NSData Class Reference

Inherits from
Conforms to
Framework
/System/Library/Frameworks/Foundation.framework
Availability
Available in iOS 2.0 and later.
Declared in
NSData.h
Companion guides
Related sample code

Overview

NSData and its mutable subclass NSMutableData provide data objects, object-oriented wrappers for byte buffers. Data objects let simple allocated buffers (that is, data with no embedded pointers) take on the behavior of Foundation objects.

NSData creates static data objects, and NSMutableData creates dynamic data objects. NSData and NSMutableData are typically used for data storage and are also useful in Distributed Objects applications, where data contained in data objects can be copied or moved between applications.

The size of the data is subject to a theoretical limit of about 8 ExaBytes (in practice, the limit should not be a factor).

NSData is “toll-free bridged” with its Core Foundation counterpart, CFDataRef. See “Toll-Free Bridging” for more information on toll-free bridging.

Tasks

Creating Data Objects

Accessing Data

Base-64 Encoding

Testing Data

Storing Data

Class Methods

data

Creates and returns an empty data object.

+ (id)data
Return Value

An empty data object.

Discussion

This method is declared primarily for the use of mutable subclasses of NSData.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

dataWithBytes:length:

Creates and returns a data object containing a given number of bytes copied from a given buffer.

+ (id)dataWithBytes:(const void *)bytes length:(NSUInteger)length
Parameters
bytes

A buffer containing data for the new object.

length

The number of bytes to copy from bytes. This value must not exceed the length of bytes.

Return Value

A data object containing length bytes copied from the buffer bytes. Returns nil if the data object could not be created.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

dataWithBytesNoCopy:length:

Creates and returns a data object that holds length bytes from the buffer bytes.

+ (id)dataWithBytesNoCopy:(void *)bytes length:(NSUInteger)length
Parameters
bytes

A buffer containing data for the new object. bytes must point to a memory block allocated with malloc.

length

The number of bytes to hold from bytes. This value must not exceed the length of bytes.

Return Value

A data object that holds length bytes from the buffer bytes. Returns nil if the data object could not be created.

Discussion

The returned object takes ownership of the bytes pointer and frees it on deallocation. Therefore, bytes must point to a memory block allocated with malloc.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

dataWithBytesNoCopy:length:freeWhenDone:

Creates and returns a data object that holds a given number of bytes from a given buffer.

+ (id)dataWithBytesNoCopy:(void *)bytes length:(NSUInteger)length freeWhenDone:(BOOL)freeWhenDone
Parameters
bytes

A buffer containing data for the new object. If freeWhenDone is YES, bytes must point to a memory block allocated with malloc.

length

The number of bytes to hold from bytes. This value must not exceed the length of bytes.

freeWhenDone

If YES, the returned object takes ownership of the bytes pointer and frees it on deallocation.

Return Value

A data object that holds length bytes from the buffer bytes. Returns nil if the data object could not be created.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

dataWithContentsOfFile:

Creates and returns a data object by reading every byte from the file specified by a given path.

+ (id)dataWithContentsOfFile:(NSString *)path
Parameters
path

The absolute path of the file from which to read data.

Return Value

A data object by reading every byte from the file specified by path. Returns nil if the data object could not be created.

Discussion

This method is equivalent to dataWithContentsOfFile:options:error: with no options. If you need to know what was the reason for failure, use dataWithContentsOfFile:options:error:.

A sample using this method can be found in “Working With Binary Data”.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

dataWithContentsOfFile:options:error:

Creates and returns a data object by reading every byte from the file specified by a given path.

+ (id)dataWithContentsOfFile:(NSString *)path options:(NSDataReadingOptions)mask error:(NSError **)errorPtr
Parameters
path

The absolute path of the file from which to read data.

mask

A mask that specifies options for reading the data. Constant components are described in “NSDataReadingOptions”.

errorPtr

If an error occurs, upon return contains an NSError object that describes the problem.

Return Value

A data object by reading every byte from the file specified by path. Returns nil if the data object could not be created.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

dataWithContentsOfURL:

Returns a data object containing the data from the location specified by a given URL.

+ (id)dataWithContentsOfURL:(NSURL *)aURL
Parameters
aURL

The URL from which to read data.

Return Value

A data object containing the data from the location specified by aURL. Returns nil if the data object could not be created.

Discussion

This method is ideal for converting data:// URLs to NSData objects, and can also be used for reading short files synchronously. If you need to read potentially large files, use inputStreamWithURL: to open a stream, then read the file a piece at a time.

If you need to know the reason for failure, use dataWithContentsOfURL:options:error:.

Availability
  • Available in iOS 2.0 and later.
Related Sample Code
Declared In
NSData.h

dataWithContentsOfURL:options:error:

Creates and returns a data object containing the data from the location specified by aURL.

+ (id)dataWithContentsOfURL:(NSURL *)aURL options:(NSDataReadingOptions)mask error:(NSError **)errorPtr
Parameters
aURL

The URL from which to read data.

mask

A mask that specifies options for reading the data. Constant components are described in “NSDataReadingOptions”.

errorPtr

If there is an error reading in the data, upon return contains an NSError object that describes the problem.

Discussion

This method is ideal for converting data:// URLs to NSData objects, and can also be used for reading short files synchronously. If you need to read potentially large files, use inputStreamWithURL: to open a stream, then read the file a piece at a time.

Availability
  • Available in iOS 2.0 and later.
Related Sample Code
Declared In
NSData.h

dataWithData:

Creates and returns a data object containing the contents of another data object.

+ (id)dataWithData:(NSData *)aData
Parameters
aData

A data object.

Return Value

A data object containing the contents of aData. Returns nil if the data object could not be created.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

Instance Methods

base64EncodedDataWithOptions:

Create a Base-64, UTF-8 encoded NSData from the receiver's contents using the given options.

- (NSData *)base64EncodedDataWithOptions:(NSDataBase64EncodingOptions)options
Parameters
options

A mask that specifies options for Base-64 encoding the data. Possible values are given in “NSDataBase64EncodingOptions”.

Return Value

A Base-64, UTF-8 encoded data object.

Discussion

By default, no line endings are inserted.

If you specify one of the line length options (NSDataBase64Encoding64CharacterLineLength or NSDataBase64Encoding76CharacterLineLength) but don’t specify the kind of line ending to insert, the default line ending is Carriage Return + Line Feed.

Availability
  • Available in iOS 7.0 and later.
Declared In
NSData.h

base64EncodedStringWithOptions:

Create a Base-64 encoded NSString from the receiver's contents using the given options.

- (NSString *)base64EncodedStringWithOptions:(NSDataBase64EncodingOptions)options
Parameters
options

A mask that specifies options for Base-64 encoding the data. Possible values are given in “NSDataBase64EncodingOptions”.

Return Value

A Base-64 encoded string.

Discussion

By default, no line endings are inserted.

If you specify one of the line length options (NSDataBase64Encoding64CharacterLineLength or NSDataBase64Encoding76CharacterLineLength) but don’t specify the kind of line ending to insert, the default line ending is Carriage Return + Line Feed.

Availability
  • Available in iOS 7.0 and later.
Declared In
NSData.h

bytes

Returns a pointer to the receiver’s contents.

- (const void *)bytes
Return Value

A read-only pointer to the receiver’s contents.

Discussion

If the length of the receiver is 0, this method returns nil.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

description

Returns an NSString object that contains a hexadecimal representation of the receiver’s contents.

- (NSString *)description
Return Value

An NSString object that contains a hexadecimal representation of the receiver’s contents in NSData property list format.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

enumerateByteRangesUsingBlock:

Enumerate through each range of bytes in the data object using a block.

- (void)enumerateByteRangesUsingBlock:(void (^)(const void *bytes, NSRange byteRange, BOOL *stop))block
Parameters
block

The block to apply to byte ranges in the array.

The block takes three arguments:

bytes

The bytes for the current range.

byteRange

The range of the current data bytes.

stop

A reference to a Boolean value. The block can set the value to YES to stop further processing of the data. The stop argument is an out-only argument. You should only ever set this Boolean to YES within the Block.

Discussion

The enumeration block is called once for each contiguous region of memory in the receiver (once total for a contiguous NSData object), until either all bytes have been enumerated, or the stop parameter is set to YES.

Availability
  • Available in iOS 7.0 and later.
Declared In
NSData.h

getBytes:length:

Copies a number of bytes from the start of the receiver's data into a given buffer.

- (void)getBytes:(void *)buffer length:(NSUInteger)length
Parameters
buffer

A buffer into which to copy data.

length

The number of bytes from the start of the receiver's data to copy to buffer.

Discussion

The number of bytes copied is the smaller of the length parameter and the length of the data encapsulated in the object.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

getBytes:range:

Copies a range of bytes from the receiver’s data into a given buffer.

- (void)getBytes:(void *)buffer range:(NSRange)range
Parameters
buffer

A buffer into which to copy data.

range

The range of bytes in the receiver's data to copy to buffer. The range must lie within the range of bytes of the receiver's data.

Discussion

If range isn’t within the receiver’s range of bytes, an NSRangeException is raised.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

initWithBase64EncodedData:options:

Returns a data object initialized with the given Base-64 encoded data.

- (id)initWithBase64EncodedData:(NSData *)base64Data options:(NSDataBase64DecodingOptions)options
Parameters
base64Data

A Base-64, UTF-8 encoded data object.

options

A mask that specifies options for Base-64 decoding the data. Possible values are given in “NSDataBase64DecodingOptions”.

Return Value

A data object containing the Base-64 decoded data. Returns nil if the data object could not be decoded.

Discussion

The default implementation of this method will reject non-alphabet characters, including line break characters. To support different encodings and ignore non-alphabet characters, specify an options value of NSDataBase64DecodingIgnoreUnknownCharacters.

Availability
  • Available in iOS 7.0 and later.
Declared In
NSData.h

initWithBase64EncodedString:options:

Returns a data object initialized with the given Base-64 encoded string.

- (id)initWithBase64EncodedString:(NSString *)base64String options:(NSDataBase64DecodingOptions)options
Parameters
base64String

A Base-64 encoded string.

options

A mask that specifies options for Base-64 decoding the data. Possible values are given in “NSDataBase64DecodingOptions”.

Return Value

A data object built by Base-64 decoding the provided string. Returns nil if the data object could not be decoded.

Discussion

The default implementation of this method will reject non-alphabet characters, including line break characters. To support different encodings and ignore non-alphabet characters, specify an options value of NSDataBase64DecodingIgnoreUnknownCharacters.

Availability
  • Available in iOS 7.0 and later.
Declared In
NSData.h

initWithBytes:length:

Returns a data object initialized by adding to it a given number of bytes of data copied from a given buffer.

- (id)initWithBytes:(const void *)bytes length:(NSUInteger)length
Discussion

A data object initialized by adding to it length bytes of data copied from the buffer bytes. The returned object might be different than the original receiver.

Availability
  • Available in iOS 2.0 and later.
Related Sample Code
Declared In
NSData.h

initWithBytesNoCopy:length:

Returns a data object initialized by adding to it a given number of bytes of data from a given buffer.

- (id)initWithBytesNoCopy:(void *)bytes length:(NSUInteger)length
Parameters
bytes

A buffer containing data for the new object. bytes must point to a memory block allocated with malloc.

length

The number of bytes to hold from bytes. This value must not exceed the length of bytes.

Return Value

A data object initialized by adding to it length bytes of data from the buffer bytes. The returned object might be different than the original receiver.

Discussion

The returned object takes ownership of the bytes pointer and frees it on deallocation. Therefore, bytes must point to a memory block allocated with malloc.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

initWithBytesNoCopy:length:deallocator:

Returns a data object initialized by adding to it a given number of bytes of data from a given buffer, with a custom deallocator block.

- (id)initWithBytesNoCopy:(void *)bytes length:(NSUInteger)length deallocator:(void (^)(void *bytes, NSUInteger length))deallocator
Parameters
bytes

A buffer containing data for the new object.

length

The number of bytes to hold from bytes. This value must not exceed the length of bytes.

deallocator

A block to invoke when the resulting NSData object is deallocated.

Return Value

A data object initialized by adding to it length bytes of data from the buffer bytes. The returned object might be different than the original receiver.

Discussion

Use this method to define your own deallocation behavior for the data buffer you provide.

In order to avoid any inadvertent strong reference cycles, you should avoid capturing pointers to any objects that may in turn maintain strong references to the NSData object. This includes explicit references to self, and implicit references to self due to direct instance variable access. To make it easier to avoid these references, the deallocator block takes two parameters, a pointer to the buffer, and its length; you should always use these values instead of trying to use references from outside the block.

Availability
  • Available in iOS 7.0 and later.
Declared In
NSData.h

initWithBytesNoCopy:length:freeWhenDone:

Initializes a newly allocated data object by adding to it length bytes of data from the buffer bytes.

- (id)initWithBytesNoCopy:(void *)bytes length:(NSUInteger)length freeWhenDone:(BOOL)flag
Parameters
bytes

A buffer containing data for the new object. If flag is YES, bytes must point to a memory block allocated with malloc.

length

The number of bytes to hold from bytes. This value must not exceed the length of bytes.

flag

If YES, the returned object takes ownership of the bytes pointer and frees it on deallocation.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

initWithContentsOfFile:

Returns a data object initialized by reading into it the data from the file specified by a given path.

- (id)initWithContentsOfFile:(NSString *)path
Parameters
path

The absolute path of the file from which to read data.

Return Value

A data object initialized by reading into it the data from the file specified by path. The returned object might be different than the original receiver.

Discussion

This method is equivalent to initWithContentsOfFile:options:error: with no options.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

initWithContentsOfFile:options:error:

Returns a data object initialized by reading into it the data from the file specified by a given path.

- (id)initWithContentsOfFile:(NSString *)path options:(NSDataReadingOptions)mask error:(NSError **)errorPtr
Parameters
path

The absolute path of the file from which to read data.

mask

A mask that specifies options for reading the data. Constant components are described in “NSDataReadingOptions”.

errorPtr

If an error occurs, upon return contains an NSError object that describes the problem.

Return Value

A data object initialized by reading into it the data from the file specified by path. The returned object might be different than the original receiver.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

initWithContentsOfURL:

Initializes a newly allocated data object initialized with the data from the location specified by aURL.

- (id)initWithContentsOfURL:(NSURL *)aURL
Parameters
aURL

The URL from which to read data

Return Value

An NSData object initialized with the data from the location specified by aURL. The returned object might be different than the original receiver.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

initWithContentsOfURL:options:error:

Returns a data object initialized with the data from the location specified by a given URL.

- (id)initWithContentsOfURL:(NSURL *)aURL options:(NSDataReadingOptions)mask error:(NSError **)errorPtr
Parameters
aURL

The URL from which to read data.

mask

A mask that specifies options for reading the data. Constant components are described in “NSDataReadingOptions”.

errorPtr

If there is an error reading in the data, upon return contains an NSError object that describes the problem.

Return Value

A data object initialized with the data from the location specified by aURL. The returned object might be different than the original receiver.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

initWithData:

Returns a data object initialized with the contents of another data object.

- (id)initWithData:(NSData *)data
Parameters
data

A data object.

Return Value

A data object initialized with the contents data. The returned object might be different than the original receiver.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

isEqualToData:

Compares the receiving data object to otherData.

- (BOOL)isEqualToData:(NSData *)otherData
Parameters
otherData

The data object with which to compare the receiver.

Return Value

YES if the contents of otherData are equal to the contents of the receiver, otherwise NO.

Discussion

Two data objects are equal if they hold the same number of bytes, and if the bytes at the same position in the objects are the same.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

length

Returns the number of bytes contained in the receiver.

- (NSUInteger)length
Return Value

The number of bytes contained in the receiver.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

rangeOfData:options:range:

Finds and returns the range of the first occurrence of the given data, within the given range, subject to given options.

- (NSRange)rangeOfData:(NSData *)dataToFind options:(NSDataSearchOptions)mask range:(NSRange)searchRange
Parameters
dataToFind

The data for which to search. This value must not be nil.

Important: Raises an NSInvalidArgumentException if dataToFind is nil.

mask

A mask specifying search options. The “NSDataSearchOptions” options may be specified singly or by combining them with the C bitwise OR operator.

searchRange

The range within the receiver in which to search for dataToFind. If this range is not within the receiver’s range of bytes, an NSRangeException raised.

Return Value

An NSRange structure giving the location and length of dataToFind within searchRange, modulo the options in mask. The range returned is relative to the start of the searched data, not the passed-in search range. Returns {NSNotFound, 0} if dataToFind is not found or is empty (@"").

Availability
  • Available in iOS 4.0 and later.
Declared In
NSData.h

subdataWithRange:

Returns a data object containing the receiver’s bytes that fall within the limits specified by a given range.

- (NSData *)subdataWithRange:(NSRange)range
Parameters
range

The range in the receiver from which to get the data. The range must not exceed the bounds of the receiver.

Return Value

A data object containing the receiver’s bytes that fall within the limits specified by range. If range isn’t within the receiver’s range of bytes, raises NSRangeException.

Discussion

A sample using this method can be found in “Working With Binary Data”.

Availability
  • Available in iOS 2.0 and later.
Related Sample Code
Declared In
NSData.h

writeToFile:atomically:

Writes the bytes in the receiver to the file specified by a given path.

- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)flag
Parameters
path

The location to which to write the receiver's bytes. If path contains a tilde (~) character, you must expand it with stringByExpandingTildeInPath before invoking this method.

atomically

If YES, the data is written to a backup file, and then—assuming no errors occur—the backup file is renamed to the name specified by path; otherwise, the data is written directly to path.

Return Value

YES if the operation succeeds, otherwise NO.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

writeToFile:options:error:

Writes the bytes in the receiver to the file specified by a given path.

- (BOOL)writeToFile:(NSString *)path options:(NSDataWritingOptions)mask error:(NSError **)errorPtr
Parameters
path

The location to which to write the receiver's bytes.

mask

A mask that specifies options for writing the data. Constant components are described in “NSDataWritingOptions”.

errorPtr

If there is an error writing out the data, upon return contains an NSError object that describes the problem.

Return Value

YES if the operation succeeds, otherwise NO.

Availability
  • Available in iOS 2.0 and later.
Related Sample Code
Declared In
NSData.h

writeToURL:atomically:

Writes the bytes in the receiver to the location specified by aURL.

- (BOOL)writeToURL:(NSURL *)aURL atomically:(BOOL)atomically
Parameters
aURL

The location to which to write the receiver's bytes. Only file:// URLs are supported.

atomically

If YES, the data is written to a backup location, and then—assuming no errors occur—the backup location is renamed to the name specified by aURL; otherwise, the data is written directly to aURL. atomically is ignored if aURL is not of a type the supports atomic writes.

Return Value

YES if the operation succeeds, otherwise NO.

Discussion

Since at present only file:// URLs are supported, there is no difference between this method and writeToFile:atomically:, except for the type of the first argument.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

writeToURL:options:error:

Writes the bytes in the receiver to the location specified by a given URL.

- (BOOL)writeToURL:(NSURL *)aURL options:(NSDataWritingOptions)mask error:(NSError **)errorPtr
Parameters
aURL

The location to which to write the receiver's bytes.

mask

A mask that specifies options for writing the data. Constant components are described in “NSDataWritingOptions”.

errorPtr

If there is an error writing out the data, upon return contains an NSError object that describes the problem.

Return Value

YES if the operation succeeds, otherwise NO.

Discussion

Since at present only file:// URLs are supported, there is no difference between this method and writeToFile:options:error:, except for the type of the first argument.

Availability
  • Available in iOS 2.0 and later.
Declared In
NSData.h

Constants

NSDataReadingOptions

Options for methods used to read NSData objects.

enum {
   NSDataReadingMappedIfSafe = 1UL << 0,
   NSDataReadingUncached = 1UL << 1,
   NSDataReadingMappedAlways = 1UL << 3,
};
typedef NSUInteger NSDataReadingOptions;
Constants
NSDataReadingMappedIfSafe

A hint indicating the file should be mapped into virtual memory, if possible and safe.

Available in iOS 5.0 and later.

Declared in NSData.h.

NSDataReadingUncached

A hint indicating the file should not be stored in the file-system caches.

For data being read once and discarded, this option can improve performance.

Available in iOS 4.0 and later.

Declared in NSData.h.

NSDataReadingMappedAlways

Hint to map the file in if possible.

This takes precedence over NSDataReadingMappedIfSafe if both are given.

Available in iOS 5.0 and later.

Declared in NSData.h.

NSDataBase64EncodingOptions

Options for methods used to Base-64 encode data.

enum {
   NSDataBase64Encoding64CharacterLineLength = 1UL << 0,
   NSDataBase64Encoding76CharacterLineLength = 1UL << 1,
   NSDataBase64EncodingEndLineWithCarriageReturn = 1UL << 4,
   NSDataBase64EncodingEndLineWithLineFeed = 1UL << 5,
};
typedef NSUInteger NSDataBase64EncodingOptions;
Constants
NSDataBase64Encoding64CharacterLineLength

Set the maximum line length to 64 characters, after which a line ending is inserted.

Available in iOS 7.0 and later.

Declared in NSData.h.

NSDataBase64Encoding76CharacterLineLength

Set the maximum line length to 76 characters, after which a line ending is inserted.

Available in iOS 7.0 and later.

Declared in NSData.h.

NSDataBase64EncodingEndLineWithCarriageReturn

When a maximum line length is set, specify that the line ending to insert should include a carriage return.

Available in iOS 7.0 and later.

Declared in NSData.h.

NSDataBase64EncodingEndLineWithLineFeed

When a maximum line length is set, specify that the line ending to insert should include a line feed.

Available in iOS 7.0 and later.

Declared in NSData.h.

NSDataBase64DecodingOptions

Options to modify the decoding algorithm used to decode Base-64 encoded NSData objects.

enum {
   NSDataBase64DecodingIgnoreUnknownCharacters = 1UL << 0
};
typedef NSUInteger NSDataBase64DecodingOptions;
Constants
NSDataBase64DecodingIgnoreUnknownCharacters

Modify the decoding algorithm so that it ignores unknown non-Base-64 bytes, including line ending characters.

Available in iOS 7.0 and later.

Declared in NSData.h.

Legacy Reading Options

Deprecated names for reading options. Do not use these names, use the new replacements instead.

enum {
   NSDataReadingMapped = NSDataReadingMappedIfSafe,
   NSMappedRead = NSDataReadingMapped,
   NSUncachedRead = NSDataReadingUncached
};
Constants
NSDataReadingMapped

Deprecated name for NSDataReadingMappedIfSafe.

Available in iOS 4.0 and later.

Declared in NSData.h.

NSMappedRead

Deprecated name for NSDataReadingMapped.

Available in iOS 2.0 and later.

Declared in NSData.h.

NSUncachedRead

Deprecated name for NSDataReadingUncached.

Available in iOS 2.0 and later.

Declared in NSData.h.

NSDataWritingOptions

Options for methods used to write NSData objects.

enum {
   NSDataWritingAtomic = 1UL << 0,
   NSDataWritingWithoutOverwriting = 1UL << 1,
   NSDataWritingFileProtectionNone = 0x10000000,
   NSDataWritingFileProtectionComplete = 0x20000000,
   NSDataWritingFileProtectionCompleteUnlessOpen = 0x30000000,
   NSDataWritingFileProtectionCompleteUntilFirstUserAuthentication = 0x40000000,
   NSDataWritingFileProtectionMask = 0xf0000000,
};
typedef NSUInteger NSDataWritingOptions;
Constants
NSDataWritingAtomic

A hint to write data to an auxiliary file first and then exchange the files. This option is equivalent to using a write method taking the parameter atomically:YES.

Available in iOS 4.0 and later.

Declared in NSData.h.

NSDataWritingWithoutOverwriting

Hint to return prevent overwriting an existing file. Cannot be combined with NSDataWritingAtomic.

Available in iOS 6.0 and later.

Declared in NSData.h.

NSDataWritingFileProtectionNone

A hint to set the content protection attribute of the file when writing it out. In this case, the file is not stored in an encrypted format and may be accessed at boot time and while the device is unlocked.

Available in iOS 4.0 and later.

Declared in NSData.h.

NSDataWritingFileProtectionComplete

A hint to set the content protection attribute of the file when writing it out. In this case, the file is stored in an encrypted format and may be read from or written to only while the device is unlocked. At all other times, attempts to read and write the file result in failure.

Available in iOS 4.0 and later.

Declared in NSData.h.

NSDataWritingFileProtectionCompleteUnlessOpen

A hint to set the content protection attribute of the file when writing it out. In this case, the file cannot be opened for reading or writing when the device is locked, although new files can be created with this class. If one of these files is open when the device is locked, reading and writing are still allowed.

Available in iOS 5.0 and later.

Declared in NSData.h.

NSDataWritingFileProtectionCompleteUntilFirstUserAuthentication

A hint to set the content protection attribute of the file when writing it out. In this case, the file can be read or written to while the device is locked, but while it is booting up, they have protection equivalent to NSDataWritingFileProtectionComplete.

Available in iOS 5.0 and later.

Declared in NSData.h.

NSDataWritingFileProtectionMask

A mask to use when determining the file protection options assigned to the data.

Available in iOS 4.0 and later.

Declared in NSData.h.

Legacy Writing Options

Deprecated names for writing options. Do not use these names, use the new replacements instead.

enum {
   NSAtomicWrite = NSDataWritingAtomic
};
Constants
NSAtomicWrite

Deprecated name for NSDataWritingAtomic.

Available in iOS 2.0 and later.

Declared in NSData.h.

NSDataSearchOptions

Options for method used to search NSData objects. These options are used with the rangeOfData:options:range: method.

enum {
   NSDataSearchBackwards = 1UL << 0,
   NSDataSearchAnchored = 1UL << 1
};
typedef NSUInteger NSDataSearchOptions;
Constants
NSDataSearchBackwards

Search from the end of NSData object.

Available in iOS 4.0 and later.

Declared in NSData.h.

NSDataSearchAnchored

Search is limited to start (or end, if NSDataSearchBackwards) of NSData object.

This option performs searching only on bytes at the beginning or end of the range. No match at the beginning or end means nothing is found, even if a matching sequence of bytes occurs elsewhere in the data object.

Available in iOS 4.0 and later.

Declared in NSData.h.