6.44 CString

Defined in namespace Smalltalk

Category: Language-C interface

Technically, CString is really a pointer to type char. However, it's so darn useful as a distinct datatype, and it is a separate datatype in Smalltalk, so we allow developers to express their semantics more precisely by using a more descriptive type.

In general, I behave like a cross between an array of characters and a pointer to a character. I provide the protocol for both data types. My #value method returns a Smalltalk String, as you would expect for a scalar datatype.

6.44.1 CString class: getting info		(class)
6.44.2 CString: accessing		(instance)
6.44.3 CString: pointer like behavior		(instance)

6.44.1 CString class: getting info

alignof

Answer the receiver's instances required aligment

scalarIndex

Private - Answer an index referring to the receiver's instances scalar type

sizeof

Answer the receiver's size

6.44.2 CString: accessing

alignof

Answer the receiver's required aligment

scalarIndex

Private - Answer an index referring to the receiver's scalar type

sizeof

Answer the receiver's size

6.44.3 CString: pointer like behavior

+ anInteger

Return another CString pointing at &receiver[anInteger] (or, if you prefer, what `receiver + anInteger' does in C).

- intOrPtr

If intOrPtr is an integer, return another CString pointing at &receiver[-anInteger] (or, if you prefer, what `receiver - anInteger' does in C). If it is a CString, return the difference in chars, i.e. in bytes, between the two pointed addresses (or, if you prefer, what `receiver - anotherCharPtr' does in C)

addressAt: anIndex

Access the string, returning a Smalltalk CChar corresponding to the given indexed element of the string. anIndex is zero-based, just like with all other C-style accessing.

at: anIndex

Access the string, returning the Smalltalk Character corresponding to the given indexed element of the string. anIndex is zero-based, just like with all other C-style accessing.

at: anIndex put: aCharacter

Store in the string a Smalltalk Character, at the given indexed element of the string. anIndex is zero-based, just like with all other C-style accessing.

decr

Adjust the pointer by one byte down (i.e. --receiver)

decrBy: anInteger

Adjust the pointer by anInteger bytes down (i.e. receiver -= anInteger). Note that, unlike #-, #decrBy: does not support passing another CString as its parameter, since neither C supports something like `charPtr -= anotherCharPtr'

deref

Access the string, returning the Smalltalk CChar corresponding to the first element of the string. This may not make much sense, but it resembles what `*string' does in C.

deref: aCChar

Access the string, setting the first element of the string to the value of the passed CChar. This may not make much sense, but it resembles what we get in C if we do *string = 's'.

incr

Adjust the pointer by one byte up (i.e. ++receiver)

incrBy: anInteger

Adjust the pointer by anInteger bytes up (i.e. receiver += anInteger)

replaceWith: aString

Overwrite memory starting at the receiver's address, with the contents of the Smalltalk String aString, null-terminating it. Ensure there is free space enough, or big trouble will hit you!