From 8a24ec9653c09224a5e2d011e61067ddb11c1fe0 Mon Sep 17 00:00:00 2001
From: Matthew Wild <mwild1@gmail.com>
Date: Thu, 17 Sep 2020 13:00:19 +0100
Subject: net.websocket.frames: Allow all methods to work on non-string objects

Instead of using the string library, use methods from the passed object,
which are assumed to be equivalent.

This provides compatibility with objects from util.ringbuffer and
util.dbuffer, for example.
---
 net/websocket/frames.lua | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/net/websocket/frames.lua b/net/websocket/frames.lua
index ba25d261..e1b5527a 100644
--- a/net/websocket/frames.lua
+++ b/net/websocket/frames.lua
@@ -16,13 +16,12 @@ local bor = bit.bor;
 local bxor = bit.bxor;
 local lshift = bit.lshift;
 local rshift = bit.rshift;
+local unpack = table.unpack or unpack; -- luacheck: ignore 113
 
 local t_concat = table.concat;
-local s_byte = string.byte;
 local s_char= string.char;
-local s_sub = string.sub;
-local s_pack = string.pack; -- luacheck: ignore 143
-local s_unpack = string.unpack; -- luacheck: ignore 143
+local s_pack = string.pack;
+local s_unpack = string.unpack;
 
 if not s_pack and softreq"struct" then
 	s_pack = softreq"struct".pack;
@@ -30,12 +29,12 @@ if not s_pack and softreq"struct" then
 end
 
 local function read_uint16be(str, pos)
-	local l1, l2 = s_byte(str, pos, pos+1);
+	local l1, l2 = str:byte(pos, pos+1);
 	return l1*256 + l2;
 end
 -- FIXME: this may lose precision
 local function read_uint64be(str, pos)
-	local l1, l2, l3, l4, l5, l6, l7, l8 = s_byte(str, pos, pos+7);
+	local l1, l2, l3, l4, l5, l6, l7, l8 = str:byte(pos, pos+7);
 	local h = lshift(l1, 24) + lshift(l2, 16) + lshift(l3, 8) + l4;
 	local l = lshift(l5, 24) + lshift(l6, 16) + lshift(l7, 8) + l8;
 	return h * 2^32 + l;
@@ -63,9 +62,15 @@ end
 
 if s_unpack then
 	function read_uint16be(str, pos)
+		if type(str) ~= "string" then
+			str, pos = str:sub(pos, pos+1), 1;
+		end
 		return s_unpack(">I2", str, pos);
 	end
 	function read_uint64be(str, pos)
+		if type(str) ~= "string" then
+			str, pos = str:sub(pos, pos+7), 1;
+		end
 		return s_unpack(">I8", str, pos);
 	end
 end
@@ -73,7 +78,7 @@ end
 local function parse_frame_header(frame)
 	if #frame < 2 then return; end
 
-	local byte1, byte2 = s_byte(frame, 1, 2);
+	local byte1, byte2 = frame:byte(1, 2);
 	local result = {
 		FIN = band(byte1, 0x80) > 0;
 		RSV1 = band(byte1, 0x40) > 0;
@@ -102,7 +107,7 @@ local function parse_frame_header(frame)
 	end
 
 	if result.MASK then
-		result.key = { s_byte(frame, length_bytes+3, length_bytes+6) };
+		result.key = { frame:byte(length_bytes+3, length_bytes+6) };
 	end
 
 	return result, header_length;
@@ -121,7 +126,7 @@ local function apply_mask(str, key, from, to)
 	for i = from, to do
 		local key_index = counter%key_len + 1;
 		counter = counter + 1;
-		data[counter] = s_char(bxor(key[key_index], s_byte(str, i)));
+		data[counter] = s_char(bxor(key[key_index], str:byte(i)));
 	end
 	return t_concat(data);
 end
@@ -189,7 +194,7 @@ local function parse_close(data)
 	if #data >= 2 then
 		code = read_uint16be(data, 1);
 		if #data > 2 then
-			message = s_sub(data, 3);
+			message = data:sub(3);
 		end
 	end
 	return code, message
-- 
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