Fix wrong makefile rule.

.gitignore

@@ -1,4 +1,5 @@
 zig-cache
 zig-out
+.zig-cache
 docs
 *.swp

README.md

@@ -24,5 +24,6 @@ See the [dedicated repository][examples].
 
 LibIPC reached a stable state and is usable.
 Performance is fine for most projects, but can be largely improved.
+The `poll` syscall is used instead of more recent and *faster* syscalls (`epoll`, `kqueue`, etc.).
 
 [examples]: https://git.baguette.netlib.re/Baguette/libipc-examples

TODO.md

@@ -9,7 +9,6 @@
 ### makefile
 
 - release
-- distribution
 
 ### documentation
 

build.zig

@@ -1,6 +1,6 @@
 const std = @import("std");
 
-const VERSION = "0.1.1";
+const VERSION = "0.2.0";
 
 // Although this function looks imperative, note that its job is to
 // declaratively construct a build graph that will be executed by an external
@@ -21,7 +21,7 @@ pub fn build(b: *std.Build) void {
         .name = "ipc",
         // In this case the main source file is merely a path, however, in more
         // complicated build scripts, this could be a generated file.
-        .root_source_file = .{ .path = "src/bindings.zig" },
+        .root_source_file = .{ .cwd_relative = "src/bindings.zig" },
         .target = target,
         .optimize = optimize,
     });
@@ -37,7 +37,7 @@ pub fn build(b: *std.Build) void {
 
     const shared_lib = b.addSharedLibrary(.{
         .name = "ipc",
-        .root_source_file = .{ .path = "src/bindings.zig" },
+        .root_source_file = .{ .cwd_relative = "src/bindings.zig" },
         .version = comptime (try std.SemanticVersion.parse(VERSION)),
         .target = target,
         .optimize = optimize,
@@ -47,7 +47,7 @@ pub fn build(b: *std.Build) void {
 
     // Creates a step for unit testing.
     const main_tests = b.addTest(.{
-        .root_source_file = .{ .path = "src/main.zig" },
+        .root_source_file = .{ .cwd_relative = "src/main.zig" },
         .target = target,
         .optimize = optimize,
     });

ipc.pc

@@ -3,6 +3,6 @@ libdir=/usr/local/lib
 
 Name: LibIPC
 Description: The simplest Inter Process Communication library
-Version: 0.1.1
+Version: 0.2.0
 Libs: -L${libdir} -lipc
 Cflags: -I${includedir}

libipc.h

@@ -3,47 +3,112 @@
 
 #include <stdint.h>
 
+/**
+  The LibIPC API is designed to be simple.
+
+  For most applications, the usage can be summarized as:
+
+  - ipc_context_init                         to allocate the "context" structure;
+  - ipc_service_init or ipc_connect_service  to instanciate the service or starts a connection to it;
+  - loop over ipc_wait_event                 to wait for events;
+  - ipc_schedule                             to send messages;
+  - ipc_close_all then ipc_context_deinit    to close all connections then free the context.
+
+  The ipc_wait_event function is where the magic happens.
+  This function handles all the complexity of network management, juggling with file descriptors,
+  storing connection-related data, waiting for an event, handling connections and disconnections,
+  reading incoming messages and providing UNDERSTANDABLE notifications (see the `event_types` enumeration).
+
+  Basic events are:
+
+  - Connections and disconnections, they are already handled within LibIPC, but the API notifies the
+    user so they can perform additional operations;
+  - Messages (received or sent);
+  - Timers, to wake up the application on a regular basis (setup with ipc_context_timer).
+
+  Furthermore, the API can be used for non-IPC communications, meaning connections not using the LibIPC protocol.
+  This is particularly useful when dealing with any file descriptor that needs attention.
+  The ipc_add_external function adds a file descriptor marked as "external" which will be listened on by LibIPC.
+  In this case, disconnections are still handled, but messages aren't automatically read.
+  This way, almost any protocol can be used along with LibIPC communications and with the LibIPC API.
+  Related event: EXTERNAL, notifying users that an "external" file descriptor received a message.
+
+  Finally, a "switch" mechanism to automatically transfer messages between a pair of file descriptors (ipc_add_switch).
+  Messages are automatically exchanged between the two file descriptors by LibIPC;
+  eventually with user-provided callbacks (ipc_set_switch_callbacks) for non-IPC connections.
+  Thus, callbacks enable to handle websocket connections, non-IPC clients communicating with JSON messages, etc.
+  Related events: SWITCH RX and TX, notifying users that a "switched" file descriptor received (or sent) a message.
+
+  Switch and IO callbacks enable to easily create "protocol IPC services" (such as TCPd) to
+  bind IPC services to basically any available protocol through small, dedicated services
+  handling all the nitty-gritty details of non-IPC protocols.
+ */
+
+// Event types: the "t" parameter in "ipc_wait_event".
 enum event_types {
-	  ERROR = 0         // A problem occured.
-	, CONNECTION = 1    // New user.
-	, DISCONNECTION = 2 // User disconnected.
-	, MESSAGE_RX = 3    // New message.
-	, MESSAGE_TX = 4    // Message sent.
-	, TIMER = 5         // Timeout in the poll(2) function.
-	, EXTERNAL = 6      // Message received from a non IPC socket.
-	, SWITCH_RX = 7     // Message received from a switched FD.
-	, SWITCH_TX = 8     // Message sent to a switched fd.
+	  ERROR         = 0  // A problem occured.
+	, CONNECTION    = 1  // New user.
+	, DISCONNECTION = 2  // User disconnected.
+	, MESSAGE_RX    = 3  // New message.
+	, MESSAGE_TX    = 4  // Message sent.
+	, TIMER         = 5  // Timeout in the poll(2) function.
+	, EXTERNAL      = 6  // Message received from a non-IPC socket.
+	, SWITCH_RX     = 7  // Message received from a switched fd.
+	, SWITCH_TX     = 8  // Message sent to a switched fd.
 };
 
 // Return type of callback functions when switching.
 enum cb_event_types {
-	  CB_NO_ERROR = 0      // No error. A message was generated.
-	, CB_ERROR = 1         // Generic error.
-	, CB_FD_CLOSING = 2    // The fd is closing.
-	, CB_IGNORE = 3        // The message should be ignored (protocol specific).
+	  CB_NO_ERROR   = 0  // No error. A message was generated.
+	, CB_ERROR      = 1  // Generic error.
+	, CB_FD_CLOSING = 2  // The fd is closing.
+	, CB_IGNORE     = 3  // The message should be ignored (protocol specific).
 };
 
-int ipc_context_init (void** ptr);
-int ipc_service_init (void* ctx, int* servicefd, const char* service_name, uint16_t service_name_len);
+int ipc_context_init    (void** ptr);  // Allocate memory for a context.
+void ipc_context_deinit (void** ctx);  // Free the context's memory.
+void ipc_context_timer  (void* ctx, int timer); // Change the timer (for timer events, in ms).
+
+// Init (or connect to) a service. That's almost the same operation behind the scene.
+int ipc_service_init    (void* ctx, int* servicefd, const char* service_name, uint16_t service_name_len);
 int ipc_connect_service (void* ctx, int* servicefd, const char* service_name, uint16_t service_name_len);
-void ipc_context_deinit (void** ctx);
-int ipc_write (void* ctx, int servicefd, char* mcontent, uint32_t mlen);
-int ipc_schedule (void* ctx, int servicefd, const char* mcontent, uint32_t mlen);
-int ipc_read_fd (void* ctx, int fd, char* buffer, size_t* buflen);
-int ipc_read (void* ctx, size_t index, char* buffer, size_t* buflen);
-int ipc_wait_event(void* ctx, char* t, size_t* index, int* originfd, char* buffer, size_t* buflen);
-void ipc_context_timer (void* ctx, int timer);
-int ipc_close_fd (void* ctx, int fd);
-int ipc_close (void* ctx, size_t index);
+
+// Write a message or schedule it.
+int ipc_write    (void* ctx, int servicefd, const char* mcontent, size_t mlen);
+int ipc_schedule (void* ctx, int servicefd, const char* mcontent, size_t mlen);
+
+// Read a message from a client; either selected by an index in the context structure or by its file descriptor.
+int ipc_read_fd (void* ctx,       int fd, char* buffer, size_t* buflen);
+int ipc_read    (void* ctx, size_t index, char* buffer, size_t* buflen);
+
+// Wait for an event.
+// The "t" parameter is the type of the event (enum event_types).
+// The "index" parameter is the index in the context structure of the origin of the event (client or server).
+// The "originfd" parameter is the file descriptor on which the event occurs.
+// The "newfd" parameter is the file descriptor of the new connected client, in case of a connection event.
+// The "buffer" and "buflen" parameters contain respectively a copy of the received message and its length.
+int ipc_wait_event (void* ctx, char* t, size_t* index, int* originfd, int* newfd, char* buffer, size_t* buflen);
+
+// Close a client (or server) based on its file descriptor or its index in the context structure.
+int ipc_close_fd  (void* ctx,       int fd);
+int ipc_close     (void* ctx, size_t index);
+// Close all connections (probably right before the processus is terminated).
 int ipc_close_all (void* ctx);
 
-// Switch functions (for "protocol" services, such as TCPd).
+// Add a (possibly non-IPC) file descriptor to handle.
+// Since it's not marked as an IPC connection, messages won't be automatically read;
+// which enables to handle any communications for most protocols through the LibIPC API.
 int ipc_add_external (void* ctx, int newfd);
+
+// Add a new switch between a pair of file descriptors, enabling automatic exchange of messages
+// between this pair of fds. Useful for "protocol services", such as TCPd.
 int ipc_add_switch (void* ctx, int fd1, int fd2);
 
+// Set IO callbacks for a file descriptor.
 // Returned "char" is a cb_event_types enum.
+// One of the callbacks can be "NULL" to keep the default callback, thus changing only input or output operations.
 int ipc_set_switch_callbacks (void* ctx, int fd
-  , char (*in (int orig, const char *payload, uint32_t *mlen))
-  , char (*out(int dest,       char *payload, uint32_t  mlen)));
+  , char (*in (int orig,       char *payload, size_t *mlen))
+  , char (*out(int dest, const char *payload, size_t  mlen)));
 
 #endif

makefile

@@ -15,25 +15,27 @@ PREFIX       ?= /usr/local
 LIBDIR       ?= $(PREFIX)/lib
 INCLUDEDIR   ?= $(PREFIX)/include
 PKGCONFIGDIR ?= /usr/share/pkgconfig
-install-pkgconfig:
-	[ -d $(PKGCONFIGDIR) ] || install -m 0755 -d $(PKGCONFIGDIR)
-	install -m 0644 ipc.pc $(PKGCONFIGDIR)
-install-library:
-	[ -d $(LIBDIR) ] || install -m 0755 -d $(LIBDIR)
-	install -m 0644 zig-out/lib/libipc.a $(LIBDIR)
-	install -m 0644 zig-out/lib/libipc.so $(LIBDIR)
-install-header:
-	[ -d $(INCLUDEDIR) ] || install -m 0755 -d $(INCLUDEDIR)
-	install -m 0644 libipc.h $(INCLUDEDIR)
-install: install-pkgconfig install-library install-header
 
-uninstall-library:
-	rm $(LIBDIR)/libipc.a \
-		$(LIBDIR)/libipc.so \
-		$(LIBDIR)/libipc.so.*
-uninstall-header:
-	rm $(INCLUDEDIR)/libipc.h
-uninstall: uninstall-library uninstall-header
+$(PKGCONFIGDIR):; install -m 0755 -d $(PKGCONFIGDIR)
+$(PKGCONFIGDIR)/ipc.pc: ipc.pc; install -m 0644 ipc.pc $(PKGCONFIGDIR)
+install-pkgconfig: $(PKGCONFIGDIR) $(PKGCONFIGDIR)/ipc.pc
+
+$(LIBDIR):; install -m 0755 -d $(LIBDIR)
+$(LIBDIR)/libipc.a:   zig-out/lib/libipc.a;	install -m 0644 zig-out/lib/libipc.a $(LIBDIR)
+$(LIBDIR)/libipc.so: zig-out/lib/libipc.so;	install -m 0644 zig-out/lib/libipc.so $(LIBDIR)
+install-library: $(LIBDIR) $(LIBDIR)/libipc.a $(LIBDIR)/libipc.so
+
+$(INCLUDEDIR):;	install -m 0755 -d $(INCLUDEDIR)
+$(INCLUDEDIR)/libipc.h: libipc.h;	install -m 0644 libipc.h $(INCLUDEDIR)
+install-header: $(INCLUDEDIR) $(INCLUDEDIR)/libipc.h
+
+install: install-pkgconfig install-library install-header
+	@echo "Now that you have installed the library, you should (probably) run ldconfig."
+
+uninstall-library:; rm $(LIBDIR)/libipc.a $(LIBDIR)/libipc.so*
+uninstall-header:; rm $(INCLUDEDIR)/libipc.h
+uninstall-pkgconfig:; rm $(PKGCONFIGDIR)/ipc.pc
+uninstall: uninstall-pkgconfig uninstall-library uninstall-header
 
 mrproper:
 	rm -r docs zig-cache zig-out 2>/dev/null || true
@@ -48,21 +50,21 @@ serve-doc:
 	darkhttpd docs/ --addr $(DOC_HTTPD_ADDR) --port $(DOC_HTTPD_PORT) --log $(DOC_HTTPD_ACCESS_LOGS)
 
 PACKAGE ?= libipc
-VERSION ?= 0.1.0
+VERSION ?= 0.2.0
 PKG = $(PACKAGE)-$(VERSION)
-dist-dir:
-	[ -d $(PKG) ] || ln -s . $(PKG)
 $(PKG).tar.gz: dist-dir
 	tar zcf $@ \
 		$(PKG)/src \
-		$(PKG)/build.zig \
+		$(PKG)/build.zig* \
 		$(PKG)/libipc.h \
+		$(PKG)/ipc.pc \
 		$(PKG)/makefile* \
 		$(PKG)/README* \
 		$(PKG)/TODO*
-dist-rm-dir:
-	rm $(PKG)
-dist-gz: $(PACKAGE)-$(VERSION).tar.gz
+$(PKG):; ln -s . $(PKG)
+dist-dir: $(PKG)
+dist-rm-dir:; rm $(PKG)
+dist-gz: $(PKG).tar.gz
 dist: dist-gz dist-rm-dir
 
 # You can add your specific instructions there.

src/bindings.zig

@@ -36,7 +36,7 @@ export fn ipc_context_deinit(ctx: **Context) callconv(.C) void {
 }
 
 /// Write a message (no waiting).
-export fn ipc_write(ctx: *Context, servicefd: i32, mcontent: [*]const u8, mlen: u32) callconv(.C) i32 {
+export fn ipc_write(ctx: *Context, servicefd: i32, mcontent: [*]const u8, mlen: usize) callconv(.C) i32 {
     // TODO: better default length.
     var buffer = [_]u8{0} ** 100000;
     var fba = std.heap.FixedBufferAllocator.init(&buffer);
@@ -48,7 +48,7 @@ export fn ipc_write(ctx: *Context, servicefd: i32, mcontent: [*]const u8, mlen:
 
 /// Schedule a message.
 /// Use the same allocator as the context.
-export fn ipc_schedule(ctx: *Context, servicefd: i32, mcontent: [*]const u8, mlen: u32) callconv(.C) i32 {
+export fn ipc_schedule(ctx: *Context, servicefd: i32, mcontent: [*]const u8, mlen: usize) callconv(.C) i32 {
     const message = Message.init(servicefd, ctx.allocator, mcontent[0..mlen]) catch return -1;
     ctx.schedule(message) catch return -2;
     return 0;
@@ -90,7 +90,7 @@ export fn ipc_read(ctx: *Context, index: usize, buffer: [*]u8, buflen: *usize) c
 
 /// Wait for an event.
 /// Buffer length will be changed to the size of the received message.
-export fn ipc_wait_event(ctx: *Context, t: *u8, index: *usize, originfd: *i32, buffer: [*]u8, buflen: *usize) callconv(.C) i32 {
+export fn ipc_wait_event(ctx: *Context, t: *u8, index: *usize, originfd: *i32, newfd: *i32, buffer: [*]u8, buflen: *usize) callconv(.C) i32 {
     const event = ctx.wait_event() catch |err| switch (err) {
         else => {
             log.warn("error while waiting for an event: {}\n", .{err});
@@ -100,13 +100,17 @@ export fn ipc_wait_event(ctx: *Context, t: *u8, index: *usize, originfd: *i32, b
     t.* = @intFromEnum(event.t);
     index.* = event.index;
     originfd.* = event.origin;
+    newfd.* = event.newfd;
 
     if (event.m) |m| {
         var fbs = std.io.fixedBufferStream(buffer[0..buflen.*]);
         var writer = fbs.writer();
         _ = writer.write(m.payload) catch return -4;
         buflen.* = m.payload.len;
-        m.deinit();
+        switch (event.t) {
+            .SWITCH_RX => {},
+            else => m.deinit(),
+        }
     } else {
         buflen.* = 0;
     }
@@ -148,8 +152,8 @@ export fn ipc_add_switch(ctx: *Context, fd1: i32, fd2: i32) callconv(.C) i32 {
 }
 
 export fn ipc_set_switch_callbacks(ctx: *Context, fd: i32,
-                                   in: *const fn (origin: i32, mcontent: [*]u8, mlen: *u32) callconv(.C) u8,
-                                   out: *const fn (origin: i32, mcontent: [*]const u8, mlen: u32) callconv(.C) u8) callconv(.C) i32 {
+        in:  ?*const fn (origin: i32, mcontent:       [*]u8, mlen: *usize) callconv(.C) u8,
+        out: ?*const fn (origin: i32, mcontent: [*]const u8, mlen:  usize) callconv(.C) u8) callconv(.C) i32 {
     ctx.set_switch_callbacks(fd, in, out) catch return -1;
     return 0;
 }

src/context.zig

@@ -1,17 +1,11 @@
 const std = @import("std");
 const testing = std.testing;
-// const DEBUG = @import("./hexdump.zig");
 const net = std.net;
 const os = std.os;
 const fmt = std.fmt;
 const c = std.c;
 const posix = std.posix;
 
-// const print = std.debug.print;
-
-// TODO: to remove once PR https://github.com/ziglang/zig/pull/14639 is accepted.
-pub extern "c" fn umask(mode: c.mode_t) c.mode_t;
-
 const log = std.log.scoped(.libipc_context);
 
 const receive_fd = @import("./exchange-fd.zig").receive_fd;
@@ -35,7 +29,6 @@ pub const PollFD = std.ArrayList(posix.pollfd);
 pub const IPC_HEADER_SIZE = 4; // Size (4 bytes) then content.
 pub const IPC_BASE_SIZE = 100000; // 100 KB, plenty enough space for messages
 pub const IPC_MAX_MESSAGE_SIZE = IPC_BASE_SIZE - IPC_HEADER_SIZE;
-pub const IPC_VERSION = 1;
 
 // Context of the whole networking state.
 pub const Context = struct {
@@ -66,8 +59,8 @@ pub const Context = struct {
         };
 
         // Allow mkdir to create a directory with 0o770 permissions.
-        const previous_mask = umask(0o007);
-        defer _ = umask(previous_mask);
+        const previous_mask = c.umask(0o007);
+        defer _ = c.umask(previous_mask);
 
         // Create the run directory, where all UNIX sockets will be.
         posix.mkdir(rundir, 0o0770) catch |err| switch (err) {
@@ -80,7 +73,12 @@ pub const Context = struct {
             },
         };
 
-        return Self{ .rundir = rundir, .connections = Connections.init(allocator), .pollfd = PollFD.init(allocator), .tx = Messages.init(allocator), .switchdb = SwitchDB.init(allocator), .allocator = allocator };
+        return Self{ .rundir = rundir
+                   , .connections = Connections.init(allocator)
+                   , .pollfd = PollFD.init(allocator)
+                   , .tx = Messages.init(allocator)
+                   , .switchdb = SwitchDB.init(allocator)
+                   , .allocator = allocator };
     }
 
     pub fn deinit(self: *Self) void {
@@ -218,6 +216,13 @@ pub const Context = struct {
         try self.add_(newcon, newfd);
     }
 
+    // /// Change the type of a file descriptor.
+    // /// Useful for protocol daemons (ex: TCPd) or proxies listening to local IPC connections for new clients.
+    // /// In this case, the client can be "switched" but needs to be marked as such.
+    // /// TODO
+    // pub fn change_fd_type (self: *Self, fd: i32, new_type: Connection.Type) !void {
+    // }
+
     fn accept_new_client(self: *Self, event: *Event, server_index: usize) !void {
         // net.Server
         const serverfd = self.pollfd.items[server_index].fd;
@@ -233,7 +238,7 @@ pub const Context = struct {
 
         const sfd = server.stream.handle;
         // WARNING: imply every new item is last
-        event.set(Event.Type.CONNECTION, self.pollfd.items.len - 1, sfd, null);
+        event.set(Event.Type.CONNECTION, self.pollfd.items.len - 1, sfd, newfd, null);
     }
 
     // Create a unix socket.
@@ -257,8 +262,8 @@ pub const Context = struct {
 
         // Allow to create a unix socket with the right permissions.
         // Group should include write permissions.
-        const previous_mask = umask(0o117);
-        defer _ = umask(previous_mask);
+        const previous_mask = c.umask(0o117);
+        defer _ = c.umask(previous_mask);
 
         // Remove the old UNIX socket.
         posix.unlink(path) catch |err| switch (err) {
@@ -290,12 +295,6 @@ pub const Context = struct {
         _ = try m.write(writer); // returns paylen
 
         _ = try stream.write(fbs.getWritten());
-
-        // var hexbuf: [2000]u8 = undefined;
-        // var hexfbs = std.io.fixedBufferStream(&hexbuf);
-        // var hexwriter = hexfbs.writer();
-        // try DEBUG.hexdump(hexwriter, "MSG SENT", fbs.getWritten());
-        // print("{s}\n", .{hexfbs.getWritten()});
     }
 
     pub fn schedule(self: *Self, m: Message) !void {
@@ -318,8 +317,8 @@ pub const Context = struct {
     }
 
     pub fn set_switch_callbacks(self: *Self, fd: i32,
-                                in: *const fn (origin: i32, mcontent: [*]u8, mlen: *u32) callconv(.C) u8,
-                                out: *const fn (origin: i32, mcontent: [*]const u8, mlen: u32) callconv(.C) u8) !void {
+            in:  ?*const fn (origin: i32, mcontent:       [*]u8, mlen: *usize) callconv(.C) u8,
+            out: ?*const fn (origin: i32, mcontent: [*]const u8, mlen:  usize) callconv(.C) u8) !void {
         try self.switchdb.set_callbacks(fd, in, out);
     }
 
@@ -365,7 +364,7 @@ pub const Context = struct {
 
     // Wait for an event.
     pub fn wait_event(self: *Self) !Event {
-        var current_event: Event = Event.init(Event.Type.ERROR, 0, 0, null);
+        var current_event: Event = Event.init(Event.Type.ERROR, 0, 0, 0, null);
         var wait_duration: i32 = -1; // -1 == unlimited
 
         if (self.timer) |t| {
@@ -399,17 +398,17 @@ pub const Context = struct {
 
         if (count < 0) {
             log.err("there is a problem: poll < 0", .{});
-            current_event = Event.init(Event.Type.ERROR, 0, 0, null);
+            current_event = Event.init(Event.Type.ERROR, 0, 0, 0, null);
             return current_event;
         }
 
         const duration = timer.read() / 1000000; // ns -> ms
         if (count == 0) {
             if (duration >= wait_duration) {
-                current_event = Event.init(Event.Type.TIMER, 0, 0, null);
+                current_event = Event.init(Event.Type.TIMER, 0, 0, 0, null);
             } else {
                 // In case nothing happened, and poll wasn't triggered by time out.
-                current_event = Event.init(Event.Type.ERROR, 0, 0, null);
+                current_event = Event.init(Event.Type.ERROR, 0, 0, 0, null);
             }
             return current_event;
         }
@@ -455,7 +454,7 @@ pub const Context = struct {
                 }
                 // EXTERNAL = user handles IO
                 else if (self.connections.items[i].t == .EXTERNAL) {
-                    return Event.init(Event.Type.EXTERNAL, i, current_fd, null);
+                    return Event.init(Event.Type.EXTERNAL, i, current_fd, 0, null);
                 }
                 // otherwise = new message or disconnection
                 else {
@@ -463,26 +462,26 @@ pub const Context = struct {
                         error.ConnectionResetByPeer => {
                             log.warn("connection reset by peer", .{});
                             try self.close(i);
-                            return Event.init(Event.Type.DISCONNECTION, i, current_fd, null);
+                            return Event.init(Event.Type.DISCONNECTION, i, current_fd, 0, null);
                         },
                         error.wrongMessageLength => {
                             log.warn("wrong message length, terminating the connection", .{});
                             try self.close(i);
-                            return Event.init(Event.Type.DISCONNECTION, i, current_fd, null);
+                            return Event.init(Event.Type.DISCONNECTION, i, current_fd, 0, null);
                         },
                         else => {
                             log.warn("unmanaged error while reading a message ({})", .{err});
                             try self.close(i);
-                            return Event.init(Event.Type.ERROR, i, current_fd, null);
+                            return Event.init(Event.Type.ERROR, i, current_fd, 0, null);
                         },
                     };
 
                     if (maybe_message) |m| {
-                        return Event.init(Event.Type.MESSAGE_RX, i, current_fd, m);
+                        return Event.init(Event.Type.MESSAGE_RX, i, current_fd, 0, m);
                     }
 
                     try self.close(i);
-                    return Event.init(Event.Type.DISCONNECTION, i, current_fd, null);
+                    return Event.init(Event.Type.DISCONNECTION, i, current_fd, 0, null);
                 }
             }
 
@@ -526,21 +525,21 @@ pub const Context = struct {
                         error.BrokenPipe => {
                             log.warn("cannot send message, dest probably closed the connection ({})", .{err});
                             try self.close(i);
-                            return Event.init(Event.Type.DISCONNECTION, i, current_fd, null);
+                            return Event.init(Event.Type.DISCONNECTION, i, current_fd, 0, null);
                         },
                         else => {
                             log.warn("unmanaged error while sending a message ({})", .{err});
                             try self.close(i);
-                            return Event.init(Event.Type.ERROR, i, current_fd, null);
+                            return Event.init(Event.Type.ERROR, i, current_fd, 0, null);
                         },
                     };
-                    return Event.init(Event.Type.MESSAGE_TX, i, current_fd, null);
+                    return Event.init(Event.Type.MESSAGE_TX, i, current_fd, 0, null);
                 }
             }
             // .revent is POLLHUP
             if (fd.revents & std.os.linux.POLL.HUP > 0) {
                 // handle disconnection
-                current_event = Event.init(Event.Type.DISCONNECTION, i, current_fd, null);
+                current_event = Event.init(Event.Type.DISCONNECTION, i, current_fd, 0, null);
                 try self.close(i);
                 return current_event;
             }
@@ -548,7 +547,7 @@ pub const Context = struct {
             if ((fd.revents & std.os.linux.POLL.HUP > 0) or
                 (fd.revents & std.os.linux.POLL.NVAL > 0))
             {
-                return Event.init(Event.Type.ERROR, i, current_fd, null);
+                return Event.init(Event.Type.ERROR, i, current_fd, 0, null);
             }
         }
 

src/event.zig

@@ -48,23 +48,26 @@ pub const Event = struct {
     t: Event.Type,
     index: usize,
     origin: i32, // socket fd
+    newfd: i32,  // on new connection, tell the new client's socket fd
     m: ?Message, // message
 
     const Self = @This();
 
-    pub fn init(t: Event.Type, index: usize, origin: i32, m: ?Message) Self {
+    pub fn init(t: Event.Type, index: usize, origin: i32, newfd: i32, m: ?Message) Self {
         return Self{
             .t = t,
             .index = index,
             .origin = origin,
+            .newfd = newfd,
             .m = m,
         };
     }
 
-    pub fn set(self: *Self, t: Event.Type, index: usize, origin: i32, m: ?Message) void {
+    pub fn set(self: *Self, t: Event.Type, index: usize, origin: i32, newfd: i32, m: ?Message) void {
         self.t = t;
         self.index = index;
         self.origin = origin;
+        self.newfd = newfd;
         self.m = m;
     }
 
@@ -72,6 +75,7 @@ pub const Event = struct {
         self.t = Event.Type.ERROR;
         self.index = @as(usize, 0);
         self.origin = @as(i32, 0);
+        self.newfd = @as(i32, 0);
         if (self.m) |message| {
             message.deinit();
         }
@@ -79,7 +83,7 @@ pub const Event = struct {
     }
 
     pub fn format(self: Self, comptime _: []const u8, _: fmt.FormatOptions, out_stream: anytype) !void {
-        try fmt.format(out_stream, "{}, origin: {}, index {}, message: [{?}]", .{ self.t, self.origin, self.index, self.m });
+        try fmt.format(out_stream, "{}, origin: {}, newfd: {}, index {}, message: [{?}]", .{ self.t, self.origin, self.newfd, self.index, self.m });
     }
 };
 
@@ -92,7 +96,7 @@ test "Event - creation and display" {
     const s = "hello!!";
     var m = try Message.init(1, allocator, s); // fd type payload
     defer m.deinit();
-    const e = Event.init(Event.Type.CONNECTION, 5, 8, m); // type index origin message
+    const e = Event.init(Event.Type.CONNECTION, 5, 8, 4, m); // type index origin message
 
-    try print_eq("event.Event.Type.CONNECTION, origin: 8, index 5, message: [fd: 1, payload: [hello!!]]", e);
+    try print_eq("event.Event.Type.CONNECTION, origin: 8, newfd: 4, index 5, message: [fd: 1, payload: [hello!!]]", e);
 }

src/exchange-fd.zig

@@ -78,8 +78,8 @@ test {
 pub fn send_fd(sockfd: posix.socket_t, msg: []const u8, fd: posix.fd_t) void {
     var iov = [_]posix.iovec_const{
         .{
-            .iov_base = msg.ptr,
-            .iov_len = msg.len,
+            .base = msg.ptr,
+            .len = msg.len,
         },
     };
 
@@ -191,7 +191,7 @@ pub fn receive_fd(sockfd: posix.socket_t, buffer: []u8, msg_size: *usize) !posix
     var msg_buffer = [_]u8{0} ** 1500;
 
     var iov = [_]posix.iovec{
-        .{ .iov_base = msg_buffer[0..], .iov_len = msg_buffer.len },
+        .{ .base = msg_buffer[0..], .len = msg_buffer.len },
     };
 
     var cmsg = Cmsghdr(posix.fd_t).init(.{

src/hexdump.zig

@@ -1,13 +1,13 @@
 const std = @import("std");
 
-pub fn hexdump(stream: anytype, header: []const u8, buffer: []const u8) std.os.WriteError!void {
+pub fn hexdump(stream: anytype, header: []const u8, buffer: []const u8) std.posix.WriteError!void {
     // Print a header.
     if (header.len > 0) {
         var hdr: [64]u8 = undefined;
         const offset: usize = (hdr.len / 2) - ((header.len / 2) - 1);
 
         @memset(hdr[0..hdr.len], ' ');
-        std.mem.copy(u8, hdr[offset..hdr.len], header);
+        std.mem.copyForwards(u8, hdr[offset..hdr.len], header);
 
         try stream.writeAll(hdr[0..hdr.len]);
         try stream.writeAll("\n");
@@ -72,6 +72,17 @@ pub fn hexdump(stream: anytype, header: []const u8, buffer: []const u8) std.os.W
     try stream.writeAll("\n");
 }
 
+/// Debug function: print some bytes' hexdump on standard output.
+pub fn print_hex(title: []const u8, buffer : []const u8) !void
+{
+    const stdout = std.io.getStdOut().writer();
+    var hexbuf: [100_000]u8 = undefined;
+    var hexfbs = std.io.fixedBufferStream(&hexbuf);
+    const hexwriter = hexfbs.writer();
+    try hexdump(hexwriter, title, buffer);
+    try stdout.print("{s}\n", .{hexfbs.getWritten()});
+}
+
 const print = std.debug.print;
 
 test "36-byte hexdump test" {

src/message.zig

@@ -5,6 +5,7 @@ const fmt = std.fmt;
 
 const print_eq = @import("./util.zig").print_eq;
 
+const payload_header_length = 4;
 pub const Messages = std.ArrayList(Message);
 
 pub const Message = struct {
@@ -28,17 +29,17 @@ pub const Message = struct {
         var reader = fbs.reader();
 
         const msg_len = try reader.readInt(u32, .big);
-        if (msg_len > buffer.len - 4) {
+        if (msg_len > buffer.len - payload_header_length) {
             return error.wrongMessageLength;
         }
-        const msg_payload = buffer[4 .. 4 + msg_len];
+        const msg_payload = buffer[payload_header_length .. payload_header_length + msg_len];
 
         return try Message.init(fd, allocator, msg_payload);
     }
 
     pub fn write(self: Self, writer: anytype) !usize {
         try writer.writeInt(u32, @as(u32, @truncate(self.payload.len)), .big);
-        return 4 + try writer.write(self.payload);
+        return payload_header_length + try writer.write(self.payload);
     }
 
     pub fn format(self: Self, comptime _: []const u8, _: fmt.FormatOptions, out_stream: anytype) !void {

src/switch.zig

@@ -40,10 +40,12 @@ pub const SwitchDB = struct {
     const Self = @This();
 
     db: std.AutoArrayHashMap(i32, ManagedConnection),
+    allocator: std.mem.Allocator,
 
     pub fn init(allocator: Allocator) Self {
         return Self{
             .db = std.AutoArrayHashMap(i32, ManagedConnection).init(allocator),
+            .allocator = allocator,
         };
     }
 
@@ -63,11 +65,12 @@ pub const SwitchDB = struct {
     }
 
     pub fn set_callbacks(self: *Self, fd: i32,
-                         in: *const fn (origin: i32, mcontent: [*]u8, mlen: *u32) callconv(.C) u8,
-                         out: *const fn (origin: i32, mcontent: [*]const u8, mlen: u32) callconv(.C) u8) !void {
+            in:  ?*const fn (origin: i32, mcontent:       [*]u8, mlen: *usize) callconv(.C) u8,
+            out: ?*const fn (origin: i32, mcontent: [*]const u8, mlen:  usize) callconv(.C) u8) !void {
         var managedconnection = self.db.get(fd) orelse return error.unregisteredFD;
-        managedconnection.in = in;
-        managedconnection.out = out;
+        if (in)  |f| { managedconnection.in  = f; }
+        if (out) |f| { managedconnection.out = f; }
+        try self.db.put(fd, managedconnection);
     }
 
     /// Dig the "db" hashmap, perform "in" fn, may provide a message.
@@ -77,7 +80,7 @@ pub const SwitchDB = struct {
         var managedconnection = self.db.get(fd) orelse return error.unregisteredFD;
 
         var buffer = [_]u8{0} ** 100000; // TODO: buffer size
-        var message_size: u32 = @truncate(buffer.len);
+        var message_size: usize = buffer.len;
         const r: CBEventType = @enumFromInt(managedconnection.in(fd, &buffer, &message_size));
 
         switch (r) {
@@ -87,9 +90,10 @@ pub const SwitchDB = struct {
             },
             CBEventType.NO_ERROR => {
                 // TODO: read message
-                // TODO: better allocator?
                 // TODO: better errors?
-                const message: Message = Message.read(managedconnection.dest, buffer[0..message_size], std.heap.c_allocator) catch {
+                const message: Message = Message.read(managedconnection.dest
+                                                     , buffer[0..message_size]
+                                                     , self.allocator) catch {
                     return error.generic;
                 };
                 return message;
@@ -120,7 +124,7 @@ pub const SwitchDB = struct {
         _ = message.write(writer) catch return error.generic;
         const written = fbs.getWritten();
 
-        const r: CBEventType = @enumFromInt(managedconnection.out(message.fd, written.ptr, @truncate(written.len)));
+        const r: CBEventType = @enumFromInt(managedconnection.out(message.fd, written.ptr, written.len));
 
         switch (r) {
             // The message should be ignored (protocol specific).
@@ -145,26 +149,26 @@ pub const SwitchDB = struct {
         var message: ?Message = null;
         message = self.read(fd) catch |err| switch (err) {
             error.closeFD => {
-                return Event.init(Event.Type.DISCONNECTION, index, fd, null);
+                return Event.init(Event.Type.DISCONNECTION, index, fd, 0, null);
             },
             error.unregisteredFD, error.generic => {
-                return Event.init(Event.Type.ERROR, index, fd, null);
+                return Event.init(Event.Type.ERROR, index, fd, 0, null);
             },
         };
-        return Event.init(Event.Type.SWITCH_RX, index, fd, message);
+        return Event.init(Event.Type.SWITCH_RX, index, fd, 0, message);
     }
 
     pub fn handle_event_write(self: *Self, index: usize, message: Message) Event {
         const fd = message.fd;
         self.write(message) catch |err| switch (err) {
             error.closeFD => {
-                return Event.init(Event.Type.DISCONNECTION, index, fd, null);
+                return Event.init(Event.Type.DISCONNECTION, index, fd, 0, null);
             },
             error.unregisteredFD, error.generic => {
-                return Event.init(Event.Type.ERROR, index, fd, null);
+                return Event.init(Event.Type.ERROR, index, fd, 0, null);
             },
         };
-        return Event.init(Event.Type.SWITCH_TX, index, fd, null);
+        return Event.init(Event.Type.SWITCH_TX, index, fd, 0, null);
     }
 
     /// Simple wrapper around self.db.get.
@@ -182,8 +186,8 @@ pub const SwitchDB = struct {
 
 const ManagedConnection = struct {
     dest: i32,
-    in: *const fn (origin: i32, mcontent: [*]u8, mlen: *u32) callconv(.C) u8 = default_in,
-    out: *const fn (origin: i32, mcontent: [*]const u8, mlen: u32) callconv(.C) u8 = default_out,
+    in:  *const fn (origin: i32, mcontent:       [*]u8, mlen: *usize) callconv(.C) u8 = default_in,
+    out: *const fn (origin: i32, mcontent: [*]const u8, mlen:  usize) callconv(.C) u8 = default_out,
 };
 
 test "creation and display" {
@@ -201,18 +205,18 @@ test "creation and display" {
     try print_eq("{ (5,6)(6,5) }", .{switchdb});
 }
 
-fn successful_in(_: i32, mcontent: [*]u8, mlen: *u32) CBEventType {
+fn successful_in(_: i32, mcontent: [*]u8, mlen: *usize) CBEventType {
     var m = Message.init(8, std.heap.c_allocator, "coucou") catch unreachable;
     defer m.deinit();
 
     var fbs = std.io.fixedBufferStream(mcontent[0..mlen.*]);
     const writer = fbs.writer();
     const bytes_written = m.write(writer) catch unreachable;
-    mlen.* = @truncate(bytes_written);
+    mlen.* = bytes_written;
     return CBEventType.NO_ERROR;
 }
 
-fn successful_out(_: i32, _: [*]const u8, _: u32) CBEventType {
+fn successful_out(_: i32, _: [*]const u8, _: usize) CBEventType {
     return CBEventType.NO_ERROR;
 }
 
@@ -251,11 +255,11 @@ test "successful exchanges" {
     }
 }
 
-fn unsuccessful_in(_: i32, _: [*]const u8, _: *u32) CBEventType {
+fn unsuccessful_in(_: i32, _: [*]const u8, _: *usize) CBEventType {
     return CBEventType.ERROR;
 }
 
-fn unsuccessful_out(_: i32, _: [*]const u8, _: u32) CBEventType {
+fn unsuccessful_out(_: i32, _: [*]const u8, _: usize) CBEventType {
     return CBEventType.ERROR;
 }
 
@@ -307,7 +311,7 @@ test "nuke 'em" {
     try testing.expect(switchdb.db.count() == 0);
 }
 
-fn default_in(origin: i32, mcontent: [*]u8, mlen: *u32) callconv(.C) u8 {
+fn default_in(origin: i32, mcontent: [*]u8, mlen: *usize) callconv(.C) u8 {
     // This may be kinda hacky, idk.
     var stream: net.Stream = .{ .handle = origin };
     const packet_size: usize = stream.read(mcontent[0..mlen.*]) catch return @intFromEnum(CBEventType.ERROR);
@@ -318,12 +322,12 @@ fn default_in(origin: i32, mcontent: [*]u8, mlen: *u32) callconv(.C) u8 {
         return @intFromEnum(CBEventType.FD_CLOSING);
     }
 
-    mlen.* = @truncate(packet_size);
+    mlen.* = packet_size;
 
     return @intFromEnum(CBEventType.NO_ERROR);
 }
 
-fn default_out(fd: i32, mcontent: [*]const u8, mlen: u32) callconv(.C) u8 {
+fn default_out(fd: i32, mcontent: [*]const u8, mlen: usize) callconv(.C) u8 {
     // Message contains the fd, no need to search for the right structure to copy,
     // let's just recreate a Stream from the fd.