pkg/dockerscript: expose a simple, clean API with a single Parse method

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)

beam/examples/beamsh/beamsh.go

@@ -3,109 +3,17 @@ package main
 import (
 	"fmt"
 	"os"
-	scanner "github.com/dotcloud/docker/pkg/dockerscript"
+	"github.com/dotcloud/docker/pkg/dockerscript"
-	"strings"
 )
 
 func main() {
-	s := &scanner.Scanner{}
+	script, err := dockerscript.Parse(os.Stdin)
-	s.Init(os.Stdin)
-	s.Whitespace = 1<<'\t' | 1<<' '
-	//s.Mode = ScanIdents | ScanFloats | ScanChars | ScanStrings | ScanRawStrings | ScanComments | SkipComments
-	s.Mode = scanner.ScanStrings | scanner.ScanRawStrings | scanner.ScanIdents
-	expr, err := parse(s, "")
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "line %d:%d: %v\n", s.Pos().Line, s.Pos().Column, err)
+		fmt.Fprintf(os.Stderr, "parse error: %v\n", err)
 		os.Exit(1)
 	}
-	fmt.Printf("%d commands:\n", len(expr))
+	fmt.Printf("%d commands:\n", len(script))
-	for i, cmd := range expr {
+	for i, cmd := range script {
 		fmt.Printf("%%%d: %s\n", i, cmd)
 	}
 }
-
-type Command struct {
-	Args []string
-	Children []*Command
-}
-
-func (cmd *Command) subString(depth int) string {
-	var prefix string
-	for i:=0; i<depth; i++ {
-		prefix += "  "
-	}
-	s := prefix + strings.Join(cmd.Args, ", ")
-	if len(cmd.Children) > 0 {
-		s += " {\n"
-		for _, subcmd := range cmd.Children {
-			s += subcmd.subString(depth + 1)
-		}
-		s += prefix + "}"
-	}
-	s += "\n"
-	return s
-}
-
-func (cmd *Command) String() string {
-	return cmd.subString(0)
-}
-
-func parseArgs(s *scanner.Scanner) ([]string, rune, error) {
-	var parseError error
-	// FIXME: we overwrite previously set error
-	s.Error = func(s *scanner.Scanner, msg string) {
-		parseError = fmt.Errorf(msg)
-		// parseError = fmt.Errorf("line %d:%d: %s\n", s.Pos().Line, s.Pos().Column, msg)
-	}
-	var args []string
-	tok := s.Scan()
-	for tok != scanner.EOF {
-		if parseError != nil {
-			return args, tok, parseError
-		}
-		text := s.TokenText()
-		//fmt.Printf("--> [%s]\n", text)
-		if text == "{" || text == "}" || text == "\n" || text == "\r" || text == ";" {
-			return args, tok, nil
-		}
-		args = append(args, text)
-		tok = s.Scan()
-	}
-	return args, tok, nil
-}
-
-func parse(s *scanner.Scanner, opener string) (expr []*Command, err error) {
-	defer func() {
-		fmt.Printf("parse() returned %d commands:\n", len(expr))
-		for _, c := range expr {
-			fmt.Printf("\t----> %s\n", c)
-		}
-	}()
-	for {
-		args, tok, err := parseArgs(s)
-		if err != nil {
-			return nil, err
-		}
-		cmd := &Command{Args: args}
-		fmt.Printf("---> args=%v finished by %s\n", args, s.TokenText())
-		afterArgs := s.TokenText()
-		if afterArgs == "{" {
-			fmt.Printf("---> therefore calling parse() of sub-expression\n")
-			children, err := parse(s, "{")
-			fmt.Printf("---> parse() of sub-epxression returned %d commands (ended by %s) and error=%v\n", children, s.TokenText(), err)
-			if err != nil {
-				return nil, err
-			}
-			cmd.Children = children
-		} else if afterArgs == "}" && opener != "{" {
-			return nil, fmt.Errorf("unexpected end of block '}'")
-		}
-		if len(cmd.Args) > 0 || len(cmd.Children) > 0 {
-			expr = append(expr, cmd)
-		}
-		if tok == scanner.EOF || afterArgs == "}" {
-			break
-		}
-	}
-	return expr, nil
-}

dockerscript/dockerscript.go

@@ -0,0 +1,107 @@
+package dockerscript
+
+import (
+	"github.com/dotcloud/docker/pkg/dockerscript/scanner"
+	"fmt"
+	"io"
+	"strings"
+)
+
+type Command struct {
+	Args []string
+	Children []*Command
+}
+
+func Parse(src io.Reader) ([]*Command, error) {
+	s := &scanner.Scanner{}
+	s.Init(src)
+	s.Whitespace = 1<<'\t' | 1<<' '
+	//s.Mode = ScanIdents | ScanFloats | ScanChars | ScanStrings | ScanRawStrings | ScanComments | SkipComments
+	s.Mode = scanner.ScanStrings | scanner.ScanRawStrings | scanner.ScanIdents
+	expr, err := parse(s, "")
+	if err != nil {
+		return nil, fmt.Errorf("line %d:%d: %v\n", s.Pos().Line, s.Pos().Column, err)
+	}
+	return expr, nil
+}
+
+func (cmd *Command) subString(depth int) string {
+	var prefix string
+	for i:=0; i<depth; i++ {
+		prefix += "  "
+	}
+	s := prefix + strings.Join(cmd.Args, ", ")
+	if len(cmd.Children) > 0 {
+		s += " {\n"
+		for _, subcmd := range cmd.Children {
+			s += subcmd.subString(depth + 1)
+		}
+		s += prefix + "}"
+	}
+	s += "\n"
+	return s
+}
+
+func (cmd *Command) String() string {
+	return cmd.subString(0)
+}
+
+func parseArgs(s *scanner.Scanner) ([]string, rune, error) {
+	var parseError error
+	// FIXME: we overwrite previously set error
+	s.Error = func(s *scanner.Scanner, msg string) {
+		parseError = fmt.Errorf(msg)
+		// parseError = fmt.Errorf("line %d:%d: %s\n", s.Pos().Line, s.Pos().Column, msg)
+	}
+	var args []string
+	tok := s.Scan()
+	for tok != scanner.EOF {
+		if parseError != nil {
+			return args, tok, parseError
+		}
+		text := s.TokenText()
+		//fmt.Printf("--> [%s]\n", text)
+		if text == "{" || text == "}" || text == "\n" || text == "\r" || text == ";" {
+			return args, tok, nil
+		}
+		args = append(args, text)
+		tok = s.Scan()
+	}
+	return args, tok, nil
+}
+
+func parse(s *scanner.Scanner, opener string) (expr []*Command, err error) {
+	defer func() {
+		fmt.Printf("parse() returned %d commands:\n", len(expr))
+		for _, c := range expr {
+			fmt.Printf("\t----> %s\n", c)
+		}
+	}()
+	for {
+		args, tok, err := parseArgs(s)
+		if err != nil {
+			return nil, err
+		}
+		cmd := &Command{Args: args}
+		fmt.Printf("---> args=%v finished by %s\n", args, s.TokenText())
+		afterArgs := s.TokenText()
+		if afterArgs == "{" {
+			fmt.Printf("---> therefore calling parse() of sub-expression\n")
+			children, err := parse(s, "{")
+			fmt.Printf("---> parse() of sub-epxression returned %d commands (ended by %s) and error=%v\n", children, s.TokenText(), err)
+			if err != nil {
+				return nil, err
+			}
+			cmd.Children = children
+		} else if afterArgs == "}" && opener != "{" {
+			return nil, fmt.Errorf("unexpected end of block '}'")
+		}
+		if len(cmd.Args) > 0 || len(cmd.Children) > 0 {
+			expr = append(expr, cmd)
+		}
+		if tok == scanner.EOF || afterArgs == "}" {
+			break
+		}
+	}
+	return expr, nil
+}