alac-encoder 0.3.0

//! Adaptive Golomb

use core::cmp;

use crate::bit_buffer::BitBuffer;

const QBSHIFT: u32 = 9;
const QB: u32 = 1 << QBSHIFT;

const MMULSHIFT: u32 = 2;
const MDENSHIFT: u32 = QBSHIFT - MMULSHIFT - 1;
const MOFF: u32 = 1 << (MDENSHIFT-2);

const BITOFF: u32 = 24;

// Max. prefix of 1's.
const MAX_PREFIX_16: u32 = 9;
const MAX_PREFIX_32: u32 = 9;

// Max. bits in 16-bit data type
const MAX_DATATYPE_BITS_16: u32 = 16;

const N_MAX_MEAN_CLAMP:u32 = 0xffff;
const N_MEAN_CLAMP_VAL:u32 = 0xffff;

pub const PB0: u32 = 40;
pub const MB0: u32 = 10;
pub const KB0: u32 = 14;

pub struct AgParams {
    mb: u32,
    pb: u32,
    kb: u32,
    wb: u32,
    /// Full width
    fw: u32,
    /// Sector width
    sw: u32,
}

impl AgParams {
    pub fn new(m: u32, p: u32, k: u32, f: u32, s: u32) -> AgParams {
        AgParams {
            mb: m,
            pb: p,
            kb: k,
            wb: (1 << k) - 1,
            fw: f,
            sw: s,
        }
    }

    pub fn new_standard(fullwidth: u32, sectorwidth: u32) -> AgParams {
        AgParams::new(MB0, PB0, KB0, fullwidth, sectorwidth)
    }
}

#[inline(always)]
fn dyn_code(bitstream: &mut BitBuffer, m: u32, k: u32, n: u32) {
    let division = n / m;

    if division < MAX_PREFIX_16 {
        let modulo = n % m;
        let de = (modulo == 0) as u32;
        let num_bits = division + k + 1 - de;
        let value = (((1 << division) - 1) << (num_bits - division)) + modulo + 1 - de;

        // use this result if coding this way is smaller than doing escape
        if num_bits <= (MAX_PREFIX_16 + MAX_DATATYPE_BITS_16) {
            bitstream.write_lte25(value, num_bits as usize);
            return;
        }
    }

    let num_bits = MAX_PREFIX_16 + MAX_DATATYPE_BITS_16;
    let value = (((1 << MAX_PREFIX_16) - 1) << MAX_DATATYPE_BITS_16) + n;

    bitstream.write_lte25(value, num_bits as usize);
}

#[inline(always)]
fn dyn_code_32bit(bitstream: &mut BitBuffer, maxbits: usize, m: u32, k: u32, n: u32) {
    let division = n / m;

    if division < MAX_PREFIX_32 {
        let modulo: u32 = n - (m * division);
        let de = (modulo == 0) as u32;

        let num_bits = division + k + 1 - de;
        let value = (((1<<division)-1)<<(num_bits-division)) + modulo + 1 - de;

        if num_bits <= 25 {
            bitstream.write_lte25(value, num_bits as usize);
            return;
        }
    }

    bitstream.write_lte25((1 << MAX_PREFIX_32) - 1, MAX_PREFIX_32 as usize);
    bitstream.write(n, maxbits);
}

pub fn dyn_comp(params: &AgParams, pc: &[i32], bitstream: &mut BitBuffer, num_samples: usize, bit_size: usize) {
    debug_assert!(bit_size > 0 && bit_size <= 32);

    let mut mb: u32 = params.mb;
    let pb: u32 = params.pb;
    let kb: u32 = params.kb;
    let wb: u32 = params.wb;
    let mut zmode: u32 = 0;

    let mut row_pos = 0usize;
    let row_size = params.sw as usize;
    let row_jump = params.fw as usize - row_size;
    let mut in_ptr = 0usize;

    let mut c = 0usize;
    while c < num_samples {
        let k = cmp::min(31 - ((mb >> QBSHIFT) + 3).leading_zeros(), kb);
        let m = (1 << k) - 1;

        let del = pc[in_ptr];
        in_ptr += 1;
        row_pos += 1;

        let n: u32 = ((del.abs() << 1) - ((del >> 31) & 1)) as u32 - zmode;
        debug_assert!(32 - n.leading_zeros() <= bit_size as u32);

        dyn_code_32bit(bitstream, bit_size, m, k, n);

        c += 1;
        if row_pos >= row_size {
            row_pos = 0;
            in_ptr += row_jump;
        }

        mb = pb * (n + zmode) + mb - ((pb * mb) >> QBSHIFT);

        // update mean tracking if it's overflowed
        if n > N_MAX_MEAN_CLAMP {
            mb = N_MEAN_CLAMP_VAL;
        }

        zmode = 0;

        debug_assert!(c <= num_samples);

        if ((mb << MMULSHIFT) < QB) && (c < num_samples) {
            zmode = 1;
            let mut nz = 0u32;

            while (c < num_samples) && (pc[in_ptr] == 0) {
                // Take care of wrap-around globals.
                in_ptr += 1;
                nz += 1;
                c += 1;
                row_pos += 1;

                if row_pos >= row_size {
                    row_pos = 0;
                    in_ptr += row_jump;
                }

                if nz >= 65535 {
                    zmode = 0;
                    break;
                }
            }

            let k = mb.leading_zeros() - BITOFF + ((mb + MOFF) >> MDENSHIFT);
            let mz = ((1 << k) - 1) & wb;

            dyn_code(bitstream, mz, k, nz);

            mb = 0;
        }
    }
}