linux http请求报文简单响应

这几天有点忙，先放代码，之后再来改注释.

使用到不常见的函数：

char* strpbrk(char* str1,char* str2)

        str1被检索的字符串，str2要在str1中匹配的字符列表（代码中有空格）

        成功返回字符在str1中位置的指针

int strcasecmp(char* str1,char* str2)

        和strcmp函数作用相同，区别在与：此函数对大小写不敏感

int strspn(char* str1,char* str2)

        str1要被检索字符串，str2要在str1中匹配的字符列表（代码中有空格）

        成功返回第一个不在str2中出现的字符下标

        注意：strspn("ABC","BC")==0

char* strchr(char* str, int c)

        str被检索的字符串，c要查找的字符

        成功返回str中第一个值为c的字符的指针

char* strrchr(char* str,int c)

        str被检索的字符串，c要查找的字符

        成功返回str中最后一个值为c的字符的指针

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>

const size_t BUFFER_SIZE = 4096;

enum CHECK_STATE
{
	CHECK_STATE_REQUESTLINE = 0,
	CHECK_STATE_HEADER
};
enum LINE_STATUS
{
	LINE_OK = 0,
	LINE_BAD,
	LINE_OPEN
};
enum HTTP_CODE
{
	NO_REQUEST,
	GET_REQUEST,
	BAD_REQUEST,
	FORBIDDEN_REQUEST,
	INTERNAL_ERROR,
	CLOSED_CONNECTION
};

static const char *szret[] = {"I get a correct result\n", "Something wrong\n"};

LINE_STATUS parse_line(char *buffer, int &checked_index, int &read_index)
{
	char temp;
	for (; checked_index < read_index; ++checked_index)
	{
		temp = buffer[checked_index];
		if (temp == '\r')
		{
			if ((checked_index + 1) == read_index)
				return LINE_OPEN;
			else if (buffer[checked_index + 1] == '\n')
			{
				buffer[checked_index++] = '\0';
				buffer[checked_index++] = '\0';
				return LINE_OK;
			}
			return LINE_BAD;
		}
		else if (temp == '\n')
		{
			if ((checked_index > 1) && buffer[checked_index - 1] == '\r')
			{
				buffer[checked_index - 1] = '\0';
				buffer[checked_index++] = '\0';
				return LINE_OK;
			}
			return LINE_BAD;
		}
	}
	return LINE_OPEN;
}

HTTP_CODE parse_requestline(char *temp, CHECK_STATE &checkstate)
{
	char *url = strpbrk(temp, " \t");
	if (!url)
		return BAD_REQUEST;
	*url++ = '\0';

	char *method = temp;
	if (strcasecmp(method, "GET") == 0)
		printf("The request method is GET\n");
	else
		return BAD_REQUEST;

	url += strspn(url, " \t"); //
	char *version = strpbrk(url, " \t");
	if (!version)
		return BAD_REQUEST;

	*version++ = '\0';
	version += strspn(version, " \t");

	if (strcasecmp(version, "HTTP/1.1") != 0)
		return BAD_REQUEST;

	if (strncasecmp(url, "http://", 7) == 0)
	{
		url += 7;
		url = strchr(url, '/');
	}

	if (!url || url[0] != '/')
		return BAD_REQUEST;
	printf("The request URL is: %s\n", url);
	checkstate = CHECK_STATE_HEADER;
	return NO_REQUEST;
}

HTTP_CODE parse_headers(char *temp)
{
	if (temp[0] == '\0')
		return GET_REQUEST;
	else if (strncasecmp(temp, "Host:", 5) == 0)
	{
		temp += 5;
		temp += strspn(temp, " \t");
		printf("the request host is: %s\n", temp);
	}
	else
		printf("I can not handle this header\n");
	return NO_REQUEST;
}

HTTP_CODE parse_content(char *buffer, int &checked_index, CHECK_STATE &checkstate, int &read_index, int &start_line)
{
	LINE_STATUS linestatus = LINE_OK;
	HTTP_CODE retcode = NO_REQUEST;
	while ((linestatus = parse_line(buffer, checked_index, read_index)) == LINE_OK)
	{
		char *temp = buffer + start_line;
		start_line = checked_index;
		switch (checkstate)
		{
		case CHECK_STATE_REQUESTLINE:
		{
			retcode = parse_requestline(temp, checkstate);
			if (retcode == BAD_REQUEST)
				return BAD_REQUEST;
			break;
		}
		case CHECK_STATE_HEADER:
		{
			retcode = parse_headers(temp);
			if (retcode == BAD_REQUEST)
				return BAD_REQUEST;
			else if (retcode == GET_REQUEST)
				return GET_REQUEST;
			break;
		}
		default:
		{
			return INTERNAL_ERROR;
		}
		}
	}
	if (linestatus == LINE_OPEN)
		return NO_REQUEST;
	else
		return BAD_REQUEST;
}

int main(int argc, char *argv[])
{
	if (argc <= 2)
	{
		printf("usage: %s ip_address port_number\n", basename(argv[0]));
		return 1;
	}
	const char *ip = argv[1];
	int port = atoi(argv[2]);
	struct sockaddr_in address;
	memset(&address, 0, sizeof(address));
	address.sin_family = AF_INET;
	// address.sin_addr.s_addr=htonl(INADDR_ANY);
	inet_pton(AF_INET, ip, &address.sin_addr);
	address.sin_port = htons(port);

	int listenfd = socket(PF_INET, SOCK_STREAM, 0);
	assert(listenfd >= 0);
	int ret = bind(listenfd, (struct sockaddr *)&address, sizeof(address));
	assert(ret != -1);
	ret = listen(listenfd, 5);
	assert(ret != -1);
	struct sockaddr_in client_address;
	socklen_t client_addrlength = sizeof(client_address);
	int fd = accept(listenfd, (struct sockaddr *)&client_address, &client_addrlength);

	if (fd < 0)
	{
		printf("errno is: %d mean: %s\n", errno, strerror(errno));
		// perror("errno mean: ");
	}
	else
	{
		char buffer[BUFFER_SIZE];
		memset(buffer, '\0', BUFFER_SIZE);
		int data_read = 0, read_index = 0, checked_index = 0, start_line = 0;
		CHECK_STATE checkstate = CHECK_STATE_REQUESTLINE;
		while (1)
		{
			data_read = recv(fd, buffer + read_index, BUFFER_SIZE - read_index, 0);
			if (data_read == -1)
			{
				printf("reading failed\n");
				break;
			}
			else if (data_read == 0)
			{
				printf("remote client has closed the connection\n");
				break;
			}
			read_index += data_read;
			HTTP_CODE result = parse_content(buffer, checked_index, checkstate, read_index, start_line);

			if (result == NO_REQUEST)
				continue;
			else if (result == GET_REQUEST)
			{
				send(fd, szret[0], strlen(szret[0]), 0);
				break;
			}
			else
			{
				send(fd, szret[1], strlen(szret[1]), 0);
				break;
			}
		}
		close(fd);
	}
	close(listenfd);
	return 0;
}