--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hglib.lua	Wed Sep 07 16:07:39 2016 +0800
@@ -0,0 +1,70 @@
+local sizes = { i4 = 4, u4 = 4, c = 1 }
+
+local function read_u4(rh)
+	local value = 0
+	for i = 1, sizes.u4 do
+		local byte = rh:read(1):byte()
+		value = value + byte * (2 ^ ((sizes.u4 - i) * 8))
+	end
+	return value
+end
+
+local function read_c(rh)
+	return rh:read(sizes.c)
+end
+
+local function read_channel(rh)
+	local channel = read_c(rh)
+	local length = read_u4(rh)
+	if channel == 'I' or channel == 'L' then
+		return channel, length
+	else
+		return channel, rh:read(length)
+	end
+end
+
+local Client = {}
+Client.__index = Client
+
+function Client.connect(rh, wh)
+	local client = {}
+	setmetatable(client, Client)
+	client.rh = rh
+	client.wh = wh
+	return client
+end
+
+function Client:read_hello()
+	local channel, message = read_channel(self.rh)
+	assert(channel == 'o', 'channel for the hello message must be "o"')
+	local index = 1
+	while index <= #message do
+		local nexteol = message:find('\n', index + 1, true)
+		if nexteol == nil then nexteol = #message + 1 end
+		local line = message:sub(index, nexteol - 1)
+		local ci = line:find(': ', 1, true)
+		if ci ~= nil then
+			local key, value = line:sub(1, ci - 1), line:sub(ci + 2)
+			if key == 'capabilities' then
+				self.capabilities = {}
+				for cap in value:gmatch('%S+') do
+					self.capabilities[cap] = true
+				end
+			elseif key == 'encoding' then
+				self.encoding = value
+			elseif key == 'pid' then
+				self.pid = tonumber(value)
+			elseif key == 'pgid' then
+				self.pgid = tonumber(value)
+			end
+		end
+		index = nexteol + 1
+	end
+end
+
+return {
+	read_u4 = read_u4,
+	read_c = read_c,
+	read_channel = read_channel,
+	Client = Client
+}

Binary file spec/data/hello has changed

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spec/hglib_spec.lua	Wed Sep 07 16:07:39 2016 +0800
@@ -0,0 +1,15 @@
+local hglib = require('hglib')
+
+describe('hglib client', function()
+	it('can read hello', function()
+		local rh = io.open('spec/data/hello', 'rb')
+		local client = hglib.Client.connect(rh, nil)
+		client:read_hello()
+		rh:close()
+		assert.is_true(client.capabilities.getencoding)
+		assert.is_true(client.capabilities.runcommand)
+		assert.are_equal('UTF-8', client.encoding)
+		assert.are_equal(3615, client.pid)
+		assert.are_equal(3615, client.pgid)
+	end)
+end)