Delphi truncate file

Initial tests threw up further obstacles, such as "end-of-file during read", the very first read. ERR instead, to cover the case when a byte beyond end-of-file is requested, clearly an error.

After these experiences, one suspects that each system will have its own quirks for some types of file, and testing will be required. One's guilt is not so easily diverted, but, Go has the required function in the standard library. The implementation calls operating system specific functions and returns whatever errors the operating system reports. This can be achieved by using the setFileSize function in System.

Files :. Unicon provides the built-in function truncate which can be used to truncate a file. The following line of code truncates filename to newsizeinbytes. The file is opened for both read and write in untranslated mode. The built-in function for truncating a file in Java will leave the file unchanged if the specified size is larger than the file.

This version expects the source file name and the new size as command line arguments in that order. It is also possible to call API functions to achieve this task. With native means Fileio Xtra file truncation can only be implemented indirectly, either using a temp file or loading truncated file contents into memory, deleting original and writing memory back to file:.

But there are also free plugins "Xtras" like e. Lua treats strings as being invariably one byte per character hence the awkwardness of trying to use it with unicode , so it's safe to use string methods to truncate binary data. Nim provides the module "posix" which allows to use the Posix functions in Nim programs. The behavior is that of the "truncate" Posix function.

Especially, if the provided length is greater than the current file size, the file is expanded at the requested length with null bytes. The function returns a code which can be checked to emit a message or raise an exception in case of error. In the following example, we ignore discard this return code. The Unix module provided with the standard distribution provides a function truncate :.

There is also a function ftruncate that does the equivalent operation but with a file descriptor instead of a file name:. In honour of this very task, there is now 0. PureBasic has the internal function TruncateFile that cuts the file at the current file position and discards all data that follows. Racket has a file-truncate function that expects an open port and truncate its associated file. Note that it can also extend the file, and the code below prints a warning in that case.

The external truncate routine could be replaced with the following line in which case no need for NativeCall :. As long as the REXX program has access to enough virtual memory, this version won't have an issue, except for some versions of REXX that are severely limited in virtual storage by design or by the operating system.

Extra boilerplate code was added to ensure that various flavors of REXX correctly handle a file that:. AA being truncated to bytes:. Consider this as undefined behaviour. Show 4 more comments. Active Oldest Votes. Improve this answer. Add a comment. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.

The Overflow Blog. Podcast Making Agile work for data science. Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Linked Related Hot Network Questions. Question feed. WriteString 'Section 1', 'Item 2', 'B' ; ini.

WriteString 'Section 2', 'Item 3', 'C' ; ini. WriteString 'Section 2', 'Item 4', 'D' ; finally ini. Free; end; memLog. EraseSection 'Section 1' ; finally ini. This is one of the reasons I don't use ini files anymore. Quote: This is one of the reasons I don't use ini files anymore. What about for transport and processing of serious amounts of data?

This in terms of both discovering the blocks and decoding the data to be useful. Any experience there? For what I'm finding in my initial studies XML viewers and the like , XML seems so slow just to initially process that "very slow" doesn't even begin to describe it.

Or am I just finding outliers? Okay, sorry for taking so long to respond- work was hectic these past few weeks: I manage to get the EraseSection working None the less- my main loading function to populate the still fails me. When it hits a blank entry it's supposed to exit the loop, but if my file has the following layout, it creates blank lines in the listbox.

I figure that if I could at least fix my main function to ignore the blank entries then it shouldn't be a problem. Add 'Item List Empty! Add 'item List Not Found! For this test which shows that EraseSection works as expected, I am using Delphi 7 including service pack 3.

Create IniFileName ; try i. WriteString '0', 'variable', 'text0' ; i. WriteString '1', 'variable', 'text2' ; i. WriteString '2', 'variable', 'text3' ; i. WriteString '3', 'variable', 'text4' ; i. WriteString '4', 'variable', 'text5' ; finally i. Free; end; end; procedure TForm1. EraseSection '3' ; i. EraseSection '7' ; finally i. Free; end; end;. Red Flag This Post Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.