Permit immediate deflateParams changes before any deflate input.
This permits deflateParams to change the strategy and level right
after deflateInit, without having to wait until a header has been
written. The parameters can be changed immediately up until the
first deflate call that consumes any input data.
diff --git a/deflate.c b/deflate.c
index 8a1a91e..f146001 100644
--- a/deflate.c
+++ b/deflate.c
@@ -586,7 +586,8 @@
}
func = configuration_table[s->level].func;
- if ((strategy != s->strategy || func != configuration_table[level].func)) {
+ if ((strategy != s->strategy || func != configuration_table[level].func) &&
+ s->high_water) {
/* Flush the last buffer: */
int err = deflate(strm, Z_BLOCK);
if (err == Z_STREAM_ERROR)
diff --git a/zlib.h b/zlib.h
index feabc54..a4b3baf 100644
--- a/zlib.h
+++ b/zlib.h
@@ -712,10 +712,11 @@
used to switch between compression and straight copy of the input data, or
to switch to a different kind of input data requiring a different strategy.
If the compression approach (which is a function of the level) or the
- strategy is changed, then the input available so far is compressed with the
- old level and strategy using deflate(strm, Z_BLOCK). There are three
- approaches for the compression levels 0, 1..3, and 4..9 respectively. The
- new level and strategy will take effect at the next call of deflate().
+ strategy is changed, and if any input has been consumed in a previous
+ deflate() call, then the input available so far is compressed with the old
+ level and strategy using deflate(strm, Z_BLOCK). There are three approaches
+ for the compression levels 0, 1..3, and 4..9 respectively. The new level
+ and strategy will take effect at the next call of deflate().
If a deflate(strm, Z_BLOCK) is performed by deflateParams(), and it does
not have enough output space to complete, then the parameter change will not
