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/* Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
/*
* FDCACHE -- Maintain a cache of filenames and their associated modification
* dates. This can greatly reduce the amount of time required to determine
* which, if any, of the modules in a library need updating because an include
* file they depend upon has been modified.
*
* External entry points:
*
* l = m_fdate (fname) # return file (modification) date
* m_fdinit (debug) # initialize cache
*/
#define MAX_FILES 20 /* size of the cache */
#define SZ_NAME 32 /* size of filename slot */
#define EOS '\0'
struct _fdate { /* cache list element structure */
struct _fdate *uplnk;
struct _fdate *dnlnk;
int nrefs; /* number of references */
int chksum; /* speeds searches */
long fdate; /* file modification date */
char fname[SZ_NAME+1]; /* file name */
};
struct _fdate fdcache[MAX_FILES]; /* the cache */
struct _fdate *fd_head; /* doubly linked list */
struct _fdate *fd_tail;
int fd_hits, fd_misses;
struct _fdate *fd_unlink();
struct _fdate *fd_tohead();
struct _fdate *fd_totail();
long m_fdate (char *fname);
void m_fdinit (int debug);
int fd_chksum (char *s);
extern long os_fdate (char *fname);
/* M_FDATE -- Get file modification date. This is functionally equivalent to
* os_fdate().
*/
long
m_fdate (char *fname)
{
register struct _fdate *fd;
register int chksum;
/* Look in the cache first.
*/
chksum = fd_chksum (fname);
for (fd=fd_head; fd != NULL; fd=fd->dnlnk)
if (fd->chksum == chksum && strcmp (fname, fd->fname) == 0) {
fd_tohead (fd_unlink (fd));
fd->nrefs++;
fd_hits++;
return (fd->fdate);
}
/* Cache miss. Don't put in cache it name is too long.
*/
fd_misses++;
if (strlen (fname) > SZ_NAME)
return (os_fdate (fname));
/* Put fname in the cache. Reuse slot at tail of list.
*/
fd = fd_tohead (fd_unlink (fd_tail));
strncpy (fd->fname, fname, SZ_NAME);
fd->chksum = fd_chksum (fname);
fd->fdate = os_fdate (fname);
fd->nrefs = 1;
return (fd->fdate);
}
/* M_FDINIT -- Initialize (clear) the fdate cache.
*/
void
m_fdinit (int debug)
{
register struct _fdate *fd;
register int i;
int total;
if (debug) {
total = fd_hits + fd_misses;
printf ("file date cache: %d hits, %d misses, %d%% of %d\n",
fd_hits, fd_misses, (total ? fd_hits * 100 / total : 0), total);
for (fd=fd_head; fd != NULL; fd=fd->dnlnk)
if (fd->fname[0])
printf ("%3d %10ld (%05d) %s\n",
fd->nrefs, fd->fdate, fd->chksum, fd->fname);
fd_hits = 0;
fd_misses = 0;
fflush (stdout);
}
fd = fd_head = fd_tail = &fdcache[0];
fd->uplnk = NULL;
fd->dnlnk = NULL;
fd->nrefs = 0;
fd->chksum = -1;
fd->fname[0] = EOS;
for (i=1; i < MAX_FILES; i++) {
fd = fd_tohead (&fdcache[i]);
fd->fname[0] = EOS;
fd->chksum = -1;
fd->nrefs = 0;
}
}
/* FD_TOHEAD -- Link a fdate struct at the head of the list.
*/
struct _fdate *
fd_tohead (register struct _fdate *fd)
{
if (fd != fd_head) {
fd->uplnk = NULL;
fd->dnlnk = fd_head;
fd_head->uplnk = fd;
fd_head = fd;
}
return (fd);
}
/* FD_TOTAIL -- Link a fdate struct at the tail of the list.
*/
struct _fdate *
fd_totail (register struct _fdate *fd)
{
if (fd != fd_tail) {
fd->uplnk = fd_tail;
fd->dnlnk = NULL;
fd_tail->dnlnk = fd;
fd_tail = fd;
}
return (fd);
}
/* FD_UNLINK -- Unlink an fdate struct.
*/
struct _fdate *
fd_unlink (register struct _fdate *fd)
{
if (fd == fd_head)
fd_head = fd->dnlnk;
if (fd == fd_tail)
fd_tail = fd->uplnk;
if (fd->uplnk)
fd->uplnk->dnlnk = fd->dnlnk;
if (fd->dnlnk)
fd->dnlnk->uplnk = fd->uplnk;
return (fd);
}
/* FD_CHKSUM -- Compute the checksum of a character string.
*/
int
fd_chksum (char *s)
{
register int sum=0;
while (*s)
sum += *s++;
return (sum);
}
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