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ReadFile() attempted to continue reading after a short read. In most cases, this is fine. However, ReadFile() would keep trying to fill a partially-filled buffer until experiencing a 0-length read(), signaling end-of-file. For certain weird file descriptors like terminal input, EOF is an ephemeral condition, and attempting to read beyond EOF doesn’t actually return 0 (EOF) provided that they remain open, it will block waiting for more input. Consequently, ReadFile() and anything based on ReadFile() had an undocumented and quirky interface, which was that any short read that it returned (not an underlying short read) actually indicated EOF. This facet of ReadFile() was unexpected, so it’s being removed. The new behavior is that ReadFile() will return an underlying short read. The behavior of FileReaderInterface::Read() is updated in accordance with this change. Upon experiencing a short read, the caller can determine the best action. Most callers were already prepared for this behavior. Outside of util/file, only crashpad_database_util properly implemented EOF detection according to previous semantics, and adapting it to new semantics is trivial. Callers who require an exact-length read can use the new ReadFileExactly(), or the newly renamed LoggingReadFileExactly() or CheckedReadFileExactly(). These functions will retry following a short read. The renamed functions were previously called LoggingReadFile() and CheckedReadFile(), but those names implied that they were simply wrapping ReadFile(), which is not the case. They wrapped ReadFile() and further, insisted on a full read. Since ReadFile()’s semantics are now changing but these functions’ are not, they’re now even more distinct from ReadFile(), and must be renamed to avoid confusion. Test: * Change-Id: I06b77e0d6ad8719bd2eb67dab93a8740542dd908 Reviewed-on: https://chromium-review.googlesource.com/456676 Reviewed-by: Robert Sesek <rsesek@chromium.org>