minix/lib/libsffs/write.c

   1 /* This file contains file writing system call handlers.
   2  *
   3  * The entry points into this file are:
   4  *   do_write           perform the WRITE file system call
   5  *   do_trunc           perform the TRUNC file system call
   6  *
   7  * Created:
   8  *   April 2009 (D.C. van Moolenbroek)
   9  */
  10
  11 #include "inc.h"
  12
  13 /*===========================================================================*
  14  *                              write_file                                   *
  15  *===========================================================================*/
  16 static ssize_t write_file(struct inode *ino, off_t pos, size_t count,
  17         struct fsdriver_data *data)
  18 {
  19 /* Write data or zeroes to a file, depending on whether a valid pointer to
  20  * a data grant was provided.
  21  */
  22   size_t size, off, chunk;
  23   char *ptr;
  24   int r;
  25
  26   if (pos < 0)
  27         return EINVAL;
  28
  29   assert(!IS_DIR(ino));
  30
  31   if ((r = get_handle(ino)) != OK)
  32         return r;
  33
  34   assert(count > 0);
  35
  36   /* Use the buffer from below to eliminate extra copying. */
  37   size = sffs_table->t_writebuf(&ptr);
  38   off = 0;
  39
  40   while (count > 0) {
  41         chunk = MIN(count, size);
  42
  43         if (data != NULL) {
  44                 if ((r = fsdriver_copyin(data, off, ptr, chunk)) != OK)
  45                         break;
  46         } else {
  47                 /* Do this every time. We don't know what happens below. */
  48                 memset(ptr, 0, chunk);
  49         }
  50
  51         if ((r = sffs_table->t_write(ino->i_file, ptr, chunk, pos)) <= 0)
  52                 break;
  53
  54         count -= r;
  55         off += r;
  56         pos += r;
  57   }
  58
  59   if (r < 0)
  60         return r;
  61
  62   return off;
  63 }
  64
  65 /*===========================================================================*
  66  *                              do_write                                     *
  67  *===========================================================================*/
  68 ssize_t do_write(ino_t ino_nr, struct fsdriver_data *data, size_t count,
  69         off_t pos, int call)
  70 {
  71 /* Write data to a file.
  72  */
  73   struct inode *ino;
  74
  75   if (read_only)
  76         return EROFS;
  77
  78   if ((ino = find_inode(ino_nr)) == NULL)
  79         return EINVAL;
  80
  81   if (IS_DIR(ino)) return EISDIR;
  82
  83   if (count == 0) return 0;
  84
  85   return write_file(ino, pos, count, data);
  86 }
  87
  88 /*===========================================================================*
  89  *                              do_trunc                                     *
  90  *===========================================================================*/
  91 int do_trunc(ino_t ino_nr, off_t start, off_t end)
  92 {
  93 /* Change file size or create file holes.
  94  */
  95   char path[PATH_MAX];
  96   struct inode *ino;
  97   struct sffs_attr attr;
  98   uint64_t delta;
  99   ssize_t r;
 100
 101   if (read_only)
 102         return EROFS;
 103
 104   if ((ino = find_inode(ino_nr)) == NULL)
 105         return EINVAL;
 106
 107   if (IS_DIR(ino)) return EISDIR;
 108
 109   if (end == 0) {
 110         /* Truncate or expand the file. */
 111         if ((r = verify_inode(ino, path, NULL)) != OK)
 112                 return r;
 113
 114         attr.a_mask = SFFS_ATTR_SIZE;
 115         attr.a_size = start;
 116
 117         r = sffs_table->t_setattr(path, &attr);
 118   } else {
 119         /* Write zeroes to the file. We can't create holes. */
 120         if (end <= start) return EINVAL;
 121
 122         delta = (uint64_t)end - (uint64_t)start;
 123
 124         if (delta > SSIZE_MAX) return EINVAL;
 125
 126         if ((r = write_file(ino, start, (size_t)delta, NULL)) >= 0)
 127                 r = OK;
 128   }
 129
 130   return r;
 131 }