text: /*-
   * Copyright (c) 1980, 1992, 1993
   *	The 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.
   * 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 <sys/cdefs.h>
  
  __FBSDID("$FreeBSD: soc2013/dpl/head/usr.bin/systat/fetch.c 226676 2011-10-15 13:20:36Z ed $");
  
  #ifdef lint
  static const char sccsid[] = "@(#)fetch.c	8.1 (Berkeley) 6/6/93";
  #endif
  
  #include <sys/types.h>
  #include <sys/sysctl.h>
  
  #include <err.h>
  #include <errno.h>
  #include <stdlib.h>
  #include <string.h>
  
  #include "systat.h"
  #include "extern.h"
  
  int
  kvm_ckread(void *a, void *b, int l)
  {
  	if (kvm_read(kd, (u_long)a, b, l) != l) {
  		if (verbose)
  			error("error reading kmem at %p", a);
  		return (0);
  	}
  	else
  		return (1);
  }
  
  void getsysctl(const char *name, void *ptr, size_t len)
  {
  	size_t nlen = len;
  	if (sysctlbyname(name, ptr, &nlen, NULL, 0) != 0) {
  		error("sysctl(%s...) failed: %s", name,
  		    strerror(errno));
  	}
  	if (nlen != len) {
  		error("sysctl(%s...) expected %lu, got %lu", name,
  		    (unsigned long)len, (unsigned long)nlen);
      }
  }
  
  /*
   * Read sysctl data with variable size. Try some times (with increasing
   * buffers), fail if still too small.
   * This is needed sysctls with possibly raplidly increasing data sizes,
   * but imposes little overhead in the case of constant sizes.
   * Returns NULL on error, or a pointer to freshly malloc()'ed memory that holds
   * the requested data.
   * If szp is not NULL, the size of the returned data will be written into *szp.
   */
  
  /* Some defines: Number of tries. */
  #define SD_NTRIES  10
  /* Percent of over-allocation (initial) */
  #define SD_MARGIN  10
  /*
   * Factor for over-allocation in percent (the margin is increased by this on
   * any failed try).
   */
  #define SD_FACTOR  50
  /* Maximum supported MIB depth */
  #define SD_MAXMIB  16
  
  char *
  sysctl_dynread(const char *n, size_t *szp)
  {
  	char   *rv = NULL;
  	int    mib[SD_MAXMIB];
  	size_t mibsz = SD_MAXMIB;
  	size_t mrg = SD_MARGIN;
  	size_t sz;
  	int i;
  
  	/* cache the MIB */
  	if (sysctlnametomib(n, mib, &mibsz) == -1) {
  		if (errno == ENOMEM) {
  			error("XXX: SD_MAXMIB too small, please bump!");
  		}
  		return NULL;
  	}
  	for (i = 0; i < SD_NTRIES; i++) {
  		/* get needed buffer size */
  		if (sysctl(mib, mibsz, NULL, &sz, NULL, 0) == -1)
  			break;
  		sz += sz * mrg / 100;
  		if ((rv = (char *)malloc(sz)) == NULL) {
  			error("Out of memory!");
  			return NULL;
  		}
  		if (sysctl(mib, mibsz, rv, &sz, NULL, 0) == -1) {
  			free(rv);
  			rv = NULL;
  			if (errno == ENOMEM) {
  				mrg += mrg * SD_FACTOR / 100;
  			} else
  				break;
  		} else {
  			/* success */
  			if (szp != NULL)
  				*szp = sz;
  			break;
  		}
  	}
  
  	return rv;
  }
  