deno/cli/rt/23_multipart.js

// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.

((window) => {
  const { Buffer } = window.__bootstrap.buffer;
  const { bytesSymbol, Blob } = window.__bootstrap.blob;
  const { DomFile } = window.__bootstrap.domFile;
  const { getHeaderValueParams } = window.__bootstrap.webUtil;

  const decoder = new TextDecoder();
  const encoder = new TextEncoder();
  const CR = "\r".charCodeAt(0);
  const LF = "\n".charCodeAt(0);

  class MultipartBuilder {
    constructor(formData, boundary) {
      this.formData = formData;
      this.boundary = boundary ?? this.#createBoundary();
      this.writer = new Buffer();
    }

    getContentType() {
      return `multipart/form-data; boundary=${this.boundary}`;
    }

    getBody() {
      for (const [fieldName, fieldValue] of this.formData.entries()) {
        if (fieldValue instanceof DomFile) {
          this.#writeFile(fieldName, fieldValue);
        } else this.#writeField(fieldName, fieldValue);
      }

      this.writer.writeSync(encoder.encode(`\r\n--${this.boundary}--`));

      return this.writer.bytes();
    }

    #createBoundary = () => {
      return (
        "----------" +
        Array.from(Array(32))
          .map(() => Math.random().toString(36)[2] || 0)
          .join("")
      );
    };

    #writeHeaders = (headers) => {
      let buf = this.writer.empty() ? "" : "\r\n";

      buf += `--${this.boundary}\r\n`;
      for (const [key, value] of headers) {
        buf += `${key}: ${value}\r\n`;
      }
      buf += `\r\n`;

      this.writer.write(encoder.encode(buf));
    };

    #writeFileHeaders = (
      field,
      filename,
      type,
    ) => {
      const headers = [
        [
          "Content-Disposition",
          `form-data; name="${field}"; filename="${filename}"`,
        ],
        ["Content-Type", type || "application/octet-stream"],
      ];
      return this.#writeHeaders(headers);
    };

    #writeFieldHeaders = (field) => {
      const headers = [["Content-Disposition", `form-data; name="${field}"`]];
      return this.#writeHeaders(headers);
    };

    #writeField = (field, value) => {
      this.#writeFieldHeaders(field);
      this.writer.writeSync(encoder.encode(value));
    };

    #writeFile = (field, value) => {
      this.#writeFileHeaders(field, value.name, value.type);
      this.writer.writeSync(value[bytesSymbol]);
    };
  }

  class MultipartParser {
    constructor(body, boundary) {
      if (!boundary) {
        throw new TypeError("multipart/form-data must provide a boundary");
      }

      this.boundary = `--${boundary}`;
      this.body = body;
      this.boundaryChars = encoder.encode(this.boundary);
    }

    #parseHeaders = (headersText) => {
      const headers = new Headers();
      const rawHeaders = headersText.split("\r\n");
      for (const rawHeader of rawHeaders) {
        const sepIndex = rawHeader.indexOf(":");
        if (sepIndex < 0) {
          continue; // Skip this header
        }
        const key = rawHeader.slice(0, sepIndex);
        const value = rawHeader.slice(sepIndex + 1);
        headers.set(key, value);
      }

      return {
        headers,
        disposition: getHeaderValueParams(
          headers.get("Content-Disposition") ?? "",
        ),
      };
    };

    parse() {
      const formData = new FormData();
      let headerText = "";
      let boundaryIndex = 0;
      let state = 0;
      let fileStart = 0;

      for (let i = 0; i < this.body.length; i++) {
        const byte = this.body[i];
        const prevByte = this.body[i - 1];
        const isNewLine = byte === LF && prevByte === CR;

        if (state === 1 || state === 2 || state == 3) {
          headerText += String.fromCharCode(byte);
        }
        if (state === 0 && isNewLine) {
          state = 1;
        } else if (state === 1 && isNewLine) {
          state = 2;
          const headersDone = this.body[i + 1] === CR &&
            this.body[i + 2] === LF;

          if (headersDone) {
            state = 3;
          }
        } else if (state === 2 && isNewLine) {
          state = 3;
        } else if (state === 3 && isNewLine) {
          state = 4;
          fileStart = i + 1;
        } else if (state === 4) {
          if (this.boundaryChars[boundaryIndex] !== byte) {
            boundaryIndex = 0;
          } else {
            boundaryIndex++;
          }

          if (boundaryIndex >= this.boundary.length) {
            const { headers, disposition } = this.#parseHeaders(headerText);
            const content = this.body.subarray(
              fileStart,
              i - boundaryIndex - 1,
            );
            // https://fetch.spec.whatwg.org/#ref-for-dom-body-formdata
            const filename = disposition.get("filename");
            const name = disposition.get("name");

            state = 5;
            // Reset
            boundaryIndex = 0;
            headerText = "";

            if (!name) {
              continue; // Skip, unknown name
            }

            if (filename) {
              const blob = new Blob([content], {
                type: headers.get("Content-Type") || "application/octet-stream",
              });
              formData.append(name, blob, filename);
            } else {
              formData.append(name, decoder.decode(content));
            }
          }
        } else if (state === 5 && isNewLine) {
          state = 1;
        }
      }

      return formData;
    }
  }

  window.__bootstrap.multipart = {
    MultipartBuilder,
    MultipartParser,
  };
})(this);