EXAMPLE PROCEDURES THAT USE THE BRUTE-FORCE SEARCH ALGORITHM, FOR
READING A SOURCE FILE AND WRITING ALL OTHER TEXT BESIDES TEXT SPECIFIED BY
THE USER TO ANOTHER FILE (NEED DEBUGGING BUT THEY'RE CLOSE...)
function TParseForm.LoadSourceExclusive: Integer;
{OK we're duplicating some code here but, search methods for grabbing the bulk
of a file SHOULD be different, and though we might have integrated what
happens here with LoadSourceExclusive above, this way is MUCH easier to follow}
var
startMatch: Boolean;
i, filePos: LongInt;
tempArray: array[0..pattArrayLen] of Char;
bytesRead, bytesWritten, counter: Integer;
lastCharsPos: LongInt;
readFlag: Integer;
begin
filePos := 0;
counter := 0;
{assign a file handle and open input file...}
AssignFile(srcFile, srcFileName);
{assign a file handle and open output file....}
AssignFile(destFile, destFileName);
try
{try to open source file...}
reset(srcFile, 1);
fileBytes := FileSize(srcFile);
lastCharsPos := fileBytes - LongInt(prePattLen);
{and try to open destination file...}
reWrite(destFile);
try
repeat
startMatch := True;
while (startMatch = True) do
begin
blockRead(srcFile, tempArray, prePattLen, bytesRead);
Inc(counter);
Inc(filePos);
i := 1;
repeat
if not(preSequence[i] = tempArray[i - 1]) then
begin
startMatch := False;
break;
end;
Inc(i);
until (i = prePattLen);
if (i = prePattLen) then
begin
startMatch := True;
break;
end;
end;
if (startMatch = True) then
begin
filePos := ReadUntilSuccSeq;
end
else
begin
if (filePos = 1) then Write(destFile, tempArray[0]);
if (((counter mod prePattLen) = 0)
or (filePos = lastCharsPos)) then
begin
for i := 0 to (prePattLen - 1) do
begin
Write(destFile, tempArray[i]);
end;
end;
Seek(srcFile, filePos);
end;
until (filePos >= fileBytes);
finally
begin
closefile(srcFile);
closeFile(destFile);
end;
end; {putting source file data into memory}
except
on E: EInOutError do
begin
MessageDlg('Error reading ' + uppercase(SRCFileName) + '.'#13 +
GetError(E.ErrorCode)+'.', mterror,[mbOK], 0);
readFlag := -1;
end
end; {trying to open source file}
{if there hasn't been an error reading the source file then return the
total number of blockreads that have been performed. If there has been
an error then return -1...}
Result := readFlag;
end;
function TParseForm.ReadUntilSuccSeq: LongInt;
var
endMatch: Boolean;
i, filePos: LongInt;
tempArray: array[0..pattArrayLen] of Char;
bytesRead, bytesWritten: Integer;
begin
repeat
endMatch := True;
while (endMatch = True) do
begin
blockRead(srcFile, tempArray, succPattLen, bytesRead);
Inc(filePos);
i := 1;
repeat
if not(succSequence[i] = tempArray[i - 1]) then
begin
endMatch := False;
break;
end;
Inc(i);
until (i = succPattLen);
if (i = succPattLen) then
begin
endMatch := True;
break;
end
else Seek(srcFile, filePos);
end;
until ((filePos >= fileBytes) or (endMatch = True));
Result := filePos;
end;