diff options
Diffstat (limited to 'grub-core/io/bufio.c')
| -rw-r--r-- | grub-core/io/bufio.c | 214 |
1 files changed, 214 insertions, 0 deletions
diff --git a/grub-core/io/bufio.c b/grub-core/io/bufio.c new file mode 100644 index 0000000..a458c3a --- /dev/null +++ b/grub-core/io/bufio.c @@ -0,0 +1,214 @@ +/* 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 = (file->offset + res + len - 1) & ~((grub_off_t) bufio->block_size - 1); + /* 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 + }; |