parser_libxml2.c

/* parser.c
** strophe XMPP client library -- xml parser handlers and utility functions
**
** Copyright (C) 2005-2009 Collecta, Inc.
**
**  This software is provided AS-IS with no warranty, either express
**  or implied.
**
**  This program is dual licensed under the MIT and GPLv3 licenses.
*/

/** @file
 *  XML parser handlers.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <libxml/parser.h>
#include <libxml/tree.h>

#include "strophe.h"
#include "common.h"
#include "parser.h"

struct _parser_t {
    xmpp_ctx_t *ctx;
    xmlParserCtxtPtr xmlctx;
    xmlSAXHandler handlers;
    parser_start_callback startcb;
    parser_end_callback endcb;
    parser_stanza_callback stanzacb;
    void *userdata;
    int depth;
    xmpp_stanza_t *stanza;
};

static void
_set_attributes(xmpp_stanza_t *stanza, int nattrs, const xmlChar **attrs)
{
    int i, len;
    char *value;

    if (!attrs)
        return;

    /* SAX2 uses array of localname/prefix/uri/value_begin/value_end */
    for (i = 0; i < nattrs * 5; i += 5) {
        len = attrs[i + 4] - attrs[i + 3];
        value = xmpp_alloc(stanza->ctx, len + 1);
        if (value) {
            memcpy(value, attrs[i + 3], len);
            value[len] = '\0';
            xmpp_stanza_set_attribute(stanza, (const char *)attrs[i], value);
            xmpp_free(stanza->ctx, value);
        }
    }
}

/* SAX2 gives us the attrs in an incredibly inconvenient array,
 * convert it to what the start callback is expecting */
static char **
_convert_attrs(parser_t *parser, int nattrs, const xmlChar **attrs)
{
    int c, i, o, len;
    char *value;
    char **ret;

    if (!attrs)
        return NULL;

    ret = xmpp_alloc(parser->ctx, (nattrs + 1) * 2 * sizeof(char *));
    if (!ret)
        return NULL;
    memset(ret, 0, (nattrs + 1) * 2 * sizeof(char *));

    for (c = 0; c < nattrs; c++) {
        i = c * 5;
        o = c * 2;

        len = attrs[i + 4] - attrs[i + 3];
        value = xmpp_alloc(parser->ctx, len + 1);
        if (value) {
            memcpy(value, attrs[i + 3], len);
            value[len] = '\0';
            ret[o] = xmpp_strdup(parser->ctx, (char *)attrs[i]);
            ret[o + 1] = value;
        }
    }

    return ret;
}

static void _free_cbattrs(parser_t *parser, char **attrs)
{
    int i;

    if (!attrs)
        return;

    for (i = 0; attrs[i]; i += 2) {
        if (attrs[i])
            xmpp_free(parser->ctx, attrs[i]);
        if (attrs[i + 1])
            xmpp_free(parser->ctx, attrs[i + 1]);
    }

    xmpp_free(parser->ctx, attrs);
}

static void _start_element(void *userdata,
                           const xmlChar *name,
                           const xmlChar *prefix,
                           const xmlChar *uri,
                           int nnamespaces,
                           const xmlChar **namespaces,
                           int nattrs,
                           int ndefaulted,
                           const xmlChar **attrs)
{
    parser_t *parser = (parser_t *)userdata;
    xmpp_stanza_t *child;
    char **cbattrs;

    UNUSED(prefix);
    UNUSED(nnamespaces);
    UNUSED(namespaces);
    UNUSED(ndefaulted);

    if (parser->depth == 0) {
        /* notify the owner */
        if (parser->startcb) {
            cbattrs = _convert_attrs(parser, nattrs, attrs);
            parser->startcb((char *)name, cbattrs, parser->userdata);
            _free_cbattrs(parser, cbattrs);
        }
    } else {
        /* build stanzas at depth 1 */
        if (!parser->stanza && parser->depth != 1) {
            /* something terrible happened */
            /* FIXME: we should probably trigger a disconnect */
            xmpp_error(parser->ctx, "parser", "oops, where did our stanza go?");
        } else if (!parser->stanza) {
            /* starting a new toplevel stanza */
            parser->stanza = xmpp_stanza_new(parser->ctx);
            if (!parser->stanza) {
                /* FIXME: can't allocate, disconnect */
            }
            xmpp_stanza_set_name(parser->stanza, (char *)name);
            _set_attributes(parser->stanza, nattrs, attrs);
            if (uri)
                xmpp_stanza_set_ns(parser->stanza, (char *)uri);
        } else {
            /* starting a child of conn->stanza */
            child = xmpp_stanza_new(parser->ctx);
            if (!child) {
                /* FIXME: can't allocate, disconnect */
            }
            xmpp_stanza_set_name(child, (char *)name);
            _set_attributes(child, nattrs, attrs);
            if (uri)
                xmpp_stanza_set_ns(child, (char *)uri);

            /* add child to parent */
            xmpp_stanza_add_child(parser->stanza, child);

            /* the child is owned by the toplevel stanza now */
            xmpp_stanza_release(child);

            /* make child the current stanza */
            parser->stanza = child;
        }
    }

    parser->depth++;
}

static void _end_element(void *userdata,
                         const xmlChar *name,
                         const xmlChar *prefix,
                         const xmlChar *uri)
{
    parser_t *parser = (parser_t *)userdata;

    UNUSED(prefix);
    UNUSED(uri);

    parser->depth--;

    if (parser->depth == 0) {
        /* notify owner */
        if (parser->endcb)
            parser->endcb((char *)name, parser->userdata);
    } else {
        if (parser->stanza->parent) {
            /* we're finishing a child stanza, so set current to the parent */
            parser->stanza = parser->stanza->parent;
        } else {
            if (parser->stanzacb)
                parser->stanzacb(parser->stanza, parser->userdata);
            xmpp_stanza_release(parser->stanza);
            parser->stanza = NULL;
        }
    }
}

static void _characters(void *userdata, const xmlChar *chr, int len)
{
    parser_t *parser = (parser_t *)userdata;
    xmpp_stanza_t *stanza;

    /* skip unimportant whitespace, etc */
    if (parser->depth < 2)
        return;

    /* create and populate stanza */
    stanza = xmpp_stanza_new(parser->ctx);
    if (!stanza) {
        /* FIXME: allocation error, disconnect */
        return;
    }
    xmpp_stanza_set_text_with_size(stanza, (char *)chr, len);

    xmpp_stanza_add_child(parser->stanza, stanza);
    xmpp_stanza_release(stanza);
}

/* create a new parser */
parser_t *parser_new(xmpp_ctx_t *ctx,
                     parser_start_callback startcb,
                     parser_end_callback endcb,
                     parser_stanza_callback stanzacb,
                     void *userdata)
{
    parser_t *parser;

    parser = xmpp_alloc(ctx, sizeof(parser_t));
    if (parser != NULL) {
        parser->ctx = ctx;
        parser->xmlctx = NULL;
        memset(&parser->handlers, 0, sizeof(xmlSAXHandler));
        parser->handlers.initialized = XML_SAX2_MAGIC;
        parser->handlers.startElementNs = _start_element;
        parser->handlers.endElementNs = _end_element;
        parser->handlers.characters = _characters;
        parser->startcb = startcb;
        parser->endcb = endcb;
        parser->stanzacb = stanzacb;
        parser->userdata = userdata;
        parser->depth = 0;
        parser->stanza = NULL;

        parser_reset(parser);
    }

    return parser;
}

char *parser_attr_name(xmpp_ctx_t *ctx, char *nsname)
{
    return xmpp_strdup(ctx, nsname);
}

/* free a parser */
void parser_free(parser_t *parser)
{
    if (parser->xmlctx)
        xmlFreeParserCtxt(parser->xmlctx);
    if (parser->stanza)
        xmpp_stanza_release(parser->stanza);
    xmpp_free(parser->ctx, parser);
}

/* shuts down and restarts XML parser.  true on success */
int parser_reset(parser_t *parser)
{
    if (parser->xmlctx)
        xmlFreeParserCtxt(parser->xmlctx);
    if (parser->stanza)
        xmpp_stanza_release(parser->stanza);

    parser->stanza = NULL;
    parser->depth = 0;

    parser->xmlctx =
        xmlCreatePushParserCtxt(&parser->handlers, parser, NULL, 0, NULL);

    return parser->xmlctx ? 1 : 0;
}

/* feed a chunk of data to the parser */
int parser_feed(parser_t *parser, char *chunk, int len)
{
    /* xmlParseChunk API returns 0 on success which is opposite logic to
       the status returned by parser_feed */
    return !xmlParseChunk(parser->xmlctx, chunk, len, 0);
}