diff --git a/image_tagger.c b/image_tagger.c new file mode 100644 index 0000000000000000000000000000000000000000..d099cc5b698945560620a6bdcac0e0e31e460b8f --- /dev/null +++ b/image_tagger.c @@ -0,0 +1,266 @@ +#include <errno.h> +#include <stdbool.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +#include <arpa/inet.h> +#include <fcntl.h> +#include <netdb.h> +#include <netinet/in.h> +#include <strings.h> +#include <sys/select.h> +#include <sys/sendfile.h> +#include <sys/socket.h> +#include <sys/stat.h> +#include <sys/types.h> +#include <unistd.h> + +// constants +static char const * const HTTP_200_FORMAT = "HTTP/1.1 200 OK\r\n\ +Content-Type: text/html\r\n\ +Content-Length: %ld\r\n\r\n"; +static char const * const HTTP_400 = "HTTP/1.1 400 Bad Request\r\nContent-Length: 0\r\n\r\n"; +static int const HTTP_400_LENGTH = 47; +static char const * const HTTP_404 = "HTTP/1.1 404 Not Found\r\nContent-Length: 0\r\n\r\n"; +static int const HTTP_404_LENGTH = 45; + +// represents the types of method +typedef enum +{ + GET, + POST, + UNKNOWN +} METHOD; + +static bool handle_http_request(int sockfd) +{ + // try to read the request + char buff[2049]; + int n = read(sockfd, buff, 2049); + if (n <= 0) + { + if (n < 0) + perror("read"); + else + printf("socket %d close the connection\n", sockfd); + return false; + } + + // terminate the string + buff[n] = 0; + + char * curr = buff; + + // parse the method + METHOD method = UNKNOWN; + if (strncmp(curr, "GET ", 4) == 0) + { + curr += 4; + method = GET; + } + else if (strncmp(curr, "POST ", 5) == 0) + { + curr += 5; + method = POST; + } + else if (write(sockfd, HTTP_400, HTTP_400_LENGTH) < 0) + { + perror("write"); + return false; + } + + // sanitise the URI + while (*curr == '.' || *curr == '/') + ++curr; + // assume the only valid request URI is "/" but it can be modified to accept more files + if (*curr == ' ') + if (method == GET) + { + // get the size of the file + struct stat st; + stat("1_intro.html", &st); + n = sprintf(buff, HTTP_200_FORMAT, st.st_size); + // send the header first + if (write(sockfd, buff, n) < 0) + { + perror("write"); + return false; + } + // send the file + int filefd = open("1_intro.html", O_RDONLY); + do + { + n = sendfile(sockfd, filefd, NULL, 2048); + } + while (n > 0); + if (n < 0) + { + perror("sendfile"); + close(filefd); + return false; + } + close(filefd); + } + else if (method == POST) + { + // locate the username, it is safe to do so in this sample code, but usually the result is expected to be + // copied to another buffer using strcpy or strncpy to ensure that it will not be overwritten. + char * username = strstr(buff, "user=") + 5; + int username_length = strlen(username); + // the length needs to include the "Hi, " before the username + long added_length = username_length + 4; + + // get the size of the file + struct stat st; + stat("2_start.html", &st); + // increase file size to accommodate the username + long size = st.st_size + added_length; + n = sprintf(buff, HTTP_200_FORMAT, size); + // send the header first + if (write(sockfd, buff, n) < 0) + { + perror("write"); + return false; + } + // read the content of the HTML file + int filefd = open("2_start.html", O_RDONLY); + n = read(filefd, buff, 2048); + if (n < 0) + { + perror("read"); + close(filefd); + return false; + } + close(filefd); + //move the trailing part backward + int p2; + /*for (p1 = size - 1, p2 = p1 - added_length; p1 >= size - 25; --p1, --p2) + buff[p1] = buff[p2]; + ++p2;*/ + // put the separator + buff[p2++] = 'H'; + buff[p2++] ='i'; + buff[p2++] = ','; + buff[p2++] = ' '; + // copy the username + strncpy(buff + p2, username, username_length); + if (write(sockfd, buff, size) < 0) + { + perror("write"); + return false; + } + } + else + // never used, just for completeness + fprintf(stderr, "no other methods supported"); + // send 404 + else if (write(sockfd, HTTP_404, HTTP_404_LENGTH) < 0) + { + perror("write"); + return false; + } + + return true; +} + +int main(int argc, char * argv[]) +{ + if (argc < 3) + { + fprintf(stderr, "usage: %s ip port\n", argv[0]); + return 0; + } + + // create TCP socket which only accept IPv4 + int sockfd = socket(AF_INET, SOCK_STREAM, 0); + if (sockfd < 0) + { + perror("socket"); + exit(EXIT_FAILURE); + } + + // reuse the socket if possible + int const reuse = 1; + if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(int)) < 0) + { + perror("setsockopt"); + exit(EXIT_FAILURE); + } + + // create and initialise address we will listen on + struct sockaddr_in serv_addr; + bzero(&serv_addr, sizeof(serv_addr)); + serv_addr.sin_family = AF_INET; + // if ip parameter is not specified + serv_addr.sin_addr.s_addr = inet_addr(argv[1]); + serv_addr.sin_port = htons(atoi(argv[2])); + + // bind address to socket + if (bind(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) + { + perror("bind"); + exit(EXIT_FAILURE); + } + + // listen on the socket + listen(sockfd, 5); + + // initialise an active file descriptors set + fd_set masterfds; + FD_ZERO(&masterfds); + FD_SET(sockfd, &masterfds); + // record the maximum socket number + int maxfd = sockfd; + + while (1) + { + // monitor file descriptors + fd_set readfds = masterfds; + if (select(FD_SETSIZE, &readfds, NULL, NULL, NULL) < 0) + { + perror("select"); + exit(EXIT_FAILURE); + } + + // loop all possible descriptor + for (int i = 0; i <= maxfd; ++i) + // determine if the current file descriptor is active + if (FD_ISSET(i, &readfds)) + { + // create new socket if there is new incoming connection request + if (i == sockfd) + { + struct sockaddr_in cliaddr; + socklen_t clilen = sizeof(cliaddr); + int newsockfd = accept(sockfd, (struct sockaddr *)&cliaddr, &clilen); + if (newsockfd < 0) + perror("accept"); + else + { + // add the socket to the set + FD_SET(newsockfd, &masterfds); + // update the maximum tracker + if (newsockfd > maxfd) + maxfd = newsockfd; + // print out the IP and the socket number + char ip[INET_ADDRSTRLEN]; + printf( + "new connection from %s on socket %d\n", + // convert to human readable string + inet_ntop(cliaddr.sin_family, &cliaddr.sin_addr, ip, INET_ADDRSTRLEN), + newsockfd + ); + } + } + // a request is sent from the client + else if (!handle_http_request(i)) + { + close(i); + FD_CLR(i, &masterfds); + } + } + } + + return 0; +}