<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>

Node.js excels at efficient I/O, largely thanks to streams. Streams process data incrementally, avoiding memory overload—ideal for large files, network tasks, and real-time applications. Combining streams with TypeScript's type safety creates a powe

The differences in performance and efficiency between Python and JavaScript are mainly reflected in: 1) As an interpreted language, Python runs slowly but has high development efficiency and is suitable for rapid prototype development; 2) JavaScript is limited to single thread in the browser, but multi-threading and asynchronous I/O can be used to improve performance in Node.js, and both have advantages in actual projects.

JavaScript originated in 1995 and was created by Brandon Ike, and realized the language into C. 1.C language provides high performance and system-level programming capabilities for JavaScript. 2. JavaScript's memory management and performance optimization rely on C language. 3. The cross-platform feature of C language helps JavaScript run efficiently on different operating systems.

JavaScript runs in browsers and Node.js environments and relies on the JavaScript engine to parse and execute code. 1) Generate abstract syntax tree (AST) in the parsing stage; 2) convert AST into bytecode or machine code in the compilation stage; 3) execute the compiled code in the execution stage.

The future trends of Python and JavaScript include: 1. Python will consolidate its position in the fields of scientific computing and AI, 2. JavaScript will promote the development of web technology, 3. Cross-platform development will become a hot topic, and 4. Performance optimization will be the focus. Both will continue to expand application scenarios in their respective fields and make more breakthroughs in performance.

Both Python and JavaScript's choices in development environments are important. 1) Python's development environment includes PyCharm, JupyterNotebook and Anaconda, which are suitable for data science and rapid prototyping. 2) The development environment of JavaScript includes Node.js, VSCode and Webpack, which are suitable for front-end and back-end development. Choosing the right tools according to project needs can improve development efficiency and project success rate.

Yes, the engine core of JavaScript is written in C. 1) The C language provides efficient performance and underlying control, which is suitable for the development of JavaScript engine. 2) Taking the V8 engine as an example, its core is written in C, combining the efficiency and object-oriented characteristics of C. 3) The working principle of the JavaScript engine includes parsing, compiling and execution, and the C language plays a key role in these processes.

JavaScript is at the heart of modern websites because it enhances the interactivity and dynamicity of web pages. 1) It allows to change content without refreshing the page, 2) manipulate web pages through DOMAPI, 3) support complex interactive effects such as animation and drag-and-drop, 4) optimize performance and best practices to improve user experience.


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