227 lines
9.3 KiB
Plaintext
227 lines
9.3 KiB
Plaintext
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Implementation notes:
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This is a true OS/400 implementation, not a PASE implementation (for PASE,
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use an AIX implementation).
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The biggest problem with OS/400 is EBCDIC. The current libxml2 implementation
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uses UTF-8 internally. To ease encoding conversion between the calling
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applications and libxml2, supplementary "convert and latch" functions are
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provided (See below). To bind the EBCDIC OS/400 system calls and libxml2,
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an ASCII run-time environment (QADRT) has been used and wrapper functions have
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been designed.
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Other problems are:
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- Source code line length: to be stored in DB2 members, source files may not
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have lines longer than 100 characters. Some header and documentation files
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have been modified accordingly.
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- va_list dereferencing: the OS/400 implementation of va_list type is an array
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but the compiler forbids explicit array dereferencing. Source files have
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been updated accordingly.
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- Depending on the compilation/execution environment, it is possible that
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stdin/stdout/stderr are not associated with a file descriptor; as a side
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effect, open() may return a file descriptor value 0, 1 or 2 that is NOT
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a C standard file. Thus using such a number may be inaccurate.
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- iconv_open() arguments: OS/400 uses non-standard encoding names and does not
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support standard names. For this reason, a name wrapper has been designed.
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- dlopen() (support for xmodule): the function and its corollaries are not
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provided by the OS/400 library. However a local implementation is provided.
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Compiling on OS/400:
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_ As a prerequisite, QADRT development environment must be installed.
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_ Install the libxml2 source directory in IFS.
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_ Enter shell (QSH)
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_ Change current directory to the libxml2 installation directory
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_ Change current directory to ./os400
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_ Edit file iniscript.sh. You may want to change tunable configuration
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parameters, like debug info generation, optimisation level, listing option,
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target library, zlib availability, etc.
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_ Copy any file in the current directory to makelog (i.e.:
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cp initscript.sh makelog): this is intended to create the makelog file with
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an ASCII CCSID!
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_ Enter the command "sh make.sh >makelog 2>&1'
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_ Examine the makelog file to check for compilation errors.
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Leaving file initscript.sh unchanged, this will produce the following
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OS/400 objects:
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_ Library LIBXML2. All other objects will be stored in this library.
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_ Modules for all libxml2 units, with full debug info and no code optimization.
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_ Binding directory LIBXML2_A, to be used at calling program link time for
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statically binding the modules (specify BNDSRVPGM(QADRTTS QGLDCLNT QGLDBRDR)
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when creating a program using LIBXML2_A).
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_ Service program LIBXML2. To be used at calling program run-time
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when this program has dynamically bound libxml2 at link time.
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_ Binding directory LIBXML2. To be used to dynamically bind libxml2 when
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linking a calling program.
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_ Source file LIBXML. It contains all the header members needed to compile a
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C/C++ module using libxml2.
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_ Standard and additional C/C++ libxml2 header members (possibly renamed) in
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file LIBXML.
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_ IFS directory /libxml2 with subdirectory include/libxml containing all
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C/C++ header files for IFS-based compilation.
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_ Source file LIBXMLRPG. It contains all the include members needed to compile a
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ILE/RPG module/program using libxml2 (ILE/RPG binding).
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_ ILE/RPG binding include members (possibly renamed) in file LIBXMLRPG.
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_ IFS subdirectory /libxml2/include/libxmlrpg containing all ILE/RPG include
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files for IFS-based compilation.
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Renamed header files in DB2 members:
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DB2 member names are limited to 10 characters, thus the following C/C++
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header members are renamed as:
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parserInternals.h --> PARSERINTE
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schemasInternals.h --> SCHEMASINT
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xmlautomata.h --> XMLAUTOMAT
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xmlschemastype.h --> SCHMTYPES
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xpathInternals.h --> XPATHINTER
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IFS header files are NOT renamed.
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ILE/RPG headers are processed likewise.
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Special programming consideration:
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QADRT being used, the following points must be considered:
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_ If static binding is used, service program QADRTTS must be linked too.
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_ The EBCDIC CCSID used by QADRT is 37 by default, NOT THE JOB'S CCSID. If
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another EBCDIC CCSID is required, it must be set via a locale through a call
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to setlocale_a (QADRT's setlocale() ASCII wrapper) with category LC_ALL or
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LC_CTYPE, or by setting environment variable QADRT_ENV_LOCALE to the locale
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object path before executing the program.
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_ Always use *IFSIO or *IFS64IO to compile calling programs.
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Supplementary (non libxml2 standard) support procedures for OS/400.
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As cited above, there are some procedures to ease encoding conversion of
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libxml2 function arguments and results: the mechanism is based on
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dictionaries. The functions convert a string, latch the result in a dictionary
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to ensure its persistence and return its address. It is the caller's
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responsibility to clean the dictionary when it becomes too big or disappears.
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The procedures are:
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#include <libxml/transcode.h>
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const char * xmlTranscodeResult(const xmlChar * s,
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const char * encoding,
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xmlDictPtr * dict,
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void (*freeproc)(const void *));
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const xmlChar * xmlTranscodeString(const char * s,
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const char * encoding,
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xmlDictPtr * dict);
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const xmlChar * xmlTranscodeWString(const char * s,
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const char * encoding,
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xmlDictPtr * dict);
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const xmlChar * xmlTranscodeWString(const char * s,
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const char * encoding,
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xmlDictPtr * dict);
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where:
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s is the string to translate.
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encoding is the alternate character encoding. If null, the current job's
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encoding (CCSID) is used.
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dict is the address of the latching directory. If NULL, the procedure
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functions as a simple non-latching encoding converter and
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its result value should be freed by the caller.
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freeproc is a procedure to release the original string, or NULL.
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xmlTranscodeResult() converts from UTF-8 to the given alternate encoding.
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xmlTranscodeString() converts from the given 8-bit encoding to UTF-8 (note that
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UTF-8 itself is considered as a 8-bit encoding).
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xmlTranscodeWString() converts from the given 16-bit encoding to UTF-8.
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xmlTranscodeHString() converts from the given 32-bit encoding to UTF-8.
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To shorten statements using these functions, shorthands are defined:
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xmlTR for xmlTranscodeResult
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xmlTS for xmlTranscodeString
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xmlTW for xmlTranscodeWString
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xmlTH for xmlTranscodeHstring
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These shorthands may be disabled by defining XML_NO_SHORT_NAMES before
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libxml/transcode.h inclusion.
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A directory pointer must be preset to NULL before the first call using it to
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one of the above procedure.
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To release a latching directory, use function
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void xmlZapDict(xmlDictPtr * dict);
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Example:
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#include <libxml/transcode.h>
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#include <libxml/tree.h>
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xmlDocPtr mySimpleXMLDoc(char * element, char * text)
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{
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xmlDocPtr doc;
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xmlNodePtr node;
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xmlDictPtr dict = NULL;
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/* element and text are encoded in the current job's encoding. */
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doc = xmlNewDoc();
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xmlNewTextChild((xmlNodePtr) doc, NULL, xmlTS(element, NULL,
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&dict), xmlTS(text, NULL, &dict));
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xmlZapDict(&dict);
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return doc;
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}
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Additionally, a formatter into latched/dynamic storage is provided:
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const char * xmlVasprintf(xmlDictPtr * dict,
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const char * encoding,
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const xmlChar * fmt,
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va_list args);
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xmllint and xmlcatalog programs:
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These programs are fully implemented at the qshell level, with standard
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command line options. Links to these are installed in sub-directory bin of
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the IFS installation directory.
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CL command interfaces to these programs are also provided with limited
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support. In particular, interactive mode is not supported and argument count
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and lengths are limited by the CL command syntax.
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ILE/RPG binding:
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All standard types and procedures are provided. Since ILE/RPG does not
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support macros, they have not been ported. However some of them are emulated
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as functions: these are the more useful ones (xmlXPathNodeSetGetLength,
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xmlXPathNodeSetItem, xmlXPathNodeSetIsEmpty, htmlDefaultSubelement,
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htmlElementAllowedHereDesc, htmlRequiredAttrs) and the global/threaded
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variables access macros. These variables can be read with function
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get_xxx(void), where xxxx is the name of the variable; they may be set by
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calling function set_xxxx(value), where value is of the same type as the
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variable.
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The C va_list is not implemented as such in ILE/RPG. Functions implementing
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va_list and associated methods are provided:
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/include "libxmlrpg/xmlstdarg"
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d xmlVaStart pr
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d list like(xmlVaList)
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d lastargaddr * value
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d lastargsize 10u 0 value
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d xmlVaArg pr
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d list like(xmlVaList)
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d dest * value
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d argsize 10i 0 value
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d xmlVaEnd pr
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d list like(xmlVaList)
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