add support for lua 5.4 alpha

Signed-off-by: Asbjørn Sloth Tønnesen <ast@2e8.dk>

2 files changed, 111 insertions, 0 deletions

diff --git a/lua/inet/bitops/init.lua b/lua/inet/bitops/init.lua
new file mode 100644
index 0000000..6af992b
--- /dev/null
+++ b/lua/inet/bitops/init.lua
@@ -0,0 +1,6 @@
+local versions = {
+	['Lua 5.2'] = 'bit32',
+}
+
+local library = versions[_VERSION] or 'inet.bitops.native'
+return assert(require(library))
diff --git a/lua/inet/bitops/native.lua b/lua/inet/bitops/native.lua
new file mode 100644
index 0000000..48470f9
--- /dev/null
+++ b/lua/inet/bitops/native.lua
@@ -0,0 +1,105 @@
+-- Until Lua 5.2 support is dropped, we can't use the native operators directly
+-- https://pastebin.com/fepexfdU - assumed public domain license
+
+--[[ Backwards compat for Lua 5.3; only loaded in 5.3 because package.loaded is
+     prepopulated with the existing global bit32 in 5.2. ]]
+
+local bit32 = {}
+
+-------------------------------------------------------------------------------
+
+local function fold(init, op, ...)
+  local result = init
+  local args = table.pack(...)
+  for i = 1, args.n do
+    result = op(result, args[i])
+  end
+  return result
+end
+
+local function trim(n)
+  return n & 0xFFFFFFFF
+end
+
+local function mask(w)
+  return ~(0xFFFFFFFF << w)
+end
+
+function bit32.arshift(x, disp)
+  return x // (2 ^ disp)
+end
+
+function bit32.band(...)
+  return fold(0xFFFFFFFF, function(a, b) return a & b end, ...)
+end
+
+function bit32.bnot(x)
+  return ~x
+end
+
+function bit32.bor(...)
+  return fold(0, function(a, b) return a | b end, ...)
+end
+
+function bit32.btest(...)
+  return bit32.band(...) ~= 0
+end
+
+function bit32.bxor(...)
+  return fold(0, function(a, b) return a ~ b end, ...)
+end
+
+local function fieldargs(f, w)
+  w = w or 1
+  assert(f >= 0, "field cannot be negative")
+  assert(w > 0, "width must be positive")
+  assert(f + w <= 32, "trying to access non-existent bits")
+  return f, w
+end
+
+function bit32.extract(n, field, width)
+  local f, w = fieldargs(field, width)
+  return (n >> f) & mask(w)
+end
+
+function bit32.replace(n, v, field, width)
+  local f, w = fieldargs(field, width)
+  local m = mask(w)
+  return (n & ~(m << f)) | ((v & m) << f)
+end
+
+function bit32.lrotate(x, disp)
+  if disp == 0 then
+    return x
+  elseif disp < 0 then
+    return bit32.rrotate(x, -disp)
+  else
+    disp = disp & 31
+    x = trim(x)
+    return trim((x << disp) | (x >> (32 - disp)))
+  end
+end
+
+function bit32.lshift(x, disp)
+  return trim(x << disp)
+end
+
+function bit32.rrotate(x, disp)
+  if disp == 0 then
+    return x
+  elseif disp < 0 then
+    return bit32.lrotate(x, -disp)
+  else
+    disp = disp & 31
+    x = trim(x)
+    return trim((x >> disp) | (x << (32 - disp)))
+  end
+end
+
+function bit32.rshift(x, disp)
+  return trim(x >> disp)
+end
+
+-------------------------------------------------------------------------------
+
+return bit32