lib/zlib: implement switching between DFLTCC and software

This commit is based on:
  zlib-ng/zlib-ng@fc04275

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mikhail Zaslonko <[email protected]>
Acked-by: Ilya Leoshkevich <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

lib/zlib_dfltcc/dfltcc_deflate.c

@@ -112,30 +112,36 @@ int dfltcc_deflate(
  int soft_bcc;
  int no_flush;
 
- if (!dfltcc_can_deflate(strm))
+ if (!dfltcc_can_deflate(strm)) {
+ /* Clear history. */
+ if (flush == Z_FULL_FLUSH)
+ param->hl = 0;
  return 0;
+ }
 
 again:
  masked_avail_in = 0;
  soft_bcc = 0;
  no_flush = flush == Z_NO_FLUSH;
 
- /* Trailing empty block. Switch to software, except when Continuation Flag
- * is set, which means that DFLTCC has buffered some output in the
- * parameter block and needs to be called again in order to flush it.
+ /* No input data. Return, except when Continuation Flag is set, which means
+ * that DFLTCC has buffered some output in the parameter block and needs to
+ * be called again in order to flush it.
  */
- if (flush == Z_FINISH && strm->avail_in == 0 && !param->cf) {
- if (param->bcf) {
-  /* A block is still open, and the hardware does not support closing
-  * blocks without adding data. Thus, close it manually.
-  */
+ if (strm->avail_in == 0 && !param->cf) {
+ /* A block is still open, and the hardware does not support closing
+ * blocks without adding data. Thus, close it manually.
+ */
+ if (!no_flush && param->bcf) {
  send_eobs(strm, param);
  param->bcf = 0;
  }
- return 0;
- }
-
- if (strm->avail_in == 0 && !param->cf) {
+ /* Let one of deflate_* functions write a trailing empty block. */
+ if (flush == Z_FINISH)
+ return 0;
+ /* Clear history. */
+ if (flush == Z_FULL_FLUSH)
+ param->hl = 0;
  *result = need_more;
  return 1;
  }
@@ -189,7 +195,7 @@ int dfltcc_deflate(
  param->cvt = CVT_ADLER32;
  if (!no_flush)
  /* We need to close a block. Always do this in software - when there is
- * no input data, the hardware will not nohor BCC. */
+ * no input data, the hardware will not hohor BCC. */
  soft_bcc = 1;
  if (flush == Z_FINISH && !param->bcf)
  /* We are about to open a BFINAL block, set Block Header Final bit
@@ -204,8 +210,8 @@ int dfltcc_deflate(
  param->sbb = (unsigned int)state->bi_valid;
  if (param->sbb > 0)
  *strm->next_out = (Byte)state->bi_buf;
- if (param->hl)
-  param->nt = 0; /* Honor history */
+ /* Honor history and check value */
+ param->nt = 0;
  param->cv = strm->adler;
 
  /* When opening a block, choose a Huffman-Table Type */