homework for the study

webserver.c

/* webserver.c */

#include <cnaiapi.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <stdbool.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/sendfile.h>
#include <errno.h>
#include <signal.h>

const char * HTDOCS = "htdocs/";
const char * INDEX_FILE = "index.html";


/*
 * Writes a HTTP-Response to the connection
 */
bool initialResponseLine(connection _conn, char * _httpVersion, char * _responseStatusCode, char * _reasonPhrase)
{
	char response[100] = "HTTP/";
	strcat(response, strcat(_httpVersion, " ")); 
	strcat(response, strcat(_responseStatusCode, " ")); 
	strcat(response, _reasonPhrase);
	strcat(response, "\n");
	
	int ret = write(STDOUT_FILENO, response, strlen(response));
	if (ret < 0) {
		return false;
	}
	
	return true;
}

const char * mimes[][2] = {
	{".jpg", "image/jpeg"},
	{".jpeg", "image/jpeg"},
	{".html", "text/html"},
	{".htm", "text/html"},
};

// get mime type of file name
char * getMime(const char * file) {
	char *ext = strrchr(file, '.');

	if (ext == NULL)
		return "text/plain";

	int i;
	for (i = 0; i < sizeof(mimes); i++) {
		if (strcmp(ext, mimes[i][0]) == 0) {
			return (char*)mimes[i][1];
		}
	}

	return "text/plain";
}



int main(int argc, char *argv[])
{
	signal(SIGCLD, SIG_IGN);
	
	connection conn;
	appnum app = atoi(argv[1]);	
	
	// Holds the complete request
	char requestBuffer[1024] = "";
	int requestLength = 0;
	
	// Holds the requested file path, not it's content
	char getBuffer[1024];
	
	// Holds the length of the path to the file
	int getLength = 0;


	while (true) {

		conn = await_contact(app);
		if (conn < 0) {
			printf("Fehler bei der Verbindung\n");
			return 1;
		}
	
		// to connect clients simultaniously
		pid_t pid = fork();
		
		// child creation unsuccessful
		if (pid < 0) {
			printf("Fehler in child creation\n");
			end_contact(conn);
		}
		else if (pid > 0) {
			printf("Parent\n");
			end_contact(conn);
		}
		else {
			// read input -> blocks the thread until data is recieved
			
			// Holds the Request from Client
			char readBuffer[1024];
	
			int l;
			while ((l = read(conn, readBuffer, 1024))) {
				if (l < 0) {
					printf("%s\n", strerror(errno));
					//end_contact(conn);
					exit(1);
				}
						
				strncat(requestBuffer, readBuffer, l);
				memset(&readBuffer[0], 0, sizeof(readBuffer));
			
				char* requestEnd = strstr(requestBuffer, "\r\n\r\n");

				if (requestEnd != NULL) {
					break;
				}
			}
			
			// check for GET-Request
			int isGet = strncmp("GET", requestBuffer, 3);
			if (isGet != 0) {
				initialResponseLine(conn, "1.0", "501", "Not Implemented");
				exit(1);
			}
			
			// parsing the request from 5. symbol in readBuffer from Client (start of path)
			int i;
			requestLength = strlen(requestBuffer);
			printf("%d\n", requestLength);
			for (i = 5; i < requestLength; i++) {
				// check man page for comaprison
				if (isspace(requestBuffer[i]) != false) {
					break;
				}
					
				getBuffer[getLength++] = requestBuffer[i];
			}
			
			
			// deliver requested file

			// if only "/" take index.html	
			if ( strlen(getBuffer) == 0 ) {
				strcat(getBuffer, INDEX_FILE);
			}
			
			char filePath[1024] = "";
			strcat(filePath, HTDOCS);
			strcat(filePath, getBuffer);
			
			// open file -> http://www.win-tux.de/c_018_025.htm#RxxobKap01802504002A2F1F02418C
			int fd = open(filePath, O_RDONLY);
			
			// if an error occurs -> 404
			if (fd < 0) {
				initialResponseLine(conn, "1.0", "404", "Not Found\r");
				printf("%s\r", filePath);
				exit(0);
			}
			
			struct stat st;
			fstat (fd, &st);
			
			char responseHeader[1024];
			int len = sprintf(responseHeader, "HTTP/1.0 200 OK\r\nOK\r\nContent-Type: %s\r\nContent-Length: %ld\r\n\r\n", getMime(filePath), st.st_size);
			
			write(conn, responseHeader, len);
			int r = sendfile(conn, fd, 0, st.st_size);
			if (r < 0) {
				printf("Fehler beim Datei senden: %s", strerror(errno));
			}
			
			close(fd);
			exit(0);
		}
	}
	
	end_contact(conn);
	return 0;
}