Add bitwise rotate functions

Author: edubart

bint.lua

@@ -134,7 +134,9 @@ wordbits = wordbits or 32
 
 -- Memoize bint modules
 local memoindex = bits * 64 + wordbits
-if memo[memoindex] then return memo[memoindex] end
+if memo[memoindex] then
+  return memo[memoindex]
+end
 
 -- Validate
 assert(bits % wordbits == 0, 'bitsize is not multiple of word bitsize')
@@ -725,10 +727,10 @@ end
 -- Bitwise right shift words of a bint (in-place). Used only internally.
 function bint:_shrwords(n)
   if n < BINT_SIZE then
-    for i=1,BINT_SIZE-n+1 do
+    for i=1,BINT_SIZE-n do
       self[i] = self[i + n]
     end
-    for i=BINT_SIZE-n,BINT_SIZE do
+    for i=BINT_SIZE-n+1,BINT_SIZE do
       self[i] = 0
     end
   else
@@ -851,6 +853,34 @@ function bint.bwrap(x, y)
   end
 end
 
+-- Rotate left integer x by y bits considering bints.
+-- @param x A bint or a lua integer.
+-- @param y Number of bits to rotate.
+function bint.brol(x, y)
+  x, y = bint_assert_convert(x), bint_assert_tointeger(y)
+  if y > 0 then
+    return (x << y) | (x >> (BINT_BITS - y))
+  elseif y < 0 then
+    return x:bror(-y)
+  else
+    return x
+  end
+end
+
+-- Rotate right integer x by y bits considering bints.
+-- @param x A bint or a lua integer.
+-- @param y Number of bits to rotate.
+function bint.bror(x, y)
+  x, y = bint_assert_convert(x), bint_assert_tointeger(y)
+  if y > 0 then
+    return (x >> y) | (x << (BINT_BITS - y))
+  elseif y < 0 then
+    return x:brol(-y)
+  else
+    return x
+  end
+end
+
 --- Truncate a number to a bint.
 -- Floats numbers are truncated, that is, the fractional port is discarded.
 -- @param x A number to truncate.

docs/index.html

@@ -2282,7 +2282,7 @@ <h2 class="section-header "><a name="Fields"></a>Fields</h2>
 </div> <!-- id="main" -->
 <div id="about">
 <i>generated by <a href="http://github.com/stevedonovan/LDoc">LDoc 1.4.6</a></i>
-<i style="float:right;">Last updated 2020-07-10 09:41:24 </i>
+<i style="float:right;">Last updated 2020-07-10 10:21:42 </i>
 </div> <!-- id="about" -->
 </div> <!-- id="container" -->
 </body>

tests.lua

@@ -1,5 +1,5 @@
-local function test(bits)
-  local bint = require 'bint'(bits)
+local function test(bits, wordbits)
+  local bint = require 'bint'(bits, wordbits)
 
   local function assert_eq(a , b)
     if a ~= b then --luacov:disable
@@ -340,6 +340,12 @@ local function test(bits)
     local function test_shr(x, y)
       assert_eq((bint(x) >> y):tointeger(), x >> y)
     end
+    local function test_brol(x, y)
+      assert_eq(bint(x):brol(y):tointeger(), (x << y) | (x >> (64 - y)))
+    end
+    local function test_bror(x, y)
+      assert_eq(bint(x):bror(y):tointeger(), (x >> y) | (x << (64 - y)))
+    end
     local function test_shlone(x)
       assert_eq(bint(x):_shlone():tointeger(), x << 1)
     end
@@ -355,6 +361,10 @@ local function test(bits)
       test_bwrap(x, y) test_bwrap(x, -y) test_bwrap(-x, y)
       test_shlone(x) test_shlone(y)
       test_shrone(x) test_shrone(y)
+      if bits == 64 then
+        test_brol(x, y)
+        test_bror(x, y)
+      end
     end
     test_ops(0, 0)
     test_ops(1, 0)
@@ -413,6 +423,10 @@ local function test(bits)
     test_ops( 524288, 19)
     test_ops(1048576, 20)
     test_ops(1048576, 100)
+    assert_eq(bint.brol(1, -1), bint.mininteger())
+    assert_eq(bint.bror(1, 1), bint.mininteger())
+    assert_eq(bint.brol(bint.mininteger(), 1), bint(1))
+    assert_eq(bint.bror(bint.mininteger(), -1), bint(1))
   end
 
   do -- pow