Thread: Serializing/deserializing problem

Hi, I'm using a trie for fast storing/retrieval of strings and associated value, and the trie API includes functions for de/serializing the trie. So I need to implement a save() and load() methods, that will call serialize() and deserialize() in trie.c. I'm having problems to get this working, it compiles fine, and I can serialize data to disk, but I can't deserialize data to create a trie from the file. I don't know wheter the problem is in how I write trie's data to
disk, or when I load it from disk, or both.

I copy below the code of a test program that uses the trie API, and I add links to the trie header and definitions. The program reads a file with strings (one per line) and stores them in the trie, storing a value with each string. The serialize function in trie.c will call _write_to_handle() for each key in the trie, and _write_value_to_handle() for each value associated with a key.

Code:

/* Usage:
#test -save /tmp/words.txt      read strings, store in trie, and save trie to disk.
#test -load                             load data from disk and builds a trie from it.
*/

#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include "trie.h"

#define LINESZ 1024

static int total_words = 0;
int total_values=0;

const void *value;
Trie trie;

/* Methods called when serialing trie data */
static int _write_handle(const void *towrite, const int length, void *handle)
{
    fwrite(&towrite, length, 1, (FILE *) handle);  
    return 1;	
}

static int _write_value_handle(const void *towrite, void *handle)
{
    fwrite(&towrite, sizeof(int), 1, handle);  
    return 1;
}

/* Methods called when deserialing trie data */
static int _read_handle(void *wasread, const int length, void *handle)
{   
     printf("_read_handle called. length: &#37;d\n",length);
     fread(wasread, length, 1, (FILE *) handle);   
     printf("wasread is: %s\n",wasread);   
     return 1;	
}

static void * _read_value_handle(void *handle)   //returns a pointer to the value
{
//In my tests, this method never gets called, because a problem happens with
// the data read in _read_handle(). No error given, deserialize() function just quits.
    int *value;
    printf("_read_value_handle called.");
    fread(&value, sizeof(int), 1, handle);  
    printf("value read is: %d",value);
    return value;
}

/* Methods to serialize and deserialize the trie  */
int trie_save(){   
  FILE *out = fopen("savefile.txt", "wb"); 
  int success=Trie_serialize(trie, _write_handle, _write_value_handle, (void *)out); 
  fclose(out);		   
  return success;
}

int trie_load(){ 
   int success=1;
   FILE *in = fopen("savefile.txt", "rb"); 
   trie = Trie_deserialize(_read_handle, _read_value_handle,in);
   if(!trie) {
      success=0;
      printf("Error: trie could not be created from data.\n");
  }
  fclose(in);		   
  return success;
}

int main(int argc, char **argv) {
  char s[LINESZ];
  int myval;
  
  if(!strcmp(argv[1], "-load")) { 
         int success=trie_load();
  	 printf("load sucess is: %d\n",success);
  }

  if(!strcmp(argv[1], "-save")) {
  
FILE *in = fopen(argv[2], "r");  // e.g. /tmp/words.txt 
  trie=Trie_new();
  value=(const void *)1;
  	
  if (!in) {
    perror(argv[1]);
    return 1;
  }
  while (fgets(s, LINESZ, in)) {
    int len = strlen(s);
    if (len) {
      s[len-1] = '\0';  // chop newline 
       total_words++; 
      // add to trie  //arg3 is the value
      Trie_set(trie, (const unsigned char*) s, (const void*) total_words); 
    }
  }
  fclose(in);
  
  int success=trie_save();
  printf("serialized trie success: %d\n",success);
  
  }
  fprintf(stderr, "Checked %d total words.\n", total_words);
  fprintf(stderr, "Trie length is: %d .\n", Trie_len(trie));

  Trie_del(trie);
  return 0;
}

trie.h, trie.c


I'd much appreciate any suggestions about what I'm doing wrong.

Thanks.