libhed/access.h

   1 /* Low-level file accessors */
   2
   3 /* This is a libhed PRIVATE file.
   4  * Do not include outside of libhed. Do not install on the system.
   5  */
   6
   7 /*
   8  * hed - Hexadecimal editor
   9  * Copyright (C) 2012  Petr Tesarik <petr@tesarici.cz>
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of version 2 of the GNU General Public License as
  13  * published by the Free Software Foundation.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  23  */
  24
  25 /*
  26  * Definitions in this file abstract from the low-level file access
  27  * method. There are currently two access methods:
  28  *   read()
  29  *   mmap()
  30  *
  31  * However, there might be more methods in the future, such as
  32  * a BIOS-call based one for making a standalone disk editor
  33  * directly loadable from the boot manager.
  34  */
  35
  36 #ifndef LIBHED__ACCESS_H
  37 #define LIBHED__ACCESS_H
  38
  39 #include "config.h"
  40
  41 #include <assert.h>
  42
  43 /* Prevent polluting linker namespace with internal symbols */
  44 #include "private.h"
  45 #define sys_page_shift internal_name(sys_page_shift)
  46 #define sys_page_size internal_name(sys_page_size)
  47 #define file_access_init internal_name(file_access_init)
  48
  49 #define FILE_BLOCK_MASK         ((signed long)FILE_BLOCK_SIZE-1)
  50 #define FILE_BLOCK_OFF(x)       ((hed_off_t)(x) & FILE_BLOCK_MASK)
  51 #define FILE_BLOCK_ROUND(x)     ((hed_off_t)(x) & ~FILE_BLOCK_MASK)
  52 #define FILE_BLOCK_END(x)       ((hed_off_t)(x) | FILE_BLOCK_MASK)
  53
  54 #if defined(HED_CONFIG_MMAP) || defined(HED_CONFIG_SWAP_MMAP)
  55
  56 #define HED_USES_MMAP   1       /* We use mmap() in some way */
  57
  58 extern unsigned int sys_page_shift;     /* Page size bits */
  59 extern unsigned long sys_page_size;     /* Page size (in bytes) */
  60
  61 #endif
  62
  63 #ifdef HED_CONFIG_MMAP
  64
  65 #include <sys/mman.h>
  66 #include <util/lists.h>
  67 #include "file_priv.h"
  68
  69 #define FILE_BLOCK_SHIFT sys_page_shift
  70 #define FILE_BLOCK_SIZE sys_page_size
  71
  72 /* Space to be allocated for each block's data */
  73 #define FILE_BLOCK_ALLOC        0
  74
  75 struct remap_control {
  76         void *start;            /* start address of mapped region */
  77         void *end;              /* end address of mapped region */
  78 };
  79
  80 static inline void
  81 remap_init(struct remap_control *rc)
  82 {
  83         rc->start = rc->end = NULL;
  84 }
  85
  86 static inline void
  87 remap_finish(struct remap_control *rc)
  88 {
  89         if (rc->start != rc->end)
  90                 munmap(rc->start, rc->end - rc->start);
  91 }
  92
  93 #define remap_compact(rc,cache,preload,n) do { } while(0)
  94
  95 static inline void
  96 remap_add(struct remap_control *rc, void *data)
  97 {
  98         if (data == rc->end)
  99                 rc->end = data + FILE_BLOCK_SIZE;
 100         else if (data + FILE_BLOCK_SIZE == rc->start)
 101                 rc->start = data;
 102         else if (data) {
 103                 remap_finish(rc);
 104                 rc->start = data;
 105                 rc->end = data + FILE_BLOCK_SIZE;
 106         }
 107 }
 108
 109 #define fixup_files internal_name(fixup_files)
 110 extern struct list_head fixup_files;
 111
 112 static inline void
 113 fixup_register(struct file_priv *file)
 114 {
 115         list_add(&file->fixup_list, &fixup_files);
 116 }
 117
 118 static inline void
 119 fixup_deregister(struct file_priv *file)
 120 {
 121         list_del(&file->fixup_list);
 122 }
 123
 124 #else  /* !HED_CONFIG_MMAP */
 125
 126 #include "cache.h"
 127
 128 /* More or less arbitrarily chosen: */
 129 #define FILE_BLOCK_SHIFT        12
 130 #define FILE_BLOCK_SIZE         (1U << FILE_BLOCK_SHIFT)
 131
 132 /* Space to be allocated for each block's data */
 133 #define FILE_BLOCK_ALLOC        FILE_BLOCK_SIZE
 134
 135 struct remap_control { };
 136
 137 #define remap_init(rc)          do {} while(0)
 138 #define remap_finish(rc)        do {} while(0)
 139 #define remap_add(rc,data)      do {} while(0)
 140
 141 static inline void
 142 remap_compact(struct remap_control *rc, struct hed_cache *cache,
 143               struct hed_block_data **preload, int n)
 144 {
 145 #ifdef HED_CONFIG_READAHEAD
 146         cache_compact(cache, preload, n);
 147 #endif
 148 }
 149
 150 #define fixup_register(f)       do {} while(0)
 151 #define fixup_deregister(f)     do {} while(0)
 152
 153 #endif  /* HED_CONFIG_MMAP */
 154
 155 #if HED_USES_MMAP
 156
 157 #include <unistd.h>
 158 #include "util/numbers.h"
 159
 160 #define SWAP_BLOCK_SHIFT sys_page_shift
 161 #define SWAP_BLOCK_SIZE sys_page_size
 162
 163 int file_access_init(void);
 164
 165 #else
 166
 167 #define SWAP_BLOCK_SHIFT FILE_BLOCK_SHIFT
 168 #define SWAP_BLOCK_SIZE FILE_BLOCK_SIZE
 169
 170 static inline int
 171 file_access_init(void)
 172 {
 173         return 0;
 174 }
 175
 176 #endif
 177
 178 #endif  /* LIBHED__ACCESS_H */