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53 lines
1.9 KiB
Markdown
53 lines
1.9 KiB
Markdown
---
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title: "C07. Upload a File as Multipart Form Data"
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order: 7
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status: "draft"
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---
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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**.
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## Send a small file
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Read the file into memory first, then send it. For small files, this is the simplest path.
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```cpp
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httplib::Client cli("http://localhost:8080");
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std::ifstream ifs("avatar.png", std::ios::binary);
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std::string content((std::istreambuf_iterator<char>(ifs)),
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std::istreambuf_iterator<char>());
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httplib::UploadFormDataItems items = {
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{"name", "Alice", "", ""},
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{"avatar", content, "avatar.png", "image/png"},
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};
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auto res = cli.Post("/upload", items);
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```
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Each `UploadFormData` entry is `{name, content, filename, content_type}`. For plain text fields, leave `filename` and `content_type` empty.
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## Stream a large file
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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.
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```cpp
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httplib::Client cli("http://localhost:8080");
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httplib::UploadFormDataItems items = {
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{"name", "Alice", "", ""},
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};
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httplib::FormDataProviderItems provider_items = {
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httplib::make_file_provider("video", "large-video.mp4", "", "video/mp4"),
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};
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auto res = cli.Post("/upload", httplib::Headers{}, items, provider_items);
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```
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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.
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> **Note:** You can mix `UploadFormDataItems` and `FormDataProviderItems` in the same request. A clean split is: text fields in `UploadFormDataItems`, files in `FormDataProviderItems`.
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> To show upload progress, see C11. Use the progress callback.
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