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Assure that deflateParams() will not switch functions mid-block.

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This alters the specification in zlib.h, so that deflateParams()
will not change any parameters if there is not enough output space
in the event that a block is emitted in order to allow switching
the compression function.
This commit is contained in:
Mark Adler
2016-11-22 23:29:19 -08:00
parent 1101ea79c6
commit 7161ad76e2
2 changed files with 23 additions and 21 deletions
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11
deflate.c
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@@ -517,7 +517,6 @@ int ZEXPORT deflateParams(strm, level, strategy)
{ {
deflate_state *s; deflate_state *s;
compress_func func; compress_func func;
int err = Z_OK;
if (deflateStateCheck(strm)) return Z_STREAM_ERROR; if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
s = strm->state; s = strm->state;
@@ -534,9 +533,11 @@ int ZEXPORT deflateParams(strm, level, strategy)
if ((strategy != s->strategy || func != configuration_table[level].func)) { if ((strategy != s->strategy || func != configuration_table[level].func)) {
/* Flush the last buffer: */ /* Flush the last buffer: */
err = deflate(strm, Z_BLOCK); int err = deflate(strm, Z_BLOCK);
if (err == Z_BUF_ERROR && s->pending == 0) if (err == Z_STREAM_ERROR)
err = Z_OK; return err;
if (strm->avail_out == 0)
return Z_BUF_ERROR;
} }
if (s->level != level) { if (s->level != level) {
s->level = level; s->level = level;
@@ -546,7 +547,7 @@ int ZEXPORT deflateParams(strm, level, strategy)
s->max_chain_length = configuration_table[level].max_chain; s->max_chain_length = configuration_table[level].max_chain;
} }
s->strategy = strategy; s->strategy = strategy;
return err; return Z_OK;
} }
/* ========================================================================= */ /* ========================================================================= */

33
zlib.h
View File

@@ -695,24 +695,25 @@ ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm,
new level and strategy will take effect at the next call of deflate(). 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 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 have enough output space to complete, then the parameter change will not
take effect at an undetermined location in the uncompressed data provided so take effect. In this case, deflateParams() can be called again with the
far. In order to assure a change in the parameters at a specific location same parameters and more output space to try again.
in the uncompressed data, the deflate stream should first be flushed with
Z_BLOCK or another flush parameter, and deflate() called until
strm.avail_out is not zero, before the call of deflateParams(). Then no
more input data should be provided before the deflateParams() call. If this
is done, the old level and strategy will be applied to the data compressed
before deflateParams(), and the new level and strategy will be applied to
the the data compressed after deflateParams().
deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source stream In order to assure a change in the parameters on the first try, the
deflate stream should be flushed using deflate() with Z_BLOCK or other flush
request until strm.avail_out is not zero, before calling deflateParams().
Then no more input data should be provided before the deflateParams() call.
If this is done, the old level and strategy will be applied to the data
compressed before deflateParams(), and the new level and strategy will be
applied to the the data compressed after deflateParams().
deflateParams returns Z_OK on success, Z_STREAM_ERROR if the source stream
state was inconsistent or if a parameter was invalid, or Z_BUF_ERROR if state was inconsistent or if a parameter was invalid, or Z_BUF_ERROR if
there was not enough output space to complete the compression before the there was not enough output space to complete the compression of the
parameters were changed. Note that in the case of a Z_BUF_ERROR, the available input data before a change in the strategy or approach. Note that
parameters are changed nevertheless, and will take effect at an undetermined in the case of a Z_BUF_ERROR, the parameters are not changed. A return
location in the previously supplied uncompressed data. Compression may value of Z_BUF_ERROR is not fatal, in which case deflateParams() can be
proceed after a Z_BUF_ERROR. retried with more output space.
*/ */
ZEXTERN int ZEXPORT deflateTune OF((z_streamp strm, ZEXTERN int ZEXPORT deflateTune OF((z_streamp strm,