Create SFFS library out of HGFS

This Shared Folders File System library (libsffs) now contains all the
file system logic originally in HGFS. The actual HGFS server code is
now a stub that passes on all the work to libsffs. The libhgfs library
is changed accordingly.

lib/libsffs/write.c

@@ -0,0 +1,164 @@
+/* This file contains file writing system call handlers.
+ *
+ * The entry points into this file are:
+ *   do_write		perform the WRITE file system call
+ *   do_ftrunc		perform the FTRUNC file system call
+ *
+ * Created:
+ *   April 2009 (D.C. van Moolenbroek)
+ */
+
+#include "inc.h"
+
+static int write_file(struct inode *ino, u64_t *posp, size_t *countp,
+	cp_grant_id_t *grantp);
+
+/*===========================================================================*
+ *				write_file				     *
+ *===========================================================================*/
+static int write_file(ino, posp, countp, grantp)
+struct inode *ino;
+u64_t *posp;
+size_t *countp;
+cp_grant_id_t *grantp;
+{
+/* Write data or zeroes to a file, depending on whether a valid pointer to
+ * a data grant was provided.
+ */
+  u64_t pos;
+  size_t count, size;
+  vir_bytes off;
+  char *ptr;
+  int r, chunk;
+
+  assert(!IS_DIR(ino));
+
+  if ((r = get_handle(ino)) != OK)
+	return r;
+
+  pos = *posp;
+  count = *countp;
+
+  assert(count > 0);
+
+  /* Use the buffer from below to eliminate extra copying. */
+  size = sffs_table->t_writebuf(&ptr);
+  off = 0;
+
+  while (count > 0) {
+	chunk = MIN(count, size);
+
+	if (grantp != NULL) {
+		r = sys_safecopyfrom(m_in.m_source, *grantp,
+			off, (vir_bytes) ptr, chunk, D);
+
+		if (r != OK)
+			break;
+	} else {
+		/* Do this every time. We don't know what happens below. */
+		memset(ptr, 0, chunk);
+	}
+
+	if ((r = sffs_table->t_write(ino->i_file, ptr, chunk, pos)) <= 0)
+		break;
+
+	count -= r;
+	off += r;
+	pos = add64u(pos, r);
+  }
+
+  if (r < 0)
+	return r;
+
+  *posp = pos;
+  *countp = off;
+
+  return OK;
+}
+
+/*===========================================================================*
+ *				do_write				     *
+ *===========================================================================*/
+int do_write()
+{
+/* Write data to a file.
+ */
+  struct inode *ino;
+  u64_t pos;
+  size_t count;
+  cp_grant_id_t grant;
+  int r;
+
+  if (state.s_read_only)
+	return EROFS;
+
+  if ((ino = find_inode(m_in.REQ_INODE_NR)) == NULL)
+	return EINVAL;
+
+  if (IS_DIR(ino)) return EISDIR;
+
+  pos = make64(m_in.REQ_SEEK_POS_LO, m_in.REQ_SEEK_POS_HI);
+  count = m_in.REQ_NBYTES;
+  grant = m_in.REQ_GRANT;
+
+  if (count == 0) return EINVAL;
+
+  if ((r = write_file(ino, &pos, &count, &grant)) != OK)
+	return r;
+
+  m_out.RES_SEEK_POS_HI = ex64hi(pos);
+  m_out.RES_SEEK_POS_LO = ex64lo(pos);
+  m_out.RES_NBYTES = count;
+
+  return OK;
+}
+
+/*===========================================================================*
+ *				do_ftrunc				     *
+ *===========================================================================*/
+int do_ftrunc()
+{
+/* Change file size or create file holes.
+ */
+  char path[PATH_MAX];
+  struct inode *ino;
+  struct sffs_attr attr;
+  u64_t start, end, delta;
+  size_t count;
+  int r;
+
+  if (state.s_read_only)
+	return EROFS;
+
+  if ((ino = find_inode(m_in.REQ_INODE_NR)) == NULL)
+	return EINVAL;
+
+  if (IS_DIR(ino)) return EISDIR;
+
+  start = make64(m_in.REQ_TRC_START_LO, m_in.REQ_TRC_START_HI);
+  end = make64(m_in.REQ_TRC_END_LO, m_in.REQ_TRC_END_HI);
+
+  if (cmp64u(end, 0) == 0) {
+	/* Truncate or expand the file. */
+	if ((r = verify_inode(ino, path, NULL)) != OK)
+		return r;
+
+	attr.a_mask = SFFS_ATTR_SIZE;
+	attr.a_size = start;
+
+	r = sffs_table->t_setattr(path, &attr);
+  } else {
+	/* Write zeroes to the file. We can't create holes. */
+	if (cmp64(end, start) <= 0) return EINVAL;
+
+	delta = sub64(end, start);
+
+	if (ex64hi(delta) != 0) return EINVAL;
+
+	count = ex64lo(delta);
+
+	r = write_file(ino, &start, &count, NULL);
+  }
+
+  return r;
+}