func gettok()

in cmd/goyacc/yacc.go [828:998]
152 lines of code
58 McCabe index (conditional complexity)

func gettok() int {
	var i int
	var match, c rune

	tokname = ""
	for {
		lineno += peekline
		peekline = 0
		c = getrune(finput)
		for c == ' ' || c == '\n' || c == '\t' || c == '\v' || c == '\r' {
			if c == '\n' {
				lineno++
			}
			c = getrune(finput)
		}

		// skip comment -- fix
		if c != '/' {
			break
		}
		lineno += skipcom()
	}

	switch c {
	case EOF:
		if tokflag {
			fmt.Printf(">>> ENDFILE %v\n", lineno)
		}
		return ENDFILE

	case '{':
		ungetrune(finput, c)
		if tokflag {
			fmt.Printf(">>> ={ %v\n", lineno)
		}
		return '='

	case '<':
		// get, and look up, a type name (union member name)
		c = getrune(finput)
		for c != '>' && c != EOF && c != '\n' {
			tokname += string(c)
			c = getrune(finput)
		}

		if c != '>' {
			errorf("unterminated < ... > clause")
		}

		for i = 1; i <= ntypes; i++ {
			if typeset[i] == tokname {
				numbval = i
				if tokflag {
					fmt.Printf(">>> TYPENAME old <%v> %v\n", tokname, lineno)
				}
				return TYPENAME
			}
		}
		ntypes++
		numbval = ntypes
		typeset[numbval] = tokname
		if tokflag {
			fmt.Printf(">>> TYPENAME new <%v> %v\n", tokname, lineno)
		}
		return TYPENAME

	case '"', '\'':
		match = c
		tokname = string(c)
		for {
			c = getrune(finput)
			if c == '\n' || c == EOF {
				errorf("illegal or missing ' or \"")
			}
			if c == '\\' {
				tokname += string('\\')
				c = getrune(finput)
			} else if c == match {
				if tokflag {
					fmt.Printf(">>> IDENTIFIER \"%v\" %v\n", tokname, lineno)
				}
				tokname += string(c)
				return IDENTIFIER
			}
			tokname += string(c)
		}

	case '%':
		c = getrune(finput)
		switch c {
		case '%':
			if tokflag {
				fmt.Printf(">>> MARK %%%% %v\n", lineno)
			}
			return MARK
		case '=':
			if tokflag {
				fmt.Printf(">>> PREC %%= %v\n", lineno)
			}
			return PREC
		case '{':
			if tokflag {
				fmt.Printf(">>> LCURLY %%{ %v\n", lineno)
			}
			return LCURLY
		}

		getword(c)
		// find a reserved word
		for i := range resrv {
			if tokname == resrv[i].name {
				if tokflag {
					fmt.Printf(">>> %%%v %v %v\n", tokname,
						resrv[i].value-PRIVATE, lineno)
				}
				return resrv[i].value
			}
		}
		errorf("invalid escape, or illegal reserved word: %v", tokname)

	case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
		numbval = int(c - '0')
		for {
			c = getrune(finput)
			if !isdigit(c) {
				break
			}
			numbval = numbval*10 + int(c-'0')
		}
		ungetrune(finput, c)
		if tokflag {
			fmt.Printf(">>> NUMBER %v %v\n", numbval, lineno)
		}
		return NUMBER

	default:
		if isword(c) || c == '.' || c == '$' {
			getword(c)
			break
		}
		if tokflag {
			fmt.Printf(">>> OPERATOR %v %v\n", string(c), lineno)
		}
		return int(c)
	}

	// look ahead to distinguish IDENTIFIER from IDENTCOLON
	c = getrune(finput)
	for c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\r' || c == '/' {
		if c == '\n' {
			peekline++
		}
		// look for comments
		if c == '/' {
			peekline += skipcom()
		}
		c = getrune(finput)
	}
	if c == ':' {
		if tokflag {
			fmt.Printf(">>> IDENTCOLON %v: %v\n", tokname, lineno)
		}
		return IDENTCOLON
	}

	ungetrune(finput, c)
	if tokflag {
		fmt.Printf(">>> IDENTIFIER %v %v\n", tokname, lineno)
	}
	return IDENTIFIER
}