_DEFAULT));

    if (OCIStmtExecute(srvhp, stmthp, errhp, (ub4)1, (ub4)0, (OCISnapshot *)NULL, (OCISnapshot *)NULL, OCI_DEFAULT) != OCI_SUCCESS) {
        printf("OCIStmtExecute fled\n");
        exit(1);
    }
    FILE *pFile = fopen(filename, "rb");
    fseek(pFile, 0, SEEK_END);
    int file_size = ftell(pFile);
    fseek(pFile, 0, SEEK_SET);
    char * pBuf = (char *) malloc(file_size);
    fread(pBuf, 1, file_size, pFile);
    fclose(pFile);

    checkerr(errhp, OCILobCreateTemporary(srvhp, errhp, &lobp, OCI_DEFAULT, SQLT_BLOB, TRUE, OCI_DURATION_SESSION));
    checkerr(errhp, OCILobWrite(srvhp, errhp, lobp, &file_size, 1, (dvoid *)pBuf, (file_size > DATA_SIZE) ? DATA_SIZE : file_size, OCI_ONE_PIECE, (dvoid *)0, (sb4 (*)(void *, const void *, ub4, ub1)) 0, 0, SQLCS_IMPLICIT));
    free(pBuf);

    checkerr(errhp, OCIStmtPrepare(stmthp, errhp, (text *)"insert into tblname(blob_col) values (:1)", strlen("insert into tblname(blob_col) values (:1)"), OCI_NTV_SYNTAX, OCI_DEFAULT));

    if (OCIBindByPos(stmthp, &bndhp, errhp, (ub4) 1, (dvoid *) &lobp, sizeof(OCILobLocator *), SQLT_BLOB, (dvoid *)0, (ub2 *)0, (ub2 *)0, (ub4)0, 0, OCI_DEFAULT) != OCI_SUCCESS)
    {
        printf("OCIBindByPos fled\n");
        exit(1);
    }

    OCITransCommit(srvhp, errhp, OCI_DEFAULT);

    OCILogoff(authp, envhp, errhp);

    OCIHandleFree(srvhp, OCI_HTYPE_SERVER);
    OCIHandleFree(stmthp, OCI_HTYPE_STMT);
    OCIHandleFree(errhp, OCI_HTYPE_ERROR);
    OCIHandleFree(envhp, OCI_HTYPE_ENV);
    printf("Finish storing BLOB in Oracle!\n");

    return 0;
}

上述代码完成了将本地test.png文件存储到Oracle的tablename表中的blob字段。

需要注意的是，在调用初始化连接函数的时候，需要注意传入的连接名称username、password和dbname都需要替换为自己的信息。

总结：

使用Oracle数据库存储大型文件可以避免数据丢失、备份快速等问题，同时Oracle数据库也提供了很多方便的API，方便我们进行使用，可以大大提高开发效率，减少出现问题的几率。