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polyUnpackT0

Unpack polynomial with coefficients in (-2^(D-1), 2^(D-1)] (T0) from bytes. Output coefficients will not be normalized, but in (-2^(D-1), 2^(D-1)].

ml_dsa.polyUnpackT0

fn polyUnpackT0(buf: []const u8) Poly

File

lib/std/crypto/ml_dsa.zig:1105

Code

fn polyUnpackT0(buf: []const u8) Poly {
    const bound = 1 << (D - 1);
    var p = Poly.zero;
    var j: usize = 0;
    var i: usize = 0;
    while (i < buf.len) : (i += 13) {
        p.cs[j] = Q + bound - ((@as(u32, buf[i]) | (@as(u32, buf[i + 1]) << 8)) & 0x1fff);
        p.cs[j + 1] = Q + bound - (((@as(u32, buf[i + 1]) >> 5) | (@as(u32, buf[i + 2]) << 3) | (@as(u32, buf[i + 3]) << 11)) & 0x1fff);
        p.cs[j + 2] = Q + bound - (((@as(u32, buf[i + 3]) >> 2) | (@as(u32, buf[i + 4]) << 6)) & 0x1fff);
        p.cs[j + 3] = Q + bound - (((@as(u32, buf[i + 4]) >> 7) | (@as(u32, buf[i + 5]) << 1) | (@as(u32, buf[i + 6]) << 9)) & 0x1fff);
        p.cs[j + 4] = Q + bound - (((@as(u32, buf[i + 6]) >> 4) | (@as(u32, buf[i + 7]) << 4) | (@as(u32, buf[i + 8]) << 12)) & 0x1fff);
        p.cs[j + 5] = Q + bound - (((@as(u32, buf[i + 8]) >> 1) | (@as(u32, buf[i + 9]) << 7)) & 0x1fff);
        p.cs[j + 6] = Q + bound - (((@as(u32, buf[i + 9]) >> 6) | (@as(u32, buf[i + 10]) << 2) | (@as(u32, buf[i + 11]) << 10)) & 0x1fff);
        p.cs[j + 7] = Q + bound - ((@as(u32, buf[i + 11]) >> 3) | (@as(u32, buf[i + 12]) << 5));
        j += 8;
    }
    return p;
}