mirror of
https://github.com/cc65/cc65.git
synced 2024-12-24 11:31:31 +00:00
85 lines
2.1 KiB
ArmAsm
85 lines
2.1 KiB
ArmAsm
;
|
|
; Ullrich von Bassewitz, 2005-04-21
|
|
;
|
|
; Search the environment for a string.
|
|
;
|
|
|
|
.export searchenv, copyenvptr
|
|
.import __environ, __envcount
|
|
.import ptr1:zp, ptr2:zp, ptr3:zp
|
|
|
|
.code
|
|
|
|
;----------------------------------------------------------------------------
|
|
; searchenv:
|
|
;
|
|
; ptr1 must contain the string to search for. On exit, the N flag will tell
|
|
; if the entry was found, and X will contain the index of the environment
|
|
; string in the environment (a negative value if the entry was not found).
|
|
; On success, ptr3 will contain the entry and Y the offset of the '=' within
|
|
; the string.
|
|
|
|
.proc searchenv
|
|
|
|
; Copy the pointer to the environment to the zero page
|
|
|
|
jsr copyenvptr
|
|
|
|
; Loop over all environment entries trying to find the requested one.
|
|
|
|
ldx __envcount
|
|
@L0: dex
|
|
bmi @L9 ; Out of entries
|
|
|
|
; Since the maximum number of entries is 64, the index can only be 63, so
|
|
; the following shift cannot overflow and the carry is clear.
|
|
|
|
txa
|
|
asl a ; Mul by two for word access
|
|
tay
|
|
lda (ptr2),y
|
|
sta ptr3
|
|
iny
|
|
lda (ptr2),y
|
|
sta ptr3+1
|
|
|
|
; ptr1 points to name, ptr3 points to the next environment entry. Compare the
|
|
; two. The following loop limits the length of name to 255 bytes.
|
|
|
|
ldy #$00
|
|
@L1: lda (ptr1),y
|
|
beq @L2 ; Jump on end of name
|
|
cmp (ptr3),y
|
|
bne @L0 ; Next environment entry
|
|
iny
|
|
bne @L1
|
|
|
|
; End of name reached, check if the environment entry contains a '=' char
|
|
|
|
@L2: lda (ptr3),y
|
|
cmp #'='
|
|
bne @L0 ; Next environment entry
|
|
|
|
; Done. The function result is in X and the N flag is set correctly.
|
|
|
|
@L9: rts
|
|
|
|
.endproc
|
|
|
|
|
|
;----------------------------------------------------------------------------
|
|
; copyenvptr: Copy _environ to ptr2
|
|
;
|
|
|
|
.proc copyenvptr
|
|
|
|
lda __environ
|
|
sta ptr2
|
|
lda __environ+1
|
|
sta ptr2+1
|
|
rts
|
|
|
|
.endproc
|
|
|
|
|