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-#LyX 1.1 created this file. For more info see http://www.lyx.org/
-\lyxformat 2.16
-\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 2001
-\layout Standard
-
-
-\begin_inset LatexCommand \tableofcontents{}
-
-\end_inset 
-
-
-\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 so users can store their calendar data and arrange
- meetings with other users.
- 
-\layout Standard
-
-Libical implements RFC2445, RFC2446 and some of RFC2447 and the CAP draft.
- 
-\layout Standard
-
-This documentation assumes that you are familiar with the iCalendar standards
- RFC2445 and RFC2446.
- these specifications are online on the CALSCH webpage at:
-\layout Verbatim
-
-http://www.imc.org/ietf-calendar/
-\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 Verbatim
-
-http://softwarestudio.org/libical/index.html 
-\layout Standard
-
-and a mailing list that you can join by sending the following mail:
-\layout Verbatim
-
-To: minimalist@softwarestudio.org 
-\layout Verbatim
-
-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
-
-Example Code
-\layout Standard
-
-A lot of the documentation for this library is in the form of example code.
- These examples are in the 
-\begin_inset Quotes eld
-\end_inset 
-
-examples
-\begin_inset Quotes erd
-\end_inset 
-
- directory of the distribution.
- Also look in 
-\begin_inset Quotes eld
-\end_inset 
-
-src/test
-\begin_inset Quotes erd
-\end_inset 
-
- for additional annotated examples.
- 
-\layout Section
-
-Building the Library
-\layout Standard
-
-Libical uses autoconf to generate makefiles.
- It should built with no adjustments on Linux, FreeBSD and Solaris under
- gcc.
- Some version have been successfully been build on MacOS, Solaris, UnixWare,
- And Tru64 UNIX without gcc, but you may run into problems with a particular
- later version.
- 
-\layout Standard
-
-For a more complete guide to building the library, see the README file in
- the distribution.
- 
-\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 Verbatim
-
-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.
- Components are delimited by 
-\begin_inset Quotes eld
-\end_inset 
-
-BEGIN
-\begin_inset Quotes erd
-\end_inset 
-
- and 
-\begin_inset Quotes eld
-\end_inset 
-
-END
-\begin_inset Quotes erd
-\end_inset 
-
- tags.
- 
-\layout Standard
-\added_space_bottom 0.3cm 
-When a component is sent across a network, if it is un-encrypted, it will
- look something like:
-\layout Verbatim
-
-BEGIN:VCALENDAR
-\layout Verbatim
-
-METHOD:REQUEST
-\layout Verbatim
-
-PRODID: -//hacksw/handcal//NONSGML v1.0//EN
-\layout Verbatim
-
-BEGIN:VEVENT 
-\layout Verbatim
-
-DTSTAMP:19980309T231000Z 
-\layout Verbatim
-
-UID:guid-1.host1.com 
-\layout Verbatim
-
-ORGANIZER;ROLE=CHAIR:MAILTO:mrbig@host.com 
-\layout Verbatim
-
-ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT;CUTYPE=GROUP: 
-\layout Verbatim
-
-  MAILTO:employee-A@host.com 
-\layout Verbatim
-
-DESCRIPTION:Project XYZ Review Meeting 
-\layout Verbatim
-
-CATEGORIES:MEETING 
-\layout Verbatim
-
-CLASS:PUBLIC 
-\layout Verbatim
-
-CREATED:19980309T130000Z 
-\layout Verbatim
-
-SUMMARY:XYZ Project Review 
-\layout Verbatim
-
-DTSTART;TZID=US-Eastern:19980312T083000 
-\layout Verbatim
-
-DTEND;TZID=US-Eastern:19980312T093000 
-\layout Verbatim
-
-LOCATION:1CP Conference Room 4350 
-\layout Verbatim
-
-END:VEVENT 
-\layout Verbatim
-
-END:VCALENDAR
-\layout Standard
-
-Note that components can be nested; this example has both a VCALENDAR and
- a VEVENT component, one nested inside the other.
- 
-\layout Subsection
-
-Core iCal classes
-\layout Standard
-
-Libical is an object-based, data-oriented library.
- Nearly all of the routines in the library are associated with an opaque
- data types and perform some operation on that data type.
- Although the library does not actually have classes, we will use those
- terms since the behavior of these associations of data and routines is
- very similar to a class.
- 
-\layout Subsubsection
-
-Properties
-\layout Standard
-
-Properties are represented with the icalproperty class and its many 
-\begin_inset Quotes eld
-\end_inset 
-
-derived
-\begin_inset Quotes erd
-\end_inset 
-
- classes with on 
-\begin_inset Quotes eld
-\end_inset 
-
-derived
-\begin_inset Quotes erd
-\end_inset 
-
- class per property type in RFC2445.
- Again, there is no actual inheritance relations, but there are clusters
- of routines that make this term useful.
- A property is a container for a single value and a set of parameters.
- 
-\layout Subsubsection
-
-Components 
-\layout Standard
-
-In libical, components are represented with the icalcomponent class.
- Icalcomponent is a container for a set of other components and properties.
-\layout Subsubsection
-
-Values 
-\layout Standard
-
-Values are represented in a similar way to properties; a base class and
- many 
-\begin_inset Quotes eld
-\end_inset 
-
-derived 
-\begin_inset Quotes eld
-\end_inset 
-
- classes.
- A value is essentially a abstract handle on a single fundamental type,
- a structure or a union.
- 
-\layout Subsubsection
-
-Parameters 
-\layout Standard
-
-Parameters are represetned in a similar way to properties, except that they
- contain only one value
-\layout Subsection
-
-Other elements of libical
-\layout Standard
-
-In addition to the core iCal classes, libical has many other types, structures,
- classes that aid in creating and using iCal components.
- 
-\layout Subsubsection
-
-Enumerations and types
-\layout Standard
-
-Libical is strongly typed, soo every component, property, parameter, and
- value type has an enumeration, and some have an associated structure or
- union.
- 
-\layout Subsubsection
-
-The parser
-\layout Standard
-
-The libical parser offers a variety of ways to convert RFC2445 text into
- a libical iinsteral component structure.
- the parser can parse blocks of text as a string, or it can parse lin-by-line.
-\layout Subsubsection
-
-Error objects
-\layout Standard
-
-Libical has a substantial error reporting system for both programming errors
- and component usage errors.
- 
-\layout Subsubsection
-
-Memory Management
-\layout Standard
-
-Since many of libicals interfaces return strings, the library has its own
- memory management system to elimiate the need to free every string returned
- from the libraru.
- 
-\layout Subsubsection
-
-Storage classes
-\layout Standard
-
-The library also offers several classes to store components to flies, memory
- or databases.
- 
-\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 key 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.
- For instanace, the timezone properties associated with daylight savings
- time 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,this grouping is represented by the
- XDAYLIGHT component.
- Standard iCAL components all start with the letter 
-\begin_inset Quotes eld
-\end_inset 
-
-V,
-\begin_inset Quotes erd
-\end_inset 
-
- while pseudo components start with
-\begin_inset Quotes erd
-\end_inset 
-
-X.
-\begin_inset Quotes erd
-\end_inset 
-
-
-\layout Standard
-
-There are also pseudo components that are conceptually derived classes 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 cumbersome 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 Verbatim
-
-CATEGORIES: work, home
-\layout Standard
-
-becomes in libical's internal representation
-\layout Verbatim
-
-CATEGORIES: work
-\layout Verbatim
-
-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
-
-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 separately
- and then assemble them in to components: 
-\layout Verbatim
-
-icalcomponent *event;
-\layout Verbatim
-
-icalproperty *prop;
-\layout Verbatim
-
-icalparameter *param;
-\layout Verbatim
-
-struct icaltimetype atime;
-\layout Verbatim
-
-event = icalcomponent_new(ICAL_VEVENT_COMPONENT);
-\layout Verbatim
-
-prop = icalproperty_new_dtstamp(atime) ;
-\layout Verbatim
-
-icalcomponent_add_property(event, prop);
-\layout Verbatim
-
-prop = icalproperty_new_uid(''guid-1.host1.com'') );
-\layout Verbatim
-
-icalcomponent_add_property(event,prop);
-\layout Verbatim
-
-prop=icalproperty_new_organizer(''mrbig@host.com''); 
-\layout Verbatim
-
-param = icalparameter_new_role(ICAL_ROLE_CHAIR) 
-\layout Verbatim
-
-icalproperty_add_parameter(prop, param);
-\layout Verbatim
-
-icalcomponent_add_property(event,prop);
-\layout Standard
-
-Notice that libical uses a semi-object-oriented style of interface.
- Most things you work with are objects, that are instantiated with a constructor
- that has 
-\begin_inset Quotes eld
-\end_inset 
-
-new
-\begin_inset Quotes erd
-\end_inset 
-
- in the name.
- Also note that, other than the object reference, most structure data is
- passed in to libical routines by value.
- Libical has some complex but very regular memory handling rules.
- These are detailed in section 
-\begin_inset LatexCommand \ref{sec:memory}
-
-\end_inset 
-
-.
-\layout Standard
-
-If any of the constructors fail, they will return 0.
- If you try to insert 0 into a property or component, or use a zero-valued
- object reference, libical will either silently ignore the error or will
- abort with an error message.
- This behavior is controlled by a compile time flag (ICAL_ERRORS_ARE_FATAL),
- and will abort by default.
- 
-\layout Subsubsection
-
-vaargs Constructors 
-\layout Standard
-
-There is another way to create complex components, which is arguably more
- elegant, if you are not horrified by varargs.
- The varargs constructor interface allows you to create intricate components
- in a single block of code.
- Here is the previous examples in the vaargs style.
- 
-\layout Verbatim
-
-    calendar = 
-\layout Verbatim
-
-        icalcomponent_vanew(
-\layout Verbatim
-
-            ICAL_VCALENDAR_COMPONENT,
-\layout Verbatim
-
-            icalproperty_new_version(''2.0''),
-\layout Verbatim
-
-            icalproperty_new_prodid(
-\layout Verbatim
-
-                 ''-//RDU Software//NONSGML HandCal//EN''),
-\layout Verbatim
-
-            icalcomponent_vanew(
-\layout Verbatim
-
-                ICAL_VEVENT_COMPONENT,
-\layout Verbatim
-
-                icalproperty_new_dtstamp(atime),
-\layout Verbatim
-
-                icalproperty_new_uid(''guid-1.host1.com''),
-\layout Verbatim
-
-                icalproperty_vanew_organizer(
-\layout Verbatim
-
-                    ''mrbig@host.com''),
-\layout Verbatim
-
-                    icalparameter_new_role(ICAL_ROLE_CHAIR),
-\layout Verbatim
-
-                    0
-\layout Verbatim
-
-                    ),
-\layout Verbatim
-
-                icalproperty_vanew_attendee(
-\layout Verbatim
-
-                    ''employee-A@host.com'',
-\layout Verbatim
-
-                    icalparameter_new_role(
-\layout Verbatim
-
-                        ICAL_ROLE_REQPARTICIPANT),
-\layout Verbatim
-
-                    icalparameter_new_rsvp(1),
-\layout Verbatim
-
-                    icalparameter_new_cutype(ICAL_CUTYPE_GROUP),
-\layout Verbatim
-
-                    0
-\layout Verbatim
-
-                    ),
-\layout Verbatim
-
-                icalproperty_new_location(
-\layout Verbatim
-
-                   "1CP Conference Room 4350"),
-\layout Verbatim
-
-                0
-\layout Verbatim
-
-                ),
-\layout Verbatim
-
-            0
-\layout Verbatim
-
-            );
-\layout Standard
-
-This form is similar to the constructor form , except that the constructors
- have 
-\begin_inset Quotes eld
-\end_inset 
-
-vanew
-\begin_inset Quotes erd
-\end_inset 
-
- instead of 
-\begin_inset Quotes eld
-\end_inset 
-
-new
-\begin_inset Quotes erd
-\end_inset 
-
- in the name.
- The arguments are similar too, except that the component constructor can
- have a list of properties, and the property constructor can have a list
- of parameters.
- Be sure to terminate every list with a '0', or your code will crash, if
- you are lucky.
- 
-\layout Subsubsection
-
-Parsing Text Files 
-\layout Standard
-
-The final way to create components will probably be the most common; you
- can create components from RFC2445 compliant text.
- If you have the string in memory, use
-\layout Verbatim
-
-icalcomponent* icalparser_parse_string(char* str);
-\layout Standard
-
-If the string contains only one component, the parser will return the component
- in libical form.
- If the string contains multiple components, the multiple components will
- be returned as the children of an ICAL_XROOT_COMPONENT component.
- 
-\layout Standard
-
-Parsing a whole string may seem wasteful if you want to pull a large component
- off of the network or from a file; you may prefer to parse the component
- line by line.
- This is possible too by using:
-\layout Verbatim
-
-icalparser* icalparser_new(); 
-\layout Verbatim
-
-void icalparser_free(icalparser* parser);
-\layout Verbatim
-
-icalparser_get_line(parser,read_stream);
-\layout Verbatim
-
-icalparser_add_line(parser,line);
-\layout Verbatim
-
-icalparser_set_gen_data(parser,stream)
-\layout Standard
-
-These routines will construct a parser object to which you can add lines
- of input and retrieve any components that the parser creates from the input.
- These routines work by specifing an adaptor routine to get string data
- from a source.
- For an example:
-\layout Verbatim
-
-char* read_stream(char *s, size_t size, void *d) 
-\layout Verbatim
-
-{ 
-\layout Verbatim
-
-  char *c = fgets(s,size, (FILE*)d);
-\layout Verbatim
-
-  return c;
-\layout Verbatim
-
-}
-\layout Verbatim
-
-main() {
-\layout Verbatim
-
-  char* line; 
-\layout Verbatim
-
-  icalcomponent *c; 
-\layout Verbatim
-
-  icalparser *parser = icalparser_new();
-\layout Verbatim
-
-  FILE* stream = fopen(argv[1],"r");
-\layout Verbatim
-
-  icalparser_set_gen_data(parser,stream);
-\layout Verbatim
-
-  do{ 
-\layout Verbatim
-
-    line = icalparser_get_line(parser,read_stream); 
-\layout Verbatim
-
-    c = icalparser_add_line(parser,line);
-\layout Verbatim
-
-    if (c != 0){ 
-\layout Verbatim
-
-     printf("%s",icalcomponent_as_ical_string(c));     
-\layout Verbatim
-
-     icalparser_claim(parser); 
-\layout Verbatim
-
-     printf("
-\backslash 
-n---------------
-\backslash 
-n"); 
-\layout Verbatim
-
-     icalcomponent_free(c); 
-\layout Verbatim
-
-   }
-\layout Verbatim
-
-  } while ( line != 0);
-\layout Verbatim
-
-}
-\layout Standard
-
-The parser object parameterizes the routine used to get input lines with
- icalparser_set_gen_data() and
-\emph on 
- 
-\emph default 
-icalparser_get_line().
- In this example, the routine read_stream() will fetch the next line from
- a stream, with the stream passed in as the void* parameter d.
- The parser calls read_stream() from icalparser_get_line(), but it also
- needs to know what stream to use.
- This is set by the call to icalparser_set_gen_data().
- By using a different routine for read_stream or passing in different data
- with icalparser_set_gen_data, you can connect to any data source.
- 
-\layout Standard
-
-Using the same mechanism, other implementations could read from memory buffers,
- sockets or other interfaces.
- 
-\layout Standard
-
-Since the example code is a very common way to use the parser, there is
- a convenience routine;
-\layout Verbatim
-
-icalcomponent* icalparser_parse(icalparser *parser, 
-\layout Verbatim
-
-               char* (*line_gen_func)(char *s, size_t size,  void* d))
-\layout Standard
-
-To use this routine, you still must construct the parser object and pass
- in a reference to a line reading routine.
- If the parser can create a single component from the input, it will return
- a pointer to the newly constructed component.
- If the parser can construct multiple components from the input, it will
- return a reference to an XROOT component ( of type ICAL_XROOT_COMPONENT.)
- This XROOT component will hold all of the components constructed from the
- input as children.
- 
-\layout Subsection
-
-Accessing Components 
-\layout Standard
-
-Given a reference to a component, you probably will want to access the propertie
-s, parameters and values inside.
- Libical interfaces let you find sub-component, add and remove sub-components,
- and do the same three operations on properties.
- 
-\layout Subsubsection
-
-Finding Components 
-\layout Standard
-
-To find a sub-component of a component, use: 
-\layout Verbatim
-
-icalcomponent* icalcomponent_get_first_component(
-\layout Verbatim
-
-                                   icalcomponent* component, 
-\layout Verbatim
-
-                                   icalcomponent_kind kind);
-\layout Standard
-
-This routine will return a reference to the first component of the type
- 'kind.' The key kind values, listed in icalenums.h are: 
-\layout Verbatim
-
-ICAL_ANY_COMPONENT
-\layout Verbatim
-
-ICAL_VEVENT_COMPONENT
-\layout Verbatim
-
-ICAL_VTODO_COMPONENT
-\layout Verbatim
-
-ICAL_VJOURNAL_COMPONENT
-\layout Verbatim
-
-ICAL_VCALENDAR_COMPONENT 
-\layout Verbatim
-
-ICAL_VFREEBUSY_COMPONENT
-\layout Verbatim
-
-ICAL_VALARM_COMPONENT
-\layout Standard
-
-These are only the most common components; there are many more listed in
- icalenums.h.
-\layout Standard
-
-As you might guess, if there is more than one subcomponent of the type you
- have chosen, this routine will return only the first.
- to get at the others, you need to iterate through the component.
- 
-\layout Subsubsection
-
-Iterating Through Components
-\layout Standard
-
-Iteration requires a second routine to get the next subcomponent after the
- first:
-\layout Verbatim
-
-icalcomponent* icalcomponent_get_next_component(
-\layout Verbatim
-
-               icalcomponent* component, 
-\layout Verbatim
-
-               icalcomponent_kind kind);
-\layout Standard
-
-With the 'first' and 'next' routines, you can create a for loop to iterate
- through all of a components subcomponents
-\layout Verbatim
-
-  for(c = icalcomponent_get_first_component(comp,ICAL_ANY_COMPONENT); 
-\layout Verbatim
-
-         c != 0; 
-\layout Verbatim
-
- c = icalcomponent_get_next_component(comp,ICAL_ANY_COMPONENT))
-\layout Verbatim
-
-{ 
-\layout Verbatim
-
-      do_something(c);
-\layout Verbatim
-
-}
-\layout Standard
-
-This code bit wil iterate through all of the subcomponents in 'comp' but
- you can select a specific type of component by changing ICAL_ANY_COMPONENT
- to another component type.
-\layout Subsubsection
-
-Using Component Iterators
-\layout Standard
-
-The iteration model in the previous section requires the component to keep
- the state of the iteration.
- So, you could not use this model to perform a sorting operations, since
- you'd need two iterators and there is only space for one.
- If you ever call icalcomponent_get_first_component() when an iteration
- is in progress, the pointer will be reset to the beginning.
- 
-\layout Standard
-
-To solve this problem, there are also external iterators for components.
- The routines associated with these external iterators are: 
-\layout Verbatim
-
-icalcompiter icalcomponent_begin_component(icalcomponent* component, icalcompone
-nt_kind kind);
-\layout Verbatim
-
-icalcompiter icalcomponent_end_component(icalcomponent* component, icalcomponent
-_kind kind);
-\layout Verbatim
-
-icalcomponent* icalcompiter_next(icalcompiter* i); 
-\layout Verbatim
-
-icalcomponent* icalcompiter_prior(icalcompiter* i); 
-\layout Verbatim
-
-icalcomponent* icalcompiter_deref(icalcompiter* i);
-\layout Standard
-
-The _begin_() and _end_() routines return a new iterator that points to
- the beginning and ending of the list of subcomponent for the given component,
- and the kind argument works like the kind argument for internal iterators.
- 
-\layout Standard
-
-After creating an iterators, use _next_() and _prior_() to step forward
- and backward through the list and get the component that the iterator points
- to, and use _deref() to return the component that the iterator points to
- without moving the iterator.
- All routines will return 0 when they move to point off the end of the list.
- 
-\layout Standard
-
-Here is an example of a loop using these routines: 
-\layout Verbatim
-
-for(
-\layout Verbatim
-
-   i = icalcomponent_begin_component(impl->cluster,ICAL_ANY_COMPONENT);
- 
-\layout Verbatim
-
-   icalcompiter_deref(&i)!= 0; 
-\layout Verbatim
-
-   icalcompiter_next(&i)
-\layout Verbatim
-
-) { 
-\layout Verbatim
-
-      icalcomponent *this = icalcompiter_deref(&i);
-\layout Verbatim
-
-}
-\layout Subsubsection
-
-Removing Components 
-\layout Standard
-
-Removing an element from a list while iterating through the list with the
- internal iterators can cause problems, since you will probably be removing
- the element that the internal iterator points to.
- The _remove() routine will keep the iterator valid by moving it to the
- next component, but in a normal loop, this will result in two advances
- per iteration, and you will remove only every other component.
-  To avoid the problem, you will need to step the iterator ahead of the
- element you are going to remove, like this:
-\layout Verbatim
-
-for(c = icalcomponent_get_first_component(parent_comp,ICAL_ANY_COMPONENT);
- 
-\layout Verbatim
-
-       c != 0; 
-\layout Verbatim
-
-       c = next
-\layout Verbatim
-
-{     
-\layout Verbatim
-
-    next = icalcomponent_get_next_component(parent_comp,ICAL_ANY_COMPONENT);
-\layout Verbatim
-
-    icalcomponent_remove_component(parent_comp,c); 
-\layout Verbatim
-
-}
-\layout Standard
-
-Another way to remove components is to rely on the side effect of icalcomponent_
-remove_component: if component iterator in the parent component is pointing
- to the child that will be removed, it will move the iterator to the component
- after the child.
- The following code will exploit this behavior: 
-\layout Verbatim
-
-icalcomponent_get_first_component(parent_comp,ICAL_VEVENT_COMPONENT);
-\layout Verbatim
-
-while((c=icalcomponent_get_current_component(c)) != 0 ){ 
-\layout Verbatim
-
-   if(icalcomponent_isa(c) == ICAL_VEVENT_COMPONENT){ 
-\layout Verbatim
-
-      icalcomponent_remove_component(parent_comp,inner);
-\layout Verbatim
-
-   } else { 
-\layout Verbatim
-
-      icalcomponent_get_next_component(parent_comp,ICAL_VEVENT_COMPONENT);
- 
-\layout Verbatim
-
-   } 
-\layout Verbatim
-
-}
-\layout Subsubsection
-
-Working with properties and parameters
-\layout Standard
-
-Finding, iterating and removing properties works the same as it does for
- components, using the property-specific or parameter-specific interfaces:
- 
-\layout Verbatim
-
-icalproperty* icalcomponent_get_first_property(
-\layout Verbatim
-
-     icalcomponent* component, 
-\layout Verbatim
-
-     icalproperty_kind kind); 
-\layout Verbatim
-
-icalproperty* icalcomponent_get_next_property(
-\layout Verbatim
-
-     icalcomponent* component, 
-\layout Verbatim
-
-     icalproperty_kind kind);
-\layout Verbatim
-
-void icalcomponent_add_property(
-\layout Verbatim
-
-     icalcomponent* component, 
-\layout Verbatim
-
-     icalproperty* property);
-\layout Verbatim
-
-void icalcomponent_remove_property(
-\layout Verbatim
-
-     icalcomponent* component, 
-\layout Verbatim
-
-     icalproperty* property);
-\layout Standard
-
-For parameters:
-\layout Verbatim
-
-icalparameter* icalproperty_get_first_parameter(
-\layout Verbatim
-
-     icalproperty* prop, 
-\layout Verbatim
-
-     icalparameter_kind kind); 
-\layout Verbatim
-
-icalparameter* icalproperty_get_next_parameter(
-\layout Verbatim
-
-     icalproperty* prop, 
-\layout Verbatim
-
-     icalparameter_kind kind);
-\layout Verbatim
-
-void icalproperty_add_parameter(
-\layout Verbatim
-
-     icalproperty* prop,
-\layout Verbatim
-
-     icalparameter* parameter);
-\layout Verbatim
-
-void icalproperty_remove_parameter(
-\layout Verbatim
-
-     icalproperty* prop, 
-\layout Verbatim
-
-     icalparameter_kind kind);
-\layout Standard
-
-Note that since there should be only one parameter of each type in a property,
- you will rarely need to use icalparameter_get_nect_paameter.
-\layout Subsubsection
-
-Working with values
-\layout Standard
-
-Values are typically part of a property, although they can exist on their
- own.
- You can manipulate them either as part of the property or independently.
-\layout Standard
-
-The most common way to work with values to is to manipulate them from they
- properties that contain them.
- This involves fewer routine calls and intermediate variables than working
- with them independently, and it is type-safe.
- 
-\layout Standard
-
-For each property, there are a _get_ and a _set_ routine that access the
- internal value.
- For instanace, for the UID property, the routines are: 
-\layout Verbatim
-
-void icalproperty_set_uid(icalproperty* prop, const char* v)
-\layout Verbatim
-
-const char* icalproperty_get_uid(icalproperty* prop)
-\layout Standard
-
-For multi-valued properties, like ATTACH, the value type is usually a struct
- or union that holds both possible types.
- 
-\layout Standard
-
-If you want to work with the underlying value object, you can get and set
- it with:
-\layout Verbatim
-
-icalvalue* icalproperty_get_value (icalproperty* prop)
-\layout Verbatim
-
-void icalproperty_set_value(icalproperty* prop, icalvalue* value);
-\layout Standard
-
-Icalproperty_get_value() will return a reference that you can manipulate
- with other icalvalue routines.
- Most of the time, you will have to know what the type of the value is.
- For instance, if you know that the value is a DATETIME type, you can manipulate
- it with: 
-\layout Verbatim
-
-struct icaltimetype icalvalue_get_datetime(icalvalue* value); 
-\layout Verbatim
-
-void icalvalue_set_datetime(icalvalue* value, struct icaltimetype v);
-\layout Standard
-
-When working with an extension property or value (and X-PROPERTY or a property
- that has the parameter VALUE=x-name ) the value type is always a string.
- To get and set the value, use: 
-\layout Verbatim
-
-void icalproperty_set_x(icalproperty* prop, char* v); 
-\layout Verbatim
-
-char* icalproperty_get_x(icalproperty* prop);
-\layout Standard
-
-All X properties have the type of ICAL_X_PROPERTY, so you will need these
- routines to get and set the name of the property:
-\layout Verbatim
-
-char* icalproperty_get_x_name(icalproperty* prop)
-\layout Verbatim
-
-void icalproperty_set_x_name(icalproperty* prop, char* name);
-\layout Subsubsection
-
-Checking Component Validity
-\layout Standard
-
-RFC 2446 defines rules for what properties must exist in a component to
- be used for transferring scheduling data.
- Most of these rules relate to the existence of properties relative to the
- METHOD property, which declares what operation a remote receiver should
- use to process a component.
- For instance, if the METHOD is REQUEST and the component is a VEVENT, the
- sender is probably asking the receiver to join in a meeting.
- In this case, RFC2446 says that the component must specify a start time
- (DTSTART) and list the receiver as an attendee (ATTENDEE).
- 
-\layout Standard
-
-Libical can check these restrictions with the routine:
-\layout Verbatim
-
-int icalrestriction_check(icalcomponent* comp);
-\layout Standard
-
-This routine returns 0 if the component does not pass RFC2446 restrictions,
- or if the component is malformed.
- The component you pass in 
-\emph on 
-must
-\emph default 
- be a VCALENDAR, with one or more children, like the examples in RFC2446.
- 
-\layout Standard
-
-When this routine runs, it will insert new properties into the component
- to indicate any errors it finds.
- See section 6.5.3, X-LIC-ERROR for more information about these error properties.
- 
-\layout Subsubsection
-
-Converting Components to Text
-\layout Standard
-
-To create an RFC2445 compliant text representation of an object, use one
- of the *_as_ical_string() routines:
-\layout Verbatim
-
-char* icalcomponent_as_ical_string (icalcomponent* component)
-\layout Verbatim
-
-char* icalproperty_as_ical_string (icalproperty* property)
-\layout Verbatim
-
-char* icalparameter_as_ical_string (icalparameter* parameter)
-\layout Verbatim
-
-char* icalvalue_as_ical_string (icalvalue* value)
-\layout Standard
-
-In most cases, you will only use icalcomponent_as_ical_string (), since
- it will cascade and convert all of the parameters, properties and values
- that are attached to the root component.
-\layout Standard
-
-Icalproperty_as_ical_string() will terminate each line with the RFC2445
- specified line terminator 
-\begin_inset Quotes eld
-\end_inset 
-
-
-\backslash 
-
-\backslash 
-n
-\begin_inset Quotes erd
-\end_inset 
-
- However, if you compile with the symbol ICAL_UNIX_NEWLINE undefined, (
- it is defined by default) it will terminate lines with 
-\begin_inset Quotes eld
-\end_inset 
-
-
-\backslash 
-
-\backslash 
-n
-\backslash 
-
-\backslash 
-r
-\begin_inset Quotes erd
-\end_inset 
-
-
-\layout Standard
-
-Remember that the string returned by these routines is owned by the library,
- and will eventually be re-written.
- You should copy it if you want to preserve it.
- 
-\layout Subsection
-
-Time
-\layout Subsubsection
-
-Time structure
-\layout Standard
-
-LIbical defines it's own time structure for storing all dates and times.
- It would have been nice to re-use the C library's 
-\emph on 
-struct tm, 
-\emph default 
-but that structure does not differentiate between dates and times, and between
- local time and UTC.
- The libical structure is:
-\layout Verbatim
-
-struct icaltimetype { 
-\layout Verbatim
-
-  int year; 
-\layout Verbatim
-
-  int month; 
-\layout Verbatim
-
-  int day; 
-\layout Verbatim
-
-  int hour; 
-\layout Verbatim
-
-  int minute; 
-\layout Verbatim
-
-  int second;
-\layout Verbatim
-
-  int is_utc; /* 1-> time is in UTC timezone */
-\layout Verbatim
-
-  int is_date; /* 1 -> interpret this as date.
- */ }; 
-\layout Standard
-
-The year, month, day, hour, minute and second fields hold the broken-out
- time values.
- The is_utc field distinguishes between times in UTC and a local time zone.
- The is_date field indicates if the time should be interpreted only as a
- date.
- If it is a date, the hour, minute and second fields are assumed to be zero,
- regardless of their actual vaules.
- 
-\layout Subsubsection
-
-Creating time structures
-\layout Standard
-
-There are several ways to create a new icaltimetype structure: 
-\layout Verbatim
-
-struct icaltimetype icaltime_from_string(const char* str);
-\layout Verbatim
-
-struct icaltimetype icaltime_from_timet(time_t v, int is_date);
-\layout Verbatim
-
-struct icaltimetype icaltime_from_int(int v, int is_date, int is_utc);
-\layout Standard
-
-Icaltime_from_string takes any RFC2445 compliant time string: 
-\layout Verbatim
-
-struct icaltimetype tt = icaltime_from_string("19970101T103000");
-\layout Standard
-
-Icaltime_from_timet takes a timet value, representing seconds past the POSIX
- epoch, and a flag to indicate if the time is a date.
- Dates have an identical structure to a time, but the time portion ( hours,
- minuts and seconds ) is always 00:00:00.
- Dates act differently in sorting an comparision, and they have a different
- string representation in RFC2445.
- 
-\layout Standard
-
-The icaltime_from_int is like icaltime_from_timet, but with an arbitrary
- epoch.
- This routine was a mistake and is deprecated.
- 
-\layout Subsubsection
-
-Time manipulating routines
-\layout Standard
-
-The null time value is used to indicate that the data in the structure is
- not a valid time.
-\layout Verbatim
-
-struct icaltimetype icaltime_null_time(void);
-\layout Verbatim
-
-int icaltime_is_null_time(struct icaltimetype t);
-\layout Standard
-
-It is sensible for the broken-out time fields to contain values that are
- not permitted in an ISO compliant time string.
- For instance, the seconds field can hold values greater than 59, and the
- hours field can hold values larger than 24.
- The excessive values will be rolled over into the next larger field when
- the structure is normalized.
- 
-\layout Verbatim
-
-struct icaltimetype icaltime_normalize(struct icaltimetype t);
-\layout Standard
-
-Normalizing allows you to do arithmetic operations on time values.
- 
-\layout Verbatim
-
-struct icaltimetype tt = icaltime_from_string(
-\begin_inset Quotes eld
-\end_inset 
-
-19970101T103000
-\begin_inset Quotes erd
-\end_inset 
-
-);
-\layout Verbatim
-
-tt.days +=3 
-\layout Verbatim
-
-tt.second += 70;
-\layout Verbatim
-
-tt = icaltime_normalize(tt);
-\layout Standard
-
-There are several routines to get the day of the week or month, etc, from
- a time structure.
-\layout Verbatim
-
-short icaltime_day_of_year(struct icaltimetype t); 
-\layout Verbatim
-
-struct icaltimetype icaltime_from_day_of_year(short doy, short year);
-\layout Verbatim
-
-short icaltime_day_of_week(struct icaltimetype t); 
-\layout Verbatim
-
-short icaltime_start_doy_of_week(struct icaltimetype t);
-\layout Verbatim
-
-short icaltime_week_number(short day_of_month, short month, short year);
-\layout Verbatim
-
-struct icaltimetype icaltime_from_week_number(short week_number, short year);
-\layout Verbatim
-
-short icaltime_days_in_month(short month,short year);
-\layout Standard
-
-Two routines convert time structures to and from the number of seconds since
- the POSIX epoch.
- The is_date field indicates whether or not the hour, minute and second
- fields should be used in the conversion.
-\layout Verbatim
-
-struct icaltimetype icaltime_from_timet(time_t v, int is_date); 
-\layout Verbatim
-
-time_t icaltime_as_timet(struct icaltimetype);
-\layout Standard
-
-The compare routine works exactly like strcmp, but on time structures.
- 
-\layout Verbatim
-
-int icaltime_compare(struct icaltimetype a,struct icaltimetype b);
-\layout Standard
-
-The following routines convert between UTC and a named timezone.
- The tzid field must be a timezone name from the Olsen database, such as
- 
-\begin_inset Quotes eld
-\end_inset 
-
-America/Los_Angeles.
-\begin_inset Quotes erd
-\end_inset 
-
- 
-\layout Standard
-
-The utc_offset routine returns the offset of the named time zone from UTC,
- in seconds.
- 
-\layout Standard
-
-The tt parameter in the following routines indicates the date on which the
- conversion should be made.
- The tt parameter is necessary because timezones have many different rules
- for when daylight savings time is used, and these rules can change over
- time.
- So, for a single timezone one year may have daylight savings time on March
- 15, but for other years March 15 may be standard time, and some years may
- have standard time all year.
- 
-\layout Verbatim
-
-int icaltime_utc_offset(struct icaltimetype tt, char* tzid);
-\layout Verbatim
-
-int icaltime_local_utc_offset();
-\layout Verbatim
-
-struct icaltimetype icaltime_as_utc(struct icaltimetype tt,char* tzid);
-\layout Verbatim
-
-struct icaltimetype icaltime_as_zone(struct icaltimetype tt,char* tzid);
-\layout Verbatim
-
-struct icaltimetype icaltime_as_local(struct icaltimetype tt);
-\layout Subsection
-
-Storing Objects
-\layout Standard
-
-The libical distribution includes a separate library, libicalss, that allows
- you to store iCal component data to disk in a variety of ways.
- This library also includes code to implement the CSTP protocol of CAP and
- has some routines for deciphering incomming messages.
- 
-\layout Standard
-
-The file storage routines are organized in an inheritance heirarchy that
- is rooted in icalset, with the derived class icalfileset and icaldirset.
- Icalfileset stores components to a file, while icaldirset stores components
- to multiple files, one per month based on DTSTAMP.
- Other storages classess, for storage to a heap or a mysql database are
- planned for the future.
- 
-\layout Standard
-
-All of the icalset derived classes have the same interface: 
-\layout Verbatim
-
-\layout Verbatim
-
-icaldirset* icaldirset_new(const char* path);
-\layout Verbatim
-
-void icaldirset_free(icaldirset* store);
-\layout Verbatim
-
-const char* icaldirset_path(icaldirset* store);
-\layout Verbatim
-
-void icaldirset_mark(icaldirset* store);
-\layout Verbatim
-
-icalerrorenum icaldirset_commit(icaldirset* store); 
-\layout Verbatim
-
-icalerrorenum icaldirset_add_component(icaldirset* store, icalcomponent*
- comp);
-\layout Verbatim
-
-icalerrorenum icaldirset_remove_component(icaldirset* store, icalcomponent*
- comp);
-\layout Verbatim
-
-int icaldirset_count_components(icaldirset* store, icalcomponent_kind kind);
-\layout Verbatim
-
-icalerrorenum icaldirset_select(icaldirset* store, icalcomponent* gauge);
-\layout Verbatim
-
-void icaldirset_clear(icaldirset* store);
-\layout Verbatim
-
-icalcomponent* icaldirset_fetch(icaldirset* store, const char* uid);
-\layout Verbatim
-
-int icaldirset_has_uid(icaldirset* store, const char* uid);
-\layout Verbatim
-
-icalcomponent* icaldirset_fetch_match(icaldirset* set, icalcomponent *c);
-\layout Verbatim
-
-icalerrorenum icaldirset_modify(icaldirset* store, icalcomponent *oldc,
- icalcomponent *newc);
-\layout Verbatim
-
-icalcomponent* icaldirset_get_current_component(icaldirset* store);
-\layout Verbatim
-
-icalcomponent* icaldirset_get_first_component(icaldirset* store);
-\layout Verbatim
-
-icalcomponent* icaldirset_get_next_component(icaldirset* store);
-\layout Subsubsection
-
-Creating a new set
-\layout Standard
-
-You can create a new set from either the base class or the direved class.
- From the base class use one of:
-\layout Verbatim
-
-icalset* icalset_new_file(const char* path); 
-\layout Verbatim
-
-icalset* icalset_new_dir(const char* path); 
-\layout Verbatim
-
-icalset* icalset_new_heap(void); 
-\layout Verbatim
-
-icalset* icalset_new_mysql(const char* path);
-\layout Standard
-
-You can also create a new set based on the derived class, For instance,
- with icalfileset: 
-\layout Verbatim
-
-icalfileset* icalfileset_new(const char* path);
-\layout Verbatim
-
-icalfileset* icalfileset_new_open(const char* path, int flags, mode_t mode);
-\layout Standard
-
-Icaset_new_file is identical to icalfileset_new.
- BOth routines will open an existing file for readinga and writing, or create
- a new file if it does not exist.
- Icalfilset_new_open takes the same arguments as the open() system routine
- and behaves in the same way.
- 
-\layout Standard
-
-The icalset and icalfilset objects are somewhat interchangable -- you can
- use an icalfileset* as an argument to any of the icalset routines.
-\layout Standard
-
-The following examples will all use icalfileset routines; using the other
- icalset derived classess will be similar.
- 
-\layout Subsubsection
-
-Adding, Finding and Removing Components 
-\layout Standard
-
-To add components to a set, use: 
-\layout Verbatim
-
-icalerrorenum icalfileset_add_component(icalfileset* cluster, icalcomponent*
- child);
-\layout Standard
-
-The fileset keeps an inmemory copy of the components, and this set must
- be written back to the file ocassionally.
- There are two routines to manage this: 
-\layout Verbatim
-
-void icalfileset_mark(icalfileset* cluster); 
-\layout Verbatim
-
-icalerrorenum icalfileset_commit(icalfileset* cluster);
-\layout Standard
-
-Icalfileset_mark indicates that the in-memory components have changed.
- Calling the _add_component routine will call _mark automatically, but you
- may need to call it yourself if you have made a change to an existing component.
- The _commit routine writes the data base to disk, but only if it is marked.
- The _commit routine is called automatically when the icalfileset is freed.
- 
-\layout Standard
-
-To iterate through the components in a set, use: 
-\layout Verbatim
-
-icalcomponent* icalfileset_get_first_component(icalfileset* cluster); 
-\layout Verbatim
-
-icalcomponent* icalfileset_get_next_component(icalfileset* cluster);
-\layout Verbatim
-
-icalcomponent* icalfileset_get_current_component (icalfileset* cluster);
-  
-\layout Standard
-
-These routines work like the corresponding routines from icalcomponent,
- except that their output is filtered through a gauge.
- A gauge is a test for the properties within a components; only components
- that pass the test are returned.
- A gauge can be constructed from a MINSQL string with:
-\layout Verbatim
-
-icalgauge* icalgauge_new_from_sql(char* sql);
-\layout Standard
-
-Then, you can add the gauge to the set with : 
-\layout Verbatim
-
-icalerrorenum icalfileset_select(icalfileset* store, icalgauge* gauge);
-\layout Standard
-
-Here is an example that puts all of these routines together: 
-\layout Verbatim
-
-
-\latex no_latex 
-void test_fileset()
-\layout Verbatim
-
-
-\latex no_latex 
-{
-\layout Verbatim
-
-
-\latex no_latex 
-    icalfileset *fs;
-\layout Verbatim
-
-
-\latex no_latex 
-    icalcomponent *c;
-\layout Verbatim
-
-
-\latex no_latex 
-    int i;
-\layout Verbatim
-
-
-\latex no_latex 
-    char *path = "test_fileset.ics";
-\layout Verbatim
-
-
-\latex no_latex 
-    icalgauge  *g = icalgauge_new_from_sql(
-\layout Verbatim
-
-
-\latex no_latex 
-        "SELECT * FROM VEVENT WHERE DTSTART > '20000103T120000Z' AND DTSTART
- <= '20000106T120000Z'");
-\layout Verbatim
-
-
-\latex no_latex 
- 
-\layout Verbatim
-
-    
-\latex no_latex 
-fs = icalfileset_new(path);
-\layout Verbatim
-
-  
-\layout Verbatim
-
-    
-\latex no_latex 
-for (i = 0; i!= 10; i++){
-\layout Verbatim
-
-
-\latex no_latex 
-        c = make_component(i);
-\latex default 
- /* Make a new component where DTSTART has month of i */
-\layout Verbatim
-
-
-\latex no_latex 
-        icalfileset_add_component(fs,c);
-\layout Verbatim
-
-
-\latex no_latex 
-    }
-\layout Verbatim
-
-\layout Verbatim
-
-
-\latex no_latex 
-    icalfileset_commit(fs);
-\latex default 
- /* Write to disk */
-\layout Verbatim
-
-\layout Verbatim
-
-
-\latex no_latex 
-    icalfileset_select(fs,g);
-\latex default 
- /* Set the gauge to filter components */
-\layout Verbatim
-
-
-\latex no_latex 
- 
-\layout Verbatim
-
-
-\latex no_latex 
-    for (c = icalfileset_get_first_component(fs);
-\layout Verbatim
-
-
-\latex no_latex 
-         c != 0;
-\layout Verbatim
-
-
-\latex no_latex 
-         c = icalfileset_get_next_component(fs)){
-\layout Verbatim
-
-
-\latex no_latex 
-        struct icaltimetype t = icalcomponent_get_dtstart(c);
-\layout Verbatim
-
-
-\latex no_latex 
- 
-\layout Verbatim
-
-
-\latex no_latex 
-        printf("%s
-\backslash 
-n",icaltime_as_ctime(t));
-\layout Verbatim
-
-
-\latex no_latex 
-    }
-\layout Verbatim
-
-    
-\latex no_latex 
-icalfileset_free(fs);
-\layout Verbatim
-
-
-\latex no_latex 
-}
-\layout Subsubsection
-
-Other routines
-\layout Standard
-
-There are several other routines in the icalset interface, but they not
- fully implemented yet.
- 
-\layout Subsection
-
-
-\begin_inset LatexCommand \label{sec:memory}
-
-\end_inset 
-
-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 transferring 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.
- For example, icalcomponent_as_ical_string().
- 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
-
-Libical has several error handling mechanisms for the various types of programmi
-ng, semantic and syntactic errors you may encounter.
-\layout Subsubsection
-
-Return values
-\layout Standard
-
-Many library routines signal errors through their return values.
- All routines that return a pointer, such as icalcomponent_new(), will return
- 0 ( zero ) on a fatal error.
- Some routines will return a value of enum icalerrorenum.
- 
-\layout Subsubsection
-
-icalerrno
-\layout Standard
-
-Most routines will set the global error value icalerrno on errors.
- This variable is an enumeration; permissible values can be found in libical/ica
-lerror.h.
- If the routine returns an enum icalerrorenum, then the return value will
- be the same as icalerrno.
- You can use icalerror_strerror() to get a string that describes the error.
- The enumerations are:
-\layout Itemize
-
-ICAL_BADARG_ERROR -- One of the argument to a routine was bad.
- Typically for a null pointer.
- 
-\layout Itemize
-
-ICAL_NEWFAILED_ERROR -- A new() or malloc() failed
-\layout Itemize
-
-ICAL_MALFORMEDDATA_ERROR -- An input string was not in the correct format
-\layout Itemize
-
-ICAL_PARSE_ERROR -- The parser failed to parse an incomming component
-\layout Itemize
-
-ICAL_INTERNAL_ERROR -- Largely equivalent to an assert
-\layout Itemize
-
-ICAL_FILE_ERROR -- A file operation failed.
- Check errno for more detail.
-\layout Itemize
-
-ICAL_ALLOCATION_ERROR -- ?
-\layout Itemize
-
-ICAL_USAGE_ERROR -- ?
-\layout Itemize
-
-ICAL_NO_ERROR -- No error
-\layout Itemize
-
-ICAL_MULTIPLEINCLUSION_ERROR -- ?
-\layout Itemize
-
-ICAL_TIMEDOUT_ERROR -- For CSTP and acquiring locks
-\layout Itemize
-
-ICAL_UNKNOWN_ERROR -- ?
-\layout Subsubsection
-
-X-LIC-ERROR and X-LIC-INVALID-COMPONENT
-\layout Standard
-
-The library handles semantic and syntactic errors in components by inserting
- errors properties into the components.
- If the parser cannot parse incoming text ( a syntactic error ) or if the
- icalrestriction_check() routine indicates that the component does not meet
- the requirements of RFC2446 ( a semantic error) the library will insert
- properties of the type X-LIC-ERROR to describe the error.
- Here is an example of the error property: 
-\layout Verbatim
-
-X-LIC-ERROR;X-LIC-ERRORTYPE=INVALID_ITIP :Failed iTIP restrictions for property
- DTSTART.
- 
-\layout Verbatim
-
-Expected 1 instances of the property and got 0 
-\layout Standard
-
-This error resulted from a call to icalrestriction_check(), which discovered
- that the component does not have a DTSTART property, as required by RFC2445.
- 
-\layout Standard
-
-There are a few routines to manipulate error properties:
-\layout Standard
-
-[ The following data is supposed to be in a table.
- It looks OK in LyX, but does not format propertly in output.
- ]
-\layout Standard
-\LyXTable
-multicol5
-10 2 0 0 -1 -1 -1 -1
-1 1 0 0
-1 0 0 0
-0 1 1 0
-1 0 0 0
-0 1 1 0
-1 1 0 0
-0 1 1 0
-1 1 0 0
-0 1 1 0
-0 1 1 0
-2 1 0 "" ""
-2 1 1 "3in" ""
-0 2 1 1 0 0 0 "" ""
-0 8 1 0 0 0 0 "" ""
-0 2 1 0 0 0 0 "" ""
-0 2 1 0 1 0 1 "" ""
-0 2 1 0 0 0 0 "" ""
-0 2 1 0 0 0 1 "" ""
-0 2 1 0 0 0 0 "" ""
-0 2 1 0 1 0 0 "" ""
-0 2 1 0 0 0 0 "" ""
-0 2 1 0 0 0 0 "" ""
-0 2 1 0 0 0 0 "" ""
-0 2 1 0 1 0 0 "" ""
-0 2 1 0 0 0 0 "" ""
-0 2 1 0 0 0 0 "" ""
-0 2 1 0 0 0 0 "" ""
-0 2 1 1 1 0 1 "" ""
-0 2 1 0 0 0 0 "" ""
-0 2 1 1 1 0 1 "" ""
-0 2 1 0 0 0 0 "" ""
-0 2 1 1 0 0 1 "" ""
-
-Routine
-\newline 
-Purpose
-\newline 
-void icalrestriction_check()
-\newline 
-Check a component against RFC2446 and insert
-\newline 
-
-\newline 
-error properties to indicate non compliance
-\newline 
-int icalcomponent_count_errors()
-\newline 
-Return the number of error properties 
-\newline 
-
-\newline 
-in a component
-\newline 
-void icalcomponent_strip_errors()
-\newline 
-Remove all error properties in as
-\newline 
-
-\newline 
-component
-\newline 
-void icalcomponent_convert_errors()
-\newline 
-Convert some error properties into 
-\newline 
-
-\newline 
-REQUESTS-STATUS proprties to indicate the inability to 
-\newline 
-
-\newline 
-process the component as an iTIP request.
- 
-\layout Standard
-
-The types of errors are listed in icalerror.h.
- They are:
-\layout Verbatim
-
-ICAL_XLICERRORTYPE_COMPONENTPARSEERROR
-\layout Verbatim
-
-ICAL_XLICERRORTYPE_PARAMETERVALUEPARSEERROR
-\layout Verbatim
-
-ICAL_XLICERRORTYPE_PARAMETERNAMEPARSEERROR 
-\layout Verbatim
-
-ICAL_XLICERRORTYPE_PROPERTYPARSEERROR
-\layout Verbatim
-
-ICAL_XLICERRORTYPE_VALUEPARSEERROR
-\layout Verbatim
-
-ICAL_XLICERRORTYPE_UNKVCALPROP
-\layout Verbatim
-
-ICAL_XLICERRORTYPE_INVALIDITIP
-\layout Standard
-
-The libical parser will generate the error that end in PARSEERROR when it
- encounters garbage in the input steam.
- ICAL_XLICERRORTYPE_INVALIDITIP is inserted by icalrestriction_check(),
- and ICAL_XLICERRORTYPE_UNKVCALPROP is generated by icalvcal_convert() when
- it encounters a vCal property that it cannot convert or does not know about.
- 
-\layout Standard
-
-Icalcomponent_convert_errors() converts some of the error properties in
- a component into REQUEST-STATUS properties that indicate a failure.
- As of libical version0.18, this routine only convert *PARSEERROR errors
- and it always generates a 3.x ( failure ) code.
- This makes it more of a good idea than a really useful bit of code.
- 
-\layout Subsubsection
-
-ICAL_ERRORS_ARE_FATAL and icalerror_errors_are_fatal
-\layout Standard
-
-If the global variable icalerror_errors_are_fatal is set to 1, then any
- error condition will cause the program to abort.
- The abort occurs in icalerror_set_errno(), and is done with an assert(0)
- if NDEBUG is undefined, and with icalerror_crash_here if NDEBUG is defined.
- The default value of icalerror_errors_are_fatal is 1 when ICAL_ERRORS_ARE_FATAL
- is defined, and 0 otherwise.
- Since ICAL_ERRORS_ARE_FATAL is defined by default, icalerror_errors_are_fatal
- is also defined by default.
- 
-\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 
-
-_PARAMETER
-\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
-
-Hacks and Bugs
-\layout Standard
-
-There are a lot of hacks in the library -- bits of code that I am not proud
- of and should probably be changed.
- These are marked with the comment string 
-\begin_inset Quotes eld
-\end_inset 
-
-HACK.
-\begin_inset Quotes erd
-\end_inset 
-
-
-\the_end