grub/grub-core/io/bufio.c
2010-05-06 11:34:04 +05:30

205 lines
4.5 KiB
C

/* bufio.c - buffered io access */
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2008 Free Software Foundation, Inc.
*
* GRUB 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 3 of the License, or
* (at your option) any later version.
*
* GRUB 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 GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <grub/err.h>
#include <grub/types.h>
#include <grub/mm.h>
#include <grub/misc.h>
#include <grub/fs.h>
#include <grub/bufio.h>
#define GRUB_BUFIO_DEF_SIZE 8192
#define GRUB_BUFIO_MAX_SIZE 1048576
struct grub_bufio
{
grub_file_t file;
grub_size_t block_size;
grub_size_t buffer_len;
char buffer[0];
};
typedef struct grub_bufio *grub_bufio_t;
static struct grub_fs grub_bufio_fs;
grub_file_t
grub_bufio_open (grub_file_t io, int size)
{
grub_file_t file;
grub_bufio_t bufio = 0;
file = (grub_file_t) grub_malloc (sizeof (*file));
if (! file)
return 0;
if (size == 0)
size = GRUB_BUFIO_DEF_SIZE;
else if (size > GRUB_BUFIO_MAX_SIZE)
size = GRUB_BUFIO_MAX_SIZE;
if ((size < 0) || ((unsigned) size > io->size))
size = ((io->size > GRUB_BUFIO_MAX_SIZE) ? GRUB_BUFIO_MAX_SIZE :
io->size);
bufio = grub_malloc (sizeof (struct grub_bufio) + size);
if (! bufio)
{
grub_free (file);
return 0;
}
bufio->file = io;
bufio->block_size = size;
bufio->buffer_len = 0;
file->device = io->device;
file->offset = 0;
file->size = io->size;
file->data = bufio;
file->read_hook = 0;
file->fs = &grub_bufio_fs;
return file;
}
grub_file_t
grub_buffile_open (const char *name, int size)
{
grub_file_t io, file;
io = grub_file_open (name);
if (! io)
return 0;
file = grub_bufio_open (io, size);
if (! file)
{
grub_file_close (io);
return 0;
}
return file;
}
static grub_ssize_t
grub_bufio_read (grub_file_t file, char *buf, grub_size_t len)
{
grub_size_t res = len;
grub_bufio_t bufio = file->data;
grub_uint32_t pos;
if ((file->offset >= bufio->file->offset) &&
(file->offset < bufio->file->offset + bufio->buffer_len))
{
grub_size_t n;
pos = file->offset - bufio->file->offset;
n = bufio->buffer_len - pos;
if (n > len)
n = len;
grub_memcpy (buf, &bufio->buffer[pos], n);
len -= n;
if (! len)
return res;
buf += n;
bufio->file->offset += bufio->buffer_len;
pos = 0;
}
else
{
bufio->file->offset = grub_divmod64 (file->offset, bufio->block_size,
&pos);
bufio->file->offset *= bufio->block_size;
}
if (pos + len >= bufio->block_size)
{
if (pos)
{
grub_size_t n;
bufio->file->fs->read (bufio->file, bufio->buffer,
bufio->block_size);
if (grub_errno)
return -1;
n = bufio->block_size - pos;
grub_memcpy (buf, &bufio->buffer[pos], n);
len -= n;
buf += n;
bufio->file->offset += bufio->block_size;
pos = 0;
}
while (len >= bufio->block_size)
{
bufio->file->fs->read (bufio->file, buf, bufio->block_size);
if (grub_errno)
return -1;
len -= bufio->block_size;
buf += bufio->block_size;
bufio->file->offset += bufio->block_size;
}
if (! len)
{
bufio->buffer_len = 0;
return res;
}
}
bufio->buffer_len = bufio->file->size - bufio->file->offset;
if (bufio->buffer_len > bufio->block_size)
bufio->buffer_len = bufio->block_size;
bufio->file->fs->read (bufio->file, bufio->buffer, bufio->buffer_len);
if (grub_errno)
return -1;
grub_memcpy (buf, &bufio->buffer[pos], len);
return res;
}
static grub_err_t
grub_bufio_close (grub_file_t file)
{
grub_bufio_t bufio = file->data;
grub_file_close (bufio->file);
grub_free (bufio);
file->device = 0;
return grub_errno;
}
static struct grub_fs grub_bufio_fs =
{
.name = "bufio",
.dir = 0,
.open = 0,
.read = grub_bufio_read,
.close = grub_bufio_close,
.label = 0,
.next = 0
};