accounts: cache key addresses

In order to avoid disk thrashing for Accounts and HasAccount,
address->key file mappings are now cached in memory. This makes it no
longer necessary to keep the key address in the file name. The address
of each key is derived from file content instead.

There are minor user-visible changes:

- "geth account list" now reports key file paths alongside the address.
- If multiple keys are present for an address, unlocking by address is
  not possible. Users are directed to remove the duplicate files
  instead. Unlocking by index is still possible.
- Key files are overwritten written in place when updating the password.

accounts/accounts_test.go

@@ -19,28 +19,70 @@ package accounts
 import (
 	"io/ioutil"
 	"os"
+	"runtime"
+	"strings"
 	"testing"
 	"time"
+
+	"github.com/ethereum/go-ethereum/common"
 )
 
 var testSigData = make([]byte, 32)
 
+func TestManager(t *testing.T) {
+	dir, am := tmpManager(t, true)
+	defer os.RemoveAll(dir)
+
+	a, err := am.NewAccount("foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasPrefix(a.File, dir) {
+		t.Errorf("account file %s doesn't have dir prefix", a.File)
+	}
+	stat, err := os.Stat(a.File)
+	if err != nil {
+		t.Fatalf("account file %s doesn't exist (%v)", a.File, err)
+	}
+	if runtime.GOOS != "windows" && stat.Mode() != 0600 {
+		t.Fatalf("account file has wrong mode: got %o, want %o", stat.Mode(), 0600)
+	}
+	if !am.HasAddress(a.Address) {
+		t.Errorf("HasAccount(%x) should've returned true", a.Address)
+	}
+	if err := am.Update(a, "foo", "bar"); err != nil {
+		t.Errorf("Update error: %v", err)
+	}
+	if err := am.DeleteAccount(a, "bar"); err != nil {
+		t.Errorf("DeleteAccount error: %v", err)
+	}
+	if common.FileExist(a.File) {
+		t.Errorf("account file %s should be gone after DeleteAccount", a.File)
+	}
+	if am.HasAddress(a.Address) {
+		t.Errorf("HasAccount(%x) should've returned true after DeleteAccount", a.Address)
+	}
+}
+
 func TestSign(t *testing.T) {
-	dir, am := tmpManager(t, false)
+	dir, am := tmpManager(t, true)
 	defer os.RemoveAll(dir)
 
 	pass := "" // not used but required by API
 	a1, err := am.NewAccount(pass)
-	am.Unlock(a1, "")
-
-	_, err = am.Sign(a1, testSigData)
 	if err != nil {
 		t.Fatal(err)
 	}
+	if err := am.Unlock(a1, ""); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := am.Sign(a1, testSigData); err != nil {
+		t.Fatal(err)
+	}
 }
 
 func TestTimedUnlock(t *testing.T) {
-	dir, am := tmpManager(t, false)
+	dir, am := tmpManager(t, true)
 	defer os.RemoveAll(dir)
 
 	pass := "foo"
@@ -142,7 +184,7 @@ func tmpManager(t *testing.T, encrypted bool) (string, *Manager) {
 	}
 	new := NewPlaintextManager
 	if encrypted {
-		new = func(kd string) *Manager { return NewManager(kd, LightScryptN, LightScryptP) }
+		new = func(kd string) *Manager { return NewManager(kd, veryLightScryptN, veryLightScryptP) }
 	}
 	return d, new(d)
 }