nmap/charpool.cc

/***************************************************************************
 * charpool.cc -- Handles Nmap's "character pool" memory allocation        *
 * system.                                                                 *
 *                                                                         *
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 ***************************************************************************/

/* $Id$ */

#include <stddef.h>
#undef NDEBUG
#include <assert.h>

#include "nbase.h"

/* Character pool memory allocation */
#include "charpool.h"
#include "nmap_error.h"

static CharPool g_charpool (16384);

const char *cp_strndup(const char *src, int len) {
  return g_charpool.dup(src, len);
}
const char *cp_strdup(const char *src) {
  return g_charpool.dup(src);
}
void cp_free(void) {
  return g_charpool.clear();
}

/* Allocated blocks are allocated to multiples of ALIGN_ON. This is the
   definition used by the malloc in Glibc 2.7, which says that it "suffices for
   nearly all current machines and C compilers." */
#define ALIGN_ON (2 * sizeof(size_t))

CharPool::CharPool(size_t init_sz) {
  assert(init_sz >= 256);
  /* Create our char pool */
  currentbucketsz = init_sz;
  nexti = 0;
  char *b = (char *) safe_malloc(currentbucketsz);
  buckets.push_back(b);
}

void CharPool::clear(void) {
  for (BucketList::iterator it=buckets.begin(); it != buckets.end(); it++) {
    free(*it);
  }
  buckets.clear();
}

const char *CharPool::dup(const char *src, int len) {
  if (len < 0)
    len = strlen(src);
  int sz = len + 1;
  char *p = buckets.back() + nexti;
  int modulus;

  if ((modulus = sz % ALIGN_ON))
    sz += ALIGN_ON - modulus;

  while (nexti + sz > currentbucketsz) {
    /* Doh!  We've got to make room */
    currentbucketsz <<= 1;
    nexti = 0;
    p = (char *) safe_malloc(currentbucketsz);
    buckets.push_back(p);
  }

  nexti += sz;
  p[len] = '\0';
  return (const char *) memcpy(p, src, len);
}