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string.rfind() is now romable and now works correctly on empty strings.

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added some comments to strings.pattern_match
This commit is contained in:
Irmen de Jong
2025-04-16 21:41:41 +02:00
parent 801fe1b604
commit 7108b74105
3 changed files with 53 additions and 29 deletions
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40
compiler/res/prog8lib/strings.p8
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@@ -10,6 +10,7 @@ strings {
; This value is determined during runtime and counts upto the first terminating 0 byte in the string,
; regardless of the size of the string during compilation time. Don’t confuse this with len and sizeof!
; uses P8ZP_SCRATCH_W1 to store the string address, do not change this, other routines here may depend on it (as optimization implementation detail)
%asm {{
sta P8ZP_SCRATCH_W1
sty P8ZP_SCRATCH_W1+1
@@ -153,17 +154,13 @@ _found tya
asmsub rfind(uword string @AY, ubyte character @X) -> ubyte @A, bool @Pc {
; Locates the first position of the given character in the string, starting from the right.
; returns Carry set if found + index in A, or Carry clear if not found (and A will be 255, an invalid index).
; TODO: Romable
%asm {{
stx P8ZP_SCRATCH_B1
sta _str
sty _str+1
; note: we make use of the fact that length() stores the string address AY in P8ZP_SCRATCH_W1 for us! we need that later
jsr length
cpy #0
beq _notfound
dey
lda _str
sta P8ZP_SCRATCH_W1
lda _str+1
sta P8ZP_SCRATCH_W1+1
- lda (P8ZP_SCRATCH_W1),y
cmp P8ZP_SCRATCH_B1
beq _found
@@ -176,9 +173,6 @@ _notfound lda #255
_found tya
sec
rts
_str .word 0 ; modified
; !notreached!
}}
}
@@ -322,17 +316,23 @@ _done rts
}
asmsub pattern_match(str string @AY, str pattern @R0) clobbers(Y) -> bool @A {
; This routine matches a string against a pattern and returns with the carry bit set if they match, or clear if they don't.
; The two characters ? and * have a special meaning when they appear in the pattern. All other characters match themselves.
; ? matches any one character. For example, F?? matches FOO but not FU, and ?? matches all two-character strings.
; * matches any string, including the empty string.
; For example, F* matches all strings starting with F. *O*O* matches all strings with at least two Os. Finally, ?* matches all non-empty strings.
; Both the pattern and the string must be NUL-terminated (that it, followed with a 00 byte) and at most 255 characters long (excluding the NUL).
; Code taken from http://6502.org/source/strings/patmatch.htm
;
; Input: cx16.r0: A NUL-terminated, <255-length pattern
; AY: A NUL-terminated, <255-length string
;
; Output: A = 1 if the string matches the pattern, A = 0 if not.
;
; Notes: Clobbers A, X, Y. Each * in the pattern uses 4 bytes of stack.
; Does not work in ROM due to self-modifying code.
%asm {{
; pattern matching of a string.
; Input: cx16.r0: A NUL-terminated, <255-length pattern
; AY: A NUL-terminated, <255-length string
;
; Output: A = 1 if the string matches the pattern, A = 0 if not.
;
; Notes: Clobbers A, X, Y. Each * in the pattern uses 4 bytes of stack.
;
; see http://6502.org/source/strings/patmatch.htm
; TODO: Romable (or skip it?)
strptr = P8ZP_SCRATCH_W1