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/* 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;
}
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