1	import Base
2	import ./buffer.bend as Buffer
3	
4	# Sole production hash API. Packed input and output, four bytes per U32,
5	# big-endian. Consumes input; returns exactly eight words, or None for an
6	# oversized byte length. No byte-list or digest-list compatibility API.
7	def sha256(words: Array<U32>, byte_length: Nat) -> Maybe<&1,Array<U32>>:
8	  Buffer.sha256(words,byte_length)
9	
10	def hex_digit_if(x: U32, small: Bool) -> Char:
11	  match small:
12	    case True{}:
13	      Chr{(48 + x : U32)}
14	    case False{}:
15	      Chr{(87 + x : U32)}
16	
17	def hex_digit(+x: U32) -> Char:
18	  hex_digit_if(x, U32.is_lt(x, 10))
19	
20	def hex_word_go(n: Nat, +x: U32, acc: String) -> String:
21	  match n:
22	    case 0n:
23	      acc
24	    case 1n+p:
25	      hex_word_go(p, U32.shrn(x, 4n), SCon{hex_digit((x .&. 15 : U32)), acc})
26	
27	def hex_word(x: U32) -> String:
28	  hex_word_go(8n, x, "")
29	
30	# Formatting helper consumes eight words; it does not create a digest list.
31	def hex_walk(n: Nat, +index: U32, pair: Array<U32> & U32) -> String:
32	  match n pair:
33	    case 0n Tuple{a,w}: hex_word(w)
34	    case 1n+p Tuple{a,w}: hex_word(w) ++ hex_walk(p,U32.inc(index),Array.get(U32,a,index))
35	
36	def hex(a: Array<U32>) -> String:
37	  hex_walk(7n,1,Array.get(U32,a,0))