24 lines
658 B
Ada
24 lines
658 B
Ada
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-- Package body for crc checksum
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-- Copyright Fil Andrii root.fi36@gmail.com 2022
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package body X25CRC is
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procedure Reset (Element : in out Checksum) is
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begin
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Element.Low := 16#FF#;
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Element.High := 16#FF#;
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end Reset;
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procedure Update (Element : in out Checksum; Value : Unsigned_8) is
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use type Unsigned_16;
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Tmp : Unsigned_16;
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begin
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Tmp := Unsigned_16 (Value) xor (Element.Value and 16#FF#);
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Tmp := (Tmp xor Shift_Left (Tmp, 4)) and 16#FF#;
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Element.Value :=
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Shift_Right (Element.Value, 8) xor Shift_Left (Tmp, 8) xor Shift_Left (Tmp, 3) xor Shift_Right (Tmp, 4);
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end Update;
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end X25CRC;
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