Eliminate an extra allocation in encryptor_win when en/decrypting.

crypto/encryptor_win.cc

Index: crypto/encryptor_win.cc
diff --git a/crypto/encryptor_win.cc b/crypto/encryptor_win.cc
index 088c9e56d680f9a0a9dddd2f666077f690bbd448..081ea6fbea4a901b39b1c66f5387f5281665aae1 100644
--- a/crypto/encryptor_win.cc
+++ b/crypto/encryptor_win.cc
@@ -4,8 +4,7 @@
 
 #include "crypto/encryptor.h"
 
-#include <vector>
-
+#include "base/string_util.h"
 #include "crypto/symmetric_key.h"
 
 namespace crypto {
@@ -85,15 +84,18 @@ bool Encryptor::Encrypt(const base::StringPiece& plaintext,
   DWORD total_len = data_len + block_size_;
 
   // CryptoAPI encrypts/decrypts in place.
-  std::vector<BYTE> tmp(total_len);
-  memcpy(&tmp[0], plaintext.data(), data_len);
-
-  BOOL ok = CryptEncrypt(capi_key_.get(), NULL, TRUE, 0, &tmp[0],
-                         &data_len, total_len);
-  if (!ok)
+  plaintext.CopyToString(ciphertext);
+
+  BOOL ok = CryptEncrypt(
+      capi_key_.get(), NULL, TRUE, 0,
+      reinterpret_cast<BYTE*>(WriteInto(ciphertext, total_len+1)),

[wtc, 2011/06/29 00:46:41]

Add spaces around '+'.

It is safer to do things in this order:

1. Call WriteInto(ciphertext, total_len + 1) to get a pointer
to an output buffer of the right size.

2. Copy plaintext into the output buffer.

3. Pass the output buffer to CryptEncrypt.

The reason to call WriteInto before copying is that I
am not sure if WriteInto preserves the existing data in
the std::string.

I prefer ciphertext->clear() to ciphertext->resize(0).

+      &data_len, total_len);
+  if (!ok) {
+    ciphertext->resize(0);
     return false;
+  }
 
-  ciphertext->assign(reinterpret_cast<char*>(&tmp[0]), data_len);
+  ciphertext->resize(data_len);
   return true;
 }
 
@@ -103,16 +105,19 @@ bool Encryptor::Decrypt(const base::StringPiece& ciphertext,
   if (data_len == 0)
     return false;
 
-  std::vector<BYTE> tmp(data_len);
-  memcpy(&tmp[0], ciphertext.data(), data_len);
-
-  BOOL ok = CryptDecrypt(capi_key_.get(), NULL, TRUE, 0, &tmp[0], &data_len);
-  if (!ok)
+  // CryptoAPI encrypts/decrypts in place.
+  ciphertext.CopyToString(plaintext);
+
+  BOOL ok = CryptDecrypt(
+      capi_key_.get(), NULL, TRUE, 0,
+      reinterpret_cast<BYTE*>(WriteInto(plaintext, data_len+1)),
+      &data_len);
+  if (!ok) {
+    plaintext->resize(0);
     return false;
+  }
 
-  DCHECK_GT(tmp.size(), data_len);
-
-  plaintext->assign(reinterpret_cast<char*>(&tmp[0]), data_len);
+  plaintext->resize(data_len);
   return true;
 }