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diff --git a/libical/doc/UsingLibical.lyx b/libical/doc/UsingLibical.lyx new file mode 100644 index 0000000000..20eaffd288 --- /dev/null +++ b/libical/doc/UsingLibical.lyx @@ -0,0 +1,719 @@ +#This file was created by <eric> Mon Feb 7 20:19:42 2000 +#LyX 1.0 (C) 1995-1999 Matthias Ettrich and the LyX Team +\lyxformat 2.15 +\textclass linuxdoc +\language default +\inputencoding default +\fontscheme default +\graphics default +\paperfontsize default +\spacing single +\papersize Default +\paperpackage a4 +\use_geometry 0 +\use_amsmath 0 +\paperorientation portrait +\secnumdepth 3 +\tocdepth 3 +\paragraph_separation indent +\defskip medskip +\quotes_language english +\quotes_times 2 +\papercolumns 1 +\papersides 1 +\paperpagestyle default + +\layout Title + +Using Libical +\layout Author + +Eric Busboom (eric@softwarestudio.org) +\layout Date + +January 2000 +\layout Section + +Introduction +\layout Standard + +Libical is an Open Source implementation of the iCalendar protocols and + protocol data units. + The iCalendar specification describes how calendar clients can communicate + with calendar servers for users can store their calendar data and arrange + meetings with other users. + +\layout Standard + +Libical implements the following specifications and protocols +\layout Standard +\added_space_top 0.3cm \added_space_bottom 0.3cm \align center \LyXTable +multicol5 +5 2 0 0 -1 -1 -1 -1 +1 1 0 0 +1 1 0 0 +1 1 0 0 +1 1 0 0 +1 1 0 0 +8 1 0 "" "" +8 1 1 "" "" +0 8 1 0 0 0 0 "" "" +0 8 1 0 0 0 0 "" "" +0 8 1 0 0 0 0 "" "" +0 8 1 0 0 0 0 "" "" +0 8 1 0 0 0 0 "" "" +0 8 1 0 0 0 0 "" "" +0 8 1 0 0 0 0 "" "" +0 8 1 0 0 0 0 "" "" +0 8 1 0 0 0 0 "" "" +0 8 1 0 0 0 0 "" "" + +iCal Core +\newline +2445 +\newline +iTIP +\newline +2446 +\newline +iMIP +\newline +2447 +\newline +iRIP +\newline +draft +\newline +CAP +\newline +draft +\layout Standard + +(The current version, 0.14, does not implement iRip or CAP. + ) +\layout Standard + +This documentation assumes that you are familiar with the iCalendar standards + RFC2445 and RFC2446. +\layout Subsection + +The libical project +\layout Standard + +This code is under active development. + If you would like to contribute to the project, you can contact me, Eric + Busboom, at eric@softwarestudio.org. + The project has a webpage at +\layout Quote + +http://softwarestudio.org/libical/index.html +\layout Standard + +and a mailing list that you can join by sending the following mail: +\layout Code + +To: minimalist@softwarestudio.org +\layout Code + +Subject: subscribe libical +\layout Subsection + +License +\layout Standard + +The code and datafiles in this distribution are licensed under the Mozilla + Public License. + See http://www.mozilla.org/NPL/MPL-1.0.html for a copy of the license. + Alternately, you may use libical under the terms of the GNU Library General + Public License. + See http://www.fsf.org/copyleft/lesser.html for a copy of the LGPL. +\layout Standard + +This dual license ensures that the library can be incorporated into both + proprietary code and GPL'd programs, and will benefit from improvements + made by programmers in both realms. + I will only accept changes into my version of the library if they are similarly + dual-licensed. +\layout Subsection + +Purpose & Goals +\layout Subsection + +Document version +\layout Standard + +$Id: UsingLibical.lyx,v 1.1 2000/02/17 18:02:36 alves Exp $ +\layout Section + +Building the Library +\layout Section + +Structure +\layout Standard + +The iCal calendar model is based on four types of objects: components, propertie +s, values and parameters. + +\layout Standard + +Properties are the fundamental unit of information in iCal, and they work + a bit like a hash entry, with a constant key and a variable value. + Properties may also have modifiers, called parameters. + In the iCal content line +\layout Code + +ORGANIZER;ROLE=CHAIR:MAILTO:mrbig@host.com +\layout Standard + +The property name is +\begin_inset Quotes eld +\end_inset + +ORGANIZER, +\begin_inset Quotes erd +\end_inset + + the value of the property is +\begin_inset Quotes eld +\end_inset + +mrbig@host.com +\begin_inset Quotes erd +\end_inset + + and the +\begin_inset Quotes eld +\end_inset + +ROLE +\begin_inset Quotes erd +\end_inset + + parameter specifies that Mr Big is the chair of the meetings associated + with this property. + +\layout Standard + +Components are groups of properties that represent the core objects of a + calendar system, such as events or timezones. + +\layout Standard + +The central goal of libical is to parse iTIP data into an internal representatio +n of Components, Properties, Parameters an Values, and to allow the user + to manipulate the data in various ways +\layout Subsection + +Components +\layout Subsection + +Properties +\layout Subsection + +Values +\layout Subsection + +Parameters +\layout Subsection + +Enumerations +\layout Subsection + +Types +\layout Subsection + +The Parser +\layout Subsection + +Restrictions +\layout Subsection + +Memory Management +\layout Section + +Differences From RFCs +\layout Standard + +Libical has been designed to follow the standards as closely as possible, + so that the key objects in the standards are also keey objects in the library. + However, there are a few areas where the specifications are (arguably) + irregular, and following them exactly would result in an unfriendly interface. + These deviations make libical easier to use by maintaining a self-similar + interface. + +\layout Subsection + +Pseudo Components +\layout Standard + +Libical defines components for groups of properties that look and act like + components, but are not defined as components in the specification. + XDAYLIGHT and XSTANDARD are notable examples. + These pseudo components group properties within the VTIMEZONE components. + XDAYLIGHT starts with +\begin_inset Quotes eld +\end_inset + +BEGIN:DAYLIGHT +\begin_inset Quotes erd +\end_inset + + and ends with +\begin_inset Quotes eld +\end_inset + +END:DAYLIGHT, just like other components, but is not defined as a component + in RFC2445. + ( See RFC2445, page 61 ) In Libical, it is a component. + +\layout Standard + +There are also pseudo components that are conceptually derived classess + of VALARM. + RFC2446 defines what properties may be included in each component, and + for VALARM, the set of properties it may have depends on the value of the + ACTION property. + +\layout Standard + +For instance, if a VALARM component has an ACTION property with the value + of +\begin_inset Quotes eld +\end_inset + +AUDIO, +\begin_inset Quotes erd +\end_inset + + the component must also have an +\begin_inset Quotes eld +\end_inset + +ATTACH +\begin_inset Quotes erd +\end_inset + + property. + However, if the ACTION value is +\begin_inset Quotes eld +\end_inset + +DISPLAY, +\begin_inset Quotes erd +\end_inset + + the component must have a DESCRIPTION property. + +\layout Standard + +To handle these various, complex restrictions, libical has pseudo components + for each type of alarm: XAUDIOALARM, XDISPLAYALARM, XEMAILALARM and XPROCEDUREA +LARM. + +\layout Subsection + +Combined Values +\layout Standard + +Many values can take more than one type. + TRIGGER, for instance, can have a value type of with DURATION or of DATE-TIME. + These multiple types make it difficult to create routines to return the + value associated with a property. + +\layout Standard + +It is natural to have interfaces that would return the value of a property, + but it is cumbersone for a single routine to return multiple types. + So, in libical, properties that can have multiple types are given a single + type that is the union of their RFC2445 types. + For instance, in libical, the value of the TRIGGER property resolves to + +\noun on +struct icaltriggertype +\noun default +. + This type is a union of a DURATION and a DATE-TIME. + +\layout Subsection + +Multi-Valued Properties +\layout Standard + +Some properties, such as CATEGORIES have only one value type, but each CATEGORIE +S property can have multiple value instances. + This also results in a cumbersome interface -- CATEGORIES accessors would + have to return a list while all other accessors returned a single value. + In libical, all properties have a single value, and multi-valued properties + are broken down into multiple single valued properties during parsing. + That is, an input line like, +\layout Code + +CATEGORIES: work, home +\layout Standard + +becomes in libical's internal representation +\layout Code + +CATEGORIES: work +\layout Code + +CATEGORIES: home +\layout Standard + +Oddly, RFC2445 allows some multi-valued properties ( like FREEBUSY ) to + exist as both a multi-values property and as multiple single value properties, + while others ( like CATEGORIES ) can only exist as single multi-valued + properties. + This makes the internal representation for CATEGORIES illegal. + However when you convert a component to a string, the library will collect + all of the CATEGORIES properties into one. + +\layout Section + +Implementation Limitations +\layout Section + +Using libical +\layout Subsection + +Creating Components +\layout Standard + +There are three ways to create components in Libical: creating individual + objects and assembling them, building entire objects in massive vaargs + calls, and parsing a text file containing iCalendar data. + +\layout Subsubsection + +Constructor Interfaces +\layout Standard + +Using constructor interfaces, you create each of the objects seperately + and them assemble them in to components: +\layout Code + +event = icalcomponent_new(ICAL_VEVENT_COMPONENT); +\layout Code + +icalcomponent_add_property(event, icalproperty_new_dtstamp(atime) ); +\layout Code + +icalcomponent_add_property(event,icalproperty_new_uid(strdup("guid-1.host1.com")) + ); +\layout Code + +property=icalproperty_new_organizer(strdup("mrbig@host.com")); +\layout Code + +icalproperty_add_parameter(property,icalparameter_new_role(ICAL_ROLE_CHAIR) + ); +\layout Code + +icalcomponent_add_property(event,property); +\layout Subsubsection + +vaargs Constructors +\layout Subsubsection + +Parsing Text Files +\layout Subsection + +Accessing Components +\layout Subsubsection + +Finding Components +\layout Subsubsection + +Removing Components +\layout Standard + +Removing an element from a list while iterating through the list can cause + problems, since you will probably be removing the element that the internal + iterator points to. + This will result in the iteration loop terminating immediately after removing + the element. + To avoid the problem, you will need to step the iterator ahead of the element + you are going to remove, like this: +\layout Code + +for(c = icalcomponent_get_first_component(parent_comp,ICAL_ANY_COMPONENT); + +\layout Code + + +\protected_separator + +\protected_separator + +\protected_separator + +\protected_separator +c != 0; +\layout Code + + +\protected_separator + +\protected_separator + +\protected_separator + +\protected_separator +c = next +\layout Code + +{ +\layout Code + + +\protected_separator + +\protected_separator + next = icalcomponent_get_next_component(parent_comp,ICAL_ANY_COMPONENT); +\layout Code + + +\protected_separator + +\protected_separator + icalcomponent_remove_component(parent_comp,c); +\layout Code + +} +\layout Subsubsection + +Finding Properties +\layout Subsubsection + +Removing Properties +\layout Subsubsection + +Getting Values +\layout Subsubsection + +Setting Values +\layout Subsubsection + +Getting Parameters +\layout Subsubsection + +Setting Parameters +\layout Subsubsection + +Removing Parameters +\layout Subsubsection + +Checking Component Validity +\layout Subsection + +Storing Objects +\layout Standard + +The libical distribution inclues a seperate library, libicalss, that allows + you to store iCal component data to disk in a variety of ways. + This library is documented seperately. + +\layout Subsection + +Memory Management +\layout Standard + +Libical relies heavily on dynamic allocation for both the core objects and + for the strings used to hold values. + Some of this memory the library caller owns and must free, and some of + the memory is managed by the library. + Here is a summary of the memory rules. + +\layout Description + +1) If the function name has "new" in it, the caller gets control of the + memory. + ( such as icalcomponent_new(), or icalproperty_new_clone() ) +\layout Description + +2) If you got the memory from a routine with new in it, you must call the + corresponding *_free routine to free the memory. + ( Use icalcomponent_free() to free objects created with icalcomponent_new()) + +\layout Description + +3) If the function name has "add" in it, the caller is transfering control + of the memory to the routine. + ( icalproperty_add_parameter() ) +\layout Description + +4) If the function name has "remove" in it, the caller passes in a pointer + to an object and after the call returns, the caller owns the object. + So, before you call icalcomponent_remove_property(comp,foo), you do not + own "foo" and after the call returns, you do. + +\layout Description + +5) If the routine returns a string, libical owns the memory and will put + it on a ring buffer to reclaim later. + You'd better strdup() it if you want to keep it, and you don't have to + delete it. + +\layout Subsection + +Error Handling +\layout Standard + +icalerror_errno. + Return values. + #defines. + icalerror_stop_here +\layout Subsubsection + +Return values +\layout Subsubsection + +icalerrno +\layout Subsubsection + +Component errors +\layout Subsection + +Naming Standard +\layout Standard + +Structures that you access with the +\begin_inset Quotes eld +\end_inset + +struct +\begin_inset Quotes erd +\end_inset + + keyword, such as +\begin_inset Quotes eld +\end_inset + +struct icaltimetype +\begin_inset Quotes erd +\end_inset + + are things that you are allowed to see inside and poke at. + +\layout Standard + +Structures that you access though a typedef, such as +\begin_inset Quotes eld +\end_inset + +icalcomponent +\begin_inset Quotes erd +\end_inset + + are things where all of the data is hidden. + +\layout Standard + +Component names that start with +\begin_inset Quotes eld +\end_inset + +V +\begin_inset Quotes erd +\end_inset + + are part of RFC 2445 or another iCal standard. + Component names that start with +\begin_inset Quotes eld +\end_inset + +X +\begin_inset Quotes erd +\end_inset + + are also part of the spec, but they are not actually components in the + spec. + However, they look and act like components, so they are components in libical. + Names that start with +\begin_inset Quotes eld +\end_inset + +XLIC +\begin_inset Quotes erd +\end_inset + + or +\begin_inset Quotes eld +\end_inset + +X-LIC +\begin_inset Quotes erd +\end_inset + + are not part of any iCal spec. + They are used internally by libical. + +\layout Standard + +Enums that identify a component, property, value or parameter end with +\begin_inset Quotes eld +\end_inset + +_COMPONENT, +\begin_inset Quotes erd +\end_inset + + +\begin_inset Quotes eld +\end_inset + +_PROPERTY, +\begin_inset Quotes erd +\end_inset + + +\begin_inset Quotes eld +\end_inset + +_VALUE, +\begin_inset Quotes erd +\end_inset + + or +\begin_inset Quotes eld +\end_inset + +_PAAMETER +\begin_inset Quotes erd +\end_inset + +s +\layout Standard + +Enums that identify a parameter value have the name of the parameter as + the second word. + For instance: ICAL_ROLE_REQPARTICIPANT or ICAL_PARTSTAT_ACCEPTED. +\layout Standard + +The enums for the parts of a recurarance rule and request statuses are irregular. + +\layout Section + +Useful Recipies +\layout Standard + +Iteration +\layout Standard + +Copying components. + Remember that you must clone or remove an object before putting in on anothr + list. + +\layout Standard + +Finding compliance errors +\layout Section + +Performance +\layout Standard + +Checking restrictions is computationally expensive +\layout Section + +Hacks and Bugs +\the_end |