filenamehelpers.cpp

利用Windows API来计算MD5的MFC例程.计算MD5时主要用到了CryptAcquireContext、CryptCreateHash两个API

//*****************************************************************************
// FILE: FileNameHelpers.cpp
// DESC: Implementation of functions to extract file title and file path 
//       given a filename.
// 
// By Giovanni Dicanio <[e-mail]>
// 2008, September 26th
//*****************************************************************************


#include "stdafx.h"
#include "FileNameHelpers.h"            // Module header



namespace FileNameHelpers {


CString GetFilePath( LPCTSTR fileName )
{
    // Check input string (must be not null and not empty)
    ASSERT( fileName != NULL );
    ASSERT( *fileName != TEXT('\0') );

    // Scan the string from last character to first one.
    // Stop scanning when we find \ or : .
    // The left part will be the file path, the right part is the file title.

    // Start from the end of the string
    LPCTSTR pchCurrent = fileName + _tcslen( fileName ) - 1;

    // Just to make code more clear (I could have used just 'fileName' as
    // pointer to beginning of string...)
    LPCTSTR pchStart = fileName;

    while ( pchCurrent >= pchStart )
    {
        if ( *pchCurrent == TEXT('\\') )
        {
            // backslash not included in the path
            --pchCurrent;
            break;
        }
        else if ( *pchCurrent == TEXT(':') )
        {
            // colon included in the path
            break;
        }
        else
        {
            // Neither '\' nor ':' found, so we are still pointing
            // to file title characters. So we must move left one more.
            --pchCurrent;
        }
    }
    if ( pchCurrent < pchStart )
    {
        // No file path present - just return empty string
        return TEXT("");
    }

    // On success, at the exit of while loop, pchCurrent points to last character
    // of file path, i.e. the file path is defined by range
    // [pchStart, pchCurrent]
    int pathLength = static_cast< int >(pchCurrent - pchStart) + 1;
    return CString( pchStart, pathLength );
}


CString GetFileTitle( LPCTSTR fileName )
{
    // Check input string (must be not null and not empty)
    ASSERT( fileName != NULL );
    ASSERT( *fileName != TEXT('\0') );

    // Scan the string from last character to first one.
    // Stop scanning when we find \ or : .
    // The left part will be the file path, the right part is the file title.

    // Start from the end of the string
    LPCTSTR pchEnd = fileName + _tcslen( fileName ) - 1;

    // Start from the end of the string
    LPCTSTR pchCurrent = pchEnd;

    // If the last character is a \ or a :, then there is no title in input string
    if ( *pchCurrent == TEXT('\\') || *pchCurrent == TEXT(':') )
    {
        // No title
        return TEXT("");
    }

    // Move left - first character already processed
    --pchCurrent;

    // Just to make code more clear (I could have used just 'pszFileName' as
    // pointer to beginning of string...)
    LPCTSTR pchStart = fileName;

    while ( pchCurrent >= pchStart )
    {
        if ( *pchCurrent == TEXT('\\') || *pchCurrent == TEXT(':') )
        {
            // Neither backslash nor colon are included in file title
            ++pchCurrent;
            break;
        }

        // We did not find \ or :, so move left in search of them
        // (we are still pointing to file title characters)
        --pchCurrent;
    }
    if ( pchCurrent < pchStart )
    {
        // The input string was made by only title (no path), so return
        // the whole input string
        return fileName;
    }

    // On success, at the exit of while loop, pchCurrent points to first character
    // of file title, i.e. the file path is defined by range
    // [pchCurrent, pchEnd]
    int titleLength = static_cast< int >(pchEnd - pchCurrent) + 1;
    return CString( pchCurrent, titleLength );
}


} // namespace FileNameHelpers