libstrophe-gh/src/parser_expat.c

/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
/* 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 or GPLv3 licenses.
*/

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

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

#include <expat.h>

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

/* Allocate inner text by this number bytes more. Expat splits string
 * "new\nline" into 3 strings: "new" "\n" "line". Expecting this pattern,
 * we can leave few bytes in the inner_text for "\n". It should reduce
 * number of re-allocations in 2 times for multi-line texts. */
#define INNER_TEXT_PADDING 2

struct _parser_t {
    xmpp_ctx_t *ctx;
    XML_Parser expat;
    parser_start_callback startcb;
    parser_end_callback endcb;
    parser_stanza_callback stanzacb;
    void *userdata;
    int depth;
    xmpp_stanza_t *stanza;
    char *inner_text;
    /* number of allocated bytes */
    int inner_text_size;
    /* excluding terminal '\0' */
    int inner_text_used;
};

/* Use the Unit Separator to delimit namespace and name in our XML */
const XML_Char namespace_sep = '\x1F';

/*
 * Cached strophe ctx. It is used for memory suite.
 * Note, expat doesn't support userdata in memory suite, therefore,
 * we can support only one strophe context. If user creates more than one
 * context, this module will fallback to default library allocator for all
 * contexts other than mem_ctx.
 */
static xmpp_ctx_t *mem_ctx = NULL;

static void *parser_mem_malloc(size_t size)
{
    if (mem_ctx != NULL)
        return strophe_alloc(mem_ctx, size);
    else
        return NULL;
}

static void *parser_mem_realloc(void *ptr, size_t size)
{
    if (mem_ctx != NULL)
        return strophe_realloc(mem_ctx, ptr, size);
    else
        return NULL;
}

static void parser_mem_free(void *ptr)
{
    if (mem_ctx != NULL)
        strophe_free(mem_ctx, ptr);
}

static const XML_Memory_Handling_Suite parser_mem_suite = {
    .malloc_fcn = &parser_mem_malloc,
    .realloc_fcn = &parser_mem_realloc,
    .free_fcn = &parser_mem_free,
};

/* return allocated string with the name from a delimited
 * namespace/name string */
static char *_xml_name(xmpp_ctx_t *ctx, const char *nsname)
{
    char *result = NULL;
    const char *c;
    size_t len;

    c = strchr(nsname, namespace_sep);
    if (c == NULL)
        return strophe_strdup(ctx, nsname);

    c++;
    len = strlen(c);
    result = strophe_alloc(ctx, len + 1);
    if (result != NULL) {
        memcpy(result, c, len);
        result[len] = '\0';
    }

    return result;
}

/* return allocated string with the namespace from a delimited string */
static char *_xml_namespace(xmpp_ctx_t *ctx, const char *nsname)
{
    char *result = NULL;
    const char *c;

    c = strchr(nsname, namespace_sep);
    if (c != NULL) {
        result = strophe_alloc(ctx, (c - nsname) + 1);
        if (result != NULL) {
            memcpy(result, nsname, (c - nsname));
            result[c - nsname] = '\0';
        }
    }

    return result;
}

static void _set_attributes(xmpp_stanza_t *stanza, const XML_Char **attrs)
{
    char *attr;
    int i;

    if (!attrs)
        return;

    for (i = 0; attrs[i]; i += 2) {
        /* namespaced attributes aren't used in xmpp, discard namespace */
        attr = _xml_name(stanza->ctx, attrs[i]);
        xmpp_stanza_set_attribute(stanza, attr, attrs[i + 1]);
        strophe_free(stanza->ctx, attr);
    }
}

static void complete_inner_text(parser_t *parser)
{
    xmpp_stanza_t *stanza;

    if (parser->inner_text) {
        /* create and populate stanza */
        stanza = xmpp_stanza_new(parser->ctx);
        /* FIXME: disconnect on allocation error */
        if (stanza) {
            xmpp_stanza_set_text(stanza, parser->inner_text);
            xmpp_stanza_add_child_ex(parser->stanza, stanza, 0);
        }
        strophe_free(parser->ctx, parser->inner_text);
        parser->inner_text = NULL;
        parser->inner_text_size = 0;
        parser->inner_text_used = 0;
    }
}

static void
_start_element(void *userdata, const XML_Char *nsname, const XML_Char **attrs)
{
    parser_t *parser = (parser_t *)userdata;
    xmpp_stanza_t *child;
    char *ns, *name;

    ns = _xml_namespace(parser->ctx, nsname);
    name = _xml_name(parser->ctx, nsname);

    if (parser->depth == 0) {
        /* notify the owner */
        if (parser->startcb)
            parser->startcb(name, (char **)attrs, parser->userdata);
    } else {
        /* build stanzas at depth 1 */
        if (!parser->stanza && parser->depth != 1) {
            /* something terrible happened */
            /* FIXME: shutdown disconnect */
            strophe_error(parser->ctx, "parser",
                          "oops, where did our stanza go?");
        } else {
            child = xmpp_stanza_new(parser->ctx);
            if (!child) {
                /* FIXME: can't allocate, disconnect */
            }
            xmpp_stanza_set_name(child, name);
            _set_attributes(child, attrs);
            if (ns)
                xmpp_stanza_set_ns(child, ns);

            if (parser->stanza != NULL) {
                complete_inner_text(parser);
                xmpp_stanza_add_child_ex(parser->stanza, child, 0);
            }
            parser->stanza = child;
        }
    }

    if (ns)
        strophe_free(parser->ctx, ns);
    if (name)
        strophe_free(parser->ctx, name);

    parser->depth++;
}

static void _end_element(void *userdata, const XML_Char *name)
{
    parser_t *parser = (parser_t *)userdata;

    parser->depth--;

    if (parser->depth == 0) {
        /* notify the owner */
        if (parser->endcb)
            parser->endcb((char *)name, parser->userdata);
    } else {
        complete_inner_text(parser);
        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 XML_Char *s, int len)
{
    parser_t *parser = (parser_t *)userdata;
    char *p;

    if (parser->depth < 2)
        return;

    /* Join all parts to a single resulting string. Stanza is created in
     * _start_element() and _end_element(). */
    if (parser->inner_text_used + len >= parser->inner_text_size) {
        parser->inner_text_size =
            parser->inner_text_used + len + 1 + INNER_TEXT_PADDING;
        p = strophe_realloc(parser->ctx, parser->inner_text,
                            parser->inner_text_size);
        if (p == NULL) {
            strophe_free(parser->ctx, parser->inner_text);
            parser->inner_text = NULL;
            parser->inner_text_used = 0;
            parser->inner_text_size = 0;
            return;
        }
        parser->inner_text = p;
        parser->inner_text[parser->inner_text_used] = '\0';
    }
    parser->inner_text_used += len;
    strncat(parser->inner_text, s, len);
}

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 = strophe_alloc(ctx, sizeof(parser_t));
    if (parser != NULL) {
        parser->ctx = ctx;
        parser->expat = NULL;
        parser->startcb = startcb;
        parser->endcb = endcb;
        parser->stanzacb = stanzacb;
        parser->userdata = userdata;
        parser->depth = 0;
        parser->stanza = NULL;
        parser->inner_text = NULL;
        parser->inner_text_size = 0;
        parser->inner_text_used = 0;

        parser_reset(parser);
    }

    return parser;
}

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

static void _free_parent_stanza(xmpp_stanza_t *stanza)
{
    xmpp_stanza_t *parent;

    for (parent = stanza; parent->parent != NULL; parent = parent->parent)
        ;
    xmpp_stanza_release(parent);
}

/* free a parser */
void parser_free(parser_t *parser)
{
    if (parser->expat)
        XML_ParserFree(parser->expat);

    if (parser->stanza) {
        _free_parent_stanza(parser->stanza);
        parser->stanza = NULL;
    }

    if (parser->inner_text) {
        strophe_free(parser->ctx, parser->inner_text);
        parser->inner_text = NULL;
    }

    strophe_free(parser->ctx, parser);
}

/* shuts down and restarts XML parser.  true on success */
int parser_reset(parser_t *parser)
{
    XML_Bool ret;
    const XML_Memory_Handling_Suite *mem = NULL;

    if (parser->expat) {
        ret = XML_ParserReset(parser->expat, NULL);
        if (ret != XML_TRUE) {
            XML_ParserFree(parser->expat);
            parser->expat = NULL;
        }
    } else {
        if (mem_ctx == NULL)
            mem_ctx = parser->ctx;
        if (parser->ctx == mem_ctx)
            mem = &parser_mem_suite;
        parser->expat = XML_ParserCreate_MM(NULL, mem, &namespace_sep);
    }

    if (parser->stanza) {
        _free_parent_stanza(parser->stanza);
        parser->stanza = NULL;
    }

    if (parser->inner_text) {
        strophe_free(parser->ctx, parser->inner_text);
        parser->inner_text = NULL;
    }

    if (!parser->expat)
        return 0;

    parser->depth = 0;

    XML_SetUserData(parser->expat, parser);
    XML_SetElementHandler(parser->expat, _start_element, _end_element);
    XML_SetCharacterDataHandler(parser->expat, _characters);

    return 1;
}

int parser_feed(parser_t *parser, char *chunk, int len)
{
    return XML_Parse(parser->expat, chunk, len, 0);
}