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// Copyright 2018-2022 the oak authors. All rights reserved. MIT license.
import type { BufReader } from "./buf_reader.ts";import { errors } from "./deps.ts";
const COLON = ":".charCodeAt(0);const HTAB = "\t".charCodeAt(0);const SPACE = " ".charCodeAt(0);
const decoder = new TextDecoder();
/** With a provided attribute pattern, return a RegExp which will match and * capture in the first group the value of the attribute from a header value. */export function toParamRegExp(  attributePattern: string,  flags?: string,): RegExp {  // deno-fmt-ignore  return new RegExp(    `(?:^|;)\\s*${attributePattern}\\s*=\\s*` +    `(` +      `[^";\\s][^;\\s]*` +    `|` +      `"(?:[^"\\\\]|\\\\"?)+"?` +    `)`,    flags  );}
/** Asynchronously read the headers out of body request and resolve with them as * a `Headers` object. */export async function readHeaders(  body: BufReader,): Promise<Record<string, string>> {  const headers: Record<string, string> = {};  let readResult = await body.readLine();  while (readResult) {    const { bytes } = readResult;    if (!bytes.length) {      return headers;    }    let i = bytes.indexOf(COLON);    if (i === -1) {      throw new errors.BadRequest(        `Malformed header: ${decoder.decode(bytes)}`,      );    }    const key = decoder.decode(bytes.subarray(0, i)).trim().toLowerCase();    if (key === "") {      throw new errors.BadRequest("Invalid header key.");    }    i++;    while (i < bytes.byteLength && (bytes[i] === SPACE || bytes[i] === HTAB)) {      i++;    }    const value = decoder.decode(bytes.subarray(i)).trim();    headers[key] = value;    readResult = await body.readLine();  }  throw new errors.BadRequest("Unexpected end of body reached.");}
/** Unquotes attribute values that might be pass as part of a header. */export function unquote(value: string): string {  if (value.startsWith(`"`)) {    const parts = value.slice(1).split(`\\"`);    for (let i = 0; i < parts.length; ++i) {      const quoteIndex = parts[i].indexOf(`"`);      if (quoteIndex !== -1) {        parts[i] = parts[i].slice(0, quoteIndex);        parts.length = i + 1; // Truncates and stops the loop      }      parts[i] = parts[i].replace(/\\(.)/g, "$1");    }    value = parts.join(`"`);  }  return value;}