Add detect encoding with BOM: UTF-7 and GB-18030

[rstm-sf]

Resolve #79

Add detect

• UTF-7 BOM
• GB-18030 BOM

[rstm-sf]

Simplification of checks in FindCharSetByBom
because len <= buf.Length always

So in the end it is called from the following places

UTF-unknown/src/CharsetDetector.cs

Line 142 in cb3dca2

detector.Feed(bytes, 0, bytes.Length);

UTF-unknown/src/CharsetDetector.cs

Lines 199 to 201 in cb3dca2

	while ((read = stream.Read(buff, 0, toRead)) > 0)
	{
	detector.Feed(buff, 0, read);

via

UTF-unknown/src/CharsetDetector.cs

Line 269 in cb3dca2

protected virtual void Feed(byte[] buf, int offset, int len)

UTF-unknown/src/CharsetDetector.cs

Line 283 in cb3dca2

_done = IsStartsWithBom(buf, len);

UTF-unknown/src/CharsetDetector.cs

Lines 297 to 299 in cb3dca2

	private bool IsStartsWithBom(byte[] buf, int len)
	{
	var bomSet = FindCharSetByBom(buf, len);

[rstm-sf]

It's bug or feature?

[rstm-sf]

At least add verification will be more efficient

[rstm-sf]

It seemed like it would be better, because otherwise, you need to add a length check every time

[304NotModified]

Great work! Thanks!

[304NotModified]

👍 👍

[304NotModified]

Thanks for the refactor also :)