106 行
2.6 KiB
JavaScript
106 行
2.6 KiB
JavaScript
import File from '@system.file';
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const _this = {
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lookupDict: lookupDict,
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};
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const SEP_ENTRY = "\u001e";
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const SEP_OFFLEN = "\u001f";
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function from94(str) {
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const CHAR_START = 33;
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const BASE = 94;
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let result = 0;
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for (let i = 0; i < str.length; i++) {
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result = result * BASE + (str.charCodeAt(i) - CHAR_START);
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}
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return result;
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}
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/**
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* @param baseDir 字典目录
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* @param key 查找的字符串
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* @param then 回调 (match, key, result)
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*/
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function lookupDict(baseDir, key, then) {
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const searchKey = key.toLowerCase();
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let depth = 0;
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// 记录最长前缀匹配
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let bestMatch = { key: "", off: -1, len: -1, depth: -1 };
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function step(readOff, readLen) {
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File.readText({
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uri: baseDir + "/key" + depth + ".dat",
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position: readOff,
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length: readLen,
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fail: (data, code) => {
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if (bestMatch.off !== -1) {
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readValue(bestMatch.off, bestMatch.len, bestMatch.depth, function (v) {
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then(bestMatch.key, v);
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});
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} else {
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then("", null);
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}
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},
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success: d => {
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const text = d.text;
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const entries = text.split(SEP_ENTRY);
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const targetChar = searchKey[depth];
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for (let i = 0; i < entries.length; i++) {
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const entry = entries[i];
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if (!entry) continue;
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const char = entry[0];
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const parts = entry.substring(1).split(SEP_OFFLEN);
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const vOff = from94(parts[0]);
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const vLen = from94(parts[1]);
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// 处理当前节点的叶子数据 (前缀匹配)
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if (char === "_") {
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bestMatch.key = searchKey.substring(0, depth);
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bestMatch.off = vOff;
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bestMatch.len = vLen;
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bestMatch.depth = depth;
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}
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// 处理通往下一层的路径
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if (char === targetChar) {
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if (depth === searchKey.length) {
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// 精确匹配结束
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break;
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}
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depth++;
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return setTimeout(() => step(vOff, vLen), 0);
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}
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}
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// 没有找到下一层，返回最长匹配
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if (bestMatch.off !== -1) {
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readValue(bestMatch.off, bestMatch.len, bestMatch.depth, function (v) {
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then(bestMatch.key, v);
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});
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} else {
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then("", null);
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}
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}
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});
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}
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function readValue(vPos, vLen, vDepth, callback) {
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File.readText({
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uri: baseDir + "/value" + vDepth + ".dat",
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position: vPos,
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length: vLen,
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fail: function () { callback(null); },
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success: function (data) { callback(data.text); }
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});
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}
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step(0, 1024);
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}
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export default _this; |