Commit 1ae84fcb authored by Roger Dingledine's avatar Roger Dingledine
Browse files

add a 'smartlist' building block that picks random elements from a list 


svn:r897
parent 9c66e2bf

src/common/crypto.c

+1 −0
Original line number Diff line number Diff line
@@ -1009,6 +1009,7 @@ void crypto_pseudo_rand(unsigned int n, unsigned char *to) 
  }

}



/* return a pseudo random number between 0 and max-1 */

int crypto_pseudo_rand_int(unsigned int max) {

  unsigned int val;

  unsigned int cutoff;

src/common/util.c

+49 −9
Original line number Diff line number Diff line
@@ -63,6 +63,46 @@ char *tor_strndup(const char *s, size_t n) { 
  return dup;

}



/*

 * A simple smartlist interface to make an unordered list of acceptable

 * nodes and then choose a random one.

 * smartlist_create() mallocs the list, _free() frees the list,

 * _add() adds an element, _remove() removes an element if it's there,

 * _choose() returns a random element.

 */



smartlist_t *smartlist_create(int max_elements) {

  smartlist_t *sl = tor_malloc(sizeof(smartlist_t));

  sl->list = tor_malloc(sizeof(void *) * max_elements);

  sl->num_used = 0;

  sl->max = max_elements;

  return sl;

}



void smartlist_free(smartlist_t *sl) {

  free(sl->list);

  free(sl);

}



/* add element to the list, but only if there's room */

void smartlist_add(smartlist_t *sl, void *element) {

  if(sl->num_used < sl->max)

    sl->list[sl->num_used++] = element;

}



void smartlist_remove(smartlist_t *sl, void *element) {

  int i;

  for(i=0; i < sl->num_used; i++)

    if(sl->list[i] == element)

      sl->list[i] = sl->list[--sl->num_used]; /* swap with the end */

}



void *smartlist_choose(smartlist_t *sl) {

  if(sl->num_used)

    return sl->list[crypto_pseudo_rand_int(sl->num_used)];

  return NULL; /* no elements to choose from */

}



/*

 *    String manipulation

 */

src/common/util.h

+12 −0
Original line number Diff line number Diff line
@@ -39,6 +39,18 @@ char *tor_strdup(const char *s); 
char *tor_strndup(const char *s, size_t n);

#define tor_free(p) do {if(p) {free(p); (p)=NULL;}} while(0)



typedef struct {

  void **list;

  int num_used;

  int max;

} smartlist_t;



smartlist_t *smartlist_create(int max_elements);

void smartlist_free(smartlist_t *sl);

void smartlist_add(smartlist_t *sl, void *element);

void smartlist_remove(smartlist_t *sl, void *element);

void *smartlist_choose(smartlist_t *sl);



const char *eat_whitespace(const char *s);

const char *eat_whitespace_no_nl(const char *s);

const char *find_whitespace(const char *s);