string_pool.cc

/***************************************************************************
 * string_pool.cc -- String interning for memory optimization              *
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#include "string_pool.h"
#include <nbase.h>
#include "charpool.h"

#include <set>
#include <string>
#include <cstring>
#include <utility>
#include <stdarg.h>
#include <ctype.h>

/* Keep assert() defined for security reasons */
#undef NDEBUG
#include <assert.h>

class StringPoolItem {
  public:
    const char *str;
    int len;
    bool in_cp;

    StringPoolItem(const char *i_str, int i_len) : str(i_str), len(i_len), in_cp(false) {}
    ~StringPoolItem() {} // charpool allocations are permanent and can't be freed.
    StringPoolItem(const StringPoolItem& other) {
      // If the string is already in the charpool, there's no reason we should
      // be copy-constructed, since that only happens on a successful insert
      // (new unique item)
      assert(!other.in_cp);
      this->len = other.len;
      this->str = cp_strndup(other.str, other.len);
      this->in_cp = true;
    }

// asdfq <> asdf
    bool operator< (const StringPoolItem& other) const {
      return this->len < other.len || memcmp(this->str, other.str, other.len) < 0;
    }
};

typedef std::set<StringPoolItem> StringPool;

const char *string_pool_insert_len(const char *s, int len)
{
  static StringPool pool;
  if (len == 0)
    return "";
  else if (len == 1)
    return cp_char2str(*s);

  StringPoolItem spi (s, len);

  StringPool::iterator it = pool.insert(spi).first;
  assert(it->in_cp); // We should only be storing charpool-allocated strings

  return it->str;
}

const char *string_pool_insert(const char *s)
{
  return string_pool_insert_len(s, strlen(s));
}

const char *string_pool_substr(const char *s, const char *t)
{
  assert(t >= s);
  return string_pool_insert_len(s, t - s);
}

const char *string_pool_substr_strip(const char *s, const char *t) {
  while (s < t && isspace((int) (unsigned char) *s))
    s++;
  while (t > s && isspace((int) (unsigned char) *(t - 1)))
    t--;

  return string_pool_substr(s, t);
}

const char *string_pool_strip_word(const char *s, const char *end) {
  const char *t;

  while (isspace((int) (unsigned char) *s))
    s++;
  t = s;
  while (t < end && *t != '\0' && !isspace((int) (unsigned char) *t))
    t++;

  if (s == t)
    return NULL;

  return string_pool_substr(s, t);
}

/* Format a string with sprintf and insert it with string_pool_insert. */
const char *string_pool_sprintf(const char *fmt, ...)
{
  const char *s;
  char *buf;
  int size, n;
  va_list ap;

  buf = NULL;
  size = 32;
  /* Loop until we allocate a string big enough for the sprintf. */
  for (;;) {
    buf = (char *) safe_realloc(buf, size);
    va_start(ap, fmt);
    n = Vsnprintf(buf, size, fmt, ap);
    va_end(ap);
    if (n < 0)
      size = size * 2;
    else if (n >= size)
      size = n + 1;
    else
      break;
  }

  s = string_pool_insert_len(buf, n);
  free(buf);

  return s;
}