| 文件strtest.c
1 #include <stdio.h>
2 extern void strcopy(char *d, const char *s);
3 int main()
4 { const char *srcstr = "First string - source";
5 char dststr[] = "Second string - destination";
6 /* dststr is an array since we're going to change it */
7
8 printf("Before copying:/n");
9 printf(" '%s'/n '%s'/n",srcstr,dststr);
10 strcopy(dststr,srcstr);
11 printf("After copying:/n");
12 printf(" '%s'/n '%s'/n",srcstr,dststr);
13 return 0;
14 }
文件scopy.s
1 AREA SCopy, CODE, READONLY
2 EXPORT strcopy
3 strcopy
4 ; r0 points to destination string
5 ; r1 points to source string
6 LDRB r2, [r1],#1 ; load byte and update address
7 STRB r2, [r0],#1 ; store byte and update address;
8 CMP r2, #0 ; check for zero terminator
9 BNE strcopy ; keep going if not
10 MOV pc,lr ; Return
11 END |