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Reimplement random_bytes to be consistent with endianness #2

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Sep 4, 2017
Merged

Reimplement random_bytes to be consistent with endianness #2

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22 changes: 10 additions & 12 deletions src/random.cr
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Original file line number Diff line number Diff line change
Expand Up @@ -298,19 +298,17 @@ module Random
# slice # => [217, 118, 38, 196]
# ```
def random_bytes(buf : Bytes) : Nil
n = buf.size / sizeof(typeof(next_u))
remaining = buf.size - n * sizeof(typeof(next_u))

slice = buf.to_unsafe.as(typeof(next_u)*).to_slice(n)
slice.each_index { |i| slice[i] = next_u }

if remaining > 0
bytes = next_u
remaining.times do |i|
bits = i * 8
mask = typeof(next_u).new(0xff << bits)
buf[-i - 1] = UInt8.new((bytes & mask) >> bits)
ptr = buf.to_unsafe
finish = buf.to_unsafe + buf.size

while ptr < finish
random = next_u
rand_ptr = pointerof(random).as(UInt8*)
if IO::ByteFormat::SystemEndian != IO::ByteFormat::LittleEndian
rand_ptr.to_slice(sizeof(typeof(next_u))).reverse!
end
rand_ptr.copy_to(ptr, {finish - ptr, sizeof(typeof(next_u))}.min)
ptr += sizeof(typeof(next_u))
end
end

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