/*      Copyright (c) 2007-11, WebThing Ltd

 *      Copyright (c) 2011-, The Apache Software Foundation

 *

 * Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#if defined(WIN32)

#define XML2ENC_DECLARE_EXPORT

#endif

#include <ctype.h>

/* libxml2 */

#include <libxml/encoding.h>

#include "http_protocol.h"

#include "http_config.h"

#include "http_log.h"

#include "apr_strings.h"

#include "apr_xlate.h"

#include "apr_optional.h"

#include "mod_xml2enc.h"

module AP_MODULE_DECLARE_DATA xml2enc_module;

#define BUFLEN 8192

#define BUF_MIN 4096

#define APR_BRIGADE_DO(b,bb) for (b = APR_BRIGADE_FIRST(bb); \

                                  b != APR_BRIGADE_SENTINEL(bb); \

                                  b = APR_BUCKET_NEXT(b))

#define ENC_INITIALISED 0x100

#define ENC_SEEN_EOS 0x200

#define ENC_SKIPTO ENCIO_SKIPTO

#define HAVE_ENCODING(enc) \

        (((enc)!=XML_CHAR_ENCODING_NONE)&&((enc)!=XML_CHAR_ENCODING_ERROR))

/*

 * XXX: Check all those ap_assert()s ans replace those that should not happen

 * XXX: with AP_DEBUG_ASSERT and those that may happen with proper error

 * XXX: handling.

 */

typedef struct {

    xmlCharEncoding xml2enc;

    char* buf;

    apr_size_t bytes;

    apr_xlate_t* convset;

    unsigned int flags;

    apr_off_t bblen;

    apr_bucket_brigade* bbnext;

    apr_bucket_brigade* bbsave;

    const char* encoding;

} xml2ctx;

typedef struct {

    const char* default_charset;

    xmlCharEncoding default_encoding;

    apr_array_header_t* skipto;

} xml2cfg;

typedef struct {

    const char* val;

} tattr;

static ap_regex_t* seek_meta_ctype;

static ap_regex_t* seek_charset;

static apr_status_t xml2enc_filter(request_rec* r, const char* enc,

                                   unsigned int mode)

{

    /* set up a ready-initialised ctx to convert to enc, and insert filter */

    apr_xlate_t* convset; 

    apr_status_t rv;

    unsigned int flags = (mode ^ ENCIO);

    if ((mode & ENCIO) == ENCIO_OUTPUT) {

        rv = apr_xlate_open(&convset, enc, "UTF-8", r->pool);

        flags |= ENC_INITIALISED;

    }

    else if ((mode & ENCIO) == ENCIO_INPUT) {

        rv = apr_xlate_open(&convset, "UTF-8", enc, r->pool);

        flags |= ENC_INITIALISED;

    }

    else if ((mode & ENCIO) == ENCIO_INPUT_CHECKS) {

        convset = NULL;

        rv = APR_SUCCESS; /* we'll initialise later by sniffing */

    }

    else {

        rv = APR_EGENERAL;

        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01426)

                      "xml2enc: bad mode %x", mode);

    }

    if (rv == APR_SUCCESS) {

        xml2ctx* ctx = apr_pcalloc(r->pool, sizeof(xml2ctx));

        ctx->flags = flags;

        if (flags & ENC_INITIALISED) {

            ctx->convset = convset;

            ctx->bblen = BUFLEN;

            ctx->buf = apr_palloc(r->pool, (apr_size_t)ctx->bblen);

        }

        ap_add_output_filter("xml2enc", ctx, r, r->connection);

    }

    else {

        ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01427)

                      "xml2enc: Charset %s not supported.", enc) ;

    }

    return rv;

}

/* This needs to operate only when we're using htmlParser */

/* Different modules may apply different rules here.  Ho, hum.  */

static void fix_skipto(request_rec* r, xml2ctx* ctx)

{

    apr_status_t rv;

    xml2cfg* cfg = ap_get_module_config(r->per_dir_config, &xml2enc_module);

    if ((cfg->skipto != NULL) && (ctx->flags & ENC_SKIPTO)) {

        int found = 0;

        char* p = ap_strchr(ctx->buf, '<');

        tattr* starts = (tattr*) cfg->skipto->elts;

        while (!found && p && *p) {

            int i;

            for (i = 0; i < cfg->skipto->nelts; ++i) {

                if (!strncasecmp(p+1, starts[i].val, strlen(starts[i].val))) {

                    /* found a starting element. Strip all that comes before. */

                    apr_bucket* b;

                    apr_bucket* bstart;

                    rv = apr_brigade_partition(ctx->bbsave, (p-ctx->buf),

                                               &bstart);

                    ap_assert(rv == APR_SUCCESS);

                    while (b = APR_BRIGADE_FIRST(ctx->bbsave), b != bstart) {

                        apr_bucket_delete(b);

                    }

                    ctx->bytes -= (p-ctx->buf);

                    ctx->buf = p ;

                    found = 1;

                    ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01428)

                                  "Skipped to first <%s> element",

                                  starts[i].val) ;

                    break;

                }

            }

            p = ap_strchr(p+1, '<');

        }

        if (p == NULL) {

            ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r, APLOGNO(01429)

                          "Failed to find start of recognised HTML!");

        }

    }

}

static void sniff_encoding(request_rec* r, xml2ctx* ctx)

{

    xml2cfg* cfg = NULL; /* initialise to shut compiler warnings up */

    char* p ;

    apr_bucket* cutb;

    apr_bucket* cute;

    apr_bucket* b;

    ap_regmatch_t match[2] ;

    apr_status_t rv;

    const char* ctype = r->content_type;

    if (ctype) {

        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01430)

                      "Content-Type is %s", ctype) ;

        /* If we've got it in the HTTP headers, there's nothing to do */

        if (ctype && (p = ap_strcasestr(ctype, "charset=") , p != NULL)) {

            p += 8 ;

            if (ctx->encoding = apr_pstrndup(r->pool, p, strcspn(p, " ;") ),

                ctx->encoding) {

                ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, APLOGNO(01431)

                              "Got charset %s from HTTP headers", ctx->encoding) ;

                ctx->xml2enc = xmlParseCharEncoding(ctx->encoding);

            }

        }

    }

    /* to sniff, first we look for BOM */

    if (ctx->xml2enc == XML_CHAR_ENCODING_NONE) {

        ctx->xml2enc = xmlDetectCharEncoding((const xmlChar*)ctx->buf,

                                             ctx->bytes); 

        if (HAVE_ENCODING(ctx->xml2enc)) {

            ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, APLOGNO(01432)

                          "Got charset from XML rules.") ;

            ctx->encoding = xmlGetCharEncodingName(ctx->xml2enc);

        }

    }

    /* If none of the above, look for a META-thingey */

    /* also we're probably about to invalidate it, so we remove it. */

    if (ap_regexec(seek_meta_ctype, ctx->buf, 1, match, 0) == 0 ) {

        /* get markers on the start and end of the match */

        rv = apr_brigade_partition(ctx->bbsave, match[0].rm_eo, &cute);

        ap_assert(rv == APR_SUCCESS);

        rv = apr_brigade_partition(ctx->bbsave, match[0].rm_so, &cutb);

        ap_assert(rv == APR_SUCCESS);

        /* now set length of useful buf for start-of-data hooks */

        ctx->bytes = match[0].rm_so;

        if (ctx->encoding == NULL) {

            p = apr_pstrndup(r->pool, ctx->buf + match[0].rm_so,

                             match[0].rm_eo - match[0].rm_so) ;

            if (ap_regexec(seek_charset, p, 2, match, 0) == 0) {

                if (ctx->encoding = apr_pstrndup(r->pool, p+match[1].rm_so,

                                               match[1].rm_eo - match[1].rm_so),

                    ctx->encoding) {

                    ctx->xml2enc = xmlParseCharEncoding(ctx->encoding);

                    if (HAVE_ENCODING(ctx->xml2enc))

                        ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, APLOGNO(01433)

                                      "Got charset %s from HTML META", ctx->encoding) ;

                }

            }

        }

        /* cut out the <meta> we're invalidating */

        while (cutb != cute) {

            b = APR_BUCKET_NEXT(cutb);

            apr_bucket_delete(cutb);

            cutb = b;

        }

        /* and leave a string */

        ctx->buf[ctx->bytes] = 0;

    }

    /* either it's set to something we found or it's still the default */

    /* Aaargh!  libxml2 has undocumented <META-crap> support.  So this fails

     * if metafix is not active.  Have to make it conditional.

     *

     * No, that means no-metafix breaks things.  Deal immediately with

     * this particular instance of metafix.

     */

    if (!HAVE_ENCODING(ctx->xml2enc)) {

        cfg = ap_get_module_config(r->per_dir_config, &xml2enc_module);

        if (!ctx->encoding) {

            ctx->encoding = cfg->default_charset?cfg->default_charset:"ISO-8859-1";

        }

        /* Unsupported charset. Can we get (iconv) support through apr_xlate? */

        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01434)

                      "Charset %s not supported by libxml2; trying apr_xlate",

                      ctx->encoding);

        if (apr_xlate_open(&ctx->convset, "UTF-8", ctx->encoding, r->pool)

            == APR_SUCCESS) {

            ctx->xml2enc = XML_CHAR_ENCODING_UTF8 ;

        } else {

            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01435)

                          "Charset %s not supported.  Consider aliasing it?",

                          ctx->encoding) ;

        }

    }

    if (!HAVE_ENCODING(ctx->xml2enc)) {

        /* Use configuration default as a last resort */

        ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r, APLOGNO(01436)

                  "No usable charset information; using configuration default");

        ctx->xml2enc = (cfg->default_encoding == XML_CHAR_ENCODING_NONE)

                        ? XML_CHAR_ENCODING_8859_1 : cfg->default_encoding ;

    }

    if (ctype && ctx->encoding) {

        if (ap_regexec(seek_charset, ctype, 2, match, 0)) {

            r->content_type = apr_pstrcat(r->pool, ctype, ";charset=utf-8",

                                          NULL);

        } else {

            char* str = apr_palloc(r->pool, strlen(r->content_type) + 13

                                   - (match[0].rm_eo - match[0].rm_so) + 1);

            memcpy(str, r->content_type, match[1].rm_so);

            memcpy(str + match[1].rm_so, "utf-8", 5);

            strcpy(str + match[1].rm_so + 5, r->content_type+match[1].rm_eo);

            r->content_type = str;

        }

    }

}

static apr_status_t xml2enc_filter_init(ap_filter_t* f)

{

    xml2ctx* ctx;

    if (!f->ctx) {

        xml2cfg* cfg = ap_get_module_config(f->r->per_dir_config,

                                            &xml2enc_module);

        f->ctx = ctx = apr_pcalloc(f->r->pool, sizeof(xml2ctx));

        ctx->xml2enc = XML_CHAR_ENCODING_NONE;

        if (cfg->skipto != NULL) {

            ctx->flags |= ENC_SKIPTO;

        }

    }

    return APR_SUCCESS;

}

static apr_status_t xml2enc_ffunc(ap_filter_t* f, apr_bucket_brigade* bb)

{

    xml2ctx* ctx = f->ctx;

    apr_status_t rv;

    apr_bucket* b;

    apr_bucket* bstart;

    apr_size_t insz = 0;

    int pending_meta = 0;

    char *ctype;

    char *p;

    if (!ctx || !f->r->content_type) {

        /* log error about configuring this */

        ap_remove_output_filter(f);

        return ap_pass_brigade(f->next, bb) ;

    }

    ctype = apr_pstrdup(f->r->pool, f->r->content_type);

    for (p = ctype; *p; ++p)

        if (isupper(*p))

            *p = tolower(*p);

    /* only act if starts-with "text/" or contains "xml" */

    if (strncmp(ctype, "text/", 5) && !strstr(ctype, "xml"))  {

        ap_remove_output_filter(f);

        return ap_pass_brigade(f->next, bb) ;

    }

    if (ctx->bbsave == NULL) {

        ctx->bbsave = apr_brigade_create(f->r->pool,

                                         f->r->connection->bucket_alloc);

    }

    /* append to any data left over from last time */

    APR_BRIGADE_CONCAT(ctx->bbsave, bb);

    if (!(ctx->flags & ENC_INITIALISED)) {

        /* some kind of initialisation required */

        /* Turn all this off when post-processing */

        /* if we don't have enough data to sniff but more's to come, wait */

        apr_brigade_length(ctx->bbsave, 0, &ctx->bblen);

        if ((ctx->bblen < BUF_MIN) && (ctx->bblen != -1)) {

            APR_BRIGADE_DO(b, ctx->bbsave) {

                if (APR_BUCKET_IS_EOS(b)) {

                    ctx->flags |= ENC_SEEN_EOS;

                    break;

                }

            }

            if (!(ctx->flags & ENC_SEEN_EOS)) {

                /* not enough data to sniff.  Wait for more */

                APR_BRIGADE_DO(b, ctx->bbsave) {

                    rv = apr_bucket_setaside(b, f->r->pool);

                    ap_assert(rv == APR_SUCCESS);

                }

                return APR_SUCCESS;

            }

        }

        if (ctx->bblen == -1) {

            ctx->bblen = BUFLEN-1;

        }

        /* flatten it into a NULL-terminated string */

        ctx->buf = apr_palloc(f->r->pool, (apr_size_t)(ctx->bblen+1));

        ctx->bytes = (apr_size_t)ctx->bblen;

        rv = apr_brigade_flatten(ctx->bbsave, ctx->buf, &ctx->bytes);

        ap_assert(rv == APR_SUCCESS);

        ctx->buf[ctx->bytes] = 0;

        sniff_encoding(f->r, ctx);

        /* FIXME: hook here for rewriting start-of-data? */

        /* nah, we only have one action here - call it inline */

        fix_skipto(f->r, ctx);

        /* we might change the Content-Length, so let's force its re-calculation */

        apr_table_unset(f->r->headers_out, "Content-Length");

        /* consume the data we just sniffed */

        /* we need to omit any <meta> we just invalidated */

        ctx->flags |= ENC_INITIALISED;

        ap_set_module_config(f->r->request_config, &xml2enc_module, ctx);

    }

    if (ctx->bbnext == NULL) {

        ctx->bbnext = apr_brigade_create(f->r->pool,

                                         f->r->connection->bucket_alloc);

    }

    if (!ctx->convset) {

        rv = ap_pass_brigade(f->next, ctx->bbsave);

        apr_brigade_cleanup(ctx->bbsave);

        ap_remove_output_filter(f);

        return rv;

    }

    /* move the data back to bb */

    APR_BRIGADE_CONCAT(bb, ctx->bbsave);

    while (!APR_BRIGADE_EMPTY(bb)) {

        b = APR_BRIGADE_FIRST(bb);

        ctx->bytes = 0;

        if (APR_BUCKET_IS_METADATA(b)) {

            APR_BUCKET_REMOVE(b);

            APR_BRIGADE_INSERT_TAIL(ctx->bbnext, b);

            /* Besides FLUSH, aggregate meta buckets to send them at

             * once below. This resource filter is over on EOS.

             */

            pending_meta = 1;

            if (APR_BUCKET_IS_EOS(b)) {

                ap_remove_output_filter(f);

                APR_BRIGADE_CONCAT(ctx->bbnext, bb);

            }

            else if (!APR_BUCKET_IS_FLUSH(b)) {

                continue;

            }

        }

        if (pending_meta) {

            pending_meta = 0;

            /* passing meta bucket down the chain */

            rv = ap_pass_brigade(f->next, ctx->bbnext);

            apr_brigade_cleanup(ctx->bbnext);

            if (rv != APR_SUCCESS) {

                return rv;

            }

            continue;

        }

        /* data bucket */

        {

            char* buf;

            apr_size_t bytes = 0;

            char fixbuf[BUFLEN];

            apr_bucket* bdestroy = NULL;

            if (insz > 0) { /* we have dangling data.  Flatten it. */

                buf = fixbuf;

                bytes = BUFLEN;

                rv = apr_brigade_flatten(bb, buf, &bytes);

                ap_assert(rv == APR_SUCCESS);

                if (bytes == insz) {

                    /* this is only what we've already tried to convert.

                     * The brigade is exhausted.

                     * Save remaining data for next time round

                     */

                    ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, f->r, APLOGNO(01437)

                                  "xml2enc: Setting aside %" APR_SIZE_T_FMT

                                  " unconverted bytes", bytes);

                    rv = ap_fflush(f->next, ctx->bbnext);

                    APR_BRIGADE_CONCAT(ctx->bbsave, bb);

                    APR_BRIGADE_DO(b, ctx->bbsave) {

                        ap_assert(apr_bucket_setaside(b, f->r->pool)

                                  == APR_SUCCESS);

                    }

                    return rv;

                }

                /* remove the data we've just read */

                rv = apr_brigade_partition(bb, bytes, &bstart);

                while (b = APR_BRIGADE_FIRST(bb), b != bstart) {

                    apr_bucket_delete(b);

                }

                ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, f->r, APLOGNO(01438)

                              "xml2enc: consuming %" APR_SIZE_T_FMT

                              " bytes flattened", bytes);

            }

            else {

                rv = apr_bucket_read(b, (const char**)&buf, &bytes,

                                     APR_BLOCK_READ);

                APR_BUCKET_REMOVE(b);

                bdestroy = b;  /* can't destroy until finished with the data */

                ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, f->r, APLOGNO(01439)

                              "xml2enc: consuming %" APR_SIZE_T_FMT

                              " bytes from bucket", bytes);

            }

            /* OK, we've got some input we can use in [buf,bytes] */

            if (rv == APR_SUCCESS) {

                apr_size_t consumed;

                xml2enc_run_preprocess(f, &buf, &bytes);

                consumed = insz = bytes;

                while (insz > 0) {

                    apr_status_t rv2;

                    if (ctx->bytes == ctx->bblen) {

                        /* nothing was converted last time!

                         * break out of this loop! 

                         */

                        b = apr_bucket_transient_create(buf+(bytes - insz), insz,

                                                        bb->bucket_alloc);

                        APR_BRIGADE_INSERT_HEAD(bb, b);

                        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, f->r, APLOGNO(01440)

                                      "xml2enc: reinserting %" APR_SIZE_T_FMT

                                      " unconsumed bytes from bucket", insz);

                        break;

                    }

                    ctx->bytes = (apr_size_t)ctx->bblen;

                    rv = apr_xlate_conv_buffer(ctx->convset, buf+(bytes - insz),

                                               &insz, ctx->buf, &ctx->bytes);

                    ap_log_rerror(APLOG_MARK, APLOG_DEBUG, rv, f->r, APLOGNO(01441)

                                  "xml2enc: converted %" APR_SIZE_T_FMT

                                  "/%" APR_OFF_T_FMT " bytes", consumed - insz,

                                  ctx->bblen - ctx->bytes);

                    consumed = insz;

                    rv2 = ap_fwrite(f->next, ctx->bbnext, ctx->buf,

                                    (apr_size_t)ctx->bblen - ctx->bytes);

                    if (rv2 != APR_SUCCESS) {

                        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, rv2, f->r, APLOGNO(01442)

                                      "ap_fwrite failed");

                        return rv2;

                    }

                    switch (rv) {

                    case APR_SUCCESS:

                        continue;

                    case APR_EINCOMPLETE:

                        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, f->r, APLOGNO(01443)

                                      "INCOMPLETE");

                        continue;     /* If outbuf too small, go round again.

                                       * If it was inbuf, we'll break out when

                                       * we test ctx->bytes == ctx->bblen

                                       */

                    case APR_EINVAL: /* try skipping one bad byte */

                        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, f->r, APLOGNO(01444)

                                   "Skipping invalid byte(s) in input stream!");

                        --insz;

                        continue;

                    default:

                        /* Erk!  What's this?

                         * Bail out, flush, and hope to eat the buf raw

                         */

                        ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, f->r, APLOGNO(01445)

                                      "Failed to convert input; trying it raw") ;

                        ctx->convset = NULL;

                        rv = ap_fflush(f->next, ctx->bbnext);

                        if (rv != APR_SUCCESS)

                            ap_log_rerror(APLOG_MARK, APLOG_DEBUG, rv, f->r, APLOGNO(01446)

                                          "ap_fflush failed");

                        apr_brigade_cleanup(ctx->bbnext);

                    }

                }

            } else {

                ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, f->r, APLOGNO(01447)

                              "xml2enc: error reading data") ;

            }

            if (bdestroy)

                apr_bucket_destroy(bdestroy);

            if (rv != APR_SUCCESS)

                return rv;

        }

    }

    if (pending_meta) {

        /* passing pending meta bucket down the chain before leaving */

        rv = ap_pass_brigade(f->next, ctx->bbnext);

        apr_brigade_cleanup(ctx->bbnext);

        if (rv != APR_SUCCESS) {

            return rv;

        }

    }

    return APR_SUCCESS;

}

static apr_status_t xml2enc_charset(request_rec* r, xmlCharEncoding* encp,

                                    const char** encoding)

{

    xml2ctx* ctx = ap_get_module_config(r->request_config, &xml2enc_module);

    if (!ctx || !(ctx->flags & ENC_INITIALISED)) {

        return APR_EAGAIN;

    }

    *encp = ctx->xml2enc;

    *encoding = ctx->encoding;

    return HAVE_ENCODING(ctx->xml2enc) ? APR_SUCCESS : APR_EGENERAL;

}

#define PROTO_FLAGS AP_FILTER_PROTO_CHANGE|AP_FILTER_PROTO_CHANGE_LENGTH

static void xml2enc_hooks(apr_pool_t* pool)

{

    ap_register_output_filter_protocol("xml2enc", xml2enc_ffunc,

                                       xml2enc_filter_init,

                                       AP_FTYPE_RESOURCE, PROTO_FLAGS);

    APR_REGISTER_OPTIONAL_FN(xml2enc_filter);

    APR_REGISTER_OPTIONAL_FN(xml2enc_charset);

    seek_meta_ctype = ap_pregcomp(pool,

                       "(<meta[^>]*http-equiv[ \t\r\n='\"]*content-type[^>]*>)",

                                  AP_REG_EXTENDED|AP_REG_ICASE) ;

    seek_charset = ap_pregcomp(pool, "charset=([A-Za-z0-9_-]+)",

                               AP_REG_EXTENDED|AP_REG_ICASE) ;

}

static const char* set_alias(cmd_parms* cmd, void* CFG,

                             const char* charset, const char* alias)

{

    const char* errmsg = ap_check_cmd_context(cmd, GLOBAL_ONLY);

    if (errmsg != NULL)

        return errmsg ;

    else if (xmlAddEncodingAlias(charset, alias) == 0)

        return NULL;

    else

        return "Error setting charset alias";

}

static const char* set_default(cmd_parms* cmd, void* CFG, const char* charset)

{

    xml2cfg* cfg = CFG;

    cfg->default_charset = charset;

    cfg->default_encoding = xmlParseCharEncoding(charset);

    switch(cfg->default_encoding) {

    case XML_CHAR_ENCODING_NONE:

        return "Default charset not found";

    case XML_CHAR_ENCODING_ERROR:

        return "Invalid or unsupported default charset";

    default:

        return NULL;

    }

}

static const char* set_skipto(cmd_parms* cmd, void* CFG, const char* arg)

{

    tattr* attr;

    xml2cfg* cfg = CFG;

    if (cfg->skipto == NULL)

        cfg->skipto = apr_array_make(cmd->pool, 4, sizeof(tattr));

    attr = apr_array_push(cfg->skipto) ;

    attr->val = arg;

    return NULL;

}

static const command_rec xml2enc_cmds[] = {

    AP_INIT_TAKE1("xml2EncDefault", set_default, NULL, OR_ALL,

                  "Usage: xml2EncDefault charset"),

    AP_INIT_ITERATE2("xml2EncAlias", set_alias, NULL, RSRC_CONF,

                     "EncodingAlias charset alias [more aliases]"),

    AP_INIT_ITERATE("xml2StartParse", set_skipto, NULL, OR_ALL,

                    "Ignore anything in front of the first of these elements"),

    { NULL }

};

static void* xml2enc_config(apr_pool_t* pool, char* x)

{

    xml2cfg* ret = apr_pcalloc(pool, sizeof(xml2cfg));

    ret->default_encoding = XML_CHAR_ENCODING_NONE ;

    return ret;

}

static void* xml2enc_merge(apr_pool_t* pool, void* BASE, void* ADD)

{

    xml2cfg* base = BASE;

    xml2cfg* add = ADD;

    xml2cfg* ret = apr_pcalloc(pool, sizeof(xml2cfg));

    ret->default_encoding = (add->default_encoding == XML_CHAR_ENCODING_NONE)

                          ? base->default_encoding : add->default_encoding ;

    ret->default_charset = add->default_charset

                         ? add->default_charset : base->default_charset;

    ret->skipto = add->skipto ? add->skipto : base->skipto;

    return ret;

}

AP_DECLARE_MODULE(xml2enc) = {

    STANDARD20_MODULE_STUFF,

    xml2enc_config,

    xml2enc_merge,

    NULL,

    NULL,

    xml2enc_cmds,

    xml2enc_hooks

};

APR_IMPLEMENT_OPTIONAL_HOOK_RUN_ALL(xml2enc, XML2ENC, int, preprocess,

                      (ap_filter_t *f, char** bufp, apr_size_t* bytesp),

                      (f, bufp, bytesp), OK, DECLINED)