From 8e84eb0c676d18088783e0d4a882baeabde045d1 Mon Sep 17 00:00:00 2001
From: XeonSquared <redtailedairways@gmail.com>
Date: Wed, 26 May 2021 16:15:24 +1000
Subject: [PATCH] switched to using string.(un)pack in libmtar and liblz16,
 meaning it works on both big and little endian machines, and should be
 smaller and faster

---
 lib/liblz16.lua | 22 ++--------------------
 lib/libmtar.lua | 25 +++----------------------
 2 files changed, 5 insertions(+), 42 deletions(-)

diff --git a/lib/liblz16.lua b/lib/liblz16.lua
index 4165bb3..fe610f0 100644
--- a/lib/liblz16.lua
+++ b/lib/liblz16.lua
@@ -3,31 +3,13 @@ local buffer = require "buffer"
 
 lz16 = {}
 
-local function cint(n,l)
- local t={}
- for i = 0, 7 do
-  t[i+1] = (n >> (i * 8)) & 0xFF
- end
- return string.reverse(string.char(table.unpack(t)):sub(1,l))
-end
-local function toint(s)
- local n = 0
- local i = 1
- for p in s:gmatch(".") do
-  n = n << 8
-  n = n | string.byte(p)
-  i=i+1
- end
- return n
-end
-
 local function readBuffer(fi)
  local stream = {}
  if fi:read(4) ~= "lz16" then
   return false, "not an lz16 archive"
  end
  function stream.read()
-  local len = toint(fi:read(2) or "\0\0")
+  local len = string.unpack(">I2", fi:read(2) or "\0\0")
   if len < 1 then
    return nil
   end
@@ -44,7 +26,7 @@ local function writeBuffer(fo)
  local stream = {}
  function stream:write(data)
   local cblock = lz.compress(data)
-  fo:write(cint(cblock:len(),2)..cblock)
+  fo:write(string.pack(">I2", cblock:len()) .. cblock)
   return cblock:len()+2
  end
  function stream.close()
diff --git a/lib/libmtar.lua b/lib/libmtar.lua
index 9782336..88c7de8 100644
--- a/lib/libmtar.lua
+++ b/lib/libmtar.lua
@@ -1,24 +1,5 @@
 local mtar = {}
 
-local function toint(s)
- local n = 0
- local i = 1
- for p in s:gmatch(".") do
-  n = n << 8
-  n = n | string.byte(p)
-  i=i+1
- end
- return n
-end
-
-local function cint(n,l)
- local t={}
- for i = 0, 7 do
-  t[i+1] = (n >> (i * 8)) & 0xFF
- end
- return string.reverse(string.char(table.unpack(t)):sub(1,l))
-end
-
 local function cleanPath(path)
  local pt = {}
  for segment in path:gmatch("[^/]+") do
@@ -32,7 +13,7 @@ local function cleanPath(path)
 end
 
 function mtar.genHeader(fname,len) -- string number -- string -- generate a header for file *fname* when provided with file length *len*
- return string.format("%s%s%s",cint(fname:len(),2),fname,cint(len,2))
+ return string.format("%s%s%s", string.pack(">I2",fname:len()), fname, string.pack(">I2",len))
 end
 
 function mtar.iter(stream) -- table -- function -- Given buffer *stream*, returns an iterator suitable for use with *for* that returns, for each iteration, the file name, a function to read from the file, and the length of the file.
@@ -46,12 +27,12 @@ function mtar.iter(stream) -- table -- function -- Given buffer *stream*, return
   while remain > 0 do
    remain=remain-#stream:read(math.min(remain,2048))
   end
-  local nlen = toint(stream:read(2) or "\0\0")
+  local nlen = string.unpack(">I2", stream:read(2) or "\0\0")
   if nlen == 0 then
    return
   end
   local name = cleanPath(stream:read(nlen))
-  local fsize = toint(stream:read(2))
+  local fsize = string.unpack(">I2", stream:read(2))
   remain = fsize
   return name, read, fsize
  end