More solutions for chapter 5

Author: StBogdan

chapter_5/p5_1.py

@@ -1,14 +1,15 @@
 from utils.binutils import blen
 
-def binary_insert(n:int, m:int, i:int, j:int) -> int:
+
+def binary_insert(n: int, m: int, i: int, j: int) -> int:
     len_n = blen(n)
     len_m = blen(m)
 
-    mask = 0b1 << (len_n - j -1)
-    mask -=1
+    mask = 0b1 << (len_n - j - 1)
+    mask -= 1
     # print(f"Mask is\t{mask:b}")
 
-    mask <<=j +1
+    mask <<= j + 1
     # print(f"Mask is\t{mask:b}")
 
     mask += (0b1 << i+1) - 1
@@ -17,15 +18,16 @@ def binary_insert(n:int, m:int, i:int, j:int) -> int:
     n &= mask
     print(f"N is\t{n:b}")
 
-    j_mask = m<<i
+    j_mask = m << i
     # print(f"Jmask is\t{j_mask:b}")
     n |= j_mask
     return n
 
+
 if __name__ == "__main__":
     n = 0b11110000001
     m = 0b1111
-    i=2
-    j=6
+    i = 2
+    j = 6
 
     print(f"Result of insertion is: {bin(binary_insert(n,m,i,j))}")

chapter_5/p5_6.py

@@ -0,0 +1,22 @@
+def flips_to_convert(a: int, b: int) -> int:
+    flip_c = 0
+    while a and b:
+        flip_c += (a & 0b1) ^ (b & 0b1)
+        a >>= 1
+        b >>= 1
+
+    while a:
+        flip_c += a & 0b1
+        a >>= 1
+    while b:
+        flip_c += b & 0b1
+        b >>= 1
+
+    return flip_c
+
+
+if __name__ == "__main__":
+    exs = [(0b1000010101, 0b1111), (0b11101, 0b01111),
+           (0b1, 0b101), (0b101, 0b101)]
+    for a, b in exs:
+        print(f"Converting {a:b} into {b:b} flips {flips_to_convert(a,b)}")

chapter_5/p5_7.py

@@ -0,0 +1,11 @@
+def pairwise_swap(a: int) -> int:
+    select_mask = 0xAAAAAAAA  # 16 A's
+    odd_bits = a & select_mask
+    even_bits = (a << 1) & select_mask
+    return (odd_bits >> 1) | (even_bits)
+
+
+if __name__ == "__main__":
+    exs = [0b1010, 0b1111, 0b100, 0b110, 0b100101]
+    for x in exs:
+        print(f"Swapping {x:10b} --> {pairwise_swap(x):10b}")

chapter_5/p5_8.py

@@ -0,0 +1,56 @@
+from typing import List
+
+
+def draw_line(screen: List[int],
+              width_bits: int,
+              x1: int,
+              x2: int,
+              y: int) -> None:
+    # print(f"Putting line\t{x1} to {x2} on line {y}")
+    w = width_bits // 8
+    h = len(screen)//w
+
+    start_index = w*y + x1//8
+    end_index = w*y + x2//8
+
+    # print(f"Indexes are\t{start_index} to {end_index}")
+
+    start_mask = (0b1 << (8 - (x1 % 8))) - 1
+    # print(f"Start mask is\t{start_mask:08b}")
+
+    if start_index != end_index:
+        screen[start_index] |= start_mask
+
+        for i in range(start_index+1, end_index):
+            screen[i] |= 0xFF
+
+        end_mask = (0xFF << (8 - (x2 % 8))) % 256
+        # print(f"End mask is\t{end_mask:08b}")
+
+        screen[end_index] |= end_mask
+    else:
+        start_mask &= (0xFF) << (8 - x2 % 8)
+        # print(f"Same mask is {start_mask:08b}")
+        screen[start_index] |= start_mask
+
+
+def print_screen(screen: List[int], width_bits: int):
+    width = width_bits//8
+    for i in range(len(screen)//width):
+        for j in range(width):
+            # print(f"{i} -- {j}")
+            print(f"{screen[i*width+j]:08b}", end=" ")
+        print()
+
+
+if __name__ == "__main__":
+    width_bits = 5 * 8
+    h = 5
+    screen = [0 for i in range(width_bits//8) for j in range(h)]
+    # print_screen(screen, width_bits)
+    for line_index in range(h):
+        start_i = line_index + 1
+        end_i = start_i*5
+        draw_line(screen, width_bits, start_i, end_i, line_index)
+
+    print_screen(screen, width_bits)