509:
36:
1180:, often a function is used that has a large domain. To create an index from the output of the function, a modulo can be taken to reduce the size of the domain to match the size of the array; however, it is often faster on many processors to restrict the size of the hash table to powers of two sizes and use a bitmask instead.
830:
The advantage to this approach is that function argument overhead is decreased. Since the minimum datum size is one byte, separating the options into separate arguments would be wasting seven bits per argument and would occupy more stack space. Instead, functions typically accept one or more 32-bit
863:
Masks are used with IP addresses in IP ACLs (Access
Control Lists) to specify what should be permitted and denied. To configure IP addresses on interfaces, masks start with 255 and have the large values on the left side: for example, IP address
1118:, in which the correspondent image areas are given a pixel value of all bits set to 0s and the surrounding areas a value of all bits set to 1s. In the sample at right, black pixels have the all-zero bits and white pixels have the all-one bits.
405:
So far the article has covered how to turn bits on and turn bits off, but not both at once. Sometimes it does not really matter what the value is, but it must be made the opposite of what it currently is. This can be achieved using the
1140:
363:, then the bit was off, but if the value is any other value, then the bit was on. What makes this convenient is that it is not necessary to figure out what the value actually is, just that it is not
1136:
operation. This way, the image pixels are appropriately placed while keeping the background surrounding pixels preserved. The result is a perfect compound of the image over the background.
936:) must match the given binary network address exactly (11000000.00000000.00000010). The last set of numbers is made of "don't cares" (.11111111). Therefore, all traffic that begins with "
1102:, when a given image is intended to be placed over a background, the transparent areas can be specified through a binary mask. This way, for each intended image there are actually two
1085:
1129:
operation. This preserves the background pixels of the transparent areas while resets with zeros the bits of the pixels which will be obscured by the overlapped image.
512:
A party trick to guess a number from which cards it is printed on uses the bits of the binary representation of the number. In the SVG file, click a card to toggle it.
351:
It is possible to use bitmasks to easily check the state of individual bits regardless of the other bits. To do this, turning off all the other bits using the bitwise
1157:, and for video titling and other image mixing applications. A faster method is to simply overwrite the background pixels with the foreground pixels if their alpha=1
892:. When the value of the mask is broken down into binary (0s and 1s), the results determine which address bits are to be considered in processing the traffic. A
1125:, to put the image on the screen over the background, the program first masks the screen pixel's bits with the image mask at the desired coordinates using the
172:, where the bitmask is used to select which element operations in the vector are to be executed (mask bit is enabled) and which are not (mask bit is clear).
855:
an alternative would be to create a class to encapsulate the set of arguments that glClear could accept and could be cleanly encapsulated in a library.
164:, etc. can be set either on or off, or inverted from on to off (or vice versa) in a single bitwise operation. An additional use of masking involves
46:
1146:
This technique is used for painting pointing device cursors, in typical 2-D videogames for characters, bullets and so on (the
104:
76:
165:
1161:
1122:
525:, bit fields are a useful way to pass a set of named boolean arguments to a function. For example, in the graphics API
83:
979:
in order to determine the ACL inverse mask. In this example, the inverse mask is determined for network address
831:
integers, with up to 32 option bits in each. While elegant, in the simplest implementation this solution is not
90:
533:
which clears the screen or other buffers. It can clear up to four buffers (the color, depth, accumulation, and
61:
1132:
Then, the program renders the image pixel's bits by combining them with the background pixel's bits using the
196:
161:
72:
497:
To write arbitrary 1s and 0s to a subset of bits, first write 0s to that subset, then set the high bits:
1549:
1147:
1091:
508:
1518:
537:), so the API authors could have had it take four arguments. But then a call to it would look like
126:
17:
944:" matches, since the last octet is "don't care". Therefore, with this mask, network addresses
97:
1468:
57:
8:
1133:
189:
1139:
1483:
1099:
933:
169:
145:
1478:
1154:
133:
1088:
1493:
534:
421:
317:(bits 4, 5, 6, 7) while leaving the lower nibble (bits 0, 1, 2, 3) unchanged.
234:(bits 4, 5, 6, 7) while leaving the lower nibble (bits 0, 1, 2, 3) unchanged.
1168:
are techniques which do not involve the image pixel mixage by binary masking.
1543:
1463:
1165:
1079:
900:-bit in the mask is a "don't care". This table further explains the concept.
889:
572:// This is not how glClear actually works and would make for unstable code.
522:
476:
masking is bit-safe, meaning that it will not affect unmasked bits because
407:
577:
which is not very descriptive. Instead there are four defined field bits,
53:
1126:
832:
896:-bit indicates that the address bit must be considered (exact match); a
1177:
425:
1473:
149:
932:
Based on the binary mask, it can be seen that the first three sets (
35:
1075:
651:
to extract the individual bits. For example, an implementation of
647:
Internally, a function taking a bitfield like this can use binary
1488:
1103:
526:
314:
295:. To leave the other bits as they were originally, they can be
231:
157:
926:
network address (binary): 11000000.00000000.00000010.00000000
1498:
1107:
852:
1160:
Although related (due to being used for the same purposes),
1106:: the actual image, in which the unused areas are given a
1084:
880:
mask. Masks for IP ACLs are the reverse: for example, mask
153:
355:
is done as discussed above and the value is compared with
1151:
1111:
448:. Therefore inversion of the values of bits is done by
125:"Signal masking" redirects here. For other uses, see
843:, so the compiler would allow a meaningless call to
929:mask (binary): 00000000.00000000.00000000.11111111
906:network address (traffic that is to be processed):
1541:
888:. This is sometimes called an inverse mask or a
346:
500:register = (register & ~bitmask) | value;
1305:// Handle memory allocation for token_array…
1183:An example of both modulo and masking in C:
622:Then a call to the function looks like this
370:Example: Querying the status of the 4th bit
62:introducing citations to additional sources
432:. Therefore, if two corresponding bits are
175:
291:ed with a 0, the result is always 0, i.e.
516:
271:More often in practice, bits are "masked
1083:
507:
52:Relevant discussion may be found on the
207:. Therefore, to make sure a bit is on,
14:
1542:
400:
1440:// Free the memory from token_array …
263:
180:
29:
1176:To create a hashing function for a
503:
152:. Using a mask, multiple bits in a
24:
1138:
25:
1561:
521:In programming languages such as
195:operation can be used, following
858:
45:relies largely or entirely on a
34:
27:Data used for bitwise operations
1317:"some hashable value"
1511:
1171:
1069:
1027:The source/source-wildcard of
971:Subtract the normal mask from
13:
1:
1504:
1114:set to 0s, and an additional
783:// Clear accumulation buffer.
487:Example: Toggling bit values
440:, but if only one of them is
188:To turn certain bits on, the
347:Querying the status of a bit
215:. To leave a bit unchanged,
7:
1457:
839:is simply defined to be an
10:
1566:
1073:
464:. If the original bit was
456:. If the original bit was
124:
144:is data that is used for
1519:"Mask R-CNN with OpenCV"
1185:
1094:(left) and masks (right)
819:// Clear stencil buffer.
657:
624:
599:
539:
490:10011101 10010101 XOR
176:Common bitmask functions
127:Masking (disambiguation)
1044:The source/wildcard of
436:, the result will be a
1143:
1095:
987:with a normal mask of
747:// Clear depth buffer.
711:// Clear color buffer.
529:, there is a command,
517:Arguments to functions
513:
494:= 10010010 01101010
1142:
1087:
1058:is the same as "host
801:GL_STENCIL_BUFFER_BIT
591:GL_STENCIL_BUFFER_BIT
511:
444:, the result will be
73:"Mask" computing
1469:Binary-coded decimal
359:. If it is equal to
148:, particularly in a
58:improve this article
765:GL_ACCUM_BUFFER_BIT
729:GL_DEPTH_BUFFER_BIT
693:GL_COLOR_BUFFER_BIT
639:GL_DEPTH_BUFFER_BIT
633:GL_COLOR_BUFFER_BIT
587:GL_ACCUM_BUFFER_BIT
583:GL_DEPTH_BUFFER_BIT
579:GL_COLOR_BUFFER_BIT
492:00001111 11111111
401:Toggling bit values
211:can be used with a
1162:transparent colors
1144:
1096:
849:glClear(GL_POINTS)
514:
146:bitwise operations
1550:Binary arithmetic
1484:Bitwise operation
1100:computer graphics
968:) are processed.
655:might look like:
472:. Also note that
309:Example: Masking
287:). When a bit is
226:Example: Masking
170:vector processing
123:
122:
108:
16:(Redirected from
1557:
1534:
1533:
1531:
1530:
1515:
1479:Bit manipulation
1453:
1450:
1447:
1444:
1441:
1438:
1435:
1432:
1429:
1426:
1423:
1420:
1417:
1414:
1411:
1408:
1405:
1402:
1399:
1396:
1393:
1390:
1389:// Using bitmask
1387:
1384:
1381:
1378:
1375:
1372:
1369:
1366:
1363:
1360:
1357:
1354:
1351:
1348:
1345:
1342:
1339:
1336:
1333:
1330:
1327:
1324:
1321:
1318:
1315:
1312:
1309:
1306:
1303:
1300:
1297:
1294:
1291:
1288:
1285:
1282:
1279:
1276:
1273:
1270:
1267:
1264:
1261:
1258:
1255:
1252:
1249:
1246:
1243:
1240:
1237:
1234:
1231:
1228:
1225:
1222:
1219:
1216:
1213:
1210:
1207:
1204:
1201:
1198:
1197:<string.h>
1195:
1192:
1191:<stdint.h>
1189:
1064:
1063:
1056:
1055:
1052:
1049:
1039:
1038:
1035:
1032:
1024:ACL equivalents
1019:
1018:
1013:(normal mask) =
1011:
1010:
1003:
1002:
993:
992:
985:
984:
977:
976:
966:
965:
958:
957:
950:
949:
942:
941:
922:
921:
912:
911:
886:
885:
878:
877:
870:
869:
850:
846:
842:
838:
826:
823:
820:
817:
814:
811:
808:
805:
802:
799:
796:
793:
790:
787:
784:
781:
778:
775:
772:
769:
766:
763:
760:
757:
754:
751:
748:
745:
742:
739:
736:
733:
730:
727:
724:
721:
718:
715:
712:
709:
706:
703:
700:
697:
694:
691:
688:
685:
682:
679:
676:
673:
670:
667:
664:
661:
654:
650:
643:
640:
637:
634:
631:
628:
618:
615:
612:
609:
606:
603:
596:
592:
588:
584:
580:
573:
570:
567:
564:
561:
558:
555:
552:
549:
546:
543:
532:
504:Uses of bitmasks
483:
479:
475:
471:
467:
463:
459:
455:
452:ing them with a
451:
447:
443:
439:
435:
431:
420:
416:
410:
366:
362:
358:
354:
306:
302:
298:
294:
290:
286:
283:" (or masked to
278:
275:" (or masked to
267:
264:Masking bits to
222:
218:
214:
210:
206:
202:
193:
184:
181:Masking bits to
134:computer science
118:
115:
109:
107:
66:
38:
30:
21:
1565:
1564:
1560:
1559:
1558:
1556:
1555:
1554:
1540:
1539:
1538:
1537:
1528:
1526:
1517:
1516:
1512:
1507:
1460:
1455:
1454:
1451:
1448:
1445:
1442:
1439:
1436:
1433:
1430:
1427:
1424:
1421:
1418:
1415:
1412:
1409:
1406:
1403:
1400:
1397:
1394:
1391:
1388:
1385:
1382:
1379:
1376:
1373:
1370:
1367:
1364:
1362:// Using modulo
1361:
1358:
1355:
1352:
1349:
1346:
1343:
1340:
1337:
1334:
1331:
1328:
1325:
1322:
1319:
1316:
1313:
1310:
1307:
1304:
1301:
1298:
1295:
1292:
1289:
1286:
1283:
1280:
1277:
1274:
1271:
1268:
1265:
1262:
1259:
1256:
1253:
1250:
1247:
1244:
1241:
1238:
1235:
1232:
1229:
1226:
1223:
1220:
1217:
1214:
1211:
1208:
1205:
1202:
1199:
1196:
1193:
1190:
1187:
1174:
1110:value with all
1082:
1072:
1061:
1060:
1053:
1050:
1047:
1046:
1037:255.255.255.255
1036:
1033:
1030:
1029:
1021:(inverse mask)
1016:
1015:
1008:
1007:
1001:255.255.255.255
1000:
999:
990:
989:
982:
981:
975:255.255.255.255
974:
973:
963:
962:
955:
954:
947:
946:
939:
938:
919:
918:
909:
908:
883:
882:
876:255.255.255.224
875:
874:
867:
866:
861:
848:
844:
840:
836:
828:
827:
824:
821:
818:
815:
812:
809:
806:
803:
800:
797:
794:
791:
788:
785:
782:
779:
776:
773:
770:
767:
764:
761:
758:
755:
752:
749:
746:
743:
740:
737:
734:
731:
728:
725:
722:
719:
716:
713:
710:
707:
704:
701:
698:
695:
692:
689:
686:
683:
680:
677:
674:
671:
668:
665:
662:
659:
652:
648:
645:
644:
641:
638:
635:
632:
629:
626:
620:
619:
616:
613:
610:
607:
604:
601:
597:is declared as
594:
590:
586:
582:
578:
575:
574:
571:
568:
565:
562:
559:
556:
553:
550:
547:
544:
541:
535:stencil buffers
530:
519:
506:
501:
495:
481:
480:, just like an
477:
473:
469:
465:
461:
457:
453:
449:
445:
441:
437:
433:
429:
418:
414:
408:
403:
398:
364:
360:
356:
352:
349:
344:
304:
300:
296:
292:
288:
284:
279:) than "masked
276:
269:
265:
261:
220:
219:is used with a
216:
212:
208:
204:
200:
191:
186:
182:
178:
130:
119:
113:
110:
67:
65:
51:
39:
28:
23:
22:
15:
12:
11:
5:
1563:
1553:
1552:
1536:
1535:
1509:
1508:
1506:
1503:
1502:
1501:
1496:
1494:Tagged pointer
1491:
1486:
1481:
1476:
1471:
1466:
1459:
1456:
1186:
1173:
1170:
1166:alpha channels
1089:Raster graphic
1071:
1068:
903:Mask example:
860:
857:
658:
625:
600:
540:
518:
515:
505:
502:
499:
489:
422:if and only if
411:(exclusive or)
402:
399:
372:
348:
345:
319:
268:
262:
236:
185:
179:
177:
174:
121:
120:
56:. Please help
42:
40:
33:
26:
9:
6:
4:
3:
2:
1562:
1551:
1548:
1547:
1545:
1524:
1523:PyImageSearch
1520:
1514:
1510:
1500:
1497:
1495:
1492:
1490:
1487:
1485:
1482:
1480:
1477:
1475:
1472:
1470:
1467:
1465:
1464:Affinity mask
1462:
1461:
1332:hash_function
1184:
1181:
1179:
1169:
1167:
1163:
1158:
1156:
1153:
1149:
1141:
1137:
1135:
1130:
1128:
1124:
1119:
1117:
1113:
1109:
1105:
1101:
1093:
1090:
1086:
1081:
1080:Clipping path
1077:
1067:
1065:
1057:
1042:
1041:means "any".
1040:
1025:
1022:
1020:
1012:
1009:255.255.255.0
1004:
996:
994:
991:255.255.255.0
986:
978:
969:
967:
959:
951:
943:
935:
930:
927:
924:
923:
914:
913:
904:
901:
899:
895:
891:
890:wildcard mask
887:
879:
871:
868:203.0.113.129
859:Inverse masks
856:
854:
834:
656:
623:
598:
538:
536:
528:
524:
510:
498:
493:
488:
485:
460:, it returns
427:
423:
412:
396:
392:
388:
384:
380:
376:
371:
368:
342:
338:
334:
330:
326:
322:
318:
316:
312:
307:
282:
274:
259:
255:
251:
247:
243:
239:
235:
233:
229:
224:
198:
197:the principle
194:
173:
171:
167:
163:
159:
155:
151:
147:
143:
139:
135:
128:
117:
106:
103:
99:
96:
92:
89:
85:
82:
78:
75: –
74:
70:
69:Find sources:
63:
59:
55:
49:
48:
47:single source
43:This article
41:
37:
32:
31:
19:
1527:. Retrieved
1525:. 2018-11-19
1522:
1513:
1407:HASH_BITMASK
1401:hashed_token
1374:hashed_token
1326:hashed_token
1272:HASH_BITMASK
1182:
1175:
1159:
1145:
1131:
1120:
1115:
1097:
1062:198.51.100.2
1059:
1048:198.51.100.2
1045:
1043:
1028:
1026:
1023:
1014:
1006:
998:
997:
988:
983:198.51.100.0
980:
972:
970:
961:
953:
945:
937:
931:
928:
925:
917:
915:
907:
905:
902:
897:
893:
881:
873:
865:
862:
841:unsigned int
829:
646:
621:
576:
520:
496:
491:
486:
428:of bits are
404:
394:
390:
389:000 = 0000
386:
382:
381:101 AND 0000
378:
374:
369:
350:
340:
336:
332:
328:
324:
320:
310:
308:
280:
272:
270:
257:
253:
249:
245:
241:
237:
227:
225:
187:
141:
137:
131:
111:
101:
94:
87:
80:
68:
44:
1419:token_array
1380:MAX_RECORDS
1356:NUM_BUCKETS
1293:token_array
1284:// (2^10)-1
1245:MAX_RECORDS
1236:// 2^32 - 1
1224:NUM_BUCKETS
1172:Hash tables
1127:bitwise AND
1070:Image masks
956:192.0.2.255
845:glClear(42)
478:Y XOR 0 = Y
470:0 XOR 1 = 1
468:it returns
462:1 XOR 1 = 0
413:operation.
313:the higher
305:Y AND 1 = Y
293:Y AND 0 = 0
230:the higher
166:predication
1529:2020-04-05
1505:References
1230:0xFFFFFFFF
1178:hash table
1134:bitwise OR
1074:See also:
837:GLbitfield
669:GLbitfield
611:GLbitfield
426:odd number
393:000 0000
385:000 0000
377:101 1001
205:Y OR 0 = Y
201:Y OR 1 = 1
114:April 2020
84:newspapers
1474:Bit field
1017:0.0.0.255
964:192.0.2.x
948:192.0.2.1
920:0.0.0.255
910:192.0.2.0
884:0.0.0.255
833:type-safe
653:glClear()
595:glClear()
531:glClear()
335:1111 =
327:0101 AND
252:0000 =
244:0101 OR
150:bit field
54:talk page
1544:Category
1458:See also
1323:uint32_t
1269:uint32_t
1254:<<
1242:uint32_t
1221:uint32_t
1194:#include
1188:#include
1123:run time
1076:Bit blit
952:through
940:192.0.2.
847:or even
417:returns
299:ed with
190:bitwise
1263:// 2^10
1150:), for
1148:sprites
1104:bitmaps
1092:sprites
1054:0.0.0.0
1031:0.0.0.0
872:with a
663:glClear
627:glClear
605:glClear
542:glClear
339:0101
331:1111
323:0101
256:0101
248:0000
240:0101
142:bitmask
98:scholar
18:Bitmask
1489:Subnet
1443:return
1392:size_t
1365:size_t
1344:strlen
934:octets
916:mask:
589:, and
527:OpenGL
315:nibble
232:nibble
158:nibble
100:
93:
86:
79:
71:
1499:umask
1434:token
1425:index
1404:&
1395:index
1386:// OR
1368:index
1350:token
1338:token
1311:token
1278:0x3FF
1266:const
1239:const
1218:const
1155:icons
1108:pixel
851:. In
798:&
762:&
726:&
690:&
343:0101
260:0101
199:that
105:JSTOR
91:books
1308:char
1299:NULL
1287:char
1209:void
1203:main
1164:and
1116:mask
1112:bits
1078:and
835:. A
795:bits
759:bits
723:bits
687:bits
672:bits
660:void
614:bits
602:void
593:and
397:000
373:1001
341:0000
337:0000
333:0000
329:0000
325:1010
321:1001
258:1111
254:1111
250:1111
246:1111
242:1010
238:1001
203:and
162:word
154:byte
138:mask
136:, a
77:news
1200:int
1152:GUI
1121:At
1098:In
853:C++
649:and
474:XOR
450:XOR
424:an
415:XOR
409:XOR
353:AND
311:off
303:as
297:AND
289:AND
273:off
168:in
140:or
132:In
60:by
1546::
1521:.
1359:);
1353:),
1290:**
1257:10
1066:"
1005:-
995:.
807:!=
792:((
789:if
771:!=
756:((
753:if
735:!=
720:((
717:if
699:!=
684:((
681:if
642:);
617:);
585:,
581:,
569:);
484:.
482:OR
367:.
281:on
228:on
223:.
217:OR
209:OR
192:OR
160:,
156:,
1532:.
1452:}
1449:;
1446:0
1437:;
1431:=
1428:)
1422:+
1416:(
1413:*
1410:;
1398:=
1383:;
1377:%
1371:=
1347:(
1341:,
1335:(
1329:=
1320:;
1314:=
1302:;
1296:=
1281:;
1275:=
1260:;
1251:1
1248:=
1233:;
1227:=
1215:{
1212:)
1206:(
1051:/
1034:/
960:(
898:1
894:0
825:}
822:}
816:{
813:)
810:0
804:)
786:}
780:{
777:)
774:0
768:)
750:}
744:{
741:)
738:0
732:)
714:}
708:{
705:)
702:0
696:)
678:{
675:)
666:(
636:|
630:(
608:(
566:0
563:,
560:0
557:,
554:1
551:,
548:1
545:(
523:C
466:0
458:1
454:1
446:1
442:1
438:0
434:1
430:1
419:1
395:0
391:1
387:1
383:1
379:0
375:1
365:0
361:0
357:0
301:1
285:1
277:0
266:0
221:0
213:1
183:1
129:.
116:)
112:(
102:·
95:·
88:·
81:·
64:.
50:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
