将 base64 转换为 base62（无特殊字符）

Question

我想在 URL 中传递一个河豚加密字符串，并且想像 base64 一样对其进行编码，但没有任何特殊字符，像 base62 这样的东西会很棒（0-9a-zA-Z）。所以我要做的是使用base64_encode转换河豚加密字符串，并将base64转换为base62。

我知道如何使 base64 url​​ 安全的解决方案，但我真的不希望字符串中有任何特殊字符。 convert_base() 只适用于 36 的基数，数学扩展可以转换到 62 的基数。

有人知道如何使用 PHP 将 base64 字符串转换为 base62 吗？

Answer 1

function base62encode($data) {
    $outstring = '';
    $l = strlen($data);
    for ($i = 0; $i < $l; $i += 8) {
        $chunk = substr($data, $i, 8);
        $outlen = ceil((strlen($chunk) * 8)/6); //8bit/char in, 6bits/char out, round up
        $x = bin2hex($chunk);  //gmp won't convert from binary, so go via hex
        $w = gmp_strval(gmp_init(ltrim($x, '0'), 16), 62); //gmp doesn't like leading 0s
        $pad = str_pad($w, $outlen, '0', STR_PAD_LEFT);
        $outstring .= $pad;
    }
    return $outstring;
}

function base62decode($data) {
    $outstring = '';
    $l = strlen($data);
    for ($i = 0; $i < $l; $i += 11) {
        $chunk = substr($data, $i, 11);
        $outlen = floor((strlen($chunk) * 6)/8); //6bit/char in, 8bits/char out, round down
        $y = gmp_strval(gmp_init(ltrim($chunk, '0'), 62), 16); //gmp doesn't like leading 0s
        $pad = str_pad($y, $outlen * 2, '0', STR_PAD_LEFT); //double output length as as we're going via hex (4bits/char)
        $outstring .= pack('H*', $pad); //same as hex2bin
    }
    return $outstring;
}

$str62 = base62_encode(base64_decode($str64)) // $str64 = our string base64 encoded

所有学分都转到Marcus Bointon。

Answer 2

在不使用 GPM 的情况下，以下内容应该可以在 Base85 上正常工作，不会有太多麻烦。令人惊讶的是，这似乎比 GPM 稍快，可能是因为它没有先转到十六进制。

<?php

/**
* Devide a large number represented as a binary string in the specified base
* and return the remainder.
* 
* @param string &$binary
* @param int $base
* @param int $start
*/
function divmod(&$binary, $base, $divisor, $start = 0)
{
    /** @var int $size */
    $size = strlen($binary);

    // Do long division from most to least significant byte, keep remainder.
    $remainder = 0;
    for ($i = $start; $i < $size; $i++) {
        // Get the byte value, 0-255 inclusive.
        $digit = ord($binary[$i]);

        // Shift the remainder left by base N bits, append the last byte.
        $temp = ($remainder * $base) + $digit;

        // Calculate the value for the current byte.
        $binary[$i] = chr($temp / $divisor);

        // Carry the remainder to the next byte.
        $remainder = $temp % $divisor;
    }

    return $remainder;
}

/**
* Produce a base62 encoded string from a large binary number.
* 
* @param string $binary
* return string
*/
function encodeBase62($binary)
{
    $charMap = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    $base = strlen($charMap);

    $size = strlen($binary);
    $start = $size - strlen(ltrim($binary, "\0"));

    $encoded = "";
    for ($i = $start; $i < $size; ) {
        // Do long division from most to least significant byte, keep remainder.
        $idx = divmod($binary, 256, $base, $i);

        $encoded = $charMap[$idx] . $encoded;

        if (ord($binary[$i]) == 0) {
            $i++; // Skip leading zeros produced by the long division.
        }
    }

    $encoded = str_pad($encoded, $start, "0", STR_PAD_LEFT);

    return $encoded;
}

/**
* Produce a large binary number from a base62 encoded string.
* 
* @param string $ascii
* return string
*/
function decodeBase62($ascii)
{
    $charMap = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    $base = strlen($charMap);

    $size = strlen($ascii);
    $start = $size - strlen(ltrim($ascii, "0"));

    // Convert the ascii representation to binary string.
    $binary = "";
    for ($i = $start; $i < $size; $i++) {
        $byte = strpos($charMap, $ascii[$i]);
        if ($byte === false) {
            throw new OutOfBoundsException("Invlaid encoding at offset '{$ascii[$i]}'");
        }

        $binary .= chr($byte);
    }

    $decode = "";
    for ($i = 0; $i < $size; ) {
        // Do long division from most to least significant byte, keep remainder.
        $idx = divmod($binary, $base, 256, $i);

        $decode = chr($idx) . $decode;

        if (ord($binary[$i]) == 0) {
            $i++; // Skip leading zeros produced by the long division.
        }
    }

    $decode = ltrim($decode, "\0");
    $decode = str_pad($decode, $start, "\0", STR_PAD_LEFT);

    return $decode;
}

$data = pack("N*", 1234567890);
//$data = pack("C*", 0x49, 0x96, 0x02, 0xD2);
var_dump(unpack("N1", $data));

$base62 = encodeBase62($data);
var_dump( $base62 ); // "1ly7vk"

$decoded = decodeBase62($base62);
var_dump(unpack("N1", $decoded)); // 1234567890

var_dump( strcmp($decoded, $data) === 0 ); // true

Answer 3

以下似乎工作正常，根本不使用 base64：

gmp_strval( gmp_init( bin2hex('myencryptedstring'), 16), 62);