diff options
Diffstat (limited to 'remap.c')
| -rw-r--r-- | remap.c | 219 |
1 files changed, 219 insertions, 0 deletions
@@ -0,0 +1,219 @@ +/* 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/>. + * + * Remapping shim + */ + +#include "sysincludes.h" +#include "msdos.h" +#include "mtools.h" +#include "remap.h" + +enum map_type_t { + DATA, + ZERO, + SKIP, + POS +}; + +struct map { + mt_off_t orig; + mt_off_t remapped; + enum map_type_t type; +}; + +typedef struct Remap_t { + struct Stream_t head; + + struct map *map; + int mapSize; + + mt_off_t net_offset; +} Remap_t; + +static enum map_type_t remap(Remap_t *This, mt_off_t *start, size_t *len) { + int i; + for(i=0; i < This->mapSize - 1; i++) + if(*start < This->map[i+1].remapped) { + limitSizeToOffT(len, This->map[i+1].remapped - *start); + break; + } + *start = *start - This->map[i].remapped + This->map[i].orig; + return This->map[i].type; +} + +static ssize_t remap_pread(Stream_t *Stream, char *buf, + mt_off_t start, size_t len) +{ + DeclareThis(Remap_t); + if(remap(This, &start, &len)==DATA) + return PREADS(This->head.Next, buf, start, len); + else { + memset(buf, 0, len); + return (ssize_t) len; + } +} + +static ssize_t remap_pwrite(Stream_t *Stream, char *buf, + mt_off_t start, size_t len) +{ + DeclareThis(Remap_t); + if(remap(This, &start, &len)==DATA) + return PWRITES(This->head.Next, buf, start, len); + else { + unsigned int i; + /* When writing to a "zero" sector, make sure that we + indeed only write zeroes back to there. Helps catch + putting filesystems with parameters unsuitable to + the particular mapping */ + for(i=0; i<len; i++) { + if(buf[i]) { + fprintf(stderr, "Bad data written to unmapped sectors\n"); + errno = EFAULT; + return -1; + } + } + return (ssize_t) len; + } +} + +static int remap_free(Stream_t *Stream) +{ + DeclareThis(Remap_t); + if(This->map) + free(This->map); + return 0; +} + +static Class_t RemapClass = { + 0, + 0, + remap_pread, + remap_pwrite, + 0, /* flush */ + remap_free, /* free */ + set_geom_pass_through, /* set_geom */ + 0, /* get_data */ + 0, /* pre-allocate */ + get_dosConvert_pass_through, /* dos convert */ + 0, /* discard */ +}; + +static int process_map(Remap_t *This, const char *ptr, + int countOnly, char *errmsg) { + mt_off_t orig=0; + mt_off_t remapped=0; + int count=0; + int atEnd=0; + char *eptr; + while(!atEnd) { + mt_off_t len; + enum map_type_t type; + if(*ptr=='\0') { + type=DATA; + atEnd=1; + } else if(!strncmp(ptr, "skip", 4)) { + type=SKIP; + ptr+=4; + } else if(!strncmp(ptr, "zero", 4)) { + type=ZERO; + ptr+=4; + } else if(!strncmp(ptr, "pos", 3)) { + type=POS; + ptr+=3; + } else { + type=DATA; + } + + len=str_to_off_with_end(ptr,&eptr); + ptr=eptr; + switch(*ptr) { + case '\0': + /* End of string */ + break; + case ',': + /* Move on to next item */ + ptr++; + break; + default: + sprintf(errmsg, "Bad number %s\n", ptr); + return -1; + } + + if(type == POS) { + orig = len; + continue; + } + if(type != SKIP) { + if(!countOnly) { + struct map *m = This->map+count; + m->orig = orig; + m->remapped = remapped; + m->type = type; + } + remapped+=len; + count++; + } + if(type != ZERO) { + orig+=len; + } + + } + This->net_offset = orig-remapped; + return count; +} + + +Stream_t *Remap(Stream_t *Next, struct device *dev, char *errmsg) { + Remap_t *This; + int nrItems=0; + const char *map = dev->data_map; + + This = New(Remap_t); + if (!This){ + printOom(); + return 0; + } + memset((void*)This, 0, sizeof(Remap_t)); + init_head(&This->head, &RemapClass, Next); + + /* First count number of items */ + nrItems=process_map(This, map, 1, errmsg); + if(nrItems < 0) { + free(This); + return NULL; + } + + This->map = calloc((size_t)nrItems, sizeof(struct map)); + if(!This->map) { + printOom(); + goto exit_0; + } + + process_map(This, map, 0, errmsg); + + if(adjust_tot_sectors(dev, This->net_offset, errmsg) < 0) + goto exit_1; + + This->mapSize=nrItems; + return &This->head; + exit_1: + free(This->map); + exit_0: + free(This); + printOom(); + return NULL; +} |