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Diffstat (limited to 'vendor/image/src/codecs/jpeg/entropy.rs')
-rw-r--r-- | vendor/image/src/codecs/jpeg/entropy.rs | 63 |
1 files changed, 0 insertions, 63 deletions
diff --git a/vendor/image/src/codecs/jpeg/entropy.rs b/vendor/image/src/codecs/jpeg/entropy.rs deleted file mode 100644 index 5bdcef6..0000000 --- a/vendor/image/src/codecs/jpeg/entropy.rs +++ /dev/null @@ -1,63 +0,0 @@ -/// Given an array containing the number of codes of each code length, -/// this function generates the huffman codes lengths and their respective -/// code lengths as specified by the JPEG spec. -const fn derive_codes_and_sizes(bits: &[u8; 16]) -> ([u8; 256], [u16; 256]) { - let mut huffsize = [0u8; 256]; - let mut huffcode = [0u16; 256]; - - let mut k = 0; - - // Annex C.2 - // Figure C.1 - // Generate table of individual code lengths - let mut i = 0; - while i < 16 { - let mut j = 0; - while j < bits[i as usize] { - huffsize[k] = i + 1; - k += 1; - j += 1; - } - i += 1; - } - - huffsize[k] = 0; - - // Annex C.2 - // Figure C.2 - // Generate table of huffman codes - k = 0; - let mut code = 0u16; - let mut size = huffsize[0]; - - while huffsize[k] != 0 { - huffcode[k] = code; - code += 1; - k += 1; - - if huffsize[k] == size { - continue; - } - - // FIXME there is something wrong with this code - let diff = huffsize[k].wrapping_sub(size); - code = if diff < 16 { code << diff as usize } else { 0 }; - - size = size.wrapping_add(diff); - } - - (huffsize, huffcode) -} - -pub(crate) const fn build_huff_lut_const(bits: &[u8; 16], huffval: &[u8]) -> [(u8, u16); 256] { - let mut lut = [(17u8, 0u16); 256]; - let (huffsize, huffcode) = derive_codes_and_sizes(bits); - - let mut i = 0; - while i < huffval.len() { - lut[huffval[i] as usize] = (huffsize[i], huffcode[i]); - i += 1; - } - - lut -} |