1	# RFC 7541 Appendix B Huffman alphabet and streaming codec.
2	import Base
3	import bend-kit-bytes@0.3.2.0/bytes.bend as Bytes
4	
5	type Code is Data:
6	  Code{bits: U32, width: U32}
7	
8	def code(+octet: U32) -> Code:
9	  match octet:
10	    case 0:
11	      Code{8184, 13}
12	    case 1:
13	      Code{8388568, 23}
14	    case 2:
15	      Code{268435426, 28}
16	    case 3:
17	      Code{268435427, 28}
18	    case 4:
19	      Code{268435428, 28}
20	    case 5:
21	      Code{268435429, 28}
22	    case 6:
23	      Code{268435430, 28}
24	    case 7:
25	      Code{268435431, 28}
26	    case 8:
27	      Code{268435432, 28}
28	    case 9:
29	      Code{16777194, 24}
30	    case 10:
31	      Code{1073741820, 30}
32	    case 11:
33	      Code{268435433, 28}
34	    case 12:
35	      Code{268435434, 28}
36	    case 13:
37	      Code{1073741821, 30}
38	    case 14:
39	      Code{268435435, 28}
40	    case 15:
41	      Code{268435436, 28}
42	    case 16:
43	      Code{268435437, 28}
44	    case 17:
45	      Code{268435438, 28}
46	    case 18:
47	      Code{268435439, 28}
48	    case 19:
49	      Code{268435440, 28}
50	    case 20:
51	      Code{268435441, 28}
52	    case 21:
53	      Code{268435442, 28}
54	    case 22:
55	      Code{1073741822, 30}
56	    case 23:
57	      Code{268435443, 28}
58	    case 24:
59	      Code{268435444, 28}
60	    case 25:
61	      Code{268435445, 28}
62	    case 26:
63	      Code{268435446, 28}
64	    case 27:
65	      Code{268435447, 28}
66	    case 28:
67	      Code{268435448, 28}
68	    case 29:
69	      Code{268435449, 28}
70	    case 30:
71	      Code{268435450, 28}
72	    case 31:
73	      Code{268435451, 28}
74	    case 32:
75	      Code{20, 6}
76	    case 33:
77	      Code{1016, 10}
78	    case 34:
79	      Code{1017, 10}
80	    case 35:
81	      Code{4090, 12}
82	    case 36:
83	      Code{8185, 13}
84	    case 37:
85	      Code{21, 6}
86	    case 38:
87	      Code{248, 8}
88	    case 39:
89	      Code{2042, 11}
90	    case 40:
91	      Code{1018, 10}
92	    case 41:
93	      Code{1019, 10}
94	    case 42:
95	      Code{249, 8}
96	    case 43:
97	      Code{2043, 11}
98	    case 44:
99	      Code{250, 8}
100	    case 45:
101	      Code{22, 6}
102	    case 46:
103	      Code{23, 6}
104	    case 47:
105	      Code{24, 6}
106	    case 48:
107	      Code{0, 5}
108	    case 49:
109	      Code{1, 5}
110	    case 50:
111	      Code{2, 5}
112	    case 51:
113	      Code{25, 6}
114	    case 52:
115	      Code{26, 6}
116	    case 53:
117	      Code{27, 6}
118	    case 54:
119	      Code{28, 6}
120	    case 55:
121	      Code{29, 6}
122	    case 56:
123	      Code{30, 6}
124	    case 57:
125	      Code{31, 6}
126	    case 58:
127	      Code{92, 7}
128	    case 59:
129	      Code{251, 8}
130	    case 60:
131	      Code{32764, 15}
132	    case 61:
133	      Code{32, 6}
134	    case 62:
135	      Code{4091, 12}
136	    case 63:
137	      Code{1020, 10}
138	    case 64:
139	      Code{8186, 13}
140	    case 65:
141	      Code{33, 6}
142	    case 66:
143	      Code{93, 7}
144	    case 67:
145	      Code{94, 7}
146	    case 68:
147	      Code{95, 7}
148	    case 69:
149	      Code{96, 7}
150	    case 70:
151	      Code{97, 7}
152	    case 71:
153	      Code{98, 7}
154	    case 72:
155	      Code{99, 7}
156	    case 73:
157	      Code{100, 7}
158	    case 74:
159	      Code{101, 7}
160	    case 75:
161	      Code{102, 7}
162	    case 76:
163	      Code{103, 7}
164	    case 77:
165	      Code{104, 7}
166	    case 78:
167	      Code{105, 7}
168	    case 79:
169	      Code{106, 7}
170	    case 80:
171	      Code{107, 7}
172	    case 81:
173	      Code{108, 7}
174	    case 82:
175	      Code{109, 7}
176	    case 83:
177	      Code{110, 7}
178	    case 84:
179	      Code{111, 7}
180	    case 85:
181	      Code{112, 7}
182	    case 86:
183	      Code{113, 7}
184	    case 87:
185	      Code{114, 7}
186	    case 88:
187	      Code{252, 8}
188	    case 89:
189	      Code{115, 7}
190	    case 90:
191	      Code{253, 8}
192	    case 91:
193	      Code{8187, 13}
194	    case 92:
195	      Code{524272, 19}
196	    case 93:
197	      Code{8188, 13}
198	    case 94:
199	      Code{16380, 14}
200	    case 95:
201	      Code{34, 6}
202	    case 96:
203	      Code{32765, 15}
204	    case 97:
205	      Code{3, 5}
206	    case 98:
207	      Code{35, 6}
208	    case 99:
209	      Code{4, 5}
210	    case 100:
211	      Code{36, 6}
212	    case 101:
213	      Code{5, 5}
214	    case 102:
215	      Code{37, 6}
216	    case 103:
217	      Code{38, 6}
218	    case 104:
219	      Code{39, 6}
220	    case 105:
221	      Code{6, 5}
222	    case 106:
223	      Code{116, 7}
224	    case 107:
225	      Code{117, 7}
226	    case 108:
227	      Code{40, 6}
228	    case 109:
229	      Code{41, 6}
230	    case 110:
231	      Code{42, 6}
232	    case 111:
233	      Code{7, 5}
234	    case 112:
235	      Code{43, 6}
236	    case 113:
237	      Code{118, 7}
238	    case 114:
239	      Code{44, 6}
240	    case 115:
241	      Code{8, 5}
242	    case 116:
243	      Code{9, 5}
244	    case 117:
245	      Code{45, 6}
246	    case 118:
247	      Code{119, 7}
248	    case 119:
249	      Code{120, 7}
250	    case 120:
251	      Code{121, 7}
252	    case 121:
253	      Code{122, 7}
254	    case 122:
255	      Code{123, 7}
256	    case 123:
257	      Code{32766, 15}
258	    case 124:
259	      Code{2044, 11}
260	    case 125:
261	      Code{16381, 14}
262	    case 126:
263	      Code{8189, 13}
264	    case 127:
265	      Code{268435452, 28}
266	    case 128:
267	      Code{1048550, 20}
268	    case 129:
269	      Code{4194258, 22}
270	    case 130:
271	      Code{1048551, 20}
272	    case 131:
273	      Code{1048552, 20}
274	    case 132:
275	      Code{4194259, 22}
276	    case 133:
277	      Code{4194260, 22}
278	    case 134:
279	      Code{4194261, 22}
280	    case 135:
281	      Code{8388569, 23}
282	    case 136:
283	      Code{4194262, 22}
284	    case 137:
285	      Code{8388570, 23}
286	    case 138:
287	      Code{8388571, 23}
288	    case 139:
289	      Code{8388572, 23}
290	    case 140:
291	      Code{8388573, 23}
292	    case 141:
293	      Code{8388574, 23}
294	    case 142:
295	      Code{16777195, 24}
296	    case 143:
297	      Code{8388575, 23}
298	    case 144:
299	      Code{16777196, 24}
300	    case 145:
301	      Code{16777197, 24}
302	    case 146:
303	      Code{4194263, 22}
304	    case 147:
305	      Code{8388576, 23}
306	    case 148:
307	      Code{16777198, 24}
308	    case 149:
309	      Code{8388577, 23}
310	    case 150:
311	      Code{8388578, 23}
312	    case 151:
313	      Code{8388579, 23}
314	    case 152:
315	      Code{8388580, 23}
316	    case 153:
317	      Code{2097116, 21}
318	    case 154:
319	      Code{4194264, 22}
320	    case 155:
321	      Code{8388581, 23}
322	    case 156:
323	      Code{4194265, 22}
324	    case 157:
325	      Code{8388582, 23}
326	    case 158:
327	      Code{8388583, 23}
328	    case 159:
329	      Code{16777199, 24}
330	    case 160:
331	      Code{4194266, 22}
332	    case 161:
333	      Code{2097117, 21}
334	    case 162:
335	      Code{1048553, 20}
336	    case 163:
337	      Code{4194267, 22}
338	    case 164:
339	      Code{4194268, 22}
340	    case 165:
341	      Code{8388584, 23}
342	    case 166:
343	      Code{8388585, 23}
344	    case 167:
345	      Code{2097118, 21}
346	    case 168:
347	      Code{8388586, 23}
348	    case 169:
349	      Code{4194269, 22}
350	    case 170:
351	      Code{4194270, 22}
352	    case 171:
353	      Code{16777200, 24}
354	    case 172:
355	      Code{2097119, 21}
356	    case 173:
357	      Code{4194271, 22}
358	    case 174:
359	      Code{8388587, 23}
360	    case 175:
361	      Code{8388588, 23}
362	    case 176:
363	      Code{2097120, 21}
364	    case 177:
365	      Code{2097121, 21}
366	    case 178:
367	      Code{4194272, 22}
368	    case 179:
369	      Code{2097122, 21}
370	    case 180:
371	      Code{8388589, 23}
372	    case 181:
373	      Code{4194273, 22}
374	    case 182:
375	      Code{8388590, 23}
376	    case 183:
377	      Code{8388591, 23}
378	    case 184:
379	      Code{1048554, 20}
380	    case 185:
381	      Code{4194274, 22}
382	    case 186:
383	      Code{4194275, 22}
384	    case 187:
385	      Code{4194276, 22}
386	    case 188:
387	      Code{8388592, 23}
388	    case 189:
389	      Code{4194277, 22}
390	    case 190:
391	      Code{4194278, 22}
392	    case 191:
393	      Code{8388593, 23}
394	    case 192:
395	      Code{67108832, 26}
396	    case 193:
397	      Code{67108833, 26}
398	    case 194:
399	      Code{1048555, 20}
400	    case 195:
401	      Code{524273, 19}
402	    case 196:
403	      Code{4194279, 22}
404	    case 197:
405	      Code{8388594, 23}
406	    case 198:
407	      Code{4194280, 22}
408	    case 199:
409	      Code{33554412, 25}
410	    case 200:
411	      Code{67108834, 26}
412	    case 201:
413	      Code{67108835, 26}
414	    case 202:
415	      Code{67108836, 26}
416	    case 203:
417	      Code{134217694, 27}
418	    case 204:
419	      Code{134217695, 27}
420	    case 205:
421	      Code{67108837, 26}
422	    case 206:
423	      Code{16777201, 24}
424	    case 207:
425	      Code{33554413, 25}
426	    case 208:
427	      Code{524274, 19}
428	    case 209:
429	      Code{2097123, 21}
430	    case 210:
431	      Code{67108838, 26}
432	    case 211:
433	      Code{134217696, 27}
434	    case 212:
435	      Code{134217697, 27}
436	    case 213:
437	      Code{67108839, 26}
438	    case 214:
439	      Code{134217698, 27}
440	    case 215:
441	      Code{16777202, 24}
442	    case 216:
443	      Code{2097124, 21}
444	    case 217:
445	      Code{2097125, 21}
446	    case 218:
447	      Code{67108840, 26}
448	    case 219:
449	      Code{67108841, 26}
450	    case 220:
451	      Code{268435453, 28}
452	    case 221:
453	      Code{134217699, 27}
454	    case 222:
455	      Code{134217700, 27}
456	    case 223:
457	      Code{134217701, 27}
458	    case 224:
459	      Code{1048556, 20}
460	    case 225:
461	      Code{16777203, 24}
462	    case 226:
463	      Code{1048557, 20}
464	    case 227:
465	      Code{2097126, 21}
466	    case 228:
467	      Code{4194281, 22}
468	    case 229:
469	      Code{2097127, 21}
470	    case 230:
471	      Code{2097128, 21}
472	    case 231:
473	      Code{8388595, 23}
474	    case 232:
475	      Code{4194282, 22}
476	    case 233:
477	      Code{4194283, 22}
478	    case 234:
479	      Code{33554414, 25}
480	    case 235:
481	      Code{33554415, 25}
482	    case 236:
483	      Code{16777204, 24}
484	    case 237:
485	      Code{16777205, 24}
486	    case 238:
487	      Code{67108842, 26}
488	    case 239:
489	      Code{8388596, 23}
490	    case 240:
491	      Code{67108843, 26}
492	    case 241:
493	      Code{134217702, 27}
494	    case 242:
495	      Code{67108844, 26}
496	    case 243:
497	      Code{67108845, 26}
498	    case 244:
499	      Code{134217703, 27}
500	    case 245:
501	      Code{134217704, 27}
502	    case 246:
503	      Code{134217705, 27}
504	    case 247:
505	      Code{134217706, 27}
506	    case 248:
507	      Code{134217707, 27}
508	    case 249:
509	      Code{268435454, 28}
510	    case 250:
511	      Code{134217708, 27}
512	    case 251:
513	      Code{134217709, 27}
514	    case 252:
515	      Code{134217710, 27}
516	    case 253:
517	      Code{134217711, 27}
518	    case 254:
519	      Code{134217712, 27}
520	    case 255:
521	      Code{67108846, 26}
522	    case 256:
523	      Code{1073741823, 30}
524	    case _:
525	      Code{0, 0}
526	
527	def width.of(c: Code) -> U32:
528	  match c:
529	    case Code{bits, width}:
530	      width
531	
532	def width(+octet: U32) -> U32:
533	  width.of(code(octet))
534	
535	def symbol(+width: U32, +bits: U32) -> Maybe<&2, U32>:
536	  match width:
537	    case 5:
538	      match bits:
539	        case 0:
540	          Some{48}
541	        case 1:
542	          Some{49}
543	        case 2:
544	          Some{50}
545	        case 3:
546	          Some{97}
547	        case 4:
548	          Some{99}
549	        case 5:
550	          Some{101}
551	        case 6:
552	          Some{105}
553	        case 7:
554	          Some{111}
555	        case 8:
556	          Some{115}
557	        case 9:
558	          Some{116}
559	        case _:
560	          None{}
561	    case 6:
562	      match bits:
563	        case 20:
564	          Some{32}
565	        case 21:
566	          Some{37}
567	        case 22:
568	          Some{45}
569	        case 23:
570	          Some{46}
571	        case 24:
572	          Some{47}
573	        case 25:
574	          Some{51}
575	        case 26:
576	          Some{52}
577	        case 27:
578	          Some{53}
579	        case 28:
580	          Some{54}
581	        case 29:
582	          Some{55}
583	        case 30:
584	          Some{56}
585	        case 31:
586	          Some{57}
587	        case 32:
588	          Some{61}
589	        case 33:
590	          Some{65}
591	        case 34:
592	          Some{95}
593	        case 35:
594	          Some{98}
595	        case 36:
596	          Some{100}
597	        case 37:
598	          Some{102}
599	        case 38:
600	          Some{103}
601	        case 39:
602	          Some{104}
603	        case 40:
604	          Some{108}
605	        case 41:
606	          Some{109}
607	        case 42:
608	          Some{110}
609	        case 43:
610	          Some{112}
611	        case 44:
612	          Some{114}
613	        case 45:
614	          Some{117}
615	        case _:
616	          None{}
617	    case 7:
618	      match bits:
619	        case 92:
620	          Some{58}
621	        case 93:
622	          Some{66}
623	        case 94:
624	          Some{67}
625	        case 95:
626	          Some{68}
627	        case 96:
628	          Some{69}
629	        case 97:
630	          Some{70}
631	        case 98:
632	          Some{71}
633	        case 99:
634	          Some{72}
635	        case 100:
636	          Some{73}
637	        case 101:
638	          Some{74}
639	        case 102:
640	          Some{75}
641	        case 103:
642	          Some{76}
643	        case 104:
644	          Some{77}
645	        case 105:
646	          Some{78}
647	        case 106:
648	          Some{79}
649	        case 107:
650	          Some{80}
651	        case 108:
652	          Some{81}
653	        case 109:
654	          Some{82}
655	        case 110:
656	          Some{83}
657	        case 111:
658	          Some{84}
659	        case 112:
660	          Some{85}
661	        case 113:
662	          Some{86}
663	        case 114:
664	          Some{87}
665	        case 115:
666	          Some{89}
667	        case 116:
668	          Some{106}
669	        case 117:
670	          Some{107}
671	        case 118:
672	          Some{113}
673	        case 119:
674	          Some{118}
675	        case 120:
676	          Some{119}
677	        case 121:
678	          Some{120}
679	        case 122:
680	          Some{121}
681	        case 123:
682	          Some{122}
683	        case _:
684	          None{}
685	    case 8:
686	      match bits:
687	        case 248:
688	          Some{38}
689	        case 249:
690	          Some{42}
691	        case 250:
692	          Some{44}
693	        case 251:
694	          Some{59}
695	        case 252:
696	          Some{88}
697	        case 253:
698	          Some{90}
699	        case _:
700	          None{}
701	    case 10:
702	      match bits:
703	        case 1016:
704	          Some{33}
705	        case 1017:
706	          Some{34}
707	        case 1018:
708	          Some{40}
709	        case 1019:
710	          Some{41}
711	        case 1020:
712	          Some{63}
713	        case _:
714	          None{}
715	    case 11:
716	      match bits:
717	        case 2042:
718	          Some{39}
719	        case 2043:
720	          Some{43}
721	        case 2044:
722	          Some{124}
723	        case _:
724	          None{}
725	    case 12:
726	      match bits:
727	        case 4090:
728	          Some{35}
729	        case 4091:
730	          Some{62}
731	        case _:
732	          None{}
733	    case 13:
734	      match bits:
735	        case 8184:
736	          Some{0}
737	        case 8185:
738	          Some{36}
739	        case 8186:
740	          Some{64}
741	        case 8187:
742	          Some{91}
743	        case 8188:
744	          Some{93}
745	        case 8189:
746	          Some{126}
747	        case _:
748	          None{}
749	    case 14:
750	      match bits:
751	        case 16380:
752	          Some{94}
753	        case 16381:
754	          Some{125}
755	        case _:
756	          None{}
757	    case 15:
758	      match bits:
759	        case 32764:
760	          Some{60}
761	        case 32765:
762	          Some{96}
763	        case 32766:
764	          Some{123}
765	        case _:
766	          None{}
767	    case 19:
768	      match bits:
769	        case 524272:
770	          Some{92}
771	        case 524273:
772	          Some{195}
773	        case 524274:
774	          Some{208}
775	        case _:
776	          None{}
777	    case 20:
778	      match bits:
779	        case 1048550:
780	          Some{128}
781	        case 1048551:
782	          Some{130}
783	        case 1048552:
784	          Some{131}
785	        case 1048553:
786	          Some{162}
787	        case 1048554:
788	          Some{184}
789	        case 1048555:
790	          Some{194}
791	        case 1048556:
792	          Some{224}
793	        case 1048557:
794	          Some{226}
795	        case _:
796	          None{}
797	    case 21:
798	      match bits:
799	        case 2097116:
800	          Some{153}
801	        case 2097117:
802	          Some{161}
803	        case 2097118:
804	          Some{167}
805	        case 2097119:
806	          Some{172}
807	        case 2097120:
808	          Some{176}
809	        case 2097121:
810	          Some{177}
811	        case 2097122:
812	          Some{179}
813	        case 2097123:
814	          Some{209}
815	        case 2097124:
816	          Some{216}
817	        case 2097125:
818	          Some{217}
819	        case 2097126:
820	          Some{227}
821	        case 2097127:
822	          Some{229}
823	        case 2097128:
824	          Some{230}
825	        case _:
826	          None{}
827	    case 22:
828	      match bits:
829	        case 4194258:
830	          Some{129}
831	        case 4194259:
832	          Some{132}
833	        case 4194260:
834	          Some{133}
835	        case 4194261:
836	          Some{134}
837	        case 4194262:
838	          Some{136}
839	        case 4194263:
840	          Some{146}
841	        case 4194264:
842	          Some{154}
843	        case 4194265:
844	          Some{156}
845	        case 4194266:
846	          Some{160}
847	        case 4194267:
848	          Some{163}
849	        case 4194268:
850	          Some{164}
851	        case 4194269:
852	          Some{169}
853	        case 4194270:
854	          Some{170}
855	        case 4194271:
856	          Some{173}
857	        case 4194272:
858	          Some{178}
859	        case 4194273:
860	          Some{181}
861	        case 4194274:
862	          Some{185}
863	        case 4194275:
864	          Some{186}
865	        case 4194276:
866	          Some{187}
867	        case 4194277:
868	          Some{189}
869	        case 4194278:
870	          Some{190}
871	        case 4194279:
872	          Some{196}
873	        case 4194280:
874	          Some{198}
875	        case 4194281:
876	          Some{228}
877	        case 4194282:
878	          Some{232}
879	        case 4194283:
880	          Some{233}
881	        case _:
882	          None{}
883	    case 23:
884	      match bits:
885	        case 8388568:
886	          Some{1}
887	        case 8388569:
888	          Some{135}
889	        case 8388570:
890	          Some{137}
891	        case 8388571:
892	          Some{138}
893	        case 8388572:
894	          Some{139}
895	        case 8388573:
896	          Some{140}
897	        case 8388574:
898	          Some{141}
899	        case 8388575:
900	          Some{143}
901	        case 8388576:
902	          Some{147}
903	        case 8388577:
904	          Some{149}
905	        case 8388578:
906	          Some{150}
907	        case 8388579:
908	          Some{151}
909	        case 8388580:
910	          Some{152}
911	        case 8388581:
912	          Some{155}
913	        case 8388582:
914	          Some{157}
915	        case 8388583:
916	          Some{158}
917	        case 8388584:
918	          Some{165}
919	        case 8388585:
920	          Some{166}
921	        case 8388586:
922	          Some{168}
923	        case 8388587:
924	          Some{174}
925	        case 8388588:
926	          Some{175}
927	        case 8388589:
928	          Some{180}
929	        case 8388590:
930	          Some{182}
931	        case 8388591:
932	          Some{183}
933	        case 8388592:
934	          Some{188}
935	        case 8388593:
936	          Some{191}
937	        case 8388594:
938	          Some{197}
939	        case 8388595:
940	          Some{231}
941	        case 8388596:
942	          Some{239}
943	        case _:
944	          None{}
945	    case 24:
946	      match bits:
947	        case 16777194:
948	          Some{9}
949	        case 16777195:
950	          Some{142}
951	        case 16777196:
952	          Some{144}
953	        case 16777197:
954	          Some{145}
955	        case 16777198:
956	          Some{148}
957	        case 16777199:
958	          Some{159}
959	        case 16777200:
960	          Some{171}
961	        case 16777201:
962	          Some{206}
963	        case 16777202:
964	          Some{215}
965	        case 16777203:
966	          Some{225}
967	        case 16777204:
968	          Some{236}
969	        case 16777205:
970	          Some{237}
971	        case _:
972	          None{}
973	    case 25:
974	      match bits:
975	        case 33554412:
976	          Some{199}
977	        case 33554413:
978	          Some{207}
979	        case 33554414:
980	          Some{234}
981	        case 33554415:
982	          Some{235}
983	        case _:
984	          None{}
985	    case 26:
986	      match bits:
987	        case 67108832:
988	          Some{192}
989	        case 67108833:
990	          Some{193}
991	        case 67108834:
992	          Some{200}
993	        case 67108835:
994	          Some{201}
995	        case 67108836:
996	          Some{202}
997	        case 67108837:
998	          Some{205}
999	        case 67108838:
1000	          Some{210}
1001	        case 67108839:
1002	          Some{213}
1003	        case 67108840:
1004	          Some{218}
1005	        case 67108841:
1006	          Some{219}
1007	        case 67108842:
1008	          Some{238}
1009	        case 67108843:
1010	          Some{240}
1011	        case 67108844:
1012	          Some{242}
1013	        case 67108845:
1014	          Some{243}
1015	        case 67108846:
1016	          Some{255}
1017	        case _:
1018	          None{}
1019	    case 27:
1020	      match bits:
1021	        case 134217694:
1022	          Some{203}
1023	        case 134217695:
1024	          Some{204}
1025	        case 134217696:
1026	          Some{211}
1027	        case 134217697:
1028	          Some{212}
1029	        case 134217698:
1030	          Some{214}
1031	        case 134217699:
1032	          Some{221}
1033	        case 134217700:
1034	          Some{222}
1035	        case 134217701:
1036	          Some{223}
1037	        case 134217702:
1038	          Some{241}
1039	        case 134217703:
1040	          Some{244}
1041	        case 134217704:
1042	          Some{245}
1043	        case 134217705:
1044	          Some{246}
1045	        case 134217706:
1046	          Some{247}
1047	        case 134217707:
1048	          Some{248}
1049	        case 134217708:
1050	          Some{250}
1051	        case 134217709:
1052	          Some{251}
1053	        case 134217710:
1054	          Some{252}
1055	        case 134217711:
1056	          Some{253}
1057	        case 134217712:
1058	          Some{254}
1059	        case _:
1060	          None{}
1061	    case 28:
1062	      match bits:
1063	        case 268435426:
1064	          Some{2}
1065	        case 268435427:
1066	          Some{3}
1067	        case 268435428:
1068	          Some{4}
1069	        case 268435429:
1070	          Some{5}
1071	        case 268435430:
1072	          Some{6}
1073	        case 268435431:
1074	          Some{7}
1075	        case 268435432:
1076	          Some{8}
1077	        case 268435433:
1078	          Some{11}
1079	        case 268435434:
1080	          Some{12}
1081	        case 268435435:
1082	          Some{14}
1083	        case 268435436:
1084	          Some{15}
1085	        case 268435437:
1086	          Some{16}
1087	        case 268435438:
1088	          Some{17}
1089	        case 268435439:
1090	          Some{18}
1091	        case 268435440:
1092	          Some{19}
1093	        case 268435441:
1094	          Some{20}
1095	        case 268435442:
1096	          Some{21}
1097	        case 268435443:
1098	          Some{23}
1099	        case 268435444:
1100	          Some{24}
1101	        case 268435445:
1102	          Some{25}
1103	        case 268435446:
1104	          Some{26}
1105	        case 268435447:
1106	          Some{27}
1107	        case 268435448:
1108	          Some{28}
1109	        case 268435449:
1110	          Some{29}
1111	        case 268435450:
1112	          Some{30}
1113	        case 268435451:
1114	          Some{31}
1115	        case 268435452:
1116	          Some{127}
1117	        case 268435453:
1118	          Some{220}
1119	        case 268435454:
1120	          Some{249}
1121	        case _:
1122	          None{}
1123	    case 30:
1124	      match bits:
1125	        case 1073741820:
1126	          Some{10}
1127	        case 1073741821:
1128	          Some{13}
1129	        case 1073741822:
1130	          Some{22}
1131	        case 1073741823:
1132	          Some{256}
1133	        case _:
1134	          None{}
1135	    case _:
1136	      None{}
1137	
1138	def size.valid(ok: Bool, +total: U32, +n: U32) -> Maybe<&2, U32>:
1139	  match ok:
1140	    case True{}:
1141	      Some{(total + n : U32)}
1142	    case False{}:
1143	      None{}
1144	def size.one(+octet: U32, +total: U32) -> Maybe<&2, U32>:
1145	  +n = width(octet)
1146	  size.valid(Bool.and(U32.is_ne(n, 0), U32.is_le(total, (4294967295 - n : U32))), total, n)
1147	
1148	
1149	def size(s: String, +total: U32) -> Maybe<&2, U32>:
1150	  match s:
1151	    case SNil{}:
1152	      Some{total}
1153	    case SCon{Chr{c}, t}:
1154	      do Maybe<&2, U32>:
1155	        n: U32 <- size.one(c, total)
1156	        size(t, n)
1157	
1158	type Builder is Type:
1159	  Builder{bytes: Bytes.Bytes, at: U32, partial: U32, bits: U32}
1160	
1161	def emit.full(full: Bool, out: Bytes.Bytes, +at: U32, +partial: U32, +bits: U32) -> Builder:
1162	  match full:
1163	    case True{}:
1164	      Builder{Bytes.set(out, at, partial), (at + 1 : U32), 0, 0}
1165	    case False{}:
1166	      Builder{out, at, partial, (bits + 1 : U32)}
1167	
1168	def emit.bit(+bit: U32, st: Builder) -> Builder:
1169	  Builder{out, +at, +partial, +bits} = st
1170	  emit.full(U32.is_eq(bits, 7), out, at, ((partial << 1n) .|. bit : U32), bits)
1171	
1172	def emit.bits(n: Nat, +code: U32, st: Builder) -> Builder:
1173	  match n:
1174	    case 0n:
1175	      st
1176	    case 1n+p:
1177	      +p = p
1178	      emit.bits(p, code, emit.bit(((code >> p) .&. 1 : U32), st))
1179	
1180	def emit.code(c: Code, st: Builder) -> Builder:
1181	  match c:
1182	    case Code{bits, width}:
1183	      emit.bits(U32.to_nat(width), bits, st)
1184	
1185	def encode.go(s: String, st: Builder) -> Builder:
1186	  match s:
1187	    case SNil{}:
1188	      st
1189	    case SCon{Chr{c}, t}:
1190	      encode.go(t, emit.code(code(c), st))
1191	
1192	def encode.last(more: Bool, out: Bytes.Bytes, +at: U32, +partial: U32, +bits: U32) -> Bytes.Bytes:
1193	  match more:
1194	    case False{}:
1195	      out
1196	    case True{}:
1197	      +pad = (8 - bits : U32)
1198	      Bytes.set(out, at, ((partial << U32.to_nat(pad)) .|. ((1 << U32.to_nat(pad)) - 1 : U32) : U32))
1199	def encode.finish(st: Builder) -> Bytes.Bytes:
1200	  Builder{out, +at, +partial, +bits} = st
1201	  encode.last(U32.is_ne(bits, 0), out, at, partial, bits)
1202	
1203	
1204	def encode.ready(s: String, m: Maybe<&2, U32>) -> Maybe<&1, Bytes.Bytes>:
1205	  match m:
1206	    case None{}:
1207	      None{}
1208	    case Some{+bits}:
1209	      +len = ((bits >> 3n) + Bool.pick(U32, U32.is_ne((bits .&. 7 : U32), 0), 1, 0) : U32)
1210	      Some{encode.finish(encode.go(s, Builder{Bytes.new(len), 0, 0, 0}))}
1211	
1212	# HPACK text is a byte string: code points above 255 are rejected.
1213	def encode(+s: String) -> Maybe<&1, Bytes.Bytes>:
1214	  encode.ready(s, size(s, 0))
1215	
1216	type Decoder is Data:
1217	  Decoder{bits: U32, width: U32, rev: String}
1218	
1219	def decode.found(+octet: U32, rev: String) -> Maybe<&2, Decoder>:
1220	  match octet:
1221	    case 256:
1222	      None{}
1223	    case _:
1224	      Some{Decoder{0, 0, SCon{Chr{octet}, rev}}}
1225	
1226	def decode.pending(ok: Bool, +bits: U32, +width: U32, rev: String) -> Maybe<&2, Decoder>:
1227	  match ok:
1228	    case True{}:
1229	      Some{Decoder{bits, width, rev}}
1230	    case False{}:
1231	      None{}
1232	def decode.symbol(m: Maybe<&2, U32>, +bits: U32, +width: U32, rev: String) -> Maybe<&2, Decoder>:
1233	  match m:
1234	    case Some{octet}:
1235	      decode.found(octet, rev)
1236	    case None{}:
1237	      decode.pending(U32.is_lt(width, 30), bits, width, rev)
1238	
1239	
1240	def decode.bit(d: Decoder, +bit: U32) -> Maybe<&2, Decoder>:
1241	  Decoder{+bits, +width, rev} = d
1242	  +code = ((bits << 1n) .|. bit : U32)
1243	  +n = (width + 1 : U32)
1244	  decode.symbol(symbol(n, code), code, n, rev)
1245	
1246	def decode.step(n: Nat, +byte: U32, d: Decoder) -> Maybe<&2, Decoder>:
1247	  match n:
1248	    case 0n:
1249	      Some{d}
1250	    case 1n+p:
1251	      +p = p
1252	      do Maybe<&2, Decoder>:
1253	        next: Decoder <- decode.bit(d, ((byte >> p) .&. 1 : U32))
1254	        decode.step(p, byte, next)
1255	
1256	def with_number.got(-R: Type, m: Maybe<&2, U32>, b: Bytes.Bytes, k: Bytes.Bytes -> U32 -> R) -> R:
1257	  match m:
1258	    case Some{v}:
1259	      k(b, v)
1260	    case None{}:
1261	      k(b, 0)
1262	def with_number(-R: Type, r: Bytes.Bytes & Maybe<&2, U32>, k: Bytes.Bytes -> U32 -> R) -> R:
1263	  (b, m) = r
1264	  with_number.got(R, m, b, k)
1265	
1266	
1267	def decode.go(n: Nat, b: Bytes.Bytes, +at: U32, d: Decoder) -> Maybe<&2, Decoder>:
1268	  match n:
1269	    case 0n:
1270	      Some{d}
1271	    case 1n+p:
1272	      with_number(Maybe<&2, Decoder>, Bytes.get(b, at), b => byte =>
1273	        do Maybe<&2, Decoder>:
1274	          next: Decoder <- decode.step(8n, byte, d)
1275	          decode.go(p, b, (at + 1 : U32), next))
1276	
1277	def decode.tail(ok: Bool, rev: String) -> Maybe<&2, String>:
1278	  match ok:
1279	    case True{}:
1280	      Some{String.reverse(rev)}
1281	    case False{}:
1282	      None{}
1283	
1284	def decode.finish(m: Maybe<&2, Decoder>) -> Maybe<&2, String>:
1285	  match m:
1286	    case None{}:
1287	      None{}
1288	    case Some{Decoder{+bits, +width, rev}}:
1289	      decode.tail(Bool.and(U32.is_le(width, 7), U32.is_eq(bits, ((1 << U32.to_nat(width)) - 1 : U32))), rev)
1290	
1291	def decode(b: Bytes.Bytes) -> Maybe<&2, String>:
1292	  Bytes.Bytes{+len, buf} = b
1293	  decode.finish(decode.go(U32.to_nat(len), Bytes.Bytes{len, buf}, 0, Decoder{0, 0, SNil{}}))