Use larger division steps in tobase function

Author: edubart

bint.lua

@@ -376,7 +376,7 @@ end
 -- @see bint.tointeger
 function bint.tonumber(x)
  if isbint(x) then
- if x >= BINT_MATHMININTEGER and x <= BINT_MATHMAXINTEGER then
+ if x <= BINT_MATHMAXINTEGER and x >= BINT_MATHMININTEGER then
  return x:tointeger()
  else
  return tonumber(tostring(x))
@@ -431,9 +431,8 @@ function bint.tobase(x, base, unsigned)
  if unsigned == nil then
  unsigned = base ~= 10
  end
- if base == 10 or base == 16 then
- local inluarange = x >= BINT_MATHMININTEGER and x <= BINT_MATHMAXINTEGER
- if inluarange then
+ if (base == 10 and not unsigned) or (base == 16 and unsigned) then
+ if x <= BINT_MATHMAXINTEGER and x >= BINT_MATHMININTEGER then
  -- integer is small, use tostring or string.format (faster)
  local n = x:tointeger()
  if base == 10 then
@@ -448,14 +447,33 @@ function bint.tobase(x, base, unsigned)
  if neg then
  x = x:abs()
  end
- while not x:iszero() do
- local d
- x, d = xremainder(x, base)
- table.insert(ss, 1, BASE_LETTERS[d])
- end
- if #ss == 0 then
+ local stop = x:iszero()
+ if stop then
  return '0'
  end
+ -- calculate basepow
+ local step = 0
+ local basepow = 1
+ local limit = (BINT_WORDMSB - 1) // base
+ repeat
+ step = step + 1
+ basepow = basepow * base
+ until basepow >= limit
+ -- spit out base digits
+ while not stop do
+ local xd
+ x, xd = xremainder(x, basepow)
+ stop = x:iszero()
+ for _=1,step do
+ local d
+ xd, d = xd // base, xd % base
+ if stop and xd == 0 and d == 0 then
+ -- stop on leading zeros
+ break
+ end
+ table.insert(ss, 1, BASE_LETTERS[d])
+ end
+ end
  if neg then
  table.insert(ss, 1, '-')
  end

tests.lua

@@ -186,13 +186,15 @@ local function test(bits, wordbits)
  assert_eq(bint.parse(1), bint(1))
  assert_eq(bint.parse(1.5), 1.5)
 
+ assert_eq(bint.tobase(math.mininteger, 10), tostring(math.mininteger))
+ assert_eq(bint.tobase(math.maxinteger, 10), tostring(math.maxinteger))
  assert_eq(bint.tobase(1, 10), '1')
  assert_eq(bint.tobase(8, 7), '11')
  assert_eq(bint.tobase(1, 37), nil)
  assert_eq(bint.tobase(1.5, 10), nil)
  assert_eq(bint.tobase(0xff, 16, true), 'ff')
  assert_eq(bint.tobase(-0xff, 16, false), '-ff')
- if bits > 64 then
+ if bits == 64 then
  assert_eq(bint.tobase(-1, 16, true), 'ffffffffffffffff')
  assert_eq(bint.tobase(-2, 16, true), 'fffffffffffffffe')
  end
@@ -616,7 +618,7 @@ end
 
 test(64)
 test(64, 16)
-test(64, 4)
 test(64, 8)
+test(64, 4)
 test(128)
 test(256)