X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Ffilesys%2Ffilehdr.c;h=1f35946479070e15884f839dfd3c58cbb097c94f;hb=97dcefb4742e13df9eb22c3aa00bb802bdc55c60;hp=aad11e564c2ad15199b639c7827f8b70ecc04256;hpb=621963e2a383d53b2c5eca627102625421b46545;p=pintos-anon

diff --git a/src/filesys/filehdr.c b/src/filesys/filehdr.c
index aad11e5..1f35946 100644
--- a/src/filesys/filehdr.c
+++ b/src/filesys/filehdr.c
@@ -5,6 +5,14 @@
 #include "filesys.h"
 #include "lib.h"
 
+/* Allocates sectors from bitmap B for the content of a file
+   whose size is LENGTH bytes, and returns a new `struct filehdr'
+   properly initialized for the file.
+   It is the caller's responsible to allocate a sector for the
+   file header itself, and to write the file header and bitmap
+   to disk.
+   If memory or disk allocation fails, returns a null pointer,
+   leaving bitmap B is unchanged. */
 struct filehdr *
 filehdr_allocate (struct bitmap *b, off_t length) 
 {
@@ -26,6 +34,7 @@ filehdr_allocate (struct bitmap *b, off_t length)
       if (sector == BITMAP_ERROR)
         {
           filehdr_deallocate (h, b);
+          free (h);
           return NULL;
         }
       h->sectors[h->sector_cnt++] = sector;
@@ -34,6 +43,8 @@ filehdr_allocate (struct bitmap *b, off_t length)
   return h;
 }
 
+/* Marks the sectors for H's content as free in bitmap B.
+   Neither H's own disk sector nor its memory are freed. */
 void
 filehdr_deallocate (struct filehdr *h, struct bitmap *b) 
 {
@@ -46,8 +57,11 @@ filehdr_deallocate (struct filehdr *h, struct bitmap *b)
     bitmap_reset (b, h->sectors[i]);
 }
 
+/* Reads a file header from FILEHDR_SECTOR
+   and returns a new `struct filehdr' that contains it.
+   Returns a null pointer fi memory allocation fails. */
 struct filehdr *
-filehdr_read (disk_sector_no filehdr_sector) 
+filehdr_read (disk_sector_t filehdr_sector) 
 {
   struct filehdr *h = calloc (1, sizeof *h);
   if (h == NULL)
@@ -59,21 +73,28 @@ filehdr_read (disk_sector_no filehdr_sector)
   return h;
 }
 
+/* Writes H to disk in sector FILEHDR_SECTOR. */
 void
-filehdr_write (const struct filehdr *h, disk_sector_no filehdr_sector) 
+filehdr_write (const struct filehdr *h, disk_sector_t filehdr_sector) 
 {
   ASSERT (h != NULL);
   ASSERT (sizeof *h == DISK_SECTOR_SIZE);
   disk_write (filesys_disk, filehdr_sector, h);
 }
 
+/* Frees the memory (but not the on-disk sector) associated with
+   H. */
 void
 filehdr_destroy (struct filehdr *h) 
 {
   free (h);
 }
 
-disk_sector_no
+/* Returns the disk sector that contains byte offset POS within
+   the file with header H.
+   Returns -1 if H does not contain data for a byte at offset
+   POS. */
+disk_sector_t
 filehdr_byte_to_sector (const struct filehdr *h, off_t pos) 
 {
   size_t idx;
@@ -81,9 +102,10 @@ filehdr_byte_to_sector (const struct filehdr *h, off_t pos)
   ASSERT (h != NULL);
 
   idx = pos / DISK_SECTOR_SIZE;
-  return idx < h->sector_cnt ? h->sectors[idx] : (disk_sector_no) -1;
+  return idx < h->sector_cnt ? h->sectors[idx] : (disk_sector_t) -1;
 }
 
+/* Returns the length, in bytes, of the file with header H, */
 off_t
 filehdr_length (const struct filehdr *h)
 {
@@ -91,4 +113,22 @@ filehdr_length (const struct filehdr *h)
   return h->length;
 }
 
-void filehdr_print (const struct filehdr *);
+/* Prints a representation of H to the system console. */
+void
+filehdr_print (const struct filehdr *h) 
+{
+  size_t i;
+  
+  printk ("File header: %jd bytes, %zd sectors (",
+          (intmax_t) h->length, h->sector_cnt);
+
+  /* This loop could be unsafe for large h->sector_cnt, can you
+     see why? */
+  for (i = 0; i < h->sector_cnt; i++) 
+    {
+      if (i != 0)
+        printk (", ");
+      printk ("%jd", (intmax_t) h->sectors[i]); 
+    }
+  printk (")\n");
+}