I have an HTML input like this <input type="file" id="myfile" onchange="load_file()">.
I want to load the file into Emscripten's MEMFS file system.
Looking at the Emscripten file API I have been trying to use FS.mount() to do so.
However, the documentation only gives an example of using mount using WORKERFS, so I tried playing around with it like this.
let files = document.getElementById('myfile').files;
let file=files[0];
FS.mount(MEMFS, {files: file },'test');
console.log(FS.readFile('test/' + file.name));
But get a "No such file or directory" error message when I try to read the file.
Any suggestions of where I am going wrong?
I have an HTML input like this <input type="file" id="myfile" onchange="load_file()">.
I want to load the file into Emscripten's MEMFS file system.
Looking at the Emscripten file API I have been trying to use FS.mount() to do so.
However, the documentation only gives an example of using mount using WORKERFS, so I tried playing around with it like this.
let files = document.getElementById('myfile').files;
let file=files[0];
FS.mount(MEMFS, {files: file },'test');
console.log(FS.readFile('test/' + file.name));
But get a "No such file or directory" error message when I try to read the file.
Any suggestions of where I am going wrong?
Share Improve this question asked Apr 29, 2020 at 7:56 Harry O'ConnorHarry O'Connor 1631 silver badge7 bronze badges1 Answer
Reset to default 9Here is what I ended up doing–
input_test.html for file input:
<html>
<body>
<input type="file" id="myfile" onchange="load_file()">
</body>
<script type="text/javascript" src="auto_em.js"></script>
<script type="text/javascript" src="input_test.js"></script>
</html>
input_test.js then reads the file as an ArrayBuffer and then uses a Uint8Array view of that buffer to write the file to Emscripten's MEMFS:
let reader= new FileReader();
function load_file(){
let files = document.getElementById('myfile').files;
let file=files[0];
reader.addEventListener('loadend', print_file);
reader.readAsArrayBuffer(file);
}
function print_file(e){
let result=reader.result;
const uint8_view = new Uint8Array(result);
FS.writeFile('write_test.txt', uint8_view)
Moduleall('print_file', 'number', ['string'], ['write_test.txt'])
}
print_input.cpp to print out file to check it worked:
#include <stdio.h>
extern "C" {
int print_file(char* file_path){
FILE *file = fopen(file_path, "r");
if (!file) {
printf("cannot open file\n");
return 1;
}
while (!feof(file)) {
char c = fgetc(file);
if (c != EOF) {
putchar(c);
}
}
return 0;
}
}
then piled using:
emcc print_input.cpp -o auto_em.js -s "EXPORTED_FUNCTIONS=['_print_file']" -s "EXTRA_EXPORTED_RUNTIME_METHODS=['ccall']" -s FORCE_FILESYSTEM=1