I have the full path name of a given folder for e.g.
c:\foo\bar
Now I would like to reference a file inside c:\foo named baz.txt,
c:\foo\bar\..\baz.txt
I am currently using the .. path operator to go down one level and get the file that I need.
Is there a function that can do path manipulations, for e.g. UpOneLevel(str) -> str ? I know I can write one by splitting the string and removing the last token, but I would rather it be a built-in / library function so I don't get into trouble later if there are for e.g. escaped backslashes.
Use the ExpandFileName function:
var
S: string;
begin
S := 'c:\foo\bar\..';
S := ExpandFileName(S);
ShowMessage(S);
end;
The message from the above example will show the c:\foo path.
Look at ExtractFilePath() and ExtractFileDir(). These are available in just about all Delphi versions, particularly those that do not have TDirectory, IOUtils, etc.
And before anyone says it, these work just fine whether the path ends with a filename or not. ForceDirectories() uses them internally to walk backwards through a hierarchy of parent folders, for example.
This answer is valid for Delphi XE +
Use the TDirectory class of the IOutils unit, which have the method GetParent, like this::
uses IOUtils;
procedure TForm1.Button1Click(Sender: TObject);
var
s: string;
begin
s := 'c:\foo\bar';
ShowMessage(TDirectory.GetParent(s));
end;
In older versions
Look at the other answers.
You can take a look at TPathBuilder record in SvClasses unit from delphi-oop library. This unit does not support Delphi 2007 but TPathBuilder implementation is compatible with this Delphi version. Example usage:
var
LFullPath: string;
begin
LFullPath := TPathBuilder.InitCustomPath('c:\foo\bar').GoUpFolder.AddFile('baz.txt').ToString;
//LFullPath = c:\foo\baz.txt
Related
My problem is not exporting a function, but importing it. I know for sure that both the function and DLL both work because I have used a hard-coded path to point to the DLL.
This is what is currently working:
function RoamingAppDataPath: String; external 'C:\Users\Peter\AppData\Roaming\ss\Application\ss.dll';
However I need to point to the DLL with a dynamic value so what I tried to do is
Declare a global variable (DLLPath: String)
Assign DLLPath the value - RoamingAppDataPath+'\ss\Application\ss.dll'
Note: RoamingAppDataPath is a function that outputs the path to the roaming app data folder.
The code I am trying to run is:
function RoamingAppDataPath: String; external DLLPath;
When I compile the code, Delphi is telling me that it is expecting a constant expression:
E2026 Constant expression expected
What is the work around for this?
You have to bind at runtime and that means you need to use LoadLibrary and GetProcAddress:
var
lib: HMODULE;
RoamingAppDataPath: function: string;
lib := LoadLibrary(dllfilename);
if lib=0 then
RaiseLastOSError;
Pointer(RoamingAppDataPath) := GetProcAddress(lib, 'RoamingAppDataPath');
And then you can call it:
radp := RoamingAppDataPath;
Some comments:
I don't know why you write this function when it exists in standard system libraries.
Using string across DLL boundaries is liable to fail. You need to be using ShareMem and make sure that all code is built with the same Delphi version. Better to allocate the buffer in the calling code.
Even if you would be able to use a Variable, you would nowhere be able to set a value to DLLPATH, since already initalization would not be used if a static DLL can not be used.
You will have to use dynamic loadingif you want to define the path for the DLL.
procedure Test;external 'Notexists.DLL';
var
Form2: TForm2;
implementation
{$R *.dfm}
procedure TForm2.Button1Click(Sender: TObject);
begin
test;
end;
initialization
Showmessage('Hallo'); // will never be seen if test is used.
Hello recently I replace TextFile with TFileStream. I never use it so I have small problem with it.
How can I add someting to my file after I assign it to variable?
How can I read someting form that file?
I need defined line form that file so I was doing something like that:
var linia_klienta:array[0..30] of string;
AssignFile(tempPlik,'klienci.txt');
Reset(tempPlik);
i:=0;
While Not Eof(tempPlik) do
begin
Readln(tempPlik,linia_klient[i]);
inc(i);
end;
CloseFile(tempPlik);
Then when line two is needed I simply
edit1.text = linia_klienta[1];
If you need to read a text file and access each line, try instead using a TStringList class with this class you can load a file, read the data (accesing each line using a index) and save the data back.
something like this
FText : TStringList;
i : integer;
begin
FText := TStringList.Create;
try
FText.LoadFromFile('C:\Foo\Foo.txt');
//read the lines
for i:=0 to FText.Count-1 do
ProcessLine(FText[i]); //do something
//Add additional lines
FText.Add('Adding a new line to the end');
FText.Add('Adding a new line to the end');
//Save the data back
FText.SaveToFile('C:\Foo\Foo.txt');
finally
FText.Free;
end;
end;
end;
I newer versions of Delphi you can use TStreamReader / TStreamWriter here is an example of using TStreamReader ... this is only for manipulating text files
var
SR : TStreamReader;
line : String;
begin
SR := TStreamReader.Create('D:\test.txt');
while not (SR.EndOfStream) do
begin
line := SR.ReadLine;
ShowMessage(line);
end;
SR.Free;
end;
TStream and its immediate descendants are mostly low-level access class. They mostly deal with generic buffers. There are some more specialized classes that descend from or use a stream to perform higher level tasks.
Since Delphi 1 TReader and TWriter could be used to read and write Delphi types directly (inlcuding strings), but they were not designed to handle "line-oriented" files (unluckily they were designed too much with component properties streaming in mind, not as a general purpose framework).
Turbo Power SysTools has a nice TStAnsiTextStream class that implements line-oriented access to text files in a way similar to that of TextFile. Since Delphi 2009 new classes (see opc0de answer) implement the same kind of access without the need of third party libraries (moreover they support different encodings thanks to Delphi 2009 extend codepage support, including Unicode).
Depending with what you want to do, its the stream class you need.
Do you want to work with text (characters with break-lines and end-of-line characters) data ?
OR, do you want to work with binary data ?
I see you are using an array of char, instead, of a string.
Do you really want to use character data as if it was binary ?
Sometimes, some applications require that case.
The "A" in A-links and A-keywords stands for "associative". This is because A-link keywords are actually not keywords at all. They are more like link or jump targets (known as anchors in H&M). They are never visible to the user like index keywords. They are known as "associative" because they are not absolute targets.
How to call CHM help by A-keyword in Delphi XE?
The Windows API function HTMLHelp is directly available in the Windows unit. You want the HH_ALINK_LOOKUP command.
If you're using the help system from HelpInfts, the HtmlHelpViewer unit contains THtmlHelpViewer, which contains various methods for dealing with ALinks - specifically LookupALink. Unfortunately, there seems to be no documentation of the type, so you'll have to drill down into the source yourself (it is quite simple, so you should not have too much trouble).
I don't see any support for it in helpintfs.
I tried myself once with D2006/FPC, and commited the results to FPC:
You'll need the unit "htmlhelp" from
http://svn.freepascal.org/cgi-bin/viewvc.cgi/trunk/packages/winunits-base/src/htmlhelp.pp?view=co
and do some ansi->unicode translation in that file (e.g. change all pchar to pansichar, replacint ptr(u)int with native(u)int etc)
This file has a constant HH_ALINK_LOOKUP that afaik can be used to lookup alinks and keywords.
This can be passed to the htmlhelp function. The below code is from Free Pascal and uses ansistrings, but it probably works analogous in Delphi
{$apptype console}
Uses HTMLHelp;
var
keyword : ansistring;
HelpfileName : AnsiString;
htmltopic : AnsiString;
res : Integer;
ah : PHH_AKLINK ;
Begin
Helpfilename:='rtl.chm';
keyword:='Sysutils' ;
New(ah);
fillchar(ah^,sizeof(ah^),#0);
ah.cbstruct:=sizeof(tagHH_AKLINK);
ah.fReserved := FALSE ;
ah.pszKeywords :=pansichar(keyword);
ah.pszUrl := NIL ;
ah.pszMsgText :='Text succes' ;
ah.pszMsgTitle :='Text fail';
ah.pszWindow := NIL ;
ah.fIndexOnFail:= false;
Res:=HtmlHelpA(0,pansichar(helpfilename) ,HH_DISPLAY_INDEX,PTRUINT(PAnsiChar(Keyword)));
// keyword search seems to have same effect.
Res:=HtmlHelpA(0,pansichar(helpfilename) ,HH_ALINK_LOOKUP,PTRUINT(AH));
writeln(ah.pszkeywords);
writeln(ah.pszurl);
writeln(ah.pszmsgtext);
writeln(ah.pszmsgtitle);
writeln(ah.pszwindow);
writeln(res);
readln;
end.
What is the easiest way to create and save string into .txt files?
Use TStringList.
uses
Classes, Dialogs; // Classes for TStrings, Dialogs for ShowMessage
var
Lines: TStrings;
Line: string;
FileName: string;
begin
FileName := 'test.txt';
Lines := TStringList.Create;
try
Lines.Add('First line');
Lines.Add('Second line');
Lines.SaveToFile(FileName);
Lines.LoadFromFile(FileName);
for Line in Lines do
ShowMessage(Line);
finally
Lines.Free;
end;
end;
Also SaveToFile and LoadFromFile can take an additional Encoding in Delphi 2009 and newer to set the text encoding (Ansi, UTF-8, UTF-16, UTF-16 big endian).
Actually, I prefer this:
var
Txt: TextFile;
SomeFloatNumber: Double;
SomeStringVariable: string;
Buffer: Array[1..4096] of byte;
begin
SomeStringVariable := 'Text';
AssignFile(Txt, 'Some.txt');
Rewrite(Txt);
SetTextBuf(Txt, Buffer, SizeOf(Buffer));
try
WriteLn(Txt, 'Hello, World.');
WriteLn(Txt, SomeStringVariable);
SomeFloatNumber := 3.1415;
WriteLn(Txt, SomeFloatNumber:0:2); // Will save 3.14
finally CloseFile(Txt);
end;
end;
I consider this the easiest way, since you don't need the classes or any other unit for this code. And it works for all Delphi versions including -if I'm not mistaken- all .NET versions of Delphi...
I've added a call to SetTextBuf() to this example, which is a good trick to speed up textfiles in Delphi considerably. Normally, textfiles have a buffer of only 128 bytes. I tend to increase this buffer to a multiple of 4096 bytes. In several cases, I'va also implemented my own TextFile types, allowing me to use these "console" functions to write text to memo fields or even to another, external application! At this location is some example code (ZIP) I wrote in 2000 and just modified to make sure it compiles with Delphi 2007. Not sure about newer Delphi versions, though. Then again, this code is 10 years old already.These console functions have been a standard of the Pascal language since it's beginning so I don't expect them to disappear anytime soon. The TtextRec type might be modified in the future, though, so I can't predict if this code will work in the future... Some explanations:
WA_TextCustomEdit.AssignCustomEdit allows text to be written to CustomEdit-based objects like TMemo.
WA_TextDevice.TWATextDevice is a class that can be dropped on a form, which contains events where you can do something with the data written.
WA_TextLog.AssignLog is used by me to add timestamps to every line of text.
WA_TextNull.AssignNull is basically a dummy text device. It just discards anything you write to it.
WA_TextStream.AssignStream writes text to any TStream object, including memory streams, file streams, TCP/IP streams and whatever else you have.
Code in link is hereby licensed as CC-BY
Oh, the server with the ZIP file isn't very powerful, so it tends to be down a few times every day. Sorry about that.
The IOUtils unit which was introduced in Delphi 2010 provides some very convenient functions for writing/reading text files:
//add the text 'Some text' to the file 'C:\users\documents\test.txt':
TFile.AppendAllText('C:\users\documents\text.txt', 'Some text', TEncoding.ASCII);
Or if you are using an older version of Delphi (which does not have the for line in lines method of iterating a string list):
var i : integer;
begin
...
try
Lines.Add('First line');
Lines.Add('Second line');
Lines.SaveToFile(FileName);
Lines.LoadFromFile(FileName);
for i := 0 to Lines.Count -1 do
ShowMessage(Lines[i]);
finally
Lines.Free;
end;
If you're using a Delphi version >= 2009, give a look to the TStreamWriter class.
It will also take care of text file encodings and newline characters.
procedure String2File;
var s:ansiString;
begin
s:='My String';
with TFileStream.create('c:\myfile.txt',fmCreate) do
try
writeBuffer(s[1],length(s));
finally
free;
end;
end;
Care needed when using unicode strings....
Subj. I'd like to use strings instead of PChar because that spares me much casting, but if I just do
procedure SomeExternalProc(s: string); external SOMEDLL_DLL;
and then implement it in some other project with non-shared memory manager:
library SeparateDll;
procedure SomeExternalProc(s: string);
begin
//a bla bla bla
//code here code here
end;
I have (formally) no guarantee Delphi does not decide for whatever reason to alter the string, modify its reference counter, duplicate or unique it, or whatever else. For example
var InternalString: string;
procedure SomeExternalProc(s: string);
begin
InternalString := s;
end;
Delphi increments refcounter and copies a pointer, that's it. I'd like Delphi to copy the data. Does declaring the parameter as "const" make it safe for that reason? If not, is there a way to do it? Declaring parameter as PChar doesn't seem to be a solution because you need to cast it every time:
procedure SomeExternalProc(s: Pchar); forward;
procedure LocalProc;
var local_s: string;
begin
SomeExternalProc(local_s); //<<--- incompatible types: 'string' and 'PAnsiChar'
end;
That would probably work, as long as you only ever use your DLL from code compiled in the same version of Delphi. The internal format of string has been known to change between releases, and you have no formal guarantee that it won't change again.
If you want to avoid having to cast everywhere you use it, try wrapping the function, like this:
procedure SomeExternalProc(s: Pchar); external dllname;
procedure MyExternalProc(s: string); inline;
begin
SomeExternalProc(PChar(local_s));
end;
Then in your code, you call MyExternalProc instead of SomeExternalProc, and everyone's happy.
If both the app and the DLL are written in the same Delphi release, just use shared memory manager (more details here).
If one side is written in a different language than there's no other way but to use PChar or WideString (WideStrings are managed by the COM memory manager).
Or you can write a wrapper function:
procedure MyExternalProc(const s: string);
begin
SomeExternalProc(PChar(s));
end;
Just to add a single fact:
Delphi allows you to simply assign PChar to a string so on the DLL side you don't need any typecast:
function MyDllFunction(_s: PChar): integer;
var
s: string;
begin
s := _s; // implicit conversion to string
// now work with s instead of the _s parameter
end;
This also applies for passing PChar as a parameter to a function that expects a (by value) string.
I recommend to use an alternative memory manager such as RecyclerMM or FastMM. They doesn't require any external shared MM dll's and allows you to pass strings to the dlls safely. As a bonus, you may get a nice performance improvement in whole application.
FastMM is used as a default memory manager in Delphi 2006 and above. Also it's a good tool to search the memory-leaks.