134 lines
6.7 KiB
C++
134 lines
6.7 KiB
C++
#pragma once
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#include <string>
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#include <string_view>
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#include <emscripten.h>
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#define _EM_JS_INLINE(ret, c_name, js_name, params, code) \
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extern "C" { \
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ret c_name params EM_IMPORT(js_name); \
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EMSCRIPTEN_KEEPALIVE \
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__attribute__((section("em_js"), aligned(1))) inline char __em_js__##js_name[] = \
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#params "<::>" code; \
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}
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#define EM_JS_INLINE(ret, name, params, ...) _EM_JS_INLINE(ret, name, name, params, #__VA_ARGS__)
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namespace emscripten_browser_file {
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/////////////////////////////////// Interface //////////////////////////////////
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using upload_handler = void(*)(std::string const&, std::string const&, std::string_view buffer, void*);
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inline void upload(std::string const &accept_types, upload_handler callback, void *callback_data = nullptr);
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inline void download(std::string const &filename, std::string const &mime_type, std::string_view buffer);
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///////////////////////////////// Implementation ///////////////////////////////
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wmissing-variable-declarations"
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EM_JS_INLINE(void, upload, (char const *accept_types, upload_handler callback, void *callback_data), {
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/// Prompt the browser to open the file selector dialogue, and pass the file to the given handler
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/// Accept-types are in the format ".png,.jpeg,.jpg" as per https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes/accept
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/// Upload handler callback signature is:
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/// void my_handler(std::string const &filename, std::string const &mime_type, std::string_view buffer, void *callback_data = nullptr);
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globalThis["open_file"] = function(e) {
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const file_reader = new FileReader();
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file_reader.onload = (event) => {
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const uint8Arr = new Uint8Array(event.target.result);
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const data_ptr = Module["_malloc"](uint8Arr.length);
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const data_on_heap = new Uint8Array(Module["HEAPU8"].buffer, data_ptr, uint8Arr.length);
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data_on_heap.set(uint8Arr);
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Module["ccall"]('upload_file_return', 'number', ['string', 'string', 'number', 'number', 'number', 'number'], [event.target.filename, event.target.mime_type, data_on_heap.byteOffset, uint8Arr.length, callback, callback_data]);
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Module["_free"](data_ptr);
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};
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file_reader.filename = e.target.files[0].name;
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file_reader.mime_type = e.target.files[0].type;
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file_reader.readAsArrayBuffer(e.target.files[0]);
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};
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var file_selector = document.createElement('input');
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file_selector.setAttribute('type', 'file');
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file_selector.setAttribute('onchange', 'globalThis["open_file"](event)');
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/// The 'cancel' event is fired when the user cancels the currently open dialog.
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/// In this case, the upload handler will get the empty string_view.
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/// See https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/cancel_event
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file_selector.addEventListener('cancel', () => {
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Module["ccall"]('upload_file_return', 'number', ['string', 'string', 'number', 'number', 'number', 'number'], ["", "", 0, 0, callback, callback_data]);
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});
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file_selector.setAttribute('accept', UTF8ToString(accept_types));
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/// file_selector.click() approach doesn't work in Safari (tested with native desktop v. 17.5 and iPhone/iPad simulators).
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/// It seems that the Safari browser limits programmatical clicking in our case.
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/// As a workaround, we create <dialog> where the user manually clicks on <input>.
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var is_safari = /^((?!chrome|android).)*safari/i.test(navigator.userAgent);
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if (is_safari) {
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var dialog = document.createElement('dialog');
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dialog.setAttribute('id', 'EmJsFileDialog');
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var desc = document.createElement('p');
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desc.innerText = 'Please choose a file. Allowed extension(s): ' + UTF8ToString(accept_types);
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dialog.appendChild(desc);
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/// We should recreate <dialog> every call; it is the most natural way to reset input.value.
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/// Otherwise, if the user re-selects the same file, it triggers the 'cancel' event instead of 'onchange'.
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file_selector.setAttribute('onclick', 'var dg = document.getElementById("EmJsFileDialog"); dg.close(); dg.remove()');
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dialog.appendChild(file_selector);
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document.body.append(dialog);
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dialog.showModal();
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} else {
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/// Not a Safari browser, so file_selector.click() is ok.
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file_selector.click();
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}
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});
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#pragma GCC diagnostic pop
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inline void upload(std::string const &accept_types, upload_handler callback, void *callback_data) {
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/// C++ wrapper for javascript upload call
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upload(accept_types.c_str(), callback, callback_data);
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}
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wmissing-variable-declarations"
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EM_JS_INLINE(void, download, (char const *filename, char const *mime_type, void const *b, size_t buffer_size), {
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// Fix copied from: https://github.com/Armchair-Software/emscripten-browser-file/issues/1
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/// Offer a buffer in memory as a file to download, specifying download filename and mime type
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var a = document.createElement('a');
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a.download = UTF8ToString(filename);
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var bufferCopy = new ArrayBuffer(buffer_size);
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var uint8Array = new Uint8Array(bufferCopy);
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uint8Array.set(new Uint8Array(Module["HEAPU8"].buffer, b, buffer_size));
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a.href = URL.createObjectURL(new Blob([uint8Array], {type: UTF8ToString(mime_type)}));
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a.click();
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});
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#pragma GCC diagnostic pop
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inline void download(std::string const &filename, std::string const &mime_type, std::string_view buffer) {
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/// C++ wrapper for javascript download call, accepting a string_view
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download(filename.c_str(), mime_type.c_str(), buffer.data(), buffer.size());
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}
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namespace {
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extern "C" {
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EMSCRIPTEN_KEEPALIVE inline int upload_file_return(char const *filename, char const *mime_type, char *buffer, size_t buffer_size, upload_handler callback, void *callback_data);
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EMSCRIPTEN_KEEPALIVE inline int upload_file_return(char const *filename, char const *mime_type, char *buffer, size_t buffer_size, upload_handler callback, void *callback_data) {
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/// Load a file - this function is called from javascript when the file upload is activated
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/// The file was not uploaded.
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/// We must process this case separately because std::string_view(nullptr, 0) results in UB.
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/// <The behavior is undefined if [s, s + count) is not a valid range
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/// (even though the constructor may not access any of the elements of this range)>
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/// https://en.cppreference.com/w/cpp/string/basic_string_view/basic_string_view
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if (! buffer || buffer_size == 0) {
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callback(filename, mime_type, std::string_view(), callback_data);
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return 1;
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}
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/// Ok
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callback(filename, mime_type, {buffer, buffer_size}, callback_data);
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return 1;
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}
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}
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}
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}
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