1/* strncpy.s 4.2 84/11/01 */ 2 3/* 4 * Copy string s2 over top of string s1. 5 * Truncate or null-pad to n bytes. 6 * 7 * char * 8 * strncpy(s1, s2, n) 9 * char *s1, *s2; 10 */ 11#include "DEFS.h" 12 13ENTRY(strncpy, R6) 14 movl 12(ap),r6 # r6 = n 15 bleq done # n <= 0 16 movl 4(ap),r3 # r3 = s1 17 movl 8(ap),r1 # r1 = s2 181: 19 movzwl $65535,r2 # r2 = bytes in first chunk 20 cmpl r6,r2 # r2 = min(bytes in chunk, n); 21 jgeq 2f 22 movl r6,r2 232: 24 subl2 r2,r6 # update n 25 locc $0,r2,(r1) # '\0' found? 26 jneq 3f 27 subl2 r2,r1 # back up pointer updated by locc 28 movc3 r2,(r1),(r3) # copy in next piece 29 tstl r6 # run out of space? 30 jneq 1b 31 jbr done 323: # copy up to '\0' logic 33 addl2 r0,r6 # r6 = number of null-pad bytes 34 subl2 r0,r2 # r2 = number of bytes to move 35 subl2 r2,r1 # back up pointer updated by locc 36 movc3 r2,(r1),(r3) # copy in last piece 374: # null-pad logic 38 movzwl $65535,r2 # r2 = bytes in first chunk 39 cmpl r6,r2 # r2 = min(bytes in chunk, n); 40 jgeq 5f 41 movl r6,r2 425: 43 subl2 r2,r6 # update n 44 movc5 $0,(r3),$0,r2,(r3)# pad with '\0's 45 tstl r6 # finished padding? 46 jneq 4b 47done: 48 movl 4(ap),r0 # return s1 49 ret 50