ICU-461.12.tar.gz

[apple/icu.git] / icuSources / common / unicode / ucat.h

/*
**********************************************************************
* Copyright (c) 2003-2004, International Business Machines
* Corporation and others.  All Rights Reserved.
**********************************************************************
* Author: Alan Liu
* Created: March 19 2003
* Since: ICU 2.6
**********************************************************************
*/
#ifndef UCAT_H
#define UCAT_H

#include "unicode/utypes.h"
#include "unicode/ures.h"

/**
 * \file
 * \brief C API: Message Catalog Wrappers
 *
 * This C API provides look-alike functions that deliberately resemble
 * the POSIX catopen, catclose, and catgets functions.  The underlying
 * implementation is in terms of ICU resource bundles, rather than
 * POSIX message catalogs.
 *
 * The ICU resource bundles obey standard ICU inheritance policies.
 * To facilitate this, sets and messages are flattened into one tier.
 * This is done by creating resource bundle keys of the form
 * <set_num>%<msg_num> where set_num is the set number and msg_num is
 * the message number, formatted as decimal strings.
 *
 * Example:  Consider a message catalog containing two sets:
 *
 * Set 1: Message 4  = "Good morning."
 *        Message 5  = "Good afternoon."
 *        Message 7  = "Good evening."
 *        Message 8  = "Good night."
 * Set 4: Message 14 = "Please "
 *        Message 19 = "Thank you."
 *        Message 20 = "Sincerely,"
 *
 * The ICU resource bundle source file would, assuming it is named
 * "greet.txt", would look like this:
 *
 * greet
 * {
 *     1%4  { "Good morning." }
 *     1%5  { "Good afternoon." }
 *     1%7  { "Good evening." }
 *     1%8  { "Good night." }
 * 
 *     4%14 { "Please " }
 *     4%19 { "Thank you." }
 *     4%20 { "Sincerely," }
 * }
 *
 * The catgets function is commonly used in combination with functions
 * like printf and strftime.  ICU components like message format can
 * be used instead, although they use a different format syntax.
 * There is an ICU package, icuio, that provides some of
 * the POSIX-style formatting API.
 */

U_CDECL_BEGIN

/**
 * An ICU message catalog descriptor, analogous to nl_catd.
 * 
 * @stable ICU 2.6
 */
typedef UResourceBundle* u_nl_catd;

/**
 * Open and return an ICU message catalog descriptor. The descriptor
 * may be passed to u_catgets() to retrieve localized strings.
 *
 * @param name string containing the full path pointing to the
 * directory where the resources reside followed by the package name
 * e.g. "/usr/resource/my_app/resources/guimessages" on a Unix system.
 * If NULL, ICU default data files will be used.
 *
 * Unlike POSIX, environment variables are not interpolated within the
 * name.
 *
 * @param locale the locale for which we want to open the resource. If
 * NULL, the default ICU locale will be used (see uloc_getDefault). If
 * strlen(locale) == 0, the root locale will be used.
 *
 * @param ec input/output error code. Upon output,
 * U_USING_FALLBACK_WARNING indicates that a fallback locale was
 * used. For example, 'de_CH' was requested, but nothing was found
 * there, so 'de' was used. U_USING_DEFAULT_WARNING indicates that the
 * default locale data or root locale data was used; neither the
 * requested locale nor any of its fallback locales were found.
 *
 * @return a message catalog descriptor that may be passed to
 * u_catgets(). If the ec parameter indicates success, then the caller
 * is responsible for calling u_catclose() to close the message
 * catalog. If the ec parameter indicates failure, then NULL will be
 * returned.
 * 
 * @stable ICU 2.6
 */
U_STABLE u_nl_catd U_EXPORT2
u_catopen(const char* name, const char* locale, UErrorCode* ec);

/**
 * Close an ICU message catalog, given its descriptor.
 *
 * @param catd a message catalog descriptor to be closed. May be NULL,
 * in which case no action is taken.
 * 
 * @stable ICU 2.6
 */
U_STABLE void U_EXPORT2
u_catclose(u_nl_catd catd);

/**
 * Retrieve a localized string from an ICU message catalog.
 *
 * @param catd a message catalog descriptor returned by u_catopen.
 *
 * @param set_num the message catalog set number. Sets need not be
 * numbered consecutively.
 *
 * @param msg_num the message catalog message number within the
 * set. Messages need not be numbered consecutively.
 *
 * @param s the default string. This is returned if the string
 * specified by the set_num and msg_num is not found. It must be
 * zero-terminated.
 *
 * @param len fill-in parameter to receive the length of the result.
 * May be NULL, in which case it is ignored.
 *
 * @param ec input/output error code. May be U_USING_FALLBACK_WARNING
 * or U_USING_DEFAULT_WARNING. U_MISSING_RESOURCE_ERROR indicates that
 * the set_num/msg_num tuple does not specify a valid message string
 * in this catalog.
 *
 * @return a pointer to a zero-terminated UChar array which lives in
 * an internal buffer area, typically a memory mapped/DLL file. The
 * caller must NOT delete this pointer. If the call is unsuccessful
 * for any reason, then s is returned.  This includes the situation in
 * which ec indicates a failing error code upon entry to this
 * function.
 * 
 * @stable ICU 2.6
 */
U_STABLE const UChar* U_EXPORT2
u_catgets(u_nl_catd catd, int32_t set_num, int32_t msg_num,
          const UChar* s,
          int32_t* len, UErrorCode* ec);

U_CDECL_END

#endif /*UCAT_H*/
/*eof*/