'\" '\" Generated from file 'tie\&.man' by tcllib/doctools with format 'nroff' '\" Copyright (c) 2004-2008 Andreas Kupries '\" .TH "tie" 3tcl 1\&.1 tcllib "Tcl Data Structures" .\" 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 tie \- Array persistence .SH SYNOPSIS package require \fBTcl 8\&.4\fR .sp package require \fBtie ?1\&.1?\fR .sp \fB::tie::tie\fR \fIarrayvarname\fR \fIoptions\fR\&.\&.\&. \fIdstype\fR \fIdsname\fR\&.\&.\&. .sp \fB::tie::untie\fR \fIarrayvarname\fR ?\fItoken\fR? .sp \fB::tie::info\fR \fBties\fR \fIarrayvarname\fR .sp \fB::tie::info\fR \fBtypes\fR .sp \fB::tie::info\fR \fBtype\fR \fIdstype\fR .sp \fB::tie::register\fR \fIdsclasscmd\fR \fBas\fR \fIdstype\fR .sp \fBdsclasscmd\fR \fIobjname\fR ?\fIdsname\fR\&.\&.\&.? .sp \fBds\fR \fBdestroy\fR .sp \fBds\fR \fBnames\fR .sp \fBds\fR \fBsize\fR .sp \fBds\fR \fBget\fR .sp \fBds\fR \fBset\fR \fIdict\fR .sp \fBds\fR \fBunset\fR ?\fIpattern\fR? .sp \fBds\fR \fBsetv\fR \fIindex\fR \fIvalue\fR .sp \fBds\fR \fBunsetv\fR \fIindex\fR .sp \fBds\fR \fBgetv\fR \fIindex\fR .sp .BE .SH DESCRIPTION The \fBtie\fR package provides a framework for the creation of persistent Tcl array variables\&. It should be noted that the provided mechanism is generic enough to also allow its usage for the distribution of the contents of Tcl arrays over multiple threads and processes, i\&.e\&. communication\&. .PP This, persistence and communication, is accomplished by \fItying\fR) a Tcl array variable to a \fIdata source\fR\&. Examples of data sources are other Tcl arrays and files\&. .PP It should be noted that a single Tcl array variable can be tied to more than one \fIdata source\fR\&. It is this feature which allows the framework to be used for communication as well\&. Just tie several Tcl arrays in many client processes to a Tcl array in a server and all changes to any of them will be distributed to all\&. Less centralized variants of this are of course possible as well\&. .SH "USING TIES" .SS "TIE API" This section describes the basic API used to establish and remove ties between Tcl array variables and data sources\&. This interface is the only one a casual user has to be concerned about\&. The following sections about the various internal interfaces can be safely skipped\&. .TP \fB::tie::tie\fR \fIarrayvarname\fR \fIoptions\fR\&.\&.\&. \fIdstype\fR \fIdsname\fR\&.\&.\&. This command establishes a tie between the Tcl array whose name is provided by the argument \fIarrayvarname\fR and the \fIdata source\fR identified by the \fIdstype\fR and its series of \fIdsname\fR arguments\&. All changes made to the Tcl array after this command returns will be saved to the \fIdata source\fR for safekeeping (or distribution)\&. .sp The result of the command is always a token which identifies the new tie\&. This token can be used later to destroy this specific tie\&. .RS .TP varname \fIarrayvarname\fR (in) The name of the Tcl array variable to connect the new tie to\&. .TP name|command \fIdstype\fR (in) This argument specifies the type of the \fIdata source\fR we wish to access\&. The \fIdstype\fR can be one of \fBlog\fR, \fBarray\fR, \fBremotearray\fR, \fBfile\fR, \fBgrowfile\fR, or \fBdsource\fR; in addition, the programmer can register additional data source types\&. Each \fIdstype\fR is followed by one or more arguments that identify the \fIdata source\fR to which the array is to be tied\&. .TP string \fIdsname\fR (in) The series of \fIdsname\fR arguments coming after the \fIdstype\fR identifies the \fIdata source\fR we wish to connect to, and has to be appropriate for the chosen type\&. .RE .sp The command understands a number of additional options which guide the process of setting up the connection between Tcl array and \fIdata source\fR\&. .sp .RS .TP \fB-open\fR The Tcl array for the new tie is \fIloaded\fR from the \fIdata source\fR, and the previously existing contents of the Tcl array are erased\&. Care is taken to \fInot\fR erase the previous contents should the creation of the tie fail\&. .sp This option and the option \fB-save\fR exclude each other\&. If neither this nor option \fB-save\fR are specified then this option is assumed as default\&. .TP \fB-save\fR The Tcl array for the new tie is \fIsaved\fR to the \fIdata source\fR, and the previously existing contents of the \fIdata source\fR are erased\&. .sp This option and the option \fB-open\fR exclude each other\&. If neither this nor option \fB-open\fR are specified then option \fB-open\fR is assumed as default\&. .TP \fB-merge\fR Using this option prevents the erasure of any previously existing content and merges the data instead\&. It can be specified in conjunction with either \fB-open\fR or \fB-save\fR\&. They determine how data existing in both Tcl array and \fIdata source\fR, i\&.e duplicates, are dealt with\&. .sp When used with \fB-open\fR data in the \fIdata source\fR has precedence\&. In other words, for duplicates the data in the \fIdata source\fR is loaded into the Tcl array\&. .sp When used with \fB-save\fR data in the Tcl array has precedence\&. In other words, for duplicates the data in the Tcl array is saved into the \fIdata source\fR\&. .RE .sp .TP \fB::tie::untie\fR \fIarrayvarname\fR ?\fItoken\fR? This command dissolves one or more ties associated with the Tcl array named by \fIarrayvarname\fR\&. If no \fItoken\fR is specified then all ties to that Tcl array are dissolved\&. Otherwise only the tie the token stands for is removed, if it is actually connected to the array\&. Trying to remove a specific tie not belonging to the provided array will cause an error\&. .sp It should be noted that while severing a tie will destroy management information internal to the package the \fIdata source\fR which was handled by the tie will not be touched, only closed\&. .sp After the command returns none of changes made to the array will be saved to the \fIdata source\fR anymore\&. .sp The result of the command is an empty string\&. .RS .TP varname \fIarrayname\fR (in) The name of a Tcl array variable which may have ties\&. .TP handle \fItoken\fR (in) A handle representing a specific tie\&. This argument is optional\&. .RE .sp .TP \fB::tie::info\fR \fBties\fR \fIarrayvarname\fR This command returns a list of ties associated with the Tcl array variable named by \fIarrayvarname\fR\&. The result list will be empty if the variable has no ties associated with it\&. .TP \fB::tie::info\fR \fBtypes\fR This command returns a dictionary of registered types, and the class commands they are associated with\&. .TP \fB::tie::info\fR \fBtype\fR \fIdstype\fR This command returns the fully resolved class command for a type name\&. This means that the command will follow a chain of type definitions ot its end\&. .PP .SS "STANDARD DATA SOURCE TYPES" This package provides the six following types as examples and standard data sources\&. .TP \fBlog\fR This \fIdata source\fR does not maintain any actual data, nor persistence\&. It does not accept any identifying arguments\&. All changes are simply logged to \fBstdout\fR\&. .TP \fBarray\fR This \fIdata source\fR uses a regular Tcl array as the origin of the persistent data\&. It accepts a single identifying argument, the name of this Tcl array\&. All changes are mirrored to that array\&. .TP \fBremotearray\fR This \fIdata source\fR is similar to \fBarray\fR\&. The difference is that the Tcl array to which we are mirroring is not directly accessible, but through a \fBsend\fR-like command\&. .sp It accepts three identifying arguments, the name of the other Tcl array, the command prefix for the \fBsend\fR-like accessor command, and an identifier for the remote entity hosting the array, in this order\&. All changes are mirrored to that array, via the command prefix\&. All commands will be executed in the context of the global namespace\&. .sp \fBsend\fR-like means that the command prefix has to have \fBsend\fR syntax and semantics\&. I\&.e\&. it is a channel over which we can send arbitrary commands to some other entity\&. The remote array \fIdata source\fR however uses only the commands \fBset\fR, \fBunset\fR, \fBarray exists\fR, \fBarray names\fR, \fBarray set\fR, and \fBarray get\fR to retrieve and set values in the remote array\&. .sp The command prefix and the entity id are separate to allow the data source to use options like \fB-async\fR when assembling the actual commands\&. .sp Examples of command prefixes, listed with the id of the remote entity, without options\&. In reality only the part before the id is the command prefix: .RS .TP \fBsend\fR \fItkname\fR The Tcl array is in a remote interpreter and is accessed via Tk's X communication\&. .TP \fBcomm::comm send\fR \fIhostportid\fR The Tcl array is in a remote interpreter and is accessed through a socket\&. .TP \fBthread::send\fR \fIthreadid\fR The Tcl array is in a remote interpreter in a different thread of this process\&. .RE .sp .TP \fBfile\fR This \fIdata source\fR uses a single file as origin of the persistent data\&. It accepts a single identifying argument, the path to this file\&. The file has to be both readable and writable\&. It may not exist, the \fIdata source\fR will create it in that case\&. This (and only this) situation will require that the directory for the file exists and is writable as well\&. .sp All changes are saved in the file, as proper Tcl commands, one command per operation\&. In other words, the file will always contain a proper Tcl script\&. .sp If the file exists when the tie using it is set up, then it will be compacted, i\&.e\&. superfluous operations are removed, if the operations log stored in it contains either at least one operation clearing the whole array, or at least 1\&.5 times more operations than entries in the loaded array\&. .TP \fBgrowfile\fR This \fIdata source\fR is like \fBfile\fR in terms of the storage medium for the array data, and how it is configured\&. In constrast to the former it however assumes and ensures that the tied array will never shrink\&. I\&.e\&. the creation of new array entries, and the modification of existing entries is allowed, but the deletion of entries is not, and causes the data source to throw errors\&. .sp This restriction allows us to simplify both file format and access to the file radically\&. For one, the file is read only once and the internal cache cannot be invalidated\&. Second, writing data is reduced to a simple append, and no compaction step is necessary\&. The format of the contents is the string representation of a dictionary which can be incrementally extended forever at the end\&. .TP \fBdsource\fR This \fIdata source\fR uses an explicitly specified \fIdata source object\fR as the source for the persistent data\&. It accepts a single identifying argument, the command prefix, i\&.e\&. object command\&. .sp To use this type it is necessary to know how the framework manages ties and what \fBdata source objects\fR are\&. .sp All changes are delegated to the specified object\&. .PP .SH "CREATING NEW DATA SOURCES" This section is of no interest to the casual user of ties\&. Only developers wishing to create new data sources have to know the information provided herein\&. .SS "DATA SOURCE OBJECTS" All ties are represented internally by an in-memory object which mediates between the tie framework and the specific \fIdata source\fR, like an array, file, etc\&. This is the \fIdata source object\fR\&. .PP Its class, the \fBdata source class\fR is \fInot\fR generic, but specific to the type of the \fIdata source\fR\&. Writing a new \fIdata source\fR requires us to write such a class, and then registering it with the framework as a new type\&. .PP The following subsections describe the various APIs a \fBdata source class\fR and the objects it generates will have to follow to be compatible with the tie framework\&. .PP Data source objects are normally automatically created and destroyed by the framework when a tie is created, or removed\&. This management can be explicitly bypassed through the usage of the "dsource" type\&. The \fIdata source\fR for this type is a \fIdata source object\fR itself, and this object is outside of the scope of the tie framework and not managed by it\&. In other words, this type allows the creation of ties which talk to pre-existing \fIdata source object\fRs, and these objects will survive the removal of the ties using them as well\&. .SS "REGISTERING A NEW DATA SOURCE CLASS" After a \fBdata source class\fR has been written it is necessary to register it as a new type with the framework\&. .TP \fB::tie::register\fR \fIdsclasscmd\fR \fBas\fR \fIdstype\fR Using this command causes the tie framework to remember the class command \fIdsclasscmd\fR of a \fBdata source class\fR under the type name \fIdstype\fR\&. .sp After the call the argument \fIdstype\fR of the basic user command \fB::tie::tie\fR will accept \fIdstype\fR as a type name and translate it internally to the appropriate class command for the creation of \fBdata source objects\fR for the new \fIdata source\fR\&. .PP .SS "DATA SOURCE CLASS" Each data source class is represented by a single command, also called the \fIclass command\fR, or \fIobject creation command\fR\&. Its syntax is .TP \fBdsclasscmd\fR \fIobjname\fR ?\fIdsname\fR\&.\&.\&.? The first argument of the class command is the name of the \fIdata source object\fR to create\&. The framework itself will always supply the string \fB%AUTO%\fR, to signal that the class command has to generate not only the object, but the object name as well\&. .sp This is followed by a series of arguments identifying the data source the new object is for\&. These are the same \fIdsname\fR arguments which are given to the basic user command \fB::tie::tie\fR\&. Their actual meaning is dependent on the \fIdata source class\fR\&. .sp The result of the class command has to be the fully-qualified name of the new \fIdata source object\fR, i\&.e\&. the name of the \fIobject command\fR\&. The interface this command has to follow is described in the section \fBDATA SOURCE OBJECT API\fR .PP .PP .SS "DATA SOURCE OBJECT API" Please read the section \fBDATA SOURCE CLASS\fR first, to know how to generate new \fIobject commands\fR\&. .PP Each \fIobject command\fR for a \fIdata source\fR object has to provide at least the methods listed below for proper inter-operation with the tie framework\&. Note that the names of most of the methods match the subcommands of the builtin \fBarray\fR command\&. .PP .TP \fBds\fR \fBdestroy\fR This method is called when the object \fBds\fR is destroyed\&. It now has to release all its internal resources associated with the external data source\&. .TP \fBds\fR \fBnames\fR This command has to return a list containing the names of all keys found in the \fIdata source\fR the object talks to\&. This is equivalent to \fBarray names\fR\&. .TP \fBds\fR \fBsize\fR This command has to return an integer number specifying the number of keys found in the \fIdata source\fR the object talks to\&. This is equivalent to \fBarray size\fR\&. .TP \fBds\fR \fBget\fR This command has to return a dictionary containing the data found in the \fIdata source\fR the object talks to\&. This is equivalent to \fBarray get\fR\&. .TP \fBds\fR \fBset\fR \fIdict\fR This command takes a dictionary and adds its contents to the data source the object talks to\&. This is equivalent to \fBarray set\fR\&. .TP \fBds\fR \fBunset\fR ?\fIpattern\fR? This command takes a pattern and removes all elements whose keys matching it from the \fIdata source\fR\&. If no pattern is specified it defaults to \fB*\fR, causing the removal of all elements\&. This is nearly equivalent to \fBarray unset\fR\&. .TP \fBds\fR \fBsetv\fR \fIindex\fR \fIvalue\fR This command has to save the \fIvalue\fR in the \fIdata source\fR the object talks to, under the key \fIindex\fR\&. .sp The result of the command is ignored\&. If an error is thrown then this error will show up as error of the set operation which caused the method call\&. .TP \fBds\fR \fBunsetv\fR \fIindex\fR This command has to remove the value under the key \fIindex\fR from the \fIdata source\fR the object talks to\&. .sp The result of the command is ignored\&. If an error is thrown then this error will show up as error of the unset operation which caused the method call\&. .TP \fBds\fR \fBgetv\fR \fIindex\fR This command has to return the value for the key \fIindex\fR in the \fIdata source\fR the object talks to\&. .PP And here a small table comparing the \fIdata source\fR methods to the regular Tcl commands for accessing an array\&. .PP .CS Regular Tcl Data source ----------- ----------- array names a ds names array size a ds size array get a ds get array set a dict ds set dict array unset a pattern ds unset ?pattern? ----------- ----------- set a($idx) $val ds setv idx val unset a($idx) ds unsetv idx $a($idx) ds getv idx ----------- ----------- .CE .SH "BUGS, IDEAS, FEEDBACK" This document, and the package it describes, will undoubtedly contain bugs and other problems\&. Please report such in the category \fItie\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 array, database, file, metakit, persistence, tie, untie .SH CATEGORY Programming tools .SH COPYRIGHT .nf Copyright (c) 2004-2008 Andreas Kupries .fi