chromium/third_party/abseil-cpp/absl/random/internal/randen_round_keys.cc

// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "absl/random/internal/randen_traits.h"

// This file contains only the round keys for randen.
//
// "Nothing up my sleeve" numbers from the first hex digits of Pi, obtained
// from http://hexpi.sourceforge.net/. The array was generated by following
// Python script:

/*
python >tmp.cc << EOF
"""Generates Randen round keys array from pi-hex.62500.txt file."""
import binascii

KEYS = 17 * 8

def chunks(l, n):
    """Yield successive n-sized chunks from l."""
    for i in range(0, len(l), n):
        yield l[i:i + n]

def pairwise(t):
    """Transforms sequence into sequence of pairs."""
    it = iter(t)
    return zip(it,it)

def digits_from_pi():
  """Reads digits from hexpi.sourceforge.net file."""
  with open("pi-hex.62500.txt") as file:
    return file.read()

def digits_from_urandom():
  """Reads digits from /dev/urandom."""
  with open("/dev/urandom") as file:
    return binascii.hexlify(file.read(KEYS * 16))

def print_row(b)
  print("  0x{0}, 0x{1}, 0x{2}, 0x{3}, 0x{4}, 0x{5}, 0x{6}, 0x{7}, 0x{8}, 0x{9},
0x{10}, 0x{11}, 0x{12}, 0x{13}, 0x{14}, 0x{15},".format(*b))


digits = digits_from_pi()
#digits = digits_from_urandom()

print("namespace {")
print("static constexpr size_t kKeyBytes = {0};\n".format(KEYS * 16))
print("}")

print("alignas(16) const unsigned char kRandenRoundKeysBE[kKeyBytes] = {")

for i, u16 in zip(range(KEYS), chunks(digits, 32)):
  b = list(chunks(u16, 2))
  print_row(b)

print("};")

print("alignas(16) const unsigned char kRandenRoundKeys[kKeyBytes] = {")

for i, u16 in zip(range(KEYS), chunks(digits, 32)):
  b = list(chunks(u16, 2))
  b.reverse()
  print_row(b)

print("};")

EOF

*/

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace random_internal {
namespace {
static constexpr size_t kKeyBytes = …;
}

alignas(16) const unsigned char kRandenRoundKeysBE[kKeyBytes] = …;

alignas(16) const unsigned char kRandenRoundKeys[kKeyBytes] = …;

}  // namespace random_internal
ABSL_NAMESPACE_END
}  // namespace absl