File Creation and read/write exercises

 

File Creation and read/write exercises

RFile can read and write a file. If a file with the same name already exists during file creation, an error will occur. You can use the replace method.

RFile is easy to use. Note that there are multiple read and write methods, which involve the conversion of 8-bit and 16-bit data. close () is required after use. The following is the practice code.

Void writeFile () { User: LeaveIfError (ifs. Connect ()); RFile file; _ Partition (KfileName, "c :\\ mytxtfile \ aaa.txt "); TBufC <20> filename (KfileName ); // RFs ifs; defined previously If (file. Create (ifs, filename, EFileWrite )! = KErrAlreadyExists) { _ LIT8 (KFileContent, "Test File write "); TBufC8 <20> bufc (KFileContent ); User: LeaveIfError (file. Write (KFileContent )); User: LeaveIfError (file. Flush ()); File. Close (); } // Read it after writing /* When reading data, convert it to 16-bit storage; otherwise, garbled characters are displayed. */ TBuf8 <4> aRead; TBuf <4> aread16; File. Open (ifs, filename, EFileRead ); _ Partition (KC, "% S \ n "); TInt I = 0; Do { ARead. Zero (); Aread16.Zero (); File. Read (I, aRead, 4 ); I + = 4; File. Seek (ESeekStart, I ); Aread16.Copy (aRead ); Console-> Printf (KC, & aread16 ); } While (aRead. Length ()! = 0 ); File. Close (); Ifs. Close (); }

For more information about RFile, see the SDK help.

Location:f32file.h Link against:efsrv.lib ClassRFile RFile Support Supported from 5.0 Description Creates and opens a file, and performs all operations on a single open file. These include: Reading from and writing to the file Seeking to a position within the file Locking and unlocking within the file Setting file attributes Before using any of these services, a connection to a file server session must have been made and the file must be open. Opening Files: UseOpen()To open an existing file for reading or writing-an error is returned if it does not already exist. To open an existing file for reading only, useOpen()With an access modeEFileReadAnd a share modeEFileShareReadersOnly. UseCreate()To create and open a new file for writing-an error is returned if it already exists. UseReplace()To open a file for writing, replacing any existing file of the same name if one exists or creating a new file if one does not exist, UseTemp()To create and open a temporary file with a unique name, for writing and reading. When opening a file, you must specify the file server session to use for operations with that file. if you do not close the file explicitly, it is closed when the server session associated with it is closed. Reading and Writing: There are several variants of bothRead()AndWrite(). The basicRead(TDes8& aDes)AndWrite(const TDesC8& aDes)Are supplemented by variants allowing the descriptor length to be overridden, or the seek position of the first byte to be specified, or asynchronous completion, or any combination. Reading transfers data from a file to a descriptor, and writing transfers data from a descriptor to a file. In all cases, the file data is treated as binary and byte descriptors are used (TDes8,TDesC8).   Derivation RSubSessionBase-Client-side handle to a sub-session RFsBase-Base class that provides a Close () function for file related clean-up RFile-Creates and opens a file, and performs all operations on a single open file Members Defined inRFile: Att(),ChangeMode(),Create(),Flush(),Lock(),Modified(),Open(),Read(),Read(),Read(),Read(),Read(),Read(),Read(),Read(),Rename(),Replace(),Seek(),Set(),SetAtt(),SetModified(),SetSize(),Size(),Temp(),UnLock(),Write(),Write(),Write(),Write(),Write(),Write(),Write(),Write() Inherited fromRFsBase: Close() Inherited fromRSubSessionBase: CloseSubSession(),CreateSubSession(),Send(),SendReceive(),SubSessionHandle(),operator=()

Anping 2009 @ original
Qi_jianzhou@126.com