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32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
35 #include <sys/libkern.h>
36 #include <machine/endian.h>
38 typedef const void *cvp;
39 typedef const unsigned char *ustring;
40 typedef unsigned long ul;
41 typedef const unsigned long *culp;
44 * bcmp -- vax cmpc3 instruction
47 (bcmp)(const void *b1, const void *b2, size_t length)
49 #if BYTE_ORDER == LITTLE_ENDIAN
51 * The following code is endian specific. Changing it from
52 * little-endian to big-endian is fairly trivial, but making
53 * it do both is more difficult.
55 * Note that this code will reference the entire longword which
56 * includes the final byte to compare. I don't believe this is
57 * a problem since AFAIK, objects are not protected at smaller
58 * than longword boundaries.
60 int shl, shr, len = length;
61 ustring p1 = b1, p2 = b2;
68 * align p1 to a longword boundary
70 while ((long)p1 & (sizeof(long) - 1)) {
78 * align p2 to longword boundary and calculate the shift required to
81 shr = (long)p2 & (sizeof(long) - 1);
83 p2 -= shr; /* p2 now longword aligned */
84 shr <<= 3; /* offset in bits */
85 shl = (sizeof(long) << 3) - shr;
90 while ((len -= sizeof(long)) >= 0) {
93 if (*(culp)p1 != (va >> shr | vb << shl))
99 * At this point, len is between -sizeof(long) and -1,
100 * representing 0 .. sizeof(long)-1 bytes remaining.
102 if (!(len += sizeof(long)))
105 len <<= 3; /* remaining length in bits */
107 * The following is similar to the `if' condition
108 * inside the above while loop. The ?: is necessary
109 * to avoid accessing the longword after the longword
110 * containing the last byte to be compared.
112 return ((((va >> shr | ((shl < len) ? *(culp)p2 << shl : 0)) ^
113 *(culp)p1) & ((1L << len) - 1)) != 0);
115 /* p1 and p2 have common alignment so no shifting needed */
116 while ((len -= sizeof(long)) >= 0) {
117 if (*(culp)p1 != *(culp)p2)
124 * At this point, len is between -sizeof(long) and -1,
125 * representing 0 .. sizeof(long)-1 bytes remaining.
127 if (!(len += sizeof(long)))
130 return (((*(culp)p1 ^ *(culp)p2)
131 & ((1L << (len << 3)) - 1)) != 0);