From 4b8881abb499f280f630b6a95f17170d4417c1de Mon Sep 17 00:00:00 2001
From: Marian Buschsieweke <marian.buschsieweke@ovgu.de>
Date: Mon, 14 May 2018 14:01:29 +0200
Subject: [PATCH] gnrc/netif/hdr.h: Optimized structure layout
Reordered struct members to not waste memory due to padding.
Before:
``` C
typedef struct {
uint8_t src_l2addr_len;
uint8_t dst_l2addr_len;
kernel_pid_t if_pid; // <-- 16 bit, is aligned to 16 bit
uint8_t flags;
uint8_t __padding_byte; // <-- Inserted to fulfill padding requirements
int16_t rssi; // <-- 16 bit, is NOT aligned to 16 bit
uint8_t lqi;
uint8_t __padding_byte2;// <-- Inserted to fulfill padding requirements
} gnrc_netif_hdr_t;
```
Now:
``` C
typedef struct {
uint8_t src_l2addr_len;
uint8_t dst_l2addr_len;
kernel_pid_t if_pid; // <-- 16 bit, is aligned to 16 bit
uint8_t flags;
uint8_t lqi;
int16_t rssi; // <-- 16 bit, is aligned to 16 bit
} gnrc_netif_hdr_t;
```
When build for the `bluepill` board, the new layout reduces the size by 2 bytes.
---
sys/include/net/gnrc/netif/hdr.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/sys/include/net/gnrc/netif/hdr.h b/sys/include/net/gnrc/netif/hdr.h
index b4ab577f97..3e6aef7eaa 100644
--- a/sys/include/net/gnrc/netif/hdr.h
+++ b/sys/include/net/gnrc/netif/hdr.h
@@ -85,8 +85,8 @@ typedef struct {
uint8_t dst_l2addr_len; /**< length of l2 destination address in byte */
kernel_pid_t if_pid; /**< PID of network interface */
uint8_t flags; /**< flags as defined above */
- int16_t rssi; /**< rssi of received packet in dBm (optional) */
uint8_t lqi; /**< lqi of received packet (optional) */
+ int16_t rssi; /**< rssi of received packet in dBm (optional) */
} gnrc_netif_hdr_t;
/**
--
GitLab