File: hashing.c

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pgn-extract 16.0-1
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/*
 *  Program: pgn-extract: a Portable Game Notation (PGN) extractor.
 *  Copyright (C) 1994-2005 David Barnes
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 1, or (at your option)
 *  any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *  David Barnes may be contacted as D.J.Barnes@kent.ac.uk
 *  http://www.cs.kent.ac.uk/people/staff/djb/
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#ifdef __BORLANDC__
/* For unlink() */
#include <io.h>
#else
/* For unlink() */
#include <unistd.h>
#endif
#include "bool.h"
#include "mymalloc.h"
#include "defs.h"
#include "typedef.h"
#include "tokens.h"
#include "taglist.h"
#include "lex.h"
#include "hashing.h"

		/* Routines, similar in nature to those in apply.c
		 * to implement a duplicate hash-table lookup using
		 * an external file, rather than malloc'd memory.
		 * The only limit should be a file system limit.
		 *
		 * This version should be slightly more accurate than
		 * the alternative because the final_ and cumulative_
		 * hash values are both stored, rather than the XOR
		 * of them.
		 */

/* The name of the file used.
 * This is overwritten each time, and removed on normal
 * program exit.
 */
static char VIRTUAL_FILE[] = "virtual.tmp";

/* Define a table to hold hash values of the extracted games.
 * This is used to enable duplicate detection.
 */
#define LOG_TABLE_SIZE 8191
typedef struct{
    /* Record the file offset of the first and last entries
     * for an index. (head == -1) => empty.
     */
  long head, tail;
} LogHeaderEntry;

/* If use_virtual_hash_table */
static LogHeaderEntry *VirtualLogTable = NULL;

/* Define a table to hold hash values of the extracted games.
 * This is used to enable duplicate detection when not using
 * the virtual hash table.
 */
static HashLog **LogTable = NULL;

	/* Define a type to hold hash values of interest.
	 * This is used both to aid in duplicate detection
	 * and in finding positional variations.
	 */
typedef struct VirtualHashLog {
    /* Store the final position hash value and
     * the cumulative hash value for a game.
     */
    HashCode final_hash_value, cumulative_hash_value;
    /* Record the file list index for the file this game was first found in. */
    int file_number;
    /* Record the file offset of the next element
     * in this list. -1 => end-of-list.
     */
    long next;
} VirtualHashLog;

static FILE *hash_file = NULL;

static const char *previous_virtual_occurance(Game game_details);
	
	/* Determine which table to initialise, depending
	 * on whether use_virtual_hash_table is set or not.
	 */
void
init_duplicate_hash_table(void)
{  int i;

   if(GlobalState.use_virtual_hash_table){
       VirtualLogTable = (LogHeaderEntry *)
	    MallocOrDie(LOG_TABLE_SIZE*sizeof(*VirtualLogTable));
       for(i = 0; i < LOG_TABLE_SIZE; i++){
	   VirtualLogTable[i].head = VirtualLogTable[i].tail = -1;
       }
       hash_file = fopen(VIRTUAL_FILE,"w+b");
       if(hash_file == NULL){
	   fprintf(GlobalState.logfile,"Unable to open %s\n",
		    VIRTUAL_FILE);
       }
    }
    else{
       LogTable = (HashLog**) MallocOrDie(LOG_TABLE_SIZE*sizeof(*LogTable));
       for(i = 0; i < LOG_TABLE_SIZE; i++){
	   LogTable[i] = NULL;
       }
    }
}

	/* Close and remove the temporary file if in use. */
void
clear_duplicate_hash_table(void)
{
   if(GlobalState.use_virtual_hash_table){
      if(hash_file != NULL){
	(void) fclose(hash_file);
	unlink(VIRTUAL_FILE);
      }
   }
}

	/* Retrieve a duplicate table entry from the hash file. */
static int
retrieve_virtual_entry(long ix,VirtualHashLog *entry)
{
    if(hash_file == NULL){
	return 0;
    }
    else if(fseek(hash_file,ix,SEEK_SET) != 0){
	fprintf(GlobalState.logfile,
			"Fseek error to %ld in retrieve_virtual_entry\n",ix);
	return 0;
    }
    else if(fread((void *)entry,sizeof(*entry),1,hash_file) != 1){
	fprintf(GlobalState.logfile,
			"Fread error from %ld in retrieve_virtual_entry\n",ix);
	return 0;
    }
    else{
	return 1;
    }
}

	/* Write a duplicate table entry to the hash file. */
static int
write_virtual_entry(long where,const VirtualHashLog *entry)
{
    if(fseek(hash_file,where,SEEK_SET) != 0){
	fprintf(GlobalState.logfile,
		"Fseek error to %ld in write_virtual_entry\n",where);
	return 0;
    }
    else if(fwrite((void *)entry,sizeof(*entry),1,hash_file) != 1){
	fprintf(GlobalState.logfile,
		"Fwrite error from %ld in write_virtual_entry\n",where);
	return 0;
    }
    else{
	/* Written ok. */
	return 1;
    }
}

	/* Return the name of the original file if it looks like we
	 * have met the moves in game_details before, otherwise return
	 * NULL.  A match is assumed to be so if both
	 * the final_ and cumulative_ hash values in game_details
	 * are already present in VirtualLogTable.
	 */
static const char *
previous_virtual_occurance(Game game_details)
{   unsigned ix = game_details.final_hash_value % LOG_TABLE_SIZE;
    VirtualHashLog entry;
    Boolean duplicate = FALSE;
    const char *original_filename = NULL;


    /* Are we keeping this information? */
    if(GlobalState.suppress_duplicates || GlobalState.suppress_originals ||
		GlobalState.duplicate_file != NULL){
      if(VirtualLogTable[ix].head < 0l){
	/* First occurrence. */
      }
      else{
	int keep_going =
		retrieve_virtual_entry(VirtualLogTable[ix].head,&entry);

	while(keep_going && !duplicate){
	    if((entry.final_hash_value == game_details.final_hash_value) &&
	       (entry.cumulative_hash_value == game_details.cumulative_hash_value)){
		/* We have a match.
		 * Determine where it first occured.
		 */
		original_filename = input_file_name(entry.file_number);
		duplicate = TRUE;
	    }
	    else if(entry.next >= 0l){
	       keep_going = retrieve_virtual_entry(entry.next,&entry);
	    }
	    else{
	       keep_going = 0;
	    }
	}
      }

      if(!duplicate){
	/* Write an entry for it. */
	/* Where to write the next VirtualHashLog entry. */
	static long next_free_entry = 0l;

	/* Store the XOR of the two hash values. */
	entry.final_hash_value = game_details.final_hash_value ;
	entry.cumulative_hash_value = game_details.cumulative_hash_value;
	entry.file_number = current_file_number();
	entry.next = -1l;

	/* Write out these details. */
	if(write_virtual_entry(next_free_entry,&entry)){
	    long where_written = next_free_entry;
	    /* Move on ready for next time. */
	    next_free_entry += sizeof(entry);

	    /* Now update the index table. */
	    if(VirtualLogTable[ix].head < 0l){
		/* First occurrence. */
		VirtualLogTable[ix].head =
			VirtualLogTable[ix].tail = where_written;
	    }
	    else{
		VirtualHashLog tail;

		if(retrieve_virtual_entry(VirtualLogTable[ix].tail,&tail)){
		    tail.next = where_written;
		    (void) write_virtual_entry(VirtualLogTable[ix].tail,&tail);
		    /* Store the new tail address. */
		    VirtualLogTable[ix].tail = where_written;
		}
	    }
	}
      }
    }
    return original_filename;
}

	/* Return the name of the original file if it looks like we
	 * have met the moves in game_details before, otherwise return
	 * NULL.  A match is assumed to be so if both
	 * the final_ and cumulative_ hash values in game_details
	 * are already present in LogTable.
	 */
const char *
previous_occurance(Game game_details)
{
  const char *original_filename = NULL;
  if(GlobalState.use_virtual_hash_table){
    original_filename = previous_virtual_occurance(game_details);
  }
  else{
    unsigned ix = game_details.final_hash_value % LOG_TABLE_SIZE;
    HashLog *entry = NULL;
    Boolean duplicate = FALSE;

    /* Are we keeping this information? */
    if(GlobalState.suppress_duplicates || GlobalState.suppress_originals ||
		GlobalState.duplicate_file != NULL){
	for(entry = LogTable[ix]; !duplicate && (entry != NULL);
					entry = entry->next){
	    if(entry->combined_hash_value ==
			(game_details.final_hash_value ^
					game_details.cumulative_hash_value)){
		/* We have a match.
		 * Determine where it first occured.
		 */
		original_filename = input_file_name(entry->file_number);
		duplicate = TRUE;
	    }
	}

	if(!duplicate){
	    /* First occurrence, so add it to the log. */
	    entry = (HashLog *)MallocOrDie(sizeof(*entry));

	    /* Store the XOR of the two hash values. */
	    entry->combined_hash_value =
		game_details.final_hash_value ^ game_details.cumulative_hash_value;
	    entry->file_number = current_file_number();
	    /* Link it into the head at this index. */
	    entry->next =  LogTable[ix];
	    LogTable[ix] = entry;
	}
    }
  }
  return original_filename;
}