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/* Store I/O
Copyright (C) 1995, 96, 97, 98, 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 <string.h>
#include <sys/mman.h>
#include "store.h"
/* Returns in RUN the tail of STORE's run list, who's first run contains
ADDR, and is not a hole, and in RUNS_END a pointer pointing at the end of
the run list. Returns the offset within it at which ADDR occurs. Also
returns BASE, which should be added to offsets from RUNS. */
static inline off_t
store_find_first_run (struct store *store, off_t addr,
struct store_run **run, struct store_run **runs_end,
off_t *base, size_t *index)
{
struct store_run *tail = store->runs, *tail_end = tail + store->num_runs;
off_t wrap_src = store->wrap_src;
if (addr >= wrap_src && addr < store->end)
/* Locate the correct position within a repeating pattern of runs. */
{
*base = addr / store->wrap_dst;
addr %= wrap_src;
}
else
*base = 0;
/* XXX: this isn't going to be very efficient if RUNS is very complex...
But it should do dandy if it's short. For long run lists, we could do a
binary search or something. */
while (tail < tail_end)
{
off_t run_blocks = tail->length;
if (run_blocks > addr)
{
*run = tail;
*runs_end = tail_end;
*index = tail - store->runs;
return addr;
}
/* Not to the right place yet, move on... */
addr -= run_blocks;
tail++;
}
return -1;
}
/* Update RUN, BASE, & INDEX to point to the next elemement in the runs
array. RUNS_END is the point where RUNS will wrap. Returns true if
things are still kosher. */
static inline int
store_next_run (struct store *store, struct store_run *runs_end,
struct store_run **run, off_t *base, size_t *index)
{
(*run)++;
(*index)++;
if (*run == runs_end)
/* Wrap around in a repeating RUNS. */
{
*run = store->runs;
*base += store->wrap_dst;
*index = 0;
return (*base < store->end);
}
else
return 1;
}
#include <assert.h>
/* Write LEN bytes from BUF to STORE at ADDR. Returns the amount written
in AMOUNT. ADDR is in BLOCKS (as defined by STORE->block_size). */
error_t
store_write (struct store *store,
off_t addr, void *buf, size_t len, size_t *amount)
{
error_t err;
size_t index;
off_t base;
struct store_run *run, *runs_end;
int block_shift = store->log2_block_size;
store_write_meth_t write = store->class->write;
if (store->flags & STORE_READONLY)
return EROFS; /* XXX */
assert ((len & (block_shift - 1)) == 0);
addr = store_find_first_run (store, addr, &run, &runs_end, &base, &index);
if (addr < 0)
err = EIO;
else if ((len >> block_shift) <= run->length)
/* The first run has it all... */
err = (*write)(store, base + run->start + addr, index, buf, len, amount);
else
/* ARGH, we've got to split up the write ... */
{
mach_msg_type_number_t try = run->length << block_shift, written;
/* Write the initial bit in the first run. Errors here are returned. */
err = (*write)(store, base + run->start + addr, index, buf, try, &written);
if (!err && written == try)
/* Wrote the first bit successfully, now do the rest. Any errors
will just result in a short write. */
{
buf += written;
len -= written;
while (store_next_run (store, runs_end, &run, &base, &index)
&& run->start >= 0) /* Check for holes. */
/* Ok, we can write in this run, at least a bit. */
{
mach_msg_type_number_t seg_written;
if ((len >> block_shift) <= run->length)
try = len;
else
try = run->length << block_shift;
err = (*write)(store, base + run->start, index, buf, try,
&seg_written);
if (err)
break; /* Ack */
written += seg_written;
if (seg_written < try)
break; /* Didn't use up the run, we're done. */
len -= seg_written;
if (len == 0)
break; /* Nothing left to write! */
buf += seg_written;
}
}
*amount = written;
}
return err;
}
/* Read AMOUNT bytes from STORE at ADDR into BUF & LEN (which follows the
usual mach buffer-return semantics) to STORE at ADDR. ADDR is in BLOCKS
(as defined by STORE->block_size). */
error_t
store_read (struct store *store,
off_t addr, size_t amount, void **buf, size_t *len)
{
size_t index;
off_t base;
struct store_run *run, *runs_end;
int block_shift = store->log2_block_size;
store_read_meth_t read = store->class->read;
addr = store_find_first_run (store, addr, &run, &runs_end, &base, &index);
if (addr < 0 || run->start < 0)
return EIO; /* Reading from a hole. */
assert ((amount & (block_shift - 1)) == 0);
if ((amount >> block_shift) <= run->length)
/* The first run has it all... */
return (*read) (store, base + run->start + addr, index, amount, buf, len);
else
/* ARGH, we've got to split up the read ... This isn't fun. */
{
error_t err;
int all;
/* WHOLE_BUF and WHOLE_BUF_LEN will point to a buff that's large enough
to hold the entire request. This is initially whatever the user
passed in, but we'll change it as necessary. */
void *whole_buf = *buf, *buf_end;
size_t whole_buf_len = *len;
/* Read LEN bytes from the store address ADDR into BUF_END. BUF_END
and AMOUNT are adjusted by the amount actually read. Whether or not
the amount read is the same as what was request is returned in ALL. */
inline error_t seg_read (off_t addr, off_t len, int *all)
{
/* SEG_BUF and SEG_LEN are the buffer for a particular bit of the
whole (within one run). */
void *seg_buf = buf_end;
size_t seg_buf_len = len;
error_t err =
(*read)(store, addr, index, len, &seg_buf, &seg_buf_len);
if (!err)
{
/* If for some bizarre reason, the underlying storage chose not
to use the buffer space we so kindly gave it, bcopy it to
that space. */
if (seg_buf != buf_end)
{
bcopy (seg_buf, buf_end, seg_buf_len);
munmap (seg_buf, seg_buf_len);
}
buf_end += seg_buf_len;
amount -= seg_buf_len;
*all = (seg_buf_len == len);
}
return err;
}
if (whole_buf_len < amount)
/* Not enough room in the user's buffer to hold everything, better
make room. */
{
whole_buf_len = amount;
whole_buf = mmap (0, amount, PROT_READ|PROT_WRITE, MAP_ANON, 0, 0);
if (whole_buf == (void *) -1)
return errno; /* Punt early, there's nothing to clean up. */
}
buf_end = whole_buf;
err = seg_read (base + run->start + addr,
run->length << block_shift, &all);
while (!err && all && amount > 0
&& store_next_run (store, runs_end, &run, &base, &index))
{
if (run->start < 0)
/* A hole! Can't read here. Must stop. */
break;
else
err = seg_read (base + run->start,
(amount >> block_shift) <= run->length
? amount /* This run has the rest. */
: (run->length << block_shift), /* Whole run. */
&all);
}
/* The actual amount read. */
*len = buf_end - whole_buf;
if (*len > 0)
err = 0; /* Return a short read instead of an error. */
/* Deallocate any amount of WHOLE_BUF we didn't use. */
if (whole_buf != *buf)
{
if (err)
munmap (whole_buf, whole_buf_len);
else
{
vm_size_t unused = whole_buf_len - round_page (*len);
if (unused)
munmap (whole_buf + whole_buf_len - unused, unused);
*buf = whole_buf;
}
}
return err;
}
}
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