Research V6 development

Work on file usr/sys/ken/subr.c

Synthesized-from: v6

diff --git a/usr/sys/ken/subr.c b/usr/sys/ken/subr.c
new file mode 100644 (file)
index 0000000..ee79a50
--- /dev/null
+++ b/usr/sys/ken/subr.c
@@ -0,0 +1,207 @@
+#
+/*
+ */
+
+#include "../param.h"
+#include "../conf.h"
+#include "../inode.h"
+#include "../user.h"
+#include "../buf.h"
+#include "../systm.h"
+
+/*
+ * Bmap defines the structure of file system storage
+ * by returning the physical block number on a device given the
+ * inode and the logical block number in a file.
+ * When convenient, it also leaves the physical
+ * block number of the next block of the file in rablock
+ * for use in read-ahead.
+ */
+bmap(ip, bn)
+struct inode *ip;
+int bn;
+{
+       register *bp, *bap, nb;
+       int *nbp, d, i;
+
+       d = ip->i_dev;
+       if(bn & ~077777) {
+               u.u_error = EFBIG;
+               return(0);
+       }
+
+       if((ip->i_mode&ILARG) == 0) {
+
+               /*
+                * small file algorithm
+                */
+
+               if((bn & ~7) != 0) {
+
+                       /*
+                        * convert small to large
+                        */
+
+                       if ((bp = alloc(d)) == NULL)
+                               return(NULL);
+                       bap = bp->b_addr;
+                       for(i=0; i<8; i++) {
+                               *bap++ = ip->i_addr[i];
+                               ip->i_addr[i] = 0;
+                       }
+                       ip->i_addr[0] = bp->b_blkno;
+                       bdwrite(bp);
+                       ip->i_mode =| ILARG;
+                       goto large;
+               }
+               nb = ip->i_addr[bn];
+               if(nb == 0 && (bp = alloc(d)) != NULL) {
+                       bdwrite(bp);
+                       nb = bp->b_blkno;
+                       ip->i_addr[bn] = nb;
+                       ip->i_flag =| IUPD;
+               }
+               rablock = 0;
+               if (bn<7)
+                       rablock = ip->i_addr[bn+1];
+               return(nb);
+       }
+
+       /*
+        * large file algorithm
+        */
+
+    large:
+       i = bn>>8;
+       if(bn & 0174000)
+               i = 7;
+       if((nb=ip->i_addr[i]) == 0) {
+               ip->i_flag =| IUPD;
+               if ((bp = alloc(d)) == NULL)
+                       return(NULL);
+               ip->i_addr[i] = bp->b_blkno;
+       } else
+               bp = bread(d, nb);
+       bap = bp->b_addr;
+
+       /*
+        * "huge" fetch of double indirect block
+        */
+
+       if(i == 7) {
+               i = ((bn>>8) & 0377) - 7;
+               if((nb=bap[i]) == 0) {
+                       if((nbp = alloc(d)) == NULL) {
+                               brelse(bp);
+                               return(NULL);
+                       }
+                       bap[i] = nbp->b_blkno;
+                       bdwrite(bp);
+               } else {
+                       brelse(bp);
+                       nbp = bread(d, nb);
+               }
+               bp = nbp;
+               bap = bp->b_addr;
+       }
+
+       /*
+        * normal indirect fetch
+        */
+
+       i = bn & 0377;
+       if((nb=bap[i]) == 0 && (nbp = alloc(d)) != NULL) {
+               nb = nbp->b_blkno;
+               bap[i] = nb;
+               bdwrite(nbp);
+               bdwrite(bp);
+       } else
+               brelse(bp);
+       rablock = 0;
+       if(i < 255)
+               rablock = bap[i+1];
+       return(nb);
+}
+
+/*
+ * Pass back  c  to the user at his location u_base;
+ * update u_base, u_count, and u_offset.  Return -1
+ * on the last character of the user's read.
+ * u_base is in the user address space unless u_segflg is set.
+ */
+passc(c)
+char c;
+{
+
+       if(u.u_segflg)
+               *u.u_base = c; else
+               if(subyte(u.u_base, c) < 0) {
+                       u.u_error = EFAULT;
+                       return(-1);
+               }
+       u.u_count--;
+       if(++u.u_offset[1] == 0)
+               u.u_offset[0]++;
+       u.u_base++;
+       return(u.u_count == 0? -1: 0);
+}
+
+/*
+ * Pick up and return the next character from the user's
+ * write call at location u_base;
+ * update u_base, u_count, and u_offset.  Return -1
+ * when u_count is exhausted.  u_base is in the user's
+ * address space unless u_segflg is set.
+ */
+cpass()
+{
+       register c;
+
+       if(u.u_count == 0)
+               return(-1);
+       if(u.u_segflg)
+               c = *u.u_base; else
+               if((c=fubyte(u.u_base)) < 0) {
+                       u.u_error = EFAULT;
+                       return(-1);
+               }
+       u.u_count--;
+       if(++u.u_offset[1] == 0)
+               u.u_offset[0]++;
+       u.u_base++;
+       return(c&0377);
+}
+
+/*
+ * Routine which sets a user error; placed in
+ * illegal entries in the bdevsw and cdevsw tables.
+ */
+nodev()
+{
+
+       u.u_error = ENODEV;
+}
+
+/*
+ * Null routine; placed in insignificant entries
+ * in the bdevsw and cdevsw tables.
+ */
+nulldev()
+{
+}
+
+/*
+ * copy count words from from to to.
+ */
+bcopy(from, to, count)
+int *from, *to;
+{
+       register *a, *b, c;
+
+       a = from;
+       b = to;
+       c = count;
+       do
+               *b++ = *a++;
+       while(--c);
+}