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@@ -1,19 +1,107 @@
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+/*
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+ * Copyright (c) 1990 Regents of the University of California.
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+ * All rights reserved.
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+ *
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+ * Redistribution and use in source and binary forms, with or without
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+ * modification, are permitted provided that the following conditions
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+ * are met:
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+ * 1. Redistributions of source code must retain the above copyright
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+ * notice, this list of conditions and the following disclaimer.
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+ * 2. Redistributions in binary form must reproduce the above copyright
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+ * notice, this list of conditions and the following disclaimer in the
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+ * documentation and/or other materials provided with the distribution.
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+ * 3. [rescinded 22 July 1999]
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+ * 4. Neither the name of the University nor the names of its contributors
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+ * may be used to endorse or promote products derived from this software
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+ * without specific prior written permission.
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+ *
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+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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+ * SUCH DAMAGE.
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+ */
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+
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#include <stdlib.h>
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// Do not use register a5; callback function might need it.
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register long __tbl asm ("a5");
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-__ATTR_LIB_C__ void *bsearch(const void *key, const void *bptr, short n, short w, compare_t cmp_func)
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-{
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- unsigned short left=0,right=n-1,index;
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+/*
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+ * Perform a binary search.
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+ *
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+ * The code below is a bit sneaky. After a comparison fails, we
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+ * divide the work in half by moving either left or right. If lim
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+ * is odd, moving left simply involves halving lim: e.g., when lim
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+ * is 5 we look at item 2, so we change lim to 2 so that we will
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+ * look at items 0 & 1. If lim is even, the same applies. If lim
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+ * is odd, moving right again involves halving lim, this time moving
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+ * the base up one item past p: e.g., when lim is 5 we change base
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+ * to item 3 and make lim 2 so that we will look at items 3 and 4.
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+ * If lim is even, however, we have to shrink it by one before
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+ * halving: e.g., when lim is 4, we still looked at item 2, so we
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+ * have to make lim 3, then halve, obtaining 1, so that we will only
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+ * look at item 3.
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+ */
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+__ATTR_LIB_C__ void *bsearch(const void *key, const void *bptr, short n, short w, compare_t cmp_func);
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+asm("
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+ .text
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+ .even
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+ .globl bsearch
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+bsearch:
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+ movem.l %d3-%d5/%a2-%a4,-(%sp)
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+ move.l %a0,%d5 ;# key, key
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+ move.w %d1,%d4 ;# w, w
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+ move.l %a1,%a3 ;# bptr, base
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+ move.w %d0,%d3 ;# n, lim
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+ beq.s .L2 ;#
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+.L3:
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+ move.w %d3,%d0 ;# lim, tmp40
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+ lsr.w #1,%d0 ;#, tmp40
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+ mulu.w %d4,%d0 ;# w, tmp41
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+ lea 0(%a3,%d0.l),%a4 ;# base, tmp41, rptr
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+ move.l %a4,-(%sp) ;# rptr,
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+ move.l %d5,-(%sp) ;# key,
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+ jsr (%a2) ;#* cmp_func
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+ addq.l #8,%sp ;#,
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+ tst.w %d0 ;# rcmp
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+ beq.s .L4 ;#
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+ ble.s .L5 ;#
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+ lea 0(%a4,%d4.w),%a3 ;#, base
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+ subq.w #1,%d3 ;#, lim
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+.L5:
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+ lsr.w #1,%d3 ;#, lim
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+ bne.s .L3 ;#
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+.L2:
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+ suba.l %a4,%a4 ;# rptr
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+.L4:
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+ move.l %a4,%a0 ;# rptr, <result>
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+ movem.l (%sp)+,%d3-%d5/%a2-%a4
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+ rts
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+");
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+
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+// The assembly routine above was created using the following C code as a starting point:
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+/*{
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+ char *base = (char *)bptr;
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+ unsigned short lim;
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short rcmp;
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void *rptr;
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- do
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- {
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- index=(left+right)>>1;
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- if((rcmp=cmp_func(key,rptr=(char*)bptr+(long)index*(unsigned short)w))>0) left=index+1;
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- else if(rcmp<0) right=index-1;
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- else return rptr;
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- } while(left<=right);
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- return 0;
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-}
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+
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+ for (lim = n; lim != 0; lim >>= 1) {
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+ rptr = base + ((long)(lim >> 1) * (unsigned short)w);
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+ rcmp = cmp_func(key, rptr);
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+ if (rcmp == 0)
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+ return rptr;
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+ if (rcmp > 0) { // key > p: move right
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+ base = (char *)rptr + w;
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+ lim--;
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+ } // else move left
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+ }
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+ return NULL;
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+}*/
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