Add SourceFile struct

This struct contains the path of a source file, together with the
library or sketch it is contained in. This allows the SourceFile methods
to generate the full paths to the source file, object file and
dependency file, making it easier to pass around source files.

This commit only adds the struct. Next commits will start to use this
struct in the include detection, where it fills an immediate need, later
it will be used in more places as well.

Signed-off-by: Matthijs Kooijman <matthijs@stdin.nl>

Author: matthijskooijman

src/arduino.cc/builder/types/types.go

@@ -31,13 +31,75 @@ package types
 
 import (
 	"os"
+	"fmt"
 	"path/filepath"
 	"strconv"
 
 	"arduino.cc/builder/constants"
 	"arduino.cc/properties"
 )
 
+type SourceFile struct {
+	// Sketch or Library pointer that this source file lives in
+        Origin interface{}
+	// Path to the source file within the sketch/library root folder
+        RelativePath string
+}
+
+// Create a SourceFile containing the given source file path within the
+// given origin. The given path can be absolute, or relative within the
+// origin's root source folder
+func MakeSourceFile(ctx *Context, origin interface{}, path string) (SourceFile, error) {
+	if filepath.IsAbs(path) {
+		var err error
+		path, err = filepath.Rel(sourceRoot(ctx, origin), path)
+		if err != nil {
+			return SourceFile{}, err
+		}
+	}
+	return SourceFile{Origin: origin, RelativePath: path}, nil
+}
+
+// Return the build root for the given origin, where build products will
+// be placed. Any directories inside SourceFile.RelativePath will be
+// appended here.
+func buildRoot(ctx *Context, origin interface{}) string {
+        switch o := origin.(type) {
+                case *Sketch:
+                        return ctx.SketchBuildPath
+                case *Library:
+			return filepath.Join(ctx.LibrariesBuildPath, o.Name)
+                default:
+                        panic("Unexpected origin for SourceFile: " + fmt.Sprint(origin))
+        }
+}
+
+// Return the source root for the given origin, where its source files
+// can be found. Prepending this to SourceFile.RelativePath will give
+// the full path to that source file.
+func sourceRoot(ctx *Context, origin interface{}) string {
+        switch o := origin.(type) {
+                case *Sketch:
+                        return ctx.SketchBuildPath
+                case *Library:
+			return o.SrcFolder
+                default:
+                        panic("Unexpected origin for SourceFile: " + fmt.Sprint(origin))
+        }
+}
+
+func (f *SourceFile) SourcePath(ctx *Context) string {
+        return filepath.Join(sourceRoot(ctx, f.Origin), f.RelativePath)
+}
+
+func (f *SourceFile) ObjectPath(ctx *Context) string {
+        return filepath.Join(buildRoot(ctx, f.Origin), f.RelativePath + ".o")
+}
+
+func (f *SourceFile) DepfilePath(ctx *Context) string {
+        return filepath.Join(buildRoot(ctx, f.Origin), f.RelativePath + ".d")
+}
+
 type SketchFile struct {
 	Name   string
 	Source string