NSMutableData

Inherits From: NSData : NSObject

Conforms To: NSCoding, NSCopying, NSMutableCopying (NSData) NSObject (NSObject)

Declared In: Foundation/NSData.h

Foundation/NSSerialization.h

Class Description

The NSMutableData class declares the programmatic interface to objects that contain modifiable data in the form of bytes. This class inherits all read-only access methods from its superclass, NSData, and declares only those methods that permit the modification of the data.

NSMutableData's two primitive methodsmutableBytes and setLength:provide the basis for all the other methods in its interface. The mutableBytes method returns a pointer for writing into the bytes contained in the mutable data object. setLength: allows you to truncate or extend the length of a mutable data object.

The appendBytes:length: and appendData: methods let you append bytes or the contents of another data object to a mutable data object. You can replace a range of bytes in a mutable data object with either zeroes (using the resetBytesInRange: method), or with different bytes (using the replaceBytesInRange:withBytes: method).

This class declares various serialization methods that enable architecture-independent serialization of arbitrary Objective C types.

Creating an NSMutableData Object

• + (id)allocWithZone:(NSZone *)zone Creates and returns an uninitialized mutable data object from zone.
• + (id)dataWithCapacity:(unsigned int)numBytes Creates and returns a mutable data object, initially allocating enough memory to hold numBytes bytes.
• + (id)dataWithLength:(unsigned int)length Creates and returns a mutable data object, giving it enough memory to hold length bytes. Fills the object with zeroes up to length.
• - (id)initWithCapacity:(unsigned int)capacity Initializes a newly allocated mutable data object, giving it enough memory to hold capacity bytes. Sets the length of the data object to 0.
• - (id)initWithLength:(unsigned int)length Initializes a newly allocated mutable data object, giving it enough memory to hold length bytes. Fills the object with zeroes up to length.

• - (void)increaseLengthBy:(unsigned int)extraLength Increases the length of a mutable data object by extraLength zero-filled bytes.
• - (void *)mutableBytes Returns a pointer to the bytes in a mutable data object, enabling you to modify the bytes.
• - (void)setLength:(unsigned int)length Extends or truncates the length of a mutable data object by length bytes. If the mutable data object is extended, the additional bytes are zero-filled.

• - (void)appendBytes:(const void *)bytes Appends length bytes to a mutable data object from length:(unsigned int)length the buffer bytes.
• - (void)appendData:(NSData *)other Appends the contents of the data object other to the receiver.

• - (void)replaceBytesInRange:(NSRange)aRange Replaces the receiver's bytes located in aRange with bytes. withBytes:(const void *)bytes Raises an NSRangeException if aRange is not within the range of the receiver's data.
• - (void)resetBytesInRange:(NSRange)aRange Replaces the receiver's bytes located in aRange with zeros. Raises an NSRangeException if aRange is not within the range of the receiver's data.

• - (void)serializeAlignedBytesLength:(unsigned int)length Prepares bytes for an appendBytes:length: invocation by serializing them. If the length of the bytes will cause extension past the page size, this method encodes header information, creating a hole so that all bytes in the data object are aligned on page boundaries.
• - (void)serializeDataAt:(const void *)data Serializes whatever data element is referenced by data, ofObjCType:(const char *)type interpreting it by the Objective C type specifier type. context: If the data element is an object other than an instance of (id <NSObjCTypeSerializationCallBack>)callback NSDictionary, NSArray, NSString, or NSData, further definition of the object can occur through a callback from object callback. All Objective C types are currently supported except unions and void *. Pointers refer to a single item.
• - (void)serializeInt:(int)value Serializes the integer value by encoding it as a character representation.
• - (void)serializeInt:(int)value Serializes the integer value by encoding it as a character atIndex:(unsigned int)index representation and replaces the encoded value at the specified index in the data.
• - (void)serializeInts:(int *)intBuffer Serializes numInts count of integers in intBuffer by count:(unsigned int)numInts encoding each integer as a character representation.
• - (void)serializeInts:(int *)intBuffer Serializes numInts count of integers in intBuffer by count:(unsigned int)numInts encoding each integer, starting at the specified atIndex:(unsigned int)index index, and replacing each corresponding integer encoding serially.