fs/yaffs2/yaffs_nameval.c

   1 /*
   2  * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
   3  *
   4  * Copyright (C) 2002-2011 Aleph One Ltd.
   5  *   for Toby Churchill Ltd and Brightstar Engineering
   6  *
   7  * Created by Charles Manning <charles@aleph1.co.uk>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  */
  13
  14 /*
  15  * This simple implementation of a name-value store assumes a small number of
  16 * values and fits into a small finite buffer.
  17  *
  18  * Each attribute is stored as a record:
  19  *  sizeof(int) bytes   record size.
  20  *  yaffs_strnlen+1 bytes name null terminated.
  21  *  nbytes    value.
  22  *  ----------
  23  *  total size  stored in record size
  24  *
  25  * This code has not been tested with unicode yet.
  26  */
  27
  28 #include "yaffs_nameval.h"
  29
  30 #include "yportenv.h"
  31
  32 static int nval_find(const char *xb, int xb_size, const YCHAR *name,
  33                      int *exist_size)
  34 {
  35         int pos = 0;
  36         int size;
  37
  38         memcpy(&size, xb, sizeof(int));
  39         while (size > 0 && (size < xb_size) && (pos + size < xb_size)) {
  40                 if (!yaffs_strncmp((YCHAR *) (xb + pos + sizeof(int)),
  41                                 name, size)) {
  42                         if (exist_size)
  43                                 *exist_size = size;
  44                         return pos;
  45                 }
  46                 pos += size;
  47                 if (pos < xb_size - sizeof(int))
  48                         memcpy(&size, xb + pos, sizeof(int));
  49                 else
  50                         size = 0;
  51         }
  52         if (exist_size)
  53                 *exist_size = 0;
  54         return -ENODATA;
  55 }
  56
  57 static int nval_used(const char *xb, int xb_size)
  58 {
  59         int pos = 0;
  60         int size;
  61
  62         memcpy(&size, xb + pos, sizeof(int));
  63         while (size > 0 && (size < xb_size) && (pos + size < xb_size)) {
  64                 pos += size;
  65                 if (pos < xb_size - sizeof(int))
  66                         memcpy(&size, xb + pos, sizeof(int));
  67                 else
  68                         size = 0;
  69         }
  70         return pos;
  71 }
  72
  73 int nval_del(char *xb, int xb_size, const YCHAR *name)
  74 {
  75         int pos = nval_find(xb, xb_size, name, NULL);
  76         int size;
  77
  78         if (pos < 0 || pos >= xb_size)
  79                 return -ENODATA;
  80
  81         /* Find size, shift rest over this record,
  82          * then zero out the rest of buffer */
  83         memcpy(&size, xb + pos, sizeof(int));
  84         memcpy(xb + pos, xb + pos + size, xb_size - (pos + size));
  85         memset(xb + (xb_size - size), 0, size);
  86         return 0;
  87 }
  88
  89 int nval_set(char *xb, int xb_size, const YCHAR *name, const char *buf,
  90                 int bsize, int flags)
  91 {
  92         int pos;
  93         int namelen = yaffs_strnlen(name, xb_size);
  94         int reclen;
  95         int size_exist = 0;
  96         int space;
  97         int start;
  98
  99         pos = nval_find(xb, xb_size, name, &size_exist);
 100
 101         if (flags & XATTR_CREATE && pos >= 0)
 102                 return -EEXIST;
 103         if (flags & XATTR_REPLACE && pos < 0)
 104                 return -ENODATA;
 105
 106         start = nval_used(xb, xb_size);
 107         space = xb_size - start + size_exist;
 108
 109         reclen = (sizeof(int) + namelen + 1 + bsize);
 110
 111         if (reclen > space)
 112                 return -ENOSPC;
 113
 114         if (pos >= 0) {
 115                 nval_del(xb, xb_size, name);
 116                 start = nval_used(xb, xb_size);
 117         }
 118
 119         pos = start;
 120
 121         memcpy(xb + pos, &reclen, sizeof(int));
 122         pos += sizeof(int);
 123         yaffs_strncpy((YCHAR *) (xb + pos), name, reclen);
 124         pos += (namelen + 1);
 125         memcpy(xb + pos, buf, bsize);
 126         return 0;
 127 }
 128
 129 int nval_get(const char *xb, int xb_size, const YCHAR * name, char *buf,
 130              int bsize)
 131 {
 132         int pos = nval_find(xb, xb_size, name, NULL);
 133         int size;
 134
 135         if (pos >= 0 && pos < xb_size) {
 136
 137                 memcpy(&size, xb + pos, sizeof(int));
 138                 pos += sizeof(int);     /* advance past record length */
 139                 size -= sizeof(int);
 140
 141                 /* Advance over name string */
 142                 while (xb[pos] && size > 0 && pos < xb_size) {
 143                         pos++;
 144                         size--;
 145                 }
 146                 /*Advance over NUL */
 147                 pos++;
 148                 size--;
 149
 150                 /* If bsize is zero then this is a size query.
 151                  * Return the size, but don't copy.
 152                  */
 153                 if (!bsize)
 154                         return size;
 155
 156                 if (size <= bsize) {
 157                         memcpy(buf, xb + pos, size);
 158                         return size;
 159                 }
 160         }
 161         if (pos >= 0)
 162                 return -ERANGE;
 163
 164         return -ENODATA;
 165 }
 166
 167 int nval_list(const char *xb, int xb_size, char *buf, int bsize)
 168 {
 169         int pos = 0;
 170         int size;
 171         int name_len;
 172         int ncopied = 0;
 173         int filled = 0;
 174
 175         memcpy(&size, xb + pos, sizeof(int));
 176         while (size > sizeof(int) &&
 177                 size <= xb_size &&
 178                 (pos + size) < xb_size &&
 179                 !filled) {
 180                 pos += sizeof(int);
 181                 size -= sizeof(int);
 182                 name_len = yaffs_strnlen((YCHAR *) (xb + pos), size);
 183                 if (ncopied + name_len + 1 < bsize) {
 184                         memcpy(buf, xb + pos, name_len * sizeof(YCHAR));
 185                         buf += name_len;
 186                         *buf = '\0';
 187                         buf++;
 188                         if (sizeof(YCHAR) > 1) {
 189                                 *buf = '\0';
 190                                 buf++;
 191                         }
 192                         ncopied += (name_len + 1);
 193                 } else {
 194                         filled = 1;
 195                 }
 196                 pos += size;
 197                 if (pos < xb_size - sizeof(int))
 198                         memcpy(&size, xb + pos, sizeof(int));
 199                 else
 200                         size = 0;
 201         }
 202         return ncopied;
 203 }
 204
 205 int nval_hasvalues(const char *xb, int xb_size)
 206 {
 207         return nval_used(xb, xb_size) > 0;
 208 }