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Diffstat (limited to 'sys/libkern/bcmp.c')
| -rw-r--r-- | sys/libkern/bcmp.c | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/sys/libkern/bcmp.c b/sys/libkern/bcmp.c new file mode 100644 index 0000000..7c09ce5 --- /dev/null +++ b/sys/libkern/bcmp.c @@ -0,0 +1,149 @@ +/* + * Copyright (c) 1987, 1993 + * The Regents of the University of California. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * $FreeBSD$ + */ + +#include <string.h> +#include <machine/endian.h> + +typedef const void *cvp; +typedef const unsigned char *ustring; +typedef unsigned long ul; +typedef const unsigned long *culp; + +/* + * bcmp -- vax cmpc3 instruction + */ +int +bcmp(b1, b2, length) + const void *b1, *b2; + register size_t length; +{ +#if BYTE_ORDER == LITTLE_ENDIAN + /* + * The following code is endian specific. Changing it from + * little-endian to big-endian is fairly trivial, but making + * it do both is more difficult. + * + * Note that this code will reference the entire longword which + * includes the final byte to compare. I don't believe this is + * a problem since AFAIK, objects are not protected at smaller + * than longword boundaries. + */ + int shl, shr, len = length; + ustring p1 = b1, p2 = b2; + ul va, vb; + + if (len == 0) + return (0); + + /* + * align p1 to a longword boundary + */ + while ((long)p1 & (sizeof(long) - 1)) { + if (*p1++ != *p2++) + return (1); + if (--len <= 0) + return (0); + } + + /* + * align p2 to longword boundary and calculate the shift required to + * align p1 and p2 + */ + shr = (long)p2 & (sizeof(long) - 1); + if (shr != 0) { + p2 -= shr; /* p2 now longword aligned */ + shr <<= 3; /* offset in bits */ + shl = (sizeof(long) << 3) - shr; + + va = *(culp)p2; + p2 += sizeof(long); + + while ((len -= sizeof(long)) >= 0) { + vb = *(culp)p2; + p2 += sizeof(long); + if (*(culp)p1 != (va >> shr | vb << shl)) + return (1); + p1 += sizeof(long); + va = vb; + } + /* + * At this point, len is between -sizeof(long) and -1, + * representing 0 .. sizeof(long)-1 bytes remaining. + */ + if (!(len += sizeof(long))) + return (0); + + len <<= 3; /* remaining length in bits */ + /* + * The following is similar to the `if' condition + * inside the above while loop. The ?: is necessary + * to avoid accessing the longword after the longword + * containing the last byte to be compared. + */ + return ((((va >> shr | ((shl < len) ? *(culp)p2 << shl : 0)) ^ + *(culp)p1) & ((1L << len) - 1)) != 0); + } else { + /* p1 and p2 have common alignment so no shifting needed */ + while ((len -= sizeof(long)) >= 0) { + if (*(culp)p1 != *(culp)p2) + return (1); + p1 += sizeof(long); + p2 += sizeof(long); + } + + /* + * At this point, len is between -sizeof(long) and -1, + * representing 0 .. sizeof(long)-1 bytes remaining. + */ + if (!(len += sizeof(long))) + return (0); + + return (((*(culp)p1 ^ *(culp)p2) + & ((1L << (len << 3)) - 1)) != 0); + } +#else + register char *p1, *p2; + + if (length == 0) + return(0); + p1 = (char *)b1; + p2 = (char *)b2; + do + if (*p1++ != *p2++) + break; + while (--length); + return(length); +#endif +} |
