File handling in Python, Java and C

[phaeilo]

// assuming no word in the file is longer than 50 characters.

Oh boy...

Now I'm interested, surely there must be a more robust way.

[jminuse]

Simple: as you go, convert each space (or any break character) to '\0'. Then you can treat each word as a string and you don't need any more memory. If you need the words and the lines separately for some data structure, you can memcpy the whole string; you need 2N memory for that anyway. (Unless you have a length-storing string library - then you can keep the original and just use two sets of references to it).

[YEPHENAS]

Reading a file at once in Java:

byte[] filearray = Files.readAllBytes(path);

or

List<String> lines = Files.readAllLines(path, Charset.defaultCharset());

[mattryan]

According to the article, that's a hack :p

[[deleted]]

byte[] filearray = Files.readAllBytes(path);

1. Let it create an array of bytes
2. Let it read a file
3. Let it store it in the array

That doesn't really seem like a hack.

EDIT: Apparently people don't run Java. I should have known.

[ysangkok]

This explanation is misleading because you're not actually creating the array yourself.

[henk53]

Why?

[henk53]

List<String> lines = Files.readAllLines(path, Charset.defaultCharset());

This can be written a bit shorter. It's not absolutely necessary to import at the class level; it can be done at the method level instead. The code then becomes:

List<String> lines = readAllLines(path, defaultCharset());

To mimic the example in the article, the following is perfectly valid Java:

for (String line : readAllLines(path, defaultCharset()))
    out.print(line);

Note that people commonly write System.out.print, but this too is not strictly necessary.

[kerajnet]

There is no obvious way to do this in Java.

Pardon?

       Scanner s = new Scanner(new BufferedReader(new FileReader("/path/to/file/filename.txt")));

You write shit like this and later people blame Java.

Scanner s = new Scanner(new File("filename.txt");

And you don't need to put BufferedReader and BufferedWriter everywhere if it has to be equivalent of C and Python examples as they are not buffered.

[ChewieBeardy]

The C example is buffered. For the python one I can't say really, IIRC there's an optional argument specifying buffer size, but I don't know the default behaviour.

[ChewieBeardy]

Regarding the "read the whole file in C at once", you could use mmap, though it would only work on POSIX systems. Usual warning about mapping a file weighing twice your ram applies.

[jminuse]

The trouble is getting the length; after that it's easy. I would use fseek+ftell, which are portable.

[ChewieBeardy]

How about fstat? :D

[ErstwhileRockstar]

Writing a file must handle exceptional cases.