diff options
Diffstat (limited to 'offset.c')
-rw-r--r-- | offset.c | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/offset.c b/offset.c new file mode 100644 index 0000000..e8be549 --- /dev/null +++ b/offset.c @@ -0,0 +1,90 @@ +/* Copyright 2021 Alain Knaff. + * This file is part of mtools. + * + * Mtools 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. + * + * Mtools 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 Mtools. If not, see <http://www.gnu.org/licenses/>. + * + * filter to support filesystems stored at an offset into their image + */ + +#include "sysincludes.h" +#include "msdos.h" +#include "mtools.h" +#include "offset.h" + +typedef struct Offset_t { + struct Stream_t head; + + mt_off_t offset; +} Offset_t; + +static ssize_t offset_pread(Stream_t *Stream, char *buf, + mt_off_t start, size_t len) +{ + DeclareThis(Offset_t); + return PREADS(This->head.Next, buf, start+This->offset, len); +} + +static ssize_t offset_pwrite(Stream_t *Stream, char *buf, + mt_off_t start, size_t len) +{ + DeclareThis(Offset_t); + return PWRITES(This->head.Next, buf, start+This->offset, len); +} + +static Class_t OffsetClass = { + 0, + 0, + offset_pread, + offset_pwrite, + 0, /* flush */ + 0, /* free */ + set_geom_pass_through, /* set_geom */ + 0, /* get_data */ + 0, /* pre-allocate */ + get_dosConvert_pass_through, /* dos convert */ + 0, /* discard */ +}; + +Stream_t *OpenOffset(Stream_t *Next, struct device *dev, off_t offset, + char *errmsg, mt_off_t *maxSize) { + Offset_t *This; + + This = New(Offset_t); + if (!This){ + printOom(); + return 0; + } + memset((void*)This, 0, sizeof(Offset_t)); + init_head(&This->head, &OffsetClass, Next); + + This->offset = offset; + + if(maxSize) { + if(This->offset > *maxSize) { + if(errmsg) + sprintf(errmsg,"init: Big disks not supported"); + goto exit_0; + } + + *maxSize -= This->offset; + } + + if(adjust_tot_sectors(dev, This->offset, errmsg) < 0) + goto exit_0; + + return &This->head; + exit_0: + Free(This); + return NULL; +} |