usbloadergx/source/network/http.c

#include "http.h"

/**
 * Emptyblock is a statically defined variable for functions to return if they are unable
 * to complete a request
 */
const struct block emptyblock = {0, NULL};

//The maximum amount of bytes to send per net_write() call
#define NET_BUFFER_SIZE 1024

// Write our message to the server
static s32 send_message(s32 server, char *msg) {
    s32 bytes_transferred = 0;
    s32 remaining = strlen(msg);
    while (remaining) {
        if ((bytes_transferred = net_write(server, msg, remaining > NET_BUFFER_SIZE ? NET_BUFFER_SIZE : remaining)) > 0) {
            remaining -= bytes_transferred;
            usleep (20 * 1000);
        } else if (bytes_transferred < 0) {
            return bytes_transferred;
        } else {
            return -ENODATA;
        }
    }
    return 0;
}

/**
 * Connect to a remote server via TCP on a specified port
 *
 * @param u32 ip address of the server to connect to
 * @param u32 the port to connect to on the server
 * @return s32 The connection to the server (negative number if connection could not be established)
 */
static s32 server_connect(u32 ipaddress, u32 socket_port) {
    //Initialize socket
    s32 connection = net_socket(AF_INET, SOCK_STREAM, IPPROTO_IP);
    if (connection < 0) return connection;

    struct sockaddr_in connect_addr;
    memset(&connect_addr, 0, sizeof(connect_addr));
    connect_addr.sin_family = AF_INET;
    connect_addr.sin_port = socket_port;
    connect_addr.sin_addr.s_addr= ipaddress;

    //Attemt to open the socket
    if (net_connect(connection, (struct sockaddr*)&connect_addr, sizeof(connect_addr)) == -1) {
        net_close(connection);
        return -1;
    }
    return connection;
}

//The amount of memory in bytes reserved initially to store the HTTP response in
//Be careful in increasing this number, reading from a socket on the Wii
//will fail if you request more than 20k or so
#define HTTP_BUFFER_SIZE 1024 * 5

//The amount of memory the buffer should expanded with if the buffer is full
#define HTTP_BUFFER_GROWTH 1024 * 5

/**
 * This function reads all the data from a connection into a buffer which it returns.
 * It will return an empty buffer if something doesn't go as planned
 *
 * @param s32 connection The connection identifier to suck the response out of
 * @return block A 'block' struct (see http.h) in which the buffer is located
 */
struct block read_message(s32 connection) {
    //Create a block of memory to put in the response
    struct block buffer;
    buffer.data = malloc(HTTP_BUFFER_SIZE);
    buffer.size = HTTP_BUFFER_SIZE;

    if (buffer.data == NULL) {
        return emptyblock;
    }

    //The offset variable always points to the first byte of memory that is free in the buffer
    u32 offset = 0;

    while (1) {
        //Fill the buffer with a new batch of bytes from the connection,
        //starting from where we left of in the buffer till the end of the buffer
        s32 bytes_read = net_read(connection, buffer.data + offset, buffer.size - offset);

        //Anything below 0 is an error in the connection
        if (bytes_read < 0) {
            //printf("Connection error from net_read()  Errorcode: %i\n", bytes_read);
            return emptyblock;
        }

        //No more bytes were read into the buffer,
        //we assume this means the HTTP response is done
        if (bytes_read == 0) {
            break;
        }

        offset += bytes_read;

        //Check if we have enough buffer left over,
        //if not expand it with an additional HTTP_BUFFER_GROWTH worth of bytes
        if (offset >= buffer.size) {
            buffer.size += HTTP_BUFFER_GROWTH;
            buffer.data = realloc(buffer.data, buffer.size);

            if (buffer.data == NULL) {
                return emptyblock;
            }
        }
    }

    //At the end of above loop offset should be precisely the amount of bytes that were read from the connection
    buffer.size = offset;

    //Shrink the size of the buffer so the data fits exactly in it
    realloc(buffer.data, buffer.size);

    return buffer;
}

/**
 * Downloads the contents of a URL to memory
 * This method is not threadsafe (because networking is not threadsafe on the Wii)
 */
struct block downloadfile(const char *url) {
    //Check if the url starts with "http://", if not it is not considered a valid url
    if (strncmp(url, "http://", strlen("http://")) != 0) {
        //printf("URL '%s' doesn't start with 'http://'\n", url);
        return emptyblock;
    }

    //Locate the path part of the url by searching for '/' past "http://"
    char *path = strchr(url + strlen("http://"), '/');

    //At the very least the url has to end with '/', ending with just a domain is invalid
    if (path == NULL) {
        //printf("URL '%s' has no PATH part\n", url);
        return emptyblock;
    }

    //Extract the domain part out of the url
    int domainlength = path - url - strlen("http://");

    if (domainlength == 0) {
        //printf("No domain part in URL '%s'\n", url);
        return emptyblock;
    }

    char domain[domainlength + 1];
    strncpy(domain, url + strlen("http://"), domainlength);
    domain[domainlength] = '\0';

    //Parsing of the URL is done, start making an actual connection
    u32 ipaddress = getipbynamecached(domain);

    if (ipaddress == 0) {
        //printf("\ndomain %s could not be resolved", domain);
        return emptyblock;
    }


    s32 connection = server_connect(ipaddress, 80);

    if (connection < 0) {
        //printf("Error establishing connection");
        return emptyblock;
    }

    //Form a nice request header to send to the webserver
    char* headerformat = "GET %s HTTP/1.0\r\nHost: %s\r\nUser-Agent: WiiEarthh 1.0\r\n\r\n";;
    char header[strlen(headerformat) + strlen(domain) + strlen(path)];
    sprintf(header, headerformat, path, domain);

    //Do the request and get the response
    send_message(connection, header);
    struct block response = read_message(connection);
    net_close(connection);

    //Search for the 4-character sequence \r\n\r\n in the response which signals the start of the http payload (file)
    unsigned char *filestart = NULL;
    u32 filesize = 0;
    int i;
    for (i = 3; i < response.size; i++) {
        if (response.data[i] == '\n' &&
                response.data[i-1] == '\r' &&
                response.data[i-2] == '\n' &&
                response.data[i-3] == '\r') {
            filestart = response.data + i + 1;
            filesize = response.size - i - 1;
            break;
        }
    }

    if (filestart == NULL) {
        //printf("HTTP Response was without a file\n");
        free(response.data);
        return emptyblock;
    }

    //Copy the file part of the response into a new memoryblock to return
    struct block file;
    file.data = malloc(filesize);
    file.size = filesize;

    if (file.data == NULL) {
        //printf("No more memory to copy file from HTTP response\n");
        free(response.data);
        return emptyblock;
    }

    memcpy(file.data, filestart, filesize);

    //Dispose of the original response
    free(response.data);

    return file;
}

s32 GetConnection(char * domain) {

    u32 ipaddress = getipbynamecached(domain);
    if (ipaddress == 0) {
        return -1;
    }
    s32 connection = server_connect(ipaddress, 80);
    return connection;

}