diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/zlib.n | 135 |
1 files changed, 102 insertions, 33 deletions
@@ -1,5 +1,5 @@ '\" -'\" Copyright (c) 2008 Donal K. Fellows +'\" Copyright (c) 2008-2012 Donal K. Fellows '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. @@ -170,6 +170,13 @@ the .QW "\fIoptions ...\fR" to the \fBzlib push\fR command: .TP +\fB\-dictionary\fI binData\fR +.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. +.VE +.TP \fB\-header\fI dictionary\fR . Passes a description of the gzip header to create, in the same format that @@ -179,15 +186,33 @@ Passes a description of the gzip header to create, in the same format that . How hard to compress the data. Must be an integer from 0 (uncompressed) to 9 (maximally compressed). -'\".TP -'\"\fB\-limit\fI readaheadLimit\fR -'\". -'\"The maximum number of bytes ahead to read. -'\"\fITODO: not yet implemented!\fR +.TP +\fB\-limit\fI readaheadLimit\fR +. +The maximum number of bytes ahead to read when decompressing. This defaults to +1, which ensures that data is always decompressed correctly, but may be +increased to improve performance. This is more useful when the channel is +non-blocking. .PP Both compressing and decompressing channel transformations add extra -configuration options that may be accessed through \fBchan configure\fR. Each -option is either a read-only or a write-only option. The options are: +configuration options that may be accessed through \fBchan configure\fR. The +options are: +.TP +\fB\-checksum\fI checksum\fR +. +This read-only option gets the current checksum for the uncompressed data that +the compression engine has seen so far. It is valid for both compressing and +decompressing transforms, but not for the raw inflate and deflate formats. The +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. +.VE .TP \fB\-flush\fI type\fR . @@ -198,63 +223,80 @@ expensive flush respectively. Flushing degrades the compression ratio, but makes it easier for a decompressor to recover more of the file in the case of data corruption. .TP -\fB\-checksum\fR -. -This read-only option gets the current checksum for the uncompressed data -that the compression engine has seen so far. It is valid for both -compressing and decompressing transforms, but not for the raw inflate -and deflate formats. The compression algorithm depends on what -format is being produced or consumed. -.TP -\fB\-header\fR +\fB\-header\fI dictionary\fR . This read-only option, only valid for decompressing transforms that are processing gzip-format data, returns the dictionary describing the header read off the data stream. +.TP +\fB\-limit\fI readaheadLimit\fR +. +This read-write option is used by decompressing channels to control the +maximum number of bytes ahead to read from the underlying data source. This +defaults to 1, which ensures that data is always decompressed correctly, but +may be increased to improve performance. This is more useful when the channel +is non-blocking. .RE .SS "STREAMING SUBCOMMAND" .TP -\fBzlib stream\fI mode\fR ?\fIlevel\fR? +\fBzlib stream\fI mode\fR ?\fIoptions\fR? . Creates a streaming compression or decompression command based on the \fImode\fR, and return the name of the command. For a description of how that command works, see \fBSTREAMING INSTANCE COMMAND\fR below. The following modes -are supported: +and \fIoptions\fR are supported: .RS .TP -\fBzlib stream compress\fR ?\fIlevel\fR? +\fBzlib stream compress\fR ?\fB\-dictionary \fIbindata\fR? ?\fB\-level \fIlevel\fR? . The stream will be a compressing stream that produces zlib-format output, using compression level \fIlevel\fR (if specified) which will be an integer -from 0 to 9. +from 0 to 9, +.VS "TIP 400" +and the compression dictionary \fIbindata\fR (if specified). +.VE .TP -\fBzlib stream decompress\fR +\fBzlib stream decompress\fR ?\fB\-dictionary \fIbindata\fR? . The stream will be a decompressing stream that takes zlib-format input and produces uncompressed output. +.VS "TIP 400" +If \fIbindata\fR is supplied, it is a compression dictionary to use if +required. +.VE .TP -\fBzlib stream deflate\fR ?\fIlevel\fR? +\fBzlib stream deflate\fR ?\fB\-dictionary \fIbindata\fR? ?\fB\-level \fIlevel\fR? . The stream will be a compressing stream that produces raw output, using compression level \fIlevel\fR (if specified) which will be an integer from 0 -to 9. +to 9, +.VS "TIP 400" +and the compression dictionary \fIbindata\fR (if specified). Note that +the raw compressed data includes no metadata about what compression +dictionary was used, if any; that is a feature of the zlib-format data. +.VE .TP \fBzlib stream gunzip\fR . The stream will be a decompressing stream that takes gzip-format input and produces uncompressed output. .TP -\fBzlib stream gzip\fR ?\fIlevel\fR? +\fBzlib stream gzip\fR ?\fB\-header \fIheader\fR? ?\fB\-level \fIlevel\fR? . The stream will be a compressing stream that produces gzip-format output, using compression level \fIlevel\fR (if specified) which will be an integer -from 0 to 9. -'\" TODO: Header dictionary! +from 0 to 9, and the header descriptor dictionary \fIheader\fR (if specified; +for keys see \fBzlib gzip\fR). .TP -\fBzlib stream inflate\fR +\fBzlib stream inflate\fR ?\fB\-dictionary \fIbindata\fR? . The stream will be a decompressing stream that takes raw compressed input and produces uncompressed output. +.VS "TIP 400" +If \fIbindata\fR is supplied, it is a compression dictionary to use. Note that +there are no checks in place to determine whether the compression dictionary +is correct. +.VE .RE .SS "CHECKSUMMING SUBCOMMANDS" .TP @@ -277,10 +319,10 @@ the transformed data. The full set of subcommands supported by a streaming instance command, \fIstream\fR, is as follows: .TP -\fIstream \fBadd\fR ?\fIoption\fR? \fIdata\fR +\fIstream \fBadd\fR ?\fIoption...\fR? \fIdata\fR . A short-cut for -.QW "\fIstream \fBput \fIoption data\fR" +.QW "\fIstream \fBput \fR?\fIoption...\fR? \fIdata\fR" followed by .QW "\fIstream \fBget\fR" . .TP @@ -318,15 +360,27 @@ A short-cut for Return up to \fIcount\fR bytes from \fIstream\fR's internal buffers with the transformation applied. If \fIcount\fR is omitted, the entire contents of the buffers are returned. +. +\fIstream \fBheader\fR +. +Return the gzip header description dictionary extracted from the stream. Only +supported for streams created with their \fImode\fR parameter set to +\fBgunzip\fR. .TP -\fIstream \fBput\fR ?\fIoption\fR? \fIdata\fR +\fIstream \fBput\fR ?\fIoption...\fR? \fIdata\fR . Append the contents of the binary string \fIdata\fR to \fIstream\fR's internal -buffers while applying the transformation. If present, \fIoption\fR must be -one of the following (or an unambiguous prefix) which are used to modify the +buffers while applying the transformation. The following \fIoption\fRs are +supported (or an unambiguous prefix of them), which are used to modify the way in which the transformation is applied: .RS .TP +\fB\-dictionary\fI binData\fR +.VS "TIP 400" +Sets the compression dictionary to use when working with compressing or +decompressing the data to be \fIbinData\fR. +.VE +.TP \fB\-finalize\fR . Mark the stream as finished, ensuring that all bytes have been wholly @@ -334,12 +388,22 @@ compressed or decompressed. For gzip streams, this also ensures that the footer is written to the stream. The stream will need to be reset before having more data written to it after this, though data can still be read out of the stream with the \fBget\fR subcommand. +.RS +.PP +This option is mutually exclusive with the \fB\-flush\fR and \fB\-fullflush\fR +options. +.RE .TP \fB\-flush\fR . Ensure that a decompressor consuming the bytes that the current (compressing) stream is producing will be able to produce all the bytes that have been compressed so far, at some performance penalty. +.RS +.PP +This option is mutually exclusive with the \fB\-finalize\fR and +\fB\-fullflush\fR options. +.RE .TP \fB\-fullflush\fR . @@ -347,6 +411,11 @@ Ensure that not only can a decompressor handle all the bytes produced so far (as with \fB\-flush\fR above) but also that it can restart from this point if it detects that the stream is partially corrupt. This incurs a substantial performance penalty. +.RS +.PP +This option is mutually exclusive with the \fB\-finalize\fR and \fB\-flush\fR +options. +.RE .RE .TP \fIstream \fBreset\fR |