minecraft-pi-reborn/media-layer/proxy/src/server/server.cpp

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#include <cerrno>
#include <cstring>
#include <unistd.h>
#include <pthread.h>
#include <csignal>
#include <sys/wait.h>
#include <fcntl.h>
#include <string>
#include <unordered_map>
#include <fstream>
#include "../common/common.h"
// Track Client State
static int _client_is_alive = 0;
static int _client_status = 0;
static void update_client_state(int is_alive, int status) {
_client_is_alive = is_alive;
_client_status = status;
}
// Check State Of Proxy And Exit If Invalid
void _check_proxy_state() {
// Check Client State
if (!_client_is_alive) {
if (WIFEXITED(_client_status)) {
PROXY_ERR("Client Terminated: Exit Code: %i", WEXITSTATUS(_client_status));
} else if (WIFSIGNALED(_client_status)) {
PROXY_ERR("Client Terminated: Signal: %i%s", WTERMSIG(_client_status), WCOREDUMP(_client_status) ? " (Core Dumped)" : "");
} else {
PROXY_ERR("%s", "Client Terminated");
}
}
}
// Start Proxy Client
static pid_t _client_pid;
static void sigchld_handler(__attribute__((unused)) int sig) {
// Track
int status;
// Reap
int saved_errno = errno;
// Only waitpid() Proxy Client, Other Sub-Processes Are Handled By pclose()
if (waitpid(_client_pid, &status, WNOHANG) == _client_pid) {
// Handle Client Death
update_client_state(0, status);
}
errno = saved_errno;
}
static void start_media_layer_proxy_client(int read, int write) {
// Reap Children
struct sigaction sa;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_NOCLDSTOP;
sa.sa_handler = &sigchld_handler;
if (sigaction(SIGCHLD, &sa, NULL) == -1) {
PROXY_ERR("Unable To Install Signal Handler: %s", strerror(errno));
}
// Fork And Start
pid_t ret = fork();
if (ret == -1) {
PROXY_ERR("Unable To Launch Client: %s", strerror(errno));
} else if (ret == 0) {
// Child Process
// Prepare Environment
RESET_ENVIRONMENTAL_VARIABLE("LD_LIBRARY_PATH");
RESET_ENVIRONMENTAL_VARIABLE("LD_PRELOAD");
// Prepare Arguments
char *read_str = NULL;
safe_asprintf(&read_str, "%i", read);
char *write_str = NULL;
safe_asprintf(&write_str, "%i", write);
char *argv[] = {NULL /* Updated By safe_execvpe() */, read_str, write_str, NULL};
// Run
safe_execvpe_relative_to_binary("lib/media-layer-proxy-client", argv, environ);
} else {
// Parent Process
_client_pid = ret;
}
update_client_state(1, 0);
}
// Maximize Pipe Buffer Size
static void maximize_pipe_fd_size(int fd) {
// Read Maximum Pipe Size
std::ifstream max_size_file("/proc/sys/fs/pipe-max-size");
if (!max_size_file.good()) {
PROXY_ERR("%s", "Unable To Open Maximum Pipe Size File");
}
// Read One Line
int max_size;
std::string line;
if (std::getline(max_size_file, line) && line.size() > 0) {
max_size = std::stoi(line);
} else {
PROXY_ERR("%s", "Unable To Read Maximum Pipe Size File");
}
// Set Maximum Pipe Size
errno = 0;
if (fcntl(fd, F_SETPIPE_SZ, max_size) < max_size) {
PROXY_ERR("Unable To Set Maximum Pipe Size: %s", errno != 0 ? strerror(errno) : "Unknown Error");
}
}
static void maximize_pipe_size(int pipe[2]) {
maximize_pipe_fd_size(pipe[0]);
maximize_pipe_fd_size(pipe[1]);
}
// Start Server
__attribute__((constructor)) static void init_media_layer_proxy_server() {
PROXY_INFO("%s", "Starting...");
// Create Connection
int server_to_client_pipe[2];
safe_pipe2(server_to_client_pipe, 0);
maximize_pipe_size(server_to_client_pipe);
int client_to_server_pipe[2];
safe_pipe2(client_to_server_pipe, 0);
maximize_pipe_size(client_to_server_pipe);
// Set Connection
set_connection(client_to_server_pipe[0], server_to_client_pipe[1]);
// Start Client
start_media_layer_proxy_client(server_to_client_pipe[0], client_to_server_pipe[1]);
// Wait For Connection Message
char *str = read_string();
if (strcmp(str, CONNECTED_MSG) == 0) {
PROXY_INFO("%s", "Connected");
} else {
PROXY_ERR("%s", "Unable To Connect");
}
// Free
free(str);
}
// Assign Unique ID To Function
static std::unordered_map<std::string, unsigned char> &get_unique_ids() {
static std::unordered_map<std::string, unsigned char> unique_ids;
return unique_ids;
}
void _assign_unique_id(const char *name, unsigned char id) {
get_unique_ids()[name] = id;
}
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unsigned char _get_unique_id(const char *name) {
return get_unique_ids()[name]; // Assume ID Exists
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}
// The Proxy Is Single-Threaded
static pthread_mutex_t proxy_mutex = PTHREAD_MUTEX_INITIALIZER;
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void _start_proxy_call(unsigned char call_id) {
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// Lock Proxy
pthread_mutex_lock(&proxy_mutex);
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write_byte(call_id);
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}
void end_proxy_call() {
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// Flush Write Cache
flush_write_cache();
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// Release Proxy
pthread_mutex_unlock(&proxy_mutex);
}