55 lines
2.3 KiB
Plaintext
55 lines
2.3 KiB
Plaintext
#!/usr/bin/env nomsu -V2.5.5.4
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#
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This file defines actions for encoding/decoding base 64, as specified in:
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https://tools.ietf.org/html/rfc4648
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%b64_str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
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%reverse_b64 = (%b64_str.%i = (%i - 1) for %i in 1 to (length of %b64_str))
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%reverse_b64."=" = 0
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test:
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%cases = ["", "Zg==", "Zm8=", "Zm9v", "Zm9vYg==", "Zm9vYmE=", "Zm9vYmFy"]
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for %len = %encoded in %cases:
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%plain = "foobar".[1, %len - 1]
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assume ((base64 %plain) == %encoded) or barf ".."
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\(quote %plain) base64 encoded to \(quote (base64 %plain)) \
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..instead of \(quote %encoded)
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assume ((base64 decode %encoded) == %plain) or barf ".."
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\(quote %encoded) base64 decoded to \(quote (base64 decode %encoded)) \
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..instead of \(quote %plain)
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action [base64 %str, base64 encode %str, %str base64]:
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%chars = []
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for %i in 1 to (length of %str) via 3:
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%bytes = [=lua "\%str:byte(\%i, \(%i + 2))"]
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add %b64_str.(((%bytes.1 & 252) >> 2) + 1) to %chars
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if (length of %bytes) is:
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3:
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add %b64_str.(((%bytes.1 & 3) << 4) + ((%bytes.2 & 240) >> 4) + 1) to %chars
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add %b64_str.(((%bytes.2 & 15) << 2) + ((%bytes.3 & 192) >> 6) + 1) to %chars
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add %b64_str.((%bytes.3 & 63) + 1) to %chars
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2:
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add %b64_str.(((%bytes.1 & 3) << 4) + ((%bytes.2 & 240) >> 4) + 1) to %chars
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add %b64_str.(((%bytes.2 & 15) << 2) + 1) to %chars
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add "=" to %chars
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1:
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add %b64_str.(((%bytes.1 & 3) << 4) + 1) to %chars
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add "=" to %chars
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add "=" to %chars
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return (%chars joined)
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action [chr %] (=lua "string.char(\%)")
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action [decode base64 %str, %str base64 decoded, base64 decode %str]:
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%chars = []
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for %i in 1 to (length of %str) via 4:
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%indices = (%reverse_b64.(%str.%) for % in %i to (%i + 3))
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add (chr ((%indices.1 << 2) + ((%indices.2 & 48) >> 4))) to %chars
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if (%str.(%i + 2) == "="): stop
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add (chr (((%indices.2 & 15) << 4) + ((%indices.3 & 60) >> 2))) to %chars
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if (%str.(%i + 3) == "="): stop
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add (chr (((%indices.3 & 3) << 6) + %indices.4)) to %chars
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return (%chars joined)
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