The Art of SQL Server FILESTREAM - Red Gate Software

Chapter 3: Accessing FILESTREAM Data from Client Applications//Get a handle to the FILESTREAM data using OpenSqlFileStream APISQLCHAR transactionToken[32];SQLINTEGER cbTransactionToken = sizeof(transactionToken);HANDLE srcHandle = INVALID_HANDLE_VALUE;srcHandle = OpenSqlFilestream (dstFilePath, SQL_FILESTREAM_READ,SQL_FILESTREAM_OPEN_NONE , transactionToken,cbTransactionToken, 0);Listing 3-7:Using C++ to open a FILESTREAM data file for read access.The first parameter is the logical path to the FILESTREAM data file obtained from a callto the PathName() function. The second argument specifies file access mode. It can beone of SQL_FILESTREAM_READ, SQL_FILESTREAM_WRITE, or SQL_FILESTREAM_READWRITE (for read, write, and read/write operations respectively).The third parameter allows you to specify the file attributes and flags. These areadditional hints that tell the system about the usage pattern, and the system will usethis information to optimize caching and performance. In Listing 3-7 we have set it toSQL_FILESTREAM_OPEN_NONE which indicates that the file needs to be opened with nospecific flags.The fourth argument is the transaction context we retrieved, and the fifth specifies thesize (in bytes) of the transaction context buffer.The last argument allows you to specify the initial allocation size of the data file in bytes;this is ignored when the file is opened for read operation.See OpenSqlFilestream API Reference, later in this chapter, for a detailed discussion of thisAPI function.97