File stream in objective c

Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Helping communities build their own LTE networks. Podcast Making Agile work for data science. Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Visit chat. Linked Related Here, if there is an exception in the call to fis. You can also swallow the exception on the output stream.

Some people prefer not to swallow output stream exceptions, and also flush before closing. Notice that the nested standard idiom does not need the checks for null, which are in there in this case to protect against the case when one of the allocations throws an exception, in which case one would get a NullPointerException.

When a resource allocation is included as an argument to a constructor, if the constructor fails it can leave an an unreachable resource that no one can close. In that case, no one will have a hold of the FileOutputStream and so no one will be able to close it. In such a case you need to move the allocation the FileOutputStream out of the nested position and name it, so you are able to close if anything goes wrong during execution of the GZIPOutputStream constructor.

The constructors for FileInputStream, FileOutputStream and RandomAccessFile throw FileNotFoundException, but these cases are not problematic in the sense that their arguments are not resources and so they do not cause the nested resource leak. Cursor is an interface, the actual resources are something like SQLiteCursor. So, every time you call a function that returns a Cursor object, there is an allocation.

For instance, in the functions from SQLiteDatabase query … and rawQuery … allocate a cursor resource. MediaStore and DownloadManager it is only query … Cursor objects cursor created by these functions need to be closed i. Similarly, JsonParser is an abstract class, and create a resource in functions from the class JsonFactory createParser byte[] data createParser byte[] data, int offset, int len createParser String content createParser URL url createParser File f JsonParser objects js created by these functions need to be closed jp.

On the other hand. This is because they receive the resource from somewhere that will maintain the responsibility to close it. Sometimes you want to return a resource to the outside, in which case you should not close it, but you still need to be careful of exceptions in case control skips past the return leaving no one to close. Here is a simple example of a positive use of escaping resources. In this case it is intended that an object that wraps stream is passed to the caller of createAttachment.

As a rule, the recommended way to establish a TCP connection to a remote host is with streams. Streams automatically handle many of the challenges that TCP connections present. Streams are also a more Cocoa-like networking interface than lower-level protocols, behaving in a way that is largely compatible with the Cocoa file stream APIs. The way you obtain input and output streams for a host depends on whether you used service discovery to discover the host:. After you have obtained your input and output streams, you should retain them immediately if you are not using automatic reference counting.

This method returns the number of bytes written or a negative number on error. If fewer bytes were written than you tried to send, you must queue up the remaining data and send it after the delegate method gets called again with an NSStreamEventHasSpaceAvailable event. If an error occurs, you should call streamError to find out what went wrong. This method returns the number of bytes read, or a negative number on error.

If fewer bytes were read than you need, you must queue the data and wait until you receive another stream event with additional data. When you read from that stream, you get a length of zero 0. When either of these two events occurs, the delegate method is responsible for detecting the end-of-file condition and cleaning up. By default, this closes the underlying socket connection. There are two situations in which you must close it yourself, however:.

By default, streams created from an existing native socket do not close their underlying socket. As mentioned previously, a server and a client are similar once the connection is established. The main difference is that clients make outgoing connections, whereas servers create a listening socket sometimes listen socket —a socket that listens for incoming connections—then accept connections on that socket.

After that, each resulting connection behaves just like a connection you might make in a client. The API you should choose for your server depends primarily on whether you are trying to share the code with other non-Mac, non-iOS platforms. Higher-level APIs cannot be used for accepting incoming connections. Provide a CFData object containing a sockaddr struct that specifies information about the desired port and family.

When you are through with the socket, you must close it by calling CFSocketInvalidate. In this case, the data parameter of the callback is a pointer to a CFSocketNativeHandle value an integer socket number representing the socket.

The stream-based APIs are strongly recommended. For more information, see CFSocket Reference. If no error description information is required, this argument may be set to NULL. Note that if the destination file path already exists this operation will fail. File copying can be achieved using the copyItemAtPath method.

As with the move method, this takes as arguments the source and destination pathnames and an optional NSError object. Success of the operation is indicated by the returned boolean value:.

The removeItemAtPath method removes the specified file from the file system. The method takes as arguments the pathname of the file to be removed and an optional NSError object. The success of the operation is, as usual, reported in the form of a boolean YES or NO return value:.

A symbolic link to a particular file may be created using the createSymbolicLinkAtPath method. This takes as arguments the path of the symbolic link, the path to the file to which the link is to refer and an optional NSError object.

The NSFileManager class includes some basic file reading and writing capabilities. Firstly, the contents of a file may be read and stored in an NSData object through the use of the contentsAtPath method:. Having stored the contents of a file in an NSData object, that data may subsequently be written out to a new file using the createFileAtPath method:. This, however, gives us no control over how much data is to be read or written and does not allow us to append data to the end of an existing file.

Clearly some more flexible mechanism is required. The NSFileHandle class provides a range of methods designed to provide a more advanced mechanism for working with files.

In addition to files, this class can also be used for working with devices and network sockets.