Pack seqnum with mark MSB to save 1 byte.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@1092 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/fs/battfs.c b/fs/battfs.c
index 630127f5fad40c38ac58f0015e16de380a1ed99b..8289e91d245ee717f5dd9fd0a49398f4ae355e98 100644 (file)
--- a/fs/battfs.c
+++ b/fs/battfs.c
@@ -53,38 +53,42 @@
  */
 INLINE void battfs_to_disk(struct BattFsPageHeader *hdr, uint8_t *buf)
 {
-       STATIC_ASSERT(BATTFS_HEADER_LEN == 13);
+       STATIC_ASSERT(BATTFS_HEADER_LEN == 12);
        buf[0] = hdr->inode;
 
-       buf[1] = hdr->seq;
+       buf[1] = hdr->fill;
+       buf[2] = hdr->fill >> 8;
 
-       buf[2] = hdr->fill;
-       buf[3] = hdr->fill >> 8;
-
-       buf[4] = hdr->pgoff;
-       buf[5] = hdr->pgoff >> 8;
+       buf[3] = hdr->pgoff;
+       buf[4] = hdr->pgoff >> 8;
 
        /*
         * Mark is at least 1 bit longer than page address.
         * Needed to take care of wraparonds.
         */
-       buf[6] = hdr->mark;
-       buf[7] = hdr->mark >> 8;
-       buf[8] = hdr->mark >> 16;
+       buf[5] = hdr->mark;
+       buf[6] = hdr->mark >> 8;
+
+       /*
+        * First bit used by mark, last 2 bits used by seq.
+        * Since only 2 pages with the same inode and pgoff
+        * can exist at the same time, 2 bit for seq are enough.
+        */
+       buf[7] = ((hdr->mark >> 16) & 0x01) | (hdr->seq << 6);
 
        /*
         * This field must be the before the last one!
         */
-       buf[9] = hdr->fcs_free;
-       buf[10] = hdr->fcs_free >> 8;
+       buf[8] = hdr->fcs_free;
+       buf[9] = hdr->fcs_free >> 8;
 
        /*
         * This field must be the last one!
         * This is needed because if the page is only partially
         * written, we can use this to detect it.
         */
-       buf[11] = hdr->fcs;
-       buf[12] = hdr->fcs >> 8;
+       buf[10] = hdr->fcs;
+       buf[11] = hdr->fcs >> 8;
 }
 
 /**
@@ -93,14 +97,14 @@ INLINE void battfs_to_disk(struct BattFsPageHeader *hdr, uint8_t *buf)
  */
 INLINE void disk_to_battfs(uint8_t *buf, struct BattFsPageHeader *hdr)
 {
-       STATIC_ASSERT(BATTFS_HEADER_LEN == 13);
+       STATIC_ASSERT(BATTFS_HEADER_LEN == 12);
        hdr->inode = buf[0];
-       hdr->seq = buf[1];
-       hdr->fill = buf[3] << 8 | buf[2];
-       hdr->pgoff = buf[5] << 8 | buf[4];
-       hdr->mark = (mark_t)buf[8] << 16 | buf[7] << 8 | buf[6];
-       hdr->fcs_free = buf[10] << 8 | buf[9];
-       hdr->fcs = buf[12] << 8 | buf[11];
+       hdr->fill = buf[2] << 8 | buf[1];
+       hdr->pgoff = buf[4] << 8 | buf[3];
+       hdr->mark = (mark_t)(buf[7] & 0x01) << 16 | buf[6] << 8 | buf[5];
+       hdr->seq = buf[7] >> 6;
+       hdr->fcs_free = buf[9] << 8 | buf[8];
+       hdr->fcs = buf[11] << 8 | buf[10];
 }
 
 /**
@@ -316,7 +320,7 @@ bool battfs_init(struct BattFsSuper *disk)
                                else
                                {
                                        minh = MIN(minh, hdr.mark);
-                                       maxl = MAX(maxl, hdr.mark);
+                                       maxh = MAX(maxh, hdr.mark);
                                }
                        }
                        else
@@ -364,7 +368,7 @@ bool battfs_init(struct BattFsSuper *disk)
        {
                TRACEMSG("No valid marked free block found\n");
                disk->free_start = 0;
-               disk->free_next = -1;
+               disk->free_next = -1; //to be incremented ahead
        }
 
        /* free_next should contain the first usable address */

diff --git a/fs/battfs.h b/fs/battfs.h
index 6558877f838d9ce607db1677aab8563508b72054..9235263e8efb0915c761b4af0a5e6bd7b9e51854 100644 (file)
--- a/fs/battfs.h
+++ b/fs/battfs.h
@@ -92,7 +92,7 @@ typedef struct BattFsPageHeader
  * \see battfs_to_disk
  * \see disk_to_battfs
  */
-#define BATTFS_HEADER_LEN 13
+#define BATTFS_HEADER_LEN 12
 
 /**
  * Marks for valid pages.