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//! Generate correct ML_PREDEFINED_TABLE from zstd reference
fn main() {
// Reference ML_defaultDTable from zstd source
// Format: (nextState, nbAddBits, nbBits, baseVal)
let ref_table: [(u16, u8, u8, u32); 64] = [
(0, 0, 6, 3),
(0, 0, 4, 4), // states 0,1
(32, 0, 5, 5),
(0, 0, 5, 6), // states 2,3
(0, 0, 5, 8),
(0, 0, 5, 9), // states 4,5
(0, 0, 5, 11),
(0, 0, 6, 13), // states 6,7
(0, 0, 6, 16),
(0, 0, 6, 19), // states 8,9
(0, 0, 6, 22),
(0, 0, 6, 25), // states 10,11
(0, 0, 6, 28),
(0, 0, 6, 31), // states 12,13
(0, 0, 6, 34),
(0, 1, 6, 37), // states 14,15
(0, 1, 6, 41),
(0, 2, 6, 47), // states 16,17
(0, 3, 6, 59),
(0, 4, 6, 83), // states 18,19
(0, 7, 6, 131),
(0, 9, 6, 515), // states 20,21
(16, 0, 4, 4),
(0, 0, 4, 5), // states 22,23
(32, 0, 5, 6),
(0, 0, 5, 7), // states 24,25
(32, 0, 5, 9),
(0, 0, 5, 10), // states 26,27
(0, 0, 6, 12),
(0, 0, 6, 15), // states 28,29
(0, 0, 6, 18),
(0, 0, 6, 21), // states 30,31
(0, 0, 6, 24),
(0, 0, 6, 27), // states 32,33
(0, 0, 6, 30),
(0, 0, 6, 33), // states 34,35
(0, 1, 6, 35),
(0, 1, 6, 39), // states 36,37
(0, 2, 6, 43),
(0, 3, 6, 51), // states 38,39
(0, 4, 6, 67),
(0, 5, 6, 99), // states 40,41
(0, 8, 6, 259),
(32, 0, 4, 4), // states 42,43
(48, 0, 4, 4),
(16, 0, 4, 5), // states 44,45
(32, 0, 5, 7),
(32, 0, 5, 8), // states 46,47
(32, 0, 5, 10),
(32, 0, 5, 11), // states 48,49
(0, 0, 6, 14),
(0, 0, 6, 17), // states 50,51
(0, 0, 6, 20),
(0, 0, 6, 23), // states 52,53
(0, 0, 6, 26),
(0, 0, 6, 29), // states 54,55
(0, 0, 6, 32),
(0, 16, 6, 65539), // states 56,57
(0, 15, 6, 32771),
(0, 14, 6, 16387), // states 58,59
(0, 13, 6, 8195),
(0, 12, 6, 4099), // states 60,61
(0, 11, 6, 2051),
(0, 10, 6, 1027), // states 62,63
];
// ML_BASELINE_TABLE format: (extra_bits, baseline)
let ml_baseline: [(u8, u32); 53] = [
// Codes 0-31: No extra bits, match_length = baseline (3-34)
(0, 3),
(0, 4),
(0, 5),
(0, 6),
(0, 7),
(0, 8),
(0, 9),
(0, 10),
(0, 11),
(0, 12),
(0, 13),
(0, 14),
(0, 15),
(0, 16),
(0, 17),
(0, 18),
(0, 19),
(0, 20),
(0, 21),
(0, 22),
(0, 23),
(0, 24),
(0, 25),
(0, 26),
(0, 27),
(0, 28),
(0, 29),
(0, 30),
(0, 31),
(0, 32),
(0, 33),
(0, 34),
// Codes 32-35: 1 extra bit each
(1, 35),
(1, 37),
(1, 39),
(1, 41),
// Codes 36-37: 2 extra bits each
(2, 43),
(2, 47),
// Codes 38-39: 3 extra bits each
(3, 51),
(3, 59),
// Codes 40-41: 4 extra bits each
(4, 67),
(4, 83),
// Code 42: 5 extra bits
(5, 99),
// Code 43: 7 extra bits
(7, 131),
// Code 44: 8 extra bits
(8, 259),
// Code 45: 9 extra bits
(9, 515),
// Code 46-52
(10, 1027),
(11, 2051),
(12, 4099),
(13, 8195),
(14, 16387),
(15, 32771),
(16, 65539),
];
println!("/// Hardcoded Match Length decode table from zstd's seqSymbolTable_ML_defaultDistribution.");
println!("/// Each entry is (symbol, nbBits, baseline) for FSE state transitions.");
println!("/// These values are taken directly from zstd's reference implementation.");
println!("const ML_PREDEFINED_TABLE: [(u8, u8, u16); 64] = [");
for chunk in (0..64).collect::<Vec<_>>().chunks(4) {
let entries: Vec<String> = chunk
.iter()
.map(|&state| {
let (next_state, nb_add_bits, nb_bits, base_val) = ref_table[state];
// Find ML code that matches (nb_add_bits, base_val)
let ml_code = ml_baseline
.iter()
.position(|&(extra_bits, baseline)| {
extra_bits == nb_add_bits && baseline == base_val
})
.unwrap_or_else(|| {
panic!(
"No ML code found for state {} (nbAddBits={}, baseVal={})",
state, nb_add_bits, base_val
)
}) as u8;
// Calculate baseline (nextState from zstd)
let baseline = next_state;
format!("({:>2}, {}, {:>2})", ml_code, nb_bits, baseline)
})
.collect();
let comment = format!("// states {}-{}", chunk[0], chunk[chunk.len() - 1]);
println!(" {}, {}", entries.join(", "), comment);
}
println!("];");
// Also verify state 42 specifically
println!("\n=== Verification ===");
let (next_state, nb_add_bits, nb_bits, base_val) = ref_table[42];
println!(
"State 42: nextState={}, nbAddBits={}, nbBits={}, baseVal={}",
next_state, nb_add_bits, nb_bits, base_val
);
let ml_code = ml_baseline
.iter()
.position(|&(extra_bits, baseline)| extra_bits == nb_add_bits && baseline == base_val)
.map(|c| c as u8);
println!(
"ML code for (nbAddBits={}, baseVal={}): {:?}",
nb_add_bits, base_val, ml_code
);
}