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modules/cache/async.man
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rolf
To be able to say "I want a package version which explicitely claims to run with Tcl 9" every package version in tcllib has to be bumped. Started this. Done so far:
29 сен 2023, 04:16
29 сен 2023, 04:16
57c8807
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[vset Version 0.3.2] [manpage_begin cache::async n [vset Version]] [keywords asynchronous] [keywords cache] [keywords callback] [keywords synchronous] [copyright {2008 Andreas Kupries <andreas_kupries@users.sourceforge.net>}] [moddesc {In-memory caches}] [titledesc {Asynchronous in-memory cache}] [require Tcl "8.5 9"] [require cache::async [opt [vset Version]]] [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. [section API] The package exports a class, [class cache::async], as specified below. [list_begin definitions] [call [cmd ::cache::async] [arg objectName] [arg commandprefix] [opt [arg options]...]] The command creates a new [term cache] object with an associated global Tcl command whose name is [arg objectName]. This command may be used to invoke various operations on the object. [para] The [arg commandprefix] 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 [const get], 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. [para] The only supported option is [list_begin options] [opt_def -full-async-results] This option defines the behaviour of the cache for when requested keys are known to the cache at the time of [method get] request. By default such requeste are responded to asynchronously as well. Setting this option to [const false] forces the cache to respond to them synchronuously, although still through the specified callback. [list_end] [list_end] The object commands created by the class commands above have the form: [list_begin definitions] [call [arg objectName] [method get] [arg key] [arg donecmdprefix]] This method requests the data for the [arg key] 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. [para] Whenever the information is/becomes available the [arg donecmdprefix] will be run to transfer the result to the caller. This command prefix is invoked with either 2 or 3 arguments, i.e. [list_begin enum] [enum] The string [const set], the [arg key], and the value. [enum] The string [const unset], and the [arg key]. [list_end] These two possibilities are used to either signal the value for the [arg key], or that the [arg key] has no value defined for it. The latter is distinct from the cache not knowing about the [arg key]. [para] For a cache object configured to be fully asynchronous (default) the [arg donecmdprefix] is always run in an idle-handler, decoupling it from the request. Otherwise the callback will be invoked synchronously when the [arg key] is known to the cache at the time of the invokation. [para] Another important part of the cache's behaviour, as it is asynchronous it is possible that multiple [method get] requests are issued for the same [arg key] 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. [call [arg objectName] [method set] [arg key] [arg value]] [call [arg objectName] [method unset] [arg key]] These two methods are provided to allow users of the cache to make keys known to the cache, as either having a [arg value], or as undefined. [para] It is expected that the data provider (see [arg commandprefix] of the constructor) uses them in response to data requests for unknown keys. [para] Note how this matches the cache's own API towards its caller, calling the [arg donecmd] of [method get]-requests issued to itself with either "set key value" or "unset key", versus issuing [method get]-requests to its own provider with itself in the place of the [arg donecmd], expecting to be called with either "set key value" or "unset key". [para] This also means that these methods invoke the [arg donecmd] of all [method get]-requests waiting for information about the modified [arg key]. [call [arg objectName] [method exists] [arg key]] This method queries the cache for knowledge about the [arg key] and returns a boolean value. The result is [const true] if the key is known, and [const false] otherwise. [call [arg objectName] [method clear] [opt [arg key]]] This method resets the state of either the specified [arg key] or of all keys known to the cache, making it unkown. This forces future [method get]-requests to reload the information from the provider. [list_end] [vset CATEGORY cache] [include ../common-text/feedback.inc] [manpage_end]