const CONST_BITS: i32 = 13;
const PASS1_BITS: i32 = 2;
const FIX_0_298631336: i32 = 2446;
const FIX_0_390180644: i32 = 3196;
const FIX_0_541196100: i32 = 4433;
const FIX_0_765366865: i32 = 6270;
const FIX_0_899976223: i32 = 7373;
const FIX_1_175875602: i32 = 9633;
const FIX_1_501321110: i32 = 12299;
const FIX_1_847759065: i32 = 15137;
const FIX_1_961570560: i32 = 16069;
const FIX_2_053119869: i32 = 16819;
const FIX_2_562915447: i32 = 20995;
const FIX_3_072711026: i32 = 25172;
const DCT_SIZE: usize = 8;
#[inline(always)]
fn descale(x: i32, n: i32) -> i32 {
(x + (1 << (n - 1))) >> n
}
#[inline(always)]
fn into_el(v: i32) -> i16 {
v as i16
}
#[allow(clippy::erasing_op)]
#[allow(clippy::identity_op)]
pub(crate) fn fdct(data: &mut [i16; 64]) {
for y in 0..8 {
let offset = y * 8;
let tmp0 = i32::from(data[offset + 0]) + i32::from(data[offset + 7]);
let tmp7 = i32::from(data[offset + 0]) - i32::from(data[offset + 7]);
let tmp1 = i32::from(data[offset + 1]) + i32::from(data[offset + 6]);
let tmp6 = i32::from(data[offset + 1]) - i32::from(data[offset + 6]);
let tmp2 = i32::from(data[offset + 2]) + i32::from(data[offset + 5]);
let tmp5 = i32::from(data[offset + 2]) - i32::from(data[offset + 5]);
let tmp3 = i32::from(data[offset + 3]) + i32::from(data[offset + 4]);
let tmp4 = i32::from(data[offset + 3]) - i32::from(data[offset + 4]);
let tmp10 = tmp0 + tmp3;
let tmp13 = tmp0 - tmp3;
let tmp11 = tmp1 + tmp2;
let tmp12 = tmp1 - tmp2;
data[offset + 0] = into_el((tmp10 + tmp11) << PASS1_BITS);
data[offset + 4] = into_el((tmp10 - tmp11) << PASS1_BITS);
let z1 = (tmp12 + tmp13) * FIX_0_541196100;
data[offset + 2] = into_el(descale(
z1 + (tmp13 * FIX_0_765366865),
CONST_BITS - PASS1_BITS,
));
data[offset + 6] = into_el(descale(
z1 + (tmp12 * -FIX_1_847759065),
CONST_BITS - PASS1_BITS,
));
let z1 = tmp4 + tmp7;
let z2 = tmp5 + tmp6;
let z3 = tmp4 + tmp6;
let z4 = tmp5 + tmp7;
let z5 = (z3 + z4) * FIX_1_175875602;
let tmp4 = tmp4 * FIX_0_298631336;
let tmp5 = tmp5 * FIX_2_053119869;
let tmp6 = tmp6 * FIX_3_072711026;
let tmp7 = tmp7 * FIX_1_501321110;
let z1 = z1 * -FIX_0_899976223;
let z2 = z2 * -FIX_2_562915447;
let z3 = z3 * -FIX_1_961570560;
let z4 = z4 * -FIX_0_390180644;
let z3 = z3 + z5;
let z4 = z4 + z5;
data[offset + 7] = into_el(descale(tmp4 + z1 + z3, CONST_BITS - PASS1_BITS));
data[offset + 5] = into_el(descale(tmp5 + z2 + z4, CONST_BITS - PASS1_BITS));
data[offset + 3] = into_el(descale(tmp6 + z2 + z3, CONST_BITS - PASS1_BITS));
data[offset + 1] = into_el(descale(tmp7 + z1 + z4, CONST_BITS - PASS1_BITS));
}
for x in 0..8 {
let tmp0 = i32::from(data[DCT_SIZE * 0 + x]) + i32::from(data[DCT_SIZE * 7 + x]);
let tmp7 = i32::from(data[DCT_SIZE * 0 + x]) - i32::from(data[DCT_SIZE * 7 + x]);
let tmp1 = i32::from(data[DCT_SIZE * 1 + x]) + i32::from(data[DCT_SIZE * 6 + x]);
let tmp6 = i32::from(data[DCT_SIZE * 1 + x]) - i32::from(data[DCT_SIZE * 6 + x]);
let tmp2 = i32::from(data[DCT_SIZE * 2 + x]) + i32::from(data[DCT_SIZE * 5 + x]);
let tmp5 = i32::from(data[DCT_SIZE * 2 + x]) - i32::from(data[DCT_SIZE * 5 + x]);
let tmp3 = i32::from(data[DCT_SIZE * 3 + x]) + i32::from(data[DCT_SIZE * 4 + x]);
let tmp4 = i32::from(data[DCT_SIZE * 3 + x]) - i32::from(data[DCT_SIZE * 4 + x]);
let tmp10 = tmp0 + tmp3;
let tmp13 = tmp0 - tmp3;
let tmp11 = tmp1 + tmp2;
let tmp12 = tmp1 - tmp2;
data[DCT_SIZE * 0 + x] = into_el(descale(tmp10 + tmp11, PASS1_BITS));
data[DCT_SIZE * 4 + x] = into_el(descale(tmp10 - tmp11, PASS1_BITS));
let z1 = (tmp12 + tmp13) * FIX_0_541196100;
data[DCT_SIZE * 2 + x] = into_el(descale(
z1 + tmp13 * FIX_0_765366865,
CONST_BITS + PASS1_BITS,
));
data[DCT_SIZE * 6 + x] = into_el(descale(
z1 + tmp12 * -FIX_1_847759065,
CONST_BITS + PASS1_BITS,
));
let z1 = tmp4 + tmp7;
let z2 = tmp5 + tmp6;
let z3 = tmp4 + tmp6;
let z4 = tmp5 + tmp7;
let z5 = (z3 + z4) * FIX_1_175875602;
let tmp4 = tmp4 * FIX_0_298631336;
let tmp5 = tmp5 * FIX_2_053119869;
let tmp6 = tmp6 * FIX_3_072711026;
let tmp7 = tmp7 * FIX_1_501321110;
let z1 = z1 * -FIX_0_899976223;
let z2 = z2 * -FIX_2_562915447;
let z3 = z3 * -FIX_1_961570560;
let z4 = z4 * -FIX_0_390180644;
let z3 = z3 + z5;
let z4 = z4 + z5;
data[DCT_SIZE * 7 + x] = into_el(descale(tmp4 + z1 + z3, CONST_BITS + PASS1_BITS));
data[DCT_SIZE * 5 + x] = into_el(descale(tmp5 + z2 + z4, CONST_BITS + PASS1_BITS));
data[DCT_SIZE * 3 + x] = into_el(descale(tmp6 + z2 + z3, CONST_BITS + PASS1_BITS));
data[DCT_SIZE * 1 + x] = into_el(descale(tmp7 + z1 + z4, CONST_BITS + PASS1_BITS));
}
}
#[cfg(test)]
mod tests {
use super::fdct;
const INPUT1: [i16; 64] = [
-70, -71, -70, -68, -67, -67, -67, -67, -72, -73, -72, -70, -69, -69, -68, -69, -75, -76,
-74, -73, -73, -72, -71, -70, -77, -78, -77, -75, -76, -75, -73, -71, -78, -77, -77, -76,
-79, -77, -76, -75, -78, -78, -77, -77, -77, -77, -78, -77, -79, -79, -78, -78, -78, -78,
-79, -78, -80, -79, -78, -78, -81, -80, -78, -76,
];
const OUTPUT1: [i16; 64] = [
-4786, -66, 2, -18, 12, 12, 5, -7, 223, -37, -8, 21, 8, 5, -4, 6, 60, 6, -10, 5, 0, -2, -1,
5, 21, 21, -15, 12, -2, -7, 1, 0, -2, -5, 16, -15, 0, 5, -4, -8, 0, -7, -4, 6, 7, -4, 5, 4,
3, 0, 1, -5, 0, -1, 4, 1, -5, 7, 0, -3, -6, 1, 1, -4,
];
const INPUT2: [i16; 64] = [
21, 28, 11, 24, -45, -37, -55, -103, 38, -8, 31, 17, -19, 49, 15, -76, 22, -48, -36, -31,
-23, 35, -23, -72, 13, -30, -45, -42, -44, -15, -20, -44, 13, -30, -45, -42, -44, -15, -20,
-44, 13, -30, -45, -42, -44, -15, -20, -44, 13, -30, -45, -42, -44, -15, -20, -44, 13, -30,
-45, -42, -44, -15, -20, -44,
];
const OUTPUT2: [i16; 64] = [
-1420, 717, 187, 910, -244, 579, 222, -191, 461, 487, -497, -29, -220, 179, 63, -95, 213,
414, -235, -187, -108, 74, -73, -70, -63, 311, 13, -290, 17, -38, -180, -47, -254, 201,
116, -247, 102, -109, -185, -36, -310, 107, 73, -91, 126, -121, -99, -37, -253, 43, -15,
53, 101, -91, -3, -37, -136, 12, -44, 81, 53, -45, 31, -24,
];
#[test]
pub fn test_fdct_libjpeg() {
let mut i1 = INPUT1.clone();
fdct(&mut i1);
assert_eq!(i1, OUTPUT1);
let mut i2 = INPUT2.clone();
fdct(&mut i2);
assert_eq!(i2, OUTPUT2);
}
}