/* Backup the end of the pool pointer and build the pre-allocated block.
内存池最后一块,最后4字节存储TX_BYTE_BLOCK_ALLOC */
block_ptr = TX_UCHAR_POINTER_SUB_USER(block_ptr, (sizeof(ALIGN_TYPE)));
/* Cast the pool pointer into a ULONG. */
temp_ptr = TX_BYTE_POOL_TO_UCHAR_POINTER_CONVERT_USER(pool_ptr);
block_indirect_ptr = TX_UCHAR_TO_INDIRECT_UCHAR_POINTER_CONVERT_USER(block_ptr);
*block_indirect_ptr = temp_ptr;