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 <climits>

#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();
}

class StrTable {
  public:
  StrTable() {
    memset(table, 0, sizeof(table));
    for (int i = 1; i <= CHAR_MAX; i++) {
      table[i*2] = static_cast<char>(i);
    }
  }
  const char *get(char c) { assert(c >= 0); return &table[c*2]; }
  private:
  char table[2*(CHAR_MAX + 1)];
};
static StrTable g_table;

const char *cp_char2str(char c) {
  return g_table.get(c);
}

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);
  if (len == 0)
    return g_table.get('\0');
  else if (len == 1)
    return g_table.get(*src);

  int sz = len + 1;
  char *p = buckets.back() + nexti;

  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);
}