std::reverse

Use case

Reverse element order.

Explanation

In-place reversal. reverse_copy for non-modifying version. Useful for endianness conversion or reversing instruction sequences.

Time complexity: O(n). Swaps n/2 pairs of elements. See possible implementation.

Code

#include <algorithm>
#include <cstdint>
#include <print>
#include <vector>

int main() {
  std::vector<uint32_t> code = {
      // $ echo "bl 0x40" | llvm-mc -triple=aarch64 -show-encoding
      // bl	#64                             // encoding: [0x10,0x00,0x00,0x94]
      0x94000010,
      // $ echo "sub sp, sp, 0x20" | llvm-mc -triple=aarch64 -show-encoding
      // sub	sp, sp, #32                     // encoding: [0xff,0x83,0x00,0xd1]
      0xd10083ff,
      // $ echo "nop" | llvm-mc -triple=aarch64 -show-encoding
      //	nop                                     // encoding: [0x1f,0x20,0x03,0xd5]
      0xd503201f};

  std::reverse(code.begin(), code.end());

  for (const auto &insn : code) {
    std::println("{:#x}", insn);
  }

  return 0;
}

View on GitHub.

Output

$ ./src/algorithms/build/std-reverse
0xd503201f
0xd10083ff
0x94000010