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From:   <paulo.alvarez@tse.jus.br>
To:     <linux-ext4@vger.kernel.org>
CC:     Paulo Antonio Alvarez <pauloaalvarez@gmail.com>
Subject: [PATCH 1/3] Add a Windows implementation of the IO manager
Date:   Tue, 22 Dec 2020 15:15:50 -0300
Message-ID: <20201222181552.11267-2-paulo.alvarez@tse.jus.br>
In-Reply-To: <20201222181552.11267-1-paulo.alvarez@tse.jus.br>
References: <20201222181552.11267-1-paulo.alvarez@tse.jus.br>
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From: Paulo Antonio Alvarez <pauloaalvarez@gmail.com>

---
 lib/ext2fs/windows_io.c | 1041 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 1041 insertions(+)
 create mode 100644 lib/ext2fs/windows_io.c

diff --git a/lib/ext2fs/windows_io.c b/lib/ext2fs/windows_io.c
new file mode 100644
index 00000000..68b5571b
--- /dev/null
+++ b/lib/ext2fs/windows_io.c
@@ -0,0 +1,1041 @@
+/*
+ * windows_io.c --- This is the Windows implementation of the I/O manager.
+ *
+ * Implements a one-block write-through cache.
+ *
+ * Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
+ *	2002 by Theodore Ts'o.
+ *
+ * %Begin-Header%
+ * This file may be redistributed under the terms of the GNU Library
+ * General Public License, version 2.
+ * %End-Header%
+ */
+
+#include <windows.h>
+#include <winioctl.h>
+#include <io.h>
+
+#if !defined(__FreeBSD__) && !defined(__NetBSD__) && !defined(__OpenBSD__)
+#define _XOPEN_SOURCE 600
+#define _DARWIN_C_SOURCE
+#define _FILE_OFFSET_BITS 64
+#ifndef _LARGEFILE_SOURCE
+#define _LARGEFILE_SOURCE
+#endif
+#ifndef _LARGEFILE64_SOURCE
+#define _LARGEFILE64_SOURCE
+#endif
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#endif
+
+#include "config.h"
+#include <stdio.h>
+#include <string.h>
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#if HAVE_ERRNO_H
+#include <errno.h>
+#endif
+#include <fcntl.h>
+#include <time.h>
+#if HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+#define PR_GET_DUMPABLE 3
+#if HAVE_SYS_STAT_H
+#include <sys/stat.h>
+#endif
+#include <fcntl.h>
+
+#undef ALIGN_DEBUG
+
+//#define DEBUG
+#ifdef DEBUG
+#define TRACE(...) {\
+		    char __log[256];\
+		    snprintf(__log, sizeof(__log), __VA_ARGS__);\
+		    __log[sizeof(__log)-1] = 0;\
+		    OutputDebugString(__log);\
+		}
+#else
+#define TRACE(...) do { } while (0);
+#endif
+
+#include "ext2_fs.h"
+#include "ext2fs.h"
+#include "ext2fsP.h"
+
+/*
+ * For checking structure magic numbers...
+ */
+
+#define EXT2_CHECK_MAGIC(struct, code) \
+	  if ((struct)->magic != (code)) return (code)
+#define EXT2_CHECK_MAGIC_RETURN(struct, code, ret) \
+	  if ((struct)->magic != (code)) return (ret)
+
+#define EXT2_ET_MAGIC_WINDOWS_IO_CHANNEL  0x10ed
+
+struct windows_cache {
+	char			*buf;
+	unsigned long long	block;
+	int			access_time;
+	unsigned		dirty:1;
+	unsigned		in_use:1;
+};
+
+#define CACHE_SIZE 8
+#define WRITE_DIRECT_SIZE 4	/* Must be smaller than CACHE_SIZE */
+#define READ_DIRECT_SIZE 4	/* Should be smaller than CACHE_SIZE */
+
+struct windows_private_data {
+	int	magic;
+	char	name[MAX_PATH];
+	HANDLE	handle;
+	char	dos_device[MAX_PATH];
+	char	cf_device[MAX_PATH];
+	int	dev;
+	int	flags;
+	int	align;
+	int	access_time;
+	ext2_loff_t offset;
+	struct windows_cache cache[CACHE_SIZE];
+	void	*bounce;
+	struct struct_io_stats io_stats;
+};
+
+#define IS_ALIGNED(n, align) ((((uintptr_t) n) & \
+			       ((uintptr_t) ((align)-1))) == 0)
+
+static int fake_dos_name_for_device(struct windows_private_data *data)
+{
+	if (strncmp(data->name, "\\\\", 2) == 0) {
+		data->dos_device[0] = 0;
+		strcpy(data->cf_device, data->name);
+		return 0;
+	}
+
+	_snprintf(data->dos_device, MAX_PATH, "fakedevice%lu", GetCurrentProcessId());
+
+	if (!DefineDosDevice(DDD_RAW_TARGET_PATH, data->dos_device, data->name))
+		return 1;
+
+	_snprintf(data->cf_device, MAX_PATH, "\\\\.\\%s", data->dos_device);
+	TRACE("e2fsprogs::fake_dos_name_for_device::DefineDosDevice(\"%s\")", data->dos_device);
+
+	return 0;
+}
+
+static void remove_fake_dos_name(struct windows_private_data *data)
+{
+	if (*data->dos_device) {
+		TRACE("e2fsprogs::remove_fake_dos_name::DefineDosDevice(\"%s\")", data->dos_device);
+		DefineDosDevice(DDD_RAW_TARGET_PATH | DDD_EXACT_MATCH_ON_REMOVE | DDD_REMOVE_DEFINITION, data->dos_device, data->name);
+	}
+}
+
+static errcode_t windows_get_stats(io_channel channel, io_stats *stats)
+{
+	errcode_t	retval = 0;
+
+	struct windows_private_data *data;
+
+	EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+	data = (struct windows_private_data *) channel->private_data;
+	EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_WINDOWS_IO_CHANNEL);
+
+	if (stats)
+		*stats = &data->io_stats;
+
+	return retval;
+}
+
+/*
+ * Here are the raw I/O functions
+ */
+static errcode_t raw_read_blk(io_channel channel,
+			      struct windows_private_data *data,
+			      unsigned long long block,
+			      int count, void *bufv)
+{
+	errcode_t	retval;
+	ssize_t	size;
+	ext2_loff_t	location;
+	DWORD		actual = 0;
+	unsigned char	*buf = bufv;
+	ssize_t		really_read = 0;
+
+	size = (count < 0) ? -count : count * channel->block_size;
+	data->io_stats.bytes_read += size;
+	location = ((ext2_loff_t) block * channel->block_size) + data->offset;
+
+	if (data->flags & IO_FLAG_FORCE_BOUNCE) {
+		if (SetFilePointer(data->handle, location, NULL, FILE_BEGIN) == INVALID_SET_FILE_POINTER) {
+			retval = GetLastError();
+			goto error_out;
+		}
+		goto bounce_read;
+	}
+
+	if (SetFilePointer(data->handle, location, NULL, FILE_BEGIN) == INVALID_SET_FILE_POINTER) {
+		retval = GetLastError();
+		goto error_out;
+	}
+	if ((channel->align == 0) || (IS_ALIGNED(buf, channel->align) && IS_ALIGNED(size, channel->align))) {
+		if (!ReadFile(data->handle, buf, size, &actual, NULL)) {
+			retval = GetLastError();
+			goto error_out;
+		}
+		if (actual != size) {
+	short_read:
+		if (actual < 0) {
+			retval = GetLastError();
+			actual = 0;
+		} else
+			retval = EXT2_ET_SHORT_READ;
+		goto error_out;
+		}
+	return 0;
+	}
+
+	/*
+	 * The buffer or size which we're trying to read isn't aligned
+	 * to the O_DIRECT rules, so we need to do this the hard way...
+	 */
+bounce_read:
+	while (size > 0) {
+		if (!ReadFile(data->handle, data->bounce, channel->block_size, &actual, NULL)) {
+			retval = GetLastError();
+			goto error_out;
+		}
+		if (actual != channel->block_size) {
+			actual = really_read;
+			buf -= really_read;
+			size += really_read;
+			goto short_read;
+		}
+		actual = size;
+		if (size > channel->block_size)
+			actual = channel->block_size;
+		memcpy(buf, data->bounce, actual);
+		really_read += actual;
+		size -= actual;
+		buf += actual;
+	}
+	return 0;
+
+error_out:
+	if (actual >= 0 && actual < size)
+		memset((char *) buf+actual, 0, size-actual);
+	if (channel->read_error)
+		retval = (channel->read_error)(channel, block, count, buf,
+					       size, actual, retval);
+	return retval;
+}
+
+static errcode_t raw_write_blk(io_channel channel,
+			       struct windows_private_data *data,
+			       unsigned long long block,
+			       int count, const void *bufv)
+{
+	ssize_t		size;
+	ext2_loff_t	location;
+	DWORD		actual = 0;
+	errcode_t	retval;
+	const unsigned char *buf = bufv;
+
+	if (count == 1)
+		size = channel->block_size;
+	else {
+		if (count < 0)
+			size = -count;
+		else
+			size = count * channel->block_size;
+	}
+	data->io_stats.bytes_written += size;
+
+	location = ((ext2_loff_t) block * channel->block_size) + data->offset;
+
+	if (data->flags & IO_FLAG_FORCE_BOUNCE) {
+		if (SetFilePointer(data->handle, location, NULL, FILE_BEGIN) == INVALID_SET_FILE_POINTER) {
+			retval = GetLastError();
+			goto error_out;
+		}
+	goto bounce_write;
+	}
+
+		if (SetFilePointer(data->handle, location, NULL, FILE_BEGIN) == INVALID_SET_FILE_POINTER) {
+			retval = GetLastError();
+		goto error_out;
+	}
+
+	SetLastError(0);
+
+	if ((channel->align == 0) || (IS_ALIGNED(buf, channel->align) && IS_ALIGNED(size, channel->align))) {
+		if (!WriteFile(data->handle, buf, size, &actual, NULL)) {
+			retval = GetLastError();
+			goto error_out;
+		}
+
+		if (actual != size) {
+		short_write:
+			retval = EXT2_ET_SHORT_WRITE;
+			goto error_out;
+		}
+		return 0;
+	}
+
+	/*
+	 * The buffer or size which we're trying to write isn't aligned
+	 * to the O_DIRECT rules, so we need to do this the hard way...
+	 */
+bounce_write:
+	while (size > 0) {
+		if (size < channel->block_size) {
+			if (!ReadFile(data->handle, data->bounce, channel->block_size, &actual, NULL)) {
+				retval = GetLastError();
+				goto error_out;
+			}
+			if (actual != channel->block_size) {
+				if (actual < 0) {
+					retval = GetLastError();
+					goto error_out;
+				}
+				memset((char *) data->bounce + actual, 0,
+				       channel->block_size - actual);
+			}
+		}
+		actual = size;
+		if (size > channel->block_size)
+			actual = channel->block_size;
+		memcpy(data->bounce, buf, actual);
+		if (SetFilePointer(data->handle, location, NULL, FILE_BEGIN) == INVALID_SET_FILE_POINTER) {
+			retval = GetLastError();
+			goto error_out;
+		}
+		if (!WriteFile(data->handle, data->bounce, channel->block_size, &actual, NULL)) {
+			retval = GetLastError();
+			goto error_out;
+		}
+
+		if (actual != channel->block_size)
+			goto short_write;
+		size -= actual;
+		buf += actual;
+		location += actual;
+	}
+	return 0;
+
+error_out:
+	if (channel->write_error)
+		retval = (channel->write_error)(channel, block, count, buf,
+						size, actual, retval);
+	return retval;
+}
+
+
+/*
+ * Here we implement the cache functions
+ */
+
+/* Allocate the cache buffers */
+static errcode_t alloc_cache(io_channel channel,
+			     struct windows_private_data *data)
+{
+	errcode_t		retval;
+	struct windows_cache	*cache;
+	int			i;
+
+	data->access_time = 0;
+	for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
+		cache->block = 0;
+		cache->access_time = 0;
+		cache->dirty = 0;
+		cache->in_use = 0;
+		if (cache->buf)
+			ext2fs_free_mem(&cache->buf);
+		retval = io_channel_alloc_buf(channel, 0, &cache->buf);
+		if (retval)
+			return retval;
+	}
+	if (channel->align || data->flags & IO_FLAG_FORCE_BOUNCE) {
+		if (data->bounce)
+			ext2fs_free_mem(&data->bounce);
+		retval = io_channel_alloc_buf(channel, 0, &data->bounce);
+	}
+	return retval;
+}
+
+/* Free the cache buffers */
+static void free_cache(struct windows_private_data *data)
+{
+	struct windows_cache    *cache;
+	int			i;
+
+	data->access_time = 0;
+	for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
+		cache->block = 0;
+		cache->access_time = 0;
+		cache->dirty = 0;
+		cache->in_use = 0;
+		if (cache->buf)
+			ext2fs_free_mem(&cache->buf);
+	}
+	if (data->bounce)
+		ext2fs_free_mem(&data->bounce);
+}
+
+#ifndef NO_IO_CACHE
+/*
+ * Try to find a block in the cache.  If the block is not found, and
+ * eldest is a non-zero pointer, then fill in eldest with the cache
+ * entry to that should be reused.
+ */
+static struct windows_cache *find_cached_block(struct windows_private_data *data,
+					    unsigned long long block,
+					    struct windows_cache **eldest)
+{
+	struct windows_cache	*cache, *unused_cache, *oldest_cache;
+	int			i;
+
+	unused_cache = oldest_cache = 0;
+	for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
+		if (!cache->in_use) {
+			if (!unused_cache)
+				unused_cache = cache;
+			continue;
+		}
+		if (cache->block == block) {
+			cache->access_time = ++data->access_time;
+			return cache;
+		}
+		if (!oldest_cache ||
+		   (cache->access_time < oldest_cache->access_time))
+			oldest_cache = cache;
+	}
+	if (eldest)
+		*eldest = (unused_cache) ? unused_cache : oldest_cache;
+	return 0;
+}
+
+/*
+ * Reuse a particular cache entry for another block.
+ */
+static void reuse_cache(io_channel channel, struct windows_private_data *data,
+		 struct windows_cache *cache, unsigned long long block)
+{
+	if (cache->dirty && cache->in_use)
+		raw_write_blk(channel, data, cache->block, 1, cache->buf);
+
+	cache->in_use = 1;
+	cache->dirty = 0;
+	cache->block = block;
+	cache->access_time = ++data->access_time;
+}
+
+/*
+ * Flush all of the blocks in the cache
+ */
+static errcode_t flush_cached_blocks(io_channel channel,
+				     struct windows_private_data *data,
+				     int invalidate)
+{
+	struct windows_cache	*cache;
+	errcode_t	retval, retval2;
+	int			i;
+
+	retval2 = 0;
+	for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
+		if (!cache->in_use)
+			continue;
+
+		if (invalidate)
+			cache->in_use = 0;
+
+		if (!cache->dirty)
+			continue;
+
+		retval = raw_write_blk(channel, data,
+				       cache->block, 1, cache->buf);
+		if (retval)
+			retval2 = retval;
+		else
+			cache->dirty = 0;
+	}
+	return retval2;
+}
+#endif /* NO_IO_CACHE */
+
+static errcode_t windows_open_channel(struct windows_private_data *data,
+				   int flags, io_channel *channel,
+				   io_manager io_mgr)
+{
+	io_channel	io = NULL;
+	errcode_t	retval;
+	ext2fs_struct_stat st;
+
+	retval = ext2fs_get_mem(sizeof(struct struct_io_channel), &io);
+	if (retval)
+		goto cleanup;
+	memset(io, 0, sizeof(struct struct_io_channel));
+	io->magic = EXT2_ET_MAGIC_IO_CHANNEL;
+
+	io->manager = io_mgr;
+	retval = ext2fs_get_mem(strlen(data->name)+1, &io->name);
+	if (retval)
+		goto cleanup;
+
+	strcpy(io->name, data->name);
+	io->private_data = data;
+	io->block_size = 1024;
+	io->read_error = 0;
+	io->write_error = 0;
+	io->refcount = 1;
+
+#if defined(O_DIRECT)
+	if (flags & IO_FLAG_DIRECT_IO)
+		io->align = ext2fs_get_dio_alignment(data->dev);
+#elif defined(F_NOCACHE)
+	if (flags & IO_FLAG_DIRECT_IO)
+		io->align = 4096;
+#endif
+
+	/*
+	 * If the device is really a block device, then set the
+	 * appropriate flag, otherwise we can set DISCARD_ZEROES flag
+	 * because we are going to use punch hole instead of discard
+	 * and if it succeed, subsequent read from sparse area returns
+	 * zero.
+	 */
+	if (ext2fs_fstat(data->dev, &st) == 0) {
+		if (ext2fsP_is_disk_device(st.st_mode))
+			io->flags |= CHANNEL_FLAGS_BLOCK_DEVICE;
+		else
+			io->flags |= CHANNEL_FLAGS_DISCARD_ZEROES;
+	}
+
+	if ((retval = alloc_cache(io, data)))
+		goto cleanup;
+
+#ifdef BLKROGET
+	if (flags & IO_FLAG_RW) {
+		int error;
+		int readonly = 0;
+
+		/* Is the block device actually writable? */
+		error = ioctl(data->dev, BLKROGET, &readonly);
+		if (!error && readonly) {
+			retval = EPERM;
+			goto cleanup;
+		}
+	}
+#endif
+
+	*channel = io;
+	return 0;
+
+cleanup:
+	if (data) {
+		if (data->dev >= 0)
+			close(data->dev);
+		free_cache(data);
+		ext2fs_free_mem(&data);
+	}
+	if (io) {
+		if (io->name) {
+			ext2fs_free_mem(&io->name);
+		}
+		ext2fs_free_mem(&io);
+	}
+	return retval;
+}
+
+static DWORD windows_open_device(struct windows_private_data *data, int open_flags)
+{
+	DWORD ret = 0;
+
+	if (*data->name != '\\')
+		strcpy(data->cf_device, data->name);
+	else if (fake_dos_name_for_device(data))
+		return -1;
+
+	DWORD desired_access = GENERIC_READ | ((open_flags & O_RDWR) ? GENERIC_WRITE : 0);
+	DWORD share_mode = (open_flags & O_EXCL) ? 0 : FILE_SHARE_READ | ((open_flags & O_RDWR) ? FILE_SHARE_WRITE : 0);
+	DWORD flags_and_attributes =
+#if defined(O_DIRECT)
+	(open_flags & O_DIRECT) ? (FILE_FLAG_NO_BUFFERING | FILE_FLAG_WRITE_THROUGH) : FILE_ATTRIBUTE_NORMAL;
+#else
+	FILE_FLAG_NO_BUFFERING | FILE_FLAG_WRITE_THROUGH;
+#endif
+
+	data->handle = CreateFile(data->cf_device, desired_access, share_mode, NULL, OPEN_EXISTING,
+				  flags_and_attributes, NULL);
+
+	if (data->handle == INVALID_HANDLE_VALUE) {
+		ret = GetLastError();
+		goto invalid_handle;
+	}
+
+	TRACE("e2fsprogs::windows_open_device::CreateFile(\"%s\") = %p", data->cf_device, data->handle);
+
+	data->dev = _open_osfhandle((intptr_t)data->handle, 0);
+	if (data->dev < 0) {
+		ret = GetLastError() ? GetLastError() : 9999;
+		goto osfhandle_error;
+	}
+
+	TRACE("e2fsprogs::windows_open_device::_open_osfhandle(%p) = %d", data->handle, data->dev);
+
+	return 0;
+
+osfhandle_error:
+	TRACE("e2fsprogs::windows_open_device::CloseHandle(%p)", data->handle);
+	CloseHandle(data->handle);
+invalid_handle:
+	remove_fake_dos_name(data);
+	TRACE("e2fsprogs::windows_open_device() = %lu, errno = %d", ret, errno);
+	return ret;
+}
+
+static struct windows_private_data *init_private_data(const char *name, int flags)
+{
+	struct windows_private_data *data = NULL;
+
+	if (ext2fs_get_mem(sizeof(struct windows_private_data), &data))
+		return NULL;
+
+	memset(data, 0, sizeof(struct windows_private_data));
+	strncpy(data->name, name, sizeof(data->name));
+	data->magic = EXT2_ET_MAGIC_WINDOWS_IO_CHANNEL;
+	data->io_stats.num_fields = 2;
+	data->flags = flags;
+	data->handle = INVALID_HANDLE_VALUE;
+
+	return data;
+}
+
+static errcode_t windows_open(const char *name, int flags, io_channel *channel)
+{
+	int fd = -1;
+	int open_flags;
+	struct windows_private_data *data;
+
+	if (name == 0)
+		return EXT2_ET_BAD_DEVICE_NAME;
+
+	data = init_private_data(name, flags);
+	if (!data)
+		return EXT2_ET_NO_MEMORY;
+
+	open_flags = (flags & IO_FLAG_RW) ? O_RDWR : O_RDONLY;
+	if (flags & IO_FLAG_EXCLUSIVE)
+		open_flags |= O_EXCL;
+#if defined(O_DIRECT)
+	if (flags & IO_FLAG_DIRECT_IO)
+		open_flags |= O_DIRECT;
+#endif
+
+	if (windows_open_device(data, open_flags)) {
+		ext2fs_free_mem(&data);
+		return EXT2_ET_BAD_DEVICE_NAME;
+	}
+
+#if defined(F_NOCACHE) && !defined(IO_DIRECT)
+	if (flags & IO_FLAG_DIRECT_IO) {
+		if (fcntl(fd, F_NOCACHE, 1) < 0)
+			return errno;
+	}
+#endif
+	return windows_open_channel(data, flags, channel, windows_io_manager);
+}
+
+static errcode_t windows_close(io_channel channel)
+{
+	struct windows_private_data *data;
+	errcode_t	retval = 0;
+
+	EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+	data = (struct windows_private_data *) channel->private_data;
+	EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_WINDOWS_IO_CHANNEL);
+
+	if (--channel->refcount > 0)
+		return 0;
+
+#ifndef NO_IO_CACHE
+	retval = flush_cached_blocks(channel, data, 0);
+#endif
+
+	remove_fake_dos_name(data);
+
+	if (_close(data->dev) != 0)
+		retval = errno;
+
+	TRACE("e2fsprogs::windows_close::_close(%d)", data->dev);
+
+	free_cache(data);
+
+	ext2fs_free_mem(&channel->private_data);
+	if (channel->name)
+		ext2fs_free_mem(&channel->name);
+	ext2fs_free_mem(&channel);
+	return retval;
+}
+
+static errcode_t windows_set_blksize(io_channel channel, int blksize)
+{
+	struct windows_private_data *data;
+	errcode_t		retval;
+
+	EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+	data = (struct windows_private_data *) channel->private_data;
+	EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_WINDOWS_IO_CHANNEL);
+
+	if (channel->block_size != blksize) {
+#ifndef NO_IO_CACHE
+		if ((retval = flush_cached_blocks(channel, data, 0)))
+			return retval;
+#endif
+
+		channel->block_size = blksize;
+		free_cache(data);
+		if ((retval = alloc_cache(channel, data)))
+			return retval;
+	}
+	return 0;
+}
+
+static errcode_t windows_read_blk64(io_channel channel, unsigned long long block, int count, void *buf)
+{
+	struct windows_private_data *data;
+	struct windows_cache *cache, *reuse[READ_DIRECT_SIZE];
+	errcode_t	retval;
+	char		*cp;
+	int		i, j;
+
+	EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+	data = (struct windows_private_data *) channel->private_data;
+	EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_WINDOWS_IO_CHANNEL);
+
+#ifdef NO_IO_CACHE
+	return raw_read_blk(channel, data, block, count, buf);
+#else
+	/*
+	 * If we're doing an odd-sized read or a very large read,
+	 * flush out the cache and then do a direct read.
+	 */
+	if (count < 0 || count > WRITE_DIRECT_SIZE) {
+		if ((retval = flush_cached_blocks(channel, data, 0)))
+			return retval;
+		return raw_read_blk(channel, data, block, count, buf);
+	}
+
+	cp = buf;
+	while (count > 0) {
+		/* If it's in the cache, use it! */
+		if ((cache = find_cached_block(data, block, &reuse[0]))) {
+#ifdef DEBUG
+			printf("Using cached block %lu\n", block);
+#endif
+			memcpy(cp, cache->buf, channel->block_size);
+			count--;
+			block++;
+			cp += channel->block_size;
+			continue;
+		}
+		if (count == 1) {
+			/*
+			 * Special case where we read directly into the
+			 * cache buffer; important in the O_DIRECT case
+			 */
+			cache = reuse[0];
+			reuse_cache(channel, data, cache, block);
+			if ((retval = raw_read_blk(channel, data, block, 1,
+						   cache->buf))) {
+				cache->in_use = 0;
+				return retval;
+			}
+			memcpy(cp, cache->buf, channel->block_size);
+			return 0;
+		}
+
+		/*
+		 * Find the number of uncached blocks so we can do a
+		 * single read request
+		 */
+		for (i=1; i < count; i++)
+			if (find_cached_block(data, block+i, &reuse[i]))
+				break;
+#ifdef DEBUG
+		printf("Reading %d blocks starting at %lu\n", i, block);
+#endif
+		if ((retval = raw_read_blk(channel, data, block, i, cp)))
+			return retval;
+
+		/* Save the results in the cache */
+		for (j=0; j < i; j++) {
+			count--;
+			cache = reuse[j];
+			reuse_cache(channel, data, cache, block++);
+			memcpy(cache->buf, cp, channel->block_size);
+			cp += channel->block_size;
+		}
+	}
+	return 0;
+#endif /* NO_IO_CACHE */
+}
+
+static errcode_t windows_read_blk(io_channel channel, unsigned long block,
+			       int count, void *buf)
+{
+	return windows_read_blk64(channel, block, count, buf);
+}
+
+static errcode_t windows_write_blk64(io_channel channel,
+				unsigned long long block,
+				int count, const void *buf)
+{
+	struct windows_private_data *data;
+	struct windows_cache *cache, *reuse;
+	errcode_t	retval = 0;
+	const char	*cp;
+	int		writethrough;
+
+	EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+	data = (struct windows_private_data *) channel->private_data;
+	EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_WINDOWS_IO_CHANNEL);
+
+#ifdef NO_IO_CACHE
+	return raw_write_blk(channel, data, block, count, buf);
+#else
+	/*
+	 * If we're doing an odd-sized write or a very large write,
+	 * flush out the cache completely and then do a direct write.
+	 */
+	if (count < 0 || count > WRITE_DIRECT_SIZE) {
+		if ((retval = flush_cached_blocks(channel, data, 1)))
+			return retval;
+		return raw_write_blk(channel, data, block, count, buf);
+	}
+
+	/*
+	 * For a moderate-sized multi-block write, first force a write
+	 * if we're in write-through cache mode, and then fill the
+	 * cache with the blocks.
+	 */
+	writethrough = channel->flags & CHANNEL_FLAGS_WRITETHROUGH;
+	if (writethrough)
+		retval = raw_write_blk(channel, data, block, count, buf);
+
+	cp = buf;
+	while (count > 0) {
+		cache = find_cached_block(data, block, &reuse);
+		if (!cache) {
+			cache = reuse;
+			reuse_cache(channel, data, cache, block);
+		}
+		if (cache->buf != cp)
+			memcpy(cache->buf, cp, channel->block_size);
+		cache->dirty = !writethrough;
+		count--;
+		block++;
+		cp += channel->block_size;
+	}
+	return retval;
+#endif /* NO_IO_CACHE */
+}
+
+static errcode_t windows_cache_readahead(io_channel channel,
+				      unsigned long long block,
+				      unsigned long long count)
+{
+	return EXT2_ET_OP_NOT_SUPPORTED;
+}
+
+static errcode_t windows_write_blk(io_channel channel, unsigned long block,
+				int count, const void *buf)
+{
+	return windows_write_blk64(channel, block, count, buf);
+}
+
+static errcode_t windows_write_byte(io_channel channel, unsigned long offset,
+				 int size, const void *buf)
+{
+	return EXT2_ET_UNIMPLEMENTED;
+}
+
+HANDLE windows_get_handle(io_channel channel)
+{
+	struct windows_private_data *data;
+
+	EXT2_CHECK_MAGIC_RETURN(channel, EXT2_ET_MAGIC_IO_CHANNEL, INVALID_HANDLE_VALUE);
+	data = (struct windows_private_data *) channel->private_data;
+	EXT2_CHECK_MAGIC_RETURN(data, EXT2_ET_MAGIC_WINDOWS_IO_CHANNEL, INVALID_HANDLE_VALUE);
+
+	return data->handle;
+}
+
+/*
+ * Flush data buffers to disk.
+ */
+static errcode_t windows_flush(io_channel channel)
+{
+	struct windows_private_data *data;
+	errcode_t retval = 0;
+
+	EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+	data = (struct windows_private_data *) channel->private_data;
+	EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_WINDOWS_IO_CHANNEL);
+
+#ifndef NO_IO_CACHE
+	retval = flush_cached_blocks(channel, data, 0);
+#endif
+
+	return retval;
+}
+
+static errcode_t windows_set_option(io_channel channel, const char *option,
+				 const char *arg)
+{
+	struct windows_private_data *data;
+	unsigned long long tmp;
+	char *end;
+
+	EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+	data = (struct windows_private_data *) channel->private_data;
+	EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_WINDOWS_IO_CHANNEL);
+
+	if (!strcmp(option, "offset")) {
+		if (!arg)
+			return EXT2_ET_INVALID_ARGUMENT;
+
+		tmp = strtoull(arg, &end, 0);
+		if (*end)
+			return EXT2_ET_INVALID_ARGUMENT;
+		data->offset = tmp;
+		if (data->offset < 0)
+			return EXT2_ET_INVALID_ARGUMENT;
+		return 0;
+	}
+	return EXT2_ET_INVALID_ARGUMENT;
+}
+
+static errcode_t windows_discard(io_channel channel, unsigned long long block,
+				 unsigned long long count)
+{
+	TRACE("e2fsprogs::windows_discard::EXT2_ET_UNIMPLEMENTED");
+	return EXT2_ET_UNIMPLEMENTED;
+}
+
+/* parameters might not be used if OS doesn't support zeroout */
+#if __GNUC_PREREQ (4, 6)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+#endif
+static errcode_t windows_zeroout(io_channel channel, unsigned long long block,
+			      unsigned long long count)
+{
+	struct windows_private_data *data;
+	int		ret;
+
+	EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+	data = (struct windows_private_data *) channel->private_data;
+	EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_WINDOWS_IO_CHANNEL);
+
+	if (channel->flags & CHANNEL_FLAGS_BLOCK_DEVICE) {
+		/* Not implemented until the BLKZEROOUT mess is fixed */
+		goto unimplemented;
+	} else {
+		/* Regular file, try to use truncate/punch/zero. */
+		struct stat statbuf;
+
+		if (count == 0)
+			return 0;
+		/*
+		 * If we're trying to zero a range past the end of the file,
+		 * extend the file size, then truncate everything.
+		 */
+		ret = fstat(data->dev, &statbuf);
+		if (ret)
+			goto err;
+		if ((unsigned long long) statbuf.st_size <
+			(block + count) * channel->block_size + data->offset) {
+			ret = ftruncate(data->dev,
+					(block + count) * channel->block_size + data->offset);
+			if (ret)
+				goto err;
+		}
+		goto unimplemented;
+	}
+err:
+	if (ret < 0) {
+		if (errno == EOPNOTSUPP)
+			goto unimplemented;
+		return errno;
+	}
+	return 0;
+unimplemented:
+	return EXT2_ET_UNIMPLEMENTED;
+}
+
+int ext2fs_open_file(const char *pathname, int flags, mode_t mode)
+{
+	flags |= O_BINARY;
+
+	if (mode)
+#if defined(HAVE_OPEN64) && !defined(__OSX_AVAILABLE_BUT_DEPRECATED)
+		return open64(pathname, flags, mode);
+	else
+		return open64(pathname, flags);
+#else
+		return open(pathname, flags, mode);
+	else
+		return open(pathname, flags);
+#endif
+}
+
+int ext2fs_stat(const char *path, ext2fs_struct_stat *buf)
+{
+#if defined(HAVE_FSTAT64) && !defined(__OSX_AVAILABLE_BUT_DEPRECATED)
+	return stat64(path, buf);
+#else
+	return stat(path, buf);
+#endif
+}
+
+int ext2fs_fstat(int fd, ext2fs_struct_stat *buf)
+{
+#if defined(HAVE_FSTAT64) && !defined(__OSX_AVAILABLE_BUT_DEPRECATED)
+	return fstat64(fd, buf);
+#else
+	return fstat(fd, buf);
+#endif
+}
+
+#if __GNUC_PREREQ (4, 6)
+#pragma GCC diagnostic pop
+#endif
+
+static struct struct_io_manager struct_windows_manager = {
+	.magic		= EXT2_ET_MAGIC_IO_MANAGER,
+	.name		= "Windows I/O Manager",
+	.open		= windows_open,
+	.close		= windows_close,
+	.set_blksize	= windows_set_blksize,
+	.read_blk	= windows_read_blk,
+	.write_blk	= windows_write_blk,
+	.flush		= windows_flush,
+	.write_byte	= windows_write_byte,
+	.set_option	= windows_set_option,
+	.get_stats	= windows_get_stats,
+	.read_blk64	= windows_read_blk64,
+	.write_blk64	= windows_write_blk64,
+	.discard	= windows_discard,
+	.cache_readahead	= windows_cache_readahead,
+	.zeroout	= windows_zeroout,
+};
+
+io_manager windows_io_manager = &struct_windows_manager;
-- 
2.17.1