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/* 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>
#include <grub/dl.h>
GRUB_MOD_LICENSE ("GPLv3+");
#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;
grub_off_t buffer_at;
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, grub_size_t size)
{
grub_file_t file;
grub_bufio_t bufio = 0;
file = (grub_file_t) grub_zalloc (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 > io->size)
size = ((io->size > GRUB_BUFIO_MAX_SIZE) ? GRUB_BUFIO_MAX_SIZE :
io->size);
/*
* Round up size to power of 2 which the binary math to
* calculate next_buf in grub_bufio_read() requires.
*/
while (size & (size - 1))
size = (size | (size - 1)) + 1;
bufio = grub_zalloc (sizeof (struct grub_bufio) + size);
if (! bufio)
{
grub_free (file);
return 0;
}
bufio->file = io;
bufio->block_size = size;
file->device = io->device;
file->size = io->size;
file->data = bufio;
file->fs = &grub_bufio_fs;
file->not_easily_seekable = io->not_easily_seekable;
return file;
}
grub_file_t
grub_buffile_open (const char *name, enum grub_file_type type, grub_size_t size)
{
grub_file_t io, file;
io = grub_file_open (name, type);
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 = 0;
grub_off_t next_buf;
grub_bufio_t bufio = file->data;
grub_ssize_t really_read;
if (file->size == GRUB_FILE_SIZE_UNKNOWN)
file->size = bufio->file->size;
/* First part: use whatever we already have in the buffer. */
if ((file->offset >= bufio->buffer_at) &&
(file->offset < bufio->buffer_at + bufio->buffer_len))
{
grub_size_t n;
grub_uint64_t pos;
pos = file->offset - bufio->buffer_at;
n = bufio->buffer_len - pos;
if (n > len)
n = len;
grub_memcpy (buf, &bufio->buffer[pos], n);
len -= n;
res += n;
buf += n;
}
if (len == 0)
return res;
/* Need to read some more. */
next_buf = (grub_divmod64 (file->offset + res + len - 1, bufio->block_size, NULL)) * bufio->block_size;
/* Now read between file->offset + res and bufio->buffer_at. */
if (file->offset + res < next_buf)
{
grub_size_t read_now;
read_now = next_buf - (file->offset + res);
grub_file_seek (bufio->file, file->offset + res);
really_read = grub_file_read (bufio->file, buf, read_now);
if (really_read < 0)
return -1;
if (file->size == GRUB_FILE_SIZE_UNKNOWN)
file->size = bufio->file->size;
len -= really_read;
buf += really_read;
res += really_read;
/* Partial read. File ended unexpectedly. Save the last chunk in buffer.
*/
if (really_read != (grub_ssize_t) read_now)
{
bufio->buffer_len = really_read;
if (bufio->buffer_len > bufio->block_size)
bufio->buffer_len = bufio->block_size;
bufio->buffer_at = file->offset + res - bufio->buffer_len;
grub_memcpy (&bufio->buffer[0], buf - bufio->buffer_len,
bufio->buffer_len);
return res;
}
}
/* Read into buffer. */
grub_file_seek (bufio->file, next_buf);
really_read = grub_file_read (bufio->file, bufio->buffer,
bufio->block_size);
if (really_read < 0)
return -1;
bufio->buffer_at = next_buf;
bufio->buffer_len = really_read;
if (file->size == GRUB_FILE_SIZE_UNKNOWN)
file->size = bufio->file->size;
if (len > bufio->buffer_len)
len = bufio->buffer_len;
grub_memcpy (buf, &bufio->buffer[file->offset + res - next_buf], len);
res += 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",
.fs_dir = 0,
.fs_open = 0,
.fs_read = grub_bufio_read,
.fs_close = grub_bufio_close,
.fs_label = 0,
.next = 0
};
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