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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
import { ValueType } from "./encode.ts";
/** * Decode a value from the MessagePack binary format. * * @example * ```ts * import { decode } from "https://deno.land/std@$STD_VERSION/msgpack/decode.ts"; * * const encoded = Uint8Array.of(1, 2, 3) * * console.log(decode(encoded)) * ``` */export function decode(uint8: Uint8Array) {  const pointer = { consumed: 0 };  const dataView = new DataView(    uint8.buffer,    uint8.byteOffset,    uint8.byteLength,  );  const value = decodeSlice(uint8, dataView, pointer);
  if (pointer.consumed < uint8.length) {    throw new EvalError("Messagepack decode did not consume whole array");  }
  return value;}
function decodeString(  uint8: Uint8Array,  size: number,  pointer: { consumed: number },) {  pointer.consumed += size;  return decoder.decode(    uint8.subarray(pointer.consumed - size, pointer.consumed),  );}
function decodeArray(  uint8: Uint8Array,  dataView: DataView,  size: number,  pointer: { consumed: number },) {  const arr: ValueType[] = [];
  for (let i = 0; i < size; i++) {    const value = decodeSlice(uint8, dataView, pointer);    arr.push(value);  }
  return arr;}
function decodeMap(  uint8: Uint8Array,  dataView: DataView,  size: number,  pointer: { consumed: number },) {  const map: Record<number | string, ValueType> = {};
  for (let i = 0; i < size; i++) {    const key = decodeSlice(uint8, dataView, pointer);    const value = decodeSlice(uint8, dataView, pointer);
    if (typeof key !== "number" && typeof key !== "string") {      throw new EvalError(        "Messagepack decode came across an invalid type for a key of a map",      );    }
    map[key] = value;  }
  return map;}
const decoder = new TextDecoder();
const FIXMAP_BITS = 0b1000_0000;const FIXMAP_MASK = 0b1111_0000;const FIXARRAY_BITS = 0b1001_0000;const FIXARRAY_MASK = 0b1111_0000;const FIXSTR_BITS = 0b1010_0000;const FIXSTR_MASK = 0b1110_0000;
/** * Given a uint8array which contains a msgpack object, * return the value of the object as well as how many bytes * were consumed in obtaining this object */function decodeSlice(  uint8: Uint8Array,  dataView: DataView,  pointer: { consumed: number },): ValueType {  const type = dataView.getUint8(pointer.consumed);  pointer.consumed++;
  if (type <= 0x7f) { // positive fixint - really small positive number    return type;  }
  if ((type & FIXMAP_MASK) === FIXMAP_BITS) { // fixmap - small map    const size = type & ~FIXMAP_MASK;    return decodeMap(uint8, dataView, size, pointer);  }
  if ((type & FIXARRAY_MASK) === FIXARRAY_BITS) { // fixarray - small array    const size = type & ~FIXARRAY_MASK;    return decodeArray(uint8, dataView, size, pointer);  }
  if ((type & FIXSTR_MASK) === FIXSTR_BITS) { // fixstr - small string    const size = type & ~FIXSTR_MASK;    return decodeString(uint8, size, pointer);  }
  if (type >= 0xe0) { // negative fixint - really small negative number    return type - 256;  }
  switch (type) {    case 0xc0: // nil      return null;    case 0xc1: // (never used)      throw new Error(        "Messagepack decode encountered a type that is never used",      );    case 0xc2: // false      return false;    case 0xc3: // true      return true;    case 0xc4: { // bin 8 - small Uint8Array      const length = dataView.getUint8(pointer.consumed);      pointer.consumed++;      const u8 = uint8.subarray(pointer.consumed, pointer.consumed + length);      pointer.consumed += length;      return u8;    }    case 0xc5: { // bin 16 - medium Uint8Array      const length = dataView.getUint16(pointer.consumed);      pointer.consumed += 2;      const u8 = uint8.subarray(pointer.consumed, pointer.consumed + length);      pointer.consumed += length;      return u8;    }    case 0xc6: { // bin 32 - large Uint8Array      const length = dataView.getUint32(pointer.consumed);      pointer.consumed += 4;      const u8 = uint8.subarray(pointer.consumed, pointer.consumed + length);      pointer.consumed += length;      return u8;    }    case 0xc7: // ext 8 - small extension type    case 0xc8: // ext 16 - medium extension type    case 0xc9: // ext 32 - large extension type      throw new Error("ext not implemented yet");    case 0xca: { // float 32      const value = dataView.getFloat32(pointer.consumed);      pointer.consumed += 4;      return value;    }    case 0xcb: { // float 64      const value = dataView.getFloat64(pointer.consumed);      pointer.consumed += 8;      return value;    }    case 0xcc: { // uint 8      const value = dataView.getUint8(pointer.consumed);      pointer.consumed += 1;      return value;    }    case 0xcd: { // uint 16      const value = dataView.getUint16(pointer.consumed);      pointer.consumed += 2;      return value;    }    case 0xce: { // uint 32      const value = dataView.getUint32(pointer.consumed);      pointer.consumed += 4;      return value;    }    case 0xcf: { // uint 64      const value = dataView.getBigUint64(pointer.consumed);      pointer.consumed += 8;      return value;    }    case 0xd0: { // int 8      const value = dataView.getInt8(pointer.consumed);      pointer.consumed += 1;      return value;    }    case 0xd1: { // int 16      const value = dataView.getInt16(pointer.consumed);      pointer.consumed += 2;      return value;    }    case 0xd2: { // int 32      const value = dataView.getInt32(pointer.consumed);      pointer.consumed += 4;      return value;    }    case 0xd3: { // int 64      const value = dataView.getBigInt64(pointer.consumed);      pointer.consumed += 8;      return value;    }    case 0xd4: // fixext 1 - 1 byte extension type    case 0xd5: // fixext 2 - 2 byte extension type    case 0xd6: // fixext 4 - 4 byte extension type    case 0xd7: // fixext 8 - 8 byte extension type    case 0xd8: // fixext 16 - 16 byte extension type      throw new Error("fixext not implemented yet");    case 0xd9: { // str 8 - small string      const length = dataView.getUint8(pointer.consumed);      pointer.consumed += 1;      return decodeString(uint8, length, pointer);    }    case 0xda: { // str 16 - medium string      const length = dataView.getUint16(pointer.consumed);      pointer.consumed += 2;      return decodeString(uint8, length, pointer);    }    case 0xdb: { // str 32 - large string      const length = dataView.getUint32(pointer.consumed);      pointer.consumed += 4;      return decodeString(uint8, length, pointer);    }    case 0xdc: { // array 16 - medium array      const length = dataView.getUint16(pointer.consumed);      pointer.consumed += 2;      return decodeArray(uint8, dataView, length, pointer);    }    case 0xdd: { // array 32 - large array      const length = dataView.getUint32(pointer.consumed);      pointer.consumed += 4;      return decodeArray(uint8, dataView, length, pointer);    }    case 0xde: { // map 16 - medium map      const length = dataView.getUint16(pointer.consumed);      pointer.consumed += 2;      return decodeMap(uint8, dataView, length, pointer);    }    case 0xdf: { // map 32 - large map      const length = dataView.getUint32(pointer.consumed);      pointer.consumed += 4;      return decodeMap(uint8, dataView, length, pointer);    }  }
  // All cases are covered for numbers between 0-255. Typescript isn't smart enough to know that.  throw new Error("Unreachable");}