61 lines
1.7 KiB
JavaScript
61 lines
1.7 KiB
JavaScript
/* consult README.md for the magic number */
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/* charCodeAt is the best approach for binary strings */
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var use_buffer = typeof Buffer !== 'undefined';
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function adler32_bstr(bstr) {
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if(bstr.length > 32768) if(use_buffer) return adler32_buf(Buffer(bstr));
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var a = 1, b = 0, L = bstr.length, M;
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for(var i = 0; i < L;) {
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M = Math.min(L-i, 3854);
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for(;M>0;--M) {
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a += bstr.charCodeAt(i++);
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b += a;
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}
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a %= 65521;
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b %= 65521;
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}
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return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
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}
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function adler32_buf(buf) {
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var a = 1, b = 0, L = buf.length, M;
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for(var i = 0; i < L;) {
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M = Math.min(L-i, 3854);
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for(;M>0;--M) {
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a += buf[i++];
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b += a;
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}
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a %= 65521;
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b %= 65521;
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}
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return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
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}
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/* much much faster to intertwine utf8 and adler */
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function adler32_str(str) {
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var a = 1, b = 0, L = str.length, M, c, d;
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for(var i = 0; i < L;) {
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M = Math.min(L-i, 3850);
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while(M>0) {
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c = str.charCodeAt(i++);
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if(c < 0x80) { a += c; b += a; --M; }
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else if(c < 0x800) {
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a += 192|((c>>6)&31); b += a; --M;
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a += 128|(c&63); b += a; --M;
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} else if(c >= 0xD800 && c < 0xE000) {
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c = (c&1023)+64; d = str.charCodeAt(i++) & 1023;
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a += 240|((c>>8)&7); b += a; --M;
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a += 128|((c>>2)&63); b += a; --M;
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a += 128|((d>>6)&15)|(c&3); b += a; --M;
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a += 128|(d&63); b += a; --M;
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} else {
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a += 224|((c>>12)&15); b += a; --M;
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a += 128|((c>>6)&63); b += a; --M;
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a += 128|(c&63); b += a; --M;
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}
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}
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a %= 65521;
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b %= 65521;
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}
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return b > 32767 ? (((b - 65536) * 65536) | a) : ((b * 65536) | a);
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}
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