prime/src/Runtime/direct_io.c

#include <ansi_files.h>
#include <stdio.h>

size_t fwrite(const void* ptr, size_t memb_size, size_t num_memb, FILE* file) {
  size_t retval;
  retval = __fwrite(ptr, memb_size, num_memb, file);
  return (retval);
}

size_t __fwrite(const void* ptr, size_t memb_size, size_t num_memb, FILE* file) {
  unsigned char* write_ptr;
  size_t num_bytes, bytes_to_go, bytes_written;
  int ioresult, always_buffer;

#ifndef __NO_WIDE_CHAR
  if (fwide(file, 0) == 0)
    fwide(file, -1);
#endif

  bytes_to_go = memb_size * num_memb;

  if (!bytes_to_go || file->state.error || file->mode.file_kind == __closed_file)
    return 0;

  if (file->mode.file_kind == __console_file)
    __stdio_atexit();

  always_buffer =
      !file->mode.binary_io || file->mode.buffer_mode == _IOFBF || file->mode.buffer_mode == _IOLBF;

  if (file->state.io_state == __neutral) {
    if (file->mode.io_mode & __write) {
      if (file->mode.io_mode & __append) {
        if (fseek(file, 0, SEEK_END))
          return 0;
      }
      file->state.io_state = __writing;

      __prep_buffer(file);
    }
  }

  if (file->state.io_state != __writing) {
    set_error(file);
    return 0;
  }

  write_ptr = (unsigned char*)ptr;
  bytes_written = 0;

  if (bytes_to_go && (file->buffer_ptr != file->buffer || always_buffer)) {
    file->buffer_len = file->buffer_size - (file->buffer_ptr - file->buffer);

    do {
      unsigned char* newline = NULL;

      num_bytes = file->buffer_len;

      if (num_bytes > bytes_to_go)
        num_bytes = bytes_to_go;
      if (file->mode.buffer_mode == _IOLBF && num_bytes)
        if ((newline = (unsigned char*)__memrchr(write_ptr, '\n', num_bytes)) != NULL)
          num_bytes = newline + 1 - write_ptr;

      if (num_bytes) {
        memcpy(file->buffer_ptr, write_ptr, num_bytes);

        write_ptr += num_bytes;
        bytes_written += num_bytes;
        bytes_to_go -= num_bytes;

        file->buffer_ptr += num_bytes;
        file->buffer_len -= num_bytes;
      }
      if (!file->buffer_len || newline != NULL ||
          (file->mode.buffer_mode == _IONBF))
      {
        ioresult = __flush_buffer(file, NULL);

        if (ioresult) {
          set_error(file);
          bytes_to_go = 0;
          break;
        }
      }
    } while (bytes_to_go && always_buffer);
  }

  if (bytes_to_go && !always_buffer) {
    unsigned char* save_buffer = file->buffer;
    size_t save_size = file->buffer_size;

    file->buffer = write_ptr;
    file->buffer_size = bytes_to_go;
    file->buffer_ptr = write_ptr + bytes_to_go;

    if (__flush_buffer(file, &num_bytes) != __no_io_error)
      set_error(file);

    bytes_written += num_bytes;

    file->buffer = save_buffer;
    file->buffer_size = save_size;

    __prep_buffer(file);

    file->buffer_len = 0;
  }

  if (file->mode.buffer_mode != _IOFBF)
    file->buffer_len = 0;

  return ((bytes_written + memb_size - 1) / memb_size);
}