b64.ipp

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/* Copyright 2025 NTESS. See the top-level LICENSE.txt file for details.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */
#include <openssl/evp.h>
#include <cstdlib>
#include <iostream>
#include <string>
#include <limits>
 
// link with -lssl  -lcrypto
 
namespace adc {
 
// return the output data size to hold encoded data of size input_len
// including the terminal null byte
size_t b64_length(size_t input_len)
{
    return static_cast<int>(4*((input_len+2)/3) + 1);
}
 
// return the output data size to hold decoded data of size input_len
// including the terminal null byte
size_t binary_length(size_t input_len)
{
    return static_cast<int>(3*input_len/4 + 1);
}
 
// return the b64buf pointer populated with the b64 version
// of the input bytes, or NULL if not possible.
unsigned char *base64(const unsigned char *binary, size_t binary_len, unsigned char *b64buf, size_t b64buf_length)
{
    const size_t pl = b64_length(binary_len);
    if (!b64buf || b64buf_length < pl || b64buf_length >= std::numeric_limits<int>::max())
        return NULL;
    const int ol = EVP_EncodeBlock(b64buf, binary, binary_len);
    if (ol != static_cast<int>(pl-1)) {
        std::cerr << "Insufficient space to b64 encode" << std::endl;
        return NULL;
    }
    return b64buf;
}
 
// return the binary pointer populated with the binary version
// of the b64buf base64 bytes, or NULL if not possible.
unsigned char *decode64(const unsigned char *b64buf, size_t b64buf_length, unsigned char *binary, size_t binary_len)
{
    const size_t pl = binary_length(b64buf_length);
    if (!binary || binary_len < pl || binary_len > std::numeric_limits<int>::max())
        return NULL;
    const int ol = EVP_DecodeBlock(binary, b64buf, b64buf_length);
    if (static_cast<int>(pl-1) != ol) { 
        std::cerr << "Insufficient space to b64 decode;" << std::endl;
        return NULL;
    }
    return binary;
}
 
}