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1.9 KiB
title, order, status
| title | order | status |
|---|---|---|
| C07. Upload a File as Multipart Form Data | 7 | draft |
When you want to send a file the same way an HTML <input type="file"> does, use multipart form data (multipart/form-data). cpp-httplib offers two APIs — UploadFormDataItems and FormDataProviderItems — and you pick between them based on file size.
Send a small file
Read the file into memory first, then send it. For small files, this is the simplest path.
httplib::Client cli("http://localhost:8080");
std::ifstream ifs("avatar.png", std::ios::binary);
std::string content((std::istreambuf_iterator<char>(ifs)),
std::istreambuf_iterator<char>());
httplib::UploadFormDataItems items = {
{"name", "Alice", "", ""},
{"avatar", content, "avatar.png", "image/png"},
};
auto res = cli.Post("/upload", items);
Each UploadFormData entry is {name, content, filename, content_type}. For plain text fields, leave filename and content_type empty.
Stream a large file
To avoid loading the whole file into memory, use make_file_provider(). It reads the file in chunks as it sends — so even huge files won't blow up your memory footprint.
httplib::Client cli("http://localhost:8080");
httplib::UploadFormDataItems items = {
{"name", "Alice", "", ""},
};
httplib::FormDataProviderItems provider_items = {
httplib::make_file_provider("video", "large-video.mp4", "", "video/mp4"),
};
auto res = cli.Post("/upload", httplib::Headers{}, items, provider_items);
The arguments to make_file_provider() are (form name, file path, file name, content type). Leave the file name empty to use the file path as-is.
Note: You can mix
UploadFormDataItemsandFormDataProviderItemsin the same request. A clean split is: text fields inUploadFormDataItems, files inFormDataProviderItems.
To show upload progress, see C11. Use the progress callback.