Introduce mmap_file function

New in v2:

- As Tom pointed out, we don't need to keep the fd around after
  mmapping.  This simplifies things quite a bit, since we don't need a
  new class.  It's now just a function that returns a scoped_mmap.

We already have scoped_mmap, which is a thin RAII layer over mmap.  If
one simply wants to mmap an entire file for reading, it takes a bit of
boilerplate.  This patch introduces the mmap_file function to make this
easier.

gdb/ChangeLog:

	* Makefile.in (COMMON_SFILES): Add common/scoped_mmap.c.
	* common/scoped_mmap.c: New file.
	* common/scoped_mmap.h (destroy): New method.
	(~scoped_mmap, reset): Use destroy.
	(scoped_mmap): New move constructor.
	(mmap_file): New declaration.
	* unittests/scoped_mmap-selftests.c (test_normal,
	test_invalid_filename, run_tests): New functions.
	(_initialize_scoped_mmap_selftests): Register selftest.

1 files changed, 54 insertions, 0 deletions

diff --git a/gdb/unittests/scoped_mmap-selftests.c b/gdb/unittests/scoped_mmap-selftests.c
index ece3d7a..d70a56a 100644
--- a/gdb/unittests/scoped_mmap-selftests.c
+++ b/gdb/unittests/scoped_mmap-selftests.c
@@ -25,6 +25,7 @@
 #if defined(HAVE_SYS_MMAN_H) && defined(HAVE_UNISTD_H)
 
 #include "selftest.h"
+#include "common/gdb_unlinker.h"
 
 #include <unistd.h>
 
@@ -78,6 +79,57 @@ run_tests ()
 }
 
 } /* namespace scoped_mmap */
+
+namespace mmap_file
+{
+
+/* Test the standard usage of mmap_file.  */
+static void
+test_normal ()
+{
+  char filename[] = "scoped_mmapped_file-selftest-XXXXXX";
+  int fd = mkstemp (filename);
+  SELF_CHECK (fd >= 0);
+
+  write (fd, "Hello!", 7);
+  close (fd);
+
+  gdb::unlinker unlink_test_file (filename);
+
+  {
+    ::scoped_mmap m = ::mmap_file (filename);
+
+    SELF_CHECK (m.get () != MAP_FAILED);
+    SELF_CHECK (m.size () == 7);
+    SELF_CHECK (0 == strcmp ((char *) m.get (), "Hello!"));
+  }
+}
+
+/* Calling mmap_file with a non-existent file should throw an exception.  */
+static void
+test_invalid_filename ()
+{
+  bool threw = false;
+
+  try {
+      ::scoped_mmap m = ::mmap_file ("/this/file/should/not/exist");
+  } catch (gdb_exception &e) {
+      threw = true;
+  }
+
+  SELF_CHECK (threw);
+}
+
+
+/* Run selftests.  */
+static void
+run_tests ()
+{
+  test_normal ();
+  test_invalid_filename ();
+}
+
+} /* namespace mmap_file */
 } /* namespace selftests */
 
 #endif /* !defined(HAVE_SYS_MMAN_H) || !defined(HAVE_UNISTD_H) */
@@ -88,5 +140,7 @@ _initialize_scoped_mmap_selftests ()
 #if defined(HAVE_SYS_MMAN_H) && defined(HAVE_UNISTD_H)
   selftests::register_test ("scoped_mmap",
 			    selftests::scoped_mmap::run_tests);
+  selftests::register_test ("mmap_file",
+			    selftests::mmap_file::run_tests);
 #endif
 }