From 2da8e34079b01cf51eb65b5216ba43d8b33efc08 Mon Sep 17 00:00:00 2001
From: "Andrew C. Bodine" <acbodine@us.ibm.com>
Date: Tue, 16 Dec 2014 15:06:35 -0800
Subject: [PATCH] Closes #9311 Handles container id/name collisions against
 daemon functionalities according to #8069

Signed-off-by: Andrew C. Bodine <acbodine@us.ibm.com>
---
 truncindex/truncindex.go      | 22 ++++++++++------------
 truncindex/truncindex_test.go |  5 +++++
 2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/truncindex/truncindex.go b/truncindex/truncindex.go
index eec5597..73c7e24 100644
--- a/truncindex/truncindex.go
+++ b/truncindex/truncindex.go
@@ -10,10 +10,8 @@ import (
 )
 
 var (
-	// ErrNoID is thrown when attempting to use empty prefixes
-	ErrNoID = errors.New("prefix can't be empty")
-	// ErrDuplicateID is thrown when a duplicated id was found
-	ErrDuplicateID = errors.New("multiple IDs were found")
+	ErrEmptyPrefix     = errors.New("Prefix can't be empty")
+	ErrAmbiguousPrefix = errors.New("Multiple IDs found with provided prefix")
 )
 
 func init() {
@@ -47,7 +45,7 @@ func (idx *TruncIndex) addID(id string) error {
 		return fmt.Errorf("illegal character: ' '")
 	}
 	if id == "" {
-		return ErrNoID
+		return ErrEmptyPrefix
 	}
 	if _, exists := idx.ids[id]; exists {
 		return fmt.Errorf("id already exists: '%s'", id)
@@ -87,26 +85,26 @@ func (idx *TruncIndex) Delete(id string) error {
 // Get retrieves an ID from the TruncIndex. If there are multiple IDs
 // with the given prefix, an error is thrown.
 func (idx *TruncIndex) Get(s string) (string, error) {
-	idx.RLock()
-	defer idx.RUnlock()
+	if s == "" {
+		return "", ErrEmptyPrefix
+	}
 	var (
 		id string
 	)
-	if s == "" {
-		return "", ErrNoID
-	}
 	subTreeVisitFunc := func(prefix patricia.Prefix, item patricia.Item) error {
 		if id != "" {
 			// we haven't found the ID if there are two or more IDs
 			id = ""
-			return ErrDuplicateID
+			return ErrAmbiguousPrefix
 		}
 		id = string(prefix)
 		return nil
 	}
 
+	idx.RLock()
+	defer idx.RUnlock()
 	if err := idx.trie.VisitSubtree(patricia.Prefix(s), subTreeVisitFunc); err != nil {
-		return "", fmt.Errorf("no such id: %s", s)
+		return "", err
 	}
 	if id != "" {
 		return id, nil
diff --git a/truncindex/truncindex_test.go b/truncindex/truncindex_test.go
index 32c41c7..8ad1634 100644
--- a/truncindex/truncindex_test.go
+++ b/truncindex/truncindex_test.go
@@ -59,6 +59,11 @@ func TestTruncIndex(t *testing.T) {
 	assertIndexGet(t, index, id[:4], "", true)
 	assertIndexGet(t, index, id[:1], "", true)
 
+	// An ambiguous id prefix should return an error
+	if _, err := index.Get(id[:4]); err == nil || err == nil {
+		t.Fatal("An ambiguous id prefix should return an error")
+	}
+
 	// 7 characters should NOT conflict
 	assertIndexGet(t, index, id[:7], id, false)
 	assertIndexGet(t, index, id2[:7], id2, false)