can't change encode with text files

[chenxuuu]

VS Code version: Code 1.37.1 (f06011a, 2019-08-15T16:17:55.855Z)
OS version: Windows_NT x64 10.0.18362

Steps to Reproduce:

1. make a new file, start with some 0x00 bytes, after those are really text
2. open it, vscode will mind you this file is bin file, you need to click and open it:
   
3. then you can't change this file's encoding:
   

I only changed two bytes

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-6650U CPU @ 2.20GHz (4 x 2208)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software oop_rasterization: disabled_off protected_video_decode: unavailable_off rasterization: enabled skia_deferred_display_list: disabled_off skia_renderer: disabled_off surface_synchronization: enabled_on video_decode: enabled viz_display_compositor: disabled_off webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	7.93GB (1.48GB free)
Process Argv
Screen Reader	no
VM	50%

Extensions (17)

Extension	Author (truncated)	Version
rainbow-brackets	2gu	0.0.6
blamer-vs	bea	0.5.0
love	bsc	0.3.6
vscode-markdownlint	Dav	0.30.1
xml	Dot	2.5.0
gitlens	eam	9.9.3
diff-tool	jin	0.0.1
svn-scm	joh	1.54.4
luacoderassist	liw	2.3.3
vscode-language-pack-zh-hans	MS-	1.37.5
python	ms-	2019.8.30787
cpptools	ms-	0.25.0
csharp	ms-	1.21.1
vsliveshare	ms-	1.0.721
indent-rainbow	ode	7.4.0
code-settings-sync	Sha	3.4.2
vscode-hexdump	sle	1.7.2

[vscodebot]

(Experimental duplicate detection)
Thanks for submitting this issue. Please also check if it is already covered by an existing one, like:

• file is bin, can't open as text (#79682)

[bpasero]

@chenxuuu what encoding is that that uses 0x00 bytes? We use that to detect binary files. If you need to use these bytes, set a UTF16 LE or BE BOM.

[chenxuuu]

@bpasero
problem is, in old version, I can change those files' encoding, but I can't do this in new version
my serial port logs may start with any data, include 0x00 or 0x40-0xff

[bpasero]

Great catch, I pushed a fix for that.