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CPath - juggling file names made easy

, 9 Sep 2005 CPOL
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A wrapper class for path strings based on (and improving) the Shell Lightweight utility API.

Recent Changes (August 2005)

Introduction

CPath is a string class customized to handle path and file names on Windows.

Working with file names is often a pain:

  • Correct concatenation using &: file = path & subfolder & name;.
  • Modification: BuildRoot, AddExtension etc.
  • Splitting into components (path, file name, title, extension, parent folder, root, and individual elements).
  • Cleanup, like trimming, un- and requoting.
  • Read from / Write to Registry with one command.
  • Expanding / Collapsing Environment strings.
  • Detecting type of the path (IsRoot, IsURL, etc.) and a variety of root types (drive, long path, server, share, protocol, pseudo-protocol).
  • Basic file system operations: FileExists etc.
  • Frequent Helpers like GetModuleFileName.

The project includes a test application where you can play around, explore and test the functionality.

Sample screenshot

Design and Dependencies:

The main design goal was comfortable use. It is based on CString and uses the Shell Lightweight Path Helper API, so it is not suitable for portable applications.

Things you must know

Construction and Assignment (from any CString) will do some path cleanup. By default, this is: removing quotes, trimming spaces (inside and outside the spaces), collapsing self- and up-references (".." and "."), replacing UNC long path specification ("\\?\C:\") by the actual root, and expanding environment strings. See EPathCleanup for other options.

Extraction: CPath provides an operator LPCTSTR (similar to CString). CPath::GetStr() retrieves the path, and allows to apply "repacking" options. By default, paths exceeding MAX_PATH receive their UNC prefix. See EPathPacking for more options. Use CPath::GetStr(0) to retrieve the unmodified contained path as CString (avoids copy).

Error Handling: CPath functions usually fall back to a "sensible default handling". For methods accessing the file system, call GetLastError() to retrieve error information.

Things you might want to know

» Concatenate using '&': CPath path = CPath("C:\\temp") & "foo.txt";.

» Split the path into components:

String root      = path.GetRoot();
CPath   folder    = path.GetPath();
CString fileName  = path.GetName();
CString fileTitle = path.GetTitle();
CString ext       = path.GetExtension();

» Chain Commands: path.Trim().RemoveQuotes().

» Get Application Directory: nsPath::GetModuleFileName().GetPath().

Documentation

Complete documentation (generated by Doxygen) is available in the download (HTML / HTMLHelp).

Do you want to create similar documentation for your code? My Doxygen article tells you how.

Implementation Notes:

I didn't use CPathT, because the class is intended for a VC6 project (which won't be ported to VC7 very soon), and CPathT contains the same misfeatures as the Shell helper functions.

I did use CString, because it's well available outside of MFC projects (using WTL, or the "extract CString implementation" macro for DevStudio, or a CString clone class). Further, the guaranteed reference counting implementation allows for a convenient API without too much performance impact.

Like CString, CPath acts as an LPCTSTR if passed as an "unknown" argument to a function with a variable argument list. Remember, however, that this is not portable to other compilers.

Change Log

Please Note: Breaking changes were introduced with the March 2005 update, when merging two slightly distinct branches. Unfortunately, I opted for keeping my code base intact, not thinking of the article published. (I hope you don't mind too much and you still like the update.) All changes will cause a compiler error.

  • June 20, 2004: Initial release.
  • June 22, 2004
    • fixed: nsPath::CPath::MakeSystemFolder implements unmake correctly.
    • added: nsPath::CPath::MakeSystemFolder and nsPath::CPath::SearchOnPath set the Windows error code to zero if the function succeeds (thanks Hans Dietrich).
    • fixed: nsPath::CPath compiles correctly with warning level -W4.
  • Mar 3, 2005
    • Doxygen class member documentation now uses groups for better orientation.
    • fixed: eppAutoQuote bug in GetStr (thanks Stlan).
    • Added:
      • FromRegistry, ToRegistry
      • GetRootType
      • GetRoot has a new implementation.
      • MakeAbsolute, MakeRelative, MakeFullPath
      • EnvUnexpandRoot, EnvUnexpandDefaultRoots.
    • Breaking changes (sorry)
      • GetRoot -> ShellGetRoot (to distinct from the new, extended GetRoot implementation).
      • GetFileName --> GetName (consistency).
      • GetFileTitle --> GetTitle (consistency).
      • Made the creation functions independent functions in the nsPath namespace (they are well tugged away in the namespace so conflicts are avoided anyway).
  • Mar 17, 2005
    • Fixed bug in GetFileName (now: GetName): if the path ends in a backslash, GetFileName did return the entire path instead of an empty string (thanks woodland).
  • Aug 25, 2005
    • Fix: GetStr() did not Quote the string if it contains spaces (even if eppAutoQuote was given, which is the default).

      Note: this fix changes default behavior, and might break existing code in some circumstances (such as passing the path.GetStr() to a function that does not like quotes).

    • Added SplitRoot (separate first element from rest).
    • Added IsDot, IsDotDot (to check for ".", ".." path), and IsDotty (true if "." or ".."). The names are silly - suggestions?
    • Added IsValid, checking for Windows naming conventions.
    • fixed incompatibility with CStdString (causing an access violation when assigning an empty path).

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

peterchen
Klippel
Germany Germany
Peter is tired of being called "Mr. Chen", even so certain individuals insist on it. No, he's not chinese.
 
Peter has seen lots of boxes you youngsters wouldn't even accept as calculators. He is proud of having visited the insides of a 16 Bit Machine.
 
In his spare time he ponders new ways of turning groceries into biohazards, or tries to coax South American officials to add some stamps to his passport.
 
Beyond these trivialities Peter works for Klippel[^], a small german company that wants to make mankind happier by selling them novel loudspeaker measurement equipment.
 

Where are you from?[^]



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Comments and Discussions

 
QuestionOut of memory Pinmemberswuk6-Oct-11 8:34 
QuestionAny updates? Pinmemberroel_30-Jul-08 10:45 
AnswerRe: Any updates? Pinmemberroel_31-Jul-08 4:09 
GeneralRe: Any updates? Pinmemberpeterchen13-Apr-09 14:29 
GeneralRe: Any updates? PinmemberMichael Stammberger9-May-09 2:10 
GeneralRe: Any updates? Pinmemberpeterchen6-Jul-09 0:10 
GeneralUnicode, sample project & ExpandEnvironmentStrings [modified] PinmemberDavid McMinn26-Nov-07 5:10 
GeneralRe: Unicode, sample project & ExpandEnvironmentStrings Pinmemberpeterchen26-Nov-07 7:56 
GeneralRe: Unicode, sample project & ExpandEnvironmentStrings PinmemberDavid McMinn26-Nov-07 23:06 
QuestionStatic Function? PinmemberJoel Matthias14-Sep-06 8:47 
AnswerRe: Static Function? Pinmemberpeterchen15-Sep-06 9:18 
GeneralProblems with UNICODE. PinmemberWilliam GS20-Jul-06 14:12 
GeneralRe: Problems with UNICODE. Pinmemberpeterchen15-Sep-06 9:20 
GeneralA time saver! PinmemberJörgen Sigvardsson12-Jan-06 3:05 
GeneralRe: A time saver! Pinmemberpeterchen12-Jan-06 23:37 
Generalcompare path.GetPath() == _T("") always false PinmemberMichael Stammberger28-Nov-05 1:35 
GeneralRe: compare path.GetPath() == _T("") always false Pinmemberpeterchen28-Nov-05 4:50 
GeneralSilly Names... Nah! PinmemberJohann Gerell12-Sep-05 13:51 
Generalseems it doesn't support validation check PinmemberHeartFriend18-Aug-05 1:07 
GeneralValidity Check - suggestions Pinmemberpeterchen18-Aug-05 7:44 
there is "Exists", which checks if the file / directory exists, but I guess this is not what you are looking for.
 
A simple validity check would be (I think):
 
bool CPath::IsValidPath(bool allowXXLPath = false)
{
  if (!allowXXLPath && m_path.getLength() > 255)
     return false;
 
  // invalid characters:
  int idx = m_path.FindOneOf("\\/:*?\"<>|");
  if (idx >= 0)
    return false;
 
  return true;
}
 
This checks for the characters flagged "invalid" on an NTFS drive I'm not sure about the following things:
- Invalid characters is probably file system dependent
- Which file systems allow Unicode?
- no check is made for valid protocols, different restrictions for server / share names, etc.
 
Recommendations / Links?
 

Pandoras Gift #44: Hope. The one that keeps you on suffering.
aber.. "Wie gesagt, der Scheiss is' Therapie"
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GeneralProblem converting demo app to console output Pinmemberdefenestration4-Aug-05 2:05 
GeneralCPath path(&quot;&quot;); causes exception Pinmemberdefenestration4-Aug-05 1:32 
GeneralRe: CPath path(&quot;&quot;); causes exception Pinmemberpeterchen4-Aug-05 2:21 
GeneralRe: CPath path(&quot;&quot;); causes exception Pinmemberdefenestration4-Aug-05 9:26 
GeneralRe: CPath path(""); causes exception Pinmemberpeterchen4-Aug-05 11:03 

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