Javascript SHA-1：Secure Hash Algorithm_基础知识

From:http://pajhome.org.uk/crypt/md5/sha1src.html

<span class="comment">/*
 * A JavaScript implementation of the Secure Hash Algorithm, SHA-1, as defined
 * in FIPS PUB 180-1
 * Version 2.1a Copyright Paul Johnston 2000 - 2002.
 * Other contributors: Greg Holt, Andrew Kepert, Ydnar, Lostinet
 * Distributed under the BSD License
 * See http://pajhome.org.uk/crypt/md5 for details.
 */</span>

<span class="comment">/*
 * Configurable variables. You may need to tweak these to be compatible with
 * the server-side, but the defaults work in most cases.
 */</span>
<span class="reserved_word">var</span> hexcase <span class="symbol">=</span> <span class="numeric">0</span><span class="symbol">;</span> <span class="comment">/* hex output format. 0 - lowercase; 1 - uppercase    */</span>
<span class="reserved_word">var</span> b64pad <span class="symbol">=</span> <span class="string">""</span><span class="symbol">;</span> <span class="comment">/* base-64 pad character. "=" for strict RFC compliance  */</span>
<span class="reserved_word">var</span> chrsz  <span class="symbol">=</span> <span class="numeric">8</span><span class="symbol">;</span> <span class="comment">/* bits per input character. 8 - ASCII; 16 - Unicode   */</span>

<span class="comment">/*
 * These are the functions you'll usually want to call
 * They take string arguments and return either hex or base-64 encoded strings
 */</span>
<span class="reserved_word">function</span> hex_sha1<span class="braces">(</span>s<span class="braces">)</span><span class="braces">{</span><span class="reserved_word">return</span> binb2hex<span class="braces">(</span>core_sha1<span class="braces">(</span>str2binb<span class="braces">(</span>s<span class="braces">)</span>,s.<span class="predefined_identifier">length</span> * chrsz<span class="braces">)</span><span class="braces">)</span><span class="symbol">;</span><span class="braces">}</span>
<span class="reserved_word">function</span> b64_sha1<span class="braces">(</span>s<span class="braces">)</span><span class="braces">{</span><span class="reserved_word">return</span> binb2b64<span class="braces">(</span>core_sha1<span class="braces">(</span>str2binb<span class="braces">(</span>s<span class="braces">)</span>,s.<span class="predefined_identifier">length</span> * chrsz<span class="braces">)</span><span class="braces">)</span><span class="symbol">;</span><span class="braces">}</span>
<span class="reserved_word">function</span> str_sha1<span class="braces">(</span>s<span class="braces">)</span><span class="braces">{</span><span class="reserved_word">return</span> binb2str<span class="braces">(</span>core_sha1<span class="braces">(</span>str2binb<span class="braces">(</span>s<span class="braces">)</span>,s.<span class="predefined_identifier">length</span> * chrsz<span class="braces">)</span><span class="braces">)</span><span class="symbol">;</span><span class="braces">}</span>
<span class="reserved_word">function</span> hex_hmac_sha1<span class="braces">(</span>key, data<span class="braces">)</span><span class="braces">{</span> <span class="reserved_word">return</span> binb2hex<span class="braces">(</span>core_hmac_sha1<span class="braces">(</span>key, data<span class="braces">)</span><span class="braces">)</span><span class="symbol">;</span><span class="braces">}</span>
<span class="reserved_word">function</span> b64_hmac_sha1<span class="braces">(</span>key, data<span class="braces">)</span><span class="braces">{</span> <span class="reserved_word">return</span> binb2b64<span class="braces">(</span>core_hmac_sha1<span class="braces">(</span>key, data<span class="braces">)</span><span class="braces">)</span><span class="symbol">;</span><span class="braces">}</span>
<span class="reserved_word">function</span> str_hmac_sha1<span class="braces">(</span>key, data<span class="braces">)</span><span class="braces">{</span> <span class="reserved_word">return</span> binb2str<span class="braces">(</span>core_hmac_sha1<span class="braces">(</span>key, data<span class="braces">)</span><span class="braces">)</span><span class="symbol">;</span><span class="braces">}</span>

<span class="comment">/*
 * Perform a simple self-test to see if the VM is working
 */</span>
<span class="reserved_word">function</span> sha1_vm_test<span class="braces">(</span><span class="braces">)</span>
<span class="braces">{</span>
 <span class="reserved_word">return</span> hex_sha1<span class="braces">(</span><span class="string">"abc"</span><span class="braces">)</span> <span class="symbol">=</span><span class="symbol">=</span> <span class="string">"a9993e364706816aba3e25717850c26c9cd0d89d"</span><span class="symbol">;</span>
<span class="braces">}</span>

<span class="comment">/*
 * Calculate the SHA-1 of an array of big-endian words, and a bit length
 */</span>
<span class="reserved_word">function</span> core_sha1<span class="braces">(</span>x, len<span class="braces">)</span>
<span class="braces">{</span>
 <span class="comment">/* append padding */</span>
 x[len <span class="symbol">></span><span class="symbol">></span> <span class="numeric">5</span>] <span class="symbol">|</span><span class="symbol">=</span> <span class="numeric">0x80</span> <span class="symbol"><span class="symbol"> <span class="braces">(</span><span class="numeric">24</span> - len % <span class="numeric">32</span><span class="braces">)</span><span class="symbol">;</span>
 x[<span class="braces">(</span><span class="braces">(</span>len + <span class="numeric">64</span> <span class="symbol">></span><span class="symbol">></span> <span class="numeric">9</span><span class="braces">)</span> <span class="symbol"><span class="symbol"> <span class="numeric">4</span><span class="braces">)</span> + <span class="numeric">15</span>] <span class="symbol">=</span> len<span class="symbol">;</span>

 <span class="reserved_word">var</span> w <span class="symbol">=</span> <span class="predefined_type">Array</span><span class="braces">(</span><span class="numeric">80</span><span class="braces">)</span><span class="symbol">;</span>
 <span class="reserved_word">var</span> a <span class="symbol">=</span> <span class="numeric">1732584193</span><span class="symbol">;</span>
 <span class="reserved_word">var</span> b <span class="symbol">=</span> -<span class="numeric">271733879</span><span class="symbol">;</span>
 <span class="reserved_word">var</span> c <span class="symbol">=</span> -<span class="numeric">1732584194</span><span class="symbol">;</span>
 <span class="reserved_word">var</span> d <span class="symbol">=</span> <span class="numeric">271733878</span><span class="symbol">;</span>
 <span class="reserved_word">var</span> e <span class="symbol">=</span> -<span class="numeric">1009589776</span><span class="symbol">;</span>

 <span class="reserved_word">for</span><span class="braces">(</span><span class="reserved_word">var</span> i <span class="symbol">=</span> <span class="numeric">0</span><span class="symbol">;</span> i <span class="symbol"> x.<span class="predefined_identifier">length</span><span class="symbol">;</span> i +<span class="symbol">=</span> <span class="numeric">16</span><span class="braces">)</span>
 <span class="braces">{</span>
  <span class="reserved_word">var</span> olda <span class="symbol">=</span> a<span class="symbol">;</span>
  <span class="reserved_word">var</span> oldb <span class="symbol">=</span> b<span class="symbol">;</span>
  <span class="reserved_word">var</span> oldc <span class="symbol">=</span> c<span class="symbol">;</span>
  <span class="reserved_word">var</span> oldd <span class="symbol">=</span> d<span class="symbol">;</span>
  <span class="reserved_word">var</span> olde <span class="symbol">=</span> e<span class="symbol">;</span>

  <span class="reserved_word">for</span><span class="braces">(</span><span class="reserved_word">var</span> j <span class="symbol">=</span> <span class="numeric">0</span><span class="symbol">;</span> j <span class="symbol"> <span class="numeric">80</span><span class="symbol">;</span> j++<span class="braces">)</span>
  <span class="braces">{</span>
   <span class="reserved_word">if</span><span class="braces">(</span>j <span class="symbol"> <span class="numeric">16</span><span class="braces">)</span> w[j] <span class="symbol">=</span> x[i + j]<span class="symbol">;</span>
   <span class="reserved_word">else</span> w[j] <span class="symbol">=</span> rol<span class="braces">(</span>w[j-<span class="numeric">3</span>] ^ w[j-<span class="numeric">8</span>] ^ w[j-<span class="numeric">14</span>] ^ w[j-<span class="numeric">16</span>], <span class="numeric">1</span><span class="braces">)</span><span class="symbol">;</span>
   <span class="reserved_word">var</span> t <span class="symbol">=</span> safe_add<span class="braces">(</span>safe_add<span class="braces">(</span>rol<span class="braces">(</span>a, <span class="numeric">5</span><span class="braces">)</span>, sha1_ft<span class="braces">(</span>j, b, c, d<span class="braces">)</span><span class="braces">)</span>,
            safe_add<span class="braces">(</span>safe_add<span class="braces">(</span>e, w[j]<span class="braces">)</span>, sha1_kt<span class="braces">(</span>j<span class="braces">)</span><span class="braces">)</span><span class="braces">)</span><span class="symbol">;</span>
   e <span class="symbol">=</span> d<span class="symbol">;</span>
   d <span class="symbol">=</span> c<span class="symbol">;</span>
   c <span class="symbol">=</span> rol<span class="braces">(</span>b, <span class="numeric">30</span><span class="braces">)</span><span class="symbol">;</span>
   b <span class="symbol">=</span> a<span class="symbol">;</span>
   a <span class="symbol">=</span> t<span class="symbol">;</span>
  <span class="braces">}</span>

  a <span class="symbol">=</span> safe_add<span class="braces">(</span>a, olda<span class="braces">)</span><span class="symbol">;</span>
  b <span class="symbol">=</span> safe_add<span class="braces">(</span>b, oldb<span class="braces">)</span><span class="symbol">;</span>
  c <span class="symbol">=</span> safe_add<span class="braces">(</span>c, oldc<span class="braces">)</span><span class="symbol">;</span>
  d <span class="symbol">=</span> safe_add<span class="braces">(</span>d, oldd<span class="braces">)</span><span class="symbol">;</span>
  e <span class="symbol">=</span> safe_add<span class="braces">(</span>e, olde<span class="braces">)</span><span class="symbol">;</span>
 <span class="braces">}</span>
 <span class="reserved_word">return</span> <span class="predefined_type">Array</span><span class="braces">(</span>a, b, c, d, e<span class="braces">)</span><span class="symbol">;</span>

<span class="braces">}</span>

<span class="comment">/*
 * Perform the appropriate triplet combination function for the current
 * iteration
 */</span>
<span class="reserved_word">function</span> sha1_ft<span class="braces">(</span>t, b, c, d<span class="braces">)</span>
<span class="braces">{</span>
 <span class="reserved_word">if</span><span class="braces">(</span>t <span class="symbol"> <span class="numeric">20</span><span class="braces">)</span> <span class="reserved_word">return</span> <span class="braces">(</span>b <span class="symbol">&</span> c<span class="braces">)</span> <span class="symbol">|</span> <span class="braces">(</span><span class="braces">(</span>~b<span class="braces">)</span> <span class="symbol">&</span> d<span class="braces">)</span><span class="symbol">;</span>
 <span class="reserved_word">if</span><span class="braces">(</span>t <span class="symbol"> <span class="numeric">40</span><span class="braces">)</span> <span class="reserved_word">return</span> b ^ c ^ d<span class="symbol">;</span>
 <span class="reserved_word">if</span><span class="braces">(</span>t <span class="symbol"> <span class="numeric">60</span><span class="braces">)</span> <span class="reserved_word">return</span> <span class="braces">(</span>b <span class="symbol">&</span> c<span class="braces">)</span> <span class="symbol">|</span> <span class="braces">(</span>b <span class="symbol">&</span> d<span class="braces">)</span> <span class="symbol">|</span> <span class="braces">(</span>c <span class="symbol">&</span> d<span class="braces">)</span><span class="symbol">;</span>
 <span class="reserved_word">return</span> b ^ c ^ d<span class="symbol">;</span>
<span class="braces">}</span>

<span class="comment">/*
 * Determine the appropriate additive constant for the current iteration
 */</span>
<span class="reserved_word">function</span> sha1_kt<span class="braces">(</span>t<span class="braces">)</span>
<span class="braces">{</span>
 <span class="reserved_word">return</span> <span class="braces">(</span>t <span class="symbol"> <span class="numeric">20</span><span class="braces">)</span> ? <span class="numeric">1518500249</span> : <span class="braces">(</span>t <span class="symbol"> <span class="numeric">40</span><span class="braces">)</span> ? <span class="numeric">1859775393</span> :
     <span class="braces">(</span>t <span class="symbol"> <span class="numeric">60</span><span class="braces">)</span> ? -<span class="numeric">1894007588</span> : -<span class="numeric">899497514</span><span class="symbol">;</span>
<span class="braces">}</span>

<span class="comment">/*
 * Calculate the HMAC-SHA1 of a key and some data
 */</span>
<span class="reserved_word">function</span> core_hmac_sha1<span class="braces">(</span>key, data<span class="braces">)</span>
<span class="braces">{</span>
 <span class="reserved_word">var</span> bkey <span class="symbol">=</span> str2binb<span class="braces">(</span>key<span class="braces">)</span><span class="symbol">;</span>
 <span class="reserved_word">if</span><span class="braces">(</span>bkey.<span class="predefined_identifier">length</span> <span class="symbol">></span> <span class="numeric">16</span><span class="braces">)</span> bkey <span class="symbol">=</span> core_sha1<span class="braces">(</span>bkey, key.<span class="predefined_identifier">length</span> * chrsz<span class="braces">)</span><span class="symbol">;</span>

 <span class="reserved_word">var</span> ipad <span class="symbol">=</span> <span class="predefined_type">Array</span><span class="braces">(</span><span class="numeric">16</span><span class="braces">)</span>, opad <span class="symbol">=</span> <span class="predefined_type">Array</span><span class="braces">(</span><span class="numeric">16</span><span class="braces">)</span><span class="symbol">;</span>
 <span class="reserved_word">for</span><span class="braces">(</span><span class="reserved_word">var</span> i <span class="symbol">=</span> <span class="numeric">0</span><span class="symbol">;</span> i <span class="symbol"> <span class="numeric">16</span><span class="symbol">;</span> i++<span class="braces">)</span>
 <span class="braces">{</span>
  ipad[i] <span class="symbol">=</span> bkey[i] ^ <span class="numeric">0x36363636</span><span class="symbol">;</span>
  opad[i] <span class="symbol">=</span> bkey[i] ^ <span class="numeric">0x5C5C5C5C</span><span class="symbol">;</span>
 <span class="braces">}</span>

 <span class="reserved_word">var</span> <span class="predefined_identifier">hash</span> <span class="symbol">=</span> core_sha1<span class="braces">(</span>ipad.concat<span class="braces">(</span>str2binb<span class="braces">(</span>data<span class="braces">)</span><span class="braces">)</span>, <span class="numeric">512</span> + data.<span class="predefined_identifier">length</span> * chrsz<span class="braces">)</span><span class="symbol">;</span>
 <span class="reserved_word">return</span> core_sha1<span class="braces">(</span>opad.concat<span class="braces">(</span><span class="predefined_identifier">hash</span><span class="braces">)</span>, <span class="numeric">512</span> + <span class="numeric">160</span><span class="braces">)</span><span class="symbol">;</span>
<span class="braces">}</span>

<span class="comment">/*
 * Add integers, wrapping at 2^32. This uses 16-bit operations internally
 * to work around bugs in some JS interpreters.
 */</span>
<span class="reserved_word">function</span> safe_add<span class="braces">(</span>x, y<span class="braces">)</span>
<span class="braces">{</span>
 <span class="reserved_word">var</span> lsw <span class="symbol">=</span> <span class="braces">(</span>x <span class="symbol">&</span> <span class="numeric">0xFFFF</span><span class="braces">)</span> + <span class="braces">(</span>y <span class="symbol">&</span> <span class="numeric">0xFFFF</span><span class="braces">)</span><span class="symbol">;</span>
 <span class="reserved_word">var</span> msw <span class="symbol">=</span> <span class="braces">(</span>x <span class="symbol">></span><span class="symbol">></span> <span class="numeric">16</span><span class="braces">)</span> + <span class="braces">(</span>y <span class="symbol">></span><span class="symbol">></span> <span class="numeric">16</span><span class="braces">)</span> + <span class="braces">(</span>lsw <span class="symbol">></span><span class="symbol">></span> <span class="numeric">16</span><span class="braces">)</span><span class="symbol">;</span>
 <span class="reserved_word">return</span> <span class="braces">(</span>msw <span class="symbol"><span class="symbol"> <span class="numeric">16</span><span class="braces">)</span> <span class="symbol">|</span> <span class="braces">(</span>lsw <span class="symbol">&</span> <span class="numeric">0xFFFF</span><span class="braces">)</span><span class="symbol">;</span>
<span class="braces">}</span>

<span class="comment">/*
 * Bitwise rotate a 32-bit number to the left.
 */</span>
<span class="reserved_word">function</span> rol<span class="braces">(</span>num, cnt<span class="braces">)</span>
<span class="braces">{</span>
 <span class="reserved_word">return</span> <span class="braces">(</span>num <span class="symbol"><span class="symbol"> cnt<span class="braces">)</span> <span class="symbol">|</span> <span class="braces">(</span>num <span class="symbol">></span><span class="symbol">></span><span class="symbol">></span> <span class="braces">(</span><span class="numeric">32</span> - cnt<span class="braces">)</span><span class="braces">)</span><span class="symbol">;</span>
<span class="braces">}</span>

<span class="comment">/*
 * Convert an 8-bit or 16-bit string to an array of big-endian words
 * In 8-bit function, characters >255 have their hi-byte silently ignored.
 */</span>
<span class="reserved_word">function</span> str2binb<span class="braces">(</span>str<span class="braces">)</span>
<span class="braces">{</span>
 <span class="reserved_word">var</span> bin <span class="symbol">=</span> <span class="predefined_type">Array</span><span class="braces">(</span><span class="braces">)</span><span class="symbol">;</span>
 <span class="reserved_word">var</span> mask <span class="symbol">=</span> <span class="braces">(</span><span class="numeric">1</span> <span class="symbol"><span class="symbol"> chrsz<span class="braces">)</span> - <span class="numeric">1</span><span class="symbol">;</span>
 <span class="reserved_word">for</span><span class="braces">(</span><span class="reserved_word">var</span> i <span class="symbol">=</span> <span class="numeric">0</span><span class="symbol">;</span> i <span class="symbol"> str.<span class="predefined_identifier">length</span> * chrsz<span class="symbol">;</span> i +<span class="symbol">=</span> chrsz<span class="braces">)</span>
  bin[i<span class="symbol">></span><span class="symbol">></span><span class="numeric">5</span>] <span class="symbol">|</span><span class="symbol">=</span> <span class="braces">(</span>str.charCodeAt<span class="braces">(</span>i <span class="symbol">/</span> chrsz<span class="braces">)</span> <span class="symbol">&</span> mask<span class="braces">)</span> <span class="symbol"><span class="symbol"> <span class="braces">(</span><span class="numeric">32</span> - chrsz - i%<span class="numeric">32</span><span class="braces">)</span><span class="symbol">;</span>
 <span class="reserved_word">return</span> bin<span class="symbol">;</span>
<span class="braces">}</span>

<span class="comment">/*
 * Convert an array of big-endian words to a string
 */</span>
<span class="reserved_word">function</span> binb2str<span class="braces">(</span>bin<span class="braces">)</span>
<span class="braces">{</span>
 <span class="reserved_word">var</span> str <span class="symbol">=</span> <span class="string">""</span><span class="symbol">;</span>
 <span class="reserved_word">var</span> mask <span class="symbol">=</span> <span class="braces">(</span><span class="numeric">1</span> <span class="symbol"><span class="symbol"> chrsz<span class="braces">)</span> - <span class="numeric">1</span><span class="symbol">;</span>
 <span class="reserved_word">for</span><span class="braces">(</span><span class="reserved_word">var</span> i <span class="symbol">=</span> <span class="numeric">0</span><span class="symbol">;</span> i <span class="symbol"> bin.<span class="predefined_identifier">length</span> * <span class="numeric">32</span><span class="symbol">;</span> i +<span class="symbol">=</span> chrsz<span class="braces">)</span>
  str +<span class="symbol">=</span> String.fromCharCode<span class="braces">(</span><span class="braces">(</span>bin[i<span class="symbol">></span><span class="symbol">></span><span class="numeric">5</span>] <span class="symbol">></span><span class="symbol">></span><span class="symbol">></span> <span class="braces">(</span><span class="numeric">32</span> - chrsz - i%<span class="numeric">32</span><span class="braces">)</span><span class="braces">)</span> <span class="symbol">&</span> mask<span class="braces">)</span><span class="symbol">;</span>
 <span class="reserved_word">return</span> str<span class="symbol">;</span>
<span class="braces">}</span>

<span class="comment">/*
 * Convert an array of big-endian words to a hex string.
 */</span>
<span class="reserved_word">function</span> binb2hex<span class="braces">(</span>binarray<span class="braces">)</span>
<span class="braces">{</span>
 <span class="reserved_word">var</span> hex_tab <span class="symbol">=</span> hexcase ? <span class="string">"0123456789ABCDEF"</span> : <span class="string">"0123456789abcdef"</span><span class="symbol">;</span>
 <span class="reserved_word">var</span> str <span class="symbol">=</span> <span class="string">""</span><span class="symbol">;</span>
 <span class="reserved_word">for</span><span class="braces">(</span><span class="reserved_word">var</span> i <span class="symbol">=</span> <span class="numeric">0</span><span class="symbol">;</span> i <span class="symbol"> binarray.<span class="predefined_identifier">length</span> * <span class="numeric">4</span><span class="symbol">;</span> i++<span class="braces">)</span>
 <span class="braces">{</span>
  str +<span class="symbol">=</span> hex_tab.<span class="library_function">charAt</span><span class="braces">(</span><span class="braces">(</span>binarray[i<span class="symbol">></span><span class="symbol">></span><span class="numeric">2</span>] <span class="symbol">></span><span class="symbol">></span> <span class="braces">(</span><span class="braces">(</span><span class="numeric">3</span> - i%<span class="numeric">4</span><span class="braces">)</span>*<span class="numeric">8</span>+<span class="numeric">4</span><span class="braces">)</span><span class="braces">)</span> <span class="symbol">&</span> <span class="numeric">0xF</span><span class="braces">)</span> +
      hex_tab.<span class="library_function">charAt</span><span class="braces">(</span><span class="braces">(</span>binarray[i<span class="symbol">></span><span class="symbol">></span><span class="numeric">2</span>] <span class="symbol">></span><span class="symbol">></span> <span class="braces">(</span><span class="braces">(</span><span class="numeric">3</span> - i%<span class="numeric">4</span><span class="braces">)</span>*<span class="numeric">8</span> <span class="braces">)</span><span class="braces">)</span> <span class="symbol">&</span> <span class="numeric">0xF</span><span class="braces">)</span><span class="symbol">;</span>
 <span class="braces">}</span>
 <span class="reserved_word">return</span> str<span class="symbol">;</span>
<span class="braces">}</span>

<span class="comment">/*
 * Convert an array of big-endian words to a base-64 string
 */</span>
<span class="reserved_word">function</span> binb2b64<span class="braces">(</span>binarray<span class="braces">)</span>
<span class="braces">{</span>
 <span class="reserved_word">var</span> tab <span class="symbol">=</span> <span class="string">"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"</span><span class="symbol">;</span>
 <span class="reserved_word">var</span> str <span class="symbol">=</span> <span class="string">""</span><span class="symbol">;</span>
 <span class="reserved_word">for</span><span class="braces">(</span><span class="reserved_word">var</span> i <span class="symbol">=</span> <span class="numeric">0</span><span class="symbol">;</span> i <span class="symbol"> binarray.<span class="predefined_identifier">length</span> * <span class="numeric">4</span><span class="symbol">;</span> i +<span class="symbol">=</span> <span class="numeric">3</span><span class="braces">)</span>
 <span class="braces">{</span>
  <span class="reserved_word">var</span> triplet <span class="symbol">=</span> <span class="braces">(</span><span class="braces">(</span><span class="braces">(</span>binarray[i  <span class="symbol">></span><span class="symbol">></span> <span class="numeric">2</span>] <span class="symbol">></span><span class="symbol">></span> <span class="numeric">8</span> * <span class="braces">(</span><span class="numeric">3</span> - i  %<span class="numeric">4</span><span class="braces">)</span><span class="braces">)</span> <span class="symbol">&</span> <span class="numeric">0xFF</span><span class="braces">)</span> <span class="symbol"><span class="symbol"> <span class="numeric">16</span><span class="braces">)</span>
        <span class="symbol">|</span> <span class="braces">(</span><span class="braces">(</span><span class="braces">(</span>binarray[i+<span class="numeric">1</span> <span class="symbol">></span><span class="symbol">></span> <span class="numeric">2</span>] <span class="symbol">></span><span class="symbol">></span> <span class="numeric">8</span> * <span class="braces">(</span><span class="numeric">3</span> - <span class="braces">(</span>i+<span class="numeric">1</span><span class="braces">)</span>%<span class="numeric">4</span><span class="braces">)</span><span class="braces">)</span> <span class="symbol">&</span> <span class="numeric">0xFF</span><span class="braces">)</span> <span class="symbol"><span class="symbol"> <span class="numeric">8</span> <span class="braces">)</span>
        <span class="symbol">|</span> <span class="braces">(</span><span class="braces">(</span>binarray[i+<span class="numeric">2</span> <span class="symbol">></span><span class="symbol">></span> <span class="numeric">2</span>] <span class="symbol">></span><span class="symbol">></span> <span class="numeric">8</span> * <span class="braces">(</span><span class="numeric">3</span> - <span class="braces">(</span>i+<span class="numeric">2</span><span class="braces">)</span>%<span class="numeric">4</span><span class="braces">)</span><span class="braces">)</span> <span class="symbol">&</span> <span class="numeric">0xFF</span><span class="braces">)</span><span class="symbol">;</span>
  <span class="reserved_word">for</span><span class="braces">(</span><span class="reserved_word">var</span> j <span class="symbol">=</span> <span class="numeric">0</span><span class="symbol">;</span> j <span class="symbol"> <span class="numeric">4</span><span class="symbol">;</span> j++<span class="braces">)</span>
  <span class="braces">{</span>
   <span class="reserved_word">if</span><span class="braces">(</span>i * <span class="numeric">8</span> + j * <span class="numeric">6</span> <span class="symbol">></span> binarray.<span class="predefined_identifier">length</span> * <span class="numeric">32</span><span class="braces">)</span> str +<span class="symbol">=</span> b64pad<span class="symbol">;</span>
   <span class="reserved_word">else</span> str +<span class="symbol">=</span> tab.<span class="library_function">charAt</span><span class="braces">(</span><span class="braces">(</span>triplet <span class="symbol">></span><span class="symbol">></span> <span class="numeric">6</span>*<span class="braces">(</span><span class="numeric">3</span>-j<span class="braces">)</span><span class="braces">)</span> <span class="symbol">&</span> <span class="numeric">0x3F</span><span class="braces">)</span><span class="symbol">;</span>
  <span class="braces">}</span>
 <span class="braces">}</span>
 <span class="reserved_word">return</span> str<span class="symbol">;</span>
<span class="braces">}</span>
</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>