path: root/zenxml/summary.dox

// **************************************************************************
// * This file is part of the zen::Xml project. It is distributed under the *
// * Boost Software License: http://www.boost.org/LICENSE_1_0.txt           *
// * Copyright (C) Zenju (zenju AT gmx DOT de) - All Rights Reserved        *
// **************************************************************************

/**
\mainpage Overview

\li \ref sec_Rationale
\li \ref sec_Quick_Start
\li \ref sec_Supported_Platforms
\li \ref sec_Flexible_Programming_Model
\li \ref sec_Structured_XML_element_access
\li \ref sec_Access_XML_attributes
\li \ref sec_Automatic_conversion_built_in
\li \ref sec_Automatic_conversion_string
\li \ref sec_Automatic_conversion_STL
\li \ref sec_Support_user_defined
\li \ref sec_Structured_user_types
\li \ref sec_Type_Safety

\section sec_Rationale Rationale

zen::Xml is an XML library serializing structured user data in a convenient way.
Using compile-time information gathered by techniques of template metaprogramming it minimizes the manual overhead required and frees the user from implementing fundamental type conversions
by himself. Basic data types such as
- \b all built-in arithmetic numbers, 
- \b all kinds of string classes and "string-like" types,
- \b all types defined as STL containers

are handled automatically. Thereby a large number of recurring problems is solved by the library:
- generic number to string conversions
- generic char to wchar_t conversions (UTF) for custom string classes in a platform independent manner
- serialization of arbitrary STL container types
- simple integration: header-only, no extra dependencies, fully portable
- support arbitrary string classes everywhere: for file names, XML element names, attribute names, values, ...
- XML library built on C++11 with focus on elegance, minimal code size, flexibility and performance
- easily extensible API: allow for internationalization, fine-granular error handling, and custom file I/O

The design follows the philosophy of the Loki library: \n
http://loki-lib.sourceforge.net/index.php?n=Main.Philosophy

\section sec_Quick_Start Quick Start

1. Download zen::Xml: http://sourceforge.net/projects/zenxml

2. Setup one of the following preprocessor macros for your project to identify the platform (this is only required if you use C-stream-based file IO)
\code
    ZEN_WIN
    ZEN_LINUX	
	ZEN_MAC
\endcode

3. For optimal performance define this global macro in release build: (following convention of the <tt>assert</tt> macro)
\code
    NDEBUG
\endcode

4. Include the main header:
\code
#include <zenxml/xml.h>
\endcode

5. Start serializing user data:

\code
size_t a = 10;
double b = 2.0;
int    c = -1;
\endcode

\code
zen::XmlDoc doc; //empty XML document

zen::XmlOut out(doc); //the simplest way to fill the document is to use a data output proxy
out["elem1"](a); //
out["elem2"](b); //map data types to XML elements
out["elem3"](c); //

try
{
    save(doc, "file.xml"); //throw zen::XmlFileError
}
catch (const zen::XmlFileError& e) { /* handle error */ }
\endcode

The following XML file will be created:
\verbatim
<?xml version="1.0" encoding="UTF-8"?>
<Root>
    <elem1>10</elem1>
    <elem2>2.000000</elem2>
    <elem3>-1</elem3>
</Root>
\endverbatim

Load an XML file and map its content to user data:
\code
zen::XmlDoc doc; //empty XML document

try
{
    load("file.xml", doc); //throw XmlFileError, XmlParsingError
}
catch (const zen::XmlError& e) { /* handle error */ }

zen::XmlIn in(doc); //the simplest way to read the document is to use a data input proxy
in["elem1"](a); //
in["elem2"](b); //map XML elements into user data
in["elem3"](c); //

//check for mapping errors, i.e. missing elements or conversion errors: you may consider these as warnings only
if (in.errorsOccured())
{
   std::vector<std::wstring> failedElements = in.getErrorsAs<std::wstring>();
   /* generate error message showing the XML element names that failed to convert */
}
\endcode


\section sec_Supported_Platforms Supported Platforms

zen::Xml is written in a platform independent manner and runs on any rudimentary C++11 compliant compiler.
It has been tested successfully under:

- Windows:
   -# Visual C++ 2010 - 32 bit
   -# Visual C++ 2010 - 64 bit
   -# MinGW: GCC 4.5.2 - 32 bit

- Linux:
   -# GCC 4.5.2 - 32 bit
   -# GCC 4.5.2 - 64 bit

- Mac OS X:
   -# Clang 3.2 - 64 bit

<b>Note:</b> In order to enable C++11 features in GCC it is required to specify either of the following compiler options:
\verbatim
-std=c++11
-std=c++0x
-std=gnu++0x
\endverbatim


\section sec_Flexible_Programming_Model Flexible Programming Model

Depending on what granularity of control is required in a particular application, zen::Xml allows the user to choose between full control or simplicity.
\n\n
The library is structured into the following parts, each of which can be used in isolation:
\n\n
\b \<File\> \n
|\n
| io.h\n
|\n
<b>\<Byte Stream\></b>\n
|\n
| parser.h\n
|\n
<b>\<Document Object Model\></b>\n
|\n
| bind.h\n
|\n
<b>\<C++ user data\></b>
\n\n

- Save an XML document to memory
\code
zen::XmlDoc doc;
    ... //fill it
std::string stream = serialize(doc); //throw ()
/* you now have a binary XML stream */

saveStream(stream, "file.xml"); //throw XmlFileError
//if all you need is to store XmlDoc in a file direcly you can use zen::save() instead
\endcode

- Load XML document from memory
\code
//get XML byte stream:
std::string stream = loadStream("file.xml"); //throw XmlFileError

zen::XmlDoc doc;
//parse byte stream into an XML document:
parse(stream, doc); //throw XmlParsingError
//if all you need is to load an XmlDoc from a file you can use zen::load() directly
\endcode

- Fine-granular error checking with the data input proxy
\code
zen::XmlIn in(doc);
//map XML elements into user data
if (!in["elem1"](a))
   throw MyCustomException();
if (!in["elem2"](b))
   throw MyCustomException();
if (!in["elem3"](c))
   throw MyCustomException();

//if (in.errorsOccured()) ...  <- not required here: contains the same conversion errors checked manually before
\endcode

- Access the Document Object Model directly (without input/output proxy)
\n\n
The full power of type conversions which is available via the input/output proxy classes zen::XmlIn and zen::XmlOut is also available for the document object model!
\code
using namespace zen;

XmlDoc doc;

XmlElement& child = doc.root().addChild("elem1");
child.setValue(1234);

save(doc, "file.xml"); //throw XmlFileError
\endcode
\n
\code
using namespace zen;

XmlDoc doc;
load("file.xml", doc); //throw XmlFileError, XmlParsingError

XmlElement* child = doc.root().getChild("elem1");
if (child)
{
    int value = -1;
    if (!child->getValue(value))
        ... //handle conversion error
}
else
    ... //XML element not found
\endcode


\section sec_Structured_XML_element_access Structured XML element access

\code
//write a value into one deeply nested XML element - note the different types used seamlessly: char[], wchar_t[], char, wchar_t, int
zen::XmlOut out(doc);
out["elemento1"][L"элемент2"][L"要素3"][L"στοιχείο4"]["elem5"][L"元素6"][L'元']['z'](-1234);
\endcode

The resulting XML:
\verbatim
<?xml version="1.0" encoding="UTF-8"?>
<Root>
    <elemento1>
        <элемент2>
            <要素3>
                <στοιχείο4>
                    <elem5>
                        <元素6>
                            <元>
                                <z>-1234</z>
                            </元>
                        </元素6>
                    </elem5>
                </στοιχείο4>
            </要素3>
        </элемент2>
    </elemento1>
</Root>
\endverbatim


\section sec_Access_XML_attributes Access XML attributes

\code
zen::XmlDoc doc;

zen::XmlOut out(doc);
out["elem"].attribute("attr1",   -1); //
out["elem"].attribute("attr2",  2.1); //write data into XML attributes
out["elem"].attribute("attr3", true); //

save(doc, "file.xml"); //throw XmlFileError
\endcode

The resulting XML:
\verbatim
<?xml version="1.0" encoding="UTF-8"?>
<Root>
    <elem attr1="-1" attr2="2.1" attr3="true"/>
</Root>
\endverbatim


\section sec_Automatic_conversion_built_in Automatic conversion for built-in arithmetic types

All built-in arithmetic types and <tt>bool</tt> are detected at compile time and a proper conversion is applied. 
Common conversions for integer-like types such as <tt>int</tt>, <tt>long</tt>, <tt>long long</tt>, ect. as well as floating point types are optimized for maximum performance.

\code
zen::XmlOut out(doc);

out["int"]   (-1234);
out["double"](1.23);
out["float"] (4.56f);
out["ulong"] (1234UL);
out["bool"]  (false);
\endcode

The resulting XML:
\verbatim
<?xml version="1.0" encoding="UTF-8"?>
<Root>
    <int>-1234</int>
    <double>1.23</double>
    <float>4.56</float>
    <ulong>1234</ulong>
    <bool>false</bool>
</Root>
\endverbatim


\section sec_Automatic_conversion_string Automatic conversion for string-like types

The document object model of zen::Xml internally stores all names and values as a std::string. Consequently everything that is not a std::string but is "string-like" is UTF-converted
into a std::string representation. By default zen::Xml accepts all character arrays like <tt>char[]</tt>, <tt>wchar_t[]</tt>, <tt>char*</tt>, <tt>wchar_t*</tt>, single characters like 
<tt>char</tt>, <tt>wchar_t</tt>, standard string classes like <tt>std::string</tt>, <tt>std::wstring</tt> and user-defined string classes.
If the input string is based on <tt>char</tt>, it will simply be copied and thereby preserves any local encodings. If the input string is based on <tt>wchar_t</tt> it will
be converted to an UTF-8 encoded <tt>std::string</tt>. The correct <tt>wchar_t</tt> encoding of the system will be detected at compile time, for example UTF-16 on Windows, 
UTF-32 on most Linux distributions.

<b>Note:</b> User-defined string classes are automatically supported if they fulfill the following <b>string concept</b> by defining:
    -# A typedef named <tt>value_type</tt> for the underlying character type: must be \p char or \p wchar_t
    -# A member function <tt>c_str()</tt> returning something that can be converted into a <tt>const value_type*</tt>
    -# A member function <tt>length()</tt> returning the number of characters returned by <tt>c_str()</tt>

\code
std::string  elem1 = "elemento1";
std::wstring elem2 = L"элемент2";
wxString     elem3 = L"要素3";
MyString     elem4 = L"στοιχείο4";

zen::XmlOut out(doc);

out["string"]    (elem1);
out["wstring"]   (elem2);
out["wxString"]  (elem3);
out["MyString"]  (elem4);
out["char[6]"]   ("elem5");
out["wchar_t[4]"](L"元素6");
out["wchar_t"]   (L'元');
out["char"]      ('z');
\endcode

The resulting XML:
\verbatim
<?xml version="1.0" encoding="UTF-8"?>
<Root>
    <string>elemento1</string>
    <wstring>элемент2</wstring>
    <wxString>要素3</wxString>
    <MyString>στοιχείο4</MyString>
    <char[6]>elem5</char[6]>
    <wchar_t[4]>元素6</wchar_t[4]>
    <wchar_t>元</wchar_t>
    <char>z</char>
</Root>
\endverbatim


\section sec_Automatic_conversion_STL Automatic conversion for STL container types

- User-defined STL compatible types are automatically supported if they fulfill the following <b>container concept</b> by defining:
    -# A typedef named <tt>value_type</tt> for the underlying element type of the container
    -# A typedef named <tt>iterator</tt> for a non-const iterator into the container
    -# A typedef named <tt>const_iterator</tt> for a const iterator into the container
\n\n
    -# A member function <tt>begin()</tt> returning an iterator pointing to the first element in the container
    -# A member function <tt>end()</tt> returning an iterator pointing just after the last element in the container
    -# A member function <tt>insert()</tt> with the signature <tt>iterator insert(iterator position, const value_type& x)</tt>
    -# A member function <tt>clear()</tt> removing all elements from the container

- In order to support combinations of user types and STL containers such as <tt>std::vector<MyType></tt> or <tt>std::vector<std::list<MyType>></tt> it is sufficient to 
only integrate <tt>MyType</tt> into zen::Xml. \n
See \ref sec_Support_user_defined
    
\code
std::deque   <float>         testDeque;
std::list    <size_t>        testList;
std::map     <double, char>  testMap;
std::multimap<short, double> testMultiMap;
std::set     <int>           testSet;
std::multiset<std::string>   testMultiSet;
std::vector  <wchar_t>       testVector;
std::vector  <std::list<wchar_t>> testVectorList;
std::pair    <char, wchar_t> testPair;

/* fill container */

zen::XmlOut out(doc);

out["deque"]    (testDeque);
out["list"]     (testList);
out["map"]      (testMap);
out["multimap"] (testMultiMap);
out["set"]      (testSet);
out["multiset"] (testMultiSet);
out["vector"]   (testVector);
out["vect_list"](testVectorList);
out["pair" ]    (testPair);
\endcode

The resulting XML:
\verbatim
<?xml version="1.0" encoding="UTF-8"?>
<Root>
    <deque>
        <Item>1.234</Item>
        <Item>5.678</Item>
    </deque>
    <list>
        <Item>1</Item>
        <Item>2</Item>
    </list>
    <map>
        <Item>
            <one>1.1</one>
            <two>a</two>
        </Item>
        <Item>
            <one>2.2</one>
            <two>b</two>
        </Item>
    </map>
    <multimap>
        <Item>
            <one>3</one>
            <two>99</two>
        </Item>
        <Item>
            <one>3</one>
            <two>100</two>
        </Item>
        <Item>
            <one>4</one>
            <two>101</two>
        </Item>
    </multimap>
    <set>
        <Item>1</Item>
        <Item>2</Item>
    </set>
    <multiset>
        <Item>1</Item>
        <Item>1</Item>
        <Item>2</Item>
    </multiset>
    <vector>
        <Item>Ä</Item>
        <Item>Ö</Item>
    </vector>
    <vect_list>
        <Item>
            <Item>ä</Item>
            <Item>ö</Item>
            <Item>ü</Item>
        </Item>
        <Item>
            <Item>ä</Item>
            <Item>ö</Item>
            <Item>ü</Item>
        </Item>
    </vect_list>
    <pair>
        <one>a</one>
        <two>â</two>
    </pair>
</Root>
\endverbatim


\section sec_Support_user_defined Support for user-defined types

User types can be integrated into zen::Xml by providing specializations of zen::readText() and zen::writeText() or zen::readStruc() and zen::writeStruc().
The first pair should be used for all non-structured types that can be represented as a simple text string. This specialization is then used to convert the type to XML elements
and XML attributes. The second pair should be specialized for structured types that require an XML representation as a hierarchy of elements. This specialization is used when converting
the type to XML elements only.
\n\n
See section \ref sec_Type_Safety for a discussion of type categories.
\n\n
<b>Example: Specialization for an enum type</b>
\code
enum UnitTime
{
    UNIT_SECOND,
    UNIT_MINUTE,
    UNIT_HOUR
};

namespace zen
{
template <> inline
void writeText(const UnitTime& value, std::string& output)
{
    switch (value)
    {
        case UNIT_SECOND: output = "second"; break;
        case UNIT_MINUTE: output = "minute"; break;
        case UNIT_HOUR:   output = "hour"  ; break;
    }
}

template <> inline
bool readText(const std::string& input, UnitTime& value)
{
    std::string tmp = input;
    zen::trim(tmp);
    if (tmp == "second")
        value = UNIT_SECOND;
    else if (tmp == "minute")
        value = UNIT_MINUTE;
    else if (tmp == "hour")
        value = UNIT_HOUR;
    else
        return false;
    return true;
}
}
\endcode

<b>Example: Brute-force specialization for an enum type</b>
\code
namespace zen
{
template <> inline
void writeText(const EnumType& value, std::string& output)
{
    output = zen::numberTo<std::string>(static_cast<int>(value)); //treat enum like an integer
}

template <> inline
bool readText(const std::string& input, EnumType& value)
{
    value = static_cast<EnumType>(zen::stringTo<int>(input)); //treat enum like an integer
    return true;
}
}
\endcode

<b>Example: Specialization for a structured user type</b>
\code
struct Config
{
    int a;
    std::wstring b;
};

namespace zen
{
template <> inline
void writeStruc(const Config& value, XmlElement& output)
{
    XmlOut out(output);
    out["number" ](value.a);
    out["address"](value.b);
}

template <> inline
bool readStruc(const XmlElement& input, Config& value)
{
    XmlIn in(input);
    bool rv1 = in["number" ](value.a);
    bool rv2 = in["address"](value.b);
    return rv1 && rv2;
}
}

int main()
{
    Config cfg = { 2,  L"Abc 3" };

    std::vector<Config> cfgList;
    cfgList.push_back(cfg);

    zen::XmlDoc doc;
    zen::XmlOut out(doc); //write to Xml via output proxy
    out["config"](cfgList);
    save(doc, "file.xml"); //throw XmlFileError
}
\endcode

The resulting XML:
\verbatim
<?xml version="1.0" encoding="UTF-8"?>
<Root>
    <config>
        <Item>
            <number>2</number>
            <address>Abc 3</address>
        </Item>
    </config>
</Root>
\endverbatim


\section sec_Structured_user_types Structured user types

Although it is possible to enable conversion of structured user types by specializing zen::readStruc() and zen::writeStruc() (see \ref sec_Support_user_defined), 
this approach has one drawback: If a mapping error occurs when converting an XML element to structured user data, for example a child-element is missing,
the input proxy class zen::XmlIn is only able to detect that the whole conversion failed. It cannot say which child-elements in particular failed to convert.
\n\n
Therefore it may be appropriate to convert structured types by calling subroutines in order to enable fine-granular logging:

\code
void readConfig(const zen::XmlIn& in, Config& cfg)
{
    in["number" ](value.a); //failed conversions will now be logged for each single item by XmlIn
    in["address"](value.b); //instead of only once for the complete Config type!
}


void loadConfig(const wxString& filename, Config& cfg)
{
    zen::XmlDoc doc; //empty XML document

    try
    {
        load(filename, doc); //throw XmlFileError, XmlParsingError
    }
    catch (const zen::XmlError& e) { /* handle error */ }

    zen::XmlIn in(doc); 
 
    zen::XmlIn inConfig = in["config"]; //get input proxy for child element "config"
  
    readConfig(inConfig, cfg); //map child element to user data by calling subroutine

    //check for mapping errors: errors occuring in subroutines are considered, too!
    if (in.errorsOccured())
       /* show mapping errors */
}
\endcode


\section sec_Type_Safety Type Safety

zen::Xml heavily uses methods of compile-time introspection in order to free the user from managing basic type conversions by himself. 
Thereby it is important to find the right balance between automatic conversions and type safety so that program correctness is not compromised.
In the context of XML processing three fundamental type categories can be recognized:

- <b>string-like types</b>: <tt>std::string, wchar_t*, char[], wchar_t, wxString, MyStringClass, ...</tt>
- <b>to-string-convertible types</b>: any string-like type, all built-in arithmetic numbers, <tt>bool</tt>
- <b>structured types</b>: any to-string-convertible type, STL containers, <tt>std::pair</tt>, structured user types

These categories can be seen as a sequence of inclusive sets:
\verbatim
-----------------------------
| structured                |  Used as: XML element value
| ------------------------- |           Conversion via: readStruc(), writeStruc() - may be specialized for user-defined types!
| | to-string-convertible | |  Used as: XML element/attribute value
| | ---------------       | |           Conversion via: readText(), writeText() - may be specialized for user-defined types!
| | | string-like |       | |  Used as: XML element/attribute value or element name
| | ---------------       | |           Conversion via: utfCvrtTo<>()
| ------------------------- |
-----------------------------
\endverbatim

A practical implication of this design is that conversions that do not make sense in a particular context simply lead to compile-time errors:
\code
zen::XmlOut out(doc);
out[L'Z'](someValue); //fine: a wchar_t is acceptable as an element name
out[1234](someValue); //compiler error: an integer is NOT "string-like"!
\endcode
\n
\code
int i = 0;
std::vector<int> v;

zen::XmlOut out(doc);
out["elem1"](i); //fine: both i and v can be converted to an XML element
out["elem2"](v); //

out["elem"].attribute("attr1", i); //fine: an integer can be converted to an XML attribute
out["elem"].attribute("attr2", v); //compiler error: a std::vector<int> is NOT "to-string-convertible"!
\endcode

  \author \b Zenju 
  \n\n
  <b>Email:</b> zenju AT gmx DOT de
*/