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package encoding_base32
// @note(zh): Encoding utility for Base32
// A secondary param can be used to supply a custom alphabet to
// @link(encode) and a matching decoding table to @link(decode).
// If none is supplied it just uses the standard Base32 alphabet.
// Incase your specific version does not use padding, you may
// truncate it from the encoded output.
ENC_TABLE := [32]byte {
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
'Y', 'Z', '2', '3', '4', '5', '6', '7',
}
PADDING :: '='
DEC_TABLE := [?]u8 {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 26, 27, 28, 29, 30, 31, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 0, 0, 0, 0, 0,
0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
}
encode :: proc(data: []byte, ENC_TBL := ENC_TABLE, allocator := context.allocator) -> string {
out_length := (len(data) + 4) / 5 * 8
out := make([]byte, out_length)
_encode(out, data)
return string(out)
}
@private
_encode :: proc(out, data: []byte, ENC_TBL := ENC_TABLE, allocator := context.allocator) {
out := out
data := data
for len(data) > 0 {
carry: byte
switch len(data) {
case:
out[7] = ENC_TABLE[data[4] & 0x1f]
carry = data[4] >> 5
fallthrough
case 4:
out[6] = ENC_TABLE[carry | (data[3] << 3) & 0x1f]
out[5] = ENC_TABLE[(data[3] >> 2) & 0x1f]
carry = data[3] >> 7
fallthrough
case 3:
out[4] = ENC_TABLE[carry | (data[2] << 1) & 0x1f]
carry = (data[2] >> 4) & 0x1f
fallthrough
case 2:
out[3] = ENC_TABLE[carry | (data[1] << 4) & 0x1f]
out[2] = ENC_TABLE[(data[1] >> 1) & 0x1f]
carry = (data[1] >> 6) & 0x1f
fallthrough
case 1:
out[1] = ENC_TABLE[carry | (data[0] << 2) & 0x1f]
out[0] = ENC_TABLE[data[0] >> 3]
}
if len(data) < 5 {
out[7] = byte(PADDING)
if len(data) < 4 {
out[6] = byte(PADDING)
out[5] = byte(PADDING)
if len(data) < 3 {
out[4] = byte(PADDING)
if len(data) < 2 {
out[3] = byte(PADDING)
out[2] = byte(PADDING)
}
}
}
break
}
data = data[5:]
out = out[8:]
}
}
decode :: proc(data: string, DEC_TBL := DEC_TABLE, allocator := context.allocator) -> []byte #no_bounds_check{
if len(data) == 0 {
return nil
}
outi := 0
data := data
out := make([]byte, len(data) / 8 * 5, allocator)
end := false
for len(data) > 0 && !end {
dbuf : [8]byte
dlen := 8
for j := 0; j < 8; {
if len(data) == 0 {
dlen, end = j, true
break
}
input := data[0]
data = data[1:]
if input == byte(PADDING) && j >= 2 && len(data) < 8 {
assert(!(len(data) + j < 8 - 1), "Corrupted input")
for k := 0; k < 8-1-j; k +=1 {
assert(len(data) < k || data[k] == byte(PADDING), "Corrupted input")
}
dlen, end = j, true
assert(dlen != 1 && dlen != 3 && dlen != 6, "Corrupted input")
break
}
dbuf[j] = DEC_TABLE[input]
assert(dbuf[j] != 0xff, "Corrupted input")
j += 1
}
switch dlen {
case 8:
out[outi + 4] = dbuf[6] << 5 | dbuf[7]
fallthrough
case 7:
out[outi + 3] = dbuf[4] << 7 | dbuf[5] << 2 | dbuf[6] >> 3
fallthrough
case 5:
out[outi + 2] = dbuf[3] << 4 | dbuf[4] >> 1
fallthrough
case 4:
out[outi + 1] = dbuf[1] << 6 | dbuf[2] << 1 | dbuf[3] >> 4
fallthrough
case 2:
out[outi + 0] = dbuf[0] << 3 | dbuf[1] >> 2
}
outi += 5
}
return out
}
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