httpd/server/util_xml.c

	util_xml.c revision 1b21d7b3d97def358b2e923655edeb16613a1c31
/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2000 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

/*
** DAV extension module for Apache 2.0.*
**  - XML parser for the body of a request
*/

/* James Clark's Expat parser */
#include "xmlparse.h"

#include "apr.h"
#include "apr_strings.h"

#define APR_WANT_STDIO          /* for fprintf(), sprintf() */
#define APR_WANT_STRFUNC
#include "apr_want.h"

#include "httpd.h"
#include "http_protocol.h"
#include "http_log.h"
#include "http_core.h"

#include "util_xml.h"


#define DEBUG_CR "\r\n"

#define AP_XML_READ_BLOCKSIZE   2048    /* used for reading input blocks */

/* errors related to namespace processing */
#define AP_XML_NS_ERROR_UNKNOWN_PREFIX  (AP_XML_NS_ERROR_BASE)

/* test for a namespace prefix that begins with [Xx][Mm][Ll] */
#define AP_XML_NS_IS_RESERVED(name) \
    ( (name[0] == 'X' || name[0] == 'x') && \
      (name[1] == 'M' || name[1] == 'm') && \
      (name[2] == 'L' || name[2] == 'l') )


/* content for parsing */
typedef struct ap_xml_ctx {
    ap_xml_doc *doc;        /* the doc we're parsing */
    apr_pool_t *p;      /* the pool we allocate from */
    ap_xml_elem *cur_elem;  /* current element */

    int error;          /* an error has occurred */
    /* errors may be AP_XML_NS_ERROR_* or other private errors which will
       be defined here (none yet) */

} ap_xml_ctx;

/* struct for scoping namespace declarations */
typedef struct ap_xml_ns_scope {
    const char *prefix;     /* prefix used for this ns */
    int ns;         /* index into namespace table */
    int emptyURI;       /* the namespace URI is the empty string */
    struct ap_xml_ns_scope *next;   /* next scoped namespace */
} ap_xml_ns_scope;


/* return namespace table index for a given prefix */
static int find_prefix(ap_xml_ctx *ctx, const char *prefix)
{
    ap_xml_elem *elem = ctx->cur_elem;

    /*
    ** Walk up the tree, looking for a namespace scope that defines this
    ** prefix.
    */
    for (; elem; elem = elem->parent) {
    ap_xml_ns_scope *ns_scope = elem->ns_scope;

    for (ns_scope = elem->ns_scope; ns_scope; ns_scope = ns_scope->next) {
        if (strcmp(prefix, ns_scope->prefix) == 0) {
        if (ns_scope->emptyURI) {
            /*
            ** It is possible to set the default namespace to an
            ** empty URI string; this resets the default namespace
            ** to mean "no namespace." We just found the prefix
            ** refers to an empty URI, so return "no namespace."
            */
            return AP_XML_NS_NONE;
        }

        return ns_scope->ns;
        }
    }
    }

    /*
     * If the prefix is empty (""), this means that a prefix was not
     * specified in the element/attribute. The search that was performed
     * just above did not locate a default namespace URI (which is stored
     * into ns_scope with an empty prefix). This means the element/attribute
     * has "no namespace". We have a reserved value for this.
     */
    if (*prefix == '\0') {
    return AP_XML_NS_NONE;
    }

    /* not found */
    return AP_XML_NS_ERROR_UNKNOWN_PREFIX;
}

static void start_handler(void *userdata, const char *name, const char **attrs)
{
    ap_xml_ctx *ctx = userdata;
    ap_xml_elem *elem;
    ap_xml_attr *attr;
    ap_xml_attr *prev;
    char *colon;
    const char *quoted;
    char *elem_name;

    /* punt once we find an error */
    if (ctx->error)
    return;

    elem = apr_pcalloc(ctx->p, sizeof(*elem));

    /* prep the element */
    elem->name = elem_name = apr_pstrdup(ctx->p, name);

    /* fill in the attributes (note: ends up in reverse order) */
    while (*attrs) {
    attr = apr_palloc(ctx->p, sizeof(*attr));
    attr->name = apr_pstrdup(ctx->p, *attrs++);
    attr->value = apr_pstrdup(ctx->p, *attrs++);
    attr->next = elem->attr;
    elem->attr = attr;
    }

    /* hook the element into the tree */
    if (ctx->cur_elem == NULL) {
    /* no current element; this also becomes the root */
    ctx->cur_elem = ctx->doc->root = elem;
    }
    else {
    /* this element appeared within the current elem */
    elem->parent = ctx->cur_elem;

    /* set up the child/sibling links */
    if (elem->parent->last_child == NULL) {
        /* no first child either */
        elem->parent->first_child = elem->parent->last_child = elem;
    }
    else {
        /* hook onto the end of the parent's children */
        elem->parent->last_child->next = elem;
        elem->parent->last_child = elem;
    }

    /* this element is now the current element */
    ctx->cur_elem = elem;
    }

    /* scan the attributes for namespace declarations */
    for (prev = NULL, attr = elem->attr;
     attr;
     attr = attr->next) {
    if (strncmp(attr->name, "xmlns", 5) == 0) {
        const char *prefix = &attr->name[5];
        ap_xml_ns_scope *ns_scope;

        /* test for xmlns:foo= form and xmlns= form */
        if (*prefix == ':')
        ++prefix;
        else if (*prefix != '\0') {
        /* advance "prev" since "attr" is still present */
        prev = attr;
        continue;
        }

        /* quote the URI before we ever start working with it */
        quoted = ap_xml_quote_string(ctx->p, attr->value, 1);

        /* build and insert the new scope */
        ns_scope = apr_pcalloc(ctx->p, sizeof(*ns_scope));
        ns_scope->prefix = prefix;
        ns_scope->ns = ap_xml_insert_uri(ctx->doc->namespaces, quoted);
        ns_scope->emptyURI = *quoted == '\0';
        ns_scope->next = elem->ns_scope;
        elem->ns_scope = ns_scope;

        /* remove this attribute from the element */
        if (prev == NULL)
        elem->attr = attr->next;
        else
        prev->next = attr->next;

        /* Note: prev will not be advanced since we just removed "attr" */
    }
    else if (strcmp(attr->name, "xml:lang") == 0) {
        /* save away the language (in quoted form) */
        elem->lang = ap_xml_quote_string(ctx->p, attr->value, 1);

        /* remove this attribute from the element */
        if (prev == NULL)
        elem->attr = attr->next;
        else
        prev->next = attr->next;

        /* Note: prev will not be advanced since we just removed "attr" */
    }
    else {
        /* advance "prev" since "attr" is still present */
        prev = attr;
    }
    }

    /*
    ** If an xml:lang attribute didn't exist (lang==NULL), then copy the
    ** language from the parent element (if present).
    **
    ** NOTE: elem_size() *depends* upon this pointer equality.
    */
    if (elem->lang == NULL && elem->parent != NULL)
    elem->lang = elem->parent->lang;

    /* adjust the element's namespace */
    colon = ap_strchr(elem_name, ':');
    if (colon == NULL) {
    /*
     * The element is using the default namespace, which will always
     * be found. Either it will be "no namespace", or a default
     * namespace URI has been specified at some point.
     */
    elem->ns = find_prefix(ctx, "");
    }
    else if (AP_XML_NS_IS_RESERVED(elem->name)) {
    elem->ns = AP_XML_NS_NONE;
    }
    else {
    *colon = '\0';
    elem->ns = find_prefix(ctx, elem->name);
    elem->name = colon + 1;

    if (AP_XML_NS_IS_ERROR(elem->ns)) {
        ctx->error = elem->ns;
        return;
    }
    }

    /* adjust all remaining attributes' namespaces */
    for (attr = elem->attr; attr; attr = attr->next) {
        /*
         * ap_xml_attr defines this as "const" but we dup'd it, so we
         * know that we can change it. a bit hacky, but the existing
         * structure def is best.
         */
        char *attr_name = (char *)attr->name;

    colon = ap_strchr(attr_name, ':');
    if (colon == NULL) {
        /*
         * Attributes do NOT use the default namespace. Therefore,
         * we place them into the "no namespace" category.
         */
        attr->ns = AP_XML_NS_NONE;
    }
    else if (AP_XML_NS_IS_RESERVED(attr->name)) {
        attr->ns = AP_XML_NS_NONE;
    }
    else {
        *colon = '\0';
        attr->ns = find_prefix(ctx, attr->name);
        attr->name = colon + 1;

        if (AP_XML_NS_IS_ERROR(attr->ns)) {
        ctx->error = attr->ns;
        return;
        }
    }
    }
}

static void end_handler(void *userdata, const char *name)
{
    ap_xml_ctx *ctx = userdata;

    /* punt once we find an error */
    if (ctx->error)
    return;

    /* pop up one level */
    ctx->cur_elem = ctx->cur_elem->parent;
}

static void cdata_handler(void *userdata, const char *data, int len)
{
    ap_xml_ctx *ctx = userdata;
    ap_xml_elem *elem;
    ap_text_header *hdr;
    const char *s;

    /* punt once we find an error */
    if (ctx->error)
    return;

    elem = ctx->cur_elem;
    s = apr_pstrndup(ctx->p, data, len);

    if (elem->last_child == NULL) {
    /* no children yet. this cdata follows the start tag */
    hdr = &elem->first_cdata;
    }
    else {
    /* child elements exist. this cdata follows the last child. */
    hdr = &elem->last_child->following_cdata;
    }

    ap_text_append(ctx->p, hdr, s);
}

AP_DECLARE(int) ap_xml_parse_input(request_rec * r, ap_xml_doc **pdoc)
{
    int result;
    ap_xml_ctx ctx = { 0 };
    XML_Parser parser;

    if ((result = ap_setup_client_block(r, REQUEST_CHUNKED_DECHUNK)) != OK)
    return result;

    if (r->remaining == 0) {
    *pdoc = NULL;
    return OK;
    }

    ctx.p = r->pool;
    ctx.doc = apr_pcalloc(ctx.p, sizeof(*ctx.doc));

    ctx.doc->namespaces = apr_array_make(ctx.p, 5, sizeof(const char *));
    ap_xml_insert_uri(ctx.doc->namespaces, "DAV:");

    /* ### we should get the encoding from Content-Encoding */
    parser = XML_ParserCreate(NULL);
    if (parser == NULL) {
    /* ### anything better to do? */
    fprintf(stderr, "Ouch!  XML_ParserCreate() failed!\n");
    exit(1);
    }

    XML_SetUserData(parser, (void *) &ctx);
    XML_SetElementHandler(parser, start_handler, end_handler);
    XML_SetCharacterDataHandler(parser, cdata_handler);

    if (ap_should_client_block(r)) {
    long len;
    char *buffer;
    char end;
    int rv;
    apr_size_t total_read = 0;
    apr_size_t limit_xml_body = ap_get_limit_xml_body(r);

    /* allocate our working buffer */
    buffer = apr_palloc(r->pool, AP_XML_READ_BLOCKSIZE);

    /* read the body, stuffing it into the parser */
    while ((len = ap_get_client_block(r, buffer, AP_XML_READ_BLOCKSIZE)) > 0) {
        total_read += len;
        if (limit_xml_body && total_read > limit_xml_body) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR | APLOG_NOERRNO, 0, r,
                  "XML request body is larger than the configured "
                  "limit of %lu", (unsigned long)limit_xml_body);
        goto read_error;
        }

        rv = XML_Parse(parser, buffer, len, 0);
        if (rv == 0)
        goto parser_error;
    }
    if (len == -1) {
        /* ap_get_client_block() has logged an error */
        goto read_error;
    }

    /* tell the parser that we're done */
    rv = XML_Parse(parser, &end, 0, 1);
    if (rv == 0)
        goto parser_error;
    }

    XML_ParserFree(parser);

    if (ctx.error) {
    switch (ctx.error) {
    case AP_XML_NS_ERROR_UNKNOWN_PREFIX:
        ap_log_rerror(APLOG_MARK, APLOG_ERR | APLOG_NOERRNO, 0, r,
              "An undefined namespace prefix was used.");
        break;

    default:
        ap_log_rerror(APLOG_MARK, APLOG_ERR | APLOG_NOERRNO, 0, r,
              "There was an error within the XML request body.");
        break;
    }

    /* Apache will supply a default error, plus the error log above. */
    return HTTP_BAD_REQUEST;
    }

    /* ### assert: ctx.cur_elem == NULL */

    *pdoc = ctx.doc;

    return OK;

  parser_error:
    {
    enum XML_Error err = XML_GetErrorCode(parser);

    /* ### fix this error message (default vs special) */
    ap_log_rerror(APLOG_MARK, APLOG_ERR | APLOG_NOERRNO, 0, r,
              "XML parser error code: %s (%d).",
              XML_ErrorString(err), err);

    XML_ParserFree(parser);

    /* Apache will supply a default error, plus the error log above. */
    return HTTP_BAD_REQUEST;
    }

  read_error:
    XML_ParserFree(parser);

    /* Apache will supply a default error, plus whatever was logged. */
    return HTTP_BAD_REQUEST;
}

AP_DECLARE(void) ap_text_append(apr_pool_t * p, ap_text_header *hdr,
                                const char *text)
{
    ap_text *t = apr_palloc(p, sizeof(*t));

    t->text = text;
    t->next = NULL;

    if (hdr->first == NULL) {
    /* no text elements yet */
    hdr->first = hdr->last = t;
    }
    else {
    /* append to the last text element */
    hdr->last->next = t;
    hdr->last = t;
    }
}


/* ---------------------------------------------------------------
**
** XML UTILITY FUNCTIONS
*/

/*
** ap_xml_quote_string: quote an XML string
**
** Replace '<', '>', and '&' with '&lt;', '&gt;', and '&amp;'.
** If quotes is true, then replace '"' with '&quot;'.
**
** quotes is typically set to true for XML strings that will occur within
** double quotes -- attribute values.
*/
AP_DECLARE(const char *) ap_xml_quote_string(apr_pool_t *p, const char *s,
                                             int quotes)
{
    const char *scan;
    apr_size_t len = 0;
    apr_size_t extra = 0;
    char *qstr;
    char *qscan;
    char c;

    for (scan = s; (c = *scan) != '\0'; ++scan, ++len) {
    if (c == '<' || c == '>')
        extra += 3;     /* &lt; or &gt; */
    else if (c == '&')
        extra += 4;     /* &amp; */
    else if (quotes && c == '"')
        extra += 5;     /* &quot; */
    }

    /* nothing to do? */
    if (extra == 0)
    return s;

    qstr = apr_palloc(p, len + extra + 1);
    for (scan = s, qscan = qstr; (c = *scan) != '\0'; ++scan) {
    if (c == '<') {
        *qscan++ = '&';
        *qscan++ = 'l';
        *qscan++ = 't';
        *qscan++ = ';';
    }
    else if (c == '>') {
        *qscan++ = '&';
        *qscan++ = 'g';
        *qscan++ = 't';
        *qscan++ = ';';
    }
    else if (c == '&') {
        *qscan++ = '&';
        *qscan++ = 'a';
        *qscan++ = 'm';
        *qscan++ = 'p';
        *qscan++ = ';';
    }
    else if (quotes && c == '"') {
        *qscan++ = '&';
        *qscan++ = 'q';
        *qscan++ = 'u';
        *qscan++ = 'o';
        *qscan++ = 't';
        *qscan++ = ';';
    }
    else {
        *qscan++ = c;
    }
    }

    *qscan = '\0';
    return qstr;
}

/* how many characters for the given integer? */
#define AP_XML_NS_LEN(ns) ((ns) < 10 ? 1 : (ns) < 100 ? 2 : (ns) < 1000 ? 3 : \
             (ns) < 10000 ? 4 : (ns) < 100000 ? 5 : \
             (ns) < 1000000 ? 6 : (ns) < 10000000 ? 7 : \
             (ns) < 100000000 ? 8 : (ns) < 1000000000 ? 9 : 10)

static apr_size_t text_size(const ap_text *t)
{
    apr_size_t size = 0;

    for (; t; t = t->next)
    size += strlen(t->text);
    return size;
}

static apr_size_t elem_size(const ap_xml_elem *elem, int style,
                            apr_array_header_t *namespaces, int *ns_map)
{
    apr_size_t size;

    if (style == AP_XML_X2T_FULL || style == AP_XML_X2T_FULL_NS_LANG) {
    const ap_xml_attr *attr;

    size = 0;

    if (style == AP_XML_X2T_FULL_NS_LANG) {
        int i;

        /*
        ** The outer element will contain xmlns:ns%d="%s" attributes
        ** and an xml:lang attribute, if applicable.
        */

        for (i = namespaces->nelts; i--;) {
        /* compute size of: ' xmlns:ns%d="%s"' */
        size += (9 + AP_XML_NS_LEN(i) + 2 +
             strlen(AP_XML_GET_URI_ITEM(namespaces, i)) + 1);
        }

        if (elem->lang != NULL) {
        /* compute size of: ' xml:lang="%s"' */
        size += 11 + strlen(elem->lang) + 1;
        }
    }

    if (elem->ns == AP_XML_NS_NONE) {
        /* compute size of: <%s> */
        size += 1 + strlen(elem->name) + 1;
    }
    else {
        int ns = ns_map ? ns_map[elem->ns] : elem->ns;

        /* compute size of: <ns%d:%s> */
        size += 3 + AP_XML_NS_LEN(ns) + 1 + strlen(elem->name) + 1;
    }

    if (AP_XML_ELEM_IS_EMPTY(elem)) {
        /* insert a closing "/" */
        size += 1;
    }
    else {
        /*
         * two of above plus "/":
         *     <ns%d:%s> ... </ns%d:%s>
         * OR  <%s> ... </%s>
         */
        size = 2 * size + 1;
    }

    for (attr = elem->attr; attr; attr = attr->next) {
        if (attr->ns == AP_XML_NS_NONE) {
        /* compute size of: ' %s="%s"' */
        size += 1 + strlen(attr->name) + 2 + strlen(attr->value) + 1;
        }
        else {
        /* compute size of: ' ns%d:%s="%s"' */
        size += 3 + AP_XML_NS_LEN(attr->ns) + 1 + strlen(attr->name) + 2 + strlen(attr->value) + 1;
        }
    }

    /*
    ** If the element has an xml:lang value that is *different* from
    ** its parent, then add the thing in: ' xml:lang="%s"'.
    **
    ** NOTE: we take advantage of the pointer equality established by
    ** the parsing for "inheriting" the xml:lang values from parents.
    */
    if (elem->lang != NULL &&
        (elem->parent == NULL || elem->lang != elem->parent->lang)) {
        size += 11 + strlen(elem->lang) + 1;
    }
    }
    else if (style == AP_XML_X2T_LANG_INNER) {
    /*
     * This style prepends the xml:lang value plus a null terminator.
     * If a lang value is not present, then we insert a null term.
     */
    size = elem->lang ? strlen(elem->lang) + 1 : 1;
    }
    else
    size = 0;

    size += text_size(elem->first_cdata.first);

    for (elem = elem->first_child; elem; elem = elem->next) {
    /* the size of the child element plus the CDATA that follows it */
    size += (elem_size(elem, AP_XML_X2T_FULL, NULL, ns_map) +
         text_size(elem->following_cdata.first));
    }

    return size;
}

static char *write_text(char *s, const ap_text *t)
{
    for (; t; t = t->next) {
    apr_size_t len = strlen(t->text);
    memcpy(s, t->text, len);
    s += len;
    }
    return s;
}

static char *write_elem(char *s, const ap_xml_elem *elem, int style,
            apr_array_header_t *namespaces, int *ns_map)
{
    const ap_xml_elem *child;
    apr_size_t len;
    int ns;

    if (style == AP_XML_X2T_FULL || style == AP_XML_X2T_FULL_NS_LANG) {
    int empty = AP_XML_ELEM_IS_EMPTY(elem);
    const ap_xml_attr *attr;

    if (elem->ns == AP_XML_NS_NONE) {
        len = sprintf(s, "<%s", elem->name);
    }
    else {
        ns = ns_map ? ns_map[elem->ns] : elem->ns;
        len = sprintf(s, "<ns%d:%s", ns, elem->name);
    }
    s += len;

    for (attr = elem->attr; attr; attr = attr->next) {
        if (attr->ns == AP_XML_NS_NONE)
        len = sprintf(s, " %s=\"%s\"", attr->name, attr->value);
        else
        len = sprintf(s, " ns%d:%s=\"%s\"", attr->ns, attr->name, attr->value);
        s += len;
    }

    /* add the xml:lang value if necessary */
    if (elem->lang != NULL &&
        (style == AP_XML_X2T_FULL_NS_LANG ||
         elem->parent == NULL ||
         elem->lang != elem->parent->lang)) {
        len = sprintf(s, " xml:lang=\"%s\"", elem->lang);
        s += len;
    }

    /* add namespace definitions, if required */
    if (style == AP_XML_X2T_FULL_NS_LANG) {
        int i;

        for (i = namespaces->nelts; i--;) {
        len = sprintf(s, " xmlns:ns%d=\"%s\"", i,
                  AP_XML_GET_URI_ITEM(namespaces, i));
        s += len;
        }
    }

    /* no more to do. close it up and go. */
    if (empty) {
        *s++ = '/';
        *s++ = '>';
        return s;
    }

    /* just close it */
    *s++ = '>';
    }
    else if (style == AP_XML_X2T_LANG_INNER) {
    /* prepend the xml:lang value */
    if (elem->lang != NULL) {
        len = strlen(elem->lang);
        memcpy(s, elem->lang, len);
        s += len;
    }
    *s++ = '\0';
    }

    s = write_text(s, elem->first_cdata.first);

    for (child = elem->first_child; child; child = child->next) {
    s = write_elem(s, child, AP_XML_X2T_FULL, NULL, ns_map);
    s = write_text(s, child->following_cdata.first);
    }

    if (style == AP_XML_X2T_FULL || style == AP_XML_X2T_FULL_NS_LANG) {
    if (elem->ns == AP_XML_NS_NONE) {
        len = sprintf(s, "</%s>", elem->name);
    }
    else {
        ns = ns_map ? ns_map[elem->ns] : elem->ns;
        len = sprintf(s, "</ns%d:%s>", ns, elem->name);
    }
    s += len;
    }

    return s;
}

AP_DECLARE(void) ap_xml_quote_elem(apr_pool_t *p, ap_xml_elem *elem)
{
    ap_text *scan_txt;
    ap_xml_attr *scan_attr;
    ap_xml_elem *scan_elem;

    /* convert the element's text */
    for (scan_txt = elem->first_cdata.first;
     scan_txt != NULL;
     scan_txt = scan_txt->next) {
    scan_txt->text = ap_xml_quote_string(p, scan_txt->text, 0);
    }
    for (scan_txt = elem->following_cdata.first;
     scan_txt != NULL;
     scan_txt = scan_txt->next) {
    scan_txt->text = ap_xml_quote_string(p, scan_txt->text, 0);
    }

    /* convert the attribute values */
    for (scan_attr = elem->attr;
     scan_attr != NULL;
     scan_attr = scan_attr->next) {
    scan_attr->value = ap_xml_quote_string(p, scan_attr->value, 1);
    }

    /* convert the child elements */
    for (scan_elem = elem->first_child;
     scan_elem != NULL;
     scan_elem = scan_elem->next) {
    ap_xml_quote_elem(p, scan_elem);
    }
}

/* convert an element to a text string */
AP_DECLARE(void) ap_xml_to_text(apr_pool_t * p, const ap_xml_elem *elem,
                                int style, apr_array_header_t *namespaces,
                                int *ns_map, const char **pbuf,
                                apr_size_t *psize)
{
    /* get the exact size, plus a null terminator */
    apr_size_t size = elem_size(elem, style, namespaces, ns_map) + 1;
    char *s = apr_palloc(p, size);

    (void) write_elem(s, elem, style, namespaces, ns_map);
    s[size - 1] = '\0';

    *pbuf = s;
    if (psize)
    *psize = size;
}

AP_DECLARE(const char *) ap_xml_empty_elem(apr_pool_t * p,
                                           const ap_xml_elem *elem)
{
    if (elem->ns == AP_XML_NS_NONE) {
    /*
     * The prefix (xml...) is already within the prop name, or
     * the element simply has no prefix.
     */
    return apr_psprintf(p, "<%s/>" DEBUG_CR, elem->name);
    }

    return apr_psprintf(p, "<ns%d:%s/>" DEBUG_CR, elem->ns, elem->name);
}

/* return the URI's (existing) index, or insert it and return a new index */
AP_DECLARE(int) ap_xml_insert_uri(apr_array_header_t *uri_array,
                                  const char *uri)
{
    int i;
    const char **pelt;

    for (i = uri_array->nelts; i--;) {
    if (strcmp(uri, AP_XML_GET_URI_ITEM(uri_array, i)) == 0)
        return i;
    }

    pelt = apr_array_push(uri_array);
    *pelt = uri;        /* assume uri is const or in a pool */
    return uri_array->nelts - 1;
}