Repository: TheAlgorithms/C-Plus-Plus
File: hashing/sha256.cpp (C++)

Code before:

/**
 * @namespace hashing
 * @brief Hashing algorithms
 */
namespace hashing {
/**
 * @namespace SHA-256
 * @brief Functions for the [SHA-256](https://en.wikipedia.org/wiki/SHA-2)
 * algorithm implementation
 */
namespace sha256 {
/**
 * @brief Computes size of the padded input
 * @param input Input string
 * @return size_t Size of the padded input
 */
std::size_t compute_padded_size(const std::size_t input_size) {
    size_t padded_input_size = 0;
    if (input_size % 64 < 56) {
        padded_input_size = input_size + 64 - (input_size % 64);
    } else {
        padded_input_size = input_size + 128 - (input_size % 64);
    }
    return padded_input_size;
}

/**
 * @brief Returns the byte at position byte_num in in_value
 * @param in_value Input value
 * @param byte_num Position of byte to be returned
 * @return uint8_t Byte at position byte_num
 */
uint8_t extract_byte(const std::size_t in_value, const std::size_t byte_num) {
    return ((in_value >> (byte_num * 8)) & 0xFF);
}

/**
 * @brief Returns the character at pos after the input is padded
 * @param input Input string
 * @param pos Position of character to be returned
 * @return char Character at the index pos in the padded string
 */
char get_char(const std::string &input, std::size_t pos) {
    size_t input_size = input.length();
    size_t padded_input_size = compute_padded_size(input_size);
    if (pos < input_size) {
        return input[pos];
    }
    if (pos == input_size) {
        return '\x80';

Review comment (suggestion):
```suggestion
std::size_t compute_padded_size(const std::size_t input_size) {
    if (input_size % 64 < 56) {
        return input_size + 64 - (input_size % 64);
    }
    return input_size + 128 - (input_size % 64);
}
```

Code after:
#include <vector>    /// For std::vector

/**
 * @namespace hashing
 * @brief Hashing algorithms
 */
namespace hashing {
/**
 * @namespace SHA-256
 * @brief Functions for the [SHA-256](https://en.wikipedia.org/wiki/SHA-2)
 * algorithm implementation
 */
namespace sha256 {
/**
 * @class Hash
 * @brief Contains hash array and functions to update it and convert it to a
 * hexadecimal string
 */
class Hash {
    // Initialize array of hash values with first 32 bits of the fractional
    // parts of the square roots of the first 8 primes 2..19
    std::array<uint32_t, 8> hash = {0x6A09E667, 0xBB67AE85, 0x3C6EF372,
                                    0xA54FF53A, 0x510E527F, 0x9B05688C,
                                    0x1F83D9AB, 0x5BE0CD19};

 public:
    void update(const std::array<uint32_t, 64> &blocks);
    std::string to_string() const;
};

/**
 * @brief Rotates the bits of a 32-bit unsigned integer
 * @param n Integer to rotate
 * @param rotate Number of bits to rotate
 * @return uint32_t The rotated integer
 */
uint32_t right_rotate(uint32_t n, size_t rotate) {
    return (n >> rotate) | (n << (32 - rotate));
}

/**
 * @brief Updates the hash array
 * @param blocks Message schedule array
 * @return void
 */
void Hash::update(const std::array<uint32_t, 64> &blocks) {
    // Initialize array of round constants with first 32 bits of the fractional
    // parts of the cube roots of the first 64 primes 2..311
    const std::array<uint32_t, 64> round_constants = {
        0x428A2F98, 0x71374491, 0xB5C0FBCF, 0xE9B5DBA5, 0x3956C25B, 0x59F111F1,
        0x923F82A4, 0xAB1C5ED5, 0xD807AA98, 0x12835B01, 0x243185BE, 0x550C7DC3,