c - 一个C cgi脚本，用于从sqlite3_column_blob指针提供二进制文件

Question

我从sqlite数据库检索了二进制数据，现在我有了指向二进制数据（sqlite3_column_blob）的指针。如何使用C cgi脚本将此数据输出到客户端？

char *sql = "SELECT Data FROM Images WHERE Id = 1";

sqlite3_stmt *pStmt;
rc = sqlite3_prepare_v2(db, sql, -1, &pStmt, 0);

if (rc != SQLITE_OK ) {

    fprintf(stderr, "Failed to prepare statement\n");
    fprintf(stderr, "Cannot open database: %s\n", sqlite3_errmsg(db));

    sqlite3_close(db);

    return 1;
} 

rc = sqlite3_step(pStmt);

int bytes = 0;

if (rc == SQLITE_ROW) {

    bytes = sqlite3_column_bytes(pStmt, 0);
}
// >>>>next row is function to save file but I want output binary data to client<<<<  
fwrite(sqlite3_column_blob(pStmt, 0), bytes, 1, fp);

Answer 1

好的，谢谢大家的支持。在我要查找的代码下面，只需将“ sqlite3_column_blob”发送到stdout ...就可以了！

int main(void) {
    sqlite3 *db;
    char *err_msg = 0;
    int rc = sqlite3_open("./test.db", &db);
    if (rc != SQLITE_OK) {
        // error opening the SQLite database, send an error message to
        // requesting application as plain text.
        fprintf(stdout, "%s", "Content-Type: text/plain;\n\n");
        fprintf(stdout, "Cannot open database: %s\n", sqlite3_errmsg(db));
        sqlite3_close(db);
        return 1;
    }

    char *sql = "SELECT Data FROM Images WHERE Id = 1";
    sqlite3_stmt *pStmt;
    rc = sqlite3_prepare_v2(db, sql, -1, &pStmt, 0);
    if (rc != SQLITE_OK ) {
        // error with SQLite retrieving data, send an error message to
        // requesting application as plain text.
        fprintf(stdout, "%s", "Content-Type: text/plain;\n\n");
        fprintf(stdout, "Failed to prepare statement\n");
        fprintf(stdout, "Database error: %s\n", sqlite3_errmsg(db));
        sqlite3_close(db);
        return 1;
    }

    rc = sqlite3_step(pStmt);
    int bytes = 0;
    if (rc == SQLITE_ROW) {
        // send the content type HTTP response directive to requesting
        // application. the SQLite BLOB contains JPEG image data.
        fprintf(stdout, "%s", "Content-Type: image/jpeg;\n\n");
        bytes = sqlite3_column_bytes(pStmt, 0);
    }

    bytes = sqlite3_column_bytes(pStmt, 0);
    // send the image data from the SQLite BLOB to the requesting application
    fwrite(sqlite3_column_blob(pStmt, 0), bytes, 1, stdout);

    // cleanup and close SQLite connection and exit
    rc = sqlite3_finalize(pStmt);
    sqlite3_close(db);

    return 0;
}