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import { crc32 } from "../deps.ts";/** very fast */import { deflateRaw, inflateRaw } from "../zlib/mod.ts";/** slow */// import { deflateRaw, inflateRaw } from "../deflate/mod.ts";
// magic numbers marking this file as GZIPconst ID1 = 0x1F;const ID2 = 0x8B;
const compressionMethods = {  "deflate": 8,};const possibleFlags = {  "FTEXT": 0x01,  "FHCRC": 0x02,  "FEXTRA": 0x04,  "FNAME": 0x08,  "FCOMMENT": 0x10,};// const osMap = {//   "fat": 0, // FAT file system (DOS, OS/2, NT) + PKZIPW 2.50 VFAT, NTFS//   "amiga": 1, // Amiga//   "vmz": 2, // VMS (VAX or Alpha AXP)//   "unix": 3, // Unix//   "vm/cms": 4, // VM/CMS//   "atari": 5, // Atari//   "hpfs": 6, // HPFS file system (OS/2, NT 3.x)//   "macintosh": 7, // Macintosh//   "z-system": 8, // Z-System//   "cplm": 9, // CP/M//   "tops-20": 10, // TOPS-20//   "ntfs": 11, // NTFS file system (NT)//   "qdos": 12, // SMS/QDOS//   "acorn": 13, // Acorn RISC OS//   "vfat": 14, // VFAT file system (Win95, NT)//   "vms": 15, // MVS (code also taken for PRIMOS)//   "beos": 16, // BeOS (BeBox or PowerMac)//   "tandem": 17, // Tandem/NSK//   "theos": 18, // THEOS// };const os = {  "darwin": 3,  "linux": 3,  "windows": 0,};
const osCode = os[Deno.build.os] ?? 255;export const DEFAULT_LEVEL = 6;
function putByte(n: number, arr: number[]) {  arr.push(n & 0xFF);}
// LSB firstfunction putShort(n: number, arr: number[]) {  arr.push(n & 0xFF);  arr.push(n >>> 8);}
// LSB firstexport function putLong(n: number, arr: number[]) {  putShort(n & 0xffff, arr);  putShort(n >>> 16, arr);}
function putString(s: string, arr: number[]) {  for (let i = 0, len = s.length; i < len; i += 1) {    putByte(s.charCodeAt(i), arr);  }}
function readByte(arr: number[]): number {  return arr.shift()!;}
function readShort(arr: number[]) {  return arr.shift()! | (arr.shift()! << 8);}
function readLong(arr: number[]) {  const n1 = readShort(arr);  let n2 = readShort(arr);
  // JavaScript can't handle bits in the position 32  // we'll emulate this by removing the left-most bit (if it exists)  // and add it back in via multiplication, which does work  if (n2 > 32768) {    n2 -= 32768;
    return ((n2 << 16) | n1) + 32768 * Math.pow(2, 16);  }
  return (n2 << 16) | n1;}
function readString(arr: number[]) {  const charArr = [];
  // turn all bytes into chars until the terminating null  while (arr[0] !== 0) {    charArr.push(String.fromCharCode(arr.shift()!));  }
  // throw away terminating null  arr.shift();
  // join all characters into a cohesive string  return charArr.join("");}
function readBytes(arr: number[], n: number) {  const ret = [];  for (let i = 0; i < n; i += 1) {    ret.push(arr.shift());  }  return ret;}
interface Options {  level?: number;  timestamp?: number;  name?: string;}
export function getHeader(  options: Options = {},): Uint8Array {  let flags = 0;  const level: number = options.level ?? DEFAULT_LEVEL;  const out: number[] = [];
  putByte(ID1, out);  putByte(ID2, out);
  putByte(compressionMethods["deflate"], out);
  if (options.name) {    flags |= possibleFlags["FNAME"];  }
  putByte(flags, out);  putLong(options.timestamp ?? Math.floor(Date.now() / 1000), out);
  // put deflate args (extra flags)  if (level === 1) {    // fastest algorithm    putByte(4, out);  } else if (level === 9) {    // maximum compression (fastest algorithm)    putByte(2, out);  } else {    putByte(0, out);  }
  // OS identifier  putByte(osCode, out);
  if (options.name) {    // ignore the directory part    putString(options.name.substring(options.name.lastIndexOf("/") + 1), out);
    // terminating null    putByte(0, out);  }
  return new Uint8Array(out);}
export function gzip(  bytes: Uint8Array,  options: Options = {},): Uint8Array {  let flags = 0;  const level: number = options.level ?? DEFAULT_LEVEL;  const out: number[] = [];
  putByte(ID1, out);  putByte(ID2, out);
  putByte(compressionMethods["deflate"], out);
  if (options.name) {    flags |= possibleFlags["FNAME"];  }
  putByte(flags, out);  putLong(options.timestamp ?? Math.floor(Date.now() / 1000), out);
  // put deflate args (extra flags)  if (level === 1) {    // fastest algorithm    putByte(4, out);  } else if (level === 9) {    // maximum compression (fastest algorithm)    putByte(2, out);  } else {    putByte(0, out);  }
  // OS identifier  putByte(osCode, out);
  if (options.name) {    // ignore the directory part    putString(options.name.substring(options.name.lastIndexOf("/") + 1), out);
    // terminating null    putByte(0, out);  }
  deflateRaw(bytes).forEach(function (byte) {    putByte(byte, out);  });  // import { deflateRaw, inflateRaw } from "../deflate/mod.ts";  // deflateRaw(bytes, level).forEach(function (byte) {  //   putByte(byte, out);  // });
  putLong(parseInt(crc32(bytes), 16), out);  putLong(bytes.length, out);
  return new Uint8Array(out);}
export function gunzip(bytes: Uint8Array): Uint8Array {  const arr = Array.from(bytes);
  checkHeader(arr);
  // give deflate everything but the last 8 bytes  // the last 8 bytes are for the CRC32 checksum and filesize  const res: Uint8Array = inflateRaw(    new Uint8Array(arr.splice(0, arr.length - 8)),  );
  // if (flags & possibleFlags["FTEXT"]) {  //   res = Array.prototype.map.call(res, function (byte) {  //     return String.fromCharCode(byte);  //   }).join("");  // }
  const crc: number = readLong(arr) >>> 0;  if (crc !== parseInt(crc32(res), 16)) {    throw "Checksum does not match";  }
  const size: number = readLong(arr);  if (size !== res.length) {    throw "Size of decompressed file not correct";  }
  return res;}
export function checkHeader(arr: number[]) {  // check the first two bytes for the magic numbers  if (readByte(arr) !== ID1 || readByte(arr) !== ID2) {    throw "Not a GZIP file";  }  if (readByte(arr) !== 8) {    throw "Unsupported compression method";  }
  const flags: number = readByte(arr);  readLong(arr); // mtime  readByte(arr); // xFlags  readByte(arr); // os, throw away
  // just throw away the bytes for now  if (flags & possibleFlags["FEXTRA"]) {    const t: number = readShort(arr);    readBytes(arr, t);  }
  // just throw away for now  if (flags & possibleFlags["FNAME"]) {    readString(arr);  }
  // just throw away for now  if (flags & possibleFlags["FCOMMENT"]) {    readString(arr);  }
  // just throw away for now  if (flags & possibleFlags["FHCRC"]) {    readShort(arr);  }}
export function checkTail(arr: number[]) {  const tail = arr.splice(arr.length - 8);
  const crc32: number = readLong(tail) >>> 0;  const size: number = readLong(tail);
  return {    crc32,    size,  };}