From cd24e64b088c692c74f4383241df8d48d1007b31 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Michel=20D=C3=A4nzer?= <mdaenzer@redhat.com>

Date: Mon, 6 Jan 2020 18:24:52 +0100

Subject: [PATCH 4/8] util: Add os_same_file_description helper

MIME-Version: 1.0

Content-Type: text/plain; charset=UTF-8

Content-Transfer-Encoding: 8bit

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3202>

(cherry picked from commit f76cbc7901f7d500f5a4f74aedfd29970d1efd00)

Signed-off-by: Michel Dänzer <mdaenzer@redhat.com>

---

 src/util/Makefile.sources |   2 +

 src/util/meson.build      |   1 +

 src/util/os_file.c        | 165 ++++++++++++++++++++++++++++++++++++++

 src/util/os_file.h        |  45 +++++++++++

 4 files changed, 213 insertions(+)

 create mode 100644 src/util/os_file.c

 create mode 100644 src/util/os_file.h

diff --git a/src/util/Makefile.sources b/src/util/Makefile.sources

index b4d23947ab7..02e7a5e598b 100644

--- a/src/util/Makefile.sources

+++ b/src/util/Makefile.sources

@@ -27,6 +27,8 @@ MESA_UTIL_FILES := \

 	mesa-sha1.h \

 	os_time.c \

 	os_time.h \

+	os_file.c \

+	os_file.h \

 	os_misc.c \

 	os_misc.h \

 	u_process.c \

diff --git a/src/util/meson.build b/src/util/meson.build

index 156621aff65..d612e31952d 100644

--- a/src/util/meson.build

+++ b/src/util/meson.build

@@ -51,6 +51,7 @@ files_mesa_util = files(

   'mesa-sha1.h',

   'os_time.c',

   'os_time.h',

+  'os_file.c',

   'os_misc.c',

   'os_misc.h',

   'u_process.c',

diff --git a/src/util/os_file.c b/src/util/os_file.c

new file mode 100644

index 00000000000..b502ff4b0ef

--- /dev/null

+++ b/src/util/os_file.c

@@ -0,0 +1,165 @@

+/*

+ * Copyright 2019 Intel Corporation

+ * SPDX-License-Identifier: MIT

+ */

+

+#include "os_file.h"

+

+#include <errno.h>

+#include <fcntl.h>

+#include <stdlib.h>

+#include <sys/stat.h>

+

+

+#if defined(WIN32)

+#include <io.h>

+#define open _open

+#define fdopen _fdopen

+#define O_CREAT _O_CREAT

+#define O_EXCL _O_EXCL

+#define O_WRONLY _O_WRONLY

+#endif

+

+

+FILE *

+os_file_create_unique(const char *filename, int filemode)

+{

+   int fd = open(filename, O_CREAT | O_EXCL | O_WRONLY, filemode);

+   if (fd == -1)

+      return NULL;

+   return fdopen(fd, "w");

+}

+

+

+#if defined(__linux__)

+

+#include <fcntl.h>

+#include <linux/kcmp.h>

+#include <sys/stat.h>

+#include <sys/syscall.h>

+#include <unistd.h>

+

+

+static ssize_t

+readN(int fd, char *buf, size_t len)

+{

+   int err = -ENODATA;

+   size_t total = 0;

+   do {

+      ssize_t ret = read(fd, buf + total, len - total);

+

+      if (ret < 0)

+         ret = -errno;

+

+      if (ret == -EINTR || ret == -EAGAIN)

+         continue;

+

+      if (ret <= 0) {

+         err = ret;

+         break;

+      }

+

+      total += ret;

+   } while (total != len);

+

+   return total ? (ssize_t)total : err;

+}

+

+char *

+os_read_file(const char *filename)

+{

+   /* Note that this also serves as a slight margin to avoid a 2x grow when

+    * the file is just a few bytes larger when we read it than when we

+    * fstat'ed it.

+    * The string's NULL terminator is also included in here.

+    */

+   size_t len = 64;

+

+   int fd = open(filename, O_RDONLY);

+   if (fd == -1) {

+      /* errno set by open() */

+      return NULL;

+   }

+

+   /* Pre-allocate a buffer at least the size of the file if we can read

+    * that information.

+    */

+   struct stat stat;

+   if (fstat(fd, &stat) == 0)

+      len += stat.st_size;

+

+   char *buf = malloc(len);

+   if (!buf) {

+      close(fd);

+      errno = -ENOMEM;

+      return NULL;

+   }

+

+   ssize_t actually_read;

+   size_t offset = 0, remaining = len - 1;

+   while ((actually_read = readN(fd, buf + offset, remaining)) == (ssize_t)remaining) {

+      char *newbuf = realloc(buf, 2 * len);

+      if (!newbuf) {

+         free(buf);

+         close(fd);

+         errno = -ENOMEM;

+         return NULL;

+      }

+

+      buf = newbuf;

+      len *= 2;

+      offset += actually_read;

+      remaining = len - offset - 1;

+   }

+

+   close(fd);

+

+   if (actually_read > 0)

+      offset += actually_read;

+

+   /* Final resize to actual size */

+   len = offset + 1;

+   char *newbuf = realloc(buf, len);

+   if (!newbuf) {

+      free(buf);

+      errno = -ENOMEM;

+      return NULL;

+   }

+   buf = newbuf;

+

+   buf[offset] = '\0';

+

+   return buf;

+}

+

+bool

+os_same_file_description(int fd1, int fd2)

+{

+   pid_t pid = getpid();

+

+   return syscall(SYS_kcmp, pid, pid, KCMP_FILE, fd1, fd2) == 0;

+}

+

+#else

+

+#include "u_debug.h"

+

+char *

+os_read_file(const char *filename)

+{

+   errno = -ENOSYS;

+   return NULL;

+}

+

+bool

+os_same_file_description(int fd1, int fd2)

+{

+   if (fd1 == fd2)

+      return true;

+

+   debug_warn_once("Can't tell if different file descriptors reference the same"

+                   " file description, false negatives might cause trouble!\n");

+   return false;

+}

+

+#endif

diff --git a/src/util/os_file.h b/src/util/os_file.h

new file mode 100644

index 00000000000..1972beba32b

--- /dev/null

+++ b/src/util/os_file.h

@@ -0,0 +1,45 @@

+/*

+ * Copyright 2019 Intel Corporation

+ * SPDX-License-Identifier: MIT

+ *

+ * File operations helpers

+ */

+

+#ifndef _OS_FILE_H_

+#define _OS_FILE_H_

+

+#include <stdbool.h>

+#include <stdio.h>

+

+#ifdef  __cplusplus

+extern "C" {

+#endif

+

+/*

+ * Create a new file and opens it for writing-only.

+ * If the given filename already exists, nothing is done and NULL is returned.

+ * `errno` gets set to the failure reason; if that is not EEXIST, the caller

+ * might want to do something other than trying again.

+ */

+FILE *

+os_file_create_unique(const char *filename, int filemode);

+

+/*

+ * Read a file.

+ * Returns a char* that the caller must free(), or NULL and sets errno.

+ */

+char *

+os_read_file(const char *filename);

+

+/*

+ * Returns true if the two file descriptors passed in can be determined to

+ * reference the same file description, false otherwise

+ */

+bool

+os_same_file_description(int fd1, int fd2);

+

+#ifdef __cplusplus

+}

+#endif

+

+#endif /* _OS_FILE_H_ */

-- 

2.26.2