1353285 - Provide chrome JS helpers for reading UTF-8 as string and writing string as UTF-8 file

Status: NEW

(Toolkit :: General, enhancement)

Description

[Henri Sivonen (:hsivonen)]

To facilitate the removal of nsIConverterOutputStream, nsIConverterInputStream and nsIScriptableUnicodeConverter, we should have helper functions available to chrome JS that use TextDecoder and TextEncoder for conversion between JS strings (UTF-16) and bytes (UTF-8) in the context of XPCOM streams.

We should probably have these four functions:

1. Takes an nsIInputStream and reads it to the end synchronously, converts the data from UTF-8 to UTF-16 using TextDecoder and returns the result as a JS string. Marked as "don't use except for legacy code that hasn't been refactored to be async yet".

2. Takes an nsIInputStream and returns a promise. Reads the stream to the end asynchronously, converts the data from UTF-8 to UTF-16 and resolves the promise with the result as a JS string.

3. Takes a JS string and an nsIOutputStream, converts the string from UTF-16 to UTF-8 using TextEncoder and writes the bytes to the stream synchronously. Marked as "don't use except for legacy code that hasn't been refactored to be async yet".

4. Takes a JS string and an nsIOutputStream and returns a promise. Converts the string from UTF-16 to UTF-8 using TextEncoder, writes the bytes to the stream asynchronously and resolves the promise when done.

Comment 1

[Henri Sivonen (:hsivonen)]

(In reply to Henri Sivonen (:hsivonen) from comment #0)
> 1. Takes an nsIInputStream and reads it to the end synchronously, converts
> the data from UTF-8 to UTF-16 using TextDecoder and returns the result as a
> JS string. Marked as "don't use except for legacy code that hasn't been
> refactored to be async yet".

Wrap the stream in nsIBinaryInputStream, use readArrayBuffer().

> 2. Takes an nsIInputStream and returns a promise. Reads the stream to the
> end asynchronously, converts the data from UTF-8 to UTF-16 and resolves the
> promise with the result as a JS string.

Depends on bug 1347873, AFAICT.

> 3. Takes a JS string and an nsIOutputStream, converts the string from UTF-16
> to UTF-8 using TextEncoder and writes the bytes to the stream synchronously.
> Marked as "don't use except for legacy code that hasn't been refactored to
> be async yet".

Need to check if writeByteArray on nsIBinaryOutputStream enables this already.

> 4. Takes a JS string and an nsIOutputStream and returns a promise. Converts
> the string from UTF-16 to UTF-8 using TextEncoder, writes the bytes to the
> stream asynchronously and resolves the promise when done.

Wrap as nsIArrayBufferInputStream and use NetUtil::asyncCopy().

Comment 2

[Henri Sivonen (:hsivonen)]

Should these live in NetUtil.jsm?

Comment 3

[Andrew McCreight [:mccr8]]

(In reply to Henri Sivonen (:hsivonen) from comment #2)
> Should these live in NetUtil.jsm?

I really don't know anything about NetUtil.jsm, sorry.

Comment 4

[Henri Sivonen (:hsivonen)]

(In reply to Andrew McCreight [:mccr8] from comment #3)
> (In reply to Henri Sivonen (:hsivonen) from comment #2)
> > Should these live in NetUtil.jsm?
> 
> I really don't know anything about NetUtil.jsm, sorry.

OK, based on tweets, I thought you were doing NetUtil.jsm-related things.

bz, should these live in NetUtil.jsm?

Comment 5

[Boris Zbarsky [:bzbarsky]]

I was going to say I have no idea and have nothing to do with this file, then discovered I'm the original author...

So given that, sure, why not.  ;)