本文共 61237 字，大约阅读时间需要 204 分钟。

00. 目录

01. modbus-private.h文件

libmodbus内部使用的结构和函数的声明

/* * Copyright © 2010-2012 Stéphane Raimbault 
   
     * * SPDX-License-Identifier: LGPL-2.1-or-later */#ifndef MODBUS_PRIVATE_H#define MODBUS_PRIVATE_H#ifndef _MSC_VER# include 
    
     # include 
     
      #else# include "stdint.h"# include 
      
       typedef int ssize_t;#endif#include 
       
        #include 
        
         #include "modbus.h"MODBUS_BEGIN_DECLS/* It's not really the minimal length (the real one is report slave ID * in RTU (4 bytes)) but it's a convenient size to use in RTU or TCP * communications to read many values or write a single one. * Maximum between : * - HEADER_LENGTH_TCP (7) + function (1) + address (2) + number (2) * - HEADER_LENGTH_RTU (1) + function (1) + address (2) + number (2) + CRC (2) */#define _MIN_REQ_LENGTH 12#define _REPORT_SLAVE_ID 180#define _MODBUS_EXCEPTION_RSP_LENGTH 5/* Timeouts in microsecond (0.5 s) */#define _RESPONSE_TIMEOUT 500000#define _BYTE_TIMEOUT 500000typedef enum { _MODBUS_BACKEND_TYPE_RTU=0, _MODBUS_BACKEND_TYPE_TCP} modbus_backend_type_t;/* * ---------- Request Indication ---------- * | Client | ---------------------->| Server | * ---------- Confirmation Response ---------- */typedef enum { /* Request message on the server side */ MSG_INDICATION, /* Request message on the client side */ MSG_CONFIRMATION} msg_type_t;/* This structure reduces the number of params in functions and so * optimizes the speed of execution (~ 37%). */typedef struct _sft { int slave; int function; int t_id;} sft_t;typedef struct _modbus_backend { unsigned int backend_type; //modbus_backend_type_t类型 unsigned int header_length; //HBMP长度 unsigned int checksum_length; //错误校验字段长度 unsigned int max_adu_length; //ADU最大长度 int (*set_slave) (modbus_t *ctx, int slave); //设置从站设备地址 //构造查询报文的基本通信帧 int (*build_request_basis) (modbus_t *ctx, int function, int addr, int nb, uint8_t *req); //构造响应报文的基本通信帧 int (*build_response_basis) (sft_t *sft, uint8_t *rsp); //构造响应报文TID参数 int (*prepare_response_tid) (const uint8_t *req, int *req_length); //发送报文前的预处理 int (*send_msg_pre) (uint8_t *req, int req_length); //发送报文 ssize_t (*send) (modbus_t *ctx, const uint8_t *req, int req_length); //接收报文 int (*receive) (modbus_t *ctx, uint8_t *req); //接收报文 该函数被receive函数调用 ssize_t (*recv) (modbus_t *ctx, uint8_t *rsp, int rsp_length); //用于数据完整性检查 int (*check_integrity) (modbus_t *ctx, uint8_t *msg, const int msg_length); //确认响应报文的帧头是否一致 int (*pre_check_confirmation) (modbus_t *ctx, const uint8_t *req, const uint8_t *rsp, int rsp_length); //建立连接 int (*connect) (modbus_t *ctx); //关闭连接 void (*close) (modbus_t *ctx); //清空缓冲区 int (*flush) (modbus_t *ctx); //用于设置超时并读取通信事件，以检测是否存在待接收数据 int (*select) (modbus_t *ctx, fd_set *rset, struct timeval *tv, int msg_length); //释放内存 void (*free) (modbus_t *ctx);} modbus_backend_t;struct _modbus { /* Slave address */ int slave; //从站设备地址 /* Socket or file descriptor */ int s; //TCP模式下为套接字 RTU模式下为串口句柄 int debug; //是否启用debug模式 int error_recovery; //错误恢复模式 struct timeval response_timeout; //响应超时设置 struct timeval byte_timeout; //字节超时设置 struct timeval indication_timeout; //请求超时设置 //包含一系列通用函数指针 const modbus_backend_t *backend; void *backend_data; //TCP模式下特殊配置数据 RTU模式下特殊配置数据};void _modbus_init_common(modbus_t *ctx);void _error_print(modbus_t *ctx, const char *context);int _modbus_receive_msg(modbus_t *ctx, uint8_t *msg, msg_type_t msg_type);#ifndef HAVE_STRLCPYsize_t strlcpy(char *dest, const char *src, size_t dest_size);#endifMODBUS_END_DECLS#endif /* MODBUS_PRIVATE_H */
        
       
      
     
    
   

02. modbus.h文件

libmodbus对外开放的API接口

/* * Copyright © 2001-2013 Stéphane Raimbault 
   
     * * SPDX-License-Identifier: LGPL-2.1-or-later */#ifndef MODBUS_H#define MODBUS_H/* Add this for macros that defined unix flavor */#if (defined(__unix__) || defined(unix)) && !defined(USG)#include 
    
     #endif#ifndef _MSC_VER#include 
     
      #else#include "stdint.h"#endif#include "modbus-version.h"#if defined(_MSC_VER)# if defined(DLLBUILD)/* define DLLBUILD when building the DLL */#  define MODBUS_API __declspec(dllexport)# else#  define MODBUS_API __declspec(dllimport)# endif#else# define MODBUS_API#endif#ifdef  __cplusplus# define MODBUS_BEGIN_DECLS  extern "C" {
   # define MODBUS_END_DECLS    }#else# define MODBUS_BEGIN_DECLS# define MODBUS_END_DECLS#endifMODBUS_BEGIN_DECLS#ifndef FALSE#define FALSE 0#endif#ifndef TRUE#define TRUE 1#endif#ifndef OFF#define OFF 0#endif#ifndef ON#define ON 1#endif/* Modbus function codes */ //功能码#define MODBUS_FC_READ_COILS                0x01#define MODBUS_FC_READ_DISCRETE_INPUTS      0x02#define MODBUS_FC_READ_HOLDING_REGISTERS    0x03#define MODBUS_FC_READ_INPUT_REGISTERS      0x04#define MODBUS_FC_WRITE_SINGLE_COIL         0x05#define MODBUS_FC_WRITE_SINGLE_REGISTER     0x06#define MODBUS_FC_READ_EXCEPTION_STATUS     0x07#define MODBUS_FC_WRITE_MULTIPLE_COILS      0x0F#define MODBUS_FC_WRITE_MULTIPLE_REGISTERS  0x10#define MODBUS_FC_REPORT_SLAVE_ID           0x11#define MODBUS_FC_MASK_WRITE_REGISTER       0x16#define MODBUS_FC_WRITE_AND_READ_REGISTERS  0x17//广播地址#define MODBUS_BROADCAST_ADDRESS    0/* Modbus_Application_Protocol_V1_1b.pdf (chapter 6 section 1 page 12) * Quantity of Coils to read (2 bytes): 1 to 2000 (0x7D0) * (chapter 6 section 11 page 29) * Quantity of Coils to write (2 bytes): 1 to 1968 (0x7B0) */#define MODBUS_MAX_READ_BITS              2000#define MODBUS_MAX_WRITE_BITS             1968/* Modbus_Application_Protocol_V1_1b.pdf (chapter 6 section 3 page 15) * Quantity of Registers to read (2 bytes): 1 to 125 (0x7D) * (chapter 6 section 12 page 31) * Quantity of Registers to write (2 bytes) 1 to 123 (0x7B) * (chapter 6 section 17 page 38) * Quantity of Registers to write in R/W registers (2 bytes) 1 to 121 (0x79) */#define MODBUS_MAX_READ_REGISTERS          125#define MODBUS_MAX_WRITE_REGISTERS         123#define MODBUS_MAX_WR_WRITE_REGISTERS      121#define MODBUS_MAX_WR_READ_REGISTERS       125/* The size of the MODBUS PDU is limited by the size constraint inherited from * the first MODBUS implementation on Serial Line network (max. RS485 ADU = 256 * bytes). Therefore, MODBUS PDU for serial line communication = 256 - Server * address (1 byte) - CRC (2 bytes) = 253 bytes. */#define MODBUS_MAX_PDU_LENGTH              253/* Consequently: * - RTU MODBUS ADU = 253 bytes + Server address (1 byte) + CRC (2 bytes) = 256 *   bytes. * - TCP MODBUS ADU = 253 bytes + MBAP (7 bytes) = 260 bytes. * so the maximum of both backend in 260 bytes. This size can used to allocate * an array of bytes to store responses and it will be compatible with the two * backends. */#define MODBUS_MAX_ADU_LENGTH              260/* Random number to avoid errno conflicts */#define MODBUS_ENOBASE 112345678/* Protocol exceptions */enum {
       MODBUS_EXCEPTION_ILLEGAL_FUNCTION = 0x01,   //非法的功能码    MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS,      //非法的数据地址    MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE,        //非法的数据值    MODBUS_EXCEPTION_SLAVE_OR_SERVER_FAILURE,   //从站设备故障    MODBUS_EXCEPTION_ACKNOWLEDGE,               //ACK异常    MODBUS_EXCEPTION_SLAVE_OR_SERVER_BUSY,      //从站设备忙    MODBUS_EXCEPTION_NEGATIVE_ACKNOWLEDGE,      //否定应答    MODBUS_EXCEPTION_MEMORY_PARITY,             //内存奇偶校验错误    MODBUS_EXCEPTION_NOT_DEFINED,               //未定义    MODBUS_EXCEPTION_GATEWAY_PATH,              //网关路径不可用    MODBUS_EXCEPTION_GATEWAY_TARGET,            //目标设备未能回应    MODBUS_EXCEPTION_MAX};#define EMBXILFUN  (MODBUS_ENOBASE + MODBUS_EXCEPTION_ILLEGAL_FUNCTION)#define EMBXILADD  (MODBUS_ENOBASE + MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS)#define EMBXILVAL  (MODBUS_ENOBASE + MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE)#define EMBXSFAIL  (MODBUS_ENOBASE + MODBUS_EXCEPTION_SLAVE_OR_SERVER_FAILURE)#define EMBXACK    (MODBUS_ENOBASE + MODBUS_EXCEPTION_ACKNOWLEDGE)#define EMBXSBUSY  (MODBUS_ENOBASE + MODBUS_EXCEPTION_SLAVE_OR_SERVER_BUSY)#define EMBXNACK   (MODBUS_ENOBASE + MODBUS_EXCEPTION_NEGATIVE_ACKNOWLEDGE)#define EMBXMEMPAR (MODBUS_ENOBASE + MODBUS_EXCEPTION_MEMORY_PARITY)#define EMBXGPATH  (MODBUS_ENOBASE + MODBUS_EXCEPTION_GATEWAY_PATH)#define EMBXGTAR   (MODBUS_ENOBASE + MODBUS_EXCEPTION_GATEWAY_TARGET)/* Native libmodbus error codes */#define EMBBADCRC  (EMBXGTAR + 1)   //无效的CRC    #define EMBBADDATA (EMBXGTAR + 2)   //无效的数据#define EMBBADEXC  (EMBXGTAR + 3)   //无效的异常码#define EMBUNKEXC  (EMBXGTAR + 4)   //保留 未使用#define EMBMDATA   (EMBXGTAR + 5)   //数据过多#define EMBBADSLAVE (EMBXGTAR + 6)  //响应与查询地址不匹配extern const unsigned int libmodbus_version_major;extern const unsigned int libmodbus_version_minor;extern const unsigned int libmodbus_version_micro;typedef struct _modbus modbus_t;typedef struct _modbus_mapping_t {
       int nb_bits;                    //线圈寄存器的数量    int start_bits;                 //线圈寄存器的起始地址    int nb_input_bits;              //离散输入寄存器的数量           int start_input_bits;           //离散输入寄存器的起始地址    int nb_input_registers;         //输入寄存器的数量    int start_input_registers;      //输入寄存器的起始地址    int nb_registers;               //保持寄存器的数量    int start_registers;            //保持寄存器的起始地址    uint8_t *tab_bits;              //指向线圈寄存器的值    uint8_t *tab_input_bits;        //指向离散输入寄存器的值    uint16_t *tab_input_registers;  //指向输入寄存器的值    uint16_t *tab_registers;        //指向保持寄存器的值} modbus_mapping_t;typedef enum{
       MODBUS_ERROR_RECOVERY_NONE          = 0,        //不恢复    MODBUS_ERROR_RECOVERY_LINK          = (1<<1),   //链接层恢复    MODBUS_ERROR_RECOVERY_PROTOCOL      = (1<<2)    //协议层恢复} modbus_error_recovery_mode;//设置从站地址MODBUS_API int modbus_set_slave(modbus_t* ctx, int slave);//获取从站地址MODBUS_API int modbus_get_slave(modbus_t* ctx);//设置错误恢复模式MODBUS_API int modbus_set_error_recovery(modbus_t *ctx, modbus_error_recovery_mode error_recovery);//设置当前socket或者串口句柄MODBUS_API int modbus_set_socket(modbus_t *ctx, int s);//获取当前socket或者窗口句柄MODBUS_API int modbus_get_socket(modbus_t *ctx);//获取响应超时MODBUS_API int modbus_get_response_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec);//设置响应超时MODBUS_API int modbus_set_response_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec);//获取连续字节之间的超时时间MODBUS_API int modbus_get_byte_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec);//设置连续字节之间的超时时间MODBUS_API int modbus_set_byte_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec);//获取服务端等待客户端请求超时时间MODBUS_API int modbus_get_indication_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec);//设置服务端等待客户端请求超时时间MODBUS_API int modbus_set_indication_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec);//获取报文头长度MODBUS_API int modbus_get_header_length(modbus_t *ctx);//用于主站设备与从站设备建立连接MODBUS_API int modbus_connect(modbus_t *ctx);//关闭连接MODBUS_API void modbus_close(modbus_t *ctx);//释放内存MODBUS_API void modbus_free(modbus_t *ctx);//刷新缓冲区MODBUS_API int modbus_flush(modbus_t *ctx);//是否设置为debug模式MODBUS_API int modbus_set_debug(modbus_t *ctx, int flag);//获取当前错误信息MODBUS_API const char *modbus_strerror(int errnum);//-------------------------------------------------------------------------------//读取线圈或者离散量输出状态(功能码 0x1)MODBUS_API int modbus_read_bits(modbus_t *ctx, int addr, int nb, uint8_t *dest);//读取离散量输入值(功能码 0x2)MODBUS_API int modbus_read_input_bits(modbus_t *ctx, int addr, int nb, uint8_t *dest);//读取保持寄存器(功能码 0x3)MODBUS_API int modbus_read_registers(modbus_t *ctx, int addr, int nb, uint16_t *dest);//读取输入寄存器(功能码 0x4)MODBUS_API int modbus_read_input_registers(modbus_t *ctx, int addr, int nb, uint16_t *dest);//写单个线圈或者单个离散量(功能码 0x5)MODBUS_API int modbus_write_bit(modbus_t *ctx, int coil_addr, int status);//写单个保持寄存器(功能码 0x6)MODBUS_API int modbus_write_register(modbus_t *ctx, int reg_addr, const uint16_t value);//写多个线圈(功能码 0xF)MODBUS_API int modbus_write_bits(modbus_t *ctx, int addr, int nb, const uint8_t *data);//写多个保持寄存器(功能码 0x10)MODBUS_API int modbus_write_registers(modbus_t *ctx, int addr, int nb, const uint16_t *data);MODBUS_API int modbus_mask_write_register(modbus_t *ctx, int addr, uint16_t and_mask, uint16_t or_mask);MODBUS_API int modbus_write_and_read_registers(modbus_t *ctx, int write_addr, int write_nb,                                               const uint16_t *src, int read_addr, int read_nb,                                               uint16_t *dest);//报告从站ID(功能码 0x11)MODBUS_API int modbus_report_slave_id(modbus_t *ctx, int max_dest, uint8_t *dest);MODBUS_API modbus_mapping_t* modbus_mapping_new_start_address(    unsigned int start_bits, unsigned int nb_bits,    unsigned int start_input_bits, unsigned int nb_input_bits,    unsigned int start_registers, unsigned int nb_registers,    unsigned int start_input_registers, unsigned int nb_input_registers);MODBUS_API modbus_mapping_t* modbus_mapping_new(int nb_bits, int nb_input_bits,                                                int nb_registers, int nb_input_registers);MODBUS_API void modbus_mapping_free(modbus_mapping_t *mb_mapping);MODBUS_API int modbus_send_raw_request(modbus_t *ctx, const uint8_t *raw_req, int raw_req_length);MODBUS_API int modbus_receive(modbus_t *ctx, uint8_t *req);MODBUS_API int modbus_receive_confirmation(modbus_t *ctx, uint8_t *rsp);MODBUS_API int modbus_reply(modbus_t *ctx, const uint8_t *req,                            int req_length, modbus_mapping_t *mb_mapping);MODBUS_API int modbus_reply_exception(modbus_t *ctx, const uint8_t *req,                                      unsigned int exception_code);/** * UTILS FUNCTIONS **///获取高字节#define MODBUS_GET_HIGH_BYTE(data) (((data) >> 8) & 0xFF)//获取低字节#define MODBUS_GET_LOW_BYTE(data) ((data) & 0xFF)#define MODBUS_GET_INT64_FROM_INT16(tab_int16, index) \    (((int64_t)tab_int16[(index)    ] << 48) | \     ((int64_t)tab_int16[(index) + 1] << 32) | \     ((int64_t)tab_int16[(index) + 2] << 16) | \      (int64_t)tab_int16[(index) + 3])#define MODBUS_GET_INT32_FROM_INT16(tab_int16, index) \    (((int32_t)tab_int16[(index)    ] << 16) | \      (int32_t)tab_int16[(index) + 1])#define MODBUS_GET_INT16_FROM_INT8(tab_int8, index) \    (((int16_t)tab_int8[(index)    ] << 8) | \      (int16_t)tab_int8[(index) + 1])#define MODBUS_SET_INT16_TO_INT8(tab_int8, index, value) \    do { \        ((int8_t*)(tab_int8))[(index)    ] = (int8_t)((value) >> 8);  \        ((int8_t*)(tab_int8))[(index) + 1] = (int8_t)(value); \    } while (0)#define MODBUS_SET_INT32_TO_INT16(tab_int16, index, value) \    do { \        ((int16_t*)(tab_int16))[(index)    ] = (int16_t)((value) >> 16); \        ((int16_t*)(tab_int16))[(index) + 1] = (int16_t)(value); \    } while (0)#define MODBUS_SET_INT64_TO_INT16(tab_int16, index, value) \    do { \        ((int16_t*)(tab_int16))[(index)    ] = (int16_t)((value) >> 48); \        ((int16_t*)(tab_int16))[(index) + 1] = (int16_t)((value) >> 32); \        ((int16_t*)(tab_int16))[(index) + 2] = (int16_t)((value) >> 16); \        ((int16_t*)(tab_int16))[(index) + 3] = (int16_t)(value); \    } while (0)MODBUS_API void modbus_set_bits_from_byte(uint8_t *dest, int idx, const uint8_t value);MODBUS_API void modbus_set_bits_from_bytes(uint8_t *dest, int idx, unsigned int nb_bits,                                       const uint8_t *tab_byte);MODBUS_API uint8_t modbus_get_byte_from_bits(const uint8_t *src, int idx, unsigned int nb_bits);MODBUS_API float modbus_get_float(const uint16_t *src);MODBUS_API float modbus_get_float_abcd(const uint16_t *src);MODBUS_API float modbus_get_float_dcba(const uint16_t *src);MODBUS_API float modbus_get_float_badc(const uint16_t *src);MODBUS_API float modbus_get_float_cdab(const uint16_t *src);MODBUS_API void modbus_set_float(float f, uint16_t *dest);MODBUS_API void modbus_set_float_abcd(float f, uint16_t *dest);MODBUS_API void modbus_set_float_dcba(float f, uint16_t *dest);MODBUS_API void modbus_set_float_badc(float f, uint16_t *dest);MODBUS_API void modbus_set_float_cdab(float f, uint16_t *dest);#include "modbus-tcp.h"#include "modbus-rtu.h"MODBUS_END_DECLS#endif  /* MODBUS_H */
     
    
   

03. modbus.c文件

modbus.c 核心文件，实现Modbus协议层，定义通用的Modbus消息发送和接收函数、各功能码对应的函数

/* * Copyright © 2001-2011 Stéphane Raimbault 
   
     * * SPDX-License-Identifier: LGPL-2.1-or-later * * This library implements the Modbus protocol. * http://libmodbus.org/ */#include 
    
     #include 
     
      #include 
      
       #include 
       
        #include 
        
         #include 
         
          #include 
          
           #ifndef _MSC_VER#include 
           
            #endif#include 
            
             #include "modbus.h"#include "modbus-private.h"/* Internal use */#define MSG_LENGTH_UNDEFINED -1/* Exported version */const unsigned int libmodbus_version_major = LIBMODBUS_VERSION_MAJOR;const unsigned int libmodbus_version_minor = LIBMODBUS_VERSION_MINOR;const unsigned int libmodbus_version_micro = LIBMODBUS_VERSION_MICRO;/* Max between RTU and TCP max adu length (so TCP) */#define MAX_MESSAGE_LENGTH 260/* 3 steps are used to parse the query */typedef enum { _STEP_FUNCTION, _STEP_META, _STEP_DATA} _step_t;//错误解析const char *modbus_strerror(int errnum) { switch (errnum) { case EMBXILFUN: return "Illegal function"; case EMBXILADD: return "Illegal data address"; case EMBXILVAL: return "Illegal data value"; case EMBXSFAIL: return "Slave device or server failure"; case EMBXACK: return "Acknowledge"; case EMBXSBUSY: return "Slave device or server is busy"; case EMBXNACK: return "Negative acknowledge"; case EMBXMEMPAR: return "Memory parity error"; case EMBXGPATH: return "Gateway path unavailable"; case EMBXGTAR: return "Target device failed to respond"; case EMBBADCRC: return "Invalid CRC"; case EMBBADDATA: return "Invalid data"; case EMBBADEXC: return "Invalid exception code"; case EMBMDATA: return "Too many data"; case EMBBADSLAVE: return "Response not from requested slave"; default: return strerror(errnum); }}//错误输出void _error_print(modbus_t *ctx, const char *context){ if (ctx->debug) { fprintf(stderr, "ERROR %s", modbus_strerror(errno)); if (context != NULL) { fprintf(stderr, ": %s\n", context); } else { fprintf(stderr, "\n"); } }}//响应超时static void _sleep_response_timeout(modbus_t *ctx){ /* Response timeout is always positive */#ifdef _WIN32 /* usleep doesn't exist on Windows */ Sleep((ctx->response_timeout.tv_sec * 1000) + (ctx->response_timeout.tv_usec / 1000));#else /* usleep source code */ struct timespec request, remaining; request.tv_sec = ctx->response_timeout.tv_sec; request.tv_nsec = ((long int)ctx->response_timeout.tv_usec) * 1000; while (nanosleep(&request, &remaining) == -1 && errno == EINTR) { request = remaining; }#endif}//刷新缓冲区int modbus_flush(modbus_t *ctx){ int rc; if (ctx == NULL) { errno = EINVAL; return -1; } rc = ctx->backend->flush(ctx); if (rc != -1 && ctx->debug) { /* Not all backends are able to return the number of bytes flushed */ printf("Bytes flushed (%d)\n", rc); } return rc;}/* Computes the length of the expected response */static unsigned int compute_response_length_from_request(modbus_t *ctx, uint8_t *req){ int length; const int offset = ctx->backend->header_length; switch (req[offset]) { case MODBUS_FC_READ_COILS: case MODBUS_FC_READ_DISCRETE_INPUTS: { /* Header + nb values (code from write_bits) */ int nb = (req[offset + 3] << 8) | req[offset + 4]; length = 2 + (nb / 8) + ((nb % 8) ? 1 : 0); } break; case MODBUS_FC_WRITE_AND_READ_REGISTERS: case MODBUS_FC_READ_HOLDING_REGISTERS: case MODBUS_FC_READ_INPUT_REGISTERS: /* Header + 2 * nb values */ length = 2 + 2 * (req[offset + 3] << 8 | req[offset + 4]); break; case MODBUS_FC_READ_EXCEPTION_STATUS: length = 3; break; case MODBUS_FC_REPORT_SLAVE_ID: /* The response is device specific (the header provides the length) */ return MSG_LENGTH_UNDEFINED; case MODBUS_FC_MASK_WRITE_REGISTER: length = 7; break; default: length = 5; } return offset + length + ctx->backend->checksum_length;}/* Sends a request/response */static int send_msg(modbus_t *ctx, uint8_t *msg, int msg_length){ int rc; int i; //进行消息预处理 msg_length = ctx->backend->send_msg_pre(msg, msg_length); if (ctx->debug) { for (i = 0; i < msg_length; i++) printf("[%.2X]", msg[i]); printf("\n"); } /* In recovery mode, the write command will be issued until to be successful! Disabled by default. */ do { rc = ctx->backend->send(ctx, msg, msg_length); if (rc == -1) { _error_print(ctx, NULL); if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) { int saved_errno = errno; if ((errno == EBADF || errno == ECONNRESET || errno == EPIPE)) { modbus_close(ctx); _sleep_response_timeout(ctx); modbus_connect(ctx); } else { _sleep_response_timeout(ctx); modbus_flush(ctx); } errno = saved_errno; } } } while ((ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) && rc == -1); if (rc > 0 && rc != msg_length) { errno = EMBBADDATA; return -1; } return rc;}int modbus_send_raw_request(modbus_t *ctx, const uint8_t *raw_req, int raw_req_length){ sft_t sft; uint8_t req[MAX_MESSAGE_LENGTH]; int req_length; if (ctx == NULL) { errno = EINVAL; return -1; } if (raw_req_length < 2 || raw_req_length > (MODBUS_MAX_PDU_LENGTH + 1)) { /* The raw request must contain function and slave at least and must not be longer than the maximum pdu length plus the slave address. */ errno = EINVAL; return -1; } sft.slave = raw_req[0]; sft.function = raw_req[1]; /* The t_id is left to zero */ sft.t_id = 0; /* This response function only set the header so it's convenient here */ req_length = ctx->backend->build_response_basis(&sft, req); if (raw_req_length > 2) { /* Copy data after function code */ memcpy(req + req_length, raw_req + 2, raw_req_length - 2); req_length += raw_req_length - 2; } return send_msg(ctx, req, req_length);}/* * ---------- Request Indication ---------- * | Client | ---------------------->| Server | * ---------- Confirmation Response ---------- *//* Computes the length to read after the function received */static uint8_t compute_meta_length_after_function(int function, msg_type_t msg_type){ int length; if (msg_type == MSG_INDICATION) { if (function <= MODBUS_FC_WRITE_SINGLE_REGISTER) { length = 4; } else if (function == MODBUS_FC_WRITE_MULTIPLE_COILS || function == MODBUS_FC_WRITE_MULTIPLE_REGISTERS) { length = 5; } else if (function == MODBUS_FC_MASK_WRITE_REGISTER) { length = 6; } else if (function == MODBUS_FC_WRITE_AND_READ_REGISTERS) { length = 9; } else { /* MODBUS_FC_READ_EXCEPTION_STATUS, MODBUS_FC_REPORT_SLAVE_ID */ length = 0; } } else { /* MSG_CONFIRMATION */ switch (function) { case MODBUS_FC_WRITE_SINGLE_COIL: case MODBUS_FC_WRITE_SINGLE_REGISTER: case MODBUS_FC_WRITE_MULTIPLE_COILS: case MODBUS_FC_WRITE_MULTIPLE_REGISTERS: length = 4; break; case MODBUS_FC_MASK_WRITE_REGISTER: length = 6; break; default: length = 1; } } return length;}/* Computes the length to read after the meta information (address, count, etc) */static int compute_data_length_after_meta(modbus_t *ctx, uint8_t *msg, msg_type_t msg_type){ int function = msg[ctx->backend->header_length]; int length; if (msg_type == MSG_INDICATION) { switch (function) { case MODBUS_FC_WRITE_MULTIPLE_COILS: case MODBUS_FC_WRITE_MULTIPLE_REGISTERS: length = msg[ctx->backend->header_length + 5]; break; case MODBUS_FC_WRITE_AND_READ_REGISTERS: length = msg[ctx->backend->header_length + 9]; break; default: length = 0; } } else { /* MSG_CONFIRMATION */ if (function <= MODBUS_FC_READ_INPUT_REGISTERS || function == MODBUS_FC_REPORT_SLAVE_ID || function == MODBUS_FC_WRITE_AND_READ_REGISTERS) { length = msg[ctx->backend->header_length + 1]; } else { length = 0; } } length += ctx->backend->checksum_length; return length;}/* Waits a response from a modbus server or a request from a modbus client. This function blocks if there is no replies (3 timeouts). The function shall return the number of received characters and the received message in an array of uint8_t if successful. Otherwise it shall return -1 and errno is set to one of the values defined below: - ECONNRESET - EMBBADDATA - EMBUNKEXC - ETIMEDOUT - read() or recv() error codes*/int _modbus_receive_msg(modbus_t *ctx, uint8_t *msg, msg_type_t msg_type){ int rc; fd_set rset; struct timeval tv; struct timeval *p_tv; int length_to_read; int msg_length = 0; _step_t step; if (ctx->debug) { if (msg_type == MSG_INDICATION) { //表示正在等待查询报文 printf("Waiting for an indication...\n"); } else { //表示发送查询报文后等待接收响应 printf("Waiting for a confirmation...\n"); } } /* Add a file descriptor to the set */ FD_ZERO(&rset); FD_SET(ctx->s, &rset); /* We need to analyse the message step by step. At the first step, we want * to reach the function code because all packets contain this * information. */ step = _STEP_FUNCTION; length_to_read = ctx->backend->header_length + 1; if (msg_type == MSG_INDICATION) { /* Wait for a message, we don't know when the message will be * received */ if (ctx->indication_timeout.tv_sec == 0 && ctx->indication_timeout.tv_usec == 0) { /* By default, the indication timeout isn't set */ p_tv = NULL; } else { /* Wait for an indication (name of a received request by a server, see schema) */ tv.tv_sec = ctx->indication_timeout.tv_sec; tv.tv_usec = ctx->indication_timeout.tv_usec; p_tv = &tv; } } else { tv.tv_sec = ctx->response_timeout.tv_sec; tv.tv_usec = ctx->response_timeout.tv_usec; p_tv = &tv; } while (length_to_read != 0) { rc = ctx->backend->select(ctx, &rset, p_tv, length_to_read); if (rc == -1) { _error_print(ctx, "select"); if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) { int saved_errno = errno; if (errno == ETIMEDOUT) { _sleep_response_timeout(ctx); modbus_flush(ctx); } else if (errno == EBADF) { modbus_close(ctx); modbus_connect(ctx); } errno = saved_errno; } return -1; } rc = ctx->backend->recv(ctx, msg + msg_length, length_to_read); if (rc == 0) { errno = ECONNRESET; rc = -1; } if (rc == -1) { _error_print(ctx, "read"); if ((ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) && (errno == ECONNRESET || errno == ECONNREFUSED || errno == EBADF)) { int saved_errno = errno; modbus_close(ctx); modbus_connect(ctx); /* Could be removed by previous calls */ errno = saved_errno; } return -1; } /* Display the hex code of each character received */ if (ctx->debug) { int i; for (i=0; i < rc; i++) printf("<%.2X>", msg[msg_length + i]); } /* Sums bytes received */ msg_length += rc; /* Computes remaining bytes */ length_to_read -= rc; if (length_to_read == 0) { switch (step) { case _STEP_FUNCTION: /* Function code position */ length_to_read = compute_meta_length_after_function( msg[ctx->backend->header_length], msg_type); if (length_to_read != 0) { step = _STEP_META; break; } /* else switches straight to the next step */ case _STEP_META: length_to_read = compute_data_length_after_meta( ctx, msg, msg_type); if ((msg_length + length_to_read) > (int)ctx->backend->max_adu_length) { errno = EMBBADDATA; _error_print(ctx, "too many data"); return -1; } step = _STEP_DATA; break; default: break; } } if (length_to_read > 0 && (ctx->byte_timeout.tv_sec > 0 || ctx->byte_timeout.tv_usec > 0)) { /* If there is no character in the buffer, the allowed timeout interval between two consecutive bytes is defined by byte_timeout */ tv.tv_sec = ctx->byte_timeout.tv_sec; tv.tv_usec = ctx->byte_timeout.tv_usec; p_tv = &tv; } /* else timeout isn't set again, the full response must be read before expiration of response timeout (for CONFIRMATION only) */ } if (ctx->debug) printf("\n"); return ctx->backend->check_integrity(ctx, msg, msg_length);}/* Receive the request from a modbus master */int modbus_receive(modbus_t *ctx, uint8_t *req){ if (ctx == NULL) { errno = EINVAL; return -1; } return ctx->backend->receive(ctx, req);}/* Receives the confirmation. The function shall store the read response in rsp and return the number of values (bits or words). Otherwise, its shall return -1 and errno is set. The function doesn't check the confirmation is the expected response to the initial request.*/int modbus_receive_confirmation(modbus_t *ctx, uint8_t *rsp){ if (ctx == NULL) { errno = EINVAL; return -1; } return _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);}static int check_confirmation(modbus_t *ctx, uint8_t *req, uint8_t *rsp, int rsp_length){ int rc; int rsp_length_computed; const int offset = ctx->backend->header_length; const int function = rsp[offset]; if (ctx->backend->pre_check_confirmation) { rc = ctx->backend->pre_check_confirmation(ctx, req, rsp, rsp_length); if (rc == -1) { if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) { _sleep_response_timeout(ctx); modbus_flush(ctx); } return -1; } } rsp_length_computed = compute_response_length_from_request(ctx, req); /* Exception code */ if (function >= 0x80) { if (rsp_length == (offset + 2 + (int)ctx->backend->checksum_length) && req[offset] == (rsp[offset] - 0x80)) { /* Valid exception code received */ int exception_code = rsp[offset + 1]; if (exception_code < MODBUS_EXCEPTION_MAX) { errno = MODBUS_ENOBASE + exception_code; } else { errno = EMBBADEXC; } _error_print(ctx, NULL); return -1; } else { errno = EMBBADEXC; _error_print(ctx, NULL); return -1; } } /* Check length */ if ((rsp_length == rsp_length_computed || rsp_length_computed == MSG_LENGTH_UNDEFINED) && function < 0x80) { int req_nb_value; int rsp_nb_value; /* Check function code */ if (function != req[offset]) { if (ctx->debug) { fprintf(stderr, "Received function not corresponding to the request (0x%X != 0x%X)\n", function, req[offset]); } if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) { _sleep_response_timeout(ctx); modbus_flush(ctx); } errno = EMBBADDATA; return -1; } /* Check the number of values is corresponding to the request */ switch (function) { case MODBUS_FC_READ_COILS: case MODBUS_FC_READ_DISCRETE_INPUTS: /* Read functions, 8 values in a byte (nb * of values in the request and byte count in * the response. */ req_nb_value = (req[offset + 3] << 8) + req[offset + 4]; req_nb_value = (req_nb_value / 8) + ((req_nb_value % 8) ? 1 : 0); rsp_nb_value = rsp[offset + 1]; break; case MODBUS_FC_WRITE_AND_READ_REGISTERS: case MODBUS_FC_READ_HOLDING_REGISTERS: case MODBUS_FC_READ_INPUT_REGISTERS: /* Read functions 1 value = 2 bytes */ req_nb_value = (req[offset + 3] << 8) + req[offset + 4]; rsp_nb_value = (rsp[offset + 1] / 2); break; case MODBUS_FC_WRITE_MULTIPLE_COILS: case MODBUS_FC_WRITE_MULTIPLE_REGISTERS: /* N Write functions */ req_nb_value = (req[offset + 3] << 8) + req[offset + 4]; rsp_nb_value = (rsp[offset + 3] << 8) | rsp[offset + 4]; break; case MODBUS_FC_REPORT_SLAVE_ID: /* Report slave ID (bytes received) */ req_nb_value = rsp_nb_value = rsp[offset + 1]; break; default: /* 1 Write functions & others */ req_nb_value = rsp_nb_value = 1; } if (req_nb_value == rsp_nb_value) { rc = rsp_nb_value; } else { if (ctx->debug) { fprintf(stderr, "Quantity not corresponding to the request (%d != %d)\n", rsp_nb_value, req_nb_value); } if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) { _sleep_response_timeout(ctx); modbus_flush(ctx); } errno = EMBBADDATA; rc = -1; } } else { if (ctx->debug) { fprintf(stderr, "Message length not corresponding to the computed length (%d != %d)\n", rsp_length, rsp_length_computed); } if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) { _sleep_response_timeout(ctx); modbus_flush(ctx); } errno = EMBBADDATA; rc = -1; } return rc;}static int response_io_status(uint8_t *tab_io_status, int address, int nb, uint8_t *rsp, int offset){ int shift = 0; /* Instead of byte (not allowed in Win32) */ int one_byte = 0; int i; for (i = address; i < address + nb; i++) { one_byte |= tab_io_status[i] << shift; if (shift == 7) { /* Byte is full */ rsp[offset++] = one_byte; one_byte = shift = 0; } else { shift++; } } if (shift != 0) rsp[offset++] = one_byte; return offset;}/* Build the exception response */static int response_exception(modbus_t *ctx, sft_t *sft, int exception_code, uint8_t *rsp, unsigned int to_flush, const char* template, ...){ int rsp_length; /* Print debug message */ if (ctx->debug) { va_list ap; va_start(ap, template); vfprintf(stderr, template, ap); va_end(ap); } /* Flush if required */ if (to_flush) { _sleep_response_timeout(ctx); modbus_flush(ctx); } /* Build exception response */ sft->function = sft->function + 0x80; rsp_length = ctx->backend->build_response_basis(sft, rsp); rsp[rsp_length++] = exception_code; return rsp_length;}/* Send a response to the received request. Analyses the request and constructs a response. If an error occurs, this function construct the response accordingly.*/int modbus_reply(modbus_t *ctx, const uint8_t *req, int req_length, modbus_mapping_t *mb_mapping){ int offset; int slave; int function; uint16_t address; uint8_t rsp[MAX_MESSAGE_LENGTH]; int rsp_length = 0; sft_t sft; if (ctx == NULL) { errno = EINVAL; return -1; } offset = ctx->backend->header_length; slave = req[offset - 1]; function = req[offset]; address = (req[offset + 1] << 8) + req[offset + 2]; sft.slave = slave; sft.function = function; sft.t_id = ctx->backend->prepare_response_tid(req, &req_length); /* Data are flushed on illegal number of values errors. */ switch (function) { case MODBUS_FC_READ_COILS: case MODBUS_FC_READ_DISCRETE_INPUTS: { unsigned int is_input = (function == MODBUS_FC_READ_DISCRETE_INPUTS); int start_bits = is_input ? mb_mapping->start_input_bits : mb_mapping->start_bits; int nb_bits = is_input ? mb_mapping->nb_input_bits : mb_mapping->nb_bits; uint8_t *tab_bits = is_input ? mb_mapping->tab_input_bits : mb_mapping->tab_bits; const char * const name = is_input ? "read_input_bits" : "read_bits"; int nb = (req[offset + 3] << 8) + req[offset + 4]; /* The mapping can be shifted to reduce memory consumption and it doesn't always start at address zero. */ int mapping_address = address - start_bits; if (nb < 1 || MODBUS_MAX_READ_BITS < nb) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE, "Illegal nb of values %d in %s (max %d)\n", nb, name, MODBUS_MAX_READ_BITS); } else if (mapping_address < 0 || (mapping_address + nb) > nb_bits) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE, "Illegal data address 0x%0X in %s\n", mapping_address < 0 ? address : address + nb, name); } else { rsp_length = ctx->backend->build_response_basis(&sft, rsp); rsp[rsp_length++] = (nb / 8) + ((nb % 8) ? 1 : 0); rsp_length = response_io_status(tab_bits, mapping_address, nb, rsp, rsp_length); } } break; case MODBUS_FC_READ_HOLDING_REGISTERS: case MODBUS_FC_READ_INPUT_REGISTERS: { unsigned int is_input = (function == MODBUS_FC_READ_INPUT_REGISTERS); int start_registers = is_input ? mb_mapping->start_input_registers : mb_mapping->start_registers; int nb_registers = is_input ? mb_mapping->nb_input_registers : mb_mapping->nb_registers; uint16_t *tab_registers = is_input ? mb_mapping->tab_input_registers : mb_mapping->tab_registers; const char * const name = is_input ? "read_input_registers" : "read_registers"; int nb = (req[offset + 3] << 8) + req[offset + 4]; /* The mapping can be shifted to reduce memory consumption and it doesn't always start at address zero. */ int mapping_address = address - start_registers; if (nb < 1 || MODBUS_MAX_READ_REGISTERS < nb) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE, "Illegal nb of values %d in %s (max %d)\n", nb, name, MODBUS_MAX_READ_REGISTERS); } else if (mapping_address < 0 || (mapping_address + nb) > nb_registers) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE, "Illegal data address 0x%0X in %s\n", mapping_address < 0 ? address : address + nb, name); } else { int i; rsp_length = ctx->backend->build_response_basis(&sft, rsp); rsp[rsp_length++] = nb << 1; for (i = mapping_address; i < mapping_address + nb; i++) { rsp[rsp_length++] = tab_registers[i] >> 8; rsp[rsp_length++] = tab_registers[i] & 0xFF; } } } break; case MODBUS_FC_WRITE_SINGLE_COIL: { int mapping_address = address - mb_mapping->start_bits; if (mapping_address < 0 || mapping_address >= mb_mapping->nb_bits) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE, "Illegal data address 0x%0X in write_bit\n", address); } else { int data = (req[offset + 3] << 8) + req[offset + 4]; if (data == 0xFF00 || data == 0x0) { mb_mapping->tab_bits[mapping_address] = data ? ON : OFF; memcpy(rsp, req, req_length); rsp_length = req_length; } else { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, FALSE, "Illegal data value 0x%0X in write_bit request at address %0X\n", data, address); } } } break; case MODBUS_FC_WRITE_SINGLE_REGISTER: { int mapping_address = address - mb_mapping->start_registers; if (mapping_address < 0 || mapping_address >= mb_mapping->nb_registers) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE, "Illegal data address 0x%0X in write_register\n", address); } else { int data = (req[offset + 3] << 8) + req[offset + 4]; mb_mapping->tab_registers[mapping_address] = data; memcpy(rsp, req, req_length); rsp_length = req_length; } } break; case MODBUS_FC_WRITE_MULTIPLE_COILS: { int nb = (req[offset + 3] << 8) + req[offset + 4]; int nb_bits = req[offset + 5]; int mapping_address = address - mb_mapping->start_bits; if (nb < 1 || MODBUS_MAX_WRITE_BITS < nb || nb_bits * 8 < nb) { /* May be the indication has been truncated on reading because of * invalid address (eg. nb is 0 but the request contains values to * write) so it's necessary to flush. */ rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE, "Illegal number of values %d in write_bits (max %d)\n", nb, MODBUS_MAX_WRITE_BITS); } else if (mapping_address < 0 || (mapping_address + nb) > mb_mapping->nb_bits) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE, "Illegal data address 0x%0X in write_bits\n", mapping_address < 0 ? address : address + nb); } else { /* 6 = byte count */ modbus_set_bits_from_bytes(mb_mapping->tab_bits, mapping_address, nb, &req[offset + 6]); rsp_length = ctx->backend->build_response_basis(&sft, rsp); /* 4 to copy the bit address (2) and the quantity of bits */ memcpy(rsp + rsp_length, req + rsp_length, 4); rsp_length += 4; } } break; case MODBUS_FC_WRITE_MULTIPLE_REGISTERS: { int nb = (req[offset + 3] << 8) + req[offset + 4]; int nb_bytes = req[offset + 5]; int mapping_address = address - mb_mapping->start_registers; if (nb < 1 || MODBUS_MAX_WRITE_REGISTERS < nb || nb_bytes != nb * 2) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE, "Illegal number of values %d in write_registers (max %d)\n", nb, MODBUS_MAX_WRITE_REGISTERS); } else if (mapping_address < 0 || (mapping_address + nb) > mb_mapping->nb_registers) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE, "Illegal data address 0x%0X in write_registers\n", mapping_address < 0 ? address : address + nb); } else { int i, j; for (i = mapping_address, j = 6; i < mapping_address + nb; i++, j += 2) { /* 6 and 7 = first value */ mb_mapping->tab_registers[i] = (req[offset + j] << 8) + req[offset + j + 1]; } rsp_length = ctx->backend->build_response_basis(&sft, rsp); /* 4 to copy the address (2) and the no. of registers */ memcpy(rsp + rsp_length, req + rsp_length, 4); rsp_length += 4; } } break; case MODBUS_FC_REPORT_SLAVE_ID: { int str_len; int byte_count_pos; rsp_length = ctx->backend->build_response_basis(&sft, rsp); /* Skip byte count for now */ byte_count_pos = rsp_length++; rsp[rsp_length++] = _REPORT_SLAVE_ID; /* Run indicator status to ON */ rsp[rsp_length++] = 0xFF; /* LMB + length of LIBMODBUS_VERSION_STRING */ str_len = 3 + strlen(LIBMODBUS_VERSION_STRING); memcpy(rsp + rsp_length, "LMB" LIBMODBUS_VERSION_STRING, str_len); rsp_length += str_len; rsp[byte_count_pos] = rsp_length - byte_count_pos - 1; } break; case MODBUS_FC_READ_EXCEPTION_STATUS: if (ctx->debug) { fprintf(stderr, "FIXME Not implemented\n"); } errno = ENOPROTOOPT; return -1; break; case MODBUS_FC_MASK_WRITE_REGISTER: { int mapping_address = address - mb_mapping->start_registers; if (mapping_address < 0 || mapping_address >= mb_mapping->nb_registers) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE, "Illegal data address 0x%0X in write_register\n", address); } else { uint16_t data = mb_mapping->tab_registers[mapping_address]; uint16_t and = (req[offset + 3] << 8) + req[offset + 4]; uint16_t or = (req[offset + 5] << 8) + req[offset + 6]; data = (data & and) | (or & (~and)); mb_mapping->tab_registers[mapping_address] = data; memcpy(rsp, req, req_length); rsp_length = req_length; } } break; case MODBUS_FC_WRITE_AND_READ_REGISTERS: { int nb = (req[offset + 3] << 8) + req[offset + 4]; uint16_t address_write = (req[offset + 5] << 8) + req[offset + 6]; int nb_write = (req[offset + 7] << 8) + req[offset + 8]; int nb_write_bytes = req[offset + 9]; int mapping_address = address - mb_mapping->start_registers; int mapping_address_write = address_write - mb_mapping->start_registers; if (nb_write < 1 || MODBUS_MAX_WR_WRITE_REGISTERS < nb_write || nb < 1 || MODBUS_MAX_WR_READ_REGISTERS < nb || nb_write_bytes != nb_write * 2) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE, "Illegal nb of values (W%d, R%d) in write_and_read_registers (max W%d, R%d)\n", nb_write, nb, MODBUS_MAX_WR_WRITE_REGISTERS, MODBUS_MAX_WR_READ_REGISTERS); } else if (mapping_address < 0 || (mapping_address + nb) > mb_mapping->nb_registers || mapping_address < 0 || (mapping_address_write + nb_write) > mb_mapping->nb_registers) { rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE, "Illegal data read address 0x%0X or write address 0x%0X write_and_read_registers\n", mapping_address < 0 ? address : address + nb, mapping_address_write < 0 ? address_write : address_write + nb_write); } else { int i, j; rsp_length = ctx->backend->build_response_basis(&sft, rsp); rsp[rsp_length++] = nb << 1; /* Write first. 10 and 11 are the offset of the first values to write */ for (i = mapping_address_write, j = 10; i < mapping_address_write + nb_write; i++, j += 2) { mb_mapping->tab_registers[i] = (req[offset + j] << 8) + req[offset + j + 1]; } /* and read the data for the response */ for (i = mapping_address; i < mapping_address + nb; i++) { rsp[rsp_length++] = mb_mapping->tab_registers[i] >> 8; rsp[rsp_length++] = mb_mapping->tab_registers[i] & 0xFF; } } } break; default: rsp_length = response_exception( ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_FUNCTION, rsp, TRUE, "Unknown Modbus function code: 0x%0X\n", function); break; } /* Suppress any responses when the request was a broadcast */ return (ctx->backend->backend_type == _MODBUS_BACKEND_TYPE_RTU && slave == MODBUS_BROADCAST_ADDRESS) ? 0 : send_msg(ctx, rsp, rsp_length);}int modbus_reply_exception(modbus_t *ctx, const uint8_t *req, unsigned int exception_code){ int offset; int slave; int function; uint8_t rsp[MAX_MESSAGE_LENGTH]; int rsp_length; int dummy_length = 99; sft_t sft; if (ctx == NULL) { errno = EINVAL; return -1; } offset = ctx->backend->header_length; slave = req[offset - 1]; function = req[offset]; sft.slave = slave; sft.function = function + 0x80; sft.t_id = ctx->backend->prepare_response_tid(req, &dummy_length); rsp_length = ctx->backend->build_response_basis(&sft, rsp); /* Positive exception code */ if (exception_code < MODBUS_EXCEPTION_MAX) { rsp[rsp_length++] = exception_code; return send_msg(ctx, rsp, rsp_length); } else { errno = EINVAL; return -1; }}/* Reads IO status */static int read_io_status(modbus_t *ctx, int function, int addr, int nb, uint8_t *dest){ int rc; int req_length; uint8_t req[_MIN_REQ_LENGTH]; uint8_t rsp[MAX_MESSAGE_LENGTH]; //构造查询帧的基础部分根据RTU模式或者TCP模式分别调用不同的构造函数 req_length = ctx->backend->build_request_basis(ctx, function, addr, nb, req); rc = send_msg(ctx, req, req_length); if (rc > 0) { int i, temp, bit; int pos = 0; int offset; int offset_end; rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION); if (rc == -1) return -1; rc = check_confirmation(ctx, req, rsp, rc); if (rc == -1) return -1; //响应码 MBAP+功能码(1字节)+数据长度(1字节) offset = ctx->backend->header_length + 2; offset_end = offset + rc; for (i = offset; i < offset_end; i++) { /* Shift reg hi_byte to temp */ temp = rsp[i]; for (bit = 0x01; (bit & 0xff) && (pos < nb);) { dest[pos++] = (temp & bit) ? TRUE : FALSE; bit = bit << 1; } } } return rc;}/* Reads the boolean status of bits and sets the array elements in the destination to TRUE or FALSE (single bits). */int modbus_read_bits(modbus_t *ctx, int addr, int nb, uint8_t *dest){ int rc; if (ctx == NULL) { errno = EINVAL; return -1; } if (nb > MODBUS_MAX_READ_BITS) { if (ctx->debug) { fprintf(stderr, "ERROR Too many bits requested (%d > %d)\n", nb, MODBUS_MAX_READ_BITS); } errno = EMBMDATA; return -1; } rc = read_io_status(ctx, MODBUS_FC_READ_COILS, addr, nb, dest); if (rc == -1) return -1; else return nb;}/* Same as modbus_read_bits but reads the remote device input table */int modbus_read_input_bits(modbus_t *ctx, int addr, int nb, uint8_t *dest){ int rc; if (ctx == NULL) { errno = EINVAL; return -1; } if (nb > MODBUS_MAX_READ_BITS) { if (ctx->debug) { fprintf(stderr, "ERROR Too many discrete inputs requested (%d > %d)\n", nb, MODBUS_MAX_READ_BITS); } errno = EMBMDATA; return -1; } rc = read_io_status(ctx, MODBUS_FC_READ_DISCRETE_INPUTS, addr, nb, dest); if (rc == -1) return -1; else return nb;}/* Reads the data from a remove device and put that data into an array */static int read_registers(modbus_t *ctx, int function, int addr, int nb, uint16_t *dest){ int rc; int req_length; uint8_t req[_MIN_REQ_LENGTH]; uint8_t rsp[MAX_MESSAGE_LENGTH]; //判断读取寄存器的数量是否在允许的范围之内 if (nb > MODBUS_MAX_READ_REGISTERS) { if (ctx->debug) { fprintf(stderr, "ERROR Too many registers requested (%d > %d)\n", nb, MODBUS_MAX_READ_REGISTERS); } errno = EMBMDATA; return -1; } //构造查询帧的基础部分 req_length = ctx->backend->build_request_basis(ctx, function, addr, nb, req); //发送消息帧 rc = send_msg(ctx, req, req_length); if (rc > 0) { int offset; int i; //接收响应报文 rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION); if (rc == -1) return -1; rc = check_confirmation(ctx, req, rsp, rc); if (rc == -1) return -1; offset = ctx->backend->header_length; for (i = 0; i < rc; i++) { /* shift reg hi_byte to temp OR with lo_byte */ dest[i] = (rsp[offset + 2 + (i << 1)] << 8) | rsp[offset + 3 + (i << 1)]; } } return rc;}/* Reads the holding registers of remote device and put the data into an array */int modbus_read_registers(modbus_t *ctx, int addr, int nb, uint16_t *dest){ int status; if (ctx == NULL) { errno = EINVAL; return -1; } if (nb > MODBUS_MAX_READ_REGISTERS) { if (ctx->debug) { fprintf(stderr, "ERROR Too many registers requested (%d > %d)\n", nb, MODBUS_MAX_READ_REGISTERS); } errno = EMBMDATA; return -1; } status = read_registers(ctx, MODBUS_FC_READ_HOLDING_REGISTERS, addr, nb, dest); return status;}/* Reads the input registers of remote device and put the data into an array */int modbus_read_input_registers(modbus_t *ctx, int addr, int nb, uint16_t *dest){ int status; if (ctx == NULL) { errno = EINVAL; return -1; } if (nb > MODBUS_MAX_READ_REGISTERS) { fprintf(stderr, "ERROR Too many input registers requested (%d > %d)\n", nb, MODBUS_MAX_READ_REGISTERS); errno = EMBMDATA; return -1; } status = read_registers(ctx, MODBUS_FC_READ_INPUT_REGISTERS, addr, nb, dest); return status;}/* Write a value to the specified register of the remote device. Used by write_bit and write_register */static int write_single(modbus_t *ctx, int function, int addr, const uint16_t value){ int rc; int req_length; uint8_t req[_MIN_REQ_LENGTH]; if (ctx == NULL) { errno = EINVAL; return -1; } req_length = ctx->backend->build_request_basis(ctx, function, addr, (int) value, req); rc = send_msg(ctx, req, req_length); if (rc > 0) { /* Used by write_bit and write_register */ uint8_t rsp[MAX_MESSAGE_LENGTH]; rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION); if (rc == -1) return -1; rc = check_confirmation(ctx, req, rsp, rc); } return rc;}/* Turns ON or OFF a single bit of the remote device */int modbus_write_bit(modbus_t *ctx, int addr, int status){ if (ctx == NULL) { errno = EINVAL; return -1; } return write_single(ctx, MODBUS_FC_WRITE_SINGLE_COIL, addr, status ? 0xFF00 : 0);}/* Writes a value in one register of the remote device */int modbus_write_register(modbus_t *ctx, int addr, const uint16_t value){ if (ctx == NULL) { errno = EINVAL; return -1; } return write_single(ctx, MODBUS_FC_WRITE_SINGLE_REGISTER, addr, value);}/* Write the bits of the array in the remote device */int modbus_write_bits(modbus_t *ctx, int addr, int nb, const uint8_t *src){ int rc; int i; int byte_count; int req_length; int bit_check = 0; int pos = 0; uint8_t req[MAX_MESSAGE_LENGTH]; if (ctx == NULL) { errno = EINVAL; return -1; } if (nb > MODBUS_MAX_WRITE_BITS) { if (ctx->debug) { fprintf(stderr, "ERROR Writing too many bits (%d > %d)\n", nb, MODBUS_MAX_WRITE_BITS); } errno = EMBMDATA; return -1; } req_length = ctx->backend->build_request_basis(ctx, MODBUS_FC_WRITE_MULTIPLE_COILS, addr, nb, req); byte_count = (nb / 8) + ((nb % 8) ? 1 : 0); req[req_length++] = byte_count; for (i = 0; i < byte_count; i++) { int bit; bit = 0x01; req[req_length] = 0; while ((bit & 0xFF) && (bit_check++ < nb)) { if (src[pos++]) req[req_length] |= bit; else req[req_length] &=~ bit; bit = bit << 1; } req_length++; } rc = send_msg(ctx, req, req_length); if (rc > 0) { uint8_t rsp[MAX_MESSAGE_LENGTH]; rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION); if (rc == -1) return -1; rc = check_confirmation(ctx, req, rsp, rc); } return rc;}/* Write the values from the array to the registers of the remote device */int modbus_write_registers(modbus_t *ctx, int addr, int nb, const uint16_t *src){ int rc; int i; int req_length; int byte_count; uint8_t req[MAX_MESSAGE_LENGTH]; if (ctx == NULL) { errno = EINVAL; return -1; } if (nb > MODBUS_MAX_WRITE_REGISTERS) { if (ctx->debug) { fprintf(stderr, "ERROR Trying to write to too many registers (%d > %d)\n", nb, MODBUS_MAX_WRITE_REGISTERS); } errno = EMBMDATA; return -1; } req_length = ctx->backend->build_request_basis(ctx, MODBUS_FC_WRITE_MULTIPLE_REGISTERS, addr, nb, req); byte_count = nb * 2; req[req_length++] = byte_count; for (i = 0; i < nb; i++) { req[req_length++] = src[i] >> 8; req[req_length++] = src[i] & 0x00FF; } rc = send_msg(ctx, req, req_length); if (rc > 0) { uint8_t rsp[MAX_MESSAGE_LENGTH]; rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION); if (rc == -1) return -1; rc = check_confirmation(ctx, req, rsp, rc); } return rc;}int modbus_mask_write_register(modbus_t *ctx, int addr, uint16_t and_mask, uint16_t or_mask){ int rc; int req_length; /* The request length can not exceed _MIN_REQ_LENGTH - 2 and 4 bytes to * store the masks. The ugly subtraction is there to remove the 'nb' value * (2 bytes) which is not used. */ uint8_t req[_MIN_REQ_LENGTH + 2]; req_length = ctx->backend->build_request_basis(ctx, MODBUS_FC_MASK_WRITE_REGISTER, addr, 0, req); /* HACKISH, count is not used */ req_length -= 2; req[req_length++] = and_mask >> 8; req[req_length++] = and_mask & 0x00ff; req[req_length++] = or_mask >> 8; req[req_length++] = or_mask & 0x00ff; rc = send_msg(ctx, req, req_length); if (rc > 0) { /* Used by write_bit and write_register */ uint8_t rsp[MAX_MESSAGE_LENGTH]; rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION); if (rc == -1) return -1; rc = check_confirmation(ctx, req, rsp, rc); } return rc;}/* Write multiple registers from src array to remote device and read multiple registers from remote device to dest array. */int modbus_write_and_read_registers(modbus_t *ctx, int write_addr, int write_nb, const uint16_t *src, int read_addr, int read_nb, uint16_t *dest){ int rc; int req_length; int i; int byte_count; uint8_t req[MAX_MESSAGE_LENGTH]; uint8_t rsp[MAX_MESSAGE_LENGTH]; if (ctx == NULL) { errno = EINVAL; return -1; } if (write_nb > MODBUS_MAX_WR_WRITE_REGISTERS) { if (ctx->debug) { fprintf(stderr, "ERROR Too many registers to write (%d > %d)\n", write_nb, MODBUS_MAX_WR_WRITE_REGISTERS); } errno = EMBMDATA; return -1; } if (read_nb > MODBUS_MAX_WR_READ_REGISTERS) { if (ctx->debug) { fprintf(stderr, "ERROR Too many registers requested (%d > %d)\n", read_nb, MODBUS_MAX_WR_READ_REGISTERS); } errno = EMBMDATA; return -1; } req_length = ctx->backend->build_request_basis(ctx, MODBUS_FC_WRITE_AND_READ_REGISTERS, read_addr, read_nb, req); req[req_length++] = write_addr >> 8; req[req_length++] = write_addr & 0x00ff; req[req_length++] = write_nb >> 8; req[req_length++] = write_nb & 0x00ff; byte_count = write_nb * 2; req[req_length++] = byte_count; for (i = 0; i < write_nb; i++) { req[req_length++] = src[i] >> 8; req[req_length++] = src[i] & 0x00FF; } rc = send_msg(ctx, req, req_length); if (rc > 0) { int offset; rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION); if (rc == -1) return -1; rc = check_confirmation(ctx, req, rsp, rc); if (rc == -1) return -1; offset = ctx->backend->header_length; for (i = 0; i < rc; i++) { /* shift reg hi_byte to temp OR with lo_byte */ dest[i] = (rsp[offset + 2 + (i << 1)] << 8) | rsp[offset + 3 + (i << 1)]; } } return rc;}/* Send a request to get the slave ID of the device (only available in serial communication). */int modbus_report_slave_id(modbus_t *ctx, int max_dest, uint8_t *dest){ int rc; int req_length; uint8_t req[_MIN_REQ_LENGTH]; if (ctx == NULL || max_dest <= 0) { errno = EINVAL; return -1; } req_length = ctx->backend->build_request_basis(ctx, MODBUS_FC_REPORT_SLAVE_ID, 0, 0, req); /* HACKISH, addr and count are not used */ req_length -= 4; rc = send_msg(ctx, req, req_length); if (rc > 0) { int i; int offset; uint8_t rsp[MAX_MESSAGE_LENGTH]; rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION); if (rc == -1) return -1; rc = check_confirmation(ctx, req, rsp, rc); if (rc == -1) return -1; offset = ctx->backend->header_length + 2; /* Byte count, slave id, run indicator status and additional data. Truncate copy to max_dest. */ for (i=0; i < rc && i < max_dest; i++) { dest[i] = rsp[offset + i]; } } return rc;}void _modbus_init_common(modbus_t *ctx){ /* Slave and socket are initialized to -1 */ ctx->slave = -1; ctx->s = -1; ctx->debug = FALSE; ctx->error_recovery = MODBUS_ERROR_RECOVERY_NONE; ctx->response_timeout.tv_sec = 0; ctx->response_timeout.tv_usec = _RESPONSE_TIMEOUT; ctx->byte_timeout.tv_sec = 0; ctx->byte_timeout.tv_usec = _BYTE_TIMEOUT; ctx->indication_timeout.tv_sec = 0; ctx->indication_timeout.tv_usec = 0;}/* Define the slave number */int modbus_set_slave(modbus_t *ctx, int slave){ if (ctx == NULL) { errno = EINVAL; return -1; } return ctx->backend->set_slave(ctx, slave);}int modbus_get_slave(modbus_t *ctx){ if (ctx == NULL) { errno = EINVAL; return -1; } return ctx->slave;}int modbus_set_error_recovery(modbus_t *ctx, modbus_error_recovery_mode error_recovery){ if (ctx == NULL) { errno = EINVAL; return -1; } /* The type of modbus_error_recovery_mode is unsigned enum */ ctx->error_recovery = (uint8_t) error_recovery; return 0;}int modbus_set_socket(modbus_t *ctx, int s){ if (ctx == NULL) { errno = EINVAL; return -1; } ctx->s = s; return 0;}int modbus_get_socket(modbus_t *ctx){ if (ctx == NULL) { errno = EINVAL; return -1; } return ctx->s;}/* Get the timeout interval used to wait for a response */int modbus_get_response_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec){ if (ctx == NULL) { errno = EINVAL; return -1; } *to_sec = ctx->response_timeout.tv_sec; *to_usec = ctx->response_timeout.tv_usec; return 0;}int modbus_set_response_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec){ if (ctx == NULL || (to_sec == 0 && to_usec == 0) || to_usec > 999999) { errno = EINVAL; return -1; } ctx->response_timeout.tv_sec = to_sec; ctx->response_timeout.tv_usec = to_usec; return 0;}/* Get the timeout interval between two consecutive bytes of a message */int modbus_get_byte_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec){ if (ctx == NULL) { errno = EINVAL; return -1; } *to_sec = ctx->byte_timeout.tv_sec; *to_usec = ctx->byte_timeout.tv_usec; return 0;}int modbus_set_byte_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec){ /* Byte timeout can be disabled when both values are zero */ if (ctx == NULL || to_usec > 999999) { errno = EINVAL; return -1; } ctx->byte_timeout.tv_sec = to_sec; ctx->byte_timeout.tv_usec = to_usec; return 0;}/* Get the timeout interval used by the server to wait for an indication from a client */int modbus_get_indication_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec){ if (ctx == NULL) { errno = EINVAL; return -1; } *to_sec = ctx->indication_timeout.tv_sec; *to_usec = ctx->indication_timeout.tv_usec; return 0;}int modbus_set_indication_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec){ /* Indication timeout can be disabled when both values are zero */ if (ctx == NULL || to_usec > 999999) { errno = EINVAL; return -1; } ctx->indication_timeout.tv_sec = to_sec; ctx->indication_timeout.tv_usec = to_usec; return 0;}int modbus_get_header_length(modbus_t *ctx){ if (ctx == NULL) { errno = EINVAL; return -1; } return ctx->backend->header_length;}int modbus_connect(modbus_t *ctx){ if (ctx == NULL) { errno = EINVAL; return -1; } return ctx->backend->connect(ctx);}void modbus_close(modbus_t *ctx){ if (ctx == NULL) return; ctx->backend->close(ctx);}void modbus_free(modbus_t *ctx){ if (ctx == NULL) return; ctx->backend->free(ctx);}int modbus_set_debug(modbus_t *ctx, int flag){ if (ctx == NULL) { errno = EINVAL; return -1; } ctx->debug = flag; return 0;}/* Allocates 4 arrays to store bits, input bits, registers and inputs registers. The pointers are stored in modbus_mapping structure. The modbus_mapping_new_start_address() function shall return the new allocated structure if successful. Otherwise it shall return NULL and set errno to ENOMEM. */modbus_mapping_t* modbus_mapping_new_start_address( unsigned int start_bits, unsigned int nb_bits, unsigned int start_input_bits, unsigned int nb_input_bits, unsigned int start_registers, unsigned int nb_registers, unsigned int start_input_registers, unsigned int nb_input_registers){ modbus_mapping_t *mb_mapping; mb_mapping = (modbus_mapping_t *)malloc(sizeof(modbus_mapping_t)); if (mb_mapping == NULL) { return NULL; } /* 0X */ mb_mapping->nb_bits = nb_bits; mb_mapping->start_bits = start_bits; if (nb_bits == 0) { mb_mapping->tab_bits = NULL; } else { /* Negative number raises a POSIX error */ mb_mapping->tab_bits = (uint8_t *) malloc(nb_bits * sizeof(uint8_t)); if (mb_mapping->tab_bits == NULL) { free(mb_mapping); return NULL; } memset(mb_mapping->tab_bits, 0, nb_bits * sizeof(uint8_t)); } /* 1X */ mb_mapping->nb_input_bits = nb_input_bits; mb_mapping->start_input_bits = start_input_bits; if (nb_input_bits == 0) { mb_mapping->tab_input_bits = NULL; } else { mb_mapping->tab_input_bits = (uint8_t *) malloc(nb_input_bits * sizeof(uint8_t)); if (mb_mapping->tab_input_bits == NULL) { free(mb_mapping->tab_bits); free(mb_mapping); return NULL; } memset(mb_mapping->tab_input_bits, 0, nb_input_bits * sizeof(uint8_t)); } /* 4X */ mb_mapping->nb_registers = nb_registers; mb_mapping->start_registers = start_registers; if (nb_registers == 0) { mb_mapping->tab_registers = NULL; } else { mb_mapping->tab_registers = (uint16_t *) malloc(nb_registers * sizeof(uint16_t)); if (mb_mapping->tab_registers == NULL) { free(mb_mapping->tab_input_bits); free(mb_mapping->tab_bits); free(mb_mapping); return NULL; } memset(mb_mapping->tab_registers, 0, nb_registers * sizeof(uint16_t)); } /* 3X */ mb_mapping->nb_input_registers = nb_input_registers; mb_mapping->start_input_registers = start_input_registers; if (nb_input_registers == 0) { mb_mapping->tab_input_registers = NULL; } else { mb_mapping->tab_input_registers = (uint16_t *) malloc(nb_input_registers * sizeof(uint16_t)); if (mb_mapping->tab_input_registers == NULL) { free(mb_mapping->tab_registers); free(mb_mapping->tab_input_bits); free(mb_mapping->tab_bits); free(mb_mapping); return NULL; } memset(mb_mapping->tab_input_registers, 0, nb_input_registers * sizeof(uint16_t)); } return mb_mapping;}modbus_mapping_t* modbus_mapping_new(int nb_bits, int nb_input_bits, int nb_registers, int nb_input_registers){ return modbus_mapping_new_start_address( 0, nb_bits, 0, nb_input_bits, 0, nb_registers, 0, nb_input_registers);}/* Frees the 4 arrays */void modbus_mapping_free(modbus_mapping_t *mb_mapping){ if (mb_mapping == NULL) { return; } free(mb_mapping->tab_input_registers); free(mb_mapping->tab_registers); free(mb_mapping->tab_input_bits); free(mb_mapping->tab_bits); free(mb_mapping);}#ifndef HAVE_STRLCPY/* * Function strlcpy was originally developed by * Todd C. Miller 
             
               to simplify writing secure code. * See ftp://ftp.openbsd.org/pub/OpenBSD/src/lib/libc/string/strlcpy.3 * for more information. * * Thank you Ulrich Drepper... not! * * Copy src to string dest of size dest_size. At most dest_size-1 characters * will be copied. Always NUL terminates (unless dest_size == 0). Returns * strlen(src); if retval >= dest_size, truncation occurred. */size_t strlcpy(char *dest, const char *src, size_t dest_size){ register char *d = dest; register const char *s = src; register size_t n = dest_size; /* Copy as many bytes as will fit */ if (n != 0 && --n != 0) { do { if ((*d++ = *s++) == 0) break; } while (--n != 0); } /* Not enough room in dest, add NUL and traverse rest of src */ if (n == 0) { if (dest_size != 0) *d = '\0'; /* NUL-terminate dest */ while (*s++) ; } return (s - src - 1); /* count does not include NUL */}#endif
             
            
           
          
         
        
       
      
     
    
   

04. 预留

05. 附录

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