From 7e0f021a9aec35fd8e6725e87e3313b101d26f5e Mon Sep 17 00:00:00 2001
From: Tobias Klauser <tklauser@distanz.ch>
Date: Sun, 27 Jan 2008 11:37:44 +0100
Subject: Initial import (2.0.2-6)

---
 reference/C/CONTRIB/OR_USING_C/13.3.c | 118 ++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 reference/C/CONTRIB/OR_USING_C/13.3.c

(limited to 'reference/C/CONTRIB/OR_USING_C/13.3.c')

diff --git a/reference/C/CONTRIB/OR_USING_C/13.3.c b/reference/C/CONTRIB/OR_USING_C/13.3.c
new file mode 100644
index 0000000..a0dc4b1
--- /dev/null
+++ b/reference/C/CONTRIB/OR_USING_C/13.3.c
@@ -0,0 +1,118 @@
+
+#include	<sys/param.h>
+#include	<sys/time.h>
+#include	<sys/vnode.h>
+#include	<ufs/inode.h>
+#include	<ufs/fs.h>
+
+#define sblock    sb_un.u_sblock
+
+/*
+ * The super block.  We allow enough room for
+ * a complete disk block.
+ */
+union {
+    struct  fs u_sblock;
+    char    dummy[SBSIZE];
+} sb_un;
+
+read_blocks(dp)
+struct dinode *dp;
+{
+    int count;
+    register int i, n;
+    char dblock[MAXBSIZE];
+
+    count = dp->di_size;
+
+    /*
+     * For each direct block in the file (NDADDR indicates
+     * the number of direct addresses stored)...
+     */
+    for (i = 0; (i < NDADDR) && (count > 0); i++) {
+        /* 
+         * Read in the block from disk.  Read in count
+         * bytes or a disk block, whichever is less.
+         */
+        bread(fsbtodb(&sblock, dp->di_db[i]), dblock,
+              n = min(count, sblock.fs_bsize));
+        count -= n;
+
+        /* process data block ... */
+   
+    }
+
+    /* 
+     * Now start reading the indirect blocks.  NIADDR is 
+     * the number of indirect addresses.  Recall that 
+     * the first indirect address is singly indirect,
+     * the second is doubly indirect, an so on.
+     */
+    for (i = 0; (i < NIADDR) && (count > 0); i++)
+        read_indirect (dp->di_ib[i], i, &count);
+}
+
+/*
+ * read_indirect--read the indirect blocks of the file.  The
+ * level argument indicates our level of indirection; 0 is 
+ * singly indirect, 1 is doubly indirect, and so on.
+ */
+read_indirect (blkno, level, count)
+ino_t blkno;
+int *count;
+int level;
+{
+    register int i, n;
+    char dblock[MAXBSIZE];
+    daddr_t idblk[MAXBSIZE / sizeof(daddr_t)];
+
+    /*
+     * Read in the block from disk.
+     */
+    if (blkno)
+        bread(fsbtodb(&sblock, blkno), idblk, sblock.fs_bsize);
+     else
+        bzero(idblk, sblock.fs_bsize);
+
+    /* 
+     * If level is zero, then this block contains disk block
+     * addresses, since blkno was a singly indirect address.
+     * If level is non-zero, then this block contains addresses
+     * of more indirect blocks.
+     */
+    if (level <= 0) {
+        /*
+         * For each disk block (the NINDIR macro returns
+         * the number of indirect addresses in a block)...
+         */
+        for (i = 0; (i < NINDIR(&sblock)) && (*count > 0); i++) {
+            /*
+             * Read in the block from disk.
+             */
+            bread(fsbtodb(&sblock, idblk[i]), dblock,
+                  n = min(*count, sblock.fs_bsize));
+            *count -= n;
+
+            /* process data block ... */
+      }
+
+      /*
+       * Done processing.
+       */
+      return;
+  }
+
+     /*
+      * Decrement the level we're at.
+      */
+     level--;
+
+     /*
+      * Handle the next level of indirection by calling
+      * ourselves recursively with each address in this
+      * block.
+      */
+     for (i = 0; i < NINDIR(&sblock); i++)  
+         read_indirect(idblk[i], level, count);
+}
+
-- 
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