ZString

FreeBASIC

ZString
 
Standard data type: 8 bit character string

Syntax

Dim variable As ZString * size
Dim variable As ZString Ptr

Description

A ZString is a C-style fixed-size array of chars. It has no descriptor so its length is calculated faster to pass it as an argument to functions. When the variable has a fixed size, FreeBASIC avoids any overflow that could occur on assignment, by truncating the contents to a length of size - 1.

A ZString Ptr can point to a standard ZString, also can be used to implement an "user-managed" ZString, in this case Allocate/Reallocate/Deallocate must be used to size-resize-dispose it and is up to the user to avoid overflows .

The end of the string is marked by a null character (0 ASCII). This is automatically added by the FreeBASIC string handling functions. A null character will be appended when the string is created, and the length will be calculated by scanning the string for the first null character. A null character (e.g. Chr(0)) may never be contained in the text of a ZString or the rest of the string will be truncated.

In a ZString, Len returns the size of the contained string and SizeOf returns the space allocated to the ZString. SizeOf only works if the size is known by the compiler, i.e. a fixed-size ZString variable is passed directly, not as a dereferenced pointer or a ByRef function argument.

This type is provided for easy interfacing with C libraries and to also replace the fixed-length strings, that can't be managed through pointers. Any intrinsic string functions like Left will work with ZString's too, plus any string operator.

Example

Dim As ZString * 13 str1 => "hello, world"
Print str1
Print Len(str1)     'returns 12, the size of the string it contains 
Print SizeOf(str1)  'returns 13, the size of the variable


Dim As ZString Ptr str2
str2 = Allocate( 13 )
*str2 = "hello, world"
Print *str2
Print Len(*str2)     'returns 12, the size of the string it contains 


Dialect Differences

  • Not available in the -lang qb dialect unless referenced with the alias __Zstring.

Differences from QB

  • New to FreeBASIC

See also