99 lines
2.3 KiB
TypeScript
99 lines
2.3 KiB
TypeScript
import { formatHex } from './formatHex';
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const textDecoder = new TextDecoder('utf-8', { ignoreBOM: true });
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export class MMKVParser {
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private offset = 4;
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private length: number;
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constructor(private view: DataView) {
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const payloadLength = view.getUint32(0, true);
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this.length = 4 + payloadLength;
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// skip unused str
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this.readInt();
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}
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toString() {
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const offset = formatHex(this.offset, 8);
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const length = formatHex(this.length, 8);
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return `<MMKVParser offset=${offset} len=${length}>`;
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}
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get eof() {
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return this.offset >= this.length;
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}
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public readByte() {
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return this.view.getUint8(this.offset++);
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}
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public readBigInt() {
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let value = 0n;
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let shift = 0n;
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let b: number;
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do {
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b = this.readByte();
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value |= BigInt(b & 0x7f) << shift;
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shift += 7n;
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} while ((b & 0x80) !== 0);
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return value;
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}
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public readInt() {
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const value = this.readBigInt();
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if (value > Number.MAX_SAFE_INTEGER) {
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throw new Error('Runtime Error: BigInt too large to cast as number');
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}
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return Number(value);
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}
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public readBytes(n: number) {
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const offset = this.offset;
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const end = offset + n;
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this.offset = end;
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return new Uint8Array(this.view.buffer.slice(offset, end));
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}
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public readString() {
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// String [
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// len: int,
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// data: byte[int], # utf-8
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// ]
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const strByteLen = this.readInt();
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const data = this.readBytes(strByteLen);
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return textDecoder.decode(data).normalize();
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}
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public readVariantString() {
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// Container [
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// len: int,
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// data: variant
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// ]
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const containerLen = this.readInt();
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const newOffset = this.offset + containerLen;
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const result = this.readString();
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if (newOffset !== this.offset) {
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const expected = formatHex(newOffset);
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const actual = formatHex(this.offset);
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throw new Error(`readVariantString failed: offset does mismatch (expect: ${expected}, actual: ${actual})`);
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}
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return result;
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}
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public static toStringMap(view: DataView): Map<string, string> {
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const mmkv = new MMKVParser(view);
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const result = new Map<string, string>();
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while (!mmkv.eof) {
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const key = mmkv.readString();
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const value = mmkv.readVariantString();
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result.set(key, value);
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}
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return result;
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}
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}
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