ChangeChar

Synopsis

nreplace = ChangeChar(string, len, fchar, rchar)
D0                    A0      D0   D1     D2

C Prototype

ULONG ChangeChar(STRPTR string, ULONG len, ULONG fchar, ULONG rchar);

Description

Searches for a character in a byte sequence, and when found, replaces it, continuing until it encounters the ASCII code 0 (null terminator). This is true if no length was passed in len; otherwise, the scan can be forced for a specific number of bytes.

Inputs

• string — Pointer to a string, not necessarily null-terminated.
• len — Number of characters to check. If NULL, the check ends when the ASCII code 0 is found.
• fchar — ASCII code to find. THIS MUST BE NON-ZERO IF len is NULL.
• rchar — ASCII code to substitute.

Result

• nreplace — Number of replacements made.

Notes

If you set fchar to ASCII code 0 (zero) and at the same time set len to NULL, the command will not perform any replacements. In this case, you must either provide a length or use FilterChars() first.

See Also

• FilterChars

Implementation

The original 68020 assembly implementation:

; (26-Nov-1994) --- ChangeChar()
_LVOChangeChar
        movem.l d0-d5/a0,-(sp)
        moveq   #0,d5
        move.w  d0,d4
        subq.w  #1,d4
 
CC_CMPtwo
        tst.w   d0
        bne.s   CC_CMP
 
CC_TestZero
        moveq   #1,d4
        tst.b   (a0)
        beq.s   CC_Exit
 
CC_CMP  move.b  (a0),d3
        cmp.b   d1,d3
        bne.s   CC_NoFind
        move.b  d2,(a0)
        addq.w  #1,d5
 
CC_NoFind
        addq.w  #1,a0
        dbf     d4,CC_CMPtwo
 
CC_Exit move.l  d5,(sp)
        movem.l (sp)+,d0-d5/a0
        move.l  d0,d0
        rts