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/* htmlparse.cc: simple HTML parser for omega indexer
*
* Copyright 1999,2000,2001 BrightStation PLC
* Copyright 2001 Ananova Ltd
* Copyright 2002,2006,2007,2008,2009,2010,2011,2012,2015,2016,2018 Olly Betts
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
* USA
*/
#include <config.h>
#include "htmlparse.h"
#include <xapian.h>
#include "keyword.h"
#include "namedents.h"
#include "stringutils.h"
#include "utf8convert.h"
#include <algorithm>
#include <cctype>
#include <cstring>
#include <cstdio>
#include <cstdlib>
using namespace std;
// HTML5 legacy compatibility doctype.
#define HTML5_LEGACY_COMPAT "about:legacy-compat"
#define HTML5_LEGACY_COMPAT_LEN CONST_STRLEN(HTML5_LEGACY_COMPAT)
static inline void
lowercase_string(string &str)
{
for (string::iterator i = str.begin(); i != str.end(); ++i) {
*i = C_tolower(*i);
}
}
static inline bool
p_nottag(char c)
{
// ':' for XML namespaces.
return !C_isalnum(c) && c != '.' && c != '-' && c != ':';
}
static inline bool
p_whitespacegt(char c)
{
return C_isspace(c) || c == '>';
}
static inline bool
p_whitespaceeqgt(char c)
{
return C_isspace(c) || c == '=' || c == '>';
}
bool
HtmlParser::get_parameter(const string & param, string & value) const
{
map<string, string>::const_iterator i = parameters.find(param);
if (i == parameters.end()) return false;
value = i->second;
return true;
}
// UTF-8 encoded entity is always <= the entity itself in length, even if the
// trailing ';' is missing - for numeric (decimal and hex) entities:
//
// <= UTF-8 &#<..> &#x<..>
// U+007F 1 5 5
// U+07FF 2 6 6
// U+FFFF 3 7 7
// U+1FFFFF 4 9 9
// U+3FFFFFF 5 10 10
// U+7FFFFFFF 6 12 11
//
// Also true for named entities. This means we can work in-place within the
// string.
void
HtmlParser::decode_entities(string &s)
{
string::iterator out = s.begin();
string::iterator in = out;
string::iterator amp = in;
while ((amp = find(amp, s.end(), '&')) != s.end()) {
unsigned int val = 0;
string::iterator end, p = amp + 1;
if (p != s.end() && *p == '#') {
++p;
if (p != s.end() && (*p == 'x' || *p == 'X')) {
// hex
while (++p != s.end() && C_isxdigit(*p)) {
val = (val << 4) | hex_digit(*p);
}
end = p;
} else {
// number
while (p != s.end() && C_isdigit(*p)) {
val = val * 10 + (*p - '0');
++p;
}
end = p;
}
} else {
end = find_if(p, s.end(), C_isnotalnum);
int k = keyword2(tab, s.data() + (p - s.begin()), end - p);
if (k >= 0) val = named_ent_codepoint[k];
}
if (end != s.end() && *end == ';') ++end;
if (val) {
if (in != out) {
out = copy(in, amp, out);
} else {
out = amp;
}
in = end;
if (val < 0x80) {
*out++ = char(val);
} else {
// Convert unicode value val to UTF-8.
char seq[4];
unsigned len = Xapian::Unicode::nonascii_to_utf8(val, seq);
out = copy(seq, seq + len, out);
}
}
amp = end;
}
if (in != out) {
s.erase(out, in);
}
}
void
HtmlParser::parse(const string &body)
{
in_script = false;
parameters.clear();
string::const_iterator start = body.begin();
while (true) {
// Skip through until we find an HTML tag, a comment, or the end of
// document. Ignore isolated occurrences of '<' which don't start
// a tag or comment.
string::const_iterator p = start;
while (true) {
p = find(p, body.end(), '<');
if (p == body.end()) break;
unsigned char ch = *(p + 1);
// Tag, closing tag, or comment (or SGML declaration).
if ((!in_script && C_isalpha(ch)) || ch == '/' || ch == '!') break;
if (ch == '?') {
// PHP code or XML declaration.
// XML declaration is only valid at the start of the first line.
// FIXME: need to deal with BOMs...
if (p != body.begin() || body.size() < 20) break;
// XML declaration looks something like this:
// <?xml version="1.0" encoding="UTF-8"?>
if (p[2] != 'x' || p[3] != 'm' || p[4] != 'l') break;
if (strchr(" \t\r\n", p[5]) == NULL) break;
string::const_iterator decl_end = find(p + 6, body.end(), '?');
if (decl_end == body.end()) break;
// Default charset for XML is UTF-8.
charset = "utf-8";
string decl(p + 6, decl_end);
size_t enc = decl.find("encoding");
if (enc == string::npos) break;
enc = decl.find_first_not_of(" \t\r\n", enc + 8);
if (enc == string::npos || enc == decl.size()) break;
if (decl[enc] != '=') break;
enc = decl.find_first_not_of(" \t\r\n", enc + 1);
if (enc == string::npos || enc == decl.size()) break;
if (decl[enc] != '"' && decl[enc] != '\'') break;
char quote = decl[enc++];
size_t enc_end = decl.find(quote, enc);
if (enc != string::npos)
charset.assign(decl, enc, enc_end - enc);
break;
}
++p;
}
// Process text up to start of tag.
if (p > start) {
string text(body, start - body.begin(), p - start);
convert_to_utf8(text, charset);
decode_entities(text);
process_text(text);
}
if (p == body.end()) break;
start = p + 1;
if (start == body.end()) break;
if (*start == '!') {
if (++start == body.end()) break;
// Comment, SGML declaration, or HTML5 DTD.
char first_ch = *start;
if (++start == body.end()) break;
if (first_ch == '-' && *start == '-') {
++start;
string::const_iterator close = find(start, body.end(), '>');
// An unterminated comment swallows rest of document
// (like Netscape, but unlike MSIE IIRC)
if (close == body.end()) break;
p = close;
// look for -->
while (p != body.end() && (*(p - 1) != '-' || *(p - 2) != '-'))
p = find(p + 1, body.end(), '>');
if (p != body.end()) {
// Check for htdig's "ignore this bit" comments.
if (p - start == CONST_STRLEN("htdig_noindex") + 2 &&
memcmp(&*start, "htdig_noindex",
CONST_STRLEN("htdig_noindex")) == 0) {
auto i = body.find("<!--/htdig_noindex-->",
p + 1 - body.begin());
if (i == string::npos) break;
start = body.begin() + i +
CONST_STRLEN("<!--/htdig_noindex-->");
continue;
}
// Check for udmcomment (similar to htdig's)
if (p - start == CONST_STRLEN("UdmComment") + 2 &&
memcmp(&*start, "UdmComment",
CONST_STRLEN("UdmComment")) == 0) {
auto i = body.find("<!--/UdmComment-->",
p + 1 - body.begin());
if (i == string::npos) break;
start = body.begin() + i +
CONST_STRLEN("<!--/UdmComment-->");
continue;
}
// If we found --> skip to there.
start = p;
} else {
// Otherwise skip to the first > we found (as Netscape does).
start = close;
}
} else if (first_ch == '[' &&
body.size() - (start - body.begin()) > 6 &&
body.compare(start - body.begin(), 6, "CDATA[", 6) == 0) {
start += 6;
string::size_type b = start - body.begin();
string::size_type i;
i = body.find("]]>", b);
string text(body, b, i - b);
convert_to_utf8(text, charset);
process_text(text);
if (i == string::npos) break;
start = body.begin() + i + 2;
} else if (C_tolower(first_ch) == 'd' &&
body.end() - start > 6 &&
C_tolower(start[0]) == 'o' &&
C_tolower(start[1]) == 'c' &&
C_tolower(start[2]) == 't' &&
C_tolower(start[3]) == 'y' &&
C_tolower(start[4]) == 'p' &&
C_tolower(start[5]) == 'e' &&
C_isspace(start[6])) {
// DOCTYPE declaration.
start += 7;
while (start != body.end() && C_isspace(*start)) {
++start;
}
if (start == body.end()) break;
if (body.end() - start >= 5 &&
C_tolower(start[0]) == 'h' &&
C_tolower(start[1]) == 't' &&
C_tolower(start[2]) == 'm' &&
C_tolower(start[3]) == 'l' &&
(start[4] == '>' || C_isspace(start[4]))) {
start += 4;
// HTML doctype.
while (start != body.end() && C_isspace(*start)) {
++start;
}
if (start == body.end()) break;
if (*start == '>') {
// <!DOCTYPE html>
// Default charset for HTML5 is UTF-8.
charset = "utf-8";
}
} else if (body.end() - start >= 29 &&
C_tolower(start[0]) == 's' &&
C_tolower(start[1]) == 'y' &&
C_tolower(start[2]) == 's' &&
C_tolower(start[3]) == 't' &&
C_tolower(start[4]) == 'e' &&
C_tolower(start[5]) == 'm' &&
C_isspace(start[6])) {
start += 7;
while (start != body.end() && C_isspace(*start)) {
++start;
}
size_t left = body.end() - start;
if (left >= HTML5_LEGACY_COMPAT_LEN + 3 &&
(*start == '\'' || *start == '"') &&
start[HTML5_LEGACY_COMPAT_LEN + 1] == *start &&
body.compare(start - body.begin() + 1,
HTML5_LEGACY_COMPAT_LEN,
HTML5_LEGACY_COMPAT,
HTML5_LEGACY_COMPAT_LEN) == 0) {
// HTML5 legacy compatibility doctype:
// <!DOCTYPE html SYSTEM "about:legacy-compat">
start += HTML5_LEGACY_COMPAT_LEN + 2;
// Default charset for HTML5 is UTF-8.
charset = "utf-8";
}
}
start = find(start - 1, body.end(), '>');
if (start == body.end()) break;
} else {
// Some other SGML declaration - ignore it.
start = find(start - 1, body.end(), '>');
if (start == body.end()) break;
}
++start;
} else if (*start == '?') {
if (++start == body.end()) break;
// PHP - swallow until ?> or EOF
start = find(start + 1, body.end(), '>');
// look for ?>
while (start != body.end() && *(start - 1) != '?')
start = find(start + 1, body.end(), '>');
// unterminated PHP swallows rest of document (rather arbitrarily
// but it avoids polluting the database when things go wrong)
if (start != body.end()) ++start;
} else {
// opening or closing tag
int closing = 0;
if (*start == '/') {
closing = 1;
start = find_if(start + 1, body.end(), C_isnotspace);
}
p = start;
start = find_if(start, body.end(), p_nottag);
string tag(body, p - body.begin(), start - p);
// convert tagname to lowercase
lowercase_string(tag);
if (closing) {
if (!closing_tag(tag))
return;
if (in_script && tag == "script") in_script = false;
/* ignore any bogus parameters on closing tags */
p = find(start, body.end(), '>');
if (p == body.end()) break;
start = p + 1;
} else {
bool empty_element = false;
// FIXME: parse parameters lazily.
while (start < body.end() && *start != '>') {
string name, value;
p = find_if(start, body.end(), p_whitespaceeqgt);
size_t name_len = p - start;
if (name_len == 1) {
if (*start == '/' && p < body.end() && *p == '>') {
// E.g. <tag foo="bar" />
start = p;
empty_element = true;
break;
}
}
name.assign(body, start - body.begin(), name_len);
p = find_if(p, body.end(), C_isnotspace);
start = p;
if (start != body.end() && *start == '=') {
start = find_if(start + 1, body.end(), C_isnotspace);
p = body.end();
int quote = *start;
if (quote == '"' || quote == '\'') {
++start;
p = find(start, body.end(), quote);
}
if (p == body.end()) {
// unquoted or no closing quote
p = find_if(start, body.end(), p_whitespacegt);
}
value.assign(body, start - body.begin(), p - start);
start = find_if(p, body.end(), C_isnotspace);
if (!name.empty()) {
// convert parameter name to lowercase
lowercase_string(name);
// in case of multiple entries, use the first
// (as Netscape does)
parameters.insert(make_pair(name, value));
}
}
}
#if 0
cout << "<" << tag;
map<string, string>::const_iterator x;
for (x = parameters.begin(); x != parameters.end(); ++x) {
cout << " " << x->first << "=\"" << x->second << "\"";
}
cout << ">\n";
#endif
if (!opening_tag(tag))
return;
parameters.clear();
if (empty_element) {
if (!closing_tag(tag))
return;
}
// In <script> tags we ignore opening tags to avoid problems
// with "a<b".
if (tag == "script") in_script = true;
if (start != body.end() && *start == '>') ++start;
}
}
}
}
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