Offset must be >= 0 && <= 0 Out of range 0 :-)

[amno1]

• Version: v10.4.0
• Platform: Linux pascal 4.17.0-1-ARCH deps: update openssl to 1.0.1j #1 Mon Jun 4 20:39:17 UTC 2018 x86_64 GNU/Linux

internal/fs/utils.js:353
throw err;
^

RangeError [ERR_OUT_OF_RANGE]: The value of "offset" is out of range. It must be >= 0 && <= 0. Received 0
at Object.fs.readSync (fs.js:626:3)
at Object. (/home/arthur/serialkeys/dbtest/getkeys.js:11:14)
at Module._compile (internal/modules/cjs/loader.js:702:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:713:10)
at Module.load (internal/modules/cjs/loader.js:612:32)
at tryModuleLoad (internal/modules/cjs/loader.js:551:12)
at Function.Module._load (internal/modules/cjs/loader.js:543:3)
at Function.Module.runMain (internal/modules/cjs/loader.js:744:10)
at startup (internal/bootstrap/node.js:238:19)
at bootstrapNodeJSCore (internal/bootstrap/node.js:572:3)

I am trying to read a file and I am getting error when trying to read at beginning. As seen above, it says offset must be >= 0 and <= 0. It is very interesting error message i must say. Anyway I am using offset 0 and I get that error :-). I am just trying to read 10 bytes into an Uint8Array. Here is the call

let string = new Uint8Array();
let num = fs.readSync(keyfile, string, 0, 10, 0)

[joyeecheung]

There should be an error for this because the buffer is empty and can't be written, although the error message does look pretty funny and this error (bufferLength === 0) should be special cased.

If anyone is interested, the enhancement should be added in

node/lib/internal/fs/utils.js

Lines 293 to 307 in 6dbd6f6

	function validateOffsetLengthRead(offset, length, bufferLength) {
	let err;
	if (offset < 0 || offset >= bufferLength) {
	err = new ERR_OUT_OF_RANGE('offset', `>= 0 && <= ${bufferLength}`, offset);
	} else if (length < 0 || offset + length > bufferLength) {
	err = new ERR_OUT_OF_RANGE('length',
	`>= 0 && <= ${bufferLength - offset}`, length);
	}
	if (err !== undefined) {
	Error.captureStackTrace(err, validateOffsetLengthRead);
	throw err;
	}
	}

(Not sure if this count as a good first issue so I'll just add help wanted for new contributors)

[amno1]

Aha, so it was referring to my uint8array :-). Indeed changing constructor to make 10 bytes solved it.

let string = new Uint8Array(10);

However the message text is still funny, maybe renaming offset to "target_offset" or something might make it a bit easier for n00bs like me? :-)

[amno1]

Thank you by the way!

[joyeecheung]

@amno1 I think the better error should probably just be ERR_BUFFER_OUT_OF_BOUNDS or ERR_INVALID_BUFFER_SIZE with a twist to the message formatters since none of them look suitable right now. Or a generic ERR_INVALID_ARG_VALUE also works.

I could fix this myself if no new contributor want to pick this up. The internal error system is documented here: https://github.com/nodejs/node/blob/master/doc/guides/using-internal-errors.md

[amno1]

Just put a bit more clear message in error message and probably in documentation as well, what "offset" means. I was looking at docs, since I am really a C/C++ programmer, and wasn't really clear why there was both position and offset. The error message didn't help much :-). This is what docs says:

fs.readSync(fd, buffer, offset, length, position)

History

fd <integer>
buffer <Buffer> | <Uint8Array>
offset <integer>
length <integer>
position <integer>
Returns: <number>

Synchronous version of fs.read(). Returns the number of bytesRead.

Just make it a bit more clear in which ever way you prefer.

[joyeecheung]

@amno1

The convention of the fs docs is: the actual explanation in under the async version of that API. In this case, fs.read() has a detailed explanation of what these arguments mean, and the sync version only mentions Synchronous version of fs.read().

Probably deserves another good first issue to make it more explicit, something like For detailed documentation, see fs.api().

[ryzokuken]

As mentioned by @joyeecheung, this is just a matter of improving the current error messages in

node/lib/internal/fs/utils.js

Lines 293 to 307 in 6dbd6f6

	function validateOffsetLengthRead(offset, length, bufferLength) {
	let err;
	if (offset < 0 || offset >= bufferLength) {
	err = new ERR_OUT_OF_RANGE('offset', `>= 0 && <= ${bufferLength}`, offset);
	} else if (length < 0 || offset + length > bufferLength) {
	err = new ERR_OUT_OF_RANGE('length',
	`>= 0 && <= ${bufferLength - offset}`, length);
	}
	if (err !== undefined) {
	Error.captureStackTrace(err, validateOffsetLengthRead);
	throw err;
	}
	}

replacing the current one with a ERR_INVALID_ARG_VALUE or a modified version of ERR_INVALID_BUFFER_SIZE maybe. PRs welcome, labelling as good-first-issue.

[AdityaSrivast]

I want to give this a try. Will report back in two days.

[ryzokuken]

@AdityaSrivast sure thing! Feel free to reach out if you face any issues setting everything up.

[AdityaSrivast]

@ryzokuken Is there any way to test this error and know that I have fixed it?