brotli/enc/

command.rs

use super::encode::BROTLI_NUM_DISTANCE_SHORT_CODES;
use super::util::Log2FloorNonZero;
#[derive(Copy, Clone, Debug)]
pub struct BrotliDistanceParams {
    pub distance_postfix_bits: u32,
    pub num_direct_distance_codes: u32,
    pub alphabet_size: u32,
    pub max_distance: usize,
}

#[derive(Clone, Copy, Debug, Default)]
pub struct Command {
    // stores copy_len in low 25 bits and copy_code - copy_len in high 7 bit
    pub insert_len_: u32,
    pub copy_len_: u32,
    //stores distance_extra bits
    pub dist_extra_: u32,
    pub cmd_prefix_: u16,
    // stores distance code in low 10 bits and num extra bits in high 6 bits
    pub dist_prefix_: u16,
}

impl Command {
    pub fn copy_len(&self) -> u32 {
        self.copy_len_ & 0x01ff_ffff
    }

    pub fn distance_context(&self) -> u32 {
        let r: u32 = (self.cmd_prefix_ as i32 >> 6) as u32;
        let c: u32 = (self.cmd_prefix_ as i32 & 7i32) as u32;
        if (r == 0 || r == 2 || r == 4 || r == 7) && c <= 2 {
            c
        } else {
            3
        }
    }

    pub fn init_insert(&mut self, insertlen: usize) {
        self.insert_len_ = insertlen as u32;
        self.copy_len_ = (4i32 << 25) as u32;
        self.dist_extra_ = 0u32;
        self.dist_prefix_ = (1u16 << 10) | BROTLI_NUM_DISTANCE_SHORT_CODES as u16;
        get_length_code(insertlen, 4usize, false, &mut self.cmd_prefix_);
    }
}

#[inline(always)]
pub fn ComputeDistanceCode(distance: usize, max_distance: usize, dist_cache: &[i32]) -> usize {
    if distance <= max_distance {
        let distance_plus_3: usize = distance.wrapping_add(3);
        let offset0: usize = distance_plus_3.wrapping_sub(dist_cache[0] as usize);
        let offset1: usize = distance_plus_3.wrapping_sub(dist_cache[1] as usize);
        if distance == dist_cache[0] as usize {
            return 0usize;
        } else if distance == dist_cache[1] as usize {
            return 1;
        } else if offset0 < 7usize {
            return (0x0975_0468_i32 >> (4usize).wrapping_mul(offset0) & 0xfi32) as usize;
        } else if offset1 < 7usize {
            return (0x0fdb_1ace_i32 >> (4usize).wrapping_mul(offset1) & 0xfi32) as usize;
        } else if distance == dist_cache[2] as usize {
            return 2usize;
        } else if distance == dist_cache[3] as usize {
            return 3usize;
        }
    }
    distance.wrapping_add(16).wrapping_sub(1)
}

#[inline(always)]
pub fn GetInsertLengthCode(insertlen: usize) -> u16 {
    if insertlen < 6usize {
        insertlen as u16
    } else if insertlen < 130usize {
        let nbits: u32 = Log2FloorNonZero(insertlen.wrapping_sub(2) as u64).wrapping_sub(1);
        ((nbits << 1) as usize)
            .wrapping_add(insertlen.wrapping_sub(2) >> nbits)
            .wrapping_add(2) as u16
    } else if insertlen < 2114usize {
        Log2FloorNonZero(insertlen.wrapping_sub(66) as u64).wrapping_add(10) as u16
    } else if insertlen < 6210usize {
        21u32 as u16
    } else if insertlen < 22594usize {
        22u32 as u16
    } else {
        23u32 as u16
    }
}

#[inline(always)]
pub fn GetCopyLengthCode(copylen: usize) -> u16 {
    if copylen < 10usize {
        copylen.wrapping_sub(2) as u16
    } else if copylen < 134usize {
        let nbits: u32 = Log2FloorNonZero(copylen.wrapping_sub(6) as u64).wrapping_sub(1);
        ((nbits << 1) as usize)
            .wrapping_add(copylen.wrapping_sub(6) >> nbits)
            .wrapping_add(4) as u16
    } else if copylen < 2118usize {
        Log2FloorNonZero(copylen.wrapping_sub(70) as u64).wrapping_add(12) as u16
    } else {
        23u32 as u16
    }
}


#[inline(always)]
pub(crate) fn combine_length_codes(inscode: u16, copycode: u16, use_last_distance: bool) -> u16 {
    let bits64: u16 = (copycode as u32 & 0x7u32 | (inscode as u32 & 0x7u32) << 3) as u16;
    if use_last_distance && inscode < 8 && copycode < 16 {
        if (copycode as i32) < 8i32 {
            bits64
        } else {
            let s64: u16 = 64u16;
            (bits64 as i32 | s64 as i32) as u16
        }
    } else {
        let sub_offset: i32 = 2i32 * ((copycode as i32 >> 3) + 3i32 * (inscode as i32 >> 3));
        let offset = (sub_offset << 5) + 0x40i32 + (0x520d40i32 >> sub_offset & 0xc0i32);
        (offset as u16 as i32 | bits64 as i32) as u16
    }
}


#[inline(always)]
pub(crate) fn get_length_code(
    insertlen: usize,
    copylen: usize,
    use_last_distance: bool,
    code: &mut u16,
) {
    let inscode: u16 = GetInsertLengthCode(insertlen);
    let copycode: u16 = GetCopyLengthCode(copylen);
    *code = combine_length_codes(inscode, copycode, use_last_distance);
}
pub fn PrefixEncodeCopyDistance(
    distance_code: usize,
    num_direct_codes: usize,
    postfix_bits: u64,
    code: &mut u16,
    extra_bits: &mut u32,
) {
    if distance_code < (BROTLI_NUM_DISTANCE_SHORT_CODES as usize).wrapping_add(num_direct_codes) {
        *code = distance_code as u16;
        *extra_bits = 0u32;
    } else {
        let dist: u64 = (1u64 << postfix_bits.wrapping_add(2u32 as (u64))).wrapping_add(
            (distance_code as u64)
                .wrapping_sub(BROTLI_NUM_DISTANCE_SHORT_CODES as u64)
                .wrapping_sub(num_direct_codes as u64),
        );
        let bucket: u64 = Log2FloorNonZero(dist).wrapping_sub(1) as (u64);
        let postfix_mask: u64 = (1u32 << postfix_bits).wrapping_sub(1) as (u64);
        let postfix: u64 = dist & postfix_mask;
        let prefix: u64 = (dist >> bucket) & 1;
        let offset: u64 = (2u64).wrapping_add(prefix) << bucket;
        let nbits: u64 = bucket.wrapping_sub(postfix_bits);
        *code = ((nbits << 10)
            | ((BROTLI_NUM_DISTANCE_SHORT_CODES as u64)
                .wrapping_add(num_direct_codes as u64)
                .wrapping_add(
                    2u64.wrapping_mul(nbits.wrapping_sub(1))
                        .wrapping_add(prefix)
                        << postfix_bits,
                )
                .wrapping_add(postfix))) as u16;
        *extra_bits = (dist.wrapping_sub(offset) >> postfix_bits) as u32;
        /*(16u64)
        .wrapping_add(num_direct_codes as u64)
        .wrapping_add((2u64).wrapping_mul(nbits.wrapping_sub(1)).wrapping_add(prefix) <<
                      postfix_bits)
        .wrapping_add(postfix) as u16;*/
        //*extra_bits = (nbits << 24 | dist.wrapping_sub(offset) >> postfix_bits) as u32;
    }
}

impl Command {
    pub fn restore_distance_code(&self, dist: &BrotliDistanceParams) -> u32 {
        if (self.dist_prefix_ as i32 & 0x3ff)
            < BROTLI_NUM_DISTANCE_SHORT_CODES as i32 + dist.num_direct_distance_codes as i32
        {
            self.dist_prefix_ as u32 & 0x3ff
        } else {
            let dcode = self.dist_prefix_ as u32 & 0x3ff;
            let nbits: u32 = u32::from(self.dist_prefix_ >> 10);
            let extra: u32 = self.dist_extra_;
            let postfix_mask = (1u32 << dist.distance_postfix_bits) - 1;
            let hcode = dcode
                .wrapping_sub(dist.num_direct_distance_codes)
                .wrapping_sub(BROTLI_NUM_DISTANCE_SHORT_CODES)
                >> dist.distance_postfix_bits;
            let lcode = dcode
                .wrapping_sub(dist.num_direct_distance_codes)
                .wrapping_sub(BROTLI_NUM_DISTANCE_SHORT_CODES)
                & postfix_mask;
            let offset = (2u32.wrapping_add((hcode & 1)) << nbits).wrapping_sub(4);
            (offset.wrapping_add(extra) << dist.distance_postfix_bits)
                .wrapping_add(lcode)
                .wrapping_add(dist.num_direct_distance_codes)
                .wrapping_add(BROTLI_NUM_DISTANCE_SHORT_CODES)
        }
    }

    // returns which distance code to use ( 0 means none, 1 means last, 2 means penultimate, 3 means the prior to penultimate
    pub fn distance_index_and_offset(&self, dist: &BrotliDistanceParams) -> (usize, isize) {
        let n_postfix = dist.distance_postfix_bits;
        let n_direct = dist.num_direct_distance_codes;
        let dextra = self.dist_extra_;
        let dprefix = self.dist_prefix_ & 0x3ff;
        let n_dist_bits = self.dist_prefix_ >> 10;
        if u32::from(dprefix) < BROTLI_NUM_DISTANCE_SHORT_CODES {
            let table: [(usize, isize); 16] = [
                (1, 0),
                (2, 0),
                (3, 0),
                (4, 0),
                (1, -1),
                (1, 1),
                (1, -2),
                (1, 2),
                (1, -3),
                (1, 3),
                (2, -1),
                (2, 1),
                (2, -2),
                (2, 2),
                (2, -3),
                (2, 3),
            ];
            //eprint!("AA {:?} {:?} -> {:?}\n",*self, *dist, table[dprefix as usize]);
            return table[dprefix as usize];
        }
        if (dprefix as usize) < BROTLI_NUM_DISTANCE_SHORT_CODES as usize + n_direct as usize {
            let ret = dprefix as isize + 1 - BROTLI_NUM_DISTANCE_SHORT_CODES as isize;
            //eprint!("BB {:?} {:?} -> {:?}\n",*self, *dist, ret);
            return (0, ret);
        }
        let postfix_mask = (1 << n_postfix) - 1;
        let dcode = dprefix as u32 - BROTLI_NUM_DISTANCE_SHORT_CODES - n_direct;
        let hcode = dcode >> n_postfix;
        let lcode = dcode & postfix_mask;
        let offset = ((2 + (hcode & 1)) << n_dist_bits) - 4;

        let ret = (((offset + dextra) << n_postfix) + lcode + n_direct + 1) as isize;
        //assert!(ret != 0);
        (0, ret)
    }
}

pub fn RecomputeDistancePrefixes(
    cmds: &mut [Command],
    num_commands: usize,
    num_direct_distance_codes: u32,
    distance_postfix_bits: u32,
    dist: &BrotliDistanceParams,
) {
    if num_direct_distance_codes == 0u32 && (distance_postfix_bits == 0u32) {
        return;
    }
    for i in 0usize..num_commands {
        let cmd: &mut Command = &mut cmds[i];
        if cmd.copy_len() != 0 && cmd.cmd_prefix_ >= 128 {
            PrefixEncodeCopyDistance(
                cmd.restore_distance_code(dist) as usize,
                num_direct_distance_codes as usize,
                distance_postfix_bits as (u64),
                &mut cmd.dist_prefix_,
                &mut cmd.dist_extra_,
            );
        }
    }
}

impl Command {
    pub fn init(
        &mut self,
        dist: &BrotliDistanceParams,
        insertlen: usize,
        copylen: usize,
        copylen_code: usize,
        distance_code: usize,
    ) {
        self.insert_len_ = insertlen as u32;
        let copylen_code_delta = (copylen_code as i32 - copylen as i32) as i8;
        self.copy_len_ = (copylen as u32 | (u32::from(copylen_code_delta as u8) << 25));
        PrefixEncodeCopyDistance(
            distance_code,
            dist.num_direct_distance_codes as usize,
            u64::from(dist.distance_postfix_bits),
            &mut self.dist_prefix_,
            &mut self.dist_extra_,
        );
        get_length_code(
            insertlen,
            copylen_code,
            (self.dist_prefix_ & 0x3ff) == 0,
            &mut self.cmd_prefix_,
        );
    }

    pub fn new(
        dist: &BrotliDistanceParams,
        insertlen: usize,
        copylen: usize,
        copylen_code: usize,
        distance_code: usize,
    ) -> Self {
        let mut cmd = Command {
            insert_len_: insertlen as u32,
            copy_len_: (copylen | ((copylen_code ^ copylen) << 25)) as u32,
            dist_extra_: 0,
            cmd_prefix_: 0,
            dist_prefix_: 0,
        };
        cmd.init(dist, insertlen, copylen, copylen_code, distance_code);
        cmd
    }
}

#[cfg(test)]
mod test {
    // returns which distance code to use ( 0 means none, 1 means last, 2 means penultimate, 3 means the prior to penultimate
    pub fn helperCommandDistanceIndexAndOffset(
        cmd: &super::Command,
        dist: &super::BrotliDistanceParams,
    ) -> (usize, isize) {
        let n_postfix = dist.distance_postfix_bits;
        let n_direct = dist.num_direct_distance_codes;
        let dextra = cmd.dist_extra_;
        let dist_prefix = cmd.dist_prefix_ & 0x3ff;
        if dist_prefix < 16 {
            let table: [(usize, isize); 16] = [
                (1, 0),
                (2, 0),
                (3, 0),
                (4, 0),
                (1, -1),
                (1, 1),
                (1, -2),
                (1, 2),
                (1, -3),
                (1, 3),
                (2, -1),
                (2, 1),
                (2, -2),
                (2, 2),
                (2, -3),
                (2, 3),
            ];
            return table[cmd.dist_prefix_ as usize];
        }
        if (dist_prefix as usize) < 16 + n_direct as usize {
            return (0, dist_prefix as isize + 1 - 16);
        }
        let postfix_mask = (1 << n_postfix) - 1;
        let dcode = dist_prefix as u32 - 16 - n_direct;
        let n_dist_bits = 1 + (dcode >> (n_postfix + 1));

        let hcode = dcode >> n_postfix;
        let lcode = dcode & postfix_mask;
        let offset = ((2 + (hcode & 1)) << n_dist_bits) - 4;
        (
            0,
            (((offset + dextra) << n_postfix) + lcode + n_direct + 1) as isize,
        )
    }
    #[test]
    fn test_command_return_distance_index_offset() {
        let param = super::BrotliDistanceParams {
            distance_postfix_bits: 2,
            num_direct_distance_codes: 16,
            alphabet_size: 224,
            max_distance: 268435456,
        };
        let mut cmd = super::Command::default();
        cmd.insert_len_ = 63;
        cmd.copy_len_ = 3;
        cmd.dist_extra_ = 3;
        cmd.cmd_prefix_ = 297;
        cmd.dist_prefix_ = 2089;

        assert_eq!(cmd.distance_index_and_offset(&param), (0, 46));
        assert_eq!(
            cmd.distance_index_and_offset(&param),
            helperCommandDistanceIndexAndOffset(&cmd, &param)
        );
        cmd = super::Command {
            insert_len_: 27,
            copy_len_: 3,
            dist_extra_: 0,
            cmd_prefix_: 281,
            dist_prefix_: 6,
        };
        assert_eq!(cmd.distance_index_and_offset(&param), (1, -2));
        assert_eq!(
            cmd.distance_index_and_offset(&param),
            helperCommandDistanceIndexAndOffset(&cmd, &param)
        );
        cmd = super::Command {
            insert_len_: 1,
            copy_len_: 3,
            dist_extra_: 0,
            cmd_prefix_: 137,
            dist_prefix_: 27,
        };
        assert_eq!(cmd.distance_index_and_offset(&param), (0, 12));
        assert_eq!(
            cmd.distance_index_and_offset(&param),
            helperCommandDistanceIndexAndOffset(&cmd, &param)
        );
        cmd = super::Command {
            insert_len_: 5,
            copy_len_: 4,
            dist_extra_: 297,
            cmd_prefix_: 170,
            dist_prefix_: 11377,
        };
        assert_eq!(cmd.distance_index_and_offset(&param), (0, 17574));
        assert_eq!(
            cmd.distance_index_and_offset(&param),
            helperCommandDistanceIndexAndOffset(&cmd, &param)
        );
        cmd.init_insert(24);
        assert_eq!(cmd.distance_index_and_offset(&param), (0, 1));
    }
    /*
    #[test]
    fn test_restore_distance_code() {
        for dist_code in 0..50000 {
            let mut cmd = super::Command::default();
            let param =super::BrotliDistanceParams{
                distance_postfix_bits:2,
                num_direct_distance_codes:16,
                alphabet_size:224,
                max_distance:268435456,
            };
            super::InitCommand(&mut cmd, &param, 4, 4, 4, dist_code);
            let exp_dist_code = super::CommandRestoreDistanceCode(&cmd, &param);
            assert_eq!(exp_dist_code as u32, dist_code as u32);
        }
    }*/
}