16進数文字列をバイナリに変換

ただのメモ.
16進数文字列をバイナリに変換

# include <stdio.h>
# include <ctype.h>  //  isxdigit

// std::string bin2hex(const std::string& input)
// {
//     std::string res;
//     const char hex[] = "0123456789ABCDEF";
//     for(auto sc : input)
//     {
//         unsigned char c = static_cast<unsigned char>(sc);
//         res += hex[c >> 4];
//         res += hex[c & 0xf];
//     }
//
//     return res;
// }

const char * hex2bin(const char *hex, char *bin, size_t binsize) {
    if (hex && bin) {
        for (; binsize && isxdigit(hex[0]) && isxdigit(hex[1]); hex += 2, bin += 1, binsize -= 1) {     //  fujitanozomu さんの指摘を適用
            int r = sscanf_s(hex, "%2hhx", bin);                                                          //  shiracamus さんの指摘を適用
            if (r != 1) {
                break;
            }
        }
    }

    return hex;
}

# include <tchar.h>
# include <assert.h>

int main()
{
    char buf[80];
    const char * hexPriv = "b91c37cd87a0a66fd0c22eeac1bbac277db47f792310e3a9bb3ebd220fa72a59";
    const char * hexPub = "04daa7c6653f3e1ef969550c1018a1dd2d534d5169f155a8583d79abac1aca9e0d93cdc2a6f8368cf6d703f96dfd7cdb0b3aee8514d8c0225f8732dae79f487578";
    const unsigned char binPriv[] = { 0xb9, 0x1c, 0x37, 0xcd, 0x87, 0xa0, 0xa6, 0x6f, 0xd0, 0xc2, 0x2e, 0xea, 0xc1, 0xbb, 0xac, 0x27, 0x7d, 0xb4, 0x7f, 0x79, 0x23, 0x10, 0xe3, 0xa9, 0xbb, 0x3e, 0xbd, 0x22, 0x0f, 0xa7, 0x2a, 0x59, };
    const unsigned char binPub[] = { 0x04, 0xda, 0xa7, 0xc6, 0x65, 0x3f, 0x3e, 0x1e, 0xf9, 0x69, 0x55, 0x0c, 0x10, 0x18, 0xa1, 0xdd, 0x2d, 0x53, 0x4d, 0x51, 0x69, 0xf1, 0x55, 0xa8, 0x58, 0x3d, 0x79, 0xab, 0xac, 0x1a, 0xca, 0x9e, 0x0d, 0x93, 0xcd, 0xc2, 0xa6, 0xf8, 0x36, 0x8c, 0xf6, 0xd7, 0x03, 0xf9, 0x6d, 0xfd, 0x7c, 0xdb, 0x0b, 0x3a, 0xee, 0x85, 0x14, 0xd8, 0xc0, 0x22, 0x5f, 0x87, 0x32, 0xda, 0xe7, 0x9f, 0x48, 0x75, 0x78, };

    const char *p;
    p = hex2bin(hexPriv, buf, sizeof(buf));
    assert(p == hexPriv + 2 * sizeof(binPriv) && memcmp(buf, binPriv, sizeof(binPriv)) == 0);

    p = hex2bin(hexPub, buf, sizeof(buf));
    assert(p == hexPub + 2 * sizeof(binPub) && memcmp(buf, binPub, sizeof(binPub)) == 0);

    return 0;
}