# Revert 3959f7d to restore ublio support and add autoconf glue.

diff --git README.md README.md
index 60d5c71..81446a6 100644
--- README.md
+++ README.md
@@ -7,6 +7,7 @@ Supported operating systems:
 
 * GNU/Linux
 * Mac OS X 10.5 or later
+* FreeBSD
 * OpenBSD
 
 Most GNU/Linux distributions already have fuse-exfat and exfat-utils in their repositories, so you can just install and use them. The next chapter describes how to compile them from source.
diff --git configure.ac configure.ac
index b45db3f..2bcda4b 100644
--- configure.ac
+++ configure.ac
@@ -31,6 +31,12 @@ AC_PROG_CC_C99
 AC_PROG_RANLIB
 AM_PROG_AR
 AC_SYS_LARGEFILE
+PKG_CHECK_MODULES([UBLIO], [libublio], [
+  CFLAGS="$CFLAGS $UBLIO_CFLAGS"
+  LIBS="$LIBS $UBLIO_LIBS"
+  AC_DEFINE([USE_UBLIO], [1],
+    [Define if block devices are not supported.])
+], [:])
 PKG_CHECK_MODULES([FUSE], [fuse])
 AC_CONFIG_HEADERS([libexfat/config.h])
 AC_CONFIG_FILES([
diff --git libexfat/io.c libexfat/io.c
index 60f28e2..14c0151 100644
--- libexfat/io.c
+++ libexfat/io.c
@@ -37,12 +37,20 @@
 #include <sys/ioctl.h>
 #endif
 #include <sys/mount.h>
+#ifdef USE_UBLIO
+#include <sys/uio.h>
+#include <ublio.h>
+#endif
 
 struct exfat_dev
 {
 	int fd;
 	enum exfat_mode mode;
 	off_t size; /* in bytes */
+#ifdef USE_UBLIO
+	off_t pos;
+	ublio_filehandle_t ufh;
+#endif
 };
 
 static int open_ro(const char* spec)
@@ -74,6 +82,9 @@ struct exfat_dev* exfat_open(const char* spec, enum exfat_mode mode)
 {
 	struct exfat_dev* dev;
 	struct stat stbuf;
+#ifdef USE_UBLIO
+	struct ublio_param up;
+#endif
 
 	dev = malloc(sizeof(struct exfat_dev));
 	if (dev == NULL)
@@ -211,6 +222,24 @@ struct exfat_dev* exfat_open(const char* spec, enum exfat_mode mode)
 		}
 	}
 
+#ifdef USE_UBLIO
+	memset(&up, 0, sizeof(struct ublio_param));
+	up.up_blocksize = 256 * 1024;
+	up.up_items = 64;
+	up.up_grace = 32;
+	up.up_priv = &dev->fd;
+
+	dev->pos = 0;
+	dev->ufh = ublio_open(&up);
+	if (dev->ufh == NULL)
+	{
+		close(dev->fd);
+		free(dev);
+		exfat_error("failed to initialize ublio");
+		return NULL;
+	}
+#endif
+
 	return dev;
 }
 
@@ -218,6 +247,13 @@ int exfat_close(struct exfat_dev* dev)
 {
 	int rc = 0;
 
+#ifdef USE_UBLIO
+	if (ublio_close(dev->ufh) != 0)
+	{
+		exfat_error("failed to close ublio");
+		rc = -EIO;
+	}
+#endif
 	if (close(dev->fd) != 0)
 	{
 		exfat_error("failed to close device: %s", strerror(errno));
@@ -231,6 +267,13 @@ int exfat_fsync(struct exfat_dev* dev)
 {
 	int rc = 0;
 
+#ifdef USE_UBLIO
+	if (ublio_fsync(dev->ufh) != 0)
+	{
+		exfat_error("ublio fsync failed");
+		rc = -EIO;
+	}
+#endif
 	if (fsync(dev->fd) != 0)
 	{
 		exfat_error("fsync failed: %s", strerror(errno));
@@ -251,29 +294,56 @@ off_t exfat_get_size(const struct exfat_dev* dev)
 
 off_t exfat_seek(struct exfat_dev* dev, off_t offset, int whence)
 {
+#ifdef USE_UBLIO
+	/* XXX SEEK_CUR will be handled incorrectly */
+	return dev->pos = lseek(dev->fd, offset, whence);
+#else
 	return lseek(dev->fd, offset, whence);
+#endif
 }
 
 ssize_t exfat_read(struct exfat_dev* dev, void* buffer, size_t size)
 {
+#ifdef USE_UBLIO
+	ssize_t result = ublio_pread(dev->ufh, buffer, size, dev->pos);
+	if (result >= 0)
+		dev->pos += size;
+	return result;
+#else
 	return read(dev->fd, buffer, size);
+#endif
 }
 
 ssize_t exfat_write(struct exfat_dev* dev, const void* buffer, size_t size)
 {
+#ifdef USE_UBLIO
+	ssize_t result = ublio_pwrite(dev->ufh, buffer, size, dev->pos);
+	if (result >= 0)
+		dev->pos += size;
+	return result;
+#else
 	return write(dev->fd, buffer, size);
+#endif
 }
 
 ssize_t exfat_pread(struct exfat_dev* dev, void* buffer, size_t size,
 		off_t offset)
 {
+#ifdef USE_UBLIO
+	return ublio_pread(dev->ufh, buffer, size, offset);
+#else
 	return pread(dev->fd, buffer, size, offset);
+#endif
 }
 
 ssize_t exfat_pwrite(struct exfat_dev* dev, const void* buffer, size_t size,
 		off_t offset)
 {
+#ifdef USE_UBLIO
+	return ublio_pwrite(dev->ufh, buffer, size, offset);
+#else
 	return pwrite(dev->fd, buffer, size, offset);
+#endif
 }
 
 ssize_t exfat_generic_pread(const struct exfat* ef, struct exfat_node* node,