/*

* (C) 1999-2007,2025 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/internal/mgf1.h>

#include <botan/hash.h>

#include <botan/mem_ops.h>

#include <algorithm>

namespace Botan {

void mgf1_mask(HashFunction& hash, std::span<const uint8_t> input, std::span<uint8_t> output) {

   uint32_t counter = 0;

   std::vector<uint8_t> buffer(hash.output_length());

   while(!output.empty()) {

      hash.update(input);

      hash.update_be(counter);

      hash.final(buffer);

      const size_t xored = std::min<size_t>(buffer.size(), output.size());

      xor_buf(output.first(xored), std::span{buffer}.first(xored));

      output = output.subspan(xored);

      ++counter;

   }

}

}  // namespace Botan