Add HTTPMultipartBuilder and its test.

util/net/http_multipart_builder.h

Index: util/net/http_multipart_builder.h
diff --git a/util/net/http_multipart_builder.h b/util/net/http_multipart_builder.h
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+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_UTIL_NET_HTTP_MULTIPART_BUILDER_H_
+#define CRASHPAD_UTIL_NET_HTTP_MULTIPART_BUILDER_H_
+
+#include <map>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/files/file_path.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace crashpad {
+
+class HTTPBodyStream;
+
+//! \brief This class is used to build a MIME multipart message, conforming to
+//!     RFC 2046, for use as a HTTP request body.
+class HTTPMultipartBuilder {
+ public:
+  HTTPMultipartBuilder();
+  ~HTTPMultipartBuilder();
+
+  //! \brief Sets a `Content-Disposition: form-data` key-value pair.
+  //!
+  //! \param[in] key The key of the form data, specified as the `name` in the
+  //!     multipart message. Any data previously set on this class with this
+  //!     key will be overwritten.
+  //! \param[in] value The value to set at the \a key.
+  void SetFormData(const std::string& key, const std::string& value);
+
+  //! \brief Specifies the file at \a path to have its contents uploaded as
+  //!     multipart data, available at `name` of \a upload_file_name.
+  //!
+  //! \param[in] key The key of the form data, specified as the `name` in the
+  //!     multipart message. Any data previously set on this class with this
+  //!     key will be overwritten.
+  //! \param[in] upload_file_name The `filename` to specify for this multipart
+  //!     data attachment.
+  //! \param[in] path The path of the files whose contents will be uploaded.

[Mark Mentovai, 2014/10/29 21:29:14]

file, singular.

[Robert Sesek, 2014/10/29 21:47:53]

Done.

+  //! \param[in] content_type The `Content-Type` to specify for the attachment.
+  //!     If this is empty, "application/octet-stream" will be used.

[Mark Mentovai, 2014/10/29 21:29:14]

`"application/octet-stream"`

[Robert Sesek, 2014/10/29 21:47:53]

Done.

+  void SetFileAttachment(const std::string& key,
+                         const std::string& upload_file_name,
+                         const base::FilePath& path,
+                         const std::string& content_type);
+
+  //! \brief Generates the HTTPBodyStream for the data currently supplied to
+  //!     the builder.
+  //!
+  //! \return A caller-owned HTTPBodyStream object.
+  scoped_ptr<HTTPBodyStream> GetBodyStream();
+
+  //! \brief Gets the boundary that will be used in GetBodyStream().
+  std::string boundary() const { return boundary_; }

[Mark Mentovai, 2014/10/29 21:29:14]

Either make this getter private, or just omit it altogether, because the only
uses are in the class itself and it has direct access to boundary_.

[Robert Sesek, 2014/10/29 21:47:53]

Per my response on the last round, this will be necessary for setting the
Content-Type header.

+
+ private:
+  struct FileAttachment {
+    std::string filename;
+    std::string content_type;
+    base::FilePath path;
+  };
+
+  // Removes elements from both data maps at the specified |key|, to ensure
+  // uniqueness across the entire HTTP body.
+  void EraseKey(const std::string& key);

[Mark Mentovai, 2014/10/29 21:29:14]

It still seems like we should be able to just use a single map, but we can run
with this for now.

OPTIONAL: I’m just thinking about how to do it with a single map. It could look
like

  class FormFieldPart {
    virtual void AddToHTTPBodyStream(std::vector<HTTPBodyStream*>* streams) = 0;
  };
  class StringFormFieldPart : public FormFieldPart {
    void AddToHTTPBodyStream(std::vector<HTTPBodyStream*>* streams) override {
      // make a stream and add it
    }
  };
  class FileUploadFormFieldPart : public FormFieldPart {
    void AddToHTTPBodyStream(std::vector<HTTPBodyStream*>* streams) override {
      // make streams and add them
    }
  };

Then your one and only map in this class would be std::map<std::string,
FormFieldPart*>. One map, and simpler semantics in this class.

As an alternative to AddToHTTPBodyStream(), you could define the interface as

  scoped_ptr<HTTPBodyStream> GetHTTPBodyStream();

StringFormFieldPart would return a StringHTTPBodyStream. FileUploadFormFieldPart
would return a CompositeHTTPBodyStream. HTTPMultipartBuilder::GetBodyStream()
would return a CompositeHTTPBodyStream that contains both StringHTTPBodyStream
and CompositeHTTPBodyStream objects. That’s kind of cool, actually.

[Robert Sesek, 2014/10/29 21:47:53]

This screams over-abstracted.

+
+  std::string boundary_;
+  std::map<std::string, std::string> form_data_;
+  std::map<std::string, FileAttachment> file_attachments_;
+
+  DISALLOW_COPY_AND_ASSIGN(HTTPMultipartBuilder);
+};
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_NET_HTTP_MULTIPART_BUILDER_H_