Add caching

1 files changed, 114 insertions, 0 deletions

diff --git a/cache/cache.go b/cache/cache.go
index 32b8325..2d20087 100644
--- a/cache/cache.go
+++ b/cache/cache.go
@@ -1,13 +1,20 @@
 package cache
 
 import (
+	"bufio"
 	"code.laria.me/petrific/objects"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
 	"time"
 )
 
 type Cache interface {
 	PathUpdated(path string) (mtime time.Time, id objects.ObjectId, ok bool)
 	SetPathUpdated(path string, mtime time.Time, id objects.ObjectId)
+	Close() error
 }
 
 type NopCache struct{}
@@ -18,3 +25,110 @@ func (NopCache) PathUpdated(_ string) (_ time.Time, _ objects.ObjectId, ok bool)
 }
 
 func (NopCache) SetPathUpdated(_ string, _ time.Time, _ objects.ObjectId) {}
+
+func (NopCache) Close() error { return nil }
+
+type fileCacheEntry struct {
+	mtime time.Time
+	id    objects.ObjectId
+}
+
+type FileCache struct {
+	cache    map[string]fileCacheEntry
+	location string
+}
+
+func (fc FileCache) PathUpdated(path string) (time.Time, objects.ObjectId, bool) {
+	entry, ok := fc.cache[path]
+	return entry.mtime, entry.id, ok
+}
+
+func (fc FileCache) SetPathUpdated(path string, mtime time.Time, id objects.ObjectId) {
+	fc.cache[path] = fileCacheEntry{mtime, id}
+}
+
+func NewFileCache(location string) FileCache {
+	return FileCache{make(map[string]fileCacheEntry), location}
+}
+
+func escapeName(name string) string {
+	name = strings.Replace(name, "\\", "\\\\", -1)
+	name = strings.Replace(name, "\n", "\\n", -1)
+	return name
+}
+
+func unescapeName(name string) string {
+	name = strings.Replace(name, "\\n", "\n", -1)
+	name = strings.Replace(name, "\\\\", "\\", -1)
+	return name
+}
+
+func (fc FileCache) dump(w io.Writer) error {
+	for path, entry := range fc.cache {
+		if _, err := fmt.Fprintf(
+			w,
+			"%s %d %d %s\n",
+			entry.id,
+			entry.mtime.Unix(),
+			entry.mtime.Nanosecond(),
+			escapeName(path),
+		); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (fc FileCache) load(r io.Reader) error {
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		parts := strings.SplitN(scanner.Text(), " ", 4)
+		if len(parts) != 4 {
+			return fmt.Errorf("Could not load FileCache: Expected 4 entries, got %d", len(parts))
+		}
+
+		id, err := objects.ParseObjectId(parts[0])
+		if err != nil {
+			return err
+		}
+
+		sec, err := strconv.ParseInt(parts[1], 10, 64)
+		if err != nil {
+			return err
+		}
+
+		nsec, err := strconv.ParseInt(parts[2], 10, 64)
+		if err != nil {
+			return err
+		}
+
+		fc.cache[unescapeName(parts[3])] = fileCacheEntry{time.Unix(sec, nsec), id}
+	}
+
+	return scanner.Err()
+}
+
+func (fc FileCache) Load() error {
+	f, err := os.Open(fc.location)
+	switch {
+	case os.IsNotExist(err):
+		return nil
+	case err != nil:
+		return err
+	default:
+	}
+	defer f.Close()
+
+	return fc.load(f)
+}
+
+func (fc FileCache) Close() error {
+	f, err := os.Create(fc.location)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	return fc.dump(f)
+}