j2k-codec-math 0.7.1

// SPDX-License-Identifier: MIT OR Apache-2.0

//! Shared JPEG 2000 classic Tier-1 probability and context tables.

/// One JPEG 2000 MQ probability-state transition.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct ClassicMqState {
    /// Probability estimate.
    pub qe: u32,
    /// Next state after an MPS event.
    pub nmps: u8,
    /// Next state after an LPS event.
    pub nlps: u8,
    /// Whether an LPS event switches the MPS bit.
    pub switch: bool,
}

macro_rules! mq_states {
    ($($qe:expr, $nmps:expr, $nlps:expr, $switch:expr),+ $(,)?) => {
        [$(ClassicMqState { qe: $qe, nmps: $nmps, nlps: $nlps, switch: $switch }),+]
    };
}

/// MQ values and state transitions from ITU-T T.800 Table C.2.
#[rustfmt::skip]
pub const MQ_STATES: [ClassicMqState; 47] = mq_states!(
    0x5601, 1, 1, true,
    0x3401, 2, 6, false,
    0x1801, 3, 9, false,
    0x0AC1, 4, 12, false,
    0x0521, 5, 29, false,
    0x0221, 38, 33, false,
    0x5601, 7, 6, true,
    0x5401, 8, 14, false,
    0x4801, 9, 14, false,
    0x3801, 10, 14, false,
    0x3001, 11, 17, false,
    0x2401, 12, 18, false,
    0x1C01, 13, 20, false,
    0x1601, 29, 21, false,
    0x5601, 15, 14, true,
    0x5401, 16, 14, false,
    0x5101, 17, 15, false,
    0x4801, 18, 16, false,
    0x3801, 19, 17, false,
    0x3401, 20, 18, false,
    0x3001, 21, 19, false,
    0x2801, 22, 19, false,
    0x2401, 23, 20, false,
    0x2201, 24, 21, false,
    0x1C01, 25, 22, false,
    0x1801, 26, 23, false,
    0x1601, 27, 24, false,
    0x1401, 28, 25, false,
    0x1201, 29, 26, false,
    0x1101, 30, 27, false,
    0x0AC1, 31, 28, false,
    0x09C1, 32, 29, false,
    0x08A1, 33, 30, false,
    0x0521, 34, 31, false,
    0x0441, 35, 32, false,
    0x02A1, 36, 33, false,
    0x0221, 37, 34, false,
    0x0141, 38, 35, false,
    0x0111, 39, 36, false,
    0x0085, 40, 37, false,
    0x0049, 41, 38, false,
    0x0025, 42, 39, false,
    0x0015, 43, 40, false,
    0x0009, 44, 41, false,
    0x0005, 45, 42, false,
    0x0001, 45, 43, false,
    0x5601, 46, 46, false,
);

const fn mq_qe_values() -> [u32; 47] {
    let mut values = [0; 47];
    let mut index = 0;
    while index < values.len() {
        values[index] = MQ_STATES[index].qe;
        index += 1;
    }
    values
}

const fn packed_mq_transitions() -> [u32; 47] {
    let mut values = [0; 47];
    let mut index = 0;
    while index < values.len() {
        let state = MQ_STATES[index];
        values[index] =
            state.nmps as u32 | ((state.nlps as u32) << 8) | ((state.switch as u32) << 16);
        index += 1;
    }
    values
}

/// Primitive MQ probability values for device compilers that cannot lower arrays of structs.
pub const MQ_QE_VALUES: [u32; 47] = mq_qe_values();
/// Packed MQ MPS/LPS transitions and switch flag for device lookup tables.
pub const PACKED_MQ_TRANSITION_VALUES: [u32; 47] = packed_mq_transitions();

/// Sign-coding context and XOR bit indexed by packed cardinal-neighbor state.
#[rustfmt::skip]
pub const SIGN_CONTEXT_LOOKUP: [(u8, u8); 256] = [
    (9,0), (10,0), (10,1), (0,0), (12,0), (13,0), (11,0), (0,0), (12,1), (11,1),
    (13,1), (0,0), (0,0), (0,0), (0,0), (0,0), (12,0), (13,0), (11,0), (0,0),
    (12,0), (13,0), (11,0), (0,0), (9,0), (10,0), (10,1), (0,0), (0,0), (0,0),
    (0,0), (0,0), (12,1), (11,1), (13,1), (0,0), (9,0), (10,0), (10,1), (0,0),
    (12,1), (11,1), (13,1), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0),
    (0,0), (0,0), (0,0), (10,0), (10,0), (9,0), (0,0), (13,0), (13,0), (12,0),
    (0,0), (11,1), (11,1), (12,1), (0,0), (0,0), (0,0), (0,0), (0,0), (13,0),
    (13,0), (12,0), (0,0), (13,0), (13,0), (12,0), (0,0), (10,0), (10,0), (9,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (11,1), (11,1), (12,1), (0,0), (10,0),
    (10,0), (9,0), (0,0), (11,1), (11,1), (12,1), (0,0), (0,0), (0,0), (0,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (10,1), (9,0), (10,1), (0,0),
    (11,0), (12,0), (11,0), (0,0), (13,1), (12,1), (13,1), (0,0), (0,0), (0,0),
    (0,0), (0,0), (11,0), (12,0), (11,0), (0,0), (11,0), (12,0), (11,0), (0,0),
    (10,1), (9,0), (10,1), (0,0), (0,0), (0,0), (0,0), (0,0), (13,1), (12,1),
    (13,1), (0,0), (10,1), (9,0), (10,1), (0,0), (13,1), (12,1), (13,1), (0,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0),
    (0,0), (0,0), (0,0), (0,0), (0,0), (0,0), (0,0),
];

const fn packed_sign_contexts() -> [u16; 256] {
    let mut values = [0; 256];
    let mut index = 0;
    while index < values.len() {
        let (context, xor) = SIGN_CONTEXT_LOOKUP[index];
        values[index] = context as u16 | ((xor as u16) << 8);
        index += 1;
    }
    values
}

/// Packed sign context in the low byte and XOR bit in the high byte.
pub const PACKED_SIGN_CONTEXT_LOOKUP: [u16; 256] = packed_sign_contexts();

/// Zero-coding contexts for LL and LH sub-bands.
#[rustfmt::skip]
pub const ZERO_CTX_LL_LH_LOOKUP: [u8; 256] = [
    0, 3, 1, 3, 5, 7, 6, 7, 1, 3, 2, 3, 6, 7, 6, 7, 5, 7, 6, 7, 8, 8, 8, 8, 6,
    7, 6, 7, 8, 8, 8, 8, 1, 3, 2, 3, 6, 7, 6, 7, 2, 3, 2, 3, 6, 7, 6, 7, 6, 7,
    6, 7, 8, 8, 8, 8, 6, 7, 6, 7, 8, 8, 8, 8, 3, 4, 3, 4, 7, 7, 7, 7, 3, 4, 3,
    4, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 7, 7, 7, 7, 8, 8, 8, 8, 3, 4, 3, 4,
    7, 7, 7, 7, 3, 4, 3, 4, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 7, 7, 7, 7, 8,
    8, 8, 8, 1, 3, 2, 3, 6, 7, 6, 7, 2, 3, 2, 3, 6, 7, 6, 7, 6, 7, 6, 7, 8, 8,
    8, 8, 6, 7, 6, 7, 8, 8, 8, 8, 2, 3, 2, 3, 6, 7, 6, 7, 2, 3, 2, 3, 6, 7, 6,
    7, 6, 7, 6, 7, 8, 8, 8, 8, 6, 7, 6, 7, 8, 8, 8, 8, 3, 4, 3, 4, 7, 7, 7, 7,
    3, 4, 3, 4, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 7, 7, 7, 7, 8, 8, 8, 8, 3,
    4, 3, 4, 7, 7, 7, 7, 3, 4, 3, 4, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 7, 7,
    7, 7, 8, 8, 8, 8,
];

/// Zero-coding contexts for HL sub-bands.
#[rustfmt::skip]
pub const ZERO_CTX_HL_LOOKUP: [u8; 256] = [
    0, 5, 1, 6, 3, 7, 3, 7, 1, 6, 2, 6, 3, 7, 3, 7, 3, 7, 3, 7, 4, 7, 4, 7, 3,
    7, 3, 7, 4, 7, 4, 7, 1, 6, 2, 6, 3, 7, 3, 7, 2, 6, 2, 6, 3, 7, 3, 7, 3, 7,
    3, 7, 4, 7, 4, 7, 3, 7, 3, 7, 4, 7, 4, 7, 5, 8, 6, 8, 7, 8, 7, 8, 6, 8, 6,
    8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 6, 8, 6, 8,
    7, 8, 7, 8, 6, 8, 6, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7,
    8, 7, 8, 1, 6, 2, 6, 3, 7, 3, 7, 2, 6, 2, 6, 3, 7, 3, 7, 3, 7, 3, 7, 4, 7,
    4, 7, 3, 7, 3, 7, 4, 7, 4, 7, 2, 6, 2, 6, 3, 7, 3, 7, 2, 6, 2, 6, 3, 7, 3,
    7, 3, 7, 3, 7, 4, 7, 4, 7, 3, 7, 3, 7, 4, 7, 4, 7, 6, 8, 6, 8, 7, 8, 7, 8,
    6, 8, 6, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 6,
    8, 6, 8, 7, 8, 7, 8, 6, 8, 6, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8,
    7, 8, 7, 8, 7, 8,
];

/// Zero-coding contexts for HH sub-bands.
#[rustfmt::skip]
pub const ZERO_CTX_HH_LOOKUP: [u8; 256] = [
    0, 1, 3, 4, 1, 2, 4, 5, 3, 4, 6, 7, 4, 5, 7, 7, 1, 2, 4, 5, 2, 2, 5, 5, 4,
    5, 7, 7, 5, 5, 7, 7, 3, 4, 6, 7, 4, 5, 7, 7, 6, 7, 8, 8, 7, 7, 8, 8, 4, 5,
    7, 7, 5, 5, 7, 7, 7, 7, 8, 8, 7, 7, 8, 8, 1, 2, 4, 5, 2, 2, 5, 5, 4, 5, 7,
    7, 5, 5, 7, 7, 2, 2, 5, 5, 2, 2, 5, 5, 5, 5, 7, 7, 5, 5, 7, 7, 4, 5, 7, 7,
    5, 5, 7, 7, 7, 7, 8, 8, 7, 7, 8, 8, 5, 5, 7, 7, 5, 5, 7, 7, 7, 7, 8, 8, 7,
    7, 8, 8, 3, 4, 6, 7, 4, 5, 7, 7, 6, 7, 8, 8, 7, 7, 8, 8, 4, 5, 7, 7, 5, 5,
    7, 7, 7, 7, 8, 8, 7, 7, 8, 8, 6, 7, 8, 8, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8,
    8, 7, 7, 8, 8, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 4, 5, 7, 7, 5, 5, 7, 7,
    7, 7, 8, 8, 7, 7, 8, 8, 5, 5, 7, 7, 5, 5, 7, 7, 7, 7, 8, 8, 7, 7, 8, 8, 7,
    7, 8, 8, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 7, 7, 8, 8, 7, 7, 8, 8, 8, 8,
    8, 8, 8, 8, 8, 8,
];

#[cfg(test)]
mod tests {
    use core::hint::black_box;

    use super::*;

    #[test]
    fn device_tables_match_their_structured_sources_at_runtime() {
        let build_qe: fn() -> [u32; 47] = mq_qe_values;
        let build_transitions: fn() -> [u32; 47] = packed_mq_transitions;
        let build_sign_contexts: fn() -> [u16; 256] = packed_sign_contexts;

        let qe = black_box(build_qe)();
        let transitions = black_box(build_transitions)();
        let sign_contexts = black_box(build_sign_contexts)();

        for (index, state) in MQ_STATES.iter().copied().enumerate() {
            assert_eq!(qe[index], state.qe);
            assert_eq!(
                transitions[index],
                u32::from(state.nmps)
                    | (u32::from(state.nlps) << 8)
                    | (u32::from(state.switch) << 16)
            );
        }
        for (index, (context, xor)) in SIGN_CONTEXT_LOOKUP.iter().copied().enumerate() {
            assert_eq!(
                sign_contexts[index],
                u16::from(context) | (u16::from(xor) << 8)
            );
        }
    }
}