Function read_atmost_n

cpp-subprocess/subprocess.hpp:670–696

! * Function: read_atmost_n * Reads at the most `read_upto` bytes from the * file object `fp` before returning. * Parameters: * [in] fp : The file object from which it needs to read. * [in] buf : The buffer into which it needs to write the data. * [in] read_upto: Max number of bytes which must be read from `fd`. * [out] int : Number of bytes written to `buf` or read from `f

   *  reaches 50 after which it will return with whatever data it read.
   */
  static inline
  int read_atmost_n(FILE* fp, char* buf, size_t read_upto)
  {
#ifdef __USING_WINDOWS__
    return (int)fread(buf, 1, read_upto, fp);
#else
    int fd = subprocess_fileno(fp);
    int rbytes = 0;
    int eintr_cnter = 0;

    while (1) {
      int read_bytes = read(fd, buf + rbytes, read_upto - rbytes);
      if (read_bytes == -1) {
        if (errno == EINTR) {
          if (eintr_cnter >= 50) return -1;
          eintr_cnter++;
          continue;
        }
        return -1;
      }
      if (read_bytes == 0) return rbytes;

      rbytes += read_bytes;
    }
    return rbytes;
#endif
  }


  /*!