From ca154c399b879ad17804af5d9a81e607e049861e Mon Sep 17 00:00:00 2001 From: Philip Van Hoof Date: Wed, 21 Sep 2011 19:59:03 +0200 Subject: [PATCH] GMappedFile: Add API to create from an existing file descriptor At Tracker we want to mmap files using O_NOATIME. With GMappedFile this is at the moment impossible. For that reason I added the constructor new_from_fd to the GMappedFile type. https://bugzilla.gnome.org/show_bug.cgi?id=659754 --- glib/glib.symbols | 1 + glib/gmappedfile.c | 174 ++++++++++++++++++++++++++-------------- glib/gmappedfile.h | 3 + glib/tests/mappedfile.c | 48 +++++++++++ 4 files changed, 164 insertions(+), 62 deletions(-) diff --git a/glib/glib.symbols b/glib/glib.symbols index 03cbb4465..6c19c221b 100644 --- a/glib/glib.symbols +++ b/glib/glib.symbols @@ -636,6 +636,7 @@ g_timeout_add_seconds_full g_timeout_source_new g_timeout_source_new_seconds g_mapped_file_new +g_mapped_file_new_from_fd g_mapped_file_get_length g_mapped_file_get_contents g_mapped_file_ref diff --git a/glib/gmappedfile.c b/glib/gmappedfile.c index f94bf3104..8d7d0fab4 100644 --- a/glib/gmappedfile.c +++ b/glib/gmappedfile.c @@ -103,62 +103,15 @@ g_mapped_file_destroy (GMappedFile *file) g_slice_free (GMappedFile, file); } -/** - * g_mapped_file_new: - * @filename: The path of the file to load, in the GLib filename encoding - * @writable: whether the mapping should be writable - * @error: return location for a #GError, or %NULL - * - * Maps a file into memory. On UNIX, this is using the mmap() function. - * - * If @writable is %TRUE, the mapped buffer may be modified, otherwise - * it is an error to modify the mapped buffer. Modifications to the buffer - * are not visible to other processes mapping the same file, and are not - * written back to the file. - * - * Note that modifications of the underlying file might affect the contents - * of the #GMappedFile. Therefore, mapping should only be used if the file - * will not be modified, or if all modifications of the file are done - * atomically (e.g. using g_file_set_contents()). - * - * If @filename is the name of an empty, regular file, the function - * will successfully return an empty #GMappedFile. In other cases of - * size 0 (e.g. device files such as /dev/null), @error will be set - * to the #GFileError value #G_FILE_ERROR_INVAL. - * - * Return value: a newly allocated #GMappedFile which must be unref'd - * with g_mapped_file_unref(), or %NULL if the mapping failed. - * - * Since: 2.8 - */ -GMappedFile * -g_mapped_file_new (const gchar *filename, - gboolean writable, - GError **error) +static GMappedFile* +mapped_file_new_from_fd (int fd, + gboolean writable, + const gchar *filename, + GError **error) { GMappedFile *file; - int fd; struct stat st; - g_return_val_if_fail (filename != NULL, NULL); - g_return_val_if_fail (!error || *error == NULL, NULL); - - fd = g_open (filename, (writable ? O_RDWR : O_RDONLY) | _O_BINARY, 0); - if (fd == -1) - { - int save_errno = errno; - gchar *display_filename = g_filename_display_name (filename); - - g_set_error (error, - G_FILE_ERROR, - g_file_error_from_errno (save_errno), - _("Failed to open file '%s': open() failed: %s"), - display_filename, - g_strerror (save_errno)); - g_free (display_filename); - return NULL; - } - file = g_slice_new0 (GMappedFile); file->ref_count = 1; file->free_func = g_mapped_file_destroy; @@ -166,13 +119,16 @@ g_mapped_file_new (const gchar *filename, if (fstat (fd, &st) == -1) { int save_errno = errno; - gchar *display_filename = g_filename_display_name (filename); + gchar *display_filename = filename ? g_filename_display_name (filename) : NULL; g_set_error (error, G_FILE_ERROR, g_file_error_from_errno (save_errno), - _("Failed to get attributes of file '%s': fstat() failed: %s"), - display_filename, + _("Failed to get attributes of file '%s%s%s%s': fstat() failed: %s"), + display_filename ? display_filename : "fd", + display_filename ? "' " : "", + display_filename ? display_filename : "", + display_filename ? "'" : "", g_strerror (save_errno)); g_free (display_filename); goto out; @@ -186,7 +142,6 @@ g_mapped_file_new (const gchar *filename, { file->length = 0; file->contents = NULL; - close (fd); return file; } @@ -230,28 +185,123 @@ g_mapped_file_new (const gchar *filename, if (file->contents == MAP_FAILED) { int save_errno = errno; - gchar *display_filename = g_filename_display_name (filename); - + gchar *display_filename = filename ? g_filename_display_name (filename) : NULL; + g_set_error (error, G_FILE_ERROR, g_file_error_from_errno (save_errno), - _("Failed to map file '%s': mmap() failed: %s"), - display_filename, + _("Failed to map %s%s%s%s: mmap() failed: %s"), + display_filename ? display_filename : "fd", + display_filename ? "' " : "", + display_filename ? display_filename : "", + display_filename ? "'" : "", g_strerror (save_errno)); g_free (display_filename); goto out; } - close (fd); return file; out: - close (fd); g_slice_free (GMappedFile, file); return NULL; } +/** + * g_mapped_file_new: + * @filename: The path of the file to load, in the GLib filename encoding + * @writable: whether the mapping should be writable + * @error: return location for a #GError, or %NULL + * + * Maps a file into memory. On UNIX, this is using the mmap() function. + * + * If @writable is %TRUE, the mapped buffer may be modified, otherwise + * it is an error to modify the mapped buffer. Modifications to the buffer + * are not visible to other processes mapping the same file, and are not + * written back to the file. + * + * Note that modifications of the underlying file might affect the contents + * of the #GMappedFile. Therefore, mapping should only be used if the file + * will not be modified, or if all modifications of the file are done + * atomically (e.g. using g_file_set_contents()). + * + * If @filename is the name of an empty, regular file, the function + * will successfully return an empty #GMappedFile. In other cases of + * size 0 (e.g. device files such as /dev/null), @error will be set + * to the #GFileError value #G_FILE_ERROR_INVAL. + * + * Return value: a newly allocated #GMappedFile which must be unref'd + * with g_mapped_file_unref(), or %NULL if the mapping failed. + * + * Since: 2.8 + */ +GMappedFile * +g_mapped_file_new (const gchar *filename, + gboolean writable, + GError **error) +{ + GMappedFile *file; + int fd; + + g_return_val_if_fail (filename != NULL, NULL); + g_return_val_if_fail (!error || *error == NULL, NULL); + + fd = g_open (filename, (writable ? O_RDWR : O_RDONLY) | _O_BINARY, 0); + if (fd == -1) + { + int save_errno = errno; + gchar *display_filename = g_filename_display_name (filename); + + g_set_error (error, + G_FILE_ERROR, + g_file_error_from_errno (save_errno), + _("Failed to open file '%s': open() failed: %s"), + display_filename, + g_strerror (save_errno)); + g_free (display_filename); + return NULL; + } + + file = mapped_file_new_from_fd (fd, writable, filename, error); + + close (fd); + + return file; +} + + +/** + * g_mapped_file_new_from_fd: + * @fd: The file descriptor of the file to load + * @writable: whether the mapping should be writable + * @error: return location for a #GError, or %NULL + * + * Maps a file into memory. On UNIX, this is using the mmap() function. + * + * If @writable is %TRUE, the mapped buffer may be modified, otherwise + * it is an error to modify the mapped buffer. Modifications to the buffer + * are not visible to other processes mapping the same file, and are not + * written back to the file. + * + * Note that modifications of the underlying file might affect the contents + * of the #GMappedFile. Therefore, mapping should only be used if the file + * will not be modified, or if all modifications of the file are done + * atomically (e.g. using g_file_set_contents()). + * + * Return value: a newly allocated #GMappedFile which must be unref'd + * with g_mapped_file_unref(), or %NULL if the mapping failed. + * + * Since: 2.30 + */ +GMappedFile * +g_mapped_file_new_from_fd (gint fd, + gboolean writable, + GError **error) +{ + return mapped_file_new_from_fd (fd, writable, NULL, error); +} + /** * g_mapped_file_get_length: * @file: a #GMappedFile diff --git a/glib/gmappedfile.h b/glib/gmappedfile.h index dbb3f89e6..0d3c0f940 100644 --- a/glib/gmappedfile.h +++ b/glib/gmappedfile.h @@ -35,6 +35,9 @@ typedef struct _GMappedFile GMappedFile; GMappedFile *g_mapped_file_new (const gchar *filename, gboolean writable, GError **error) G_GNUC_MALLOC; +GMappedFile *g_mapped_file_new_from_fd (gint fd, + gboolean writable, + GError **error) G_GNUC_MALLOC; gsize g_mapped_file_get_length (GMappedFile *file); gchar *g_mapped_file_get_contents (GMappedFile *file); GMappedFile *g_mapped_file_ref (GMappedFile *file); diff --git a/glib/tests/mappedfile.c b/glib/tests/mappedfile.c index d6c6961d3..be2e6f69a 100644 --- a/glib/tests/mappedfile.c +++ b/glib/tests/mappedfile.c @@ -4,6 +4,9 @@ #ifdef HAVE_UNISTD_H #include #endif +#include +#include +#include static void test_basic (void) @@ -98,6 +101,50 @@ test_writable (void) g_mapped_file_free (file); } +static void +test_writable_fd (void) +{ + GMappedFile *file; + GError *error; + gchar *contents; + const gchar *old = "MMMMMMMMMMMMMMMMMMMMMMMMM"; + const gchar *new = "abcdefghijklmnopqrstuvxyz"; + int fd; + + if (access (SRCDIR "/4096-random-bytes", W_OK) != 0) + { + g_test_message ("Skipping writable mapping test"); + return; + } + + error = NULL; + fd = open (SRCDIR "/4096-random-bytes", O_RDWR, 0); + g_assert (fd != -1); + file = g_mapped_file_new_from_fd (fd, TRUE, &error); + g_assert_no_error (error); + + contents = g_mapped_file_get_contents (file); + g_assert (strncmp (contents, old, strlen (old)) == 0); + + memcpy (contents, new, strlen (new)); + g_assert (strncmp (contents, new, strlen (new)) == 0); + + g_mapped_file_free (file); + close (fd); + + error = NULL; + fd = open (SRCDIR "/4096-random-bytes", O_RDWR, 0); + g_assert (fd != -1); + file = g_mapped_file_new_from_fd (fd, TRUE, &error); + g_assert_no_error (error); + + contents = g_mapped_file_get_contents (file); + g_assert (strncmp (contents, old, strlen (old)) == 0); + + g_mapped_file_free (file); + +} + int main (int argc, char *argv[]) { @@ -108,6 +155,7 @@ main (int argc, char *argv[]) g_test_add_func ("/mappedfile/device", test_device); g_test_add_func ("/mappedfile/nonexisting", test_nonexisting); g_test_add_func ("/mappedfile/writable", test_writable); + g_test_add_func ("/mappedfile/writable_fd", test_writable_fd); return g_test_run (); }