Got the basic shell IO to work

autoload/vebugger.vim

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+function! s:readNewLinesFromPipe(pipeObject)
+	"read
+	let l:text=a:pipeObject.pipe.read(1000,0)
+	while 0<len(l:text)
+		let a:pipeObject.buffer.=l:text
+		let l:text=a:pipeObject.pipe.read(1000,0)
+	endwhile
+
+	"parse
+	let l:lastNewline=strridx(a:pipeObject.buffer,"\n")
+	if 0<=l:lastNewline
+		let l:outLines=split(strpart(a:pipeObject.buffer,0,l:lastNewline),'\n\|\r\|\r\n')
+		let a:pipeObject.buffer=strpart(a:pipeObject.buffer,l:lastNewline+1)
+		return l:outLines
+	endif
+
+	"return
+	return []
+endfunction
+
+function! s:createDebugger(command)
+	let l:debugger={'shell':vimproc#popen3(a:command)}
+	let l:debugger.outBuffer=''
+	let l:debugger.errBuffer=''
+
+	let l:debugger.pipes={
+				\'out':{'pipe':(l:debugger.shell.stdout),'buffer':''},
+				\'err':{'pipe':(l:debugger.shell.stderr),'buffer':''}}
+
+	function l:debugger.kill() dict
+		call self.shell.kill(15)
+	endfunction
+
+	function l:debugger.writeLine(line) dict
+		call self.shell.stdin.write(a:line."\n")
+	endfunction
+
+
+	function l:debugger.invokeReading() dict
+		let l:newLines={}
+		for l:k in keys(self.pipes)
+			let l:nl=s:readNewLinesFromPipe(self.pipes[l:k])
+			if 0<len(l:nl)
+				let l:newLines[l:k]=l:nl
+			endif
+		endfor
+		for l:k in keys(l:newLines)
+			for l:line in l:newLines[l:k]
+				call vebugger#handleLine(l:k,l:line)
+			endfor
+		endfor
+	endfunction
+
+	return l:debugger
+endfunction
+
+" all the functions here are currently just for testing:
+
+function! vebugger#startDebugger(command)
+	call vebugger#killDebugger()
+
+	let s:debugger=s:createDebugger(a:command)
+
+	augroup vebuffer_shell
+		autocmd!
+		autocmd CursorHold * call s:debugger.invokeReading()
+	augroup END
+endfunction
+
+function! vebugger#killDebugger()
+	if exists('s:debugger')
+		call s:debugger.shell.kill()
+		unlet s:debugger
+	endif
+endfunction
+
+function! vebugger#writeLine(line)
+	if exists('s:debugger')
+		call s:debugger.writeLine(a:line)
+	endif
+endfunction
+
+function! vebugger#invokeReading()
+	if exists('s:debugger')
+		call s:debugger.invokeReading()
+	endif
+endfunction
+
+function! vebugger#handleLine(pipe,line)
+	echo a:pipe.' - '.a:line
+endfunction

plugin/vebugger.vim

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+
+
+command! -nargs=1 VBGwrite call vebugger#writeLine(<q-args>)