in source/huffman.c [12:20]
void aws_huffman_encoder_init(struct aws_huffman_encoder *encoder, struct aws_huffman_symbol_coder *coder) {
AWS_ASSERT(encoder);
AWS_ASSERT(coder);
AWS_ZERO_STRUCT(*encoder);
encoder->coder = coder;
encoder->eos_padding = UINT8_MAX;
}