1 files changed, 129 insertions, 0 deletions
diff --git a/libstore/zero.c b/libstore/zero.c
new file mode 100644
index 00000000..4706f418
--- /dev/null
+++ b/libstore/zero.c
@@ -0,0 +1,129 @@
+/* Zero store backend
+
+   Copyright (C) 1995, 1996 Free Software Foundation, Inc.
+
+   Written by Miles Bader <miles@gnu.ai.mit.edu>
+
+   This file is part of the GNU Hurd.
+
+   The GNU Hurd is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2, or (at
+   your option) any later version.
+
+   The GNU Hurd 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
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "store.h"
+
+static error_t
+zero_read (struct store *store,
+	   off_t addr, size_t index, size_t amount, void **buf, size_t *len)
+{
+  if (*len < amount)
+    {
+      error_t err =
+	vm_allocate (mach_task_self (), (vm_address_t *)buf, amount, 1);
+      if (! err)
+	*len = amount;
+      return err;
+    }
+  else
+    {
+      bzero (*buf, amount);
+      *len = amount;
+      return 0;
+    }
+}
+
+static error_t
+zero_write (struct store *store,
+	    off_t addr, size_t index, void *buf, size_t len, size_t *amount)
+{
+  return 0;
+}
+
+/* Modify SOURCE to reflect those runs in RUNS, and return it in STORE.  */
+error_t
+zero_remap (struct store *source,
+	    const struct store_run *runs, size_t num_runs,
+	    struct store **store)
+{
+  /* Because all blocks are the same, a zero store always contains just one
+     run; here we simply count up the number of blocks specified by RUNS, and
+     modify SOURCE's one run to reflect that.  */
+  int i;
+  off_t length = 0, old_length = source->runs[0].length;
+  for (i = 0; i < num_runs; i++)
+    if (runs[i].start < 0 || runs[i].start + runs[i].length >= old_length)
+      return EINVAL;
+    else
+      length += runs[i].length;
+  source->runs[0].length = length;
+  *store = source;
+  return 0;
+}
+
+error_t
+zero_allocate_encoding (const struct store *store, struct store_enc *enc)
+{
+  enc->num_ints += 2;
+  enc->num_offsets += 1;
+  return 0;
+}
+
+error_t
+zero_encode (const struct store *store, struct store_enc *enc)
+{
+  enc->ints[enc->cur_int++] = store->class->id;
+  enc->ints[enc->cur_int++] = store->flags;
+  enc->offsets[enc->cur_offset++] = store->size;
+  return 0;
+}
+
+error_t
+zero_decode (struct store_enc *enc, struct store_class *classes,
+	     struct store **store)
+{
+  off_t size;
+  int type, flags;
+
+  if (enc->cur_int + 2 > enc->num_ints
+      || enc->cur_offset + 1 > enc->num_offsets)
+    return EINVAL;
+
+  type = enc->ints[enc->cur_int++];
+  flags = enc->ints[enc->cur_int++];
+  size = enc->offsets[enc->cur_offset++];
+
+  return store_zero_create (size, flags, store);
+}
+
+static struct store_class
+zero_class =
+{
+  STORAGE_ZERO, "zero", zero_read, zero_write,
+  zero_allocate_encoding, zero_encode, zero_decode,
+  0, 0, 0, 0, zero_remap
+};
+_STORE_STD_CLASS (zero_class);
+
+/* Return a new zero store SIZE bytes long in STORE.  */
+error_t
+store_zero_create (size_t size, int flags, struct store **store)
+{
+  struct store_run run = { 0, size };
+  *store = _make_store (&zero_class, MACH_PORT_NULL, flags, 1, &run, 1, 0);
+  return *store ? 0 : ENOMEM;
+}