Reference Guide

ZCOM Tables and Data Structures
Data Buffer Pool
Chapter 3106
Data Buffer Pool
The data buffer pool is part of the ZCOM memory structure. The size of
data buffer pool is defined in the TTGEN configuration file. The data
buffer pool is a global resource within the ZCOM subsystem.
Organization of Buffer Pool
The buffer pool is a contiguous block of memory divided dynamically into
a number of variable length buffers. When the ZCOM subsystem is
initialized, the single buffer pool is divided into 2 buffers: one small
dummy buffer which stays in the free queue all the time, and a main
buffer that contain all the remaining free space from the memory block.
The size of the dummy buffer is smaller than the minimum size in buffer
allocation, so it will never be released from the free pool. The two buffers
are linked together in a circular list. This arrangement is to minimize
the updates to the free queue header (see next paragraph), hence the
buffer management code can be more efficient.
The access to the buffer pool memory block is via the free queue header.
The free queue header is the first queue header (header 0). The header
contains a pointer to the first free block, the last free block, and some
statistics that relate to the use of the free pool. These include the number