1 /*- 2 * Copyright (c) 1990 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Mike Hibler and Chris Torek. 7 * 8 * %sccs.include.redist.c% 9 */ 10 11 #if defined(LIBC_SCCS) && !defined(lint) 12 static char sccsid[] = "@(#)memset.c 5.7 (Berkeley) 05/12/93"; 13 #endif /* LIBC_SCCS and not lint */ 14 15 #include <sys/types.h> 16 17 #include <limits.h> 18 #include <string.h> 19 20 #define wsize sizeof(u_int) 21 #define wmask (wsize - 1) 22 23 void * 24 memset(dst0, c0, length) 25 void *dst0; 26 register int c0; 27 register size_t length; 28 { 29 register size_t t; 30 register u_int c; 31 register char *dst; 32 33 dst = (char *)dst0; 34 /* 35 * If not enough words, just fill bytes. A length >= 2 words 36 * guarantees that at least one of them is `complete' after 37 * any necessary alignment. For instance: 38 * 39 * |-----------|-----------|-----------| 40 * |00|01|02|03|04|05|06|07|08|09|0A|00| 41 * ^---------------------^ 42 * dst dst+length-1 43 * 44 * but we use a minimum of 3 here since the overhead of the code 45 * to do word writes is substantial. 46 */ 47 if (length < 3 * wsize) { 48 while (length != 0) { 49 *dst++ = c0; 50 --length; 51 } 52 return (dst0); 53 } 54 55 if ((c = (u_char)c0) != 0) { /* Copy value into the word. */ 56 c = (c << 8) | c; /* u_int is 16 bits. */ 57 #if UINT_MAX > 65535 58 c = (c << 16) | c; /* u_int is 32 bits. */ 59 #endif 60 #if UINT_MAX > 0xffffffff /* GCC will bitch, otherwise. */ 61 c = (c << 32) | c; /* u_int is 64 bits. */ 62 #endif 63 } 64 65 /* Align destination by filling in bytes. */ 66 if ((t = (int)dst & wmask) != 0) { 67 t = wsize - t; 68 length -= t; 69 do { 70 *dst++ = c0; 71 } while (--t != 0); 72 } 73 74 /* Fill words. Length was >= 2*words so we know t >= 1 here. */ 75 t = length / wsize; 76 do { 77 *(u_int *)dst = c; 78 dst += wsize; 79 } while (--t != 0); 80 81 /* Mop up trailing bytes, if any. */ 82 t = length & wmask; 83 if (t != 0) 84 do { 85 *dst++ = c0; 86 } while (--t != 0); 87 return (dst0); 88 } 89