1 files changed, 190 insertions, 0 deletions
diff --git a/extensions/web/01_mimesniff.js b/extensions/web/01_mimesniff.js
new file mode 100644
index 000000000..b42dd1409
--- /dev/null
+++ b/extensions/web/01_mimesniff.js
@@ -0,0 +1,190 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+// @ts-check
+/// <reference path="../../core/lib.deno_core.d.ts" />
+/// <reference path="../web/internal.d.ts" />
+/// <reference path="../web/lib.deno_web.d.ts" />
+
+"use strict";
+
+((window) => {
+  const {
+    collectSequenceOfCodepoints,
+    HTTP_WHITESPACE,
+    HTTP_WHITESPACE_PREFIX_RE,
+    HTTP_WHITESPACE_SUFFIX_RE,
+    HTTP_QUOTED_STRING_TOKEN_POINT_RE,
+    HTTP_TOKEN_CODE_POINT_RE,
+    collectHttpQuotedString,
+  } = window.__bootstrap.infra;
+
+  /**
+   * @typedef MimeType
+   * @property {string} type
+   * @property {string} subtype
+   * @property {Map<string,string>} parameters
+   */
+
+  /**
+   * @param {string} input
+   * @returns {MimeType | null}
+   */
+  function parseMimeType(input) {
+    // 1.
+    input = input.replaceAll(HTTP_WHITESPACE_PREFIX_RE, "");
+    input = input.replaceAll(HTTP_WHITESPACE_SUFFIX_RE, "");
+
+    // 2.
+    let position = 0;
+    const endOfInput = input.length;
+
+    // 3.
+    const res1 = collectSequenceOfCodepoints(
+      input,
+      position,
+      (c) => c != "\u002F",
+    );
+    const type = res1.result;
+    position = res1.position;
+
+    // 4.
+    if (type === "" || !HTTP_TOKEN_CODE_POINT_RE.test(type)) return null;
+
+    // 5.
+    if (position >= endOfInput) return null;
+
+    // 6.
+    position++;
+
+    // 7.
+    const res2 = collectSequenceOfCodepoints(
+      input,
+      position,
+      (c) => c != "\u003B",
+    );
+    let subtype = res2.result;
+    position = res2.position;
+
+    // 8.
+    subtype = subtype.replaceAll(HTTP_WHITESPACE_SUFFIX_RE, "");
+
+    // 9.
+    if (subtype === "" || !HTTP_TOKEN_CODE_POINT_RE.test(subtype)) return null;
+
+    // 10.
+    const mimeType = {
+      type: type.toLowerCase(),
+      subtype: subtype.toLowerCase(),
+      /** @type {Map<string, string>} */
+      parameters: new Map(),
+    };
+
+    // 11.
+    while (position < endOfInput) {
+      // 11.1.
+      position++;
+
+      // 11.2.
+      const res1 = collectSequenceOfCodepoints(
+        input,
+        position,
+        (c) => HTTP_WHITESPACE.includes(c),
+      );
+      position = res1.position;
+
+      // 11.3.
+      const res2 = collectSequenceOfCodepoints(
+        input,
+        position,
+        (c) => c !== "\u003B" && c !== "\u003D",
+      );
+      let parameterName = res2.result;
+      position = res2.position;
+
+      // 11.4.
+      parameterName = parameterName.toLowerCase();
+
+      // 11.5.
+      if (position < endOfInput) {
+        if (input[position] == "\u003B") continue;
+        position++;
+      }
+
+      // 11.6.
+      if (position >= endOfInput) break;
+
+      // 11.7.
+      let parameterValue = null;
+
+      // 11.8.
+      if (input[position] === "\u0022") {
+        // 11.8.1.
+        const res = collectHttpQuotedString(input, position, true);
+        parameterValue = res.result;
+        position = res.position;
+
+        // 11.8.2.
+        position++;
+      } else { // 11.9.
+        // 11.9.1.
+        const res = collectSequenceOfCodepoints(
+          input,
+          position,
+          (c) => c !== "\u003B",
+        );
+        parameterValue = res.result;
+        position = res.position;
+
+        // 11.9.2.
+        parameterValue = parameterValue.replaceAll(
+          HTTP_WHITESPACE_SUFFIX_RE,
+          "",
+        );
+
+        // 11.9.3.
+        if (parameterValue === "") continue;
+      }
+
+      // 11.10.
+      if (
+        parameterName !== "" && HTTP_TOKEN_CODE_POINT_RE.test(parameterName) &&
+        HTTP_QUOTED_STRING_TOKEN_POINT_RE.test(parameterValue) &&
+        !mimeType.parameters.has(parameterName)
+      ) {
+        mimeType.parameters.set(parameterName, parameterValue);
+      }
+    }
+
+    // 12.
+    return mimeType;
+  }
+
+  /**
+   * @param {MimeType} mimeType
+   * @returns {string}
+   */
+  function essence(mimeType) {
+    return `${mimeType.type}/${mimeType.subtype}`;
+  }
+
+  /**
+   * @param {MimeType} mimeType
+   * @returns {string}
+   */
+  function serializeMimeType(mimeType) {
+    let serialization = essence(mimeType);
+    for (const param of mimeType.parameters) {
+      serialization += `;${param[0]}=`;
+      let value = param[1];
+      if (!HTTP_TOKEN_CODE_POINT_RE.test(value)) {
+        value = value.replaceAll("\\", "\\\\");
+        value = value.replaceAll('"', '\\"');
+        value = `"${value}"`;
+      }
+      serialization += value;
+    }
+    return serialization;
+  }
+
+  window.__bootstrap.mimesniff = { parseMimeType, essence, serializeMimeType };
+})(this);