Base: Change ReadPlatformFile to perform a best

effort read of the requested data, and add another
function (ReadPlatformFileNoBestEffort) that just
forwards the call to the OS.

Now ReadPlatformFile and WritePlatformFile behave
the same way.

BUG=none
TEST=base_unittests
Review URL: http://codereview.chromium.org/7821013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@99264 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 8 insertions, 18 deletions

diff --git a/base/platform_file_unittest.cc b/base/platform_file_unittest.cc
index 7eb1af9..1acbaa6 100644
--- a/base/platform_file_unittest.cc
+++ b/base/platform_file_unittest.cc
@@ -13,24 +13,7 @@ namespace {
 // Reads from a file the given number of bytes, or until EOF is reached.
 // Returns the number of bytes read.
 int ReadFully(base::PlatformFile file, int64 offset, char* data, int size) {
-  int total_bytes_read = 0;
-  int bytes_read;
-  while (total_bytes_read < size) {
-    bytes_read = base::ReadPlatformFile(
-        file, offset + total_bytes_read, &data[total_bytes_read],
-        size - total_bytes_read);
-
-    // If we reached EOF, bytes_read will be 0.
-    if (bytes_read == 0)
-      return total_bytes_read;
-
-    if ((bytes_read < 0) || (bytes_read > size - total_bytes_read))
-      return -1;
-
-    total_bytes_read += bytes_read;
-  }
-
-  return total_bytes_read;
+  return base::ReadPlatformFile(file, offset, data, size);
 }
 
 // Writes the given number of bytes to a file.
@@ -192,6 +175,13 @@ TEST(PlatformFile, ReadWritePlatformFile) {
   for (int i = 0; i < bytes_read; i++)
     EXPECT_EQ(data_to_write[i], data_read_1[i]);
 
+  // Read again, but using the trivial native wrapper.
+  bytes_read = base::ReadPlatformFileNoBestEffort(file, 0, data_read_1,
+                                                  kTestDataSize);
+  EXPECT_LE(bytes_read, kTestDataSize);
+  for (int i = 0; i < bytes_read; i++)
+    EXPECT_EQ(data_to_write[i], data_read_1[i]);
+
   // Write past the end of the file.
   const int kOffsetBeyondEndOfFile = 10;
   const int kPartialWriteLength = 2;