move integers utils

1 files changed, 40 insertions, 0 deletions

diff --git a/src/bitio/integers.nim b/src/bitio/integers.nim
new file mode 100644
index 0000000..c93c9b8
--- /dev/null
+++ b/src/bitio/integers.nim
@@ -0,0 +1,40 @@
+# gzip-like LZSS compressor
+# Copyright (C) 2018  Pacien TRAN-GIRARD
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const wordBitLength* = 8
+
+proc `/^`*[T: Natural](x, y: T): T =
+  (x + y - 1) div y
+
+proc truncateToUint8*(x: SomeUnsignedInt): uint8 =
+  (x and uint8.high).uint8
+
+proc bitLength*[T: SomeUnsignedInt](x: T): int =
+  var buf = x
+  while buf > 0.T:
+    buf = buf shr 1
+    result += 1
+
+proc leastSignificantBits*[T: SomeUnsignedInt](x: T, bits: int): T =
+  let maskOffset = sizeof(T) * wordBitLength - bits
+  if maskOffset >= 0: (x shl maskOffset) shr maskOffset else: x
+
+iterator chunks*(totalBitLength: int, chunkType: typedesc[SomeInteger]): tuple[index: int, chunkBitLength: int] =
+  let chunkBitLength = sizeof(chunkType) * wordBitLength
+  let wordCount = totalBitLength div chunkBitLength
+  for i in 0..<(wordCount): yield (i, chunkBitLength)
+  let remainder = totalBitLength mod chunkBitLength
+  if remainder > 0: yield (wordCount, remainder)