Enum DeflateFlush

Variants

NoFlush = 0

if flush is set to NoFlush, that allows deflate to decide how much data to accumulate before producing output, in order to maximize compression.

PartialFlush = 1

If flush is set to PartialFlush, all pending output is flushed to the output buffer, but the output is not aligned to a byte boundary. All of the input data so far will be available to the decompressor, as for Z_SYNC_FLUSH. This completes the current deflate block and follows it with an empty fixed codes block that is 10 bits long. This assures that enough bytes are output in order for the decompressor to finish the block before the empty fixed codes block.

SyncFlush = 2

If the parameter flush is set to SyncFlush, all pending output is flushed to the output buffer and the output is aligned on a byte boundary, so that the decompressor can get all input data available so far. (In particular avail_in is zero after the call if enough output space has been provided before the call.) Flushing may degrade compression for some compression algorithms and so it should be used only when necessary. This completes the current deflate block and follows it with an empty stored block that is three bits plus filler bits to the next byte, followed by four bytes (00 00 ff ff).

FullFlush = 3

If flush is set to FullFlush, all output is flushed as with Z_SYNC_FLUSH, and the compression state is reset so that decompression can restart from this point if previous compressed data has been damaged or if random access is desired. Using FullFlush too often can seriously degrade compression.

Finish = 4

If the parameter flush is set to Finish, pending input is processed, pending output is flushed and deflate returns with StreamEnd if there was enough output space. If deflate returns with Ok or BufError, this function must be called again with Finish and more output space (updated avail_out) but no more input data, until it returns with StreamEnd or an error. After deflate has returned StreamEnd, the only possible operations on the stream are deflateReset or deflateEnd.

Finish can be used in the first deflate call after deflateInit if all the compression is to be done in a single step. In order to complete in one call, avail_out must be at least the value returned by deflateBound (see below). Then deflate is guaranteed to return StreamEnd. If not enough output space is provided, deflate will not return StreamEnd, and it must be called again as described above.

Block = 5

If flush is set to Block, a deflate block is completed and emitted, as for SyncFlush, but the output is not aligned on a byte boundary, and up to seven bits of the current block are held to be written as the next byte after the next deflate block is completed. In this case, the decompressor may not be provided enough bits at this point in order to complete decompression of the data provided so far to the compressor. It may need to wait for the next block to be emitted. This is for advanced applications that need to control the emission of deflate blocks.