issue on sizeof()

最新推荐文章于 2024-11-29 16:25:11 发布
原创 最新推荐文章于 2024-11-29 16:25:11 发布 · 692 阅读 · 0 ·
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#struct #include

本文探讨了C语言中结构体的内存对齐问题，通过两个不同成员顺序的结构体示例，展示了成员变量的不同排列如何影响结构体的大小。通过对sizeof运算符结果的分析，可以帮助理解内存对齐原理及其对程序效率的影响。

 

 

 

 

 

sizeof(AType) 应该返回8还是返回5 ？

   5 = sizeof(char)+sizeof(int) = 1 + 4;

 

??????

 

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int hiTrafficTestPacketSet(user_port up, char *rawPacket, char *src_mac, char *dst_mac, char *src_ip, char *dst_ip, UINT16 lenType, UINT8 vlan, UINT32 *packetId) { int rc; int dev = 0; int dstPort = 0; struct in_addr srcIp; struct in_addr dstIp; UINT8 srcMac[MAC_ADDR_SIZE] ={0}; UINT8 dstMac[MAC_ADDR_SIZE] ={0}; UINT8 trafficTestBuf[TOTAL_PKT_LEN] = {0}; GT_U8 *packetDataPtr = (GT_U8 *)trafficTestBuf; if (!UP_IS_VALID(up)) { printf("invalid port: %d", UP_PORT(up)); return ERR_BAD_PARAM; } adPmpUp2Dp(up, &dev, &dstPort); inet_pton(AF_INET, src_ip, &srcIp); inet_pton(AF_INET, dst_ip, &dstIp); str2ether(src_mac, srcMac); str2ether(dst_mac, dstMac); TRAFFIC_TEST_PKT_ETHER_HEADER *ethPtr = NULL; TRAFFIC_TEST_PKT_IP_HEADER *ipPtr = NULL; TRAFFIC_TEST_PKT_UDP_HEADER *udpPtr = NULL; UINT8 *payloadPtr = NULL; ethPtr = (TRAFFIC_TEST_PKT_ETHER_HEADER*)trafficTestBuf; memcpy(ethPtr->dst_mac, &dstMac, MAC_ADDR_SIZE); memcpy(ethPtr->src_mac, &srcMac, MAC_ADDR_SIZE); ethPtr->lenType = htons(lenType); ipPtr = (TRAFFIC_TEST_PKT_IP_HEADER*)(trafficTestBuf + sizeof(TRAFFIC_TEST_PKT_ETHER_HEADER)); memcpy(ipPtr->src_ip, &srcIp, IPv4_SIZE); memcpy(ipPtr->dst_ip, &dstIp, IPv4_SIZE); ipPtr->ver_ihl = 0x45; ipPtr->tos = 0; ipPtr->id = 0; ipPtr->flags_fragOffset = 0x4000; ipPtr->ttl = 64; ipPtr->total_length = htons(0x0058); ipPtr->protocol = 0x11; ipPtr->checkSum = 0; udpPtr = (TRAFFIC_TEST_PKT_UDP_HEADER*)(trafficTestBuf + sizeof(TRAFFIC_TEST_PKT_ETHER_HEADER) + sizeof(TRAFFIC_TEST_PKT_IP_HEADER)); udpPtr->src_port = htons(0x1638); udpPtr->dst_port = htons(0x1638); udpPtr->length = htons(0x0044); udpPtr->checkSum = 0; payloadPtr = (UINT8*)(trafficTestBuf + sizeof(TRAFFIC_TEST_PKT_ETHER_HEADER) + sizeof(TRAFFIC_TEST_PKT_IP_HEADER) + sizeof(TRAFFIC_TEST_PKT_UDP_HEADER)); memcpy(payloadPtr, rawPacket, MAX_PAYLOAD_LEN); rc = hiTrafficPacketSdmaTxPacketSend(vlan, packetDataPtr, TOTAL_PKT_LEN, dstPort, packetId); if(rc != ERR_NO_ERROR) { printf("hiTrafficPacketSdmaTxPacketSend error rc=%d \n",rc); } return ERR_NO_ERROR; } memcpy(payloadPtr, rawPacket, MAX_PAYLOAD_LEN); rc = hiTrafficPacketSdmaTxPacketSend(vlan, packetDataPtr, TOTAL_PKT_LEN, dstPort, packetId);这里修改一下复制负载同样长度，计算整个报文总长度并传入发包函数】、
最新发布
11-05
- First, analyze the issue. - Then propose modification with code snippet. - Explain briefly. - End with related questions. Since the user provided code and specific instruction, my response should ...
还是不行 CN25G(config-dnsproxy-doh)#show DNS over HTTPS (DoH) Configuration =========================================== Global DoH Switch : Enabled ------------------------------------------- Configured DoH Servers: ID Name Status URL ----------------------------------------------------------- 1 zzx on https://test2.com 2 test on test.com =========================================== CN25G(config-dnsproxy-doh)#set 2 % Another server is being edited (ID: 1) % Commit or abort current session first CN25G(config-dnsproxy-doh)#set 1 CN25G(config-dnsproxy-doh-set)# cancel - Cancel the doh set commit - Commit the doh dnsserver - Set doh dnsserver name - Set doh name status - Set doh status end - Return to Privileged EXEC Mode exit - Exit current mode history - Display command history no - Negate command show - Display system information CN25G(config-dnsproxy-doh-set)# CN25G(config-dnsproxy-doh-set)#name test1 % Name updated for server 1: test1 CN25G(config-dnsproxy-doh-set)#commit CN25G(config-dnsproxy-doh-set)#exit CN25G(config-dnsproxy-doh)#show DNS over HTTPS (DoH) Configuration =========================================== Global DoH Switch : Enabled ------------------------------------------- Configured DoH Servers: ID Name Status URL ----------------------------------------------------------- 1 zzx on https://test2.com 2 test on test.com =========================================== STATUS cli_dnsproxy_doh_server_set(cli_env *pCliEnv, const char *id_str) { char buffer[128]; 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// 结构体拷贝 found = true; break; } } // 释放服务器列表 dmDohCfgServerListFree(server_list); if (!found) { snprintf(buffer, sizeof(buffer), "%% Server not found (ID: %u)", id_num); RCC_EXT_WriteStrLine(pCliEnv, buffer); return ERROR; } // 设置编辑状态 s_doh_edit_ctx.in_edit = true; snprintf(buffer, sizeof(buffer), "%% Editing server (ID: %u)", id_num); RCC_EXT_WriteStrLine(pCliEnv, buffer); return OK; } // 提交编辑会话 - 统一处理函数 STATUS cli_dnsproxy_doh_server_set_commit(cli_env *pCliEnv) { char buffer[256]; APPL_ERRCODE ret; // 1. 验证编辑状态 if (!s_doh_edit_ctx.in_edit) { RCC_EXT_WriteStrLine(pCliEnv, "%% No active edit session"); return ERROR; } // 2. 确保ID字段正确设置 CFG_DOH_SERVER_T *ent = &s_doh_edit_ctx.server; snprintf(ent->id, sizeof(ent->id), "%u", s_doh_edit_ctx.server_id); // 3. 调试日志：打印将要保存的配置 snprintf(buffer, sizeof(buffer), "%% Saving config: ID=%s, Name=%s, URL=%s, Status=%s", ent->id, ent->name, ent->server, ent->status); RCC_EXT_WriteStrLine(pCliEnv, buffer); // 4. 调用数据库API ret = dmDohCfgServerSet(ent); if (ret != ERR_NO_ERROR) { snprintf(buffer, sizeof(buffer), "%% Failed to update server (error: 0x%X)", ret); RCC_EXT_WriteStrLine(pCliEnv, buffer); return ERROR; } // 5. 清除编辑状态（关键修复） s_doh_edit_ctx.in_edit = false; // 6. 显示成功消息 snprintf(buffer, sizeof(buffer), "%% Successfully committed changes for server %s", ent->id); RCC_EXT_WriteStrLine(pCliEnv, buffer); return OK; } STATUS cli_dnsproxy_doh_server_set_name(cli_env *pCliEnv, const char *new_name) { // 1. 验证编辑状态 if (!s_doh_edit_ctx.in_edit) { RCC_EXT_WriteStrLine(pCliEnv, "%% No active edit session"); return ERROR; } // 2. 设置新名称 strncpy(s_doh_edit_ctx.server.name, new_name, DNSPROXY_LEN_NAME64-1); s_doh_edit_ctx.server.name[DNSPROXY_LEN_NAME64-1] = '\0'; // 3. 反馈 char buffer[128]; snprintf(buffer, sizeof(buffer), "%% Name updated for server %d: %s", s_doh_edit_ctx.server_id, new_name); RCC_EXT_WriteStrLine(pCliEnv, buffer); return OK; } STATUS cli_dnsproxy_doh_server_set_dnsserver(cli_env *pCliEnv, const char *new_url) { if (!s_doh_edit_ctx.in_edit) { RCC_EXT_WriteStrLine(pCliEnv, "%% No active edit session"); return ERROR; } // URL格式验证 if (strncmp(new_url, "https://", 8) != 0) { RCC_EXT_WriteStrLine(pCliEnv, "%% URL must start with https://"); return ERROR; } strncpy(s_doh_edit_ctx.server.server, new_url, DNSPROXY_LEN_SERVER_URL-1); s_doh_edit_ctx.server.server[DNSPROXY_LEN_SERVER_URL-1] = '\0'; char buffer[128]; snprintf(buffer, sizeof(buffer), "%% Server URL updated for %d: %s", s_doh_edit_ctx.server_id, new_url); RCC_EXT_WriteStrLine(pCliEnv, buffer); return OK; } STATUS cli_dnsproxy_doh_server_set_status(cli_env *pCliEnv, const char *new_status) { if (!s_doh_edit_ctx.in_edit) { RCC_EXT_WriteStrLine(pCliEnv, "%% No active edit session"); return ERROR; } // 扩展状态值验证 const char *valid_status[] = {"on", "off", "enable", "disable", NULL}; bool valid = false; for (int i = 0; valid_status[i] != NULL; i++) { if (strcasecmp(new_status, valid_status[i]) == 0) { valid = true; break; } } if (!valid) { RCC_EXT_WriteStrLine(pCliEnv, "%% Status must be 'on', 'off', 'enable' or 'disable'"); return ERROR; 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