mirror of
https://github.com/urbit/shrub.git
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137 lines
3.8 KiB
Plaintext
137 lines
3.8 KiB
Plaintext
:: |base64: flexible base64 encoding for little-endian atoms
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::
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:: pad: include padding when encoding, require when decoding
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:: url: use url-safe characters '-' for '+' and '_' for '/'
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::
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=+ [pad=& url=|]
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|%
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::
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+$ byte @D
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+$ word24 @
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::
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++ div-ceil
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:: divide, rounding up.
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|= [x=@ y=@] ^- @
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?: =(0 (mod x y))
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(div x y)
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+((div x y))
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::
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++ explode-bytes
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:: Explode a bytestring into list of bytes. Result is in LSB order.
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|= =octs ^- (list byte)
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=/ atom-byte-width (met 3 q.octs)
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=/ leading-zeros (sub p.octs atom-byte-width)
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(weld (reap leading-zeros 0) (rip 3 q.octs))
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::
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++ explode-words
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:: Explode a bytestring to words of bit-width `wid`. Result is in LSW order.
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|= [wid=@ =octs]
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^- (list @)
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=/ atom-bit-width (met 0 q.octs)
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=/ octs-bit-width (mul 8 p.octs)
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=/ atom-word-width (div-ceil atom-bit-width wid)
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=/ rslt-word-width (div-ceil octs-bit-width wid)
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=/ pad (sub rslt-word-width atom-word-width)
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=/ x (ripn wid q.octs)
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%+ weld x
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(reap pad 0)
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::
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:: +en:base64: encode +octs to base64 cord
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::
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:: Encode an `octs` into a base64 string.
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::
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:: First, we break up the input into a list of 24-bit words. The input
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:: might not be a multiple of 24-bits, so we add 0-2 padding bytes at
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:: the end (to the least-significant side, with a left-shift).
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::
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:: Then, we encode each block into four base64 characters.
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::
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:: Finally we remove the padding that we added at the beginning: for
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:: each byte that was added, we replace one character with an = (unless
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:: `pad` is false, in which case we just remove the extra characters).
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::
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++ en
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^- $-(octs cord)
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::
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=/ cha
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?: url
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'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_'
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'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
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::
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|^ |= bs=octs ^- cord
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=/ [padding=@ blocks=(list word24)]
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(octs-to-blocks bs)
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(crip (flop (unpad padding (encode-blocks blocks))))
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::
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++ octs-to-blocks
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|= bs=octs ^- [padding=@ud (list word24)]
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=/ padding=@ud (~(dif fo 3) 0 p.bs)
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=/ padded=octs [(add padding p.bs) (lsh 3 padding (rev 3 bs))]
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[padding (explode-words 24 padded)]
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::
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++ unpad
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|= [extra=@ t=tape] ^- tape
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=/ without (slag extra t)
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?. pad without
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(weld (reap extra '=') without)
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::
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++ encode-blocks
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|= ws=(list word24) ^- tape
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(zing (turn ws encode-block))
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::
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++ encode-block
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|= w=word24 ^- tape
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=/ a (cut 3 [(cut 0 [0 6] w) 1] cha)
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=/ b (cut 3 [(cut 0 [6 6] w) 1] cha)
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=/ c (cut 3 [(cut 0 [12 6] w) 1] cha)
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=/ d (cut 3 [(cut 0 [18 6] w) 1] cha)
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~[a b c d]
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--
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::
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:: +de:base64: decode base64 cord to (unit @)
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::
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++ de
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|= a=cord
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^- (unit octs)
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(rush a parse)
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:: +parse:base64: parse base64 cord to +octs
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::
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++ parse
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=< ^- $-(nail (like octs))
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%+ sear reduce
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;~ plug
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%- plus ;~ pose
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(cook |=(a=@ (sub a 'A')) (shim 'A' 'Z'))
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(cook |=(a=@ (sub a 'G')) (shim 'a' 'z'))
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(cook |=(a=@ (add a 4)) (shim '0' '9'))
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(cold 62 (just ?:(url '-' '+')))
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(cold 63 (just ?:(url '_' '/')))
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==
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(stun 0^2 (cold %0 tis))
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==
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|%
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:: +reduce:parse:base64: reduce, measure, and swap base64 digits
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::
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++ reduce
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|= [dat=(list @) dap=(list @)]
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^- (unit octs)
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=/ lat (lent dat)
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=/ lap (lent dap)
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=/ dif (~(dif fo 4) 0 lat)
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?: &(pad !=(dif lap))
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:: padding required and incorrect
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~&(%base-64-padding-err-one ~)
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?: &(!pad !=(0 lap))
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:: padding not required but present
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~&(%base-64-padding-err-two ~)
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=/ len (sub (mul 3 (div (add lat dif) 4)) dif)
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:+ ~ len
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%+ swp 3
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:: %+ base 64
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%+ roll
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(weld dat (reap dif 0))
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|=([p=@ q=@] (add p (mul 64 q)))
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--
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--
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