Re: [xml] new SAX2 API

On Wed, Oct 01, 2003 at 10:42:45PM +0100, Graham Bennett wrote:
Here's some more summarisation of my experiences of coding against the
SAX2 API so far..

In order to initialise the SAX handler struct, I had to do something

::memset(ctxt->sax, 0, sizeof(xmlSAXHandler)); // set some callbacks
ctxt->sax->initialized = XML_SAX2_MAGIC;

Daniel is going to provide a function which initialises the struct for
the correct SAX API version so people don't have to know about

                  xmlSAXVersion                   (xmlSAXHandler *hdlr,
                                                   int version);
Where version can be 1 or 2.  The problem is that memset() errases
the magic number :-\

 - I would rather have a string error message and some location
   information than the varargs list that is there currently.  At the
moment I have to run through the args building up a string message

  Based on Havoc's and others feedback here is what I started to work
on, it's very close to Gerror, just specialized for the parser needs:

 * xmlErrorLevel:
 * Indicates the level of an error
typedef enum {
    XML_ERR_NONE = 0,
    XML_ERR_WARNING = 1,        /* A simple warning */
    XML_ERR_ERROR = 2,          /* A recoverable error */
    XML_ERR_FATAL = 3           /* A fatal error */
} xmlErrorLevel;

 * xmlErrorDomain:
 * Indicates where an error may have come from
typedef enum {
    XML_FROM_NONE = 0,
    XML_FROM_PARSER,    /* The XML parser */
    XML_ERR_HTML,       /* The HTML parser */
    XML_ERR_MEMORY,     /* The memory allocator */
    XML_ERR_OUTPUT,     /* The serialization code */
    XML_ERR_IO,         /* The Input/Output stack */
    XML_ERR_XINCLUDE,   /* The XInclude processing */
    XML_ERR_XPATH,      /* The XPath engine */
    XML_ERR_XPOINTER    /* The XPointer engine */
} xmlErrorDomain;

 * xmlError:
 * An XML Error instance.
typedef struct _xmlError xmlError;
typedef xmlError *xmlErrorPtr;
struct _xmlError {
    int         domain; /* What part of the library raised this error */
    int         code;   /* The error code, e.g. an xmlParserError */
    char       *message;/* human-readable informative error message */
    xmlErrorLevel level;/* how consequent is the error */
    char       *file;   /* the filename */
    int         line;   /* the line number if available */
    char       *str1;   /* extra string information */
    char       *str2;   /* extra string information */
    int         int1;   /* extra number information */
    int         int2;   /* extra number information */


 * Extended error information routines
    xmlGetLastError             (void);
    xmlResetLastError           (void);
    xmlCopyError                (xmlErrorPtr from,
                                 xmlErrorPtr to);
    xmlCtxtGetLastError         (void *ctx);
    xmlCtxtResetLastError       (void *ctx);

  The xmlGetLastError() and xmlResetLastError() will work on a global
xmlError which is defined per-thread if the library is configured with
threads. The xmlCtxtGetLastError() and xmlCtxtGetLastError() will
be associated to a parser context, the xmlError is allocated and stored
within the parser context so there is no risk of facing memory allocation
to report error in out of memory condition.
  The real pain is to conver all message reporting in the library to use
those facilities, type of grunt job which is both boring and dangerous,
but this need to get done, and now is the time :-\ , it's certainly more
useful than flaming on xml-dev ...

 - How best to stop the parser?  I think there is an xmlStopParser (or
   similar) function that I should be using.  Is there anything else I
need to worry about when stopping the parse?

  Hum, no, not really. All parsing state will be freed or cleaned up
when calling xmlFreeParserCtxt() or reusing the context with xmlCtxtReadxxx()
I still need to provide similar initialization/reuse for the xmlReader.


Daniel Veillard      | Red Hat Network
veillard redhat com  | libxml GNOME XML XSLT toolkit | Rpmfind RPM search engine

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