feat: implement enhanced garbage collection statistics logging

vfs/gc/gc.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"s1d3sw1ped/SteamCache2/vfs"
 	"s1d3sw1ped/SteamCache2/vfs/vfserror"
+	"sync"
 )
 
 // Ensure GCFS implements VFS.
@@ -12,12 +13,17 @@ var _ vfs.VFS = (*GCFS)(nil)
 // GCFS is a virtual file system that calls a GC handler when the disk is full. The GC handler is responsible for freeing up space on the disk. The GCFS is a wrapper around another VFS.
 type GCFS struct {
 	vfs.VFS
-	multiplier   int
-	gcHanderFunc GCHandlerFunc
+	multiplier int
+
+	// protected by mu
+	gcHanderFunc                 GCHandlerFunc
+	lifetimeBytes, lifetimeFiles uint
+	reclaimedBytes, deletedFiles uint
+	mu                           sync.Mutex
 }
 
 // GCHandlerFunc is a function that is called when the disk is full and the GCFS needs to free up space. It is passed the VFS and the size of the file that needs to be written. Its up to the implementation to free up space. How much space is freed is also up to the implementation.
-type GCHandlerFunc func(vfs vfs.VFS, size int)
+type GCHandlerFunc func(vfs vfs.VFS, size uint) (reclaimedBytes uint, deletedFiles uint)
 
 func New(vfs vfs.VFS, multiplier int, gcHandlerFunc GCHandlerFunc) *GCFS {
 	if multiplier <= 0 {
@@ -30,13 +36,39 @@ func New(vfs vfs.VFS, multiplier int, gcHandlerFunc GCHandlerFunc) *GCFS {
 	}
 }
 
+// Stats returns the lifetime bytes, lifetime files, reclaimed bytes and deleted files.
+// The lifetime bytes and lifetime files are the total bytes and files that have been freed up by the GC handler.
+// The reclaimed bytes and deleted files are the bytes and files that have been freed up by the GC handler since the last execution.
+// The reclaimed bytes and deleted files are reset to 0 after the call to Stats.
+func (g *GCFS) Stats() (lifetimeBytes, lifetimeFiles, reclaimedBytes, deletedFiles uint) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+
+	g.lifetimeBytes += g.reclaimedBytes
+	g.lifetimeFiles += g.deletedFiles
+
+	lifetimeBytes = g.lifetimeBytes
+	lifetimeFiles = g.lifetimeFiles
+	reclaimedBytes = g.reclaimedBytes
+	deletedFiles = g.deletedFiles
+
+	g.reclaimedBytes = 0
+	g.deletedFiles = 0
+
+	return
+}
+
 // Set overrides the Set method of the VFS interface. It tries to set the key and src, if it fails due to disk full error, it calls the GC handler and tries again. If it still fails it returns the error.
 func (g *GCFS) Set(key string, src []byte) error {
+	g.mu.Lock()
+	defer g.mu.Unlock()
 	err := g.VFS.Set(key, src) // try to set the key and src
 
 	if err == vfserror.ErrDiskFull && g.gcHanderFunc != nil { // if the error is disk full and there is a GC handler
-		g.gcHanderFunc(g.VFS, len(src)*g.multiplier) // call the GC handler
-		err = g.VFS.Set(key, src)                    // try again after GC if it still fails return the error
+		reclaimedBytes, deletedFiles := g.gcHanderFunc(g.VFS, uint(len(src)*g.multiplier)) // call the GC handler
+		g.reclaimedBytes += reclaimedBytes
+		g.deletedFiles += deletedFiles
+		err = g.VFS.Set(key, src) // try again after GC if it still fails return the error
 	}
 
 	return err