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REG file parser using the Boost Spirit Parser Framework

System Programming
Windows
C++
July 1, 2014

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This article describes a sample parser of reg files using the Boost Spirit Parser Framework. The main aim of this article is to share the experience, and that’s why here, I’ll show not so much the solution for the concrete task or the usage of the concrete technology as the way the development process goes. In particular, we’ll discuss why we use the curtain libraries and make one or another solution.

Contents:

Testimonials

I would like to thank the people who developed the following projects – they made the implementation of this project easier:

I want to say a personal thank you to Silviu Simen for his article INI file reader using the Spirit library.

Background and history of this task

There was a project in which I took part and we needed to test the working of a parser for Windows hive Registry files. These files are stored in binary representation and the structure of such a file is not documented by Microsoft. But, by means of research, my colleagues managed to clear out this structure, and after that, the question of verifying the parser work appeared.

To perform testing, I decided to use the functionality of exporting of Registry in two formats: hive and reg. Thus, I could obtain two different files for the same Registry key and after that check the working of the Windows hive Registry file parser.

The structure of the Registry file – I’ll give an example below – is very similar to the structure of the ini file, so you can use standard Windows functions for reading values in this file. But the problem is that, functions work very slow for big files, and that is why this parser was developed – a parser for reg files where I use the Boost Spirit Parser Framework. The reasons why standard Windows functions are slow will be considered below in this article.

What is a reg file?

Let’s consider the general view of a reg file structure first, and some special complicated cases will be considered as necessary.

I’ve taken the following material from here http://en.wikipedia.org/wiki/Windows_Registry.

.REG files (also known as Registration entries) are text-based human-readable files for storing portions of the Registry. On Windows 2000 and later NT-based Operating Systems, they contain the string Windows Registry Editor Version 5.00 at the beginning and are Unicode-based. On Windows 9x and NT 4.0 systems, they contain the string REGEDIT4 and are ANSI-based. Windows 9x format .REG files are compatible with Windows 2000 and later NT-based systems. The Registry Editor on Windows on these systems also supports exporting .REG files in Windows 9x/NT format. Data is stored in .REG files in the following syntax:

ShellScript
[<:Hive Name><:Key Name><Subkey Name>]
"Value Name"=<Value type>:<Value data>

Example 1 (different types):

ShellScript
[HKEY_LOCAL_MACHINESOFTWAREMicrosoft]
"Value A"="<String value data>"
"Value B"=hex:<Binary data>
"Value C"=dword:<DWORD value integer>
"Value D"=hex(7):<Multi-string value data>
"Value E"=hex(2):<Expandable string value data>

Example 2 (real):

ShellScript
[HKEY_CURRENT_USERKey]
"Value string"="B"
"Value dword"=dword:00000001
"Value hard"=hex(1000800c):53,00,65,00,72,00,76,00,69,00,63,00,65,00,53,00,
  74,00,61,00,72,00,74,00,54,00,79,00,70,00,65,00,00,00,4d,00,61,00,78,00,44

Making a little digression, I want to stress that the number in the line ” hex(1000800c) ” is the type identifier and it can be anything. It’s often used as the data in the security branch [HKEY_LOCAL_MACHINESAM].

And now, let’s try to extend the information about the possible contents of the reg file. Here, I represent some facts obtained during our research process:

ShellScript
1) Key Name may consist of alphabetical symbols and " ,   ,  [ , ]. 
2) Number of values of one key can be from 0 to infinite
3) Value Name can be:
   - symbol '@' - it means default
   - "text"     - any symbols can be in this "text" 
                  even these ones: n , " ,  , [ , ] 
                  but it always ends with "n symbols in sequence
4) Value data can be:
 - "text" - any symbols can be in this "text" 
   but it always ends with " and n in sequence 
 - binary:
   - dword:XX
   - hex:XX 
   - hex(N):XX
   Comments:
     XX can be the pairs of number symbols separated by comas and
     it can end with '' symbol that means that 
     data continue in the next line
   Example:
   dword:72,...,00,
   00,..,20

Two approaches and their comparison

As it was mentioned, the structures of reg files and ini files are quite the same, so I started to search for methods for working with ini files. I found the standard Windows functions.

Using the Windows API functions

Windows gives a lot of functions to work with INI files; we are interested in two of them for our task:

  • GetPrivateProfileSectionNames: Retrieves the names of all the sections in an initialization file.
  • GetPrivateProfileSection: Retrieves all the keys and values for the specified section of an initialization file.

So, we should call GetPrivateProfileSectionNames one time to obtain the list of keys and then call GetPrivateProfileSection to obtain the values inside the keys.

The problem is that if the file is quite big, i.e., there are a lot of keys in it, then we should call GetPrivateProfileSection several times to read from the file. Here is some row test data: file size: 30 MB, file includes about 30,000 keys, the parsing of this file takes about 20 minutes. And, I should say that reg files are often bigger than 100 MB.

So, the problem:

Unjustified number of readings from the file.

Solution:

It’s necessary to load the file to the memory at one time or in some parts and then parse its content using your own tools.

Using a custom parser

When parsing a reg file content using your our own tools, it’s good idea to use already developed work. Thus, I came across the article about the ini file reader using the Spirit library. Using the example of the ini file parser, I developed my reg file parser.

Why boost::spirit ?

The Spirit Parser Framework is an object oriented recursive descent parser generator framework implemented using template metaprogramming techniques. Expression templates allow users to approximate the syntax of Extended Backus Naur Form (EBNF) completely in C++.

I was also attracted by these factors:

  1. There are no intermediate conversions to some code needed, and also no external applications except for the compiler.
  2. You need to include only two header files and no libraries to use the Spirit Parser Framework.

Useful links:

Fleeting glance on boost::spirit

The main idea of using boost::spirit is in using the rules. Usually, several basic rules are defined, and then other rules are defined by means of overridden operators as a combinations of basic rules. The following example shows the creation of rules using “AND” and “NOT” operators:

ShellScript
RuleType simpleRule = ~ch_t('A') & ~ch_t('B');

This rule works for any symbol except for ‘A’ and ‘B’.

Below in this article, each rule will be described in detail, but now, I want to give some quick information about possible operators – to let you imagine what the possible operations with the rules are.

ShellScript
Set operators:
 a | b    Union           Match a or b. Also referred to as alternative
 a & b    Intersection    Match a and b
 a - b    Difference      Match a but not b. If both match and b's matched text
                          is shorter than a's matched text, a successful
                          match is made
 a ^ b    XOR             Match a or b, but not both
Sequencing Operators:
 a >> b    Sequence        Match a and b in sequence
 a && b    Sequential-and  Sequential-and. Same as above, 
                           match a and b in sequence
 a || b    Sequential-or   Match a or b in sequence
Optional and Loops:
 *a        -    Match a zero (0) or more times
 +a        -    Match a one (1) or more times
 !a        -    Match a zero (0) or one (1) time
 a % b     -    Match a list of one or more repetitions 
                of a separated by occurrences of b. 
                This is the same as a >> *(b >> a). 
                Note that a must not also match b
Single character parsers:
 anychar_p  Matches any single character 
           (including the null terminator: '')
 alnum_p    Matches alpha-numeric characters
 alpha_p    Matches alphabetic characters
 blank_p    Matches spaces or tabs
 cntrl_p    Matches control characters
 digit_p    Matches numeric digits
 graph_p    Matches non-space printing characters
 lower_p    Matches lower case letters
 print_p    Matches printable characters
 punct_p    Matches punctuation symbols
 space_p    Matches spaces, tabs, returns, and newlines
 upper_p    Matches upper case letters
 xdigit_p   Matches hexadecimal digits
Other comments:
 negation ~
 Example: ~ch_t('x') - matches any character except 'x'

Introduction to the parser development

Further in this article, I’ll try to keep the high level of clearness so I’m sorry in advance if you think that my descriptions are too detailed.

The description starts from the heart of the parser – its algorithm. The algorithm is described in parts, and then the wrapper for this algorithm is described, and then other auxiliary classes. At the end, we’ll consider a concrete usage example and test.

Algorithm description

The algorithm is represented by a function and interface:

C
template<class charT>
struct IResultProcessor
{
    virtual ~IResultProcessor(){}
    virtual void OnKeyFound(const charT* begin, const charT* end)=0;
    virtual void OnValueNameFound(const charT* begin, const charT* end)=0;
    virtual void OnValueDataFound(const charT* begin, const charT* end)=0;    
};
template<class charT>
inline bool ParseRegFileImpl(const charT* buffer,
                             IResultProcessor<charT>* resultProc);

It follows from the function names that the algorithm will call the OnKeyFound function for each key name found, OnValueNameFound for each value name found, and OnValueDataFound for the value content.

An observant reader can ask a question: “Why is the processing of value separated into two functions, OnValueNameFound and OnValueDataFound, after all it it one single entity?” The answer is simple: “The implementation of this processing inside the algorithm would be hard and so the algorithm entrusts calling inside it the processing of these two parts”.

Preparatory work

At this stage, we will prepare the environment for the convenient work. In particular, we should use namespaces, shorten the line for rule creation, and define frequently used rules.

C
using namespace boost::spirit;
typedef rule<scanner<const> > RuleType;
typedef chlit<charT> ch_t;  // Single character
typedef chset<charT> chs_t; // Character set
typedef IResultProcessor<charT> ResProcT;
chs_t anychar_t(anychar_p); // Pattern anychar to character set
chs_t eol_CR('r'); // End of line CR
chs_t eol_LF('n'); // End of line LF
chs_t eol_t(eol_CR);// CR or LF end of line
eol_t |= eol_LF;

Auxiliary rules

C
// Matches spaces or tabs
RuleType blanks   = * blank_p;
// Symbols ']'and '[' - separate Key Name
RuleType not_name_separator = ~ch_t(']') & ~ch_t('[');
// empty data
RuleType empty_data = blanks >> (eol_t | ch_t(''));
// Data that we don't interested
// @ - it's default value name , " - requires additional processing
RuleType other_data = *(anychar_t & not_name_separator & 
                        ~ch_t('@')& ~ch_t('"'));

The first rule is to omit the blanks and tabs. Asterisk means that the rule can work several times in a row or not work at all.

The second rule is to make sure that the current symbol is not the name separator.

The third rule is to omit empty data. The operator >> means that the rule at the left side of the operator and the rule at the right side should be performed in sequence, one after another.

The forth rule is assigned to free data not part of the separators. Any symbol matches this rule except for name separators, @ – the identifier of value by default, and the symbol ” that signals the end of the line. This rule can work either several times or never.

Rule for the key name

C
RuleType ident_kname_continue = ch_t(']') >> ~eol_t;
RuleType ident_key_name = *(anychar_t & ~ch_t(']')) || 
         ident_kname_continue >> ident_key_name;

This rule can be illustrated on the scheme:

ident_key_name.png

Rule ident_kname_continue is an auxiliary for ident_key_name. First of all, ident_key_name is the recursive rule, and after the process meets symbol ], it tries to define if it is the end of the name or the part of the name. If symbol ] is the part of the name, i.e., there is no symbol of line end after it, and then this rule starts itself again and continues parsing.

Let’s consider the following case for example:

ShellScript
[HKEY_LOCAL_MACHINESOFTWAREMicrosoft_HARD_NAME[123]_ABCD]

In this example, the symbol ] is the part of the name and that’s why it’s necessary to check if there is the symbol of line end after it. You can see such names in the Registry.

Rule for the Value name

C
// if "= symbols sequence is found - value name ends
RuleType ident_vname_continue = +ch_t('"') >> ~ch_t('=');    
// If '"' symbol is found - check if value name ends,
// if it doesn't parsing continues.
RuleType ident_vname_sz_skip = ch_t('\') >> ch_t('"');
RuleType ident_vname_sz_body = *(anychar_t & ~ch_t('"') ||
    ident_vname_sz_skip );  
RuleType ident_vname_sz = 
  ident_vname_sz_body >> *(ident_vname_continue >> ident_vname_sz_body);
// Rule for default value name    
RuleType ident_vname_sz_impl = ch_t('"') >> ident_vname_sz >> +ch_t('"');
RuleType ident_vname_def = ch_t('@');
// "text" or DEFAULT
RuleType ident_value_name = ident_vname_def | ident_vname_sz_impl;

This rule can be represented on the scheme:

ident_vname.png

Rule for the value content

C
// if value content is binary
// Data can be any character except for '\' and 'n' in sequence
RuleType vdata_bin_body =*(anychar_t & ~ch_t('') & 
              ~eol_t & ~ch_t('\'));
RuleType vdata_bin_continue = ch_t('\') >> eol_t;
// if '\' and 'n' in sequence data continue on the next line
RuleType vdata_bin = vdata_bin_body >> 
    *(vdata_bin_continue >> vdata_bin_body);
// if value content is string
// String data always ends with '"' and 'n' symbols in sequence
RuleType vdata_sz_continue = +ch_t('"') >> ~eol_t;
RuleType vdata_sz_body_impl = *(anychar_t & ~ch_t('"'));
RuleType vdata_sz_body = vdata_sz_body_impl >> 
       *(vdata_sz_continue >> vdata_sz_body_impl);
// String data always starts and ends with '"' symbol
RuleType ident_vdata_sz = ch_t('"') >> vdata_sz_body >> +ch_t('"');
// Check value data format    
RuleType ident_vdata = ident_vdata_sz | vdata_bin;

This rule can be represented on the scheme like this:

ident_vdata.png

Rule that describes the line with the key name

C
// line with key name    
RuleType l_key = 
    other_data>> // Can be comments or start title 
    ch_t('[') >> // start of the key name
    // Call OnKeyFound function if rule succeeds
    ident_key_name   [bind(&CRegFileParserImpl::OnKeyFound, 
                      this, _1,_2) ] >>
    blanks    >> // can be blanks
    ch_t(']') >> // end of the key name
    blanks    >> // can be blanks
    *eol_t;      // one or more end of line symbols

This rule requires the execution of several rules in sequence. The new idea here is to use the operator []. In this case, it means that when the rule is activated, the functor transferred as the parameter should be called. And, the range where this rule worked will be transferred to this functor via two parameters.

Rule that describes the line with the Value

C
// lines with value name and data
RuleType l_values = 
    other_data>> // Can be comments or start title
    // Call OnValueNameFound function if rule succeed
    ident_value_name  
      [bind(&CRegFileParserImpl::OnValueNameFound, this, _1,_2) ] >>   
    blanks    >> // can be blanks                    
    ch_t('=') >> // always separates value name and value data
    blanks    >> // can be blanks
    // Call OnValueDataFound function if rule succeeded
    value_data  
      [bind(&CRegFileParserImpl::OnValueDataFound, this, _1,_2) ]  >>
    blanks    >> // can be blanks
    *eol_t;      // one or more end of line symbols

This rule is much like the previous one. At this moment, we can return to the question stated during the interface discussion: “Why is the processing of Value separated into two functions OnValueNameFound and OnValueDataFound, after all it is one single entity?”. Now, we can give a more detailed answer. As it’s seen from the code above, it’s hard to support an interface corresponding to the reg file structure by means of boost::spirit – a function call with 4 parameters for the whole value.

Gathering everything together

C
// Any line can satisfy one of the three rules
RuleType lines = l_key | l_values | empty_data;
// Start lexeme_d pars that compares also additional symbols
// if does just *lines, symbols ' ','t','n' are not compared
RuleType reg_file =  lexeme_d [*lines] ;
// Execute parse
return (parse(buffer, reg_file).full);

So, we finished the algorithm of reg file parsing. The rules for the key name are set, the value is aggregated, and the file parsing starts.

The whole function looks like the following:

C
template<class charT>
inline bool ParseRegFileImpl(const charT* buffer,
                             IResultProcessor<charT>* resultProc)
{
    using namespace boost::spirit;
    typedef rule<scanner<const charT*> > RuleType;
    typedef chlit<charT> ch_t;  // Single character
    typedef chset<charT> chs_t; // Character set
    typedef IResultProcessor<charT> ResProcT;
    chs_t anychar_t(anychar_p); // Pattern to char set
    chs_t eol_CR('r'); // End of line CR
    chs_t eol_LF('n'); // End of line LF
    chs_t eol_t(eol_CR);// CR or LF end of line
    eol_t |= eol_LF;
    
/* -------------------------------------------------------------- */
/* Help rules*/
    // Matches spaces or tabs
    RuleType blanks   = * blank_p;
    // Symbols ']'and '[' - separate Key Name
    RuleType not_name_separator = ~ch_t(']') & ~ch_t('[');
    // empty data
    RuleType empty_data = blanks >> (eol_t | ch_t(''));
    // Data in what we aren't interested
    // @ - it's default value name, "
    //   - requires additional processing
    RuleType other_data = *(anychar_t & not_name_separator & 
                            ~ch_t('@')& ~ch_t('"'));     
/* -------------------------------------------------------------- */
/* Rules that describe identifier of key name */
    RuleType ident_kname_continue = ch_t(']') >> ~eol_t;
    RuleType ident_key_name = *(anychar_t & ~ch_t(']')) || 
             ident_kname_continue >> ident_key_name;
  
/* -------------------------------------------------------------- */
/* Rules that describe identifier of value name */
    // Skip " sequence
    RuleType ident_vname_sz_skip = ch_t('\') >> ch_t('"');
    RuleType ident_vname_sz_impl = 
       *(anychar_t & ~ch_t('"') || ident_vname_sz_skip );  
    // Add trailing symbols to match pattern
    RuleType ident_vname_sz = ch_t('"') >> 
             ident_vname_sz_impl >> +ch_t('"');
    // Rule for default value name     
    RuleType ident_vname_def = ch_t('@');
    // "text" or DEFAULT
    RuleType ident_value_name = ident_vname_def | ident_vname_sz;
/* -------------------------------------------------------------- */
/* Rules that describe value content */
    // if value content is binary
    // Data can be any character except for '\' and 'n' in sequence
    RuleType vdata_bin_body = 
      *(anychar_t & ~ch_t('') & ~eol_t & ~ch_t('\'));
    RuleType vdata_bin_continue = ch_t('\') >> eol_t;
    // if '\' and 'n' in sequence then
    // data continue on the next line
    RuleType vdata_bin = vdata_bin_body >> 
      *(vdata_bin_continue >> vdata_bin_body);
    // if value content is string
    // String data always end with '"' and 'n' symbols in sequence
    RuleType vdata_sz_continue = +ch_t('"') >> ~eol_t;
    RuleType vdata_sz_body_impl = *(anychar_t & ~ch_t('"'));
    RuleType vdata_sz_body = vdata_sz_body_impl >> 
            *(vdata_sz_continue >> vdata_sz_body_impl);
    // String data always start and end with '"' symbol
    RuleType ident_vdata_sz = ch_t('"') >> 
             vdata_sz_body >> +ch_t('"');
    
    // Check value content format    
    RuleType ident_vdata = ident_vdata_sz | vdata_bin;
/* -------------------------------------------------------------- */
/* Put all rules together */
    // line with key name     
    RuleType l_key = 
        other_data>> // Can be comments or start title 
        ch_t('[') >> // starts key name
        // Call OnKeyFound function if rule succeed
        ident_key_name   [bind(&ResProcT::OnKeyFound, 
                          resultProc, _1,_2) ] >>
        blanks    >> // can be blanks
        ch_t(']') >> // ends key name
        blanks    >> // can be blanks
        *eol_t;      // one or more end of line symbols
    // lines with value name and data
    RuleType l_values =             
        other_data>> // Can be comments or start title
        // Call OnValueNameFound function if rule succeed
        ident_value_name   [bind(&ResProcT::OnValueNameFound, 
                            resultProc, _1,_2) ] >>   
        blanks    >> // can be blanks                         
        ch_t('=') >> // always separates value name and value data
        blanks    >> // can be blanks
        // Call OnValueDataFound function if rule succeed
        ident_vdata  [bind(&ResProcT::OnValueDataFound, 
                      resultProc, _1,_2) ]  >>
        blanks    >> // can be blanks
        *eol_t;      // one or more end of line symbols
    // Any line can satisfy one of three rules
    RuleType lines = l_key | l_values | empty_data;
    // Do lexeme_d pars that compare also additional symbols
    // if do just *lines, symbols ' ','t','n' are not compared
    RuleType reg_file =  lexeme_d [*lines] ;
    
    // Execute parse
    return (parse(buffer, reg_file).full);
}

CRegFileParser

It’s time to consider the wrapper class for this algorithm. This class assumes the processing of the value name and the value content. In other words, this class supports the following intrface:

C
template<class charT>
struct IRegFileObserver
{
    virtual ~IRegFileObserver(){}
    virtual void OnKeyFound(const charT* begin, const charT* end)=0;
    virtual void OnValueFound(const charT* nameBegin, const charT* nameEnd,
                              const charT* dataBegin, const charT* dataEnd)=0;
};

And the class itself:

C
template<class charT>
class CRegFileParser:public IResultProcessor<charT>
{    
    typedef std::pair<const charT*,const charT*> BuferRange;
    BuferRange lastVName_;
    
    IRegFileObserver<charT>* pObserver_;
   
    bool bLastVNameProcessed_;
public:
    CRegFileParser(IRegFileObserver<charT>* pObserver)
        : pObserver_(pObserver)
        , bLastVNameProcessed_(true)
    {}
    bool Parse(const charT* buffer)
    {
        return ParseRegFileImpl(buffer,this);
    }
private:
    void OnKeyFound(const charT* begin, const charT* end)
    {
        CheckVNameProcessed(true);
        
        pObserver_->OnKeyFound(begin,end);
    }
    void OnValueNameFound(const charT* begin, const charT* end)
    {
        CheckVNameProcessed(true);
        bLastVNameProcessed_ = false;
        lastVName_.first = begin;
        lastVName_.second = end;    
    }
    void OnValueDataFound(const charT* begin, const charT* end)
    {
        CheckVNameProcessed(false);
        bLastVNameProcessed_ = true;
        pObserver_->OnValueFound(lastVName_.first, 
                       lastVName_.second,begin,end);
    }
    void CheckVNameProcessed(bool needToBeProcessed)
    {
        if(bLastVNameProcessed_ != needToBeProcessed)
            throw std::exception("Value data not " + 
                  "found for founded value name");
    }
};

Using Pool

Before considering the observers created for testing, we should describe the usage of the boost Pool library.

What is Pool?

Pool allocation is a memory allocation scheme that is very fast, but limited in its usage.

Installation

The Boost Pool library is a header file library. That means there is no .lib, .dll, or .so to build; just add the Boost directory to your compiler’s include file path, and you should be good to go!

How do I use Pool?

To make it convenient, I created the following classes that have the functionality of the standard STL containers but use the boost Pool library:

C
#include <boost/pool/pool_alloc.hpp>
#include <map>
#include <vector>
#include <list>
#include <string>
template<class _Kty, class _Ty>
class QMap : public std::map< _Kty, _Ty, std::less<_Kty>, 
             boost::fast_pool_allocator< std::pair<_Kty,_Ty> > >
{};
template<class _Ty>
class QVect : public std::vector< _Ty, boost::pool_allocator<_Ty> >
{};
template<class _Ty>
class QList : public std::list< _Ty, boost::pool_allocator<_Ty> >
{};
template<class _Ty>
class QStringStream : 
  public std::basic_stringstream< _Ty,std::char_traits<_Ty>, 
                                   boost::pool_allocator<_Ty> >
{};
template<class _Ty>
class QString: public std::basic_string<_Ty,std::char_traits<_Ty>,
                                        boost::pool_allocator<_Ty> >
{
    typedef std::basic_string<_Ty,std::char_traits<_Ty>,
                              boost::pool_allocator<_Ty> >
    BaseClass;
public:
    QString(){}
    // construct from [_First, _Last), const pointers
    QString(const _Ty* first,const _Ty* last)
        : BaseClass(first,last)
    {}
};

The only disadvantage – as you could notice – is no full support for original constructors. I actually think that it’s not a big problem, you can just insert the necessary constructor if it’s needed.

Observers

Some observers were created for testing purposes:

  1. CRegStatusObserver – assigned to print the status of the parsing process on the screen in percentage.
  2. CRegCountObserver – assigned to print the number of keys and the values on the screen.
  3. CRegPrintObserver – assigned to print all the keys and values on the screen.
  4. CRegFullObserver – assigned to store all the keys in std::map, where the name of the Registry key is key and the vector of all the values of this Registry key is the std::vector values.
  5. CRegObserversPool – assigned to make it possible to use several observers simultaneously.

It’s important to mention that these observers print information on the screen, but they can be used to print to the file or some other stream. For example, CRegCountObserver:

C
template<class charT,class streamT>
class CRegCountObserver:public IRegFileObserver<charT>
{
    size_t keysCount_;  
    size_t valuesCount_;
    streamT& out_;
public:
    CRegCountObserver(streamT& out)
        : keysCount_(0)
        , valuesCount_(0)
        , out_(out)
    {}
    ~CRegCountObserver()
    {
        out_ << "Keys count: "
             << keysCount_ 
             << "t Values count: " 
             << valuesCount_
             << "n";
    }
...
};

And some examples of its usage:

C
// 1
CRegCountObserver<char> screenObsr(std::cout);
// 2
std::stringstream strStream;
CRegPrintObserver<char,std::stringstream> stringObsr(strStream);
// 3
std::fstream fileStream;
CRegPrintObserver<char,std::fstream> fileObsr(fileStream);

The usage of other observers is the same.

Auto-tests description

All auto-test are represented in the one project, RegFileParserAutoTest.

The test is a console application developed with the Boost Testing Framework. Five complicated cases were chosen to be the test data: one for key name, two for value name, and two for value content.

There is one more case with the typical content of a reg file. So, we have six cases, and there are two versions of reg file format – ANSI and UNICODE (Regedit4 and Regedit5 correspondingly); each of our cases duplicates for two formats. As a result, we have 12 test files.

To control the results of parsing, we use a comparison of the original content and the content parsed and saved in memory using CRegPrintObserver:

C
template<class charT>
class TestRunner
{
protected:
    typedef std::basic_string<charT> stringT;
    typedef std::basic_stringstream<charT> stringstreamT;
    typedef std::basic_fstream<charT> fstreamT;
public:
    
    ...
    static void 
    RunTest(const std::wstring& fileName)
    {
        std::vector<char> buffer;
        ReadFile(fileName,&buffer);
        stringstreamT stream; 
        reg_parser::CRegPrintObserver<charT,stringstreamT> 
                    coutObserver(stream);
        reg_parser::CRegFileParser<charT> regParser(&coutObserver);
        // Run parsing
        if( !regParser.Parse( (charT*)&buffer[0] ) )
            throw std::exception("Parsing fail.");
        // Prepare data for comparison
        stringT parsedStr;
        AddRegHeader(&parsedStr);
        parsedStr += stream.str();
        stringT originalStr = stringT((charT*)&buffer[0]);
        // Trim unneeded symbols
        using namespace boost;
        trim_if(originalStr,is_any_of("nt "));
        trim_if(parsedStr,is_any_of("nt "));
        if( parsedStr != originalStr)
        {
            // Save to file result of parsing
            std::wstring parsedFileName = fileName + L"_parsed";
            fstreamT file(parsedFileName.c_str(), 
                          fstreamT::out | fstreamT::trunc);
            if( file.is_open() == false )
                throw std::exception("Can't create file for " 
                                     "result of parsing.");
            BOOST_SCOPE_EXIT( (&file) )
            {
                file.close();
            } 
            BOOST_SCOPE_EXIT_END
            file << parsedStr;
            throw std::exception("Parsed data not " 
                                 "equal to original data.");
        }
    }
    ...
};

Description for manual testing

Manual tests are represented in one project, RegFileParserTestCmd. The test is a console application implemented using Boost Program Options that has these parameters:

ShellScript
C:RegFileParserbinDebug>RegFileParserTestCmd.exe --help
Allowed options:
  --help                produce help message
  --reg_file arg        source reg file
  --print               Enable printing to the screen
  --count               Enable counting parsed keys and values
  --status              Enable printing status of parsing

It’s a pity that I don’t have enough time to add options to save the parsed content to a file, and using the save option like it is in autotest doesn’t seem to be aesthetic to me.

Registry export using Regedit

Registry export using Regedit
Registry export using Regedit

Conclusion

This article is a special piece of knowledge, so may be it’s not as systematic as it should be.

It was really interesting to learn boost spirit, and I managed to get the pleasure of my work with it and some aesthetic satisfaction – not just get my task done. After all, this discovered to be very effective; for example, the calculation of number of keys and values in a Registry file of 250 MB now takes a couple of seconds only.

So learn something new, and good luck to you in your development!

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