Serialization? about uthash HOT 5 CLOSED

Is there any beter way to unserialize? It has complexity O(N*logN) (I hope not worse...)

for (i = 0; i<size; i++) {
  int32 key = readNextKeyFrom(serialized)
  int32 value = readNextValueFrom(serialized)
  hashMap *s = (hashMap*)malloc(sizeof(hashMap));
  if(s == NULL){
     elog(ERROR, "malloc error!"); 
  }else{
    s->value = value;
    s->id = key;
    HASH_ADD_INT( hashmap, id, s );
  }
}

Serialized keys are sorted. Is it possible to do it with O(N)?
(N = number of serialized keys)

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@troydhanson also created a serialization library https://github.com/troydhanson/tpl, which could do it.

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I don't know any way of serializing a uthash hash other than the obvious

myserializer_serialize_beginhashtable();
HASH_ITER(myhash, cur, tmp) {
    myserializer_serialize_item(cur);
}
myserializer_serialize_endhashtable();

How to serialize each item in the hash is of course up to you; an item is just a C struct (which might contain pointers or even weirder unserializable data), so it's always going to be up to you to figure out how to serialize it correctly.

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Issue troydhanson/tpl#12 is a similar one.

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Coming by six years later to say... 😛 The complexity of the code in your last comment should be O(N), since you're just doing the loop N times, and inside the loop all you're doing is malloc'ing a new item (O(1), slow) and adding it into the hash (O(1), fast). There shouldn't be any log-N operations happening in there.

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