internal void _tr_flush_block(int buf, // input block, or NULL if too old
int stored_len, // length of input block
bool eof // true if this is the last block for a file
) {
int opt_lenb, static_lenb;// opt_len and static_len in bytes
int max_blindex = 0; // index of last bit length code of non zero freq
// Build the Huffman trees unless a stored block is forced
if(level > 0) {
// Check if the file is ascii or binary
if(data_type == Z_UNKNOWN) set_data_type();
// Construct the literal and distance trees
l_desc.build_tree(this);
d_desc.build_tree(this);
// At this point, opt_len and static_len are the total bit lengths of
// the compressed block data, excluding the tree representations.
// Build the bit length tree for the above two trees, and get the index
// in bl_order of the last bit length code to send.
max_blindex=build_bl_tree();
// Determine the best encoding. Compute first the block length in bytes
opt_lenb=(opt_len+3+7)>>3;
static_lenb=(static_len+3+7)>>3;
if(static_lenb<=opt_lenb) opt_lenb=static_lenb;
}
else {
opt_lenb=static_lenb=stored_len+5; // force a stored block
}
if(stored_len+4<=opt_lenb && buf != -1){
// 4: two words for the lengths
// The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
// Otherwise we can't have processed more than WSIZE input bytes since
// the last block flush, because compression would have been
// successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
// transform a block into a stored block.
_tr_stored_block(buf, stored_len, eof);
}
else if(static_lenb == opt_lenb){
send_bits((STATIC_TREES<<1)+(eof?1:0), 3);
compress_block(StaticTree.static_ltree, StaticTree.static_dtree);
}
else{
send_bits((DYN_TREES<<1)+(eof?1:0), 3);
send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1);
compress_block(dyn_ltree, dyn_dtree);
}
// The above check is made mod 2^32, for files larger than 512 MB
// and uLong implemented on 32 bits.
init_block();
if(eof){
bi_windup();
}
}
