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gcache.c
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gcache.c
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/*
* Copyright (c) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
* 2002, 2003, 2004
* Ohio University.
*
* ---
*
* Starting with the release of tcptrace version 6 in 2001, tcptrace
* is licensed under the GNU General Public License (GPL). We believe
* that, among the available licenses, the GPL will do the best job of
* allowing tcptrace to continue to be a valuable, freely-available
* and well-maintained tool for the networking community.
*
* Previous versions of tcptrace were released under a license that
* was much less restrictive with respect to how tcptrace could be
* used in commercial products. Because of this, I am willing to
* consider alternate license arrangements as allowed in Section 10 of
* the GNU GPL. Before I would consider licensing tcptrace under an
* alternate agreement with a particular individual or company,
* however, I would have to be convinced that such an alternative
* would be to the greater benefit of the networking community.
*
* ---
*
* This file is part of Tcptrace.
*
* Tcptrace was originally written and continues to be maintained by
* Shawn Ostermann with the help of a group of devoted students and
* users (see the file 'THANKS'). The work on tcptrace has been made
* possible over the years through the generous support of NASA GRC,
* the National Science Foundation, and Sun Microsystems.
*
* Tcptrace is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* Tcptrace is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Tcptrace (in the file 'COPYING'); if not, write to the
* Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
* MA 02111-1307 USA
*
* Author: Shawn Ostermann
* School of Electrical Engineering and Computer Science
* Ohio University
* Athens, OH
* ostermann@cs.ohiou.edu
* http://www.tcptrace.org/
*/
#include "tcptrace.h"
static char const GCC_UNUSED copyright[] =
"@(#)Copyright (c) 2004 -- Ohio University.\n";
static char const GCC_UNUSED rcsid[] =
"@(#)$Header$";
/*
* gcache.c - generalized cacheing routines
*/
#include <sys/types.h>
#include "gcache.h"
/* Let's use ANSI C rather than old BSD calls... */
#ifndef bzero
#define bzero(ptr,nbytes) memset(ptr,0,nbytes)
#endif
#ifndef bcopy
#define bcopy(from_ptr,to_ptr,nbytes) memcpy(to_ptr,from_ptr,nbytes)
#endif
static int ca_enabled;
/* control block for a single cache */
enum cb_status { CB_INUSE=1, CB_FREE=2};
typedef enum cb_status cb_status;
struct cacheblk {
cb_status cb_status; /* INUSE or FREE */
char cb_name[CA_NAMELEN]; /* name of the cache */
u_short cb_maxent; /* maximum entries */
u_short cb_nument; /* number of entries */
u_short cb_hashsize; /* size of hash table */
u_int cb_maxlife; /* max life of an entry (secs) */
struct cacheentry *cb_cache; /* free nodes for the cache */
struct hashentry *cb_hash; /* the hash table */
tceix cb_freelist; /* list of free cacheentries */
/* statistics variables, mostly for debugging */
u_int cb_lookups; /* # lookups */
u_int cb_hits; /* # hits */
u_int cb_tos; /* # timed out entries */
u_int cb_fulls; /* # removed, full table */
};
/* a single node in the hash table */
struct hashentry {
tceix he_ix;
};
#define NULL_PHE ((struct hashentry *) 0)
#define NULL_IX 0
/* a cached item in the hash list */
enum ce_status {CE_INUSE=11, CE_FREE=12};
typedef enum ce_status ce_status;
struct cacheentry {
ce_status ce_status; /* INUSE or FREE */
char *ce_keyptr; /* pointer to the key */
tcelen ce_keylen; /* length of the key */
char *ce_resptr; /* pointer to the result */
tcelen ce_reslen; /* length of the result */
thval ce_hash; /* value that was hashed in */
ttstamp ce_tsinsert; /* timestamp - time inserted */
ttstamp ce_tsaccess; /* timestamp - last access */
tceix ce_prev; /* next entry on list */
tceix ce_next; /* prev entry on list */
};
#define NULL_PCE ((struct cacheentry *) 0)
/* locally global information */
static struct cacheblk catab[CA_NUMCACHES];
/* useful macros */
#define ISBADCID(cid) ((cid < 0) || (cid > CA_NUMCACHES) || \
(catab[cid].cb_status != CB_INUSE))
#define HASHTOIX(hash,pcb) ((hash) % (pcb->cb_hashsize))
/* debugging hooks */
static int docadebug = 0;
static int docaerror = 1;
#define CADEBUG if (docadebug) fprintf
#define CAERROR if (docaerror) fprintf
/* local routines defns */
static char *cagetmem(u_int);
static void cadeleteold(struct cacheblk *);
static void caclear(struct cacheblk *, tceix);
static void cafreemem(void *, u_int);
static tceix cagetfree(struct cacheblk *);
static tceix cagetindex(struct cacheblk *, char *, tcelen, thval);
static thval cahash(char *, tcelen);
static int caisold(struct cacheblk *, struct cacheentry *);
static void casetsize(struct cacheblk *, int);
static void caunlink(struct cacheblk *, tceix);
/*************************************************************************/
/** **/
/** GLOBAL ROUTINES **/
/** **/
/*************************************************************************/
/*
* ====================================================================
* cainit - initialize the caching tables
* ====================================================================
*/
int
cainit(void)
{
struct cacheblk *pcb;
int cid;
for (cid=0; cid < CA_NUMCACHES; ++cid) {
pcb = &catab[cid];
bzero(pcb,sizeof(struct cacheblk));
pcb->cb_status = CB_FREE;
}
ca_enabled = TRUE;
return(OK);
}
/*
* ====================================================================
* cacreate - create a new cache
* ====================================================================
*/
int
cacreate(
char *name,
int nentries,
int lifetime)
{
int cid;
tceix ix;
struct cacheblk *pcb;
struct cacheentry *pce;
/* check config limits */
if (nentries >= CA_MAXENTRIES) {
CAERROR(stderr,"cacreate(%s,%d,%d): SYSERR, nentries > max (%d)\n",
name, nentries, lifetime, CA_MAXENTRIES);
return(SYSERR);
}
for (cid=0; cid < CA_NUMCACHES; ++cid) {
pcb = &catab[cid];
if (pcb->cb_status == CB_FREE)
break;
}
if (cid == CA_NUMCACHES) {
CAERROR(stderr,"cacreate(%s,%d,%d): SYSERR, no more caches\n",
name, nentries, lifetime);
return(SYSERR);
}
bzero(pcb, sizeof(struct cacheblk));
pcb->cb_status = CB_INUSE;
#ifdef linux
#ifdef strncpy
/* stupid Linux (redhat?) bug in macro */
#undef strncpy
#endif /* strncpy */
#endif /* linux */
strncpy(pcb->cb_name,name,CA_NAMELEN);
pcb->cb_name[CA_NAMELEN-1] = '\00';
pcb->cb_maxent = nentries;
casetsize(pcb,nentries);
pcb->cb_maxlife = lifetime;
/* allocate the cache entries */
/* (0 is reserved as a null pointer, so we allocate from 0 */
/* to maxent, rather than maxent-1) */
pcb->cb_cache = (struct cacheentry *)
cagetmem((1+pcb->cb_maxent) * sizeof(struct cacheentry));
bzero(pcb->cb_cache,
(1+pcb->cb_maxent) * sizeof(struct cacheentry));
/* put them all on the free list (only forward pointers) */
for (ix=1; ix <= pcb->cb_maxent; ++ix) {
pce = &pcb->cb_cache[ix];
pce->ce_status = CE_FREE;
pce->ce_next = ix+1;
}
pcb->cb_cache[pcb->cb_maxent].ce_next = NULL_IX;
pcb->cb_freelist = 1;
/* allocate the hash table */
pcb->cb_hash = (struct hashentry *)
cagetmem(pcb->cb_hashsize * sizeof(struct hashentry));
for (ix=0; ix < pcb->cb_hashsize; ++ix) {
pcb->cb_hash[ix].he_ix = NULL_IX;
}
CADEBUG(stderr,"cacreate(%s,%d,%d) returns cache %d\n",
name, nentries, lifetime, cid);
return(cid);
}
/*
* ====================================================================
* cadestroy - destroy an existing cache
* ====================================================================
*/
int
cadestroy(
int cid)
{
struct cacheblk *pcb;
if (ISBADCID(cid)) {
CAERROR(stderr,"cadestroy(%d,...) cid is bad\n", cid);
return(SYSERR);
}
pcb = &catab[cid];
/* free up all the entries */
(void) capurge(cid);
/* free up the hash table */
cafreemem(pcb->cb_hash,
pcb->cb_hashsize * sizeof(struct hashentry));
/* free up the cached blocks */
cafreemem(pcb->cb_cache,
(1+pcb->cb_maxent) * sizeof(struct cacheentry));
/* zero out the table */
bzero(pcb,sizeof(struct cacheblk));
pcb->cb_status = CB_FREE;
return(OK);
}
/*
* ====================================================================
* cainsert - insert a new entry into an existing cache
* ====================================================================
*/
int
cainsert(
int cid,
char *pkey,
tcelen keylen,
char *pres,
tcelen reslen)
{
struct cacheblk *pcb;
struct cacheentry *pce;
struct hashentry *phe;
thval hash;
tceix ixnew;
/* check argument validity */
if (ISBADCID(cid)) {
CAERROR(stderr,"cainsert(%d,...) cid is bad\n", cid);
return(SYSERR);
}
if ((keylen > CA_MAXKEY) || (reslen > CA_MAXRES)) {
CAERROR(stderr,"cainsert: SYSERR, key or result too large\n");
return(SYSERR);
}
if (!ca_enabled)
return(OK);
pcb = &catab[cid];
hash = cahash(pkey,keylen);
phe = &pcb->cb_hash[HASHTOIX(hash,pcb)];
if ((ixnew = cagetindex(pcb,pkey,keylen,hash)) != NULL_IX) {
/* use the old one */
caclear(pcb,ixnew);
pce = &pcb->cb_cache[ixnew];
CADEBUG(stderr,"cainsert(%d): reusing cache slot %d, nument:%d\n",
cid, ixnew, pcb->cb_nument);
} else {
/* get a free cacheentry */
ixnew = cagetfree(pcb);
pce = &pcb->cb_cache[ixnew];
/* ... and put it at the head of the list */
pce->ce_prev = 0;
pce->ce_next = phe->he_ix;
pcb->cb_cache[phe->he_ix].ce_prev = ixnew;
phe->he_ix = ixnew;
CADEBUG(stderr,"cainsert(%d): using new cache slot %d, nument:%d\n",
cid, ixnew, pcb->cb_nument);
}
pce->ce_status = CE_INUSE;
pce->ce_hash = hash;
pce->ce_keyptr = cagetmem(keylen);
pce->ce_keylen = keylen;
bcopy(pkey,pce->ce_keyptr,(int)keylen);
pce->ce_resptr = cagetmem(reslen);
pce->ce_reslen = reslen;
bcopy(pres,pce->ce_resptr,(int)reslen);
time(&pce->ce_tsinsert);
pce->ce_tsaccess = pce->ce_tsinsert;
return(OK);
}
/*
* ====================================================================
* calookup - find an entry in the cache given the key, return info
* ====================================================================
*/
int
calookup(
int cid,
char *pkey,
tcelen keylen,
char *pres,
tcelen *preslen)
{
struct cacheblk *pcb;
struct cacheentry *pce;
thval hash;
tceix ix;
if (ISBADCID(cid)) {
CAERROR(stderr,"calookup(%d,...) cid is bad\n", cid);
return(SYSERR);
}
if (!ca_enabled)
return(SYSERR);
pcb = &catab[cid];
hash = cahash(pkey,keylen);
if ((ix = cagetindex(pcb,pkey,keylen,hash)) != NULL_IX) {
pce = &pcb->cb_cache[ix];
if (pce->ce_reslen <= *preslen) {
time(&pce->ce_tsaccess);
bcopy(pce->ce_resptr,pres,(int)pce->ce_reslen);
*preslen = pce->ce_reslen;
return(OK);
}
}
return(SYSERR);
}
/*
* ====================================================================
* caremove - remove an entry from the cache if it exists
* ====================================================================
*/
int
caremove(
int cid,
char *pkey,
tcelen keylen)
{
struct cacheblk *pcb;
unsigned hash;
tceix ix;
if (ISBADCID(cid)) {
CAERROR(stderr,"caremove(%d,...) cid is bad\n", cid);
return(SYSERR);
}
pcb = &catab[cid];
hash = cahash(pkey,keylen);
if ((ix = cagetindex(pcb,pkey,keylen,hash)) != NULL_IX) {
CADEBUG(stderr,"caremove(%d): killing entry in slot %d:\n",
cid, ix);
caunlink(pcb,ix);
}
return(OK);
}
/*
* ====================================================================
* capurge - remove all entries in an existing cache
* ====================================================================
*/
int
capurge(
int cid)
{
struct cacheblk *pcb;
struct cacheentry *pce;
struct hashentry *phe;
tceix ix;
if (ISBADCID(cid)) {
CAERROR(stderr,"capurge(%d,...) cid is bad\n", cid);
return(SYSERR);
}
pcb = &catab[cid];
/* free all cached entries */
for (ix=1; ix <= pcb->cb_maxent; ++ix) {
pce = &pcb->cb_cache[ix];
if (pce->ce_status == CE_INUSE)
caunlink(pcb,ix);
pce->ce_status = CE_FREE;
}
/* clear the hash table */
for (ix=0; ix < pcb->cb_hashsize; ++ix) {
phe = &pcb->cb_hash[ix];
bzero(phe,sizeof(struct hashentry));
phe->he_ix = NULL_IX;
}
pcb->cb_nument = 0;
return(OK);
}
/*
* ====================================================================
* cadump - dump contents of the cache structures
* ====================================================================
*/
void
cadump(void)
{
int cid;
int purge;
int zero;
struct cacheblk *pcb;
purge = zero = FALSE;
fprintf(stderr,"\nmaxcaches: %d (caching %sabled)\n",
CA_NUMCACHES,
ca_enabled?"en":"DIS");
fprintf(stderr,"\
ix name maxent nument htsize life tos full finds hits hit%%\n");
fprintf(stderr,"\
== =============== ====== ====== ====== ==== ==== ==== ====== ====== ====\n");
for (cid=0; cid < CA_NUMCACHES; ++cid) {
pcb = &catab[cid];
if (pcb->cb_status == CB_FREE)
continue;
if (purge)
capurge(cid);
if (zero) {
pcb->cb_tos = 0;
pcb->cb_fulls = 0;
pcb->cb_lookups = 0;
pcb->cb_hits = 0;
}
fprintf(stderr,"%2d %-15s %6d %6d %6d %4d %4d %4d %6d %6d %3d%%",
cid,
pcb->cb_name,
pcb->cb_maxent,
pcb->cb_nument,
pcb->cb_hashsize,
pcb->cb_maxlife,
pcb->cb_tos,
pcb->cb_fulls,
pcb->cb_lookups,
pcb->cb_hits,
(pcb->cb_lookups)?
((100 * pcb->cb_hits) / pcb->cb_lookups):0);
fprintf(stderr,"\n");
}
}
/*************************************************************************/
/** **/
/** LOCAL FUNCTIONS **/
/** **/
/*************************************************************************/
/*
* ====================================================================
* cahash - return the hash value for a key
* ====================================================================
*/
static thval
cahash(
char *pkey,
tcelen keylen)
{
int i;
thval hval;
hval = 0;
for (i=0; i < keylen; ++i)
hval += *pkey++;
return(hval);
}
/* try to reduce fragmentation */
#define CAMEMSIZE(nb) ((unsigned) (((nb) + 31) & ~31))
/*
* ====================================================================
* cagetmem - get memory for a cached entry
* ====================================================================
*/
static char *
cagetmem(
u_int nbytes)
{
char *ret;
ret = malloc(CAMEMSIZE(nbytes));
if (!ret) {
perror("cagetmem malloc");
exit(-1);
}
return(ret);
}
/*
* ====================================================================
* cafreemem - free memory from a cached entry
* ====================================================================
*/
static void
cafreemem(
void *ptr,
u_int nbytes)
{
free(ptr);
}
/*
* ====================================================================
* cadeleteold - delete the "oldest" cached entry
* ====================================================================
*/
static void
cadeleteold(
struct cacheblk *pcb)
{
struct cacheentry *pce;
unsigned oldtime;
tceix oldix;
tceix ix;
/* check everyone against the first entry */
oldix = 1;
pce = &pcb->cb_cache[oldix];
oldtime = pce->ce_tsaccess;
for (ix=2; ix <= pcb->cb_maxent; ++ix) {
pce = &pcb->cb_cache[ix];
if ((pce->ce_status == CE_INUSE) &&
(pce->ce_tsaccess < oldtime)) {
oldix = ix;
oldtime = pce->ce_tsaccess;
}
}
/* nuke the oldest one */
pce = &pcb->cb_cache[oldix];
caunlink(pcb,oldix);
return;
}
/*
* ====================================================================
* caclear - clear out the given entry, set status to FREE
* ====================================================================
*/
static void
caclear(
struct cacheblk *pcb,
tceix ix)
{
struct cacheentry *pce;
pce = &pcb->cb_cache[ix];
if (pce->ce_keyptr)
cafreemem(pce->ce_keyptr,pce->ce_keylen);
if (pce->ce_resptr)
cafreemem(pce->ce_resptr,pce->ce_reslen);
bzero(pce,sizeof(struct cacheentry));
pce->ce_status = CE_FREE;
}
/*
* ====================================================================
* caisold - return TRUE if the given entry is "too old"
* ====================================================================
*/
static int
caisold(
struct cacheblk *pcb,
struct cacheentry *pce)
{
time_t now;
if (pcb->cb_maxlife == 0)
return(FALSE);
time(&now);
return ((now - pce->ce_tsaccess) > pcb->cb_maxlife);
}
/*
* ====================================================================
* cagetindex - return the index of a matching entry, or SYSERR
* ====================================================================
*/
static tceix
cagetindex(
struct cacheblk *pcb,
char *pkey,
tcelen keylen,
thval hashval)
{
struct cacheentry *pce;
tceix ix;
tceix nextix;
++pcb->cb_lookups;
ix = pcb->cb_hash[HASHTOIX(hashval,pcb)].he_ix;
while (ix != NULL_IX) {
pce = &pcb->cb_cache[ix];
nextix = pce->ce_next;
CADEBUG(stderr,"cagetindex[%d]: ", ix);
if ((pce->ce_hash == hashval) &&
(pce->ce_keylen == keylen) &&
(memcmp((void *)pkey,(void *)pce->ce_keyptr,(int) keylen) == 0)) {
/* this is a match */
++pcb->cb_hits;
if (caisold(pcb,pce)) {
++pcb->cb_tos;
CADEBUG(stderr,"OLD\n");
caunlink(pcb,ix);
return(NULL_IX);
} else {
CADEBUG(stderr,"YES\n");
return(ix);
}
}
CADEBUG(stderr,"NO (%d!=%d, %d!=%d)\n",
pce->ce_hash, hashval,
pce->ce_keylen, keylen);
ix = nextix;
}
return(NULL_IX);
}
/*
* ====================================================================
* casetsize - set the hash table size
* ====================================================================
*/
static void
casetsize(
struct cacheblk *pcb,
int nentries)
{
if (nentries <= 10)
pcb->cb_hashsize = 13;
else if (nentries <= 25)
pcb->cb_hashsize = 29;
else if (nentries <= 50)
pcb->cb_hashsize = 53;
else if (nentries <= 100)
pcb->cb_hashsize = 101;
else if (nentries <= 200)
pcb->cb_hashsize = 213;
else
/* pcb->cb_hashsize = nentries * 1.25;*/
/* avoid the floating point */
pcb->cb_hashsize = (nentries * 5) >> 2;
/* 5 >> 2 == 5 / 4 == 1.25 */
return;
}
/*
* ====================================================================
* cagetfree - return the index of an unused pce. If there aren't any
* left, delete an old one and return it.
* ====================================================================
*/
static tceix
cagetfree(
struct cacheblk *pcb)
{
struct cacheentry *pce;
tceix ix;
/* if the free list is empty, delete the oldest entry */
if (pcb->cb_freelist == NULL_IX) {
CADEBUG(stderr,"cagetfree: cache full, deleting old entry, nument:%d\n",
pcb->cb_nument);
cadeleteold(pcb);
++pcb->cb_fulls;
}
/* remove the head of the list */
ix = pcb->cb_freelist;
pce = &pcb->cb_cache[ix];
pcb->cb_freelist = pce->ce_next;
++pcb->cb_nument;
CADEBUG(stderr,"cagetfree: returning slot %d\n", ix);
return(ix);
}
/*
* ====================================================================
* caunlink - remove a cached entry from a list (and erase it)
* return it to the free list
* ====================================================================
*/
static void
caunlink(
struct cacheblk *pcb,
tceix ix)
{
struct cacheentry *pce;
struct hashentry *phe;
thval hash;
pce = &pcb->cb_cache[ix];
hash = pce->ce_hash;
phe = &pcb->cb_hash[HASHTOIX(hash,pcb)];
if (pce->ce_prev == NULL_IX)
phe->he_ix = pce->ce_next;
else
pcb->cb_cache[pce->ce_prev].ce_next = pce->ce_next;
pcb->cb_cache[pce->ce_next].ce_prev = pce->ce_prev;
caclear(pcb,ix);
/* return it to the free list */
pce->ce_next = pcb->cb_freelist;
pcb->cb_freelist = ix;
--pcb->cb_nument;
}