diff options
Diffstat (limited to 'libio/fileops.c')
| -rw-r--r-- | libio/fileops.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/libio/fileops.c b/libio/fileops.c index 1851d9a1fa..d3f4831e2d 100644 --- a/libio/fileops.c +++ b/libio/fileops.c @@ -45,21 +45,27 @@ extern int errno; is that of gptr(); in put mode that of pptr(). The position in the buffer that corresponds to the position - in external file system is file_ptr(). - This is normally _IO_read_end, except in putback mode, + in external file system is normally _IO_read_end, except in putback + mode, when it is _IO_save_end. when it is _IO_save_end. If the field _fb._offset is >= 0, it gives the offset in the file as a whole corresponding to eGptr(). (?) PUT MODE: - If a filebuf is in put mode, pbase() is non-NULL and equal to base(). - Also, epptr() == ebuf(). - Also, eback() == gptr() && gptr() == egptr(). - The un-flushed character are those between pbase() and pptr(). + If a filebuf is in put mode, then all of _IO_read_ptr, _IO_read_end, + and _IO_read_base are equal to each other. These are usually equal + to _IO_buf_base, though not necessarily if we have switched from + get mode to put mode. (The reason is to maintain the invariant + that _IO_read_end corresponds to the external file position.) + _IO_write_base is non-NULL and usually equal to _IO_base_base. + We also have _IO_write_end == _IO_buf_end, but only in fully buffered mode. + The un-flushed character are those between _IO_write_base and _IO_write_ptr. + GET MODE: If a filebuf is in get or putback mode, eback() != egptr(). In get mode, the unread characters are between gptr() and egptr(). The OS file position corresponds to that of egptr(). + PUTBACK MODE: Putback mode is used to remember "excess" characters that have been sputbackc'd in a separate putback buffer. @@ -72,7 +78,7 @@ extern int errno; The OS position corresponds to that of save_egptr(). LINE BUFFERED OUTPUT: - During line buffered output, pbase()==base() && epptr()==base(). + During line buffered output, _IO_write_base==base() && epptr()==base(). However, ptr() may be anywhere between base() and ebuf(). This forces a call to filebuf::overflow(int C) on every put. If there is more space in the buffer, and C is not a '\n', |