luajit imsg

imsg.lua

local ffi = require("ffi")
local unix = require("unix")

ffi.cdef [[
typedef uint32_t pid_t;

struct msgbuf;

struct imsgbuf {
	struct msgbuf		*w;
	pid_t			 pid;
	uint32_t		 maxsize;
	int			 fd;
	int			 flags;
};

struct imsg_hdr {
	uint32_t	 type;
	uint32_t	 len;
	uint32_t	 peerid;
	uint32_t	 pid;
};

struct imsg {
	struct imsg_hdr	 hdr;
	void		*data;
	struct ibuf	*buf;
};

int imsgbuf_init(struct imsgbuf*, int);
int imsgbuf_read(struct imsgbuf*);
int imsgbuf_write(struct imsgbuf*);
int imsg_compose(struct imsgbuf*, uint32_t type, uint32_t id, pid_t pid, int fd, const void *data, size_t datalen);

void imsg_free(struct imsg*);
ssize_t imsg_get(struct imsgbuf*, struct imsg *img);
int imsg_get_data(struct imsg*, void*, size_t);
int imsg_get_type(struct imsg*);
size_t imsg_get_len(struct imsg*);
]]

local libutil = ffi.load("util")

local sizettype = ffi.typeof("size_t");
local charptype = ffi.typeof("char*")
local imsgbuftype = ffi.typeof("struct imsgbuf")
local imsgtype = ffi.typeof("struct imsg")

local t = {}

local imsgbufmeta = {}

imsgbufmeta.write = function(self)
	local rv = libutil.imsgbuf_write(self.buf)
	if rv ~= 0 then
		error(unix.strerror(ffi.errno()))
	end
end

imsgbufmeta.compose = function(self, type, id, pid, fd, data)
	local rv = libutil.imsg_compose(self.buf, type, id, pid, fd, data, #data)
	assert(rv == 1)
end

imsgbufmeta.compose_ct = function(self, typ, id, pid, fd, ct)
	assert(type(ct) == "cdata")
	local rv = libutil.imsg_compose(self.buf, typ, id, pid, fd, ct, ffi.sizeof(ct))
	assert(rv == 1)
end

imsgbufmeta.read = function(self)
	local rv = libutil.imsgbuf_read(self.buf)
	return rv
end

local imsgmeta = {}

imsgmeta.type = function(self)
	return libutil.imsg_get_type(self.imsg)
end

imsgmeta.len = function(self)
	return libutil.imsg_get_len(self.imsg)
end

imsgmeta.as_ct = function(self, ct)
	assert(type(ct) == "cdata")
	local neu = ct()
	local sz = ffi.sizeof(neu)
	local rv = libutil.imsg_get_data(self.imsg, neu, sz)
	if rv ~= 0 then
		error("imsg_get_data: " .. unix.strerror(ffi.errno()))
	end

	return neu
end

local imsgtostring = function(self)
	local sz = self:len()
	local cp = ffi.new("char[?]", sz)

	local rv = libutil.imsg_get_data(self.imsg, cp, sz)
	if rv ~= 0 then
		error("imsg_get_data: " .. unix.strerror(ffi.errno()))
	end

	return ffi.string(cp, sz)
end

imsgbufmeta.get = function(self)
	local imsg = imsgtype()
	local n = libutil.imsg_get(self.buf, imsg)
	if n == -1 then
		error("imsg_get error")
	end
	if n == 0 then
		return 0, nil
	end

	ffi.gc(imsg, libutil.imsg_free)

	return n, setmetatable({imsg=imsg}, {__index=imsgmeta,
		__tostring=imsgtostring,
	})
end

t.init = function(fd)
	local buf = imsgbuftype()
	if libutil.imsgbuf_init(buf, fd) == -1 then
		error("imsgbuf_init failed")
	end
	return setmetatable({buf=buf}, {__index=imsgbufmeta})
end

return t

test.lua

local os = assert(require("os"))
local ffi = assert(require("ffi"))
local imsg = assert(require("imsg"))
local unix = assert(require("unix"))

local TYP_STRING = 42
local TYP_MSG = 41

local msgtype = ffi.typeof("struct { int answer; char data[32]; }")

local child_main = function(imsg)
	while true do
		local rv = buf1:read()
		if rv == 0 then
			return 0
		end

		while true do
			local n, msg = buf1:get()
			if n == -1 then
				error("read error?")
			end
			if n == 0 then
				break
			end
			local typ = msg:type()
			print("child", msg:type(), msg:len())
			if typ == TYP_STRING then
				print("child", msg)
			elseif typ == TYP_MSG then
				local m = msg:as_ct(msgtype)
				print("child", m.answer, ffi.string(m.data))
			end
		end
	end
end

local parent_main = function(imsg)
	imsg:compose(TYP_STRING, 0, 0, -1, "hello world")
	imsg:write()

	local m = msgtype()
	m.answer = 1234
	ffi.copy(m.data, "fnord")
	imsg:compose_ct(TYP_MSG, 0, 0, -1, m)
	imsg:write()
	return 0
end

p0, p1 = unix.socketpair()

local rv = unix.fork()
if rv == -1 then
	error("fork")
end
if rv == 0 then
	-- child
	unix.close(p0)
	buf1 = imsg.init(p1)
	os.exit(child_main(buf1))
end

unix.close(p1)
buf0 = imsg.init(p0)
os.exit(parent_main(buf0))

unix.lua

local ffi = require("ffi")
local bit = require("bit")

ffi.cdef[[
typedef uint32_t pid_t;

int close(int);

int socketpair(int domain, int type, int protocol, int sv[2]);

pid_t fork(void);

char *strerror(int);
]]

local t = {}

t.close = ffi.C.close
t.fork = ffi.C.fork

t.strerror = function(eno)
	return ffi.string(ffi.C.strerror(eno))
end

t.SOCK_STREAM = 1

t.SOCK_CLOEXEC = 0x8000
t.SOCK_NONBLOCK = 0x4000

t.AF_UNSPEC = 0
t.AF_UNIX = 1

t.PF_UNSPEC = t.AF_UNSPEC

t.socketpair = function()
	local fds = ffi.new("int[?]", 2)
	local r = ffi.C.socketpair(t.AF_UNIX, t.SOCK_STREAM, t.PF_UNSPEC, fds)
	if r == -1 then
		error(ffi.C.strerror(ffi.errno()))
	end

	return fds[0], fds[1]
end

return t