feat(d-eyes): init

filedetection/hashes.go

@@ -0,0 +1,87 @@
+package filedetection
+
+import (
+	"crypto/md5"
+	"crypto/sha256"
+	"encoding/hex"
+	"io"
+	"os"
+	"sync"
+)
+
+var globalHasher *CachingHasher
+
+func init() {
+	globalHasher = NewCachingHasher()
+}
+
+// ComputeHashes computes the md5 and sha256 hashes of a given file.
+func ComputeHashes(file string) (md5sum, sha256sum string, err error) {
+	return globalHasher.ComputeHashes(file)
+}
+
+type multiHash struct {
+	md5sum    string
+	sha256sum string
+}
+
+type CachingHasher struct {
+	hashes map[string]*multiHash
+	mux    *sync.RWMutex
+}
+
+func NewCachingHasher() *CachingHasher {
+	return &CachingHasher{
+		hashes: map[string]*multiHash{},
+		mux:    &sync.RWMutex{},
+	}
+}
+
+func (h *CachingHasher) readCache(file string) (*multiHash, bool) {
+	h.mux.RLock()
+	defer h.mux.RUnlock()
+
+	hashes, ok := h.hashes[file]
+	return hashes, ok
+}
+
+func (h *CachingHasher) writeCache(file string, hashes *multiHash) {
+	h.mux.Lock()
+	defer h.mux.Unlock()
+
+	h.hashes[file] = hashes
+}
+
+// ComputeHashes computes the md5 and sha256 hashes of a given file.
+func (h *CachingHasher) ComputeHashes(file string) (md5sum, sha256sum string, err error) {
+	hashes, ok := h.readCache(file)
+	if ok {
+		return hashes.md5sum, hashes.sha256sum, nil
+	}
+
+	var f *os.File
+	f, err = os.OpenFile(file, os.O_RDONLY, 0666)
+	if err != nil {
+		return
+	}
+	defer f.Close()
+
+	h5 := md5.New()
+	h256 := sha256.New()
+
+	teeH5 := io.TeeReader(f, h5)
+	_, err = io.Copy(h256, teeH5)
+	if err != nil {
+		return
+	}
+
+	md5sum = hex.EncodeToString(h5.Sum(nil))
+	sha256sum = hex.EncodeToString(h256.Sum(nil))
+
+	h.writeCache(file, &multiHash{
+		md5sum:    md5sum,
+		sha256sum: sha256sum,
+	})
+
+	return
+}