emsdk/upstream/emscripten/test/fs/test_fs_write.c

// Copyright 2016 The Emscripten Authors.  All rights reserved.
// Emscripten is available under two separate licenses, the MIT license and the
// University of Illinois/NCSA Open Source License.  Both these licenses can be
// found in the LICENSE file.

// https://github.com/emscripten-core/emscripten/pull/4705: Test that FS.write() with canOwn=true works.

#include <stdio.h>

#include <emscripten/emscripten.h>

int main() {
  EM_ASM(
    var stream = FS.open('testfile', 'w+');

    var data = new Uint8Array(128);
    var str = "Hello! ";
    stringToUTF8Array(str, data, 0, lengthBytesUTF8(str)+1);
    data = data.subarray(0, lengthBytesUTF8(str));
    FS.write(stream, data, 0, lengthBytesUTF8(str), 0, /*canOwn=*/true);
    var pos = lengthBytesUTF8(str);

    str = '1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890';
    data = new Uint8Array(str.length+1);
    stringToUTF8Array(str, data, 0, lengthBytesUTF8(str)+1);
    FS.write(stream, data, 0, lengthBytesUTF8(str)+1, pos, /*canOwn=*/false);

    FS.close(stream);

    var ex;
    try {
      FS.write(stream, data, 0, lengthBytesUTF8(str)+1, pos, /*canOwn=*/false);
    } catch (err) {
      ex = err;
    }
    assert(ex.name === 'ErrnoError' && ex.errno === 8 /* EBADF */)
  );

  FILE* file = fopen("testfile", "r");
  char* line = NULL;
  size_t n;
  getline(&line, &n, file);
  printf("read %s\n", line);
  free(line);

  return 0;
}