Rework pread and pwrite support so it should actually work.

Add support for pread64 and pwrite64.  Fixup llseek a bit.
 -Erik

1 files changed, 213 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/common/pread_write.c b/libc/sysdeps/linux/common/pread_write.c
new file mode 100644
index 000000000..319de5af1
--- /dev/null
+++ b/libc/sysdeps/linux/common/pread_write.c
@@ -0,0 +1,213 @@
+/* vi: set sw=4 ts=4:
+ *
+ * Copyright (C) 2002 by Erik Andersen <andersen@uclibc.org>
+ * Based in part on the files
+ *		./sysdeps/unix/sysv/linux/pwrite.c,
+ *		./sysdeps/unix/sysv/linux/pread.c, 
+ *		sysdeps/posix/pread.c
+ *		sysdeps/posix/pwrite.c
+ * from GNU libc 2.2.5, but reworked considerably...
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Library General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Library General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <features.h>
+#if defined _FILE_OFFSET_BITS && _FILE_OFFSET_BITS != 64 
+#undef _FILE_OFFSET_BITS
+#define _FILE_OFFSET_BITS   64
+#endif
+#ifndef __USE_LARGEFILE64
+# define __USE_LARGEFILE64      1
+#endif
+/* We absolutely do _NOT_ want interfaces silently
+ * renamed under us or very bad things will happen... */
+#ifdef __USE_FILE_OFFSET64
+# undef __USE_FILE_OFFSET64
+#endif
+
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/syscall.h>
+#define _XOPEN_SOURCE 500
+#include <unistd.h>
+
+#ifdef __NR_pread
+#define __NR___syscall_pread __NR_pread
+static inline _syscall5(ssize_t, __syscall_pread, int, fd, void *, buf, size_t, count, 
+		__off_t, offset_hi, __off_t, offset_lo);
+#endif
+
+#ifdef __NR_pwrite
+#define __NR___syscall_pwrite __NR_pwrite
+static inline _syscall5(ssize_t, __syscall_pwrite, int, fd, const void *, buf, size_t, count, 
+		__off_t, offset_hi, __off_t, offset_lo);
+#endif
+
+
+static ssize_t __fake_pread_write(int fd, void *buf, 
+		size_t count, __off_t offset, int do_pwrite)
+{
+	int save_errno;
+	ssize_t result;
+	off64_t old_offset;
+
+	/* Since we must not change the file pointer preserve the 
+	 * value so that we can restore it later.  */
+	if ((old_offset=lseek64(fd, 0, SEEK_CUR)) == (off64_t) -1)
+		return -1;
+
+	/* Set to wanted position.  */
+	if (lseek (fd, offset, SEEK_SET) == (__off_t) -1)
+		return -1;
+
+	if (do_pwrite==1) {
+		/* Write the data.  */
+		result = write(fd, buf, count);
+	} else {
+		/* Read the data.  */
+		result = read(fd, buf, count);
+	}
+
+	/* Now we have to restore the position.  If this fails we 
+	 * have to return this as an error.  */
+	save_errno = errno;
+	if (lseek (fd, old_offset, SEEK_SET) == (__off_t) -1)
+	{
+		if (result == -1)
+			__set_errno (save_errno);
+		return -1;
+	}
+	__set_errno (save_errno);
+	return(result);
+}
+
+ssize_t __libc_pread(int fd, void *buf, size_t count, __off_t offset)
+{
+#ifndef __NR_pread
+	return(__fake_pread_write(fd, buf, count, offset, 0));
+#else
+	ssize_t result;
+
+	/* First try the syscall.  */
+	result = __syscall_pread(fd, buf, count, __LONG_LONG_PAIR(0, offset));
+
+	/* Bummer.  Syscall failed or is missing.  Fake it */
+	if (result == -1 && errno == ENOSYS) {
+		result = __fake_pread_write(fd, buf, count, offset, 0);
+	}
+#endif
+	return result;
+}
+weak_alias (__libc_pread, pread)
+
+ssize_t __libc_pwrite(int fd, const void *buf, size_t count, __off_t offset)
+{
+#ifndef __NR_pwrite
+	return(__fake_pread_write(fd, buf, count, offset, 1));
+#else
+	ssize_t result;
+
+	/* First try the syscall.  */
+	result = __syscall_pwrite(fd, buf, count, __LONG_LONG_PAIR(0, offset));
+
+	/* Bummer.  Syscall failed or is missing.  Fake it */
+	if (result == -1 && errno == ENOSYS) {
+		result = __fake_pread_write(fd, (void*)buf, count, offset, 1);
+	}
+#endif
+	return result;
+}
+weak_alias (__libc_pwrite, pwrite)
+
+
+
+
+#if defined __UCLIBC_HAVE_LFS__ 
+static ssize_t __fake_pread_write64(int fd, void *buf, 
+		size_t count, off64_t offset, int do_pwrite)
+{
+	int save_errno;
+	ssize_t result;
+	off64_t old_offset;
+
+	/* Since we must not change the file pointer preserve the 
+	 * value so that we can restore it later.  */
+	if ((old_offset=lseek64(fd, 0, SEEK_CUR)) == (off64_t) -1)
+		return -1;
+
+	/* Set to wanted position.  */
+	if (lseek64(fd, offset, SEEK_SET) == (off64_t) -1) 
+		return -1;                               
+
+	if (do_pwrite==1) {
+		/* Write the data.  */
+		result = write(fd, buf, count);
+	} else {
+		/* Read the data.  */
+		result = read(fd, buf, count);
+	}
+
+	/* Now we have to restore the position. */
+	save_errno = errno;
+	if (lseek64 (fd, old_offset, SEEK_SET) == (off64_t) -1) {
+		if (result == -1)
+			__set_errno (save_errno);
+		return -1;
+	}
+	__set_errno (save_errno);
+	return result;
+}
+
+ssize_t __libc_pread64(int fd, void *buf, size_t count, off64_t offset)
+{ 
+#ifndef __NR_pread
+	return(__fake_pread_write64(fd, buf, count, offset, 0));
+#else
+	ssize_t result;
+	/* First try the syscall.  */
+	result = __syscall_pread(fd, buf, count, 
+			__LONG_LONG_PAIR((__off_t) (offset >> 32), (__off_t) (offset & 0xffffffff)));
+
+	/* Bummer.  Syscall failed or is missing.  Fake it */
+	if (result == -1 && errno == ENOSYS) {
+		result = __fake_pread_write64(fd, buf, count, offset, 0); 
+	}
+	return result;
+#endif
+}
+weak_alias (__libc_pread64, pread64)
+
+ssize_t __libc_pwrite64(int fd, const void *buf, size_t count, off64_t offset)
+{ 
+#ifndef __NR_pwrite
+	return(__fake_pread_write64(fd, (void*)buf, count, offset, 1));
+#else
+	ssize_t result;
+
+	/* First try the syscall.  */
+	result = __syscall_pwrite(fd, buf, count, 
+			__LONG_LONG_PAIR((__off_t) (offset >> 32), (__off_t) (offset & 0xffffffff)));
+
+	/* Bummer.  Syscall failed or is missing.  Fake it */
+	if (result == -1 && errno == ENOSYS) {
+		result = __fake_pread_write64(fd, (void*)buf, count, offset, 1);
+	}
+	return result;
+#endif
+}
+weak_alias (__libc_pwrite64, pwrite64)
+
+#endif
+