datastore: Concurrency fix, closes #77

datastore/datastore.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"io"
 	"net/mail"
+	"sync"
 	"time"
 
 	"github.com/jhillyerd/enmime"
@@ -22,6 +23,8 @@ var (
 type DataStore interface {
 	MailboxFor(emailAddress string) (Mailbox, error)
 	AllMailboxes() ([]Mailbox, error)
+	// LockFor is a temporary hack to fix #77 until Datastore revamp
+	LockFor(emailAddress string) (*sync.RWMutex, error)
 }
 
 // Mailbox is an interface to get and manipulate messages in a DataStore

datastore/lock.go

@@ -0,0 +1,19 @@
+package datastore
+
+import (
+	"strconv"
+	"sync"
+)
+
+type HashLock [4096]sync.RWMutex
+
+func (h *HashLock) Get(hash string) *sync.RWMutex {
+	if len(hash) < 3 {
+		return nil
+	}
+	i, err := strconv.ParseInt(hash[0:3], 16, 0)
+	if err != nil {
+		return nil
+	}
+	return &h[i]
+}

datastore/lock_test.go

@@ -0,0 +1,61 @@
+package datastore_test
+
+import (
+	"testing"
+
+	"github.com/jhillyerd/inbucket/datastore"
+)
+
+func TestHashLock(t *testing.T) {
+	hl := &datastore.HashLock{}
+
+	// Invalid hashes
+	testCases := []struct {
+		name, input string
+	}{
+		{"empty", ""},
+		{"short", "a0"},
+		{"badhex", "zzzzzzzzzzzzzzzzzzzzzzz"},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.input, func(t *testing.T) {
+			l := hl.Get(tc.input)
+			if l != nil {
+				t.Errorf("Expected nil lock for %s %q, got %v", tc.name, tc.input, l)
+			}
+		})
+	}
+
+	// Valid hashes
+	testStrings := []string{
+		"deadbeef",
+		"00000000",
+		"ffffffff",
+	}
+	for _, ts := range testStrings {
+		t.Run(ts, func(t *testing.T) {
+			l := hl.Get(ts)
+			if l == nil {
+				t.Errorf("Expeced non-nil lock for hex string %q", ts)
+			}
+		})
+	}
+
+	a := hl.Get("deadbeef")
+	b := hl.Get("deadbeef")
+	if a != b {
+		t.Errorf("Expected identical locks for identical hashes, got: %p != %p", a, b)
+	}
+
+	a = hl.Get("deadbeef")
+	b = hl.Get("d3adb33f")
+	if a == b {
+		t.Errorf("Expected different locks for different hashes, got: %p == %p", a, b)
+	}
+
+	a = hl.Get("deadbeef")
+	b = hl.Get("deadb33f")
+	if a != b {
+		t.Errorf("Expected identical locks for identical leading hashes, got: %p != %p", a, b)
+	}
+}

datastore/testing.go

@@ -3,6 +3,7 @@ package datastore
 import (
 	"io"
 	"net/mail"
+	"sync"
 	"time"
 
 	"github.com/jhillyerd/enmime"
@@ -26,6 +27,10 @@ func (m *MockDataStore) AllMailboxes() ([]Mailbox, error) {
 	return args.Get(0).([]Mailbox), args.Error(1)
 }
 
+func (m *MockDataStore) LockFor(name string) (*sync.RWMutex, error) {
+	return &sync.RWMutex{}, nil
+}
+
 // MockMailbox is a shared mock for unit testing
 type MockMailbox struct {
 	mock.Mock