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<!-- Copyright (C) 2003 Red Hat, Inc. --> <!-- This material may be distributed only subject to the terms --> <!-- and conditions set forth in the Open Publication License, v1.0 --> <!-- or later (the latest version is presently available at --> <!-- http://www.opencontent.org/openpub/). --> <!-- Distribution of the work or derivative of the work in any --> <!-- standard (paper) book form is prohibited unless prior --> <!-- permission is obtained from the copyright holder. --> <HTML ><HEAD ><TITLE >Package Versioning</TITLE ><meta name="MSSmartTagsPreventParsing" content="TRUE"> <META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="The eCos Component Writer's Guide" HREF="cdl-guide.html"><LINK REL="UP" TITLE="Package Organization" HREF="package.html"><LINK REL="PREVIOUS" TITLE="Package Organization" HREF="package.html"><LINK REL="NEXT" TITLE="Package Contents and Layout" HREF="package.contents.html"></HEAD ><BODY CLASS="SECT1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >The <SPAN CLASS="APPLICATION" >eCos</SPAN > Component Writer's Guide</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="package.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 2. Package Organization</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="package.contents.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="PACKAGE.VERSIONS">Package Versioning</H1 ><P >Below each package directory there can be one or more version sub-directories, named after the versions. This is a requirement of the component framework: it must be possible for users to install multiple versions of a package and select which one to use for any given application. This has a number of advantages to users: most importantly it allows a single component repository to be shared between multiple users and multiple projects, as required; also it facilitates experiments, for example it is relatively easy to try out the latest version of some package and see if it makes any difference. There is a potential disadvantage in terms of disk space. However since <SPAN CLASS="APPLICATION" >eCos</SPAN > packages generally consist of source code intended for small embedded systems, and given typical modern disk sizes, keeping a number of different versions of a package installed will usually be acceptable. The administration tool can be used to remove versions that are no longer required.</P ><DIV CLASS="INFORMALFIGURE" ><A NAME="AEN217"><P ></P ><DIV CLASS="MEDIAOBJECT" ><P ><IMG SRC="version.png" ALIGN="CENTER"></P ></DIV ><P ></P ></DIV ><P >The version <TT CLASS="FILENAME" >current</TT > is special. Typically it corresponds to the very latest version of the sources, obtained by anonymous <SPAN CLASS="APPLICATION" >CVS</SPAN >. These sources may change frequently, unlike full releases which do not change (or only when patches are produced). Component writers may also want to work on the <TT CLASS="FILENAME" >current</TT > version.</P ><P >All other subdirectories of a package correspond to specific releases of that package. The component framework allows users to select the particular version of a package they want to use, but by default the most recent one will be used. This requires some rules for ordering version numbers, a difficult task because of the wide variety of ways in which versions can be identified.</P ><P ></P ><OL TYPE="1" ><LI ><P >The version <TT CLASS="FILENAME" >current</TT > is always considered to be the most recent version.</P ></LI ><LI ><P >If the first character of both strings are either <TT CLASS="LITERAL" >v</TT > or <TT CLASS="LITERAL" >V</TT >, these are skipped because it makes little sense to enforce case sensitivity here. Potentially this could result in ambiguity if there are two version directories <TT CLASS="LITERAL" >V1.0</TT > and <TT CLASS="LITERAL" >v1.0</TT >, but this will match the confusion experienced by any users of such a package. However if two subsequent releases are called <TT CLASS="LITERAL" >V1.0</TT > and <TT CLASS="LITERAL" >v1.1</TT >, e.g. because of a minor mix-up when making the distribution file, then the case difference is ignored.</P ></LI ><LI ><P >Next the two version strings are compared one character at a time. If both strings are currently at a digit then a string to number conversion takes place, and the resulting numbers are compared. For example <TT CLASS="LITERAL" >v10</TT > is a more recent release than <TT CLASS="LITERAL" >v2</TT >. If the two numbers are the same then processing continues, so for <TT CLASS="LITERAL" >v2b</TT > and <TT CLASS="LITERAL" >v2c</TT > the version comparison code would move on to <TT CLASS="LITERAL" >b</TT > and <TT CLASS="LITERAL" >c</TT >. </P ></LI ><LI ><P >The characters dot <TT CLASS="LITERAL" >.</TT >, hyphen <TT CLASS="LITERAL" >-</TT > and underscore <TT CLASS="LITERAL" >_</TT > are treated as equivalent separators, so if one release goes out as <TT CLASS="LITERAL" >v1_1</TT > and the next goes out as <TT CLASS="LITERAL" >v1.2</TT > the separator has no effect.</P ></LI ><LI ><P >If neither string has yet terminated but the characters are different, ASCII comparison is used. For example <TT CLASS="LITERAL" >V1.1b</TT > is more recent than <TT CLASS="LITERAL" >v1.1alpha</TT >.</P ></LI ><LI ><P >If one version string terminates before the other, the current character determines which is the more recent. If the other string is currently at a separator character, for example <TT CLASS="LITERAL" >v1.3.1</TT > and <TT CLASS="LITERAL" >v1.3</TT >, then the former is assumed to be a minor release and hence more recent than the latter. If the other string is not at a separator character, for example <TT CLASS="LITERAL" >v1.3beta</TT >, then it is treated as an experimental version of the <TT CLASS="LITERAL" >v1.3</TT > release and hence older. </P ></LI ><LI ><P >There is no special processing of dates, so with two versions <TT CLASS="LITERAL" >ss-20000316</TT > and <TT CLASS="LITERAL" >ss-20001111</TT > the numerical values <TT CLASS="LITERAL" >20001111</TT > and <TT CLASS="LITERAL" >20000316</TT > determine the result: larger values are more recent. It is suggested that the full year be used in such cases rather than a shorthand like <TT CLASS="LITERAL" >00</TT >, to avoid Y2100 problems.</P ></LI ><LI ><P >There is no limit on how many levels of versioning are used, so there could in theory be a <TT CLASS="LITERAL" >v3.1.4.1.5.9.2.7</TT > release of a package. However this is unlikely to be of benefit to typical users of a package.</P ></LI ></OL ><P >The version comparison rules of the component framework may not be suitable for every version numbering scheme in existence, but they should cope with many common cases.</P ><DIV CLASS="CAUTION" ><P ></P ><TABLE CLASS="CAUTION" BORDER="1" WIDTH="100%" ><TR ><TD ALIGN="CENTER" ><B >Caution</B ></TD ></TR ><TR ><TD ALIGN="LEFT" ><P >There are some issues still to be resolved before it is possible to combine the <TT CLASS="FILENAME" >current</TT > sources available via anonymous <SPAN CLASS="APPLICATION" >CVS</SPAN > and full releases of <SPAN CLASS="APPLICATION" >eCos</SPAN > and additional packages in a single component repository. The first problem relates to the <SPAN CLASS="DATABASE" >ecos.db</SPAN > database: if a new package is added via the CVS repository then this requires a database update, but the administration tool is bypassed. The second problem arises if an organization chooses to place its component repository under source code control using <SPAN CLASS="APPLICATION" >CVS</SPAN >, in which case different directories will belong to different <SPAN CLASS="APPLICATION" >CVS</SPAN > servers. These issues will be addressed in a future release.</P ></TD ></TR ></TABLE ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="package.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="cdl-guide.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="package.contents.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Package Organization</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="package.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Package Contents and Layout</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
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