1 files changed, 94 insertions, 0 deletions
diff --git a/src/cmd/gofix/hashsum.go b/src/cmd/gofix/hashsum.go
new file mode 100644
index 000000000..0df6ad749
--- /dev/null
+++ b/src/cmd/gofix/hashsum.go
@@ -0,0 +1,94 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"go/ast"
+)
+
+func init() {
+	register(hashSumFix)
+}
+
+var hashSumFix = fix{
+	"hashsum",
+	"2011-11-30",
+	hashSumFn,
+	`Pass a nil argument to calls to hash.Sum
+
+This fix rewrites code so that it passes a nil argument to hash.Sum.
+The additional argument will allow callers to avoid an
+allocation in the future.
+
+http://codereview.appspot.com/5448065
+`,
+}
+
+// Type-checking configuration: tell the type-checker this basic
+// information about types, functions, and variables in external packages.
+var hashSumTypeConfig = &TypeConfig{
+	Var: map[string]string{
+		"crypto.MD4":       "crypto.Hash",
+		"crypto.MD5":       "crypto.Hash",
+		"crypto.SHA1":      "crypto.Hash",
+		"crypto.SHA224":    "crypto.Hash",
+		"crypto.SHA256":    "crypto.Hash",
+		"crypto.SHA384":    "crypto.Hash",
+		"crypto.SHA512":    "crypto.Hash",
+		"crypto.MD5SHA1":   "crypto.Hash",
+		"crypto.RIPEMD160": "crypto.Hash",
+	},
+
+	Func: map[string]string{
+		"adler32.New":    "hash.Hash",
+		"crc32.New":      "hash.Hash",
+		"crc32.NewIEEE":  "hash.Hash",
+		"crc64.New":      "hash.Hash",
+		"fnv.New32a":     "hash.Hash",
+		"fnv.New32":      "hash.Hash",
+		"fnv.New64a":     "hash.Hash",
+		"fnv.New64":      "hash.Hash",
+		"hmac.New":       "hash.Hash",
+		"hmac.NewMD5":    "hash.Hash",
+		"hmac.NewSHA1":   "hash.Hash",
+		"hmac.NewSHA256": "hash.Hash",
+		"md4.New":        "hash.Hash",
+		"md5.New":        "hash.Hash",
+		"ripemd160.New":  "hash.Hash",
+		"sha1.New224":    "hash.Hash",
+		"sha1.New":       "hash.Hash",
+		"sha256.New224":  "hash.Hash",
+		"sha256.New":     "hash.Hash",
+		"sha512.New384":  "hash.Hash",
+		"sha512.New":     "hash.Hash",
+	},
+
+	Type: map[string]*Type{
+		"crypto.Hash": {
+			Method: map[string]string{
+				"New": "func() hash.Hash",
+			},
+		},
+	},
+}
+
+func hashSumFn(f *ast.File) bool {
+	typeof, _ := typecheck(hashSumTypeConfig, f)
+
+	fixed := false
+
+	walk(f, func(n interface{}) {
+		call, ok := n.(*ast.CallExpr)
+		if ok && len(call.Args) == 0 {
+			sel, ok := call.Fun.(*ast.SelectorExpr)
+			if ok && sel.Sel.Name == "Sum" && typeof[sel.X] == "hash.Hash" {
+				call.Args = append(call.Args, ast.NewIdent("nil"))
+				fixed = true
+			}
+		}
+	})
+
+	return fixed
+}