Title: TMapTextfile Class
Question: In Delphi you have many ways to manipulate text files. But all of these have a handicap: You must read the whole file (StringList)
or you can only access data sequential (Assign/Readln).
Answer:
The Windows API provides the so called Memory Mapped Files (MMF). Windows self uses MMFs to load EXE or DLL. Therefore the mechanism is very efficient, but simple to handle. The only handicap is, that you must know the size of the file before you access it. This means for typical text files, that the operation is normally limited to read from the file or manipulate inside.
The class TMapTextfile wraps the neccesary API calls and povides efficent functions for accessing the data.
Installation:
Copy MAPTEXTFILE.PAS into your library path. Use it. 8-)
Tip for using this class under Delphi 3:
Note that Delphi has changend the definition of CARDINAL from D3 to D4. In D3 CARDINAL is a subset of INTEGER (0..MaxInt - 31 Bit wide), in D4 CARDINAL is the full range (32 bit wide).
TMapTextfiles provides the following properties and methods:
Create Creates an instance of the class
Destroy Destroys the instance
Open Opens a file as a memory mapped file.
filename = name of the file
mode = open mode:
mmRead = Open only for read exclusive
mmReadShared = Open for read,
share with other
mmReadWrite = Open for read and wrie
Returns INVALID_HANDLE_VALUE if the file not
exist.If the result 0 all is OK.
NOTE:
1. The file must exist!
2. You cannot write behind the end of the file.
3. You cannot write behind the end of the file.8-)
Close Close the memory mapped file and frees all handles.
EndOfFile Returns TRUE, if the End of the file is reached.
GetSize Returns the Size of the file in Bytes
GetPos Returns the actual file read/write position
NOTE: Position 0 is the start of the file
SetPos Sets the actual read/write position
NOTE: Position 0 is the start of the file
ReadChar Reads a character from the actual read/write position.
The r/w position is incremented.
ReadString Returns a string, starting at the actual r/w pos.
The string is delimited by chars by ESC (#27) and TAB. The r/w position moves to
the end of the string, delimiter chararcters
(Cr/LF) are skipped.
ReadStringL Same as ReadString, but return length of the string
len = number of characters that we has read
ReadLn Same as ReadSring, but like the classic Procedure.
ReadCharAt Reads a charater from an arbitray position.
The r/w position is NOT moved!
pos = position to read from (0 = start of file!)
ReadChars Reads a line of charactes from the MMF.
The r/w position is NOT moved!
str = The buffer to read to
pos = position to read from (0 = Start of file!)
len = number of characters to read.
ReadStringAt Returns a string, starting at an arbitray pos.
The string is delimited by characters but not by ESC (#27) and TAB. The r/w position is
NOT moved.
FindString Findes a substring in the MMF and Returns the pos.
str = the substring to search for
pos = position to start the search (0 = start of
the file)
max = position to end the search. If this is 0 or
less then 0 the end of the file is the limit.
Returns the position of the substring or -1 if the
substring is not found.
FindStringCI Same as FindString, but works case insensitive
FindWildCard Same as FindString, but supports wildcard search.
str = the substring to search for
pos = position to start the search (0 = start
of the file)
max = position to end the search. If this is 0
or less then end of file is the limit.
wild = the character used as wildcard (i.e. "*")
joker = the character used as joker (i.e. "?")
Returns the position of the substring or -1 if the
substring is not found.
ReadBytes Reads a number of bytes to a anonymous variable.
The r/w position is NOT moved!
b = the anonymous variable
pos = position to read from (0 = start of the file)
len = number of bytes to read.
WriteBytes Writes a number of bytes to the file.
NOTE: You can not write behind the end of file!!!
b = the anonymous variable
pos = position to write to (0 = start of the file)
len = number of bytes to write
GetPtr Returns the Position as Pointer (Pchar) to the view
pos = Wanted position
WARNING: Be carefull! Normally you dont need this!
-----------------------------------------------------------------
unit MapTextfile;
interface
uses Classes, Windows;
// Modes for open
type tMapMode = (mmRead, mmReadShared, mmReadWrite);
// the class
type TMapTextfile = class
private
f_file: THandle;
f_MMF: THandle;
f_size: INTEGER;
f_view: PByte;
f_data: PChar;
f_pos: INTEGER;
f_open: BOOLEAN;
function CalcPos (pos: INTEGER): PCHAR;
function Find (const str: string;
pos, max: integer; ci: boolean): INTEGER;
public
constructor Create;
destructor Destroy; override;
function Open (const filename: string; mode: tMapMode): INTEGER;
procedure Close;
function ReadChar: CHAR;
function ReadString: string;
function ReadStringL (var len: Longint): string;
procedure ReadLn (var str: string);
function ReadCharAt (pos: Longint): CHAR;
procedure ReadChars (str: PCHAR; pos, len: LONGINT);
function ReadStringAt (pos: Longint): string;
function GetSize: Longint;
function GetPos: Longint;
procedure SetPos (pos: Longint);
function EndOfFile: Boolean;
function FindString (const str: string;
pos, max: INTEGER): INTEGER;
function FindStringCI (const str: string;
pos, max: INTEGER): INTEGER;
function FindWildCard (const str: string;
pos, max: INTEGER;
wild, joker: CHAR): INTEGER;
procedure ReadBytes (var b; pos, len: LONGINT);
procedure WriteBytes (var b; pos, len: LONGINT);
function GetPtr (pos: Longint): PChar;
end;
implementation
constructor TMapTextfile.Create;
begin
f_open:= FALSE;
end;
function TMapTextfile.Open (const filename: string; mode: tMapmode): INTEGER;
var m1, m2, m3, m4: CARDINAL;
begin
f_open:= FALSE;
case mode of
mmRead: begin
m1:= GENERIC_READ;
m2:= PAGE_READONLY;
m3:= FILE_MAP_READ;
m4:= FILE_SHARE_READ or FILE_SHARE_WRITE;
end;
mmReadShared: begin
m1:= GENERIC_READ;
m2:= PAGE_READONLY;
m3:= FILE_MAP_READ;
m4:= FILE_SHARE_READ;
end;
else begin
m1:= GENERIC_READ + GENERIC_WRITE;
m2:= PAGE_READWRITE;
m3:= FILE_MAP_WRITE;
m4:= FILE_SHARE_READ;
end;
end;
f_file:= CreateFile (PCHAR (FileName), m1, m4, nil,
OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
// all ok?
if f_file = INVALID_HANDLE_VALUE then begin
Result:= Integer (INVALID_HANDLE_VALUE);
EXIT;
end;
try
// how big is the file?
f_size:= GetFileSize (f_file, nil);
// generate memory mapped file object
f_MMF:= CreateFileMapping (f_file, nil, m2, 0, f_size, nil);
// all ok?
if f_MMF = 0 then begin Result:= -1; EXIT; end;
finally
// We need the file handle no longer, so we can free it.
CloseHandle (f_file);
end;
// Status: file handle freed, MMF handle activ
try
// create a view (a "window" to the memory) to the MMF object
f_View:= MapViewOfFile (f_MMF, m3, 0, 0, f_size);
// all ok?
if f_view = nil then begin Result:= -1; EXIT; end;
finally
// handle to the mmf object is no longer needed, so lets free it
CloseHandle (f_MMF);
end;
f_data:= PCHAR (f_view); // Pointer to map view
f_pos:= 0; // initial start position of the R/W-Pointer
f_open:= True; // Yes, we're open for buisiness
Result:= 0;
// Status: file handle freed, mmf handle freed, view is active
end;
destructor TMapTextfile.Destroy;
begin
if f_open then Close;
inherited;
end;
procedure TMapTextfile.Close;
begin
if f_open then begin
UnmapViewOfFile (f_View); // Free the view
f_open:= FALSE;
end;
end;
function TMapTextfile.CalcPos (pos: INTEGER): PCHAR;
// internal function for calculate read/write pos
// to physical memory
begin
Result:= nil;
if f_open then begin
if pos if pos f_size then pos:= f_size;
result:= PCHAR (LONGINT(f_view) + pos);
end;
end;
function TMapTextfile.ReadChar: CHAR;
// Read a char
begin
Result:= #0;
if f_open then begin
f_data:= PCHAR (LONGINT(f_view) + f_pos);
Result:= f_data^;
INC (f_pos);
end;
end;
function TMapTextfile.ReadStringL (var len: Longint): string;
begin
Result:= '';
len:= 0;
if f_open then begin
f_data:= PCHAR (LONGINT(f_view) + f_pos);
while (f_pos case f_data^ of
#0..#31: case f_data^ of
#9,
#27: Result:= Result + f_data^;
// including Tab and Escape
#10: begin INC (f_pos); EXIT; end;
// Linefeed terminates
#13: begin // Carriage Return terminates
INC (f_pos);
INC (f_data);
// is there a trailing Linefeed?
if f_data^ = #10 then INC (f_pos);
EXIT;
end;
end;
else begin
Inc (len);
Result:= Result + f_data^;
end;
end;
INC (f_pos);
INC (f_data);
end;
end;
end;
function TMapTextfile.ReadString: string;
begin
Result:= '';
if f_open then begin
f_data:= PCHAR (LONGINT(f_view) + f_pos);
while (f_pos case f_data^ of
#0..#31: case f_data^ of
#9,
#27: Result:= Result + f_data^;
// including Tab and Escape
#10: begin INC (f_pos); EXIT; end;
// Linefeed terminates
#13: begin // Carriage Return terminates
INC (f_pos);
INC (f_data);
if f_data^ = #10 then INC (f_pos);
EXIT;
end;
end;
else begin
Result:= Result + f_data^;
end;
end;
INC (f_pos);
INC (f_data);
end;
end;
end;
function TMapTextfile.ReadCharAt (pos: LONGINT): CHAR;
begin
if f_open then Result:= CalcPos (pos)^
else Result:= #0;
end;
procedure TMapTextfile.ReadChars (str: PCHAR; pos, len: LONGINT);
var i: INTEGER;
p: PCHAR;
begin
if f_open then begin
if len i:= 0;
p:= CalcPos (pos);
while (i str^:= p^;
INC (str);
INC (p);
INC (i);
end;
end;
end;
procedure TMapTextfile.ReadBytes (var b; pos, len: LONGINT);
var p: PCHAR;
begin
if f_open then begin
p:= CalcPos (pos);
Move (p^, b, len);
end;
end;
procedure TMapTextfile.WriteBytes (var b; pos, len: LONGINT);
var p: PCHAR;
begin
if f_open then begin
p:= CalcPos (pos);
Move (b, p^, len);
end;
end;
function TMapTextfile.ReadStringAt (pos: LONGINT): string;
var i: INTEGER;
p: PCHAR;
begin
Result:= '';
if f_open then begin
p:= CalcPos (pos);
i:= 0;
while (i case p^ of
#0..#31: case p^ of
#9,
#27: Result:= Result + p^;
// including Tab and Escape
#10,
#13: EXIT;
// Linefeed and Carriage Return terminates
end;
else Result:= Result + p^;
end;
INC (p);
end;
end;
end;
procedure TMapTextfile.ReadLn (var str: string);
begin
str:= ReadString;
end;
function TMapTextfile.GetSize: LONGINT;
begin
if f_open then Result:= f_size
else Result:= -1;
end;
function TMapTextfile.GetPos: LONGINT;
begin
if f_open then Result:= f_pos
else Result:= -1;
end;
procedure TMapTextfile.SetPos (pos: LONGINT);
begin
if f_open then begin
if pos if pos f_size then pos:= f_size;
f_pos:= pos;
end;
end;
function TMapTextfile.EndOfFile: BOOLEAN;
begin
if f_open then Result:= f_pos = f_size
else Result:= TRUE;
end;
function TMapTextfile.Find (const str: string;
pos, max: integer; ci: BOOLEAN): INTEGER;
// internal search function
// str = string to find
// pos = startpos
// max = maximum length to search, -1 = until file end
// ci = if true the Case insensitive
var s, l1, j, k: INTEGER;
p, x: PCHAR;
begin
Result:= -1;
if f_open then begin
if max if pos if pos max then EXIT;
x:= PCHAR (str);
p:= PCHAR (f_view);
l1:= Length (str);
if (l1 0) then begin
s:= pos;
if ci then begin
repeat (* 1 *)
j:= 0; k:= 1;
while (s+j (upcase(x[j]) = upcase(p[s+j])) do begin
INC (j);// Inc (k);
if (j = l1) then begin Result:= s; EXIT; end;
end;
INC (s, k);
until s = f_size;
end else begin
repeat (* 1 *)
j:= 0; k:= 1;
while (s+j and (j and (x[j] = p[s+j]) do begin
INC (j); Inc (k);
if (j = l1) then begin Result:= s; EXIT; end;
end;
INC (s, k);
until s = f_size;
end;
end;
end;
end;
function TMapTextfile.FindString (const str: string;
pos, max: integer): INTEGER;
begin
Result:= Find (str, Pos, max, False);
end;
function TMapTextfile.FindStringCI (const str: string;
pos, max: INTEGER): integer;
begin
Result:= Find (str, Pos, max, True);
end;
function TMapTextfile.FindWildCard (const str: string;
pos, max: INTEGER;
wild, joker: CHAR): INTEGER;
// Like FindString, using wildcards
var s, l1, j, k: Integer;
p, x: PChar;
begin
Result:= -1;
if f_open then begin
if max if pos if pos max then EXIT;
x:= PChar (str);
p:= PChar (f_view);
l1:= 0; while (x[l1] #0) do INC (l1);
if (l1 0) then begin
s:= pos;
repeat (* 1 *)
j:= 0; // j = counter in str
k:= 0; // k = counter in MMF
while (s + k and (j and ((x[j] = p[s + k]) OR (x[j] = joker)) do begin
Inc (j);
Inc (k);
if (x[j] = wild) and (j Inc (j);
// search char
while (s + k x[j]) do Inc (k);
end;
if (j = l1) then begin Result:= s; Exit; end;
end;
INC (s);
until s = f_size;
end;
end;
end;
function TMapTextfile.GetPtr (pos: Longint): Pchar;
// Returns the Position as Pointer (Pchar) to the view
begin
Result:= CalcPos (pos);
end;
end.