| | import type { StringReader, StringWriter } from './strings'; |
| |
|
| | export const comma = ','.charCodeAt(0); |
| | export const semicolon = ';'.charCodeAt(0); |
| |
|
| | const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'; |
| | const intToChar = new Uint8Array(64); |
| | const charToInt = new Uint8Array(128); |
| |
|
| | for (let i = 0; i < chars.length; i++) { |
| | const c = chars.charCodeAt(i); |
| | intToChar[i] = c; |
| | charToInt[c] = i; |
| | } |
| |
|
| | export function decodeInteger(reader: StringReader, relative: number): number { |
| | let value = 0; |
| | let shift = 0; |
| | let integer = 0; |
| |
|
| | do { |
| | const c = reader.next(); |
| | integer = charToInt[c]; |
| | value |= (integer & 31) << shift; |
| | shift += 5; |
| | } while (integer & 32); |
| |
|
| | const shouldNegate = value & 1; |
| | value >>>= 1; |
| |
|
| | if (shouldNegate) { |
| | value = -0x80000000 | -value; |
| | } |
| |
|
| | return relative + value; |
| | } |
| |
|
| | export function encodeInteger(builder: StringWriter, num: number, relative: number): number { |
| | let delta = num - relative; |
| |
|
| | delta = delta < 0 ? (-delta << 1) | 1 : delta << 1; |
| | do { |
| | let clamped = delta & 0b011111; |
| | delta >>>= 5; |
| | if (delta > 0) clamped |= 0b100000; |
| | builder.write(intToChar[clamped]); |
| | } while (delta > 0); |
| |
|
| | return num; |
| | } |
| |
|
| | export function hasMoreVlq(reader: StringReader, max: number) { |
| | if (reader.pos >= max) return false; |
| | return reader.peek() !== comma; |
| | } |
| |
|