Provide base::EvictFileFromSystemCache on Android on ARM32

base/test/test_file_util_linux.cc

Index: base/test/test_file_util_linux.cc
diff --git a/base/test/test_file_util_linux.cc b/base/test/test_file_util_linux.cc
index 0ef5c0a1571041da64665bbf1673f0cce268396d..cf8b05627297e4daa5b79ff53152b129671f524a 100644
--- a/base/test/test_file_util_linux.cc
+++ b/base/test/test_file_util_linux.cc
@@ -9,11 +9,42 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#if defined(OS_ANDROID)
+#include <asm/unistd.h>
+#include <errno.h>
+#include <linux/fadvise.h>
+#include <sys/syscall.h>
+#endif
+
 #include "base/files/file_path.h"
 #include "base/files/scoped_file.h"
 
 namespace base {
 
+// Inconveniently, the NDK doesn't provide for posix_fadvise
+// until native API level = 21, which we don't use yet, so provide a wrapper, at
+// least on ARM32
+#if defined(OS_ANDROID) && __ANDROID_API__ < 21

[Paweł Hajdan Jr., 2017/05/31 15:28:13]

If this is android-specific, why force a _linux file, instead of moving this to
new _android file?

[Maks Orlovich, 2017/05/31 15:30:25]

So I can put it in an anonymous namespace (seems prudent when duplicating a
syscall wrapper name), while not duplicating the implementation of
EvictFileFromSystemCache that uses it.

+
+namespace {
+int posix_fadvise(int fd, off_t offset, off_t len, int advice) {
+#if defined(ARCH_CPU_ARMEL)
+  // Note that the syscall argument order on ARM is different from the C
+  // function; this is helpfully documented in the Linux posix_fadvise manpage.
+  return syscall(__NR_arm_fadvise64_64, fd, advice,
+                 0,  // Upper 32-bits for offset
+                 offset,
+                 0,  // Upper 32-bits for length
+                 len);
+#endif
+  NOTIMPLEMENTED();
+  return ENOSYS;
+}
+
+}  // namespace
+
+#endif  // OS_ANDROID
+
 bool EvictFileFromSystemCache(const FilePath& file) {
   ScopedFD fd(open(file.value().c_str(), O_RDONLY));
   if (!fd.is_valid())