Function

CFStringCreateMutableWithExternalCharactersNoCopy

Creates a CFMutableString object whose Unicode character buffer is controlled externally.

Declaration

CFMutableStringRef CFStringCreateMutableWithExternalCharactersNoCopy(CFAllocatorRef alloc, UniChar *chars, CFIndex numChars, CFIndex capacity, CFAllocatorRef externalCharactersAllocator);

Parameters

alloc

The allocator to use to allocate memory for the string. Pass NULL or kCFAllocatorDefault to use the current default allocator.

chars

The Unicode character buffer for the new CFMutableString. Before calling, create this buffer on the stack or heap and optionally initialize it with Unicode character data. Upon return, the created CFString object keeps its own copy of the pointer to this buffer. You may pass in NULL if there is no initial buffer being provided.

numChars

The number of characters initially in the Unicode buffer pointed to by chars.

capacity

The capacity of the external buffer (chars); that is, the maximum number of Unicode characters that can be stored. This value should be 0 if no initial buffer is provided.

externalCharactersAllocator

The allocator to use to reallocate the external buffer when editing takes place and for deallocating the buffer when string is deallocated. If the default allocator is suitable for these purposes, pass NULL. To manage the buffer yourself, pass

kCFAllocatorNull

.

Return Value

A new mutable string, or NULL if there was a problem creating the object. Ownership follows the The Create Rule.

Discussion

This function permits you to create a CFMutableString object whose backing store is an external Unicode character buffer—that is, a buffer that you control (or can control) entirely. This function allows you to take advantage of the features of CFString, particularly the CFMutableString functions that add and modify character data. But at the same time you can directly add, delete, modify, and examine the characters in the buffer. You can even replace the buffer entirely. If, however, you directly modify or replace the character buffer, you should inform the CFString object of this change with the CFStringSetExternalCharactersNoCopy function.

If you mutate the character contents with the CFString functions, and the buffer needs to be enlarged, the CFString object calls the allocation callbacks specified for the allocator externalCharactersAllocator, or

the default allocator

if kCFAllocatorNull is specified.

This function should be used in special circumstances where you want to create a CFString wrapper around an existing, potentially large UniChar buffer you own. Using this function causes the CFString object to forgo some of its internal optimizations, so it should be avoided in general use. That is, if you want to create a CFString object from a small UniChar buffer, and you don't need to continue owning the buffer, use one of the other creation functions (for instance CFStringCreateWithCharacters) instead.

See Also

CFMutableString Miscellaneous Functions

CFStringAppend

Appends the characters of a string to those of a CFMutableString object.

CFStringAppendCharacters

Appends a buffer of Unicode characters to the character contents of a CFMutableString object.

CFStringAppendCString

Appends a C string to the character contents of a CFMutableString object.

CFStringAppendFormat

Appends a formatted string to the character contents of a CFMutableString object.

CFStringAppendFormatAndArguments

Appends a formatted string to the character contents of a CFMutableString object.

CFStringAppendPascalString

Appends a Pascal string to the character contents of a CFMutableString object.

CFStringCapitalize

Changes the first character in each word of a string to uppercase (if it is a lowercase alphabetical character).

CFStringCreateMutable

Creates an empty CFMutableString object.

CFStringCreateMutableCopy

Creates a mutable copy of a string.

CFStringDelete

Deletes a range of characters in a string.

CFStringFindAndReplace

Replaces all occurrences of a substring within a given range.

CFStringFold

Folds a given string into the form specified by optional flags.

CFStringInsert

Inserts a string at a specified location in the character buffer of a CFMutableString object.

CFStringLowercase

Changes all uppercase alphabetical characters in a CFMutableString to lowercase.

CFStringNormalize

Normalizes the string into the specified form as described in Unicode Technical Report #15.

CFStringPad

Enlarges a string, padding it with specified characters, or truncates the string.

CFStringReplace

Replaces part of the character contents of a CFMutableString object with another string.

CFStringReplaceAll

Replaces all characters of a CFMutableString object with other characters.

CFStringSetExternalCharactersNoCopy

Notifies a CFMutableString object that its external backing store of Unicode characters has changed.

CFStringTransform

Perform in-place transliteration on a mutable string.

CFStringTrim

Trims a specified substring from the beginning and end of a CFMutableString object.

CFStringTrimWhitespace

Trims whitespace from the beginning and end of a CFMutableString object.

CFStringUppercase

Changes all lowercase alphabetical characters in a CFMutableString object to uppercase.