rusty_source_map/
base64_vlq.rs

1use crate::base64;
2
3// A single base 64 digit can contain 6 bits of data. For the base 64 variable
4// length quantities we use in the source map spec, the first bit is the sign,
5// the next four bits are the actual value, and the 6th bit is the
6// continuation bit. The continuation bit tells us whether there are more
7// digits in this value following this digit.
8//
9//   Continuation
10//   |    Sign
11//   |    |
12//   V    V
13//   101011
14
15const VLQ_BASE_SHIFT: usize = 5;
16
17// binary: 100000
18const VLQ_BASE: usize = 1 << VLQ_BASE_SHIFT;
19
20// binary: 011111
21const VLQ_BASE_MASK: usize = VLQ_BASE - 1;
22
23// binary: 100000
24const VLQ_CONTINUATION_BIT: usize = VLQ_BASE;
25
26fn to_vlq_signed(value: i32) -> i32 {
27    if value < 0 {
28        (-value << 1) + 1
29    } else {
30        value << 1
31    }
32}
33
34pub fn base64vlq_encode(value: i32) -> String {
35    let mut encoded = String::new();
36    let mut digit: i32;
37
38    let mut vlq = to_vlq_signed(value);
39
40    loop {
41        digit = ((vlq as usize) & VLQ_BASE_MASK) as i32;
42        vlq = ((vlq as usize) >> VLQ_BASE_SHIFT) as i32;
43
44        if vlq > 0 {
45            // There are still more digits in this value, so we must make sure the
46            // continuation bit is marked.
47            digit = ((digit as usize) | VLQ_CONTINUATION_BIT) as i32;
48        }
49        encoded.push(base64::encode(digit).unwrap());
50        if vlq <= 0 {
51            break;
52        }
53    }
54    encoded
55}
56
57#[test]
58fn test_to_vlq_signed() {
59    assert_eq!(to_vlq_signed(1), 0b10);
60    assert_eq!(to_vlq_signed(-1), 0b11);
61    assert_eq!(to_vlq_signed(2), 0b100);
62    assert_eq!(to_vlq_signed(-2), 0b101)
63}
64
65#[test]
66fn test_base64vlq_encode() {
67    let vlqs = [
68        (-255, "/P"),
69        (-254, "9P"),
70        (-253, "7P"),
71        (-252, "5P"),
72        (-251, "3P"),
73        (-250, "1P"),
74        (-249, "zP"),
75        (-248, "xP"),
76        (-247, "vP"),
77        (-246, "tP"),
78        (-245, "rP"),
79        (-244, "pP"),
80        (-243, "nP"),
81        (-242, "lP"),
82        (-241, "jP"),
83        (-240, "hP"),
84        (-239, "/O"),
85        (-238, "9O"),
86        (-237, "7O"),
87        (-236, "5O"),
88        (-235, "3O"),
89        (-234, "1O"),
90        (-233, "zO"),
91        (-232, "xO"),
92        (-231, "vO"),
93        (-230, "tO"),
94        (-229, "rO"),
95        (-228, "pO"),
96        (-227, "nO"),
97        (-226, "lO"),
98        (-225, "jO"),
99        (-224, "hO"),
100        (-223, "/N"),
101        (-222, "9N"),
102        (-221, "7N"),
103        (-220, "5N"),
104        (-219, "3N"),
105        (-218, "1N"),
106        (-217, "zN"),
107        (-216, "xN"),
108        (-215, "vN"),
109        (-214, "tN"),
110        (-213, "rN"),
111        (-212, "pN"),
112        (-211, "nN"),
113        (-210, "lN"),
114        (-209, "jN"),
115        (-208, "hN"),
116        (-207, "/M"),
117        (-206, "9M"),
118        (-205, "7M"),
119        (-204, "5M"),
120        (-203, "3M"),
121        (-202, "1M"),
122        (-201, "zM"),
123        (-200, "xM"),
124        (-199, "vM"),
125        (-198, "tM"),
126        (-197, "rM"),
127        (-196, "pM"),
128        (-195, "nM"),
129        (-194, "lM"),
130        (-193, "jM"),
131        (-192, "hM"),
132        (-191, "/L"),
133        (-190, "9L"),
134        (-189, "7L"),
135        (-188, "5L"),
136        (-187, "3L"),
137        (-186, "1L"),
138        (-185, "zL"),
139        (-184, "xL"),
140        (-183, "vL"),
141        (-182, "tL"),
142        (-181, "rL"),
143        (-180, "pL"),
144        (-179, "nL"),
145        (-178, "lL"),
146        (-177, "jL"),
147        (-176, "hL"),
148        (-175, "/K"),
149        (-174, "9K"),
150        (-173, "7K"),
151        (-172, "5K"),
152        (-171, "3K"),
153        (-170, "1K"),
154        (-169, "zK"),
155        (-168, "xK"),
156        (-167, "vK"),
157        (-166, "tK"),
158        (-165, "rK"),
159        (-164, "pK"),
160        (-163, "nK"),
161        (-162, "lK"),
162        (-161, "jK"),
163        (-160, "hK"),
164        (-159, "/J"),
165        (-158, "9J"),
166        (-157, "7J"),
167        (-156, "5J"),
168        (-155, "3J"),
169        (-154, "1J"),
170        (-153, "zJ"),
171        (-152, "xJ"),
172        (-151, "vJ"),
173        (-150, "tJ"),
174        (-149, "rJ"),
175        (-148, "pJ"),
176        (-147, "nJ"),
177        (-146, "lJ"),
178        (-145, "jJ"),
179        (-144, "hJ"),
180        (-143, "/I"),
181        (-142, "9I"),
182        (-141, "7I"),
183        (-140, "5I"),
184        (-139, "3I"),
185        (-138, "1I"),
186        (-137, "zI"),
187        (-136, "xI"),
188        (-135, "vI"),
189        (-134, "tI"),
190        (-133, "rI"),
191        (-132, "pI"),
192        (-131, "nI"),
193        (-130, "lI"),
194        (-129, "jI"),
195        (-128, "hI"),
196        (-127, "/H"),
197        (-126, "9H"),
198        (-125, "7H"),
199        (-124, "5H"),
200        (-123, "3H"),
201        (-122, "1H"),
202        (-121, "zH"),
203        (-120, "xH"),
204        (-119, "vH"),
205        (-118, "tH"),
206        (-117, "rH"),
207        (-116, "pH"),
208        (-115, "nH"),
209        (-114, "lH"),
210        (-113, "jH"),
211        (-112, "hH"),
212        (-111, "/G"),
213        (-110, "9G"),
214        (-109, "7G"),
215        (-108, "5G"),
216        (-107, "3G"),
217        (-106, "1G"),
218        (-105, "zG"),
219        (-104, "xG"),
220        (-103, "vG"),
221        (-102, "tG"),
222        (-101, "rG"),
223        (-100, "pG"),
224        (-99, "nG"),
225        (-98, "lG"),
226        (-97, "jG"),
227        (-96, "hG"),
228        (-95, "/F"),
229        (-94, "9F"),
230        (-93, "7F"),
231        (-92, "5F"),
232        (-91, "3F"),
233        (-90, "1F"),
234        (-89, "zF"),
235        (-88, "xF"),
236        (-87, "vF"),
237        (-86, "tF"),
238        (-85, "rF"),
239        (-84, "pF"),
240        (-83, "nF"),
241        (-82, "lF"),
242        (-81, "jF"),
243        (-80, "hF"),
244        (-79, "/E"),
245        (-78, "9E"),
246        (-77, "7E"),
247        (-76, "5E"),
248        (-75, "3E"),
249        (-74, "1E"),
250        (-73, "zE"),
251        (-72, "xE"),
252        (-71, "vE"),
253        (-70, "tE"),
254        (-69, "rE"),
255        (-68, "pE"),
256        (-67, "nE"),
257        (-66, "lE"),
258        (-65, "jE"),
259        (-64, "hE"),
260        (-63, "/D"),
261        (-62, "9D"),
262        (-61, "7D"),
263        (-60, "5D"),
264        (-59, "3D"),
265        (-58, "1D"),
266        (-57, "zD"),
267        (-56, "xD"),
268        (-55, "vD"),
269        (-54, "tD"),
270        (-53, "rD"),
271        (-52, "pD"),
272        (-51, "nD"),
273        (-50, "lD"),
274        (-49, "jD"),
275        (-48, "hD"),
276        (-47, "/C"),
277        (-46, "9C"),
278        (-45, "7C"),
279        (-44, "5C"),
280        (-43, "3C"),
281        (-42, "1C"),
282        (-41, "zC"),
283        (-40, "xC"),
284        (-39, "vC"),
285        (-38, "tC"),
286        (-37, "rC"),
287        (-36, "pC"),
288        (-35, "nC"),
289        (-34, "lC"),
290        (-33, "jC"),
291        (-32, "hC"),
292        (-31, "/B"),
293        (-30, "9B"),
294        (-29, "7B"),
295        (-28, "5B"),
296        (-27, "3B"),
297        (-26, "1B"),
298        (-99, "nG"),
299        (-98, "lG"),
300        (-97, "jG"),
301        (-96, "hG"),
302        (-95, "/F"),
303        (-94, "9F"),
304        (-93, "7F"),
305        (-92, "5F"),
306        (-91, "3F"),
307        (-90, "1F"),
308        (-89, "zF"),
309        (-88, "xF"),
310        (-87, "vF"),
311        (-86, "tF"),
312        (-85, "rF"),
313        (-84, "pF"),
314        (-83, "nF"),
315        (-82, "lF"),
316        (-81, "jF"),
317        (-80, "hF"),
318        (-79, "/E"),
319        (-78, "9E"),
320        (-77, "7E"),
321        (-76, "5E"),
322        (-75, "3E"),
323        (-74, "1E"),
324        (-73, "zE"),
325        (-72, "xE"),
326        (-71, "vE"),
327        (-70, "tE"),
328        (-69, "rE"),
329        (-68, "pE"),
330        (-67, "nE"),
331        (-66, "lE"),
332        (-65, "jE"),
333        (-64, "hE"),
334        (-63, "/D"),
335        (-62, "9D"),
336        (-61, "7D"),
337        (-60, "5D"),
338        (-59, "3D"),
339        (-58, "1D"),
340        (-57, "zD"),
341        (-56, "xD"),
342        (-55, "vD"),
343        (-54, "tD"),
344        (-53, "rD"),
345        (-52, "pD"),
346        (-51, "nD"),
347        (-50, "lD"),
348        (-49, "jD"),
349        (-48, "hD"),
350        (-47, "/C"),
351        (-46, "9C"),
352        (-45, "7C"),
353        (-44, "5C"),
354        (-43, "3C"),
355        (-42, "1C"),
356        (-41, "zC"),
357        (-40, "xC"),
358        (-39, "vC"),
359        (-38, "tC"),
360        (-37, "rC"),
361        (-36, "pC"),
362        (-35, "nC"),
363        (-34, "lC"),
364        (-33, "jC"),
365        (-32, "hC"),
366        (-31, "/B"),
367        (-30, "9B"),
368        (-29, "7B"),
369        (-28, "5B"),
370        (-27, "3B"),
371        (-26, "1B"),
372        (-25, "zB"),
373        (-24, "xB"),
374        (-23, "vB"),
375        (-22, "tB"),
376        (-21, "rB"),
377        (-20, "pB"),
378        (-19, "nB"),
379        (-18, "lB"),
380        (-17, "jB"),
381        (-16, "hB"),
382        (-25, "zB"),
383        (-24, "xB"),
384        (-23, "vB"),
385        (-22, "tB"),
386        (-21, "rB"),
387        (-20, "pB"),
388        (-19, "nB"),
389        (-18, "lB"),
390        (-17, "jB"),
391        (-16, "hB"),
392        (-15, "f"),
393        (-14, "d"),
394        (-13, "b"),
395        (-12, "Z"),
396        (-11, "X"),
397        (-10, "V"),
398        (-9, "T"),
399        (-8, "R"),
400        (-7, "P"),
401        (-6, "N"),
402        (-5, "L"),
403        (-4, "J"),
404        (-3, "H"),
405        (-2, "F"),
406        (-1, "D"),
407        (0, "A"),
408        (1, "C"),
409        (2, "E"),
410        (3, "G"),
411        (4, "I"),
412        (5, "K"),
413        (6, "M"),
414        (7, "O"),
415        (8, "Q"),
416        (9, "S"),
417        (10, "U"),
418        (11, "W"),
419        (12, "Y"),
420        (13, "a"),
421        (14, "c"),
422        (15, "e"),
423        (16, "gB"),
424        (17, "iB"),
425        (18, "kB"),
426        (19, "mB"),
427        (20, "oB"),
428        (21, "qB"),
429        (22, "sB"),
430        (23, "uB"),
431        (24, "wB"),
432        (25, "yB"),
433        (26, "0B"),
434        (27, "2B"),
435        (28, "4B"),
436        (29, "6B"),
437        (30, "8B"),
438        (31, "+B"),
439        (32, "gC"),
440        (33, "iC"),
441        (34, "kC"),
442        (35, "mC"),
443        (36, "oC"),
444        (37, "qC"),
445        (38, "sC"),
446        (39, "uC"),
447        (40, "wC"),
448        (41, "yC"),
449        (42, "0C"),
450        (43, "2C"),
451        (44, "4C"),
452        (45, "6C"),
453        (46, "8C"),
454        (47, "+C"),
455        (48, "gD"),
456        (49, "iD"),
457        (50, "kD"),
458        (51, "mD"),
459        (52, "oD"),
460        (53, "qD"),
461        (54, "sD"),
462        (55, "uD"),
463        (56, "wD"),
464        (57, "yD"),
465        (58, "0D"),
466        (59, "2D"),
467        (60, "4D"),
468        (61, "6D"),
469        (62, "8D"),
470        (63, "+D"),
471        (64, "gE"),
472        (65, "iE"),
473        (66, "kE"),
474        (67, "mE"),
475        (68, "oE"),
476        (69, "qE"),
477        (70, "sE"),
478        (71, "uE"),
479        (72, "wE"),
480        (73, "yE"),
481        (74, "0E"),
482        (75, "2E"),
483        (76, "4E"),
484        (77, "6E"),
485        (78, "8E"),
486        (79, "+E"),
487        (80, "gF"),
488        (81, "iF"),
489        (82, "kF"),
490        (83, "mF"),
491        (84, "oF"),
492        (85, "qF"),
493        (86, "sF"),
494        (87, "uF"),
495        (88, "wF"),
496        (89, "yF"),
497        (90, "0F"),
498        (91, "2F"),
499        (92, "4F"),
500        (93, "6F"),
501        (94, "8F"),
502        (95, "+F"),
503        (96, "gG"),
504        (97, "iG"),
505        (98, "kG"),
506        (99, "mG"),
507        (100, "oG"),
508        (101, "qG"),
509        (102, "sG"),
510        (103, "uG"),
511        (104, "wG"),
512        (105, "yG"),
513        (106, "0G"),
514        (107, "2G"),
515        (108, "4G"),
516        (109, "6G"),
517        (110, "8G"),
518        (111, "+G"),
519        (112, "gH"),
520        (113, "iH"),
521        (114, "kH"),
522        (115, "mH"),
523        (116, "oH"),
524        (117, "qH"),
525        (118, "sH"),
526        (119, "uH"),
527        (120, "wH"),
528        (121, "yH"),
529        (122, "0H"),
530        (123, "2H"),
531        (124, "4H"),
532        (125, "6H"),
533        (126, "8H"),
534        (127, "+H"),
535        (128, "gI"),
536        (129, "iI"),
537        (130, "kI"),
538        (131, "mI"),
539        (132, "oI"),
540        (133, "qI"),
541        (134, "sI"),
542        (135, "uI"),
543        (136, "wI"),
544        (137, "yI"),
545        (138, "0I"),
546        (139, "2I"),
547        (140, "4I"),
548        (141, "6I"),
549        (142, "8I"),
550        (143, "+I"),
551        (144, "gJ"),
552        (145, "iJ"),
553        (146, "kJ"),
554        (147, "mJ"),
555        (148, "oJ"),
556        (149, "qJ"),
557        (150, "sJ"),
558        (151, "uJ"),
559        (152, "wJ"),
560        (157, "6J"),
561        (158, "8J"),
562        (159, "+J"),
563        (160, "gK"),
564        (161, "iK"),
565        (162, "kK"),
566        (163, "mK"),
567        (164, "oK"),
568        (165, "qK"),
569        (166, "sK"),
570        (167, "uK"),
571        (168, "wK"),
572        (169, "yK"),
573        (170, "0K"),
574        (171, "2K"),
575        (172, "4K"),
576        (173, "6K"),
577        (174, "8K"),
578        (175, "+K"),
579        (176, "gL"),
580        (177, "iL"),
581        (178, "kL"),
582        (179, "mL"),
583        (180, "oL"),
584        (181, "qL"),
585        (182, "sL"),
586        (183, "uL"),
587        (184, "wL"),
588        (185, "yL"),
589        (186, "0L"),
590        (187, "2L"),
591        (188, "4L"),
592        (189, "6L"),
593        (190, "8L"),
594        (191, "+L"),
595        (192, "gM"),
596        (193, "iM"),
597        (194, "kM"),
598        (195, "mM"),
599        (196, "oM"),
600        (197, "qM"),
601        (198, "sM"),
602        (199, "uM"),
603        (200, "wM"),
604        (201, "yM"),
605        (202, "0M"),
606        (203, "2M"),
607        (204, "4M"),
608        (205, "6M"),
609        (206, "8M"),
610        (207, "+M"),
611        (208, "gN"),
612        (209, "iN"),
613        (210, "kN"),
614        (211, "mN"),
615        (212, "oN"),
616        (213, "qN"),
617        (214, "sN"),
618        (215, "uN"),
619        (216, "wN"),
620        (217, "yN"),
621        (218, "0N"),
622        (219, "2N"),
623        (220, "4N"),
624        (221, "6N"),
625        (222, "8N"),
626        (223, "+N"),
627        (224, "gO"),
628        (225, "iO"),
629        (226, "kO"),
630        (227, "mO"),
631        (228, "oO"),
632        (229, "qO"),
633        (230, "sO"),
634        (231, "uO"),
635        (232, "wO"),
636        (233, "yO"),
637        (234, "0O"),
638        (235, "2O"),
639        (236, "4O"),
640        (237, "6O"),
641        (238, "8O"),
642        (239, "+O"),
643        (240, "gP"),
644        (241, "iP"),
645        (242, "kP"),
646        (243, "mP"),
647        (244, "oP"),
648        (245, "qP"),
649        (246, "sP"),
650        (247, "uP"),
651        (248, "wP"),
652        (249, "yP"),
653        (250, "0P"),
654        (251, "2P"),
655        (252, "4P"),
656        (253, "6P"),
657        (254, "8P"),
658        (255, "+P"),
659    ];
660
661    for vlq in vlqs {
662        assert_eq!(base64vlq_encode(vlq.0), vlq.1.to_string());
663    }
664}
rusty_source_map/base64_vlq.rs

rusty_source_map/
base64_vlq.rs
