nim-websock/src/random.nim

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import bearssl
## Random helpers: similar as in stdlib, but with BrHmacDrbgContext rng
const randMax = 18_446_744_073_709_551_615'u64
proc rand*(rng: var BrHmacDrbgContext, max: Natural): int =
if max == 0: return 0
var x: uint64
while true:
brHmacDrbgGenerate(addr rng, addr x, csize_t(sizeof(x)))
if x < randMax - (randMax mod (uint64(max) + 1'u64)): # against modulo bias
return int(x mod (uint64(max) + 1'u64))
proc genMaskKey*(rng: ref BrHmacDrbgContext): array[4, char] =
## Generates a random key of 4 random chars.
proc r(): char = char(rand(rng[], 255))
return [r(), r(), r(), r()]
proc genWebSecKey*(rng: ref BrHmacDrbgContext): seq[char] =
var key = newSeq[char](16)
proc r(): char = char(rand(rng[], 255))
## Generates a random key of 16 random chars.
for i in 0..15:
key.add(r())
return key