Minecraft strings

mcstring.c

#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <pthread.h>

#include <event2/buffer.h>

#include "craftd-config.h"
#include "util.h"

/**
 * Check if str is valid MC UTF-8, nonzero otherwise
 * @param str string to check
 * @return 0 if valid, nonzero otherwise
 */
int
ismc_utf8(const char *const str)
{ 
  const char *const MC_UTF8 = 
  "\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_'abcdefgh"
  "ijklmnopqrstuvwxyz{|}~.ÇüéâäàåçêëèïîìÄÅÉæÆôöòûùÿÖÜø£Ø×.áíóúñѪº¿®¬½¼¡«»";

  if( strspn(str, MC_UTF8) == strlen(str) )
    return 0;
  return EBADMSG;
}

/*
 * MC Strings always have known lengths.  Take advantage of this and try to
 * create infallible strings.  Critique and review of this code needed.
 */

/**
 * Create an mcstring from a slen and character array.  The character array does
 * not need to be null terminated, but slen MUST EQUAL the number of characters
 * not including a NUL terminator.  strlen provides this behavior for internal
 * C strings.
 *
 * If the string needs to be reader/writer locked for use in reentrant
 * functions, pass in an initialized rwlock.  The lock and the input string
 * arg need to be manually freed when finished.
 *
 * @param slen string length, not including NUL terminator
 * @param strptr input string
 * @param rwlock a reader/writer lock if necessary
 * @return a ptr to an mcstring structure or null
 */
mcstring_t *
mcstring_create(int16_t slen, char *strptr, pthread_rwlock_t rwlock)
{
  if (slen > MC_MAXSTRING)
    goto err; // LOG bad string

  char *strin;
  strin = (char *)Malloc(slen+1);
  /* NUL terminate the end.  If strnlen doesn't match slen, something
   * strange is going on with the client.
   */
  strin[slen] = '\0';
  memcpy(strin, strptr, slen);

  if (strlen(strin) != slen)
    goto err; // LOG bad string

  if (!ismc_utf8(strin))
    goto err; // LOG bad string

  mcstring_t *mcstring;
  mcstring = (mcstring_t *)Malloc(sizeof(mcstring_t));
  mcstring->slen = slen;
  mcstring->str = strin;
  mcstring->rwlock = rwlock;
  
  /* return a valid mcstring construction */
  return mcstring;

err:
  if(strin)
    free(strin);

  return NULL;
}

//TODO mcstring cat

/**
 * Free an mcstring instance.
 *
 * Make sure to destroy the rwlock first if it exists.
 *
 * @param mcstring string to free
 */
void
mcstring_free(mcstring_t * mcstring)
{
  free(mcstring->str);
  free(mcstring);
}