WriteInto handles length_with_null values of 1 better.

In debug builds on VS2010, the old code triggered a debug assertion in
xstring, since [0] was being accessed and the size of the array was 0.

A |length_with_null| of 1 is considered a valid use of this function, so
an alternate implementation is used which returns the data() pointer.

BUG=None
TEST=net_unittests --gtest_filter=*Digest* on debug on VS2010 works.


Review URL: http://codereview.chromium.org/8143001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@106062 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 42 insertions, 0 deletions

diff --git a/base/string_util_unittest.cc b/base/string_util_unittest.cc
index d449dee..f354a99 100644
--- a/base/string_util_unittest.cc
+++ b/base/string_util_unittest.cc
@@ -1079,4 +1079,46 @@ TEST(StringUtilTest, ContainsOnlyChars) {
   EXPECT_FALSE(ContainsOnlyChars("123a", "4321"));
 }
 
+TEST(StringUtilTest, WriteInto) {
+  // Validate that WriteInto reserves enough space and
+  // sizes a string correctly.
+  std::string buffer;
+  const char kOriginal[] = "supercali";
+  strncpy(WriteInto(&buffer, 1), kOriginal, 0);
+  EXPECT_STREQ("", buffer.c_str());
+  EXPECT_EQ(0u, buffer.size());
+  strncpy(WriteInto(&buffer, 2), kOriginal, 1);
+  EXPECT_STREQ("s", buffer.c_str());
+  EXPECT_EQ(1u, buffer.size());
+  strncpy(WriteInto(&buffer, 3), kOriginal, 2);
+  EXPECT_STREQ("su", buffer.c_str());
+  EXPECT_EQ(2u, buffer.size());
+  strncpy(WriteInto(&buffer, 5001), kOriginal, 5000);
+  EXPECT_STREQ("supercali", buffer.c_str());
+  EXPECT_EQ(5000u, buffer.size());
+  strncpy(WriteInto(&buffer, 3), kOriginal, 2);
+  EXPECT_STREQ("su", buffer.c_str());
+  EXPECT_EQ(2u, buffer.size());
+  strncpy(WriteInto(&buffer, 1), kOriginal, 0);
+  EXPECT_STREQ("", buffer.c_str());
+  EXPECT_EQ(0u, buffer.size());
+
+  // Validate that WriteInto returns NULL only when
+  // |length_with_null| == 1.
+  EXPECT_TRUE(WriteInto(&buffer, 1) == NULL);
+  EXPECT_TRUE(WriteInto(&buffer, 2) != NULL);
+
+  // Validate that WriteInto doesn't modify other strings
+  // when using a Copy-on-Write implementation.
+  const char kLive[] = "live";
+  const char kDead[] = "dead";
+  const std::string live = kLive;
+  std::string dead = live;
+  strncpy(WriteInto(&dead, 5), kDead, 4);
+  EXPECT_STREQ(kDead, dead.c_str());
+  EXPECT_EQ(4u, dead.size());
+  EXPECT_STREQ(kLive, live.c_str());
+  EXPECT_EQ(4u, live.size());
+}
+
 }  // namespace base