io.stream_reader read function does not work about v HOT 5 OPEN

@Casper64 I am not sure if you can investigate or not.

from v.

The read method should only be used if a io.reader instance is passed when creating a new StringReader.

That's confusing, it should be possible to use the read method seperately. 👍

from v.

Sorry, to come back at this:

In your example you pass in a buffer of lenght 100. If you call read the stringreader will attempt to read 100 bytes. The given source is only 4 bytes long, so then the code tries to read from the io.reader contained in it, but that is not set, there is no data and the method returns an error.

To me this makes sense, but the error message doesn't.

I think in this case the method should return the io.Eof error. What do you think @thomas-mangin ?

from v.

Hi @Casper64, and thank you for answering.

You are right: I messed up my minimum viable example; my buffer length should have been smaller than the string length.

In the case above, if only 14 bytes were read, the function should return 14 and the next call should return Eof. I believe this is the expected behaviour of the function in the C language and what people would expect.

As the above buffer is 100, then either another system call to the OS is required to read more than 14 bytes (for networking, the data may still be in transit) or only 14 bytes are available. The next call would then return Eof.

The problem with the reader not getting set is still there with a small buffer size as you can see below where the buffer length is 4.

module main

import io.string_reader

fn main() {
	s := 'line 1\nline 2\n'

	// works
	mut r := string_reader.StringReader.new(source: s)
	assert r.read_all(false)! == s

	// fails
	mut b := []u8{len: 4}
	mut sr := string_reader.StringReader.new(source: s)
	sr.read(mut b)!
}

❯ v run bug.v  
V panic: result not set (reader is not set)
v hash: df7828d
0   bug                                 0x0000000104a76838 panic_result_not_set + 124
1   bug                                 0x0000000104a8d650 main__main + 1000
2   bug                                 0x0000000104a8d95c main + 84
3   dyld                                0x000000018ebe60e0 start + 2360

from v.

That will be fixed. When the length of the buffer is smaller or equal to the length of the provided source the string reader will read from that source always, regardless of whether a reader is set or not.

from v.