93 lines
3.1 KiB
JavaScript
93 lines
3.1 KiB
JavaScript
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// Lightweight GBK/GB18030 decoder helper
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// Strategy:
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// 1. Prefer native TextDecoder('gb18030'/'gbk') if available
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// 2. Fallback to a reverse table built from utils/ecUnicodeToGBK.js (if present)
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// 3. Final fallback: byte-by-byte ASCII/replace decoding
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function toUint8Array(input) {
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if (!input) return new Uint8Array(0)
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if (input instanceof Uint8Array) return input
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if (input.buffer && input.buffer instanceof ArrayBuffer) return new Uint8Array(input.buffer)
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return new Uint8Array(input)
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}
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let reverseMap = null
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function buildReverseFromTable(table) {
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try {
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const rev = Object.create(null)
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for (let i = 0; i < table.length; i++) {
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const v = table[i]
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if (v) rev[String(v).toUpperCase()] = Number(i)
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}
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return rev
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} catch (e) { return null }
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}
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function decodeWithTable(u8, table) {
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if (!table) return null
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if (!reverseMap) reverseMap = buildReverseFromTable(table)
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if (!reverseMap) return null
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let out = ''
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for (let i = 0; i < u8.length; i++) {
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const b = u8[i]
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if (b <= 0x7F) { out += String.fromCharCode(b); continue }
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const b2 = u8[i + 1]
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if (typeof b2 !== 'number') { out += '\uFFFD'; continue }
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const hex = b.toString(16).padStart(2, '0').toUpperCase() + b2.toString(16).padStart(2, '0').toUpperCase()
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const cp = reverseMap[hex]
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if (cp != null) {
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try { out += String.fromCodePoint(cp) } catch (e) { out += '\uFFFD' }
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} else {
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out += '\uFFFD'
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}
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i += 1
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}
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return out
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}
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function decode(u8in) {
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const u8 = toUint8Array(u8in)
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// 1) Native TextDecoder if environment supports gb18030/gbk
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try {
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if (typeof TextDecoder === 'function') {
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try { return new TextDecoder('gb18030').decode(u8) } catch (e) { /* ignore */ }
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try { return new TextDecoder('gbk').decode(u8) } catch (e) { /* ignore */ }
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}
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} catch (e) { /* ignore */ }
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// 2) Try a local Encoding lib if available (bundles may expose Encoding.convert)
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try {
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const enc = (typeof Encoding !== 'undefined') ? Encoding : (typeof window !== 'undefined' ? window.Encoding : null)
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if (enc && typeof enc.convert === 'function') {
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try { return enc.convert(u8, { to: 'UNICODE', from: 'GB18030', type: 'string' }) } catch (e) { /* ignore */ }
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try { return enc.convert(u8, { to: 'UTF8', from: 'GB18030', type: 'string' }) } catch (e) { /* ignore */ }
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}
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} catch (e) { /* ignore */ }
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// 3) Try building reverse map from project mapping utils (utils/ecUnicodeToGBK.js)
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try {
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const tableMod = require('../utils/ecUnicodeToGBK.js')
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const table = tableMod && (tableMod.table || tableMod.t || tableMod)
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if (table) {
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const s = decodeWithTable(u8, table)
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if (s && s.length) return s
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}
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} catch (e) { /* ignore */ }
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// 4) Final fallback: best-effort ASCII/replace pass
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try {
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let out = ''
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for (let i = 0; i < u8.length; i++) {
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const b = u8[i]
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if (b <= 0x7F) out += String.fromCharCode(b)
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else {
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const b2 = u8[i + 1]
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if (typeof b2 === 'number') { out += '\uFFFD'; i += 1 } else { out += '\uFFFD' }
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}
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}
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return out
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} catch (e) { return '' }
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}
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module.exports = { decode }
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