[gnome-multi-writer] trivial: Choose a random offset when choosing the block address

[Richard Hughes <rhughes src gnome org>]

commit 33d1730f2b7ceb6aab93f1dd0fe5974a02c7eabf
Author: Richard Hughes <richard hughsie com>
Date:   Wed Jan 28 13:56:45 2015 +0000

    trivial: Choose a random offset when choosing the block address
    
    This allows us to use a random part of the block, but show the correct address
    in the error message.

 src/gmw-probe.c |   16 +++++++++++-----
 1 files changed, 11 insertions(+), 5 deletions(-)
---
diff --git a/src/gmw-probe.c b/src/gmw-probe.c
index fc584cd..22973cc 100644
--- a/src/gmw-probe.c
+++ b/src/gmw-probe.c
@@ -46,6 +46,7 @@ typedef struct {
        gssize                   bytes_read;
        gssize                   bytes_wrote;
        guint64                  address;
+       guint64                  offset;
        gboolean                 valid;
 } GmwProbeBlock;
 
@@ -194,7 +195,8 @@ gmw_probe_device_data_save (GmwProbeDevice *dev,
        for (i = 1; i < 40; i++) {
                item = g_new0 (GmwProbeBlock, 1);
                item->valid = TRUE;
-               item->address = i * ONE_MB * 32;
+               item->offset = g_random_int_range (1, 0xff);
+               item->address = (i * ONE_MB * 32);
                item->data_old = g_new0 (guint8, ONE_BLOCK);
                if (item->address >= dev->disk_size) {
                        gmw_probe_block_free (item);
@@ -202,7 +204,8 @@ gmw_probe_device_data_save (GmwProbeDevice *dev,
                }
                item->data_random = gmw_probe_get_random_data (ONE_BLOCK);
                item->bytes_read = gmw_probe_device_read (dev,
-                                                         item->address,
+                                                         item->address +
+                                                         item->offset,
                                                          item->data_old,
                                                          ONE_BLOCK);
                g_ptr_array_add (dev->data_save, item);
@@ -228,7 +231,8 @@ gmw_probe_device_data_set_dummy (GmwProbeDevice *dev,
        for (i = 0; i < dev->data_save->len; i++) {
                item = g_ptr_array_index (dev->data_save, i);
                item->bytes_wrote = gmw_probe_device_write (dev,
-                                                           item->address,
+                                                           item->address +
+                                                           item->offset,
                                                            item->data_random,
                                                            ONE_BLOCK);
 
@@ -262,7 +266,8 @@ gmw_probe_device_data_verify (GmwProbeDevice *dev,
                 * the address and data in some phantom FAT */
                offset = g_random_int_range (1, 0xff);
                item->bytes_read = gmw_probe_device_read (dev,
-                                                         item->address - offset,
+                                                         item->address +
+                                                         item->offset - offset,
                                                          wbuf2,
                                                          ONE_BLOCK + offset);
                if (item->bytes_read != ONE_BLOCK + offset) {
@@ -308,7 +313,8 @@ gmw_probe_device_data_restore (GmwProbeDevice *dev,
                if (!item->valid)
                        continue;
                item->bytes_wrote = gmw_probe_device_write (dev,
-                                                           item->address,
+                                                           item->address +
+                                                           item->offset,
                                                            item->data_old,
                                                            ONE_BLOCK);
                if (item->bytes_wrote != ONE_BLOCK)