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