'\" '\" Generated from file 'async\&.man' by tcllib/doctools with format 'nroff' '\" Copyright (c) 2008 Andreas Kupries '\" .TH "cache::async" 3tcl 0\&.3\&.1 tcllib "In-memory caches" .\" The -*- nroff -*- definitions below are for supplemental macros used .\" in Tcl/Tk manual entries. .\" .\" .AP type name in/out ?indent? .\" Start paragraph describing an argument to a library procedure. .\" type is type of argument (int, etc.), in/out is either "in", "out", .\" or "in/out" to describe whether procedure reads or modifies arg, .\" and indent is equivalent to second arg of .IP (shouldn't ever be .\" needed; use .AS below instead) .\" .\" .AS ?type? ?name? .\" Give maximum sizes of arguments for setting tab stops. Type and .\" name are examples of largest possible arguments that will be passed .\" to .AP later. If args are omitted, default tab stops are used. .\" .\" .BS .\" Start box enclosure. From here until next .BE, everything will be .\" enclosed in one large box. .\" .\" .BE .\" End of box enclosure. .\" .\" .CS .\" Begin code excerpt. .\" .\" .CE .\" End code excerpt. .\" .\" .VS ?version? ?br? .\" Begin vertical sidebar, for use in marking newly-changed parts .\" of man pages. The first argument is ignored and used for recording .\" the version when the .VS was added, so that the sidebars can be .\" found and removed when they reach a certain age. If another argument .\" is present, then a line break is forced before starting the sidebar. .\" .\" .VE .\" End of vertical sidebar. .\" .\" .DS .\" Begin an indented unfilled display. .\" .\" .DE .\" End of indented unfilled display. .\" .\" .SO ?manpage? .\" Start of list of standard options for a Tk widget. The manpage .\" argument defines where to look up the standard options; if .\" omitted, defaults to "options". The options follow on successive .\" lines, in three columns separated by tabs. .\" .\" .SE .\" End of list of standard options for a Tk widget. .\" .\" .OP cmdName dbName dbClass .\" Start of description of a specific option. cmdName gives the .\" option's name as specified in the class command, dbName gives .\" the option's name in the option database, and dbClass gives .\" the option's class in the option database. .\" .\" .UL arg1 arg2 .\" Print arg1 underlined, then print arg2 normally. .\" .\" .QW arg1 ?arg2? .\" Print arg1 in quotes, then arg2 normally (for trailing punctuation). .\" .\" .PQ arg1 ?arg2? .\" Print an open parenthesis, arg1 in quotes, then arg2 normally .\" (for trailing punctuation) and then a closing parenthesis. .\" .\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. .if t .wh -1.3i ^B .nr ^l \n(.l .ad b .\" # Start an argument description .de AP .ie !"\\$4"" .TP \\$4 .el \{\ . ie !"\\$2"" .TP \\n()Cu . el .TP 15 .\} .ta \\n()Au \\n()Bu .ie !"\\$3"" \{\ \&\\$1 \\fI\\$2\\fP (\\$3) .\".b .\} .el \{\ .br .ie !"\\$2"" \{\ \&\\$1 \\fI\\$2\\fP .\} .el \{\ \&\\fI\\$1\\fP .\} .\} .. .\" # define tabbing values for .AP .de AS .nr )A 10n .if !"\\$1"" .nr )A \\w'\\$1'u+3n .nr )B \\n()Au+15n .\" .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n .nr )C \\n()Bu+\\w'(in/out)'u+2n .. .AS Tcl_Interp Tcl_CreateInterp in/out .\" # BS - start boxed text .\" # ^y = starting y location .\" # ^b = 1 .de BS .br .mk ^y .nr ^b 1u .if n .nf .if n .ti 0 .if n \l'\\n(.lu\(ul' .if n .fi .. .\" # BE - end boxed text (draw box now) .de BE .nf .ti 0 .mk ^t .ie n \l'\\n(^lu\(ul' .el \{\ .\" Draw four-sided box normally, but don't draw top of .\" box if the box started on an earlier page. .ie !\\n(^b-1 \{\ \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .el \}\ \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .\} .fi .br .nr ^b 0 .. .\" # VS - start vertical sidebar .\" # ^Y = starting y location .\" # ^v = 1 (for troff; for nroff this doesn't matter) .de VS .if !"\\$2"" .br .mk ^Y .ie n 'mc \s12\(br\s0 .el .nr ^v 1u .. .\" # VE - end of vertical sidebar .de VE .ie n 'mc .el \{\ .ev 2 .nf .ti 0 .mk ^t \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n' .sp -1 .fi .ev .\} .nr ^v 0 .. .\" # Special macro to handle page bottom: finish off current .\" # box/sidebar if in box/sidebar mode, then invoked standard .\" # page bottom macro. .de ^B .ev 2 'ti 0 'nf .mk ^t .if \\n(^b \{\ .\" Draw three-sided box if this is the box's first page, .\" draw two sides but no top otherwise. .ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .\} .if \\n(^v \{\ .nr ^x \\n(^tu+1v-\\n(^Yu \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c .\} .bp 'fi .ev .if \\n(^b \{\ .mk ^y .nr ^b 2 .\} .if \\n(^v \{\ .mk ^Y .\} .. .\" # DS - begin display .de DS .RS .nf .sp .. .\" # DE - end display .de DE .fi .RE .sp .. .\" # SO - start of list of standard options .de SO 'ie '\\$1'' .ds So \\fBoptions\\fR 'el .ds So \\fB\\$1\\fR .SH "STANDARD OPTIONS" .LP .nf .ta 5.5c 11c .ft B .. .\" # SE - end of list of standard options .de SE .fi .ft R .LP See the \\*(So manual entry for details on the standard options. .. .\" # OP - start of full description for a single option .de OP .LP .nf .ta 4c Command-Line Name: \\fB\\$1\\fR Database Name: \\fB\\$2\\fR Database Class: \\fB\\$3\\fR .fi .IP .. .\" # CS - begin code excerpt .de CS .RS .nf .ta .25i .5i .75i 1i .. .\" # CE - end code excerpt .de CE .fi .RE .. .\" # UL - underline word .de UL \\$1\l'|0\(ul'\\$2 .. .\" # QW - apply quotation marks to word .de QW .ie '\\*(lq'"' ``\\$1''\\$2 .\"" fix emacs highlighting .el \\*(lq\\$1\\*(rq\\$2 .. .\" # PQ - apply parens and quotation marks to word .de PQ .ie '\\*(lq'"' (``\\$1''\\$2)\\$3 .\"" fix emacs highlighting .el (\\*(lq\\$1\\*(rq\\$2)\\$3 .. .\" # QR - quoted range .de QR .ie '\\*(lq'"' ``\\$1''\\-``\\$2''\\$3 .\"" fix emacs highlighting .el \\*(lq\\$1\\*(rq\\-\\*(lq\\$2\\*(rq\\$3 .. .\" # MT - "empty" string .de MT .QW "" .. .BS .SH NAME cache::async \- Asynchronous in-memory cache .SH SYNOPSIS package require \fBTcl 8\&.4\fR .sp package require \fBcache::async ?0\&.3\&.1?\fR .sp \fB::cache::async\fR \fIobjectName\fR \fIcommandprefix\fR ?\fIoptions\fR\&.\&.\&.? .sp \fIobjectName\fR \fBget\fR \fIkey\fR \fIdonecmdprefix\fR .sp \fIobjectName\fR \fBset\fR \fIkey\fR \fIvalue\fR .sp \fIobjectName\fR \fBunset\fR \fIkey\fR .sp \fIobjectName\fR \fBexists\fR \fIkey\fR .sp \fIobjectName\fR \fBclear\fR ?\fIkey\fR? .sp .BE .SH DESCRIPTION This package provides objects which cache data in memory, and operate asynchronously with regard to request and responses\&. The objects are agnostic with regard to cache keys and values, and unknown methods are delegated to the provider of cached data\&. These two properties make it easy to use caches as a facade for any data provider\&. .SH API The package exports a class, \fBcache::async\fR, as specified below\&. .TP \fB::cache::async\fR \fIobjectName\fR \fIcommandprefix\fR ?\fIoptions\fR\&.\&.\&.? The command creates a new \fIcache\fR object with an associated global Tcl command whose name is \fIobjectName\fR\&. This command may be used to invoke various operations on the object\&. .sp The \fIcommandprefix\fR is the action to perform when an user asks for data in the cache and the cache doesn't yet know about the key\&. When run the commandprefix is given three additional arguments, the string \fBget\fR, the key requested, and the cache object itself, in the form of its object command, in this order\&. The execution of the action is done in an idle-handler, decoupling it from the original request\&. .sp The only supported option is .RS .TP \fB-full-async-results\fR This option defines the behaviour of the cache for when requested keys are known to the cache at the time of \fBget\fR request\&. By default such requeste are responded to asynchronously as well\&. Setting this option to \fBfalse\fR forces the cache to respond to them synchronuously, although still through the specified callback\&. .RE .PP The object commands created by the class commands above have the form: .TP \fIobjectName\fR \fBget\fR \fIkey\fR \fIdonecmdprefix\fR This method requests the data for the \fIkey\fR from the cache\&. If the data is not yet known the command prefix specified during construction of the cache object is used to ask for this information\&. .sp Whenever the information is/becomes available the \fIdonecmdprefix\fR will be run to transfer the result to the caller\&. This command prefix is invoked with either 2 or 3 arguments, i\&.e\&. .RS .IP [1] The string \fBset\fR, the \fIkey\fR, and the value\&. .IP [2] The string \fBunset\fR, and the \fIkey\fR\&. .RE .IP These two possibilities are used to either signal the value for the \fIkey\fR, or that the \fIkey\fR has no value defined for it\&. The latter is distinct from the cache not knowing about the \fIkey\fR\&. .sp For a cache object configured to be fully asynchronous (default) the \fIdonecmdprefix\fR is always run in an idle-handler, decoupling it from the request\&. Otherwise the callback will be invoked synchronously when the \fIkey\fR is known to the cache at the time of the invokation\&. .sp Another important part of the cache's behaviour, as it is asynchronous it is possible that multiple \fBget\fR requests are issued for the same \fIkey\fR before it can respond\&. In that case the cache will issue only one data request to the provider, for the first of these, and suspend the others, and then notify all of them when the data becomes available\&. .TP \fIobjectName\fR \fBset\fR \fIkey\fR \fIvalue\fR .TP \fIobjectName\fR \fBunset\fR \fIkey\fR These two methods are provided to allow users of the cache to make keys known to the cache, as either having a \fIvalue\fR, or as undefined\&. .sp It is expected that the data provider (see \fIcommandprefix\fR of the constructor) uses them in response to data requests for unknown keys\&. .sp Note how this matches the cache's own API towards its caller, calling the \fIdonecmd\fR of \fBget\fR-requests issued to itself with either "set key value" or "unset key", versus issuing \fBget\fR-requests to its own provider with itself in the place of the \fIdonecmd\fR, expecting to be called with either "set key value" or "unset key"\&. .sp This also means that these methods invoke the \fIdonecmd\fR of all \fBget\fR-requests waiting for information about the modified \fIkey\fR\&. .TP \fIobjectName\fR \fBexists\fR \fIkey\fR This method queries the cache for knowledge about the \fIkey\fR and returns a boolean value\&. The result is \fBtrue\fR if the key is known, and \fBfalse\fR otherwise\&. .TP \fIobjectName\fR \fBclear\fR ?\fIkey\fR? This method resets the state of either the specified \fIkey\fR or of all keys known to the cache, making it unkown\&. This forces future \fBget\fR-requests to reload the information from the provider\&. .PP .SH "BUGS, IDEAS, FEEDBACK" This document, and the package it describes, will undoubtedly contain bugs and other problems\&. Please report such in the category \fIcache\fR of the \fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&. Please also report any ideas for enhancements you may have for either package and/or documentation\&. .PP When proposing code changes, please provide \fIunified diffs\fR, i\&.e the output of \fBdiff -u\fR\&. .PP Note further that \fIattachments\fR are strongly preferred over inlined patches\&. Attachments can be made by going to the \fBEdit\fR form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar\&. .SH KEYWORDS asynchronous, cache, callback, synchronous .SH COPYRIGHT .nf Copyright (c) 2008 Andreas Kupries .fi