system/lib/wasmfs/wasmfs.cpp

// Copyright 2021 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.
// wasmfs.cpp will implement a new file system that replaces the existing JS filesystem.
// Current Status: Work in Progress.
// See https://github.com/emscripten-core/emscripten/issues/15041.

#include <emscripten/emscripten.h>
#include <emscripten/html5.h>
#include <stdlib.h>
#include <vector>
#include <wasi/api.h>

extern "C" {

static std::vector<char> fd_write_stdstream_buffer;

__wasi_errno_t __wasi_fd_write(
  __wasi_fd_t fd, const __wasi_ciovec_t* iovs, size_t iovs_len, __wasi_size_t* nwritten) {
  // FD 1 = STDOUT and FD 2 = STDERR.
  // Temporary hardcoding of filedescriptor values.
  // TODO: May not want to proxy stderr (fd == 2) to the main thread.
  // This will not show in HTML - a console.warn in a worker is suffficient.
  // This would be a change from the current FS.
  if (fd == 1 || fd == 2) {
    __wasi_size_t num = 0;
    for (size_t i = 0; i < iovs_len; i++) {
      const uint8_t* buf = iovs[i].buf;
      __wasi_size_t len = iovs[i].buf_len;
      for (__wasi_size_t j = 0; j < len; j++) {
        uint8_t current = buf[j];
        if (current == 0 || current == 10) {
          fd_write_stdstream_buffer.push_back('\0'); // for null-terminated C strings
          if (fd == 1) {
            emscripten_console_log(&fd_write_stdstream_buffer[0]);
          } else if (fd == 2) {
            emscripten_console_error(&fd_write_stdstream_buffer[0]);
          }
          fd_write_stdstream_buffer.clear();
        } else {
          fd_write_stdstream_buffer.push_back(current);
        }
      }
      num += len;
    }
    *nwritten = num;
  }
  return 0;
}

__wasi_errno_t __wasi_fd_seek(
  __wasi_fd_t fd, __wasi_filedelta_t offset, __wasi_whence_t whence, __wasi_filesize_t* newoffset) {
  emscripten_console_log("__wasi_fd_seek has been temporarily stubbed and is inert");
  abort();
}

__wasi_errno_t __wasi_fd_close(__wasi_fd_t fd) {
  emscripten_console_log("__wasi_fd_close has been temporarily stubbed and is inert");
  abort();
}

__wasi_errno_t __wasi_fd_read(
  __wasi_fd_t fd, const __wasi_iovec_t* iovs, size_t iovs_len, __wasi_size_t* nread) {
  emscripten_console_log("__wasi_fd_read has been temporarily stubbed and is inert");
  abort();
}
}