From ed2b3a38ec05c566c645dc2aabfd513edff8d63b Mon Sep 17 00:00:00 2001
From: tomsmeding <tom.smeding@gmail.com>
Date: Sun, 25 Dec 2016 22:55:21 +0100
Subject: Plugins

---
 .gitignore                  |  1 +
 Makefile                    |  8 ++++-
 main.c                      | 76 +++++++++++++++++++++++++++++++++++++++------
 plugin.h                    | 18 +++++++++++
 plugins/Makefile            | 39 +++++++++++++++++++++++
 plugins/echoback/echoback.c | 25 +++++++++++++++
 util.c                      |  4 +--
 util.h                      |  4 +--
 8 files changed, 160 insertions(+), 15 deletions(-)
 create mode 100644 plugin.h
 create mode 100644 plugins/Makefile
 create mode 100644 plugins/echoback/echoback.c

diff --git a/.gitignore b/.gitignore
index 7304726..ffa1d4b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 cserver
 *.o
 *.dSYM
+*.dylib
diff --git a/Makefile b/Makefile
index 1583287..078b0a0 100644
--- a/Makefile
+++ b/Makefile
@@ -7,12 +7,18 @@ else
 endif
 BIN = cserver
 
+PLUGINDIR = plugins
+
+PLUGINS = $(patsubst $(PLUGINDIR)/%,%,$(shell find $(PLUGINDIR)/ -maxdepth 1 -type d))
+
 .PHONY: all clean remake
 
 all: $(BIN)
+	for pl in $(PLUGINS); do make -C $(PLUGINDIR) $@ PLUGINNAME=$$pl; done
 
 clean:
 	rm -rf $(BIN) *.o *.dSYM
+	for pl in $(PLUGINS); do make -C $(PLUGINDIR) $@ PLUGINNAME=$$pl; done
 
 remake: clean all
 
@@ -20,5 +26,5 @@ remake: clean all
 $(BIN): $(patsubst %.c,%.o,$(wildcard *.c))
 	$(CC) -o $@ $^
 
-%.o: %.cpp $(wildcard *.h)
+%.o: %.c $(wildcard $(dir %.o)*.h)
 	$(CC) $(CFLAGS) -c -o $@ $<
diff --git a/main.c b/main.c
index 60b9584..52d10bd 100644
--- a/main.c
+++ b/main.c
@@ -7,9 +7,11 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <unistd.h>
+#include <dlfcn.h>
 #include <errno.h>
 #include "http.h"
 #include "memory.h"
+#include "plugin.h"
 #include "util.h"
 
 
@@ -37,27 +39,81 @@ static void signal_handler(int sig){
 }
 
 
+typedef struct Plugin{
+	char *name;
+	Handler handler;
+	struct Plugin *next;
+} Plugin;
+
+Plugin *pluginlist=NULL,*pluginlist_last=NULL;
+
+static void plugin_register_callback(const char *name,Handler handler){
+	if(pluginlist==NULL){
+		pluginlist=pluginlist_last=malloc(1,Plugin);
+		pluginlist->name=copy_str(name);
+		pluginlist->handler=handler;
+		pluginlist->next=NULL;
+	} else {
+		Plugin *newplugin=malloc(1,Plugin);
+		newplugin->name=copy_str(name);
+		newplugin->handler=handler;
+		newplugin->next=NULL;
+		pluginlist_last->next=newplugin;
+		pluginlist_last=newplugin;
+	}
+	printf("Registered plugin '%s' (handler %p)\n",name,handler);
+}
+
+typedef void (*register_function)(register_callback_t callback);
+
+static void load_plugin(const char *name){
+	void *lib=dlopen(name,RTLD_NOW|RTLD_LOCAL);
+	if(lib==NULL){
+		fprintf(stderr,"dlopen(%s): %s\n",name,dlerror());
+		exit(1);
+	}
+	register_function regfunc=(register_function)dlsym(lib,"plugin_register_yourself");
+	if(regfunc==NULL){
+		fprintf(stderr,"Cannot find plugin_register_yourself symbol in library '%s'\n",name);
+		exit(1);
+	}
+	regfunc(&plugin_register_callback);
+}
+
+
 static void connection_handler(int sock){
 	Headers *headers=http_get_headers(sock);
 	if(headers==NULL){
 		return;
 	}
 
-	sendall(sock,"HTTP/1.1 200 OK\r\n"
-	             "Content-Type: text/plain; charset=UTF-8\r\n"
-	             "Server: cserver\r\n"
-	             "\r\n",-1);
+	for(Plugin *pl=pluginlist;pl!=NULL;pl=pl->next){
+		switch(pl->handler(sock,headers)){
+			case HR_HANDLED:
+				printf("Request handled by %s\n",pl->name);
+				break;
+
+			case HR_NEXT:
+				continue;
 
-	sendallf(sock,"Method: %s\n",headers->method);
-	sendallf(sock,"URL: %s\n",headers->url);
-	sendallf(sock,"Version: %s\n",headers->version);
-	for(int i=0;i<headers->nheaders;i++){
-		sendallf(sock,"Header '%s': '%s'\n",headers->headers[i][0],headers->headers[i][1]);
+			case HR_ERROR:
+				printf("Request handler '%s' threw error\n",pl->name);
+				break;
+		}
+		break;
 	}
 }
 
 
-int main(void){
+int main(int argc,char **argv){
+	if(argc==1){
+		printf("Loading no plugin files\n");
+	} else {
+		for(int i=1;i<argc;i++){
+			load_plugin(argv[i]);
+		}
+	}
+
 	int sock=socket(PF_INET,SOCK_STREAM,0);
 	if(sock<0){
 		perror("socket");
diff --git a/plugin.h b/plugin.h
new file mode 100644
index 0000000..d3e8b36
--- /dev/null
+++ b/plugin.h
@@ -0,0 +1,18 @@
+#pragma once
+
+#include "http.h"
+
+
+typedef enum Handler_ret_t{
+	HR_HANDLED,
+	HR_NEXT,
+	HR_ERROR,
+} Handler_ret_t;
+
+typedef Handler_ret_t (*Handler)(int sock,Headers *headers);
+
+typedef void (*register_callback_t)(const char *name,Handler handler);
+
+// Override this in the plugin; it will be called from the main application.
+// It should call the callback with the plugin's handler.
+void plugin_register_yourself(register_callback_t callback);
diff --git a/plugins/Makefile b/plugins/Makefile
new file mode 100644
index 0000000..145500c
--- /dev/null
+++ b/plugins/Makefile
@@ -0,0 +1,39 @@
+CC = gcc
+CFLAGS = -Wall -Wextra -std=c11 -fwrapv -I..
+ifneq ($(DEBUG),)
+	CFLAGS += -g
+else
+	CFLAGS += -O2
+endif
+
+ifeq ($(shell uname),Darwin)
+	SO_EXT = dylib
+	SO_FLAGS = -dynamiclib
+else
+	SO_EXT = so
+	SO_FLAGS = -shared
+endif
+SO_FLAGS += -fPIC
+
+TARGET = $(PLUGINNAME)/$(PLUGINNAME).$(SO_EXT)
+
+
+.PHONY: all clean remake warning
+
+all: warning $(TARGET)
+
+clean:
+	rm -rf $(TARGET) $(PLUGINNAME)/*.{o,dSYM}
+
+remake: clean all
+
+warning:
+ifndef PLUGINNAME
+	$(error "PLUGINNAME not set! Please run root Makefile instead.")
+endif
+
+
+.SECONDARY:
+
+$(PLUGINNAME)/%.$(SO_EXT): $(patsubst %.c,%.o,$(wildcard $(PLUGINNAME)/*.c)) $(wildcard ../*.o ../*.h)
+	$(CC) $(SO_FLAGS) -o $@ $(filter %.o,$^)
diff --git a/plugins/echoback/echoback.c b/plugins/echoback/echoback.c
new file mode 100644
index 0000000..af94cbf
--- /dev/null
+++ b/plugins/echoback/echoback.c
@@ -0,0 +1,25 @@
+#include <stdio.h>
+#include "plugin.h"
+#include "util.h"
+
+
+static Handler_ret_t connection_handler(int sock,Headers *headers){
+	sendall(sock,"HTTP/1.1 200 OK\r\n"
+	             "Content-Type: text/plain; charset=UTF-8\r\n"
+	             "Server: cserver\r\n"
+	             "\r\n",-1);
+
+	sendallf(sock,"Method: %s\n",headers->method);
+	sendallf(sock,"URL: %s\n",headers->url);
+	sendallf(sock,"Version: %s\n",headers->version);
+	sendall(sock,"\n",1);
+	for(int i=0;i<headers->nheaders;i++){
+		sendallf(sock,"Header '%s': '%s'\n",headers->headers[i][0],headers->headers[i][1]);
+	}
+
+	return HR_HANDLED;
+}
+
+void plugin_register_yourself(register_callback_t callback){
+	callback("echoback",&connection_handler);
+}
diff --git a/util.c b/util.c
index 9d9c5d3..5116347 100644
--- a/util.c
+++ b/util.c
@@ -10,14 +10,14 @@
 #include "util.h"
 
 
-char* copy_buf(char *buf,int len){
+char* copy_buf(const char *buf,int len){
 	char *dst=malloc(len+1,char);
 	memcpy(dst,buf,len);
 	dst[len]='\0';
 	return dst;
 }
 
-char* copy_str(char *str){
+char* copy_str(const char *str){
 	return copy_buf(str,strlen(str));
 }
 
diff --git a/util.h b/util.h
index 5831b95..1124982 100644
--- a/util.h
+++ b/util.h
@@ -1,8 +1,8 @@
 #pragma once
 
 
-char* copy_buf(char *buf,int len);
-char* copy_str(char *str);
+char* copy_buf(const char *buf,int len);
+char* copy_str(const char *str);
 
 void str_toupper(char *str);
 
-- 
cgit v1.2.3-54-g00ecf