expose LPeg patterns

Signed-off-by: Asbjørn Sloth Tønnesen <ast@2e8.dk>

3 files changed, 102 insertions, 45 deletions

diff --git a/README.rst b/README.rst
index 207b1d9..b227b1a 100644
--- a/README.rst
+++ b/README.rst
@@ -76,6 +76,7 @@ API                     Description
 ``inet.is_set(foo)``    is ``set`` table?
 ``inet.set()``          get new empty ``set`` instance.
 ``inet.mixed_networks`` IPv6 mixed notation ``set``
+``inet.lpeg``           LPeg_ patterns
 ``inet.version``        API version (currently ``1``)
 ======================= =====================================================
 
@@ -188,6 +189,29 @@ There is a multitude of different ways to create ``inet*`` instances.
   inet('192.0.2.0', 33)     -- returns nil, 'invalid mask'
   inet('2001:db8::', 129)   -- returns nil, 'invalid mask'
 
+Usable in LPeg patterns
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Internally ``inet`` uses LPeg_ to parse IP adresses, but the
+LPeg patterns are also available for embedding into your
+own LPeg patterns.
+
+::
+
+  local lpeg = require 'lpeg'
+  local P = lpeg.P
+  local http_host_v6 = P('[') * inet.lpeg.ipv6 * P(']')
+  local http_host = http_host_v6 + inet.lpeg.ipv4
+  local my_http_uri = P('https://') * http_host * P('/') * -1
+
+  my_http_uri:match('https://192.0.2.0/')     -- returns inet('192.0.2.0')
+  my_http_uri:match('https://[2001:db8::1]/') -- returns inet('2001:db8::1')
+
+  inet.lpeg.ipv6:match('2001:db8::/64')       -- returns inet('2001:db8::/64')
+  inet.lpeg.ipv4:match('192.0.2.0/24')        -- returns inet('192.0.2.0/24')
+  inet.lpeg.ip:match('2001:db8::/64')         -- returns inet('2001:db8::/64')
+  inet.lpeg.ip:match('192.0.2.0/24')          -- returns inet('192.0.2.0/24')
+
 Mangling
 --------
 
diff --git a/lua/inet/core.lua b/lua/inet/core.lua
index 2b36543..a12a036 100644
--- a/lua/inet/core.lua
+++ b/lua/inet/core.lua
@@ -79,13 +79,42 @@ function inet:full_family()
 	return format('ipv%d', self:family())
 end
 
+local function build_bip(o1, o2, o3, o4)
+	return lshift(o1, 24) + lshift(o2, 16) + lshift(o3, 8) + o4
+end
+
+local function make_inet4(bip, mask)
+	return setmetatable({
+		bip = bip,
+		mask = mask or 32,
+	}, inet4)
+end
+
+local function make_inet6(pcs, mask)
+	local r = setmetatable({
+		pcs = pcs,
+		mask = mask or 128,
+	}, inet6)
+
+	-- ensure that the result is balanced
+	if not r:is_balanced() then
+		r:balance()
+		return nil, tostring(r)..' unbalanced'
+	end
+
+	return r
+end
+
+local ipv4_peg
 local ipv4_parser
+local ipv6_peg
 local ipv6_parser
 do
 	local lpeg = require 'lpeg'
 	local C, Ct = lpeg.C, lpeg.Ct
 	local S, R = lpeg.S, lpeg.R
 	local B, Cc = lpeg.B, lpeg.Cc
+	local Cmt = lpeg.Cmt
 
 	local digit = R('09')
 
@@ -105,7 +134,13 @@ do
 		local mask12 = R('12') * digit
 		local mask3 = S('3') * R('02')
 		local netmask = S('/') * C(mask12 + mask3 + digit)
-		ipv4_parser = ipv4addr * (netmask + Cc()) * -1
+		local ipv4_base = ipv4addr * (netmask + Cc()) /
+			function (o1, o2, o3, o4, mask)
+				local bip = build_bip(o1, o2, o3, o4)
+				return bip, tonumber(mask)
+			end
+		ipv4_parser = ipv4_base * -1
+		ipv4_peg = ipv4_base / make_inet4
 	end
 
 	do
@@ -124,20 +159,43 @@ do
 		local partial = (piece * (colpi^-6))^-1 * colcol * ((picol^-6)*(ipv4embed+piece))^-1
 		local netmask = S('/') * C((digit^-3)) / tonumber
 		local pieces = full + partial
-		ipv6_parser = Ct(pieces) * ((netmask + Cc())^-1) * -1
-	end
-end
+		local function check_pcs(_, _, pcs, mask)
+			if #pcs > 8 then return false end
+			if mask ~= nil and mask > 128 then return false end
+			return true, pcs, mask
+		end
 
-local function build_bip(o1, o2, o3, o4)
-	return lshift(o1, 24) + lshift(o2, 16) + lshift(o3, 8) + o4
+		local function expand_pieces(pcs)
+			local zero_pieces = 8 - #pcs
+			for i=1,#pcs do
+				if pcs[i] == '::' then
+					pcs[i] = 0
+					for j=#pcs,i,-1 do
+						pcs[j+zero_pieces] = pcs[j]
+					end
+					for j=1,zero_pieces do
+						pcs[i+j] = 0
+					end
+				end
+			end
+			assert(#pcs == 8, 'incorrect number of pieces')
+			return pcs
+		end
+
+		local ipv6_base = Cmt(Ct(pieces) * ((netmask + Cc())^-1), check_pcs) /
+			function (pcs, mask)
+				expand_pieces(pcs)
+				return pcs, mask
+			end
+		ipv6_parser = ipv6_base * -1
+		ipv6_peg = ipv6_base / make_inet6
+	end
 end
 
 local function inet4_from_string(ipstr)
-	local o1, o2, o3, o4, mask = ipv4_parser:match(ipstr)
-	if not o1 then return nil, 'parse error' end
-
-	local bip = build_bip(o1, o2, o3, o4)
-	return bip, tonumber(mask)
+	local bip, mask = ipv4_parser:match(ipstr)
+	if not bip then return nil, 'parse error' end
+	return bip, mask
 end
 
 local function inet4_from_number(bip)
@@ -166,23 +224,6 @@ local inet4_constructors = {
 local function inet6_from_string(ipstr)
 	local pcs, netmask = ipv6_parser:match(ipstr)
 	if not pcs then return nil, 'parse error' end
-	if #pcs > 8 then return nil, 'too many pieces' end
-	local zero_pieces = 8 - #pcs
-	for i=1,#pcs do
-		if pcs[i] == '::' then
-			pcs[i] = 0
-			for j=#pcs,i,-1 do
-				pcs[j+zero_pieces] = pcs[j]
-			end
-			for j=1,zero_pieces do
-				pcs[i+j] = 0
-			end
-		end
-	end
-	if #pcs > 8 then return nil, 'too many pieces' end
-	if netmask ~= nil and netmask > 128 then
-		return nil, 'invalid netmask'
-	end
 	return pcs, netmask
 end
 
@@ -239,28 +280,13 @@ end
 local function new_inet4(ip, mask)
 	local bip, outmask = generic_new(inet4_constructors, 32, ip, mask)
 	if not bip then return nil, outmask end
-	return setmetatable({
-		bip = bip,
-		mask = outmask,
-	}, inet4)
+	return make_inet4(bip, outmask)
 end
 
 local function new_inet6(ip, mask)
 	local pcs, outmask = generic_new(inet6_constructors, 128, ip, mask)
 	if not pcs then return nil, outmask end
-
-	local r = setmetatable({
-		pcs = pcs,
-		mask = outmask,
-	}, inet6)
-
-	-- ensure that the result is balanced
-	if not r:is_balanced() then
-		r:balance()
-		return nil, tostring(r)..' unbalanced'
-	end
-
-	return r
+	return make_inet6(pcs, outmask)
 end
 
 local function new_inet(ip, mask)
@@ -877,5 +903,10 @@ M.is_inet4 = is_inet4
 M.is_inet6 = is_inet6
 M.is_inet  = is_inet
 M.new_inet = new_inet
+M.lpeg = {
+	ipv4 = ipv4_peg,
+	ipv6 = ipv6_peg,
+	ip = ipv4_peg + ipv6_peg,
+}
 
 return M
diff --git a/lua/inet/init.lua b/lua/inet/init.lua
index 56c0eed..229fbd8 100644
--- a/lua/inet/init.lua
+++ b/lua/inet/init.lua
@@ -22,6 +22,8 @@ M.is4 = core.is_inet4
 M.is6 = core.is_inet6
 M.is  = core.is_inet
 
+M.lpeg = core.lpeg
+
 M.is_set = set.is_set
 M.set    = set.new