Zig 0.17.0-dev (Split by item)

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sbox_lookup

soft.sbox_lookup
fn sbox_lookup(sbox: *align(64) const [256]u8, idx0: u8, idx1: u8, idx2: u8, idx3: u8) [4]u8

File

lib/std/crypto/aes/soft.zig:815

Code

fn sbox_lookup(sbox: *align(64) const [256]u8, idx0: u8, idx1: u8, idx2: u8, idx3: u8) [4]u8 {
    if (side_channels_mitigations == .none) {
        return [4]u8{
            sbox[idx0],
            sbox[idx1],
            sbox[idx2],
            sbox[idx3],
        };
    } else {
        const stride = switch (side_channels_mitigations) {
            .none => unreachable,
            .basic => sbox.len / 4,
            .medium => @min(sbox.len, 2 * cache_line_bytes),
            .full => @min(sbox.len, cache_line_bytes),
        };
        const of0 = idx0 % stride;
        const of1 = idx1 % stride;
        const of2 = idx2 % stride;
        const of3 = idx3 % stride;
        var t: [4][sbox.len / stride]u8 align(64) = undefined;
        var i: usize = 0;
        while (i < t[0].len) : (i += 1) {
            const tx = sbox[i * stride ..];
            t[0][i] = tx[of0];
            t[1][i] = tx[of1];
            t[2][i] = tx[of2];
            t[3][i] = tx[of3];
        }
        std.mem.doNotOptimizeAway(t);
        return [4]u8{
            t[0][idx0 / stride],
            t[1][idx1 / stride],
            t[2][idx2 / stride],
            t[3][idx3 / stride],
        };
    }
}