diff options
Diffstat (limited to 'src/lib.rs')
| -rw-r--r-- | src/lib.rs | 29 |
1 files changed, 15 insertions, 14 deletions
@@ -511,17 +511,18 @@ const HUFFMAN_MAIN_TABLE_SIZE: usize = 1 << HUFFMAN_MAIN_TABLE_BITS; const HUFFMAN_SUBTABLE_SIZE: usize = 1 << (HUFFMAN_MAX_BITS - HUFFMAN_MAIN_TABLE_BITS); #[derive(Debug)] struct HuffmanTable { - main_table: [u16; HUFFMAN_MAIN_TABLE_SIZE], - subtables: [[u16; HUFFMAN_SUBTABLE_SIZE]; HUFFMAN_MAX_CODES], - subtables_used: u16, + main_table: [i16; HUFFMAN_MAIN_TABLE_SIZE], + subtables: [[u16; HUFFMAN_SUBTABLE_SIZE]; HUFFMAN_MAX_CODES + 1], + subtables_used: i16, } impl Default for HuffmanTable { fn default() -> Self { Self { main_table: [0; HUFFMAN_MAIN_TABLE_SIZE], - subtables: [[0; HUFFMAN_SUBTABLE_SIZE]; HUFFMAN_MAX_CODES], - subtables_used: 0, + subtables: [[0; HUFFMAN_SUBTABLE_SIZE]; HUFFMAN_MAX_CODES + 1], + // reserve "null" subtable + subtables_used: 1, } } } @@ -537,21 +538,22 @@ impl HuffmanTable { if length <= HUFFMAN_MAIN_TABLE_BITS { // just throw it in the main table for i in 0..1u16 << (HUFFMAN_MAIN_TABLE_BITS - length) { - self.main_table[usize::from(i << length | code)] = value | u16::from(length) << 9; + self.main_table[usize::from(i << length | code)] = + value as i16 | i16::from(length) << 9; } } else { // put it in a subtable. let main_table_entry = usize::from(code) & (HUFFMAN_MAIN_TABLE_SIZE - 1); let subtable_index = if self.main_table[main_table_entry] == 0 { let i = self.subtables_used; - self.main_table[main_table_entry] = 0x8000 | i; + self.main_table[main_table_entry] = -i; self.subtables_used += 1; i } else { - debug_assert_ne!(self.main_table[main_table_entry] & 0x8000, 0); - self.main_table[main_table_entry] & 0x7fff + debug_assert!(self.main_table[main_table_entry] < 0); + -self.main_table[main_table_entry] }; - let subtable = &mut self.subtables[usize::from(subtable_index)]; + let subtable = &mut self.subtables[subtable_index as usize]; for i in 0..1u16 << (HUFFMAN_MAX_BITS - length) { subtable[usize::from( i << (length - HUFFMAN_MAIN_TABLE_BITS) | code >> HUFFMAN_MAIN_TABLE_BITS, @@ -583,11 +585,10 @@ impl HuffmanTable { fn read_value<R: Read>(&self, reader: &mut BitReader<'_, R>) -> Result<u16, Error<R::Error>> { let code = reader.peek_bits(HUFFMAN_MAX_BITS)? as u16; let entry = self.main_table[usize::from(code) & (HUFFMAN_MAIN_TABLE_SIZE - 1)]; - let entry = if (entry & 0x8000) == 0 { - entry + let entry = if entry > 0 { + entry as u16 } else { - self.subtables[usize::from(entry & 0x7fff)] - [usize::from(code >> HUFFMAN_MAIN_TABLE_BITS)] + self.subtables[(-entry) as usize][usize::from(code >> HUFFMAN_MAIN_TABLE_BITS)] }; let length = (entry >> 9) as u8; if length == 0 { |