```C /* The tag name of this struct is _IO_FILE to preserve historic C++ mangled names for functions taking FILE* arguments. That name should not be used in new code. */ struct _IO_FILE { int _flags; /* High-order word is _IO_MAGIC; rest is flags. */ /* The following pointers correspond to the C++ streambuf protocol. */ char *_IO_read_ptr; /* Current read pointer */ char *_IO_read_end; /* End of get area. */ char *_IO_read_base; /* Start of putback+get area. */ char *_IO_write_base; /* Start of put area. */ char *_IO_write_ptr; /* Current put pointer. */ char *_IO_write_end; /* End of put area. */ char *_IO_buf_base; /* Start of reserve area. */ char *_IO_buf_end; /* End of reserve area. */ /* The following fields are used to support backing up and undo. */ char *_IO_save_base; /* Pointer to start of non-current get area. */ char *_IO_backup_base; /* Pointer to first valid character of backup area */ char *_IO_save_end; /* Pointer to end of non-current get area. */ struct _IO_marker *_markers; struct _IO_FILE *_chain; int _fileno; int _flags2; __off_t _old_offset; /* This used to be _offset but it's too small. */ /* 1+column number of pbase(); 0 is unknown. */ unsignedshort _cur_column; signedchar _vtable_offset; char _shortbuf[1]; _IO_lock_t *_lock; #ifdef _IO_USE_OLD_IO_FILE };
int _IO_new_file_underflow (FILE *fp) { ssize_t count; /* C99 requires EOF to be "sticky". */ if (fp->_flags & _IO_EOF_SEEN) return EOF; if (fp->_flags & _IO_NO_READS) { fp->_flags |= _IO_ERR_SEEN; __set_errno (EBADF); return EOF; } if (fp->_IO_read_ptr < fp->_IO_read_end) return *(unsignedchar *) fp->_IO_read_ptr; if (fp->_IO_buf_base == NULL) { /* Maybe we already have a push back pointer. */ if (fp->_IO_save_base != NULL) { free (fp->_IO_save_base); fp->_flags &= ~_IO_IN_BACKUP; } _IO_doallocbuf (fp); } /* FIXME This can/should be moved to genops ?? */ if (fp->_flags & (_IO_LINE_BUF|_IO_UNBUFFERED)) { /* We used to flush all line-buffered stream. This really isn't required by any standard. My recollection is that traditional Unix systems did this for stdout. stderr better not be line buffered. So we do just that here explicitly. --drepper */ _IO_acquire_lock (_IO_stdout); if ((_IO_stdout->_flags & (_IO_LINKED | _IO_NO_WRITES | _IO_LINE_BUF)) == (_IO_LINKED | _IO_LINE_BUF)) _IO_OVERFLOW (_IO_stdout, EOF); _IO_release_lock (_IO_stdout); } _IO_switch_to_get_mode (fp); /* This is very tricky. We have to adjust those pointers before we call _IO_SYSREAD () since we may longjump () out while waiting for input. Those pointers may be screwed up. H.J. */ fp->_IO_read_base = fp->_IO_read_ptr = fp->_IO_buf_base; fp->_IO_read_end = fp->_IO_buf_base; fp->_IO_write_base = fp->_IO_write_ptr = fp->_IO_write_end = fp->_IO_buf_base; count = _IO_SYSREAD (fp, fp->_IO_buf_base, fp->_IO_buf_end - fp->_IO_buf_base); if (count <= 0) { if (count == 0) fp->_flags |= _IO_EOF_SEEN; else fp->_flags |= _IO_ERR_SEEN, count = 0; } fp->_IO_read_end += count; if (count == 0) { /* If a stream is read to EOF, the calling application may switch active handles. As a result, our offset cache would no longer be valid, so unset it. */ fp->_offset = _IO_pos_BAD; return EOF; } if (fp->_offset != _IO_pos_BAD) _IO_pos_adjust (fp->_offset, count); return *(unsignedchar *) fp->_IO_read_ptr; }
