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ICU-879 document uses and limitations of CCSIDs

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X-SVN-Rev: 4160
This commit is contained in:
Markus Scherer 2001-03-17 01:36:48 +00:00
parent 9fec1baba2
commit b8f1a59545
1 changed files with 60 additions and 6 deletions
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66
icu4c/source/common/unicode/ucnv.h
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@ -86,9 +86,12 @@ typedef enum {
} UConverterType;
/**
* Enum for specifying which platform a converter ID refers to
* Enum for specifying which platform a converter ID refers to.
* The use of platform/CCSID is not recommended. See ucnv_openCCSID().
*
* @see ucnv_getPlatform
* @see ucnv_openCCSID
* @see ucnv_getCCSID
*/
typedef enum {
@ -244,7 +247,51 @@ ucnv_openU (const UChar * name,
UErrorCode * err);
/**
* Creates a UConverter object from a CCSID number and platform pair
* Creates a UConverter object from a CCSID number and platform pair.
* Note that the usefulness of this function is limited to platforms with numeric
* encoding IDs. Only IBM and Microsoft platforms use numeric (16-bit) identifiers for
* encodings.
*
* In addition, IBM CCSIDs and Unicode conversion tables are not 1:1 related.
* For many IBM CCSIDs there are multiple (up to six) Unicode conversion tables, and
* for some Unicode conversion tables there are multiple CCSIDs.
* Some "alternate" Unicode conversion tables are provided by the
* IBM CDRA conversion table registry.
* The most prominent example of a systematic modification of conversion tables that is
* not provided in the form of conversion table files in the repository is
* that S/390 Unix System Services swaps the codes for Line Feed and New Line in all
* EBCDIC codepages, which requires such a swap in the Unicode conversion tables as well.
*
* Only IBM default conversion tables are accessible with ucnv_openCCSID().
* ucnv_getCCSID() will return the same CCSID for all conversion tables that are associated
* with that CCSID.
*
* Currently, the only "platform" supported in the ICU converter API is UCNV_IBM.
*
* In summary, the use of CCSIDs and the associated API functions is not recommended.
*
* In order to open a converter with the default IBM CDRA Unicode conversion table,
* you can use this function or use the prefix "ibm-":
* \code
* char name[20];
* sprintf(name, "ibm-%hu", ccsid);
* cnv=ucnv_open(name, &errorCode);
* \endcode
*
* In order to open a converter with the IBM S/390 Unix System Services variant of a Unicode/EBCDIC conversion table,
* you can use the prefix "ibm-" together with the suffix "-s390":
* \code
* char name[20];
* sprintf(name, "ibm-%hu-s390", ccsid);
* cnv=ucnv_open(name, &errorCode);
* \endcode
*
* In order to open a converter from a Microsoft codepage number, use the prefix "cp":
* \code
* char name[20];
* sprintf(name, "cp%hu", codepageID);
* cnv=ucnv_open(name, &errorCode);
* \endcode
*
* @param codepage codepage number to create
* @param platform the platform in which the codepage number exists
@ -254,6 +301,8 @@ ucnv_openU (const UChar * name,
* @see ucnv_open
* @see ucnv_openU
* @see ucnv_close
* @see ucnv_getCCSID
* @see ucnv_getPlatform
* @see UConverterPlatform
* @stable
*/
@ -300,10 +349,6 @@ U_CAPI UConverter *
* @see ucnv_openCCSID
* @stable
*/
U_CAPI void U_EXPORT2
ucnv_close (UConverter * converter);
@ -487,10 +532,19 @@ ucnv_getName (const UConverter * converter, UErrorCode * err);
* is available.
* Does not check if the converter is <TT>NULL</TT> or if converter's data
* table is <TT>NULL</TT>.
*
* Important: The use of CCSIDs is not recommended because it is limited
* to only two platforms in principle and only one (UCNV_IBM) in the current
* ICU converter API.
* Also, CCSIDs are insufficient to identify IBM Unicode conversion tables precisely.
* For more details see ucnv_openCCSID().
*
* @param converter the Unicode converter
* @param err the error status code.
* @return If any error occurrs, -1 will be returned otherwise, the codepage number
* will be returned
* @see ucnv_openCCSID
* @see ucnv_getPlatform
* @stable
*/
U_CAPI int32_t U_EXPORT2