Add headerParams function

Author: kraih

CHANGELOG.md

@@ -3,10 +3,11 @@
 
 This package strictly follows [Semantic Versioning](https://semver.org).
 
-## v1.6.0 (2022-11-21)
+## v1.6.0 (2022-11-24)
 
 ### Features
 
+  * Added `headerParams`, `headerQuote` and `headerUnquote` functions.
   * Added `removeHook` method to `AsyncHooks` class.
 
 ## v1.5.0 (2022-11-20)

src/util.ts

@@ -32,6 +32,10 @@ const XML_UNESCAPE: Record<string, string> = {
   '#39': "'"
 };
 
+const NAME_RE = new RegExp('[;\\s]*([^=;, ]+)\\s*', 'ys');
+const QUOTED_RE = new RegExp('=\\s*("(?:\\\\\\\\|\\\\"|[^"])*")', 'ys');
+const UNQUOTED_RE = new RegExp('=\\s*([^;, ]*)', 'ys');
+
 /**
  * Safe string that should not be escaped.
  */
@@ -161,6 +165,46 @@ export function escapeRegExp(string: string) {
   return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
 }
 
+/**
+ * Extract HTTP header field parameters until the first comma.
+ */
+export function headerParams(value: string): {params: Record<string, string>; remainder: string} {
+  const params: Record<string, string> = {};
+
+  const sticky = {offset: 0, value};
+  while (value.length > sticky.offset) {
+    const nameMatch = stickyMatch(sticky, NAME_RE);
+    if (nameMatch === null) break;
+    const name = nameMatch[1];
+
+    const quotedMatch = stickyMatch(sticky, QUOTED_RE);
+    if (quotedMatch !== null) {
+      params[name] ??= headerUnquote(quotedMatch[1]);
+      continue;
+    }
+
+    const unquotedMatch = stickyMatch(sticky, UNQUOTED_RE);
+    if (unquotedMatch !== null) params[name] ??= unquotedMatch[1];
+  }
+
+  return {params, remainder: value.slice(sticky.offset)};
+}
+
+/**
+ * Quote HTTP header field parameter.
+ */
+export function headerQuote(value: string): string {
+  return '"' + value.replaceAll('\\', '\\\\').replaceAll('"', '\\"') + '"';
+}
+
+/**
+ * Unquote HTTP header field parameter.
+ */
+export function headerUnquote(value: string): string {
+  if (value.startsWith('"') !== true || value.endsWith('"') !== true) return value;
+  return value.slice(1, -1).replaceAll('\\\\', '\\').replaceAll('\\"', '"');
+}
+
 /**
  * JSON pointers.
  */

test/util.js

@@ -6,6 +6,9 @@ import {
   cssUnescape,
   decodeURIComponentSafe,
   escapeRegExp,
+  headerParams,
+  headerQuote,
+  headerUnquote,
   jsonPointer,
   SafeString,
   stickyMatch,
@@ -56,6 +59,31 @@ t.test('Util', async t => {
     t.end();
   });
 
+  t.test('headerQuote', t => {
+    t.equal(headerQuote('foo; 23 "bar'), '"foo; 23 \\"bar"');
+    t.equal(headerQuote('"foo; 23 "bar"'), '"\\"foo; 23 \\"bar\\""');
+    t.end();
+  });
+
+  t.test('headerUnquote', t => {
+    t.equal(headerUnquote('foo"bar"'), 'foo"bar"');
+    t.equal(headerUnquote('"foo 23 \\"bar"'), 'foo 23 "bar');
+    t.equal(headerUnquote('"\\"foo 23 \\"bar\\""'), '"foo 23 "bar"');
+    t.end();
+  });
+
+  t.test('headerParams', t => {
+    t.same(headerParams(''), {params: {}, remainder: ''});
+    t.same(headerParams('foo=b=a=r'), {params: {foo: 'b=a=r'}, remainder: ''});
+    t.same(headerParams('a=b; c, d=e'), {params: {a: 'b'}, remainder: ', d=e'});
+    t.same(headerParams('a=b; a=c'), {params: {a: 'b'}, remainder: ''});
+    t.same(headerParams('a=b; a="c"'), {params: {a: 'b'}, remainder: ''});
+    t.same(headerParams('a=b; b="c=d"'), {params: {a: 'b', b: 'c=d'}, remainder: ''});
+    t.same(headerParams('a=b, c=d'), {params: {a: 'b'}, remainder: ', c=d'});
+    t.same(headerParams(`rel="x"; t*=UTF-8'de'a%20b`), {params: {rel: 'x', 't*': "UTF-8'de'a%20b"}, remainder: ''});
+    t.end();
+  });
+
   t.test('decodeURIComponentSafe', t => {
     const decode = decodeURIComponentSafe;
     t.same(decode('%E0%A4%A'), null);