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genode/repos/base/include/util/xml_generator.h
Emery Hemingway b5bd6e0114 Write abritrary printable objects into Xml_generator 
Fix #3161
2019-02-19 11:12:12 +01:00

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/*
* \brief Utility for generating XML
* \author Norman Feske
* \date 2014-01-07
*/
/*
* Copyright (C) 2014-2017 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
*/
#ifndef _INCLUDE__UTIL__XML_GENERATOR_H_
#define _INCLUDE__UTIL__XML_GENERATOR_H_
#include <util/string.h>
#include <util/print_lines.h>
#include <base/snprintf.h>
namespace Genode { class Xml_generator; }
class Genode::Xml_generator
{
public:
/**
* Exception type
*/
class Buffer_exceeded { };
private:
/**
* Buffer descriptor where the XML output goes to
*
* All 'append' methods may throw a 'Buffer_exceeded' exception.
*/
class Out_buffer
{
private:
char *_dst;
size_t _capacity;
size_t _used = 0;
void _check_advance(size_t const len) const {
if (_used + len > _capacity)
throw Buffer_exceeded(); }
public:
Out_buffer(char *dst, size_t capacity)
: _dst(dst), _capacity(capacity) { }
void advance(size_t const len)
{
_check_advance(len);
_used += len;
}
void undo_append(size_t const len) {
_used = len < _used ? _used - len : 0; }
/**
* Append character
*/
void append(char const c)
{
_check_advance(1);
_dst[_used] = c;
advance(1);
}
/**
* Append character 'n' times
*/
void append(char const c, size_t n) {
for (; n--; append(c)); }
/**
* Append character buffer
*/
void append(char const *src, size_t len) {
for (; len--; append(*src++)); }
/**
* Append null-terminated string
*/
void append(char const *src) { append(src, strlen(src)); }
/**
* Append character, sanitize it if needed
*/
void append_sanitized(char const c)
{
switch (c) {
case 0: append("&#x00;"); break;
case '>': append("&gt;"); break;
case '<': append("&lt;"); break;
case '&': append("&amp;"); break;
case '"': append("&quot;"); break;
case '\'': append("&apos;"); break;
default: append(c); break;
}
}
/**
* Append character buffer, sanitize characters if needed
*/
void append_sanitized(char const *src, size_t len)
{
for (; len--; append_sanitized(*src++));
}
/**
* Return unused part of the buffer
*/
Out_buffer remainder() const {
return Out_buffer(_dst + _used, _capacity - _used); }
/**
* Insert gap into already populated part of the buffer
*
* \return empty buffer spanning the gap
*/
Out_buffer insert_gap(unsigned const at, size_t const len)
{
/* don't allow the insertion into non-populated part */
if (at > _used)
return Out_buffer(_dst + at, 0);
_check_advance(len);
memmove(_dst + at + len, _dst + at, _used - at);
advance(len);
return Out_buffer(_dst + at, len);
}
bool has_trailing_newline() const
{
return (_used > 1) && (_dst[_used - 1] == '\n');
}
/**
* Return number of unused bytes of the buffer
*/
size_t used() const { return _used; }
void discard_trailing_whitespace()
{
for (; _used > 0 && is_whitespace(_dst[_used - 1]); _used--);
}
};
class Node
{
private:
/**
* Indentation level of node
*/
unsigned const _indent_level;
Node * const _parent_node = 0;
bool const _parent_was_indented;
bool const _parent_had_content;
Out_buffer _out_buffer;
bool _has_content = false;
bool _is_indented = false;
bool _has_attributes = false;
/**
* Cursor position of next attribute to insert
*/
unsigned _attr_offset = 0;
/**
* Called by sub node
*
* \param indented if true, the returned buffer and the
* end tag start at a fresh line. This is the
* case if the content buffer contains sub
* nodes. But when inserting raw content,
* such additional whitespaces are not desired.
*/
Out_buffer _content_buffer(bool indented)
{
if (!_has_content)
_out_buffer.append(">");
if (indented)
_out_buffer.append("\n");
_has_content = true;
_is_indented = indented;
return _out_buffer.remainder();
}
void _undo_content_buffer(bool indented,
bool was_indented,
bool had_content)
{
_is_indented = was_indented;
_has_content = had_content;
if (indented)
_out_buffer.undo_append(1);
if (!_has_content)
_out_buffer.undo_append(1);
}
/**
* Called by sub node
*/
void _commit_content(Out_buffer content_buffer)
{
_out_buffer.advance(content_buffer.used());
}
public:
void insert_attribute(char const *name, char const *value)
{
/* ' ' + name + '=' + '"' + value + '"' */
size_t const gap = 1 + strlen(name) + 1 + 1 + strlen(value) + 1;
Out_buffer dst = _out_buffer.insert_gap(_attr_offset, gap);
dst.append(' ');
dst.append(name);
dst.append("=\"");
dst.append(value, strlen(value));
dst.append("\"");
_attr_offset += gap;
}
void append(char const *src, size_t src_len)
{
Out_buffer content_buffer = _content_buffer(false);
content_buffer.append(src, src_len);
_commit_content(content_buffer);
}
/**
* Append character, sanitize it if needed
*/
void append_sanitized(char const c)
{
Out_buffer content_buffer = _content_buffer(false);
content_buffer.append_sanitized(c);
_commit_content(content_buffer);
}
void append_sanitized(char const *src, size_t src_len)
{
Out_buffer content_buffer = _content_buffer(false);
content_buffer.append_sanitized(src, src_len);
_commit_content(content_buffer);
}
template <typename FUNC>
Node(Xml_generator &xml, char const *name, FUNC const &func)
:
_indent_level(xml._curr_indent),
_parent_node(xml._curr_node),
_parent_was_indented(_parent_node ? _parent_node->is_indented() : false),
_parent_had_content (_parent_node ? _parent_node->has_content() : false),
_out_buffer(_parent_node ? _parent_node->_content_buffer(true)
: xml._out_buffer)
{
_out_buffer.append('\t', _indent_level);
_out_buffer.append("<");
_out_buffer.append(name);
_attr_offset = _out_buffer.used();
xml._curr_node = this;
xml._curr_indent++;
try {
/*
* Process attributes and sub nodes
*/
func();
} catch (...) {
/* reset and drop changes by not committing it */
xml._curr_node = _parent_node;
xml._curr_indent--;
if (_parent_node) {
_parent_node->_undo_content_buffer(true, _parent_was_indented, _parent_had_content); }
throw;
}
xml._curr_node = _parent_node;
xml._curr_indent--;
if (_is_indented) {
_out_buffer.append("\n");
_out_buffer.append('\t', _indent_level);
}
if (_has_content) {
_out_buffer.append("</");
_out_buffer.append(name);
_out_buffer.append(">");
} else
_out_buffer.append("/>");
if (_parent_node)
_parent_node->_commit_content(_out_buffer);
else
xml._out_buffer = _out_buffer;
_out_buffer.append('\0');
}
bool has_content() { return _has_content; }
bool is_indented() { return _is_indented; }
};
Out_buffer _out_buffer;
Node *_curr_node = 0;
unsigned _curr_indent = 0;
public:
template <typename FUNC>
Xml_generator(char *dst, size_t dst_len,
char const *name, FUNC const &func)
:
_out_buffer(dst, dst_len)
{
if (dst) {
node(name, func);
_out_buffer.append('\n');
_out_buffer.append('\0');
}
}
template <typename FUNC>
void node(char const *name, FUNC const &func = [] () { } )
{
Node(*this, name, func);
}
void node(char const *name) { Node(*this, name, [] () { }); }
void attribute(char const *name, char const *str)
{
_curr_node->insert_attribute(name, str);
}
template <size_t N>
void attribute(char const *name, String<N> const &str)
{
_curr_node->insert_attribute(name, str.string());
}
void attribute(char const *name, bool value)
{
_curr_node->insert_attribute(name, value ? "true" : "false");
}
void attribute(char const *name, long long value)
{
char buf[64];
Genode::snprintf(buf, sizeof(buf), "%lld", value);
_curr_node->insert_attribute(name, buf);
}
void attribute(char const *name, long value)
{
attribute(name, static_cast<long long>(value));
}
void attribute(char const *name, int value)
{
attribute(name, static_cast<long long>(value));
}
void attribute(char const *name, unsigned long long value)
{
char buf[64];
Genode::snprintf(buf, sizeof(buf), "%llu", value);
_curr_node->insert_attribute(name, buf);
}
void attribute(char const *name, unsigned long value)
{
attribute(name, static_cast<unsigned long long>(value));
}
void attribute(char const *name, unsigned value)
{
attribute(name, static_cast<unsigned long long>(value));
}
void attribute(char const *name, double value)
{
String<64> buf(value);
_curr_node->insert_attribute(name, buf.string());
}
/**
* Append content to XML node
*
* This method must not be followed by calls of 'attribute'.
*/
void append(char const *str, size_t str_len = ~0UL)
{
_curr_node->append(str, str_len == ~0UL ? strlen(str) : str_len);
}
/**
* Append sanitized content to XML node
*
* This method must not be followed by calls of 'attribute'.
*/
void append_sanitized(char const *str, size_t str_len = ~0UL)
{
_curr_node->append_sanitized(str, str_len == ~0UL ? strlen(str) : str_len);
}
/**
* Append printable objects to XML node as sanitized content
*
* This method must not be followed by calls of 'attribute'.
*/
template <typename... ARGS>
void append_content(ARGS &&... args)
{
struct Node_output : Genode::Output
{
Node &node; Node_output(Node &n) : node(n) { }
/******************************
** Genode::Output interface **
******************************/
void out_char(char c) override {
node.append_sanitized(c); }
void out_string(char const *str, size_t n) override {
node.append_sanitized(str, n); }
} output { *_curr_node };
Output::out_args(output, args...);
}
size_t used() const { return _out_buffer.used(); }
};
#endif /* _INCLUDE__UTIL__XML_GENERATOR_H_ */
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