feat: add helper to parse multipart/form-data

.eslintrc

@@ -3,6 +3,7 @@
     "eslint-config-unjs"
   ],
   "rules": {
-    "unicorn/no-null": 0
+    "unicorn/no-null": "off",
+    "unicorn/number-literal-case": "off"
   }
 }

README.md

@@ -151,6 +151,7 @@ H3 has concept of compasable utilities that accept `event` (from `eventHandler((
 - `setResponseStatus(event, status)`
 - `getResponseStatus(event)`
 - `getResponseStatusText(event)`
+- `readMultipartFormData(event)`
 
 👉 You can learn more about usage in [JSDocs Documentation](https://www.jsdocs.io/package/h3#package-functions).
 

src/utils/body.ts

@@ -1,7 +1,8 @@
 import destr from "destr";
 import type { Encoding, HTTPMethod } from "../types";
 import type { H3Event } from "../event";
-import { assertMethod } from "./request";
+import { parse as parseMultipartData } from "./multipart";
+import { assertMethod, getRequestHeader } from "./request";
 
 const RawBodySymbol = Symbol.for("h3RawBody");
 const ParsedBodySymbol = Symbol.for("h3ParsedBody");
@@ -102,3 +103,19 @@ export async function readBody<T = any>(event: H3Event): Promise<T> {
   (event.node.req as any)[ParsedBodySymbol] = json;
   return json;
 }
+
+export async function readMultipartFormData(event: H3Event) {
+  const contentType = getRequestHeader(event, "content-type");
+  if (!contentType || !contentType.startsWith("multipart/form-data")) {
+    return;
+  }
+  const boundary = contentType.match(/boundary=([^;]*)(;|$)/i)?.[1];
+  if (!boundary) {
+    return;
+  }
+  const body = await readRawBody(event, false);
+  if (!body) {
+    return;
+  }
+  return parseMultipartData(body, boundary);
+}

src/utils/multipart.ts

@@ -0,0 +1,123 @@
+/**
+Based on:
+  https://github.com/freesoftwarefactory/parse-multipart - MIT License (The Free Software Factory)
+  https://github.com/nachomazzara/parse-multipart-data - a44c95319d09fd7d7ba51e01512567c444b90e14 - Ignacio Mazzara
+ */
+
+export interface MultiPartData {
+  data: Buffer;
+  name?: string;
+  filename?: string;
+  type?: string;
+}
+
+enum ParsingState {
+  INIT,
+  READING_HEADERS,
+  READING_DATA,
+  READING_PART_SEPARATOR,
+}
+
+export function parse(
+  multipartBodyBuffer: Buffer,
+  boundary: string
+): MultiPartData[] {
+  let lastline = "";
+  let state: ParsingState = ParsingState.INIT;
+  let buffer: number[] = [];
+  const allParts: MultiPartData[] = [];
+
+  let currentPartHeaders: [string, string][] = [];
+
+  for (let i = 0; i < multipartBodyBuffer.length; i++) {
+    const prevByte: number | null = i > 0 ? multipartBodyBuffer[i - 1] : null;
+    const currByte: number = multipartBodyBuffer[i];
+
+    // 0x0a => \n | 0x0d => \r
+    const newLineChar: boolean = currByte === 0x0a || currByte === 0x0d;
+    if (!newLineChar) {
+      lastline += String.fromCodePoint(currByte);
+    }
+
+    const newLineDetected: boolean = currByte === 0x0a && prevByte === 0x0d;
+    if (ParsingState.INIT === state && newLineDetected) {
+      // Searching for boundary
+      if ("--" + boundary === lastline) {
+        state = ParsingState.READING_HEADERS; // Found boundary. start reading headers
+      }
+      lastline = "";
+    } else if (ParsingState.READING_HEADERS === state && newLineDetected) {
+      // Parsing headers.
+      // Headers are separated by an empty line from the content.
+      // Stop reading headers when the line is empty
+      if (lastline.length > 0) {
+        const i = lastline.indexOf(":");
+        if (i > 0) {
+          const name = lastline.slice(0, i).toLowerCase();
+          const value = lastline.slice(i + 1).trim();
+          currentPartHeaders.push([name, value]);
+        }
+      } else {
+        // Found empty line.
+        // Reading headers is finished.
+        state = ParsingState.READING_DATA;
+        buffer = [];
+      }
+      lastline = "";
+    } else if (ParsingState.READING_DATA === state) {
+      // Parsing data
+      if (lastline.length > boundary.length + 4) {
+        lastline = ""; // Free memory
+      }
+      if ("--" + boundary === lastline) {
+        const j = buffer.length - lastline.length;
+        const part = buffer.slice(0, j - 1);
+        allParts.push(process(part, currentPartHeaders));
+        buffer = [];
+        currentPartHeaders = [];
+        lastline = "";
+        state = ParsingState.READING_PART_SEPARATOR;
+      } else {
+        buffer.push(currByte);
+      }
+      if (newLineDetected) {
+        lastline = "";
+      }
+    } else if (
+      ParsingState.READING_PART_SEPARATOR === state &&
+      newLineDetected
+    ) {
+      state = ParsingState.READING_HEADERS;
+    }
+  }
+  return allParts;
+}
+
+function process(data: number[], headers: [string, string][]): MultiPartData {
+  const dataObj: Partial<MultiPartData> = {};
+
+  // Meta
+  const contentDispositionHeader =
+    headers.find((h) => h[0] === "content-disposition")?.[1] || "";
+  for (const i of contentDispositionHeader.split(";")) {
+    const s = i.split("=");
+    if (s.length !== 2) {
+      continue;
+    }
+    const key = (s[0] || "").trim();
+    if (key === "name" || key === "filename") {
+      dataObj[key] = (s[1] || "").trim().replace(/"/g, "");
+    }
+  }
+
+  // Type
+  const contentType = headers.find((h) => h[0] === "content-type")?.[1] || "";
+  if (contentType) {
+    dataObj.type = contentType;
+  }
+
+  // Data
+  dataObj.data = Buffer.from(data);
+
+  return dataObj as MultiPartData;
+}

test/body.test.ts

@@ -7,6 +7,7 @@ import {
   readRawBody,
   readBody,
   eventHandler,
+  readMultipartFormData,
 } from "../src";
 
 describe("", () => {
@@ -172,5 +173,40 @@ describe("", () => {
 
       expect(result.text).toBe("200");
     });
+
+    it("parses multipart form data", async () => {
+      app.use(
+        "/",
+        eventHandler(async (request) => {
+          const parts = (await readMultipartFormData(request)) || [];
+          return parts.map((part) => ({
+            ...part,
+            data: part.data.toString("utf8"),
+          }));
+        })
+      );
+      const result = await request
+        .post("/api/test")
+        .set(
+          "content-type",
+          "multipart/form-data; boundary=---------------------------12537827810750053901680552518"
+        )
+        .send(
+          '-----------------------------12537827810750053901680552518\r\nContent-Disposition: form-data; name="baz"\r\n\r\nother\r\n-----------------------------12537827810750053901680552518\r\nContent-Disposition: form-data; name="bar"\r\n\r\nsomething\r\n-----------------------------12537827810750053901680552518--\r\n'
+        );
+
+      expect(result.body).toMatchInlineSnapshot(`
+        [
+          {
+            "data": "other",
+            "name": "baz",
+          },
+          {
+            "data": "something",
+            "name": "bar",
+          },
+        ]
+      `);
+    });
   });
 });