1 files changed, 50 insertions, 0 deletions
diff --git a/vendor/github.com/getlantern/errors/hide.go b/vendor/github.com/getlantern/errors/hide.go
new file mode 100644
index 0000000..f10d863
--- /dev/null
+++ b/vendor/github.com/getlantern/errors/hide.go
@@ -0,0 +1,50 @@
+package errors
+
+import (
+	"encoding/binary"
+	"sync"
+
+	"github.com/getlantern/hidden"
+)
+
+var (
+	hiddenErrors = make([]*structured, 100)
+	nextID       = uint64(0)
+	hiddenMutex  sync.RWMutex
+)
+
+// This trick saves the error to a ring buffer and embeds a non-printing
+// hiddenID in the error's description, so that if the errors is later wrapped
+// by a standard error using something like
+// fmt.Errorf("An error occurred: %v", thisError), we can subsequently extract
+// the error simply using the hiddenID in the string.
+func (e *structured) save() {
+	hiddenMutex.Lock()
+	b := make([]byte, 8)
+	binary.BigEndian.PutUint64(b, nextID)
+	e.id = nextID
+	e.hiddenID = hidden.ToString(b)
+	hiddenErrors[idxForID(nextID)] = e
+	nextID++
+	hiddenMutex.Unlock()
+}
+
+func get(hiddenID []byte) Error {
+	if len(hiddenID) != 8 {
+		return nil
+	}
+	id := binary.BigEndian.Uint64(hiddenID)
+	hiddenMutex.RLock()
+	err := hiddenErrors[idxForID(id)]
+	hiddenMutex.RUnlock()
+	if err != nil && err.id == id {
+		// Found it!
+		return err
+	}
+	// buffer has rolled over
+	return nil
+}
+
+func idxForID(id uint64) int {
+	return int(id % uint64(len(hiddenErrors)))
+}