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Implement Crystal::System::Random for win32 #5539

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Jan 5, 2018
Merged

Implement Crystal::System::Random for win32 #5539

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10 changes: 8 additions & 2 deletions src/crystal/system/win32/random.cr
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Original file line number Diff line number Diff line change
@@ -1,9 +1,15 @@
require "c/ntsecapi"

module Crystal::System::Random
def self.random_bytes(buf : Bytes) : Nil
raise NotImplementedError.new("Crystal::System::Random.random_bytes")
if LibC.RtlGenRandom(buf, buf.size) == 0
raise WinError.new("RtlGenRandom")
end
end

def self.next_u : UInt8
raise NotImplementedError.new("Crystal::System::Random.next_u")
buf = uninitialized UInt8[1]
random_bytes(buf.to_slice)
buf.unsafe_as(UInt8)
end
end
6 changes: 6 additions & 0 deletions src/lib_c/x86_64-windows-msvc/c/ntsecapi.cr
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@@ -0,0 +1,6 @@
require "./winnt"

@[Link("advapi32")]
lib LibC
fun RtlGenRandom = SystemFunction036(random_buffer : Void*, random_buffer_length : ULong) : BOOLEAN
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Why the alias?

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Nevermind, I guess it's a #define

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RtlGenRandom is what it's called in the windows documentation. The point of keeping the windows names is to be able to find the documentation easilly, so I think this is correct. It's much easier to read this way anyway.

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Have a look to libsodium sysrandom. The function is known as RtlGenRandom, but the symbol is SystemFunction036 and kind of private API, but everybody uses it (libsodium, go, etc) because it avoids bundling the whole crypto API, which is apparently quite big.

An alias, here, is expected, yes :-)

end
1 change: 1 addition & 0 deletions src/lib_c/x86_64-windows-msvc/c/win_def.cr
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@@ -1,4 +1,5 @@
lib LibC
alias WORD = UInt16
alias BOOL = Int32
alias BYTE = UChar
end
3 changes: 3 additions & 0 deletions src/lib_c/x86_64-windows-msvc/c/winnt.cr
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lib LibC
alias BOOLEAN = BYTE
end