Super simplified 2-6 2-7, added 2-8

1 files changed, 9 insertions, 6 deletions

diff --git a/ch2/2-6.c b/ch2/2-6.c
index 0932206..918f583 100644
--- a/ch2/2-6.c
+++ b/ch2/2-6.c
@@ -5,15 +5,18 @@
  */
 
 unsigned setbits(unsigned x, unsigned p, unsigned n, unsigned y) {
-    p++;                                            // We're actually interested in p+1.
-    unsigned offset = (p - n);                      // Calculate offset of y bits being inserted into x.
-    unsigned lower_x = x & ~(~0 << offset);         // Grab LSBs of x to save.
-    unsigned y_mask = (y & ~(~0 << n)) << offset;   // Grab pattern from LSBs of y.
-    x = x >> p << p;                                // Just keep MSBs of x.
-    return x | y_mask | lower_x;                    // Concatenate MSBs of x with LSB pattern from y with LSBs of x.
+    // Create a basa from x that zeroes out all of the bits to be set.
+    unsigned a = x & ~(~(~0 << n) << (p + 1 - n));
+
+    // Create a mask from y that zeroes out all of the bits except those to set.
+    unsigned b = (y & ~(~0 << n)) << (p + 1 - n);
+
+    // Apply the mask to the base.
+    return a | b;
 }
 
 int main() {
     printf("%x\n", setbits(0xaa, 3, 3, 0x33));
     printf("%x\n", setbits(0x00, 3, 3, 0xff));
+    return 0;
 }