added mtar.iter to libmtar

mtar/libmtar.lua

@@ -54,6 +54,26 @@ function mtar.genHeader(fname,len) -- generate a header for file *fname* when pr
  return string.format("%s%s%s",cint(fname:len(),2),fname,cint(len,2))
 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.
+ local remain = 0
+ local function read(n)
+  local rb = stream:read(math.min(n,remain))
+  remain = remain - rb:len()
+  return rb
+ end
+ return function()
+  stream:read(remain)
+  local nlen = toint(stream:read(2) or "\0\0")
+  if nlen == 0 then
+   return
+  end
+  local name = cleanPath(stream:read(nlen))
+  local fsize = toint(stream:read(2))
+  remain = fsize
+  return name, read, fsize
+ end
+end
+
 function mtar.unarchive(stream,dest,verbose) -- Extract mtar archive read from *stream* to *dest*. If *verbose*, print status.
  dest = dest or "."
  while true do