Address reviewer comments

Author: AntoinePrv

cpp/src/arrow/util/bpacking_scalar_codegen.py

@@ -21,7 +21,7 @@
 # https://github.com/lemire/FrameOfReference/blob/146948b6058a976bc7767262ad3a2ce201486b93/scripts/turbopacking64.py
 
 # Usage:
-#   python bpacking64_codegen.py > bpacking64_default_internal.h
+#   python bpacking_scalar_codegen.py > bpacking_scalar_generated_internal.h
 
 
 import dataclasses
@@ -44,15 +44,6 @@
 // KIND, either express or implied.  See the License for the
 // specific language governing permissions and limitations
 // under the License.
-
-// This file was generated by script which is modified from its original version in GitHub.
-// Original source:
-// https://github.com/lemire/FrameOfReference/blob/master/scripts/turbopacking64.py
-// The original copyright notice follows.
-
-// This code is released under the
-// Apache License Version 2.0 http://www.apache.org/licenses/.
-// (c) Daniel Lemire 2013
 """
 
 HEADER = """
@@ -90,6 +81,7 @@ def out_bit_width(self) -> int:
             return 8
         elif self.out_type.startswith("uint"):
             return int(self.out_type.removeprefix("uint").removesuffix("_t"))
+        raise NotImplementedError(f"Unsupported type {self.out_type}")
 
     @property
     def out_byte_width(self) -> int:
@@ -111,17 +103,21 @@ def print_struct_declaration(self):
         print(f"struct {self.struct_name};")
 
     @property
-    def howmany(self) -> int:
-        """How many values are we going to pack?"""
+    def total_in_values(self) -> int:
+        """How many values are we going to unpack?"""
         if self.smart_halve:
             return self.out_bit_width // 2
         return self.out_bit_width
 
-    def howmanywords(self, bit: int) -> int:
-        return (self.howmany * bit + self.out_bit_width - 1) // self.out_bit_width
+    def total_out_values(self, bit: int) -> int:
+        return (
+            self.total_in_values * bit + self.out_bit_width - 1
+        ) // self.out_bit_width
 
-    def howmanybytes(self, bit: int) -> int:
-        return (self.howmany * bit + self.out_byte_width - 1) // self.out_byte_width
+    def total_out_bytes(self, bit: int) -> int:
+        return (
+            self.total_in_values * bit + self.out_byte_width - 1
+        ) // self.out_byte_width
 
     def print_unpack_k(self, bit: int) -> None:
         print(
@@ -135,13 +131,13 @@ def print_unpack_k(self, bit: int) -> None:
         print()
         maskstr = " & mask"
 
-        for k in range(self.howmanywords(bit) - 1):
+        for k in range(self.total_out_values(bit) - 1):
             print(
                 f"    const auto w{k} = LoadInt<{self.out_type}>("
                 f"in + {k} * {self.out_byte_width});"
             )
 
-        k = self.howmanywords(bit) - 1
+        k = self.total_out_values(bit) - 1
         use_smart_halving = self.smart_halve and bit % 2 == 1
         if use_smart_halving:
             print(
@@ -154,7 +150,7 @@ def print_unpack_k(self, bit: int) -> None:
                 f"in + {k} * {self.out_byte_width});"
             )
 
-        for j in range(self.howmany):
+        for j in range(self.total_in_values):
             firstword = j * bit // self.out_bit_width
             secondword = (j * bit + bit - 1) // self.out_bit_width
             firstshift = (j * bit) % self.out_bit_width
@@ -176,18 +172,20 @@ def print_unpack_k(self, bit: int) -> None:
 
         if use_smart_halving:
             print(
-                f"    return in + ({self.howmanywords(bit) - 1} * {self.out_byte_width}"
+                f"    return in + ({self.total_out_values(bit) - 1} * {self.out_byte_width}"
                 f" + {self.out_byte_width // 2});"
             )
         else:
-            print(f"    return in + ({self.howmanywords(bit)} * {self.out_byte_width});")
+            print(
+                f"    return in + ({self.total_out_values(bit)} * {self.out_byte_width});"
+            )
         print("  }")
 
     def print_struct_k(self, bit: int) -> None:
         print("template<>")
         print(f"struct {self.struct_specialization(bit)} {{")
         print()
-        print(f"  static constexpr int kValuesUnpacked = {self.howmany};")
+        print(f"  static constexpr int kValuesUnpacked = {self.total_in_values};")
         print()
         self.print_unpack_k(bit)
         print("};")