Doc review; fix some quirks.

[bertos.git] / fs / battfs.h

diff --git a/fs/battfs.h b/fs/battfs.h
index ff49eaa89014a554c1978e05eda70bea95c0497c..c155b61ee2e17a11e657cc550930d1267bb06499 100644 (file)
--- a/fs/battfs.h
+++ b/fs/battfs.h
@@ -48,52 +48,77 @@
 typedef uint16_t fill_t;
 typedef fill_t   pgaddr_t;
 typedef uint16_t pgoff_t;
-typedef pgoff_t  mark_t;
+typedef uint32_t mark_t;
+typedef uint8_t  mark_roll_t;
 typedef uint8_t  inode_t;
 typedef uint8_t  seq_t;
 typedef rotating_t fcs_t;
 
 /**
- * BattFS page header.
- * \note fields order is chosen to comply
- * with CPU alignment.
+ * Size required for free block allocation is at least 1 bit more
+ * than page addressing.
+ */
+STATIC_ASSERT(sizeof(mark_t) > sizeof(pgaddr_t));
+
+/**
+ * BattFS page header, used to represent a page
+ * header in memory.
+ * To see how this is stored on disk:
+ * \see battfs_to_disk
+ * \see disk_to_battfs
  */
 typedef struct BattFsPageHeader
 {
        inode_t  inode; ///< File inode (file identifier).
        seq_t    seq;   ///< Page sequence number.
-       mark_t   mark;  ///< Marker used to keep trace of free/used pages.
-       pgoff_t  pgoff; ///< Page offset inside file.
        fill_t   fill;  ///< Filled bytes in page.
-       uint16_t rfu;   ///< Reserved for future use, 0xFFFF for now.
+       pgoff_t  pgoff; ///< Page offset inside file.
+       mark_t   mark;  ///< Marker used to keep trace of free/used pages.
+
+       /**
+        * FCS (Frame Check Sequence) of the page header once the page
+        * as been marked as free.
+        */
+       fcs_t fcs_free;
 
        /**
         * FCS (Frame Check Sequence) of the page header.
-        * \note 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.
         */
        fcs_t fcs;
 } BattFsPageHeader;
 
 /**
- * Mark for valid pages.
+ * Size of the header once saved on disk.
+ * \see battfs_to_disk
+ * \see disk_to_battfs
+ */
+#define BATTFS_HEADER_LEN 12
+
+/**
+ * Marks for valid pages.
  * Simply set to 1 all field bits.
+ * \{
  */
-#define MARK_PAGE_VALID ((1 << (CPU_BITS_PER_CHAR * sizeof(mark_t))) - 1)
+#define MARK_PAGE_VALID ((1 << (CPU_BITS_PER_CHAR * sizeof(pgaddr_t) + 1)) - 1)
+#define FCS_FREE_VALID  ((1 << (CPU_BITS_PER_CHAR * sizeof(fcs_t))) - 1)
+/* \} */
+
 
 /**
- * Max number of files.
+ * Half-size of free page marker.
+ * Used to keep trace of free marker wrap-arounds.
  */
-#define BATTFS_MAX_FILES (1 << (CPU_BITS_PER_CHAR * sizeof(inode_t)))
+#define MARK_HALF_SIZE (1 << (CPU_BITS_PER_CHAR * sizeof(pgaddr_t) + 1))
 
 /**
- * Special inode used to identify free pages.
+ * Maximum page address.
  */
-#define BATTFS_FREE_INODE (BATTFS_MAX_FILES - 1)
+#define MAX_PAGE_ADDR ((1 << (CPU_BITS_PER_CHAR * sizeof(pgaddr_t))) - 1)
 
-/* Ensure structure has no padding added */
-STATIC_ASSERT(sizeof(BattFsPageHeader) == 12);
+/**
+ * Max number of files.
+ */
+#define BATTFS_MAX_FILES (1 << (CPU_BITS_PER_CHAR * sizeof(inode_t)))
 
 /* Fwd decl */
 struct BattFsSuper;
@@ -103,6 +128,11 @@ struct BattFsSuper;
  */
 typedef uint16_t pgcnt_t;
 
+/**
+ * Sentinel used to keep trace of unset pages in disk->page_array.
+ */
+#define PAGE_UNSET_SENTINEL ((1 << (CPU_BITS_PER_CHAR * sizeof(pgcnt_t))) - 1)
+
 /**
  * Type interface for disk init function.
  * \return true if all is ok, false otherwise.
@@ -123,7 +153,7 @@ typedef size_t (*disk_page_read_t) (struct BattFsSuper *d, pgcnt_t page, pgaddr_
  * \a size the lenght to be written.
  * \return the number of bytes written.
  */
-typedef size_t (*disk_page_write_t) (struct BattFsSuper *d, pgcnt_t page, pgaddr_t addr, void *buf, size_t);
+typedef size_t (*disk_page_write_t) (struct BattFsSuper *d, pgcnt_t page, pgaddr_t addr, const void *buf, size_t);
 
 /**
  * Type interface for disk page erase function.
@@ -166,8 +196,17 @@ typedef struct BattFsSuper
         */
        pgcnt_t *page_array;
 
-       mark_t min_free; ///< Lowest sequence number of free page
-       mark_t max_free; ///< Highest sequence number of free page
+    /**
+        * Lowest free page counter.
+        * This is the counter of the first availble free page.
+        */
+       mark_t free_start;
+
+    /**
+        * Highest free page counter.
+        * This value is the next to be used to mark a block as free.
+        */
+       mark_t free_next;
 
        disk_size_t disk_size;   ///< Size of the disk, in bytes (page_count * page_size).
        disk_size_t free_bytes;  ///< Free space on the disk.
@@ -176,5 +215,6 @@ typedef struct BattFsSuper
 } BattFsSuper;
 
 bool battfs_init(struct BattFsSuper *d);
+bool battfs_writeTestBlock(struct BattFsSuper *disk, pgcnt_t page, inode_t inode, seq_t seq, fill_t fill, pgoff_t pgoff, mark_t mark);
 
 #endif /* FS_BATTFS_H */