forked from mystiq/hydrogen-web
111 lines
3.5 KiB
HTML
111 lines
3.5 KiB
HTML
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<html>
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<head>
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<meta charset="utf-8">
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<style type="text/css">
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pre {
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font-family: monospace;
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display: block;
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white-space: pre;
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font-size: 2em;
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}
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</style>
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</head>
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<body>
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<script type="text/javascript">
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const MIN = 0;
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const MAX = 0xFFFFFFFF;
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function zeropad(a, n) {
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return "0".repeat(n - a.length) + a;
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}
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// const encodeNumber = n => zeropad((n >>> 0).toString(16), 8);
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function encodeNumber(n) {
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const a = (n & 0xFFFF0000) >>> 16;
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const b = (n & 0xFFFF) >>> 0;
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//return zeropad(a.toString(16), 4) + zeropad(b.toString(16), 4);
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return String.fromCharCode(a, b);
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}
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function decodeNumber(s) {
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const a = s.charCodeAt(0);
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const b = s.charCodeAt(1);
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//return `${a.toString(16)} ${b}`;
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return ((a << 16) | b) >>> 0;
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}
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function formatArg(a) {
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if (typeof a === "string") {
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return `"${a}"`;
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}
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if (Array.isArray(a)) {
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return `[${a.map(formatArg)}]`;
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}
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return a+"";
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}
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function cmp(a, b) {
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let value;
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try {
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const result = indexedDB.cmp(encodeNumber(a), encodeNumber(b));
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if (result < 0) {
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value = "a < b";
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} else if (result === 0) {
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value = "a = b";
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} else if (result > 0) {
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value = "a > b";
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}
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} catch(err) {
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value = err.message;
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}
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return `cmp(${formatArg(a)} as ${formatArg(encodeNumber(a))},\n ${formatArg(b)} as ${formatArg(encodeNumber(b))}): ${value}`;
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}
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try {
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const tests = [
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// see https://stackoverflow.com/questions/28413947/space-efficient-way-to-encode-numbers-as-sortable-strings
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// need to encode numbers with base 256 and zero padded at start
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// should still fit in 8 bytes then?
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(cmp) => cmp(9, 100000),
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(cmp) => cmp(1, 2),
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(cmp) => cmp(MIN, 1),
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(cmp) => cmp(MIN, MIN),
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(cmp) => cmp(MIN, MAX),
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(cmp) => cmp(MAX >>> 1, MAX),
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(cmp) => cmp(0x7fffffff, 0xffff7fff),
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(cmp) => cmp(MAX, MAX),
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(cmp) => cmp(MAX - 1, MAX),
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];
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for (const fn of tests) {
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const txt = document.createTextNode(fn(cmp));
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const p = document.createElement("pre");
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p.appendChild(txt);
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document.body.appendChild(p);
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}
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} catch(err) {
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alert(err.message);
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}
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let prev;
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for (let i = MIN; i <= MAX; i += 100) {
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if (decodeNumber(encodeNumber(i)) !== i) {
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document.write(`<p>${i} decodes back to ${decodeNumber(encodeNumber(i))}</p>`);
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break;
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}
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if (typeof prev === "number") {
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if (indexedDB.cmp(encodeNumber(prev), encodeNumber(i)) >= 0) {
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document.write(`<p>${i} <= ${prev}</p>`);
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break;
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}
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}
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prev = i;
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}
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document.write(`<p>check from ${MIN} to ${prev}</p>`);
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</script>
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</body>
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</html>
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