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scheler/gist:26a942d34fb5576a68c111b05ac3fabe

Created July 23, 2020 00:17
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String hash function in Lua
Raw
gistfile1.txt
function hash(str)
h = 5381;
for c in str:gmatch"." do
h = ((h << 5) + h) + string.byte(c)
end
return h
end
@karelbilek
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(I am not sure if the h*32 + h or h<<5 + h is really faster than just h*33 )

@jarom-nelson
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jarom-nelson commented Oct 10, 2024 •
edited
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You'll want to mod by 2^31 to keep it within 32 bits or you'll get a double floating point number eventually.

function hash(str)
    h = 5381;

    for c in str:gmatch"." do
        h = math.fmod(((h << 5) + h) + string.byte(c), 2147483648)
    end
    return h
end

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