fast 0..255 * 0..255 => 0..255 rounded multiplication

take a -128..127 value and stbi__clamp it and convert to 0..255

returns 1 if "a*b*c + add" has no negative terms/factors and doesn't overflow

initialize a callback-based context

initialize a memory-decode context

if there's a pending marker from the entropy stream, return that otherwise, fetch from the stream and get a marker. if there's no marker, return 0xff,

returns 1 if the product is valid, 0 on overflow. negative factors are considered invalid.

clean up the temporary component buffers

decode a jpeg huffman value from the bitstream

after a restart interval, stbi__jpeg_reset the entropy decoder and the dc prediction

TODO(syoyo): refactor function.

Make index zero-base, and also support relative index.

combined JPEG 'receive' and JPEG 'extend', since baseline always extends everything it receives.

returns 0..31 for the highest set bit

mallocs with size overflow checking

extract an arbitrarily-aligned N-bit value (N=bits) from v, and then make it 8-bits long and fractionally extend it to full full range.

returns STBI_rgb or whatever, 0 on error

Parse triples with index offsets: i, i/j/k, i//k, i/j

return 1 if the sum is valid, 0 on overflow. negative terms are considered invalid.