diff options
Diffstat (limited to 'libstore/zero.c')
| -rw-r--r-- | libstore/zero.c | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/libstore/zero.c b/libstore/zero.c new file mode 100644 index 00000000..55f84a2c --- /dev/null +++ b/libstore/zero.c @@ -0,0 +1,169 @@ +/* Zero store backend + + Copyright (C) 1995, 1996, 1997, 1999 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., 59 Temple Place - Suite 330, Boston, MA 02111, USA. */ + +#include <assert.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <limits.h> +#include <sys/mman.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) + { + *buf = mmap (0, amount, PROT_READ|PROT_WRITE, MAP_ANON, 0, 0); + if (*buf == (void *) -1) + return errno; + *len = amount; + return 0; + } + 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, const struct store_class *const *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 error_t +zero_open (const char *name, int flags, + const struct store_class *const *classes, + struct store **store) +{ + if (name) + { + char *end; + off_t size = strtoul (name, &end, 0); + if (end == name) + return EINVAL; + return store_zero_create (size, flags, store); + } + else + { + off_t max_offs = ~((off_t)1 << (CHAR_BIT * sizeof (off_t) - 1)); + return store_zero_create (max_offs, flags, store); + } +} + +static error_t +zero_validate_name (const char *name, const struct store_class *const *classes) +{ + if (name) + { + char *end; + strtoul (name, &end, 0); + return end == name ? EINVAL : 0; + } + else + return 0; /* `maximum size' */ +} + +static error_t +zero_map (const struct store *store, vm_prot_t prot, mach_port_t *memobj) +{ + *memobj = MACH_PORT_NULL; + return 0; +} + +struct store_class +store_zero_class = +{ + STORAGE_ZERO, "zero", zero_read, zero_write, + zero_allocate_encoding, zero_encode, zero_decode, + 0, 0, 0, 0, zero_remap, zero_open, zero_validate_name, + zero_map +}; + +/* Return a new zero store SIZE bytes long in STORE. */ +error_t +store_zero_create (off_t size, int flags, struct store **store) +{ + struct store_run run = { 0, size }; + return + _store_create (&store_zero_class, MACH_PORT_NULL, + flags | STORE_INNOCUOUS, 1, &run, 1, 0, store); +} |