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authordkf <donal.k.fellows@manchester.ac.uk>2016-06-27 14:27:43 (GMT)
committerdkf <donal.k.fellows@manchester.ac.uk>2016-06-27 14:27:43 (GMT)
commit2453f30fb9e0fd71b6fc37ef6df3385f2efaf6d5 (patch)
tree1604a59684785a9535ed443d3a1ed7b979ed4f99 /doc/zlib.n
parent2d4bd7bd8e4bc730323dccbc6b659954f3d1341c (diff)
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[dd260aaf72] Allow the -dictionary option to be read from a pushed transform.
Diffstat (limited to 'doc/zlib.n')
-rw-r--r--doc/zlib.n18
1 files changed, 12 insertions, 6 deletions
diff --git a/doc/zlib.n b/doc/zlib.n
index 9f3078d..fd29e0d 100644
--- a/doc/zlib.n
+++ b/doc/zlib.n
@@ -174,7 +174,11 @@ to the \fBzlib push\fR command:
.VS "TIP 400"
Sets the compression dictionary to use when working with compressing or
decompressing the data to be \fIbinData\fR. Not valid for transformations that
-work with gzip-format data.
+work with gzip-format data. The dictionary should consist of strings (byte
+sequences) that are likely to be encountered later in the data to be compressed,
+with the most commonly used strings preferably put towards the end of the
+dictionary. Tcl provides no mechanism for choosing a good such dictionary for
+a particular data sequence.
.VE
.TP
\fB\-header\fI dictionary\fR
@@ -207,11 +211,13 @@ compression algorithm depends on what format is being produced or consumed.
.TP
\fB\-dictionary\fI binData\fR
.VS "TIP 400"
-This read-write options gets or sets the compression dictionary to use when
-working with compressing or decompressing the data to be \fIbinData\fR. It is
-not valid for transformations that work with gzip-format data, and should not
-normally be set on compressing transformations other than at the point where
-the transformation is stacked.
+This read-write options gets or sets the initial compression dictionary to use
+when working with compressing or decompressing the data to be \fIbinData\fR.
+It is not valid for transformations that work with gzip-format data, and should
+not normally be set on compressing transformations other than at the point where
+the transformation is stacked. Note that this cannot be used to get the
+current active compression dictionary mid-stream, as that information is not
+exposed by the underlying library.
.VE
.TP
\fB\-flush\fI type\fR