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tigcclib: fix bsearch(), while making it 12 bytes smaller.
bsearch used to return garbage pointers when the key was not in the array.
While at it: add an example, reference it in the documentation of bsearch.

git-svn-id: file:///var/svn/tigccpp/trunk@1356 9552661e-59e3-4036-b4f2-dbe53926924f

debrouxl 14 years ago
parent
commit
066f784899

+ 100 - 12
tigcc/archive/bsearch.c

@@ -1,19 +1,107 @@
+/*
+ * Copyright (c) 1990 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. [rescinded 22 July 1999]
+ * 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.
+ */
+
 #include <stdlib.h>
 
 // Do not use register a5; callback function might need it.
 register long __tbl asm ("a5");
 
-__ATTR_LIB_C__ void *bsearch(const void *key, const void *bptr, short n, short w, compare_t cmp_func)
-{
-  unsigned short left=0,right=n-1,index;
+/*
+ * Perform a binary search.
+ *
+ * The code below is a bit sneaky.  After a comparison fails, we
+ * divide the work in half by moving either left or right. If lim
+ * is odd, moving left simply involves halving lim: e.g., when lim
+ * is 5 we look at item 2, so we change lim to 2 so that we will
+ * look at items 0 & 1.  If lim is even, the same applies.  If lim
+ * is odd, moving right again involves halving lim, this time moving
+ * the base up one item past p: e.g., when lim is 5 we change base
+ * to item 3 and make lim 2 so that we will look at items 3 and 4.
+ * If lim is even, however, we have to shrink it by one before
+ * halving: e.g., when lim is 4, we still looked at item 2, so we
+ * have to make lim 3, then halve, obtaining 1, so that we will only
+ * look at item 3.
+ */
+__ATTR_LIB_C__ void *bsearch(const void *key, const void *bptr, short n, short w, compare_t cmp_func);
+asm("
+	.text
+	.even
+	.globl	bsearch
+bsearch:
+	movem.l %d3-%d5/%a2-%a4,-(%sp)
+	move.l %a0,%d5	;# key, key
+	move.w %d1,%d4	;# w, w
+	move.l %a1,%a3	;# bptr, base
+	move.w %d0,%d3	;# n, lim
+	beq.s .L2	;#
+.L3:
+	move.w %d3,%d0	;# lim, tmp40
+	lsr.w #1,%d0	;#, tmp40
+	mulu.w %d4,%d0	;# w, tmp41
+	lea 0(%a3,%d0.l),%a4	;# base, tmp41, rptr
+	move.l %a4,-(%sp)	;# rptr,
+	move.l %d5,-(%sp)	;# key,
+	jsr (%a2)	;#* cmp_func
+	addq.l #8,%sp	;#,
+	tst.w %d0	;# rcmp
+	beq.s .L4	;#
+	ble.s .L5	;#
+	lea 0(%a4,%d4.w),%a3	;#, base
+	subq.w #1,%d3	;#, lim
+.L5:
+	lsr.w #1,%d3	;#, lim
+	bne.s .L3	;#
+.L2:
+	suba.l %a4,%a4	;# rptr
+.L4:
+	move.l %a4,%a0	;# rptr, <result>
+	movem.l (%sp)+,%d3-%d5/%a2-%a4
+	rts
+");
+
+// The assembly routine above was created using the following C code as a starting point:
+/*{
+  char *base = (char *)bptr;
+  unsigned short lim;
   short rcmp;
   void *rptr;
-  do
-    {
-      index=(left+right)>>1;
-      if((rcmp=cmp_func(key,rptr=(char*)bptr+(long)index*(unsigned short)w))>0) left=index+1;
-      else if(rcmp<0) right=index-1;
-      else return rptr;
-    } while(left<=right);
-  return 0;
-}
+
+  for (lim = n; lim != 0; lim >>= 1) {
+    rptr = base + ((long)(lim >> 1) * (unsigned short)w);
+    rcmp = cmp_func(key, rptr);
+    if (rcmp == 0)
+      return rptr;
+    if (rcmp > 0) {  // key > p: move right
+      base = (char *)rptr + w;
+      lim--;
+    } // else move left
+  }
+  return NULL;
+}*/

+ 2 - 0
tigcc/doc/System/Include/stdlib.h/bsearch.hsf

@@ -27,3 +27,5 @@ The comparison function compares each of the pointed-to items (*<I>elem1</I> and
 <LI>If *<I>elem1</I> == *<I>elem2</I>, <I>cmp_func</I> should return 0.</LI>
 <LI>If *<I>elem1</I> &gt; *<I>elem2</I>, <I>cmp_func</I> should return an integer &gt; 0.</LI>
 </UL>
+Here is a complete example of usage (called "Binary Search"):
+$$EXAMPLE(Binary Search.c)

+ 41 - 0
tigcc/examples/Binary Search.c

@@ -0,0 +1,41 @@
+// Search integer values using a binary search.
+
+#define USE_TI89              // Compile for TI-89
+#define USE_TI92PLUS          // Compile for TI-92 Plus
+#define USE_V200              // Compile for V200
+
+#define OPTIMIZE_ROM_CALLS
+#define MIN_AMS 100           // Compile for AMS 1.00 or higher
+#define SAVE_SCREEN           // Save/Restore LCD Contents
+
+#include <tigcclib.h>         // Include All Header Files
+
+// Comparison Function
+CALLBACK short int_comp(const void *a, const void *b)
+{
+  return (*(const short*)a) - (*(const short*)b);
+}
+
+// Main Function
+void _main(void)
+{
+  short list[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+  short i;
+  short font;
+  void *p;
+
+  font = FontGetSys();
+  FontSetSys(F_4x6);
+  clrscr ();
+  for (i = -1; i < 11; i++) {
+    p = bsearch (&i, list, sizeof(list)/sizeof(list[0]), sizeof (list[0]), int_comp);
+    if (p == NULL) {
+      printf ("%d not found\n", i);
+    }
+    else {
+      printf ("%d is at index %lu\n", i, ((void *)p - (void *)list)/sizeof(list[0]));
+    }
+  }
+  FontSetSys(font);
+  ngetchx ();
+}

+ 18 - 0
tigcc/examples/Binary Search.tpr

@@ -0,0 +1,18 @@
+[Settings]
+Archive=0
+Pack=0
+Packed Variable=
+Project Name=BinSrch
+GCC Switches=-Os -Wall -W -Wwrite-strings
+GNU Assembler Switches=
+Assembler Switches=-g -t
+GNU Linker Switches=
+Linker Switches=
+Debug Info=0
+Standard Library=1
+Command Line=
+Post-Build Process=
+
+[Included Files]
+C File 1=Binary Search.c
+

+ 1 - 0
tigcc/examples/build.sh

@@ -5,6 +5,7 @@ tprbuilder -q "Approximation Mode.tpr"; if [ $? -ne 0 ]; then echo FAILED buildi
 tprbuilder -q "Argument Test.tpr"; if [ $? -ne 0 ]; then echo FAILED building "\"Argument Test.tpr\""; fi
 tprbuilder -q "Basecode Parameters.tpr"; if [ $? -ne 0 ]; then echo FAILED building "\"Basecode Parameters.tpr\""; fi
 tprbuilder -q "Big Numbers.tpr"; if [ $? -ne 0 ]; then echo FAILED building "\"Big Numbers.tpr\""; fi
+tprbuilder -q "Binary Search.tpr"; if [ $? -ne 0 ]; then echo FAILED building "\"Binary Search.tpr\""; fi
 tprbuilder -q "Bitmap Test.tpr"; if [ $? -ne 0 ]; then echo FAILED building "\"Bitmap Test.tpr\""; fi
 tprbuilder -q "Catalog.tpr"; if [ $? -ne 0 ]; then echo FAILED building "\"Catalog.tpr\""; fi
 tprbuilder -q "Cave Blaster.tpr"; if [ $? -ne 0 ]; then echo FAILED building "\"Cave Blaster.tpr\""; fi