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They are based on, and similar to, the <VAR CLASS="LITERAL" >isc_buffer_</VAR > functions in the ISC library.</P ><P >A buffer is a region of memory, together with a set of related subregions. The <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >used region</I ></SPAN > and the <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >available</I ></SPAN > region are disjoint, and their union is the buffer's region. The used region extends from the beginning of the buffer region to the last used byte. The available region extends from one byte greater than the last used byte to the end of the buffer's region. The size of the used region can be changed using various buffer commands. Initially, the used region is empty.</P ><P >The used region is further subdivided into two disjoint regions: the <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >consumed region</I ></SPAN > and the <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >remaining region</I ></SPAN >. The union of these two regions is the used region. The consumed region extends from the beginning of the used region to the byte before the <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >current</I ></SPAN > offset (if any). The <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >remaining</I ></SPAN > region the current pointer to the end of the used region. The size of the consumed region can be changed using various buffer commands. Initially, the consumed region is empty.</P ><P >The <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >active region</I ></SPAN > is an (optional) subregion of the remaining region. It extends from the current offset to an offset in the remaining region. Initially, the active region is empty. If the current offset advances beyond the chosen offset, the active region will also be empty.</P ><P ><PRE CLASS="PROGRAMLISTING" > /------------entire length---------------\\ /----- used region -----\\/-- available --\\ +----------------------------------------+ | consumed | remaining | | +----------------------------------------+ a b c d e a == base of buffer. b == current pointer. Can be anywhere between a and d. c == active pointer. Meaningful between b and d. d == used pointer. e == length of buffer. a-e == entire length of buffer. a-d == used region. a-b == consumed region. b-d == remaining region. b-c == optional active region.</PRE ></P ><P ><CODE CLASS="FUNCTION" >lwres_buffer_init()</CODE > initializes the <SPAN CLASS="TYPE" >lwres_buffer_t</SPAN > <VAR CLASS="PARAMETER" >*b</VAR > and assocates it with the memory region of size <VAR CLASS="PARAMETER" >length</VAR > bytes starting at location <VAR CLASS="PARAMETER" >base.</VAR ></P ><P ><CODE CLASS="FUNCTION" >lwres_buffer_invalidate()</CODE > marks the buffer <VAR CLASS="PARAMETER" >*b</VAR > as invalid. Invalidating a buffer after use is not required, but makes it possible to catch its possible accidental use.</P ><P >The functions <CODE CLASS="FUNCTION" >lwres_buffer_add()</CODE > and <CODE CLASS="FUNCTION" >lwres_buffer_subtract()</CODE > respectively increase and decrease the used space in buffer <VAR CLASS="PARAMETER" >*b</VAR > by <VAR CLASS="PARAMETER" >n</VAR > bytes. <CODE CLASS="FUNCTION" >lwres_buffer_add()</CODE > checks for buffer overflow and <CODE CLASS="FUNCTION" >lwres_buffer_subtract()</CODE > checks for underflow. These functions do not allocate or deallocate memory. They just change the value of <CODE CLASS="STRUCTFIELD" >used</CODE >.</P ><P >A buffer is re-initialised by <CODE CLASS="FUNCTION" >lwres_buffer_clear()</CODE >. The function sets <CODE CLASS="STRUCTFIELD" >used</CODE > , <CODE CLASS="STRUCTFIELD" >current</CODE > and <CODE CLASS="STRUCTFIELD" >active</CODE > to zero.</P ><P ><CODE CLASS="FUNCTION" >lwres_buffer_first</CODE > makes the consumed region of buffer <VAR CLASS="PARAMETER" >*p</VAR > empty by setting <CODE CLASS="STRUCTFIELD" >current</CODE > to zero (the start of the buffer).</P ><P ><CODE CLASS="FUNCTION" >lwres_buffer_forward()</CODE > increases the consumed region of buffer <VAR CLASS="PARAMETER" >*b</VAR > by <VAR CLASS="PARAMETER" >n</VAR > bytes, checking for overflow. Similarly, <CODE CLASS="FUNCTION" >lwres_buffer_back()</CODE > decreases buffer <VAR CLASS="PARAMETER" >b</VAR >'s consumed region by <VAR CLASS="PARAMETER" >n</VAR > bytes and checks for underflow.</P ><P ><CODE CLASS="FUNCTION" >lwres_buffer_getuint8()</CODE > reads an unsigned 8-bit integer from <VAR CLASS="PARAMETER" >*b</VAR > and returns it. <CODE CLASS="FUNCTION" >lwres_buffer_putuint8()</CODE > writes the unsigned 8-bit integer <VAR CLASS="PARAMETER" >val</VAR > to buffer <VAR CLASS="PARAMETER" >*b</VAR >.</P ><P ><CODE CLASS="FUNCTION" >lwres_buffer_getuint16()</CODE > and <CODE CLASS="FUNCTION" >lwres_buffer_getuint32()</CODE > are identical to <CODE CLASS="FUNCTION" >lwres_buffer_putuint8()</CODE > except that they respectively read an unsigned 16-bit or 32-bit integer in network byte order from <VAR CLASS="PARAMETER" >b</VAR >. Similarly, <CODE CLASS="FUNCTION" >lwres_buffer_putuint16()</CODE > and <CODE CLASS="FUNCTION" >lwres_buffer_putuint32()</CODE > writes the unsigned 16-bit or 32-bit integer <VAR CLASS="PARAMETER" >val</VAR > to buffer <VAR CLASS="PARAMETER" >b</VAR >, in network byte order.</P ><P >Arbitrary amounts of data are read or written from a lightweight resolver buffer with <CODE CLASS="FUNCTION" >lwres_buffer_getmem()</CODE > and <CODE CLASS="FUNCTION" >lwres_buffer_putmem()</CODE > respectively. <CODE CLASS="FUNCTION" >lwres_buffer_putmem()</CODE > copies <VAR CLASS="PARAMETER" >length</VAR > bytes of memory at <VAR CLASS="PARAMETER" >base</VAR > to <VAR CLASS="PARAMETER" >b</VAR >. Conversely, <CODE CLASS="FUNCTION" >lwres_buffer_getmem()</CODE > copies <VAR CLASS="PARAMETER" >length</VAR > bytes of memory from <VAR CLASS="PARAMETER" >b</VAR > to <VAR CLASS="PARAMETER" >base</VAR >.</P ></DIV ></BODY ></HTML >