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, 10 insertions, 1 deletions

diff --git a/base/platform_file.h b/base/platform_file.h
index cf3716c..2bfd181 100644
--- a/base/platform_file.h
+++ b/base/platform_file.h
@@ -117,10 +117,19 @@ BASE_EXPORT PlatformFile CreatePlatformFile(const FilePath& name,
 BASE_EXPORT bool ClosePlatformFile(PlatformFile file);
 
 // Reads the given number of bytes (or until EOF is reached) starting with the
-// given offset. Returns the number of bytes read, or -1 on error.
+// given offset. Returns the number of bytes read, or -1 on error. Note that
+// this function makes a best effort to read all data on all platforms, so it is
+// not intended for stream oriented files but instead for cases when the normal
+// expectation is that actually |size| bytes are read unless there is an error.
 BASE_EXPORT int ReadPlatformFile(PlatformFile file, int64 offset,
                                  char* data, int size);
 
+// Reads the given number of bytes (or until EOF is reached) starting with the
+// given offset, but does not make any effort to read all data on all platforms.
+// Returns the number of bytes read, or -1 on error.
+BASE_EXPORT int ReadPlatformFileNoBestEffort(PlatformFile file, int64 offset,
+                                             char* data, int size);
+
 // Writes the given buffer into the file at the given offset, overwritting any
 // data that was previously there. Returns the number of bytes written, or -1
 // on error. Note that this function makes a best effort to write all data on