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/*
* Copyright (c) 1987, 1989 University of Maryland
* Department of Computer Science. All rights reserved.
* Permission to copy for any purpose is hereby granted
* so long as this copyright notice remains intact.
*/
/*
* Key search routines (for a 32 bit key)
*
* SCreate initializes the search control area.
*
* SSearch returns the address of the data area (if found or created)
* or a null pointer (if not). The last argument controls the disposition
* in various cases, and is a ``value-result'' parameter.
*
* SEnumerate calls the given function on each data object within the
* search table. Note that no ordering is specified (though currently
* it runs in increasing-key-value sequence).
*/
#include "types.h"
#include "search.h"
#if vax || mc68000 || ns32000 || pyr
#define HARD_ALIGNMENT 4
#else
#define HARD_ALIGNMENT 16 /* should suffice for most everyone */
#endif
static int DOffset; /* part of alignment code */
#ifndef KPATHSEA
char *malloc(), *realloc();
#endif
struct search *
SCreate(unsigned int dsize)
{
register struct search *s;
if ((s = (struct search *) malloc(sizeof *s)) == 0)
return (0);
if (DOffset == 0) {
#ifndef HARD_ALIGNMENT
DOffset = sizeof(i32);
#else
DOffset = (sizeof(i32) + HARD_ALIGNMENT - 1) &
~(HARD_ALIGNMENT - 1);
#endif
}
dsize += DOffset; /* tack on space for keys */
#ifdef HARD_ALIGNMENT
/*
* For machines with strict alignment constraints, it may be
* necessary to align the data at a multiple of some positive power
* of two. In general, it would suffice to make dsize a power of
* two, but this could be very space-wasteful, so instead we align it
* to HARD_ALIGNMENT. 64 bit machines might ``#define HARD_ALIGNMENT
* 8'', for example. N.B.: we assume that HARD_ALIGNMENT is a power
* of two.
*/
dsize = (dsize + HARD_ALIGNMENT - 1) & ~(HARD_ALIGNMENT - 1);
#endif
s->s_dsize = dsize; /* save data object size */
s->s_space = 10; /* initially, room for 10 objects */
s->s_n = 0; /* and none in the table */
if ((s->s_data = malloc(s->s_space * dsize)) == 0) {
free((char *)s);
return (0);
}
return (s);
}
/*
* We actually use a binary search right now - this may change.
*/
char *
SSearch(struct search *s, i32 key, int *disp)
{
register char *keyaddr;
int itemstomove;
*disp &= S_CREATE | S_EXCL; /* clear return codes */
if (s->s_n) { /* look for the key */
register int h, l, m;
h = s->s_n - 1;
l = 0;
while (l <= h) {
m = (l + h) >> 1;
keyaddr = s->s_data + m * s->s_dsize;
if (*(i32 *) keyaddr > key)
h = m - 1;
else if (*(i32 *) keyaddr < key)
l = m + 1;
else { /* found it, now what? */
if (*disp & S_EXCL) {
*disp |= S_COLL;
return (0); /* collision */
}
*disp |= S_FOUND;
return (keyaddr + DOffset);
}
}
keyaddr = s->s_data + l * s->s_dsize;
} else
keyaddr = s->s_data;
/* keyaddr is now where the key should have been found, if anywhere */
if ((*disp & S_CREATE) == 0)
return (0); /* not found */
/* avoid using realloc so as to retain old data if out of memory */
if (s->s_space <= 0) { /* must expand; double it */
register char *new;
if ((new = malloc((s->s_n << 1) * s->s_dsize)) == 0) {
*disp |= S_ERROR; /* no space */
return (0);
}
keyaddr = (keyaddr - s->s_data) + new; /* relocate */
bcopy(s->s_data, new, s->s_n * s->s_dsize);
free(s->s_data);
s->s_data = new;
s->s_space = s->s_n;
}
/* now move any keyed data that is beyond keyaddr down */
itemstomove = s->s_n - (keyaddr - s->s_data) / s->s_dsize;
if (itemstomove) {
#ifndef BLOCK_COPY
register char *from, *to;
from = s->s_data + s->s_n * s->s_dsize;
to = from + s->s_dsize;
while (from > keyaddr)
*--to = *--from;
#else
BLOCK_COPY(keyaddr, keyaddr + s->s_dsize,
itemstomove * s->s_dsize);
#endif
}
*disp |= S_NEW;
s->s_n++;
s->s_space--;
*(i32 *) keyaddr = key;
keyaddr += DOffset; /* now actually dataaddr */
/* the bzero is just a frill... */
bzero(keyaddr, s->s_dsize - DOffset);
return (keyaddr);
}
/*
* Call function `f' for each element in the search table `s'.
*/
void
SEnumerate(struct search *s, void(*f)(char*,i32))
{
register int n;
register char *p;
n = s->s_n;
p = s->s_data;
while (--n >= 0) {
(*f)(p + DOffset, *(i32 *)p);
p += s->s_dsize;
}
}
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