base64编解码的另外几个版本

#include "crypto/encode/base64.h"

static const std::string base64_chars =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "abcdefghijklmnopqrstuvwxyz"
    "0123456789+/";

static inline bool is_base64(unsigned char c)
{
    return (isalnum(c) || (c == '+') || (c == '/'));
}

std::string Base64::Encode(const std::string& src)
{
    std::string ret;
    unsigned char char_array_3[3];
    unsigned char char_array_4[4];

    size_t srcLen = src.length();
    const char* pSrc = src.c_str();

    size_t i = 0;
    while (srcLen--) {
        char_array_3[i++] = *(pSrc++);
        if (i == 3) {
            char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
            char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
            char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
            char_array_4[3] = char_array_3[2] & 0x3f;

            for (i = 0; (i <4); i++)
                ret += base64_chars[char_array_4[i]];
            i = 0;
        }
    }

    size_t j = 0;
    if (i)
    {
        for (j = i; j < 3; j++)
            char_array_3[j] = '';

        char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
        char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
        char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
        char_array_4[3] = char_array_3[2] & 0x3f;

        for (j = 0; (j < i + 1); j++)
            ret += base64_chars[char_array_4[j]];

        while ((i++ < 3))
            ret += '=';

    }

    return ret;
}

std::string Base64::Encode(const unsigned char* src, size_t dataLen)
{
    if ((src == NULL) || (dataLen == 0))
    {
        return std::string();
    }

    std::string ret;
    unsigned char char_array_3[3];
    unsigned char char_array_4[4];

    size_t srcLen = dataLen;
    const char* pSrc = reinterpret_cast<const char*>(src);

    size_t i = 0;
    while (srcLen--) {
        char_array_3[i++] = *(pSrc++);
        if (i == 3) {
            char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
            char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
            char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
            char_array_4[3] = char_array_3[2] & 0x3f;

            for (i = 0; (i <4); i++)
                ret += base64_chars[char_array_4[i]];
            i = 0;
        }
    }

    size_t j = 0;
    if (i)
    {
        for (j = i; j < 3; j++)
            char_array_3[j] = '';

        char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
        char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
        char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
        char_array_4[3] = char_array_3[2] & 0x3f;

        for (j = 0; (j < i + 1); j++)
            ret += base64_chars[char_array_4[j]];

        while ((i++ < 3))
            ret += '=';
    }

    return ret;
}

bool Base64::Decode(const std::string& src, std::string& out)
{
    out.clear();

    size_t in_len = src.size();
    size_t i = 0;
    size_t j = 0;
    size_t in_ = 0;
    unsigned char char_array_4[4], char_array_3[3];

    while (in_len-- && (src[in_] != '=') && is_base64(src[in_])) {
        char_array_4[i++] = src[in_]; in_++;
        if (i == 4) {
            for (i = 0; i <4; i++)
                char_array_4[i] = (unsigned char)base64_chars.find(char_array_4[i]);

            char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
            char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
            char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

            for (i = 0; (i < 3); i++)
                out += char_array_3[i];
            i = 0;
        }
    }

    if (i) {
        for (j = i; j <4; j++)
            char_array_4[j] = 0;

        for (j = 0; j <4; j++)
            char_array_4[j] = (unsigned char)base64_chars.find(char_array_4[j]);

        char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
        char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
        char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

        for (j = 0; (j < i - 1); j++)
            out += char_array_3[j];
    }

    return true;
}

bool Base64::Decode(const unsigned char* src, size_t srcLen, unsigned char* decoded, size_t& decoded_length)
{
    if ((src == NULL) || (srcLen < 1))
        return false;
    if ((decoded == NULL) || (decoded_length < 1))
        return false;

    size_t i = 0;
    size_t j = 0;
    size_t in_ = 0;
    unsigned char char_array_4[4];
    unsigned char char_array_3[3];

    size_t offset = 0;
    while (srcLen-- && (src[in_] != '=') && is_base64(src[in_])) {
        char_array_4[i++] = src[in_]; in_++;
        if (i == 4) {
            for (i = 0; i <4; i++)
                char_array_4[i] = (unsigned char)base64_chars.find(char_array_4[i]);

            char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
            char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
            char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

            for (i = 0; i < 3; i++)
            {
                if (offset < decoded_length)
                    decoded[offset++] = char_array_3[i];
                else
                    return false;
            }
            i = 0;
        }
    }

    if (i) {
        for (j = i; j <4; j++)
            char_array_4[j] = 0;

        for (j = 0; j <4; j++)
            char_array_4[j] = (unsigned char)base64_chars.find(char_array_4[j]);

        char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
        char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
        char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

        for (j = 0; (j < i - 1); j++)
        {
            if (offset < decoded_length)
                decoded[offset++] = char_array_3[j];
            else
                return false;
        }
    }

    decoded_length = offset;

    return true;
}

bool Base64::Decode(const unsigned char* src, size_t srcLen, std::vector<unsigned char>& out)
{
    out.clear();

    size_t i = 0;
    size_t j = 0;
    size_t in_ = 0;
    unsigned char char_array_4[4];
    unsigned char char_array_3[3];

    while (srcLen-- && (src[in_] != '=') && is_base64(src[in_])) {
        char_array_4[i++] = src[in_]; in_++;
        if (i == 4) {
            for (i = 0; i <4; i++)
                char_array_4[i] = (unsigned char)base64_chars.find(char_array_4[i]);

            char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
            char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
            char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

            for (i = 0; (i < 3); i++)
                out.push_back(char_array_3[i]);
            i = 0;
        }
    }

    if (i) {
        for (j = i; j <4; j++)
            char_array_4[j] = 0;

        for (j = 0; j <4; j++)
            char_array_4[j] = (unsigned char)base64_chars.find(char_array_4[j]);

        char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
        char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
        char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

        for (j = 0; (j < i - 1); j++)
            out.push_back(char_array_3[j]);
    }

    return true;
}