Merge lp:~miki-tebeka/gorun/gorun-md5 into lp:gorun

[tebeka]

Using md5 signature instead of time stamps. This simplifies the logic of "do we need to recompile" and also protects from clock skew.

[Gustavo Niemeyer (niemeyer)]

I believe we talked about that elsewhere at the time. Computing the md5 all the time on a file content is unnecessary.

Unmerged revisions

3. By tebeka on 2011-03-19

Using md5 instead of time

=== modified file 'gorun.go'
--- gorun.go	2011-03-12 05:24:47 +0000
+++ gorun.go	2011-03-19 18:24:31 +0000
@@ -22,6 +22,7 @@
 // with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import (
+	"crypto/md5"
 	"exec"
 	"fmt"
 	"io/ioutil"
@@ -29,7 +30,6 @@
 	"path/filepath"
 	"runtime"
 	"strconv"
-	"strings"
 	"time"
 )
 
@@ -64,7 +64,7 @@
 	// causes the file to be updated on the next run.
 	now := time.Nanoseconds()
 
-	sstat, err := os.Stat(sourcefile)
+	_, err = os.Stat(sourcefile)
 	if err != nil {
 		return err
 	}
@@ -75,8 +75,6 @@
 		compile = true
 	case !rstat.IsRegular():
 		return os.ErrorString("not a file: " + runfile)
-	case rstat.Mtime_ns < sstat.Mtime_ns || rstat.Permission() & 0700 != 0700:
-		compile = true
 	default:
 		// We have spare cycles. Maybe remove old files.
 		if err := os.Chtimes(runfile, now, now); err == nil {
@@ -90,8 +88,6 @@
 			if err != nil {
 				return err
 			}
-			// If sourcefile was changed, will be updated on next run.
-			os.Chtimes(runfile, sstat.Mtime_ns, sstat.Mtime_ns)
 		}
 
 		err = os.Exec(runfile, args, os.Environ())
@@ -164,6 +160,23 @@
 	return nil
 }
 
+func FileMD5(sourcefile string) (string, os.Error) {
+	content, err := ioutil.ReadFile(sourcefile)
+	if err != nil {
+		return "", err
+	}
+
+	digest := md5.New()
+	digest.Write(content)
+
+	s := ""
+	for _, b := range digest.Sum() {
+		s += fmt.Sprintf("%02x", b)
+	}
+
+	return s, nil
+}
+
 func GoRunFile(sourcefile string) (rundir, runfile string, err os.Error) {
 	rundir, err = GoRunDir()
 	if err != nil {
@@ -173,8 +186,10 @@
 	if err != nil {
 		return "", "", err
 	}
-	runfile = strings.Replace(sourcefile, "%", "%%", -1)
-	runfile = strings.Replace(runfile, string(filepath.Separator), "%", -1)
+	runfile, err = FileMD5(sourcefile)
+	if err != nil {
+		return "", "", err
+	}
 	runfile = filepath.Join(rundir, runfile)
 	return rundir, runfile, nil
 }