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3 (C) 2001, 2002, 2003, 2004, 2006, 2008 Christian Grothoff (and other contributing authors)
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21 * @file util/container_bloomfilter.c
22 * @brief data structure used to reduce disk accesses.
24 * The idea basically: Create a signature for each element in the
25 * database. Add those signatures to a bit array. When doing a lookup,
26 * check if the bit array matches the signature of the requested
27 * element. If yes, address the disk, otherwise return 'not found'.
29 * A property of the bloom filter is that sometimes we will have
30 * a match even if the element is not on the disk (then we do
31 * an unnecessary disk access), but what's most important is that
32 * we never get a single "false negative".
34 * To be able to delete entries from the bloom filter, we maintain
35 * a 4 bit counter in the file on the drive (we still use only one
38 * @author Igor Wronsky
39 * @author Christian Grothoff
43 #include "gnunet_common.h"
44 #include "gnunet_container_lib.h"
45 #include "gnunet_disk_lib.h"
47 struct GNUNET_CONTAINER_BloomFilter
51 * The actual bloomfilter bit array
56 * Filename of the filter
61 * The bit counter file on disk
63 struct GNUNET_DISK_FileHandle *fh;
66 * How many bits we set for each stored element
68 unsigned int addressesPerElement;
71 * Size of bitArray in bytes
79 * Sets a bit active in the bitArray. Increment bit-specific
80 * usage counter on disk only if below 4bit max (==15).
82 * @param bitArray memory area to set the bit in
83 * @param bitIdx which bit to set
86 setBit (char *bitArray, unsigned int bitIdx)
89 unsigned int targetBit;
91 arraySlot = bitIdx / 8;
92 targetBit = (1L << (bitIdx % 8));
93 bitArray[arraySlot] |= targetBit;
97 * Clears a bit from bitArray. Bit is cleared from the array
98 * only if the respective usage counter on the disk hits/is zero.
100 * @param bitArray memory area to set the bit in
101 * @param bitIdx which bit to unset
104 clearBit (char *bitArray, unsigned int bitIdx)
107 unsigned int targetBit;
110 targetBit = (1L << (bitIdx % 8));
111 bitArray[slot] = bitArray[slot] & (~targetBit);
115 * Checks if a bit is active in the bitArray
117 * @param bitArray memory area to set the bit in
118 * @param bitIdx which bit to test
119 * @return GNUNET_YES if the bit is set, GNUNET_NO if not.
122 testBit (char *bitArray, unsigned int bitIdx)
125 unsigned int targetBit;
128 targetBit = (1L << (bitIdx % 8));
129 if (bitArray[slot] & targetBit)
136 * Sets a bit active in the bitArray and increments
137 * bit-specific usage counter on disk (but only if
138 * the counter was below 4 bit max (==15)).
140 * @param bitArray memory area to set the bit in
141 * @param bitIdx which bit to test
142 * @param fh A file to keep the 4 bit address usage counters in
145 incrementBit (char *bitArray, unsigned int bitIdx,
146 const struct GNUNET_DISK_FileHandle *fh)
152 unsigned int targetLoc;
154 setBit (bitArray, bitIdx);
155 if (GNUNET_DISK_handle_invalid (fh))
157 /* Update the counter file on disk */
158 fileSlot = bitIdx / 2;
159 targetLoc = bitIdx % 2;
161 GNUNET_assert (fileSlot ==
162 GNUNET_DISK_file_seek (fh, fileSlot, GNUNET_DISK_SEEK_SET));
163 if (1 != GNUNET_DISK_file_read (fh, &value, 1))
166 high = (value & (~0xF)) >> 4;
178 value = ((high << 4) | low);
179 GNUNET_assert (fileSlot == GNUNET_DISK_file_seek (fh,
181 GNUNET_DISK_SEEK_SET));
182 GNUNET_assert (1 == GNUNET_DISK_file_write (fh, &value, 1));
186 * Clears a bit from bitArray if the respective usage
187 * counter on the disk hits/is zero.
189 * @param bitArray memory area to set the bit in
190 * @param bitIdx which bit to test
191 * @param fh A file to keep the 4bit address usage counters in
194 decrementBit (char *bitArray, unsigned int bitIdx,
195 const struct GNUNET_DISK_FileHandle *fh)
201 unsigned int targetLoc;
203 if (GNUNET_DISK_handle_invalid (fh))
204 return; /* cannot decrement! */
205 /* Each char slot in the counter file holds two 4 bit counters */
206 fileSlot = bitIdx / 2;
207 targetLoc = bitIdx % 2;
208 GNUNET_DISK_file_seek (fh, fileSlot, GNUNET_DISK_SEEK_SET);
209 if (1 != GNUNET_DISK_file_read (fh, &value, 1))
212 high = (value & 0xF0) >> 4;
214 /* decrement, but once we have reached the max, never go back! */
217 if ((low > 0) && (low < 0xF))
221 clearBit (bitArray, bitIdx);
226 if ((high > 0) && (high < 0xF))
230 clearBit (bitArray, bitIdx);
233 value = ((high << 4) | low);
234 GNUNET_DISK_file_seek (fh, fileSlot, GNUNET_DISK_SEEK_SET);
235 GNUNET_assert (1 == GNUNET_DISK_file_write (fh, &value, 1));
238 #define BUFFSIZE 65536
241 * Creates a file filled with zeroes
243 * @param fh the file handle
244 * @param size the size of the file
245 * @return GNUNET_OK if created ok, GNUNET_SYSERR otherwise
248 makeEmptyFile (const struct GNUNET_DISK_FileHandle *fh, size_t size)
251 size_t bytesleft = size;
254 if (GNUNET_DISK_handle_invalid (fh))
255 return GNUNET_SYSERR;
256 buffer = GNUNET_malloc (BUFFSIZE);
257 memset (buffer, 0, BUFFSIZE);
258 GNUNET_DISK_file_seek (fh, 0, GNUNET_DISK_SEEK_SET);
260 while (bytesleft > 0)
262 if (bytesleft > BUFFSIZE)
264 res = GNUNET_DISK_file_write (fh, buffer, BUFFSIZE);
265 bytesleft -= BUFFSIZE;
269 res = GNUNET_DISK_file_write (fh, buffer, bytesleft);
272 GNUNET_assert (res != GNUNET_SYSERR);
274 GNUNET_free (buffer);
278 /* ************** GNUNET_CONTAINER_BloomFilter iterator ********* */
281 * Iterator (callback) method to be called by the
282 * bloomfilter iterator on each bit that is to be
283 * set or tested for the key.
286 * @param bf the filter to manipulate
287 * @param bit the current bit
289 typedef void (*BitIterator) (void *cls,
290 struct GNUNET_CONTAINER_BloomFilter * bf,
294 * Call an iterator for each bit that the bloomfilter
295 * must test or set for this element.
297 * @param bf the filter
298 * @param callback the method to call
299 * @param arg extra argument to callback
300 * @param key the key for which we iterate over the BF bits
303 iterateBits (struct GNUNET_CONTAINER_BloomFilter *bf,
304 BitIterator callback, void *arg, const GNUNET_HashCode * key)
306 GNUNET_HashCode tmp[2];
309 unsigned int slot = 0;
311 bitCount = bf->addressesPerElement;
312 memcpy (&tmp[0], key, sizeof (GNUNET_HashCode));
316 while (slot < (sizeof (GNUNET_HashCode) / sizeof (uint32_t)))
320 (((uint32_t *) & tmp[round & 1])[slot]) &
321 ((bf->bitArraySize * 8) - 1));
329 GNUNET_CRYPTO_hash (&tmp[round & 1], sizeof (GNUNET_HashCode),
330 &tmp[(round + 1) & 1]);
338 * Callback: increment bit
340 * @param cls not used
341 * @param bf the filter to manipulate
342 * @param bit the bit to increment
345 incrementBitCallback (void *cls,
346 struct GNUNET_CONTAINER_BloomFilter *bf,
349 incrementBit (bf->bitArray, bit, bf->fh);
353 * Callback: decrement bit
355 * @param cls not used
356 * @param bf the filter to manipulate
357 * @param bit the bit to decrement
360 decrementBitCallback (void *cls,
361 struct GNUNET_CONTAINER_BloomFilter *bf,
364 decrementBit (bf->bitArray, bit, bf->fh);
368 * Callback: test if all bits are set
370 * @param cls pointer set to GNUNET_NO if bit is not set
371 * @param bf the filter
372 * @param bit the bit to test
375 testBitCallback (void *cls,
376 struct GNUNET_CONTAINER_BloomFilter *bf, unsigned int bit)
379 if (GNUNET_NO == testBit (bf->bitArray, bit))
383 /* *********************** INTERFACE **************** */
386 * Load a bloom-filter from a file.
388 * @param filename the name of the file (or the prefix)
389 * @param size the size of the bloom-filter (number of
390 * bytes of storage space to use)
391 * @param k the number of GNUNET_CRYPTO_hash-functions to apply per
392 * element (number of bits set per element in the set)
393 * @return the bloomfilter
395 struct GNUNET_CONTAINER_BloomFilter *
396 GNUNET_CONTAINER_bloomfilter_load (const char *filename,
397 size_t size, unsigned int k)
399 struct GNUNET_CONTAINER_BloomFilter *bf;
405 if ((k == 0) || (size == 0))
412 size = ui; /* make sure it's a power of 2 */
414 bf = GNUNET_malloc (sizeof (struct GNUNET_CONTAINER_BloomFilter));
415 /* Try to open a bloomfilter file */
416 if (filename != NULL)
418 bf->fh = GNUNET_DISK_file_open (filename, GNUNET_DISK_OPEN_READWRITE
419 | GNUNET_DISK_OPEN_CREATE,
420 GNUNET_DISK_PERM_USER_READ |
421 GNUNET_DISK_PERM_USER_WRITE);
427 bf->filename = GNUNET_strdup (filename);
435 bf->bitArray = GNUNET_malloc_large (size);
436 bf->bitArraySize = size;
437 bf->addressesPerElement = k;
438 memset (bf->bitArray, 0, bf->bitArraySize);
440 if (bf->filename != NULL)
442 /* Read from the file what bits we can */
443 rbuff = GNUNET_malloc (BUFFSIZE);
445 while (pos < size * 8)
449 res = GNUNET_DISK_file_read (bf->fh, rbuff, BUFFSIZE);
452 GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING,
453 "read", bf->filename);
456 break; /* is ok! we just did not use that many bits yet */
457 for (i = 0; i < res; i++)
459 if ((rbuff[i] & 0x0F) != 0)
460 setBit (bf->bitArray, pos + i * 2);
461 if ((rbuff[i] & 0xF0) != 0)
462 setBit (bf->bitArray, pos + i * 2 + 1);
466 pos += BUFFSIZE * 2; /* 2 bits per byte in the buffer */
475 * Create a bloom filter from raw bits.
477 * @param data the raw bits in memory (maybe NULL,
478 * in which case all bits should be considered
480 * @param size the size of the bloom-filter (number of
481 * bytes of storage space to use); also size of data
482 * -- unless data is NULL
483 * @param k the number of GNUNET_CRYPTO_hash-functions to apply per
484 * element (number of bits set per element in the set)
485 * @return the bloomfilter
487 struct GNUNET_CONTAINER_BloomFilter *
488 GNUNET_CONTAINER_bloomfilter_init (const char *data,
489 size_t size, unsigned int k)
491 struct GNUNET_CONTAINER_BloomFilter *bf;
494 if ((k == 0) || (size == 0))
504 bf = GNUNET_malloc (sizeof (struct GNUNET_CONTAINER_BloomFilter));
507 bf->bitArray = GNUNET_malloc_large (size);
508 bf->bitArraySize = size;
509 bf->addressesPerElement = k;
511 memcpy (bf->bitArray, data, size);
513 memset (bf->bitArray, 0, bf->bitArraySize);
519 * Copy the raw data of this bloomfilter into
520 * the given data array.
522 * @param bf bloomfilter to take the raw data from
523 * @param data where to write the data
524 * @param size the size of the given data array
525 * @return GNUNET_SYSERR if the data array is not big enough
528 GNUNET_CONTAINER_bloomfilter_get_raw_data (struct GNUNET_CONTAINER_BloomFilter
529 *bf, char *data, size_t size)
532 return GNUNET_SYSERR;
534 if (bf->bitArraySize != size)
535 return GNUNET_SYSERR;
536 memcpy (data, bf->bitArray, size);
541 * Free the space associated with a filter
542 * in memory, flush to drive if needed (do not
543 * free the space on the drive)
545 * @param bf the filter
548 GNUNET_CONTAINER_bloomfilter_free (struct GNUNET_CONTAINER_BloomFilter *bf)
553 GNUNET_DISK_file_close (bf->fh);
554 GNUNET_free_non_null (bf->filename);
555 GNUNET_free (bf->bitArray);
560 * Reset a bloom filter to empty. Clears the file on disk.
562 * @param bf the filter
565 GNUNET_CONTAINER_bloomfilter_clear (struct GNUNET_CONTAINER_BloomFilter *bf)
570 memset (bf->bitArray, 0, bf->bitArraySize);
571 if (bf->filename != NULL)
572 makeEmptyFile (bf->fh, bf->bitArraySize * 4);
577 * Test if an element is in the filter.
579 * @param e the element
580 * @param bf the filter
581 * @return GNUNET_YES if the element is in the filter, GNUNET_NO if not
584 GNUNET_CONTAINER_bloomfilter_test (struct GNUNET_CONTAINER_BloomFilter *bf,
585 const GNUNET_HashCode * e)
592 iterateBits (bf, &testBitCallback, &res, e);
597 * Add an element to the filter
599 * @param bf the filter
600 * @param e the element
603 GNUNET_CONTAINER_bloomfilter_add (struct GNUNET_CONTAINER_BloomFilter *bf,
604 const GNUNET_HashCode * e)
609 iterateBits (bf, &incrementBitCallback, NULL, e);
614 * Or the entries of the given raw data array with the
615 * data of the given bloom filter. Assumes that
616 * the size of the data array and the current filter
619 * @param bf the filter
620 * @param data the data to or-in
621 * @param size number of bytes in data
624 GNUNET_CONTAINER_bloomfilter_or (struct GNUNET_CONTAINER_BloomFilter *bf,
625 const char *data, size_t size)
629 unsigned long long* fc;
630 const unsigned long long* dc;
634 if (bf->bitArraySize != size)
635 return GNUNET_SYSERR;
636 fc = (unsigned long long*) bf->bitArray;
637 dc = (const unsigned long long*) data;
638 n = size / sizeof (unsigned long long);
640 for (i = 0; i < n; i++)
642 for (i = n * sizeof(unsigned long long); i < size; i++)
643 bf->bitArray[i] |= data[i]
648 * Remove an element from the filter.
650 * @param bf the filter
651 * @param e the element to remove
654 GNUNET_CONTAINER_bloomfilter_remove (struct GNUNET_CONTAINER_BloomFilter *bf,
655 const GNUNET_HashCode * e)
659 if (bf->filename == NULL)
661 iterateBits (bf, &decrementBitCallback, NULL, e);
665 * Resize a bloom filter. Note that this operation
666 * is pretty costly. Essentially, the bloom filter
667 * needs to be completely re-build.
669 * @param bf the filter
670 * @param iterator an iterator over all elements stored in the BF
671 * @param iterator_cls argument to the iterator function
672 * @param size the new size for the filter
673 * @param k the new number of GNUNET_CRYPTO_hash-function to apply per element
676 GNUNET_CONTAINER_bloomfilter_resize (struct GNUNET_CONTAINER_BloomFilter *bf,
677 GNUNET_HashCodeIterator iterator,
679 size_t size, unsigned int k)
684 GNUNET_free (bf->bitArray);
688 size = i; /* make sure it's a power of 2 */
690 bf->bitArraySize = size;
691 bf->bitArray = GNUNET_malloc (size);
692 memset (bf->bitArray, 0, bf->bitArraySize);
693 if (bf->filename != NULL)
694 makeEmptyFile (bf->fh, bf->bitArraySize * 4);
695 while (GNUNET_YES == iterator (iterator_cls, &hc))
696 GNUNET_CONTAINER_bloomfilter_add (bf, &hc);
699 /* end of container_bloomfilter.c */