' Try/catch runtime demonstration
'
' This module implements the private signal and setjmp/longjmp state used by
' the companion try/catch macros.
'
' Ownership: Each Exception owns its string copies and replaces them only after
' a new copy has been allocated.
'
' This demonstration intentionally does not provide thread-safe exception
' delivery or an async-signal-safe allocation strategy.

#include once "trycatch.bi"

#define	SIGINT		2	'' Interactive attention
#define	SIGILL		4	'' Illegal instruction
#define	SIGFPE		8	'' Floating point error
#define	SIGSEGV		11	'' Segmentation violation
#define	SIGTERM		15	'' Termination request
#define SIGBREAK	21	'' Control-break
#define	SIGABRT		22	'' Abnormal termination (abort)

extern "C"
	type __p_sig_fn_t as sub(byval as integer)
	declare function signal(byval as integer, byval as __p_sig_fn_t) as __p_sig_fn_t
end extern

type TryCatchCtx
	cur 		as TryCatch ptr
	oldsigabrt  as __p_sig_fn_t
	oldsigsegv  as __p_sig_fn_t
	oldsigfpe	as __p_sig_fn_t
	oldsigill	as __p_sig_fn_t
	oldsigterm	as __p_sig_fn_t
	oldsigint	as __p_sig_fn_t
end type

' The signal handler and TryCatch constructors share one process-local context.
'' FB-LINTER: DISABLE-NEXT-LINE FBL301
	dim shared ctx as TryCatchCtx
	dim shared messages(0 to 31) as zstring * 32

private sub handler cdecl(byval sig as integer)
	if ctx.cur = 0 then
		error sig
	end if
	if sig < lbound(messages) orelse sig > ubound(messages) then
		error sig
	end if

	signal(sig, @handler)

	ctx.cur->ex = new Exception(messages(sig))
	if ctx.cur->ex = 0 then
		error 7
	end if

	var buf = @ctx.cur->buf

	ctx.cur = ctx.cur->prev

	crt.longjmp(buf, sig)
end sub

private sub __construc() constructor
	messages(SIGINT)	= "Interactive attention"
	messages(SIGILL) 	= "Illegal instruction"
	messages(SIGFPE) 	= "Floating point error"
	messages(SIGSEGV)	= "Segmentation violation"
	messages(SIGTERM)	= "Termination request"
	messages(SIGBREAK)	= "Control-break"
	messages(SIGABRT)	= "Abnormal termination"

	ctx.oldsigabrt = signal(SIGABRT, @handler)
	ctx.oldsigsegv = signal(SIGSEGV, @handler)
	ctx.oldsigfpe = signal(SIGFPE, @handler)
	ctx.oldsigill = signal(SIGILL, @handler)
	ctx.oldsigterm = signal(SIGTERM, @handler)
	ctx.oldsigint = signal(SIGINT, @handler)
end sub

private sub __destruc() destructor
	signal(SIGABRT, ctx.oldsigabrt)
	signal(SIGSEGV, ctx.oldsigsegv)
	signal(SIGFPE, ctx.oldsigfpe)
	signal(SIGILL, ctx.oldsigill)
	signal(SIGTERM, ctx.oldsigterm)
	signal(SIGINT, ctx.oldsigint)
end sub

''
'' TryCatch
''
constructor TryCatch()
	this.prev = ctx.cur
	ctx.cur = @this
end constructor

destructor TryCatch()
	if( ctx.cur = @this ) then
		ctx.cur = this.prev
	end if
	if this.ex <> 0 then
		delete this.ex
	end if
end destructor

sub TryCatch.throw_(file as zstring ptr, func as zstring ptr, line_ as integer)
	if ctx.cur = 0 then
		error 1
	end if
	if this.ex = 0 then
		error 7
	end if

	this.ex->file = file
	this.ex->func = func
	this.ex->line = line_
	var buf = @ctx.cur->buf
	ctx.cur = ctx.cur->prev
	crt.longjmp(buf, 1)
end sub

sub TryCatch.throw_(ex as Exception ptr, file as zstring ptr, func as zstring ptr, line_ as integer)
	if ex = 0 then
		error 5
	end if
	this.ex = ex
	throw_(file, func, line_)
end sub

sub TryCatch.throw_(msg as zstring ptr, file as zstring ptr, func as zstring ptr, line_ as integer)
	this.ex = new Exception(msg)
	if this.ex = 0 then
		error 7
	end if
	throw_(file, func, line_)
end sub

''
'' Exception
''
private sub CopyExceptionString(byref destination as zstring ptr, _
	byval source as zstring ptr)

	dim as zstring ptr replacement

	if source = 0 then
		replacement = allocate(1)
		if replacement = 0 then error 7
		*replacement = 0
	else
		replacement = allocate(len(*source) + 1)
		if replacement = 0 then error 7
		*replacement = *source
	end if

	if destination <> 0 then deallocate(destination)
	destination = replacement
end sub

constructor Exception()
	CopyExceptionString this.msg, @""
end constructor

constructor Exception(msg as zstring ptr)
	CopyExceptionString this.msg, msg
end constructor

destructor Exception()
	if this.msg <> 0 then
		deallocate(this.msg)
	end if
	if this.file_ <> 0 then
		deallocate(this.file_)
	end if
	if this.func_ <> 0 then
		deallocate(this.func_)
	end if
end destructor

property Exception.message() as string
	return *this.msg
end property

property Exception.file() as string
	return iif(this.file_ <> 0, *this.file_, "")
end property

property Exception.file(file_ as zstring ptr)
	CopyExceptionString this.file_, file_
end property

property Exception.func() as string
	return iif(this.func_ <> 0, *this.func_, "")
end property

property Exception.func(func_ as zstring ptr)
	CopyExceptionString this.func_, func_
end property

property Exception.line() as integer
	return this.line_
end property

property Exception.line(line_ as integer)
	this.line_ = line_
end property

operator Exception.cast() as string
	operator = this.toString()
end operator

function Exception.toString() as string
	function = this.message & " exception threw at " & this.file & "(" & this.line & "):" & this.func & "()"
end function

' End of trycatch.bas