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55 lines
1.4 KiB
55 lines
1.4 KiB
1 week ago
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// Simple hash function, from: http://burtleburtle.net/bob/hash/integer.html.
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// Chosen because it doesn't use multiply and achieves full avalanche.
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exports.hashU32 = function hashU32 (a) {
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a = a | 0;
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a = a + 2127912214 + (a << 12) | 0;
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a = a ^ -949894596 ^ a >>> 19;
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a = a + 374761393 + (a << 5) | 0;
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a = a + -744332180 ^ a << 9;
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a = a + -42973499 + (a << 3) | 0;
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return a ^ -1252372727 ^ a >>> 16 | 0;
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};
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// Reads a 64-bit little-endian integer from an array.
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exports.readU64 = function readU64 (b, n) {
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var x = 0;
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x |= b[n++] << 0;
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x |= b[n++] << 8;
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x |= b[n++] << 16;
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x |= b[n++] << 24;
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x |= b[n++] << 32;
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x |= b[n++] << 40;
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x |= b[n++] << 48;
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x |= b[n++] << 56;
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return x;
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};
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// Reads a 32-bit little-endian integer from an array.
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exports.readU32 = function readU32 (b, n) {
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var x = 0;
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x |= b[n++] << 0;
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x |= b[n++] << 8;
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x |= b[n++] << 16;
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x |= b[n++] << 24;
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return x;
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};
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// Writes a 32-bit little-endian integer from an array.
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exports.writeU32 = function writeU32 (b, n, x) {
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b[n++] = (x >> 0) & 0xff;
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b[n++] = (x >> 8) & 0xff;
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b[n++] = (x >> 16) & 0xff;
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b[n++] = (x >> 24) & 0xff;
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};
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// Multiplies two numbers using 32-bit integer multiplication.
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// Algorithm from Emscripten.
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exports.imul = function imul (a, b) {
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var ah = a >>> 16;
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var al = a & 65535;
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var bh = b >>> 16;
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var bl = b & 65535;
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return al * bl + (ah * bl + al * bh << 16) | 0;
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};
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