1.如何用C语言实现atoi()函数
2.编译器如何把数字转为二进制的源码?
3.c语言ping程序中文注释
源码.jpg)
如何用C语言实现atoi()函数
用 标准函数 sscanf 就可以了。
long my_atoi(char *str){
long i;
sscanf(str,源码"%ld",&i);
return i;
}
字符常量调用：
printf("%d %d",my_atoi("-"), my_atoi(""));
字符变量调用:
char a[]="-";
int k;
k = my_atoi(a);
---------------------------
考究一点,函数里加一个转换错误检查：
if ( sscanf(str,"%ld",&i) != 1) { printf("Covertion error in my_atoi !"); ....};
编译器如何把数字转为二进制的?
编译器如何将数字转换为二进制形式涉及到将源代码解析并转换为可执行代码的过程。此过程通常分为几个步骤。源码首先，源码编译器需要读取源代码，源码并将其转换为一系列可操作的源码dataframe源码符号，也就是源码所谓的"词法单位"或"词法分析"。接下来是源码语法分析阶段，其中编译器检查源代码的源码结构是否符合程序设计语言的语法规则。一旦语法正确，源码代码将被转换为中间代码（如抽象语法树，源码AST）。源码
数字转换为二进制的源码分享资源源码处理则位于这一过程中。编译器会识别源代码中的源码数字，并将它们转换为特定的源码二进制形式。通常，这一过程在词法分析和语法分析阶段完成，由编译器内部函数或库自动处理。例如，源码包编译过程C语言中使用`atoi`函数来将字符串转换为整数，而整数转换为二进制通常在编译器的后端优化阶段进行。
以数字5为例，转换为二进制形式的过程如下：首先，编译器识别数字5，并将其与二进制系统相关联。zfs 源码之旅 arc在二进制系统中，数字5可以表示为。这个过程依赖于计算机内部的硬件和操作系统如何处理和存储数据。通常，计算机使用二进制位（比特）来表示数字，其中每一位可以是半自动 ea 源码0或1。在现代计算机中，数字通常以位或位整数形式存储，使得数字转换为二进制的过程涉及将数字分解为其二进制位的组合。
编译器在将源代码转换为机器代码时，也会考虑数字在计算机内部的表示方式，例如有符号整数（正负数）或无符号整数。编译器会根据目标平台（如特定的CPU架构）和操作系统进行优化，以确保生成的代码在执行时能够高效地将数字表示为二进制形式。
在现代编译器中，这个过程通常是自动化的，编译器的内部机制负责处理数字到二进制的转换。具体来说，编译器会使用一系列的指令和算法，将数字转换为二进制形式，然后生成对应的机器指令。这些机器指令最终会被解释器或处理器执行，将数字以二进制形式处理和运算。
c语言ping程序中文注释
编写自己的一个ping程序,可以说是许多人迈出网络编程的第一步吧!!这个ping程序的源代码经过我的修改和调试,基本上可以取代windows中自带的ping程序. 各个模块后都有我的详细注释和修改日志,希望能够对大家的学习有所帮助!!
/* 本程序的主要源代码来自MSDN网站, 笔者只是做了一些改进和注释! 另外需要注意的是在Build之前,必须加入ws2_.lib库文件,否则会提示"error LNK:"的错误！*/
Version 1.1 修改记录:
<1> 解决了socket阻塞的问题,从而能够正确地处理超时的请求!
<2> 增加了由用户控制发送ICMP包的数目的功能(即命令的第二个参数)
<3> 增加了对ping结果的统计功能.
#pragma pack(4)
#include "winsock2.h"
#include "stdlib.h"
#include "stdio.h"
#define ICMP_ECHO 8
#define ICMP_ECHOREPLY 0
#define ICMP_MIN 8 // minimum 8 byte icmp packet (just header)
/* The IP header */
typedef struct iphdr {
unsigned int h_len:4; // length of the header
unsigned int version:4; // Version of IP
unsigned char tos; // Type of service
unsigned short total_len; // total length of the packet
unsigned short ident; // unique identifier
unsigned short frag_and_flags; // flags
unsigned char ttl;
unsigned char proto; // protocol (TCP, UDP etc)
unsigned short checksum; // IP checksum
unsigned int sourceIP;
unsigned int destIP;
}IpHeader;
//
// ICMP header
//
typedef struct icmphdr {
BYTE i_type;
BYTE i_code; /* type sub code */
USHORT i_cksum;
USHORT i_id;
USHORT i_seq;
/* This is not the std header, but we reserve space for time */
ULONG timestamp;
}IcmpHeader;
#define STATUS_FAILED 0xFFFF
#define DEF_PACKET_SIZE
#define DEF_PACKET_NUMBER 4 /* 发送数据报的个数 */
#define MAX_PACKET
#define xmalloc(s) HeapAlloc(GetProcessHeap(),HEAP_ZERO_MEMORY,(s))
#define xfree(p) HeapFree (GetProcessHeap(),0,(p))
void fill_icmp_data(char *, int);
USHORT checksum(USHORT *, int);
int decode_resp(char *,int ,struct sockaddr_in *);
void Usage(char *progname){
fprintf(stderr,"Usage:\n");
fprintf(stderr,"%s [number of packets] [data_size]\n",progname);
fprintf(stderr,"datasize can be up to 1Kb\n");
ExitProcess(STATUS_FAILED);
}
int main(int argc, char **argv){
WSADATA wsaData;
SOCKET sockRaw;
struct sockaddr_in dest,from;
struct hostent * hp;
int bread,datasize,times;
int fromlen = sizeof(from);
int timeout = ;
int statistic = 0; /* 用于统计结果 */
char *dest_ip;
char *icmp_data;
char *recvbuf;
unsigned int addr=0;
USHORT seq_no = 0;
if (WSAStartup(MAKEWORD(2,1),&wsaData) != 0){
fprintf(stderr,"WSAStartup failed: %d\n",GetLastError());
ExitProcess(STATUS_FAILED);
}
if (argc <2 ) {
Usage(argv[0]);
}
sockRaw = WSASocket(AF_INET,SOCK_RAW,IPPROTO_ICMP,NULL, 0,WSA_FLAG_OVERLAPPED);
//
//注：为了使用发送接收超时设置(即设置SO_RCVTIMEO, SO_SNDTIMEO)，
// 必须将标志位设为WSA_FLAG_OVERLAPPED !
//
if (sockRaw == INVALID_SOCKET) {
fprintf(stderr,"WSASocket() failed: %d\n",WSAGetLastError());
ExitProcess(STATUS_FAILED);
}
bread = setsockopt(sockRaw,SOL_SOCKET,SO_RCVTIMEO,(char*)&timeout,
sizeof(timeout));
if(bread == SOCKET_ERROR) {
fprintf(stderr,"failed to set recv timeout: %d\n",WSAGetLastError());
ExitProcess(STATUS_FAILED);
}
timeout = ;
bread = setsockopt(sockRaw,SOL_SOCKET,SO_SNDTIMEO,(char*)&timeout,
sizeof(timeout));
if(bread == SOCKET_ERROR) {
fprintf(stderr,"failed to set send timeout: %d\n",WSAGetLastError());
ExitProcess(STATUS_FAILED);
}
memset(&dest,0,sizeof(dest));
hp = gethostbyname(argv[1]);
if (!hp){
addr = inet_addr(argv[1]);
}
if ((!hp) && (addr == INADDR_NONE) ) {
fprintf(stderr,"Unable to resolve %s\n",argv[1]);
ExitProcess(STATUS_FAILED);
}
if (hp != NULL)
memcpy(&(dest.sin_addr),hp->h_addr,hp->h_length);
else
dest.sin_addr.s_addr = addr;
if (hp)
dest.sin_family = hp->h_addrtype;
else
dest.sin_family = AF_INET;
dest_ip = inet_ntoa(dest.sin_addr);
//
// atoi函数原型是: int atoi( const char *string );
// The return value is 0 if the input cannot be converted to an integer !
//
if(argc>2)
{
times=atoi(argv[2]);
if(times == 0)
times=DEF_PACKET_NUMBER;
}
else
times=DEF_PACKET_NUMBER;
if (argc >3)
{
datasize = atoi(argv[3]);
if (datasize == 0)
datasize = DEF_PACKET_SIZE;
if (datasize >) /* 用户给出的数据包大小太大 */
{
fprintf(stderr,"WARNING : data_size is too large !\n");
datasize = DEF_PACKET_SIZE;
}
}
else
datasize = DEF_PACKET_SIZE;
datasize += sizeof(IcmpHeader);
icmp_data = (char*)xmalloc(MAX_PACKET);
recvbuf = (char*)xmalloc(MAX_PACKET);
if (!icmp_data) {
fprintf(stderr,"HeapAlloc failed %d\n",GetLastError());
ExitProcess(STATUS_FAILED);
}
memset(icmp_data,0,MAX_PACKET);
fill_icmp_data(icmp_data,datasize);
//
//显示提示信息
//
fprintf(stdout,"\nPinging %s ....\n\n",dest_ip);
for(int i=0;i{
int bwrote;
((IcmpHeader*)icmp_data)->i_cksum = 0;
((IcmpHeader*)icmp_data)->timestamp = GetTickCount();
((IcmpHeader*)icmp_data)->i_seq = seq_no++;
((IcmpHeader*)icmp_data)->i_cksum = checksum((USHORT*)icmp_data,datasize);
bwrote = sendto(sockRaw,icmp_data,datasize,0,(struct sockaddr*)&dest,sizeof(dest));
if (bwrote == SOCKET_ERROR){
if (WSAGetLastError() == WSAETIMEDOUT) {
printf("Request timed out.\n");
continue;
}
fprintf(stderr,"sendto failed: %d\n",WSAGetLastError());
ExitProcess(STATUS_FAILED);
}
if (bwrote < datasize ) {
fprintf(stdout,"Wrote %d bytes\n",bwrote);
}
bread = recvfrom(sockRaw,recvbuf,MAX_PACKET,0,(struct sockaddr*)&from,&fromlen);
if (bread == SOCKET_ERROR){
if (WSAGetLastError() == WSAETIMEDOUT) {
printf("Request timed out.\n");
continue;
}
fprintf(stderr,"recvfrom failed: %d\n",WSAGetLastError());
ExitProcess(STATUS_FAILED);
}
if(!decode_resp(recvbuf,bread,&from))
statistic++; /* 成功接收的数目++ */
Sleep();
}
/
*Display the statistic result
*/
fprintf(stdout,"\nPing statistics for %s \n",dest_ip);
fprintf(stdout," Packets: Sent = %d,Received = %d, Lost = %d (%2.0f%% loss)\n",times,
statistic,(times-statistic),(float)(times-statistic)/times*);
WSACleanup();
return 0;
}
/*
The response is an IP packet. We must decode the IP header to locate
the ICMP data
*/
int decode_resp(char *buf, int bytes,struct sockaddr_in *from) {
IpHeader *iphdr;
IcmpHeader *icmphdr;
unsigned short iphdrlen;
iphdr = (IpHeader *)buf;
iphdrlen = (iphdr->h_len) * 4 ; // number of -bit words *4 = bytes
if (bytes < iphdrlen + ICMP_MIN) {
printf("Too few bytes from %s\n",inet_ntoa(from->sin_addr));
}
icmphdr = (IcmpHeader*)(buf + iphdrlen);
if (icmphdr->i_type != ICMP_ECHOREPLY) {
fprintf(stderr,"non-echo type %d recvd\n",icmphdr->i_type);
return 1;
}
if (icmphdr->i_id != (USHORT)GetCurrentProcessId()) {
fprintf(stderr,"someone else''s packet!\n");
return 1;
}
printf("%d bytes from %s:",bytes, inet_ntoa(from->sin_addr));
printf(" icmp_seq = %d. ",icmphdr->i_seq);
printf(" time: %d ms ",GetTickCount()-icmphdr->timestamp);
printf("\n");
return 0;
}
USHORT checksum(USHORT *buffer, int size) {
unsigned long cksum=0;
while(size >1) {
cksum+=*buffer++;
size -=sizeof(USHORT);
}
if(size) {
cksum += *(UCHAR*)buffer;
}
cksum = (cksum >> ) + (cksum & 0xffff);
cksum += (cksum >>);
return (USHORT)(~cksum);
}
/*
Helper function to fill in various stuff in our ICMP request.
*/
void fill_icmp_data(char * icmp_data, int datasize){
IcmpHeader *icmp_hdr;
char *datapart;
icmp_hdr = (IcmpHeader*)icmp_data;
icmp_hdr->i_type = ICMP_ECHO;
icmp_hdr->i_code = 0;
icmp_hdr->i_id = (USHORT)GetCurrentProcessId();
icmp_hdr->i_cksum = 0;
icmp_hdr->i_seq = 0;
datapart = icmp_data + sizeof(IcmpHeader);
//
// Place some junk in the buffer.
//
memset(datapart,''E'', datasize - sizeof(IcmpHeader));
}
/