From 992b7b94dd2981b4848ba17317c462e6d875e417 Mon Sep 17 00:00:00 2001
From: Sergey Matveev <stargrave@stargrave.org>
Date: Sun, 28 Aug 2022 17:07:28 +0300
Subject: [PATCH] Stat most files without opening them

---
 dep.go    |  2 +-
 depfix.go |  2 +-
 inode.go  | 38 +++++++++++++++++++++++++++-----------
 ood.go    | 13 ++++++-------
 run.go    | 18 ++++--------------
 5 files changed, 39 insertions(+), 34 deletions(-)

diff --git a/dep.go b/dep.go
index 0e4f24f..d819440 100644
--- a/dep.go
+++ b/dep.go
@@ -100,7 +100,7 @@ func depWrite(fdDep *os.File, cwd, tgt, hsh string) error {
 	if fi.IsDir() {
 		return nil
 	}
-	inode, err := inodeFromFile(fd)
+	inode, err := inodeFromFileByFd(fd)
 	if err != nil {
 		return err
 	}
diff --git a/depfix.go b/depfix.go
index 3cd45bb..a7174be 100644
--- a/depfix.go
+++ b/depfix.go
@@ -121,7 +121,7 @@ func depFix(root string) error {
 					}
 					return err
 				}
-				inode, err := inodeFromFile(fd)
+				inode, err := inodeFromFileByFd(fd)
 				if err != nil {
 					fd.Close()
 					return err
diff --git a/inode.go b/inode.go
index 82b6198..22aa142 100644
--- a/inode.go
+++ b/inode.go
@@ -84,8 +84,19 @@ func (inode *Inode) RecfileFields() []recfile.Field {
 	}
 }
 
-func inodeFromFile(fd *os.File) (*Inode, error) {
-	var fi os.FileInfo
+func inodeFromFileStat(fi os.FileInfo, stat unix.Stat_t) *Inode {
+	ctimeSec, ctimeNsec := stat.Ctim.Unix()
+	mtimeSec := fi.ModTime().Unix()
+	mtimeNsec := fi.ModTime().UnixNano()
+	return &Inode{
+		Size:     fi.Size(),
+		InodeNum: uint64(stat.Ino),
+		CtimeSec: ctimeSec, CtimeNsec: ctimeNsec,
+		MtimeSec: mtimeSec, MtimeNsec: mtimeNsec,
+	}
+}
+
+func inodeFromFileByFd(fd *os.File) (*Inode, error) {
 	fi, err := fd.Stat()
 	if err != nil {
 		return nil, err
@@ -95,15 +106,20 @@ func inodeFromFile(fd *os.File) (*Inode, error) {
 	if err != nil {
 		return nil, err
 	}
-	ctimeSec, ctimeNsec := stat.Ctim.Unix()
-	mtimeSec := fi.ModTime().Unix()
-	mtimeNsec := fi.ModTime().UnixNano()
-	return &Inode{
-		Size:     fi.Size(),
-		InodeNum: uint64(stat.Ino),
-		CtimeSec: ctimeSec, CtimeNsec: ctimeNsec,
-		MtimeSec: mtimeSec, MtimeNsec: mtimeNsec,
-	}, nil
+	return inodeFromFileStat(fi, stat), nil
+}
+
+func inodeFromFileByPath(p string) (*Inode, error) {
+	fi, err := os.Stat(p)
+	if err != nil {
+		return nil, err
+	}
+	var stat unix.Stat_t
+	err = unix.Stat(p, &stat)
+	if err != nil {
+		return nil, err
+	}
+	return inodeFromFileStat(fi, stat), nil
 }
 
 func inodeFromRec(m map[string]string) (*Inode, error) {
diff --git a/ood.go b/ood.go
index 40e6da8..7a31573 100644
--- a/ood.go
+++ b/ood.go
@@ -153,7 +153,7 @@ func isOOD(cwd, tgtOrig string, level int, seen map[string]struct{}) (bool, erro
 		theirHsh := m["Hash"]
 		tracef(CDebug, "ood: %s%s -> %s: checking", indent, tgtOrig, dep)
 
-		fd, err := os.Open(path.Join(cwd, dep))
+		inode, err := inodeFromFileByPath(path.Join(cwd, dep))
 		if err != nil {
 			if os.IsNotExist(err) {
 				tracef(CDebug, "ood: %s%s -> %s: not exists", indent, tgtOrig, dep)
@@ -162,12 +162,7 @@ func isOOD(cwd, tgtOrig string, level int, seen map[string]struct{}) (bool, erro
 			}
 			return ood, TgtError{tgtOrig, err}
 		}
-		defer fd.Close()
 
-		inode, err := inodeFromFile(fd)
-		if err != nil {
-			return ood, TgtError{tgtOrig, err}
-		}
 		if inode.Size != theirInode.Size {
 			tracef(CDebug, "ood: %s%s -> %s: size differs", indent, tgtOrig, dep)
 			ood = true
@@ -177,7 +172,12 @@ func isOOD(cwd, tgtOrig string, level int, seen map[string]struct{}) (bool, erro
 			tracef(CDebug, "ood: %s%s -> %s: same inode", indent, tgtOrig, dep)
 		} else {
 			tracef(CDebug, "ood: %s%s -> %s: inode differs", indent, tgtOrig, dep)
+			fd, err := os.Open(path.Join(cwd, dep))
+			if err != nil {
+				return ood, TgtError{tgtOrig, err}
+			}
 			hsh, err := fileHash(fd)
+			fd.Close()
 			if err != nil {
 				return ood, TgtError{tgtOrig, err}
 			}
@@ -188,7 +188,6 @@ func isOOD(cwd, tgtOrig string, level int, seen map[string]struct{}) (bool, erro
 			}
 			tracef(CDebug, "ood: %s%s -> %s: same hash", indent, tgtOrig, dep)
 		}
-		fd.Close()
 
 		if dep == tgt {
 			tracef(CDebug, "ood: %s%s -> %s: same target", indent, tgtOrig, dep)
diff --git a/run.go b/run.go
index 8cb6017..5e67c41 100644
--- a/run.go
+++ b/run.go
@@ -156,18 +156,13 @@ func isModified(cwd, redoDir, tgt string) (bool, *Inode, string, error) {
 		if m["Type"] != DepTypeIfchange || m["Target"] != tgt {
 			continue
 		}
-		fd, err := os.Open(path.Join(cwd, tgt))
+		ourInode, err = inodeFromFileByPath(path.Join(cwd, tgt))
 		if err != nil {
 			if os.IsNotExist(err) {
 				return false, nil, "", nil
 			}
 			return false, nil, "", err
 		}
-		ourInode, err = inodeFromFile(fd)
-		fd.Close()
-		if err != nil {
-			return false, nil, "", err
-		}
 		theirInode, err := inodeFromRec(m)
 		if err != nil {
 			return false, nil, "", err
@@ -655,15 +650,12 @@ func runScript(tgtOrig string, errs chan error, traced bool) error {
 		}
 
 		// Was $1 touched?
-		if fd, err := os.Open(path.Join(cwdOrig, tgt)); err == nil {
+		if inode, err := inodeFromFileByPath(path.Join(cwdOrig, tgt)); err == nil {
 			if inodePrev == nil {
-				fd.Close()
 				runErr.Err = Err1WasTouched
 				errs <- runErr
 				return
 			}
-			inode, err := inodeFromFile(fd)
-			fd.Close()
 			if err != nil {
 				runErr.Err = err
 				errs <- runErr
@@ -677,10 +669,8 @@ func runScript(tgtOrig string, errs chan error, traced bool) error {
 		}
 
 		if inodePrev != nil {
-			if fd, err := os.Open(path.Join(cwdOrig, tgt)); err == nil {
-				inode, err := inodeFromFile(fd)
-				fd.Close()
-				if err == nil && !inode.Equals(inodePrev) {
+			if inode, err := inodeFromFileByPath(path.Join(cwdOrig, tgt)); err == nil {
+				if !inode.Equals(inodePrev) {
 					runErr.Err = Err1WasTouched
 					errs <- runErr
 					return
-- 
2.44.0