2002-12-10  Theodore A. Roth  <address@hidden>

	* libc/string/strstr.S:

Index: libc/string/strstr.S
===================================================================
RCS file: /cvsroot/avr-libc/avr-libc/libc/string/strstr.S,v
retrieving revision 1.3
diff -u -r1.3 strstr.S
--- libc/string/strstr.S	9 Sep 2002 22:22:39 -0000	1.3
+++ libc/string/strstr.S	10 Dec 2002 19:47:36 -0000
@@ -1,4 +1,4 @@
-/* Copyright (c) 2002, Jochen Pernsteiner
+/* Copyright (c) 2002, Philip Soeberg
    All rights reserved.
 
    Redistribution and use in source and binary forms, with or without
@@ -30,8 +30,8 @@
    strstr.S
    Search string contained in a string
 
-   Contributors:
-     Created by Jochen Pernsteiner <address@hidden>
+   Contributed by:
+     Philip Soeberg <address@hidden>
 */
 
 #include "macros.inc"
@@ -40,7 +40,12 @@
 #define s1_lo r24
 #define s2_hi r23
 #define s2_lo r22
-#define tmp r21
+
+#define chr1_lo r18     /* first char of str1 (updated in loop) */
+#define chr1_hi r19     /* second char of str1 (updated in loop) */
+#define chr2_lo r20     /* first char of str2 (updated in loop) */
+#define chr2_hi r21     /* second char of str2 (updated in loop) */
+
 #define ret_hi r25
 #define ret_lo r24
 
@@ -49,44 +54,76 @@
     \brief Locate a substring.
 
     The strstr() function finds the first occurrence of the substring \c s2
-    in the string <tt>s1</tt>.  The terminating `\0' characters are not
+    in the string <tt>s1</tt>.  The terminating '\0' characters are not
     compared.
 
     \returns The strstr() function returns a pointer to the beginning of the
-    substring, or NULL if the substring is not found.  */
+    substring, or NULL if the substring is not found. If \c s2 points to a
+    string of zero length, the function returns <tt>s1</tt>. */
 
 .text
 .global _U(strstr)
 .type _U(strstr), @function
 _U(strstr):
-        LOAD_X(s1_lo, s1_hi)
-        LOAD_Z(s2_lo, s2_hi)
-        ld tmp, Z+
-        tst tmp
-        breq .strstr_ret
-        clr ret_lo
-        clr ret_hi
-.strstr_loop:
-        ld __tmp_reg__, X+
-        tst __tmp_reg__
-        breq .strstr_ret0
-        cp __tmp_reg__, tmp
-        brne .strstr_loop
-        adiw ret_lo, 1
-        ld tmp, Z+
-        tst tmp
-        brne .strstr_loop
-        sub XL, ret_lo
-        sbc XH, ret_hi
-        mov ret_lo, XL
-        mov ret_hi, XH
-        ret
-.strstr_ret0:
-        clr ret_lo
-        clr ret_hi
+    ;; Store temp registers
+	push r18
+	push r19
+	push r20
+	push r21
+
+	LOAD_X(s1_lo, s1_hi)
+	LOAD_Z(s2_lo, s2_hi)
+	ld chr2_lo, Z+
+	tst chr2_lo             ; is str2 empty?
+	breq .strstr_empty_str2
+
+.strstr_findstart:
+	LOAD_Z(s2_lo, s2_hi)    ; reset Z pointer
+	ld chr2_lo, Z+          ; fetch first char
+
+.strstr_findstart_loop:         ; Find first char
+	ld chr1_lo, X+
+	tst chr1_lo             ; Is str1 @ end?
+	breq .strstr_no_match   ; then return
+	cp chr1_lo, chr2_lo     ; Is chr1 == chr2?
+
+	mov ret_lo, XL          ; store return value
+	mov ret_hi, XH
+
+	brne .strstr_findstart_loop  ; If, then start checking string
+
+.strstr_stringloop:
+	ld chr2_lo, Z+
+	tst chr2_lo
+	breq .strstr_match
+	ld chr1_lo, X
+	tst chr1_lo
+	breq .strstr_no_match
+	cp chr1_lo, chr2_lo
+	brne .strstr_findstart
+	adiw XL, 1              ; Increment X with one
+	rjmp .strstr_stringloop
+
+;; Empty str2 string, return str1 (ANSI mandated!)
+.strstr_empty_str2:
+	mov ret_lo, s1_lo
+	mov ret_hi, s1_hi
+	rjmp .strstr_ret
+
+.strstr_no_match:
+	clr ret_lo
+	clr ret_hi
+	rjmp .strstr_ret
+
+.strstr_match:
+	sbiw ret_lo, 1
+
 .strstr_ret:
-        ret
+	pop r21                 ; Restore temp register
+	pop r20
+	pop r19
+	pop r18
+	ret
 
 .strstr_end:
 .size _U(strstr), .strstr_end - _U(strstr)
-