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Refactor some Lua string concatenations.

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Using this regular expression, '\(\w*\)\s*=\s*\1\s*\.\.', found and
replaced many string concatenation-reassignments. These can cause
performance issues, since a new string gets allocated for each
reassignment. In many cases, the replacement is simply a single string,
wrapped across lines with the '\z' escape, which consumes a newline and
whitespace following it. In other cases, a table is used to hold the
substrings until the final string is built with a single table.concat
operation (same technique used in stdnse.strbuf).

Also, some string-building loops of this form:

s = ""
for i = 1, 100, 1 do
  s = s .. "\0"
end

were replaced with this much faster and cleaner version:

s = string.rep("\0", 100)
This commit is contained in:
dmiller
2014-02-18 18:10:23 +00:00
parent 74ebf1c892
commit 1c0c090ace
7 changed files with 160 additions and 175 deletions
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44
nselib/rpc.lua
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@@ -325,10 +325,12 @@ Comm = {
packet = packet .. bin.pack( "IIII", 0, 0, 0, 0 )
elseif auth.type == Portmap.AuthType.UNIX then
packet = packet .. Util.marshall_int32(auth.type)
local blob = Util.marshall_int32(nmap.clock()) --time
blob = blob .. Util.marshall_vopaque(auth.hostname or 'localhost')
blob = blob .. Util.marshall_int32(auth.uid or 0)
blob = blob .. Util.marshall_int32(auth.gid or 0)
local blob = (
Util.marshall_int32(nmap.clock()) --time
.. Util.marshall_vopaque(auth.hostname or 'localhost')
.. Util.marshall_int32(auth.uid or 0)
.. Util.marshall_int32(auth.gid or 0)
)
if auth.gids then --len prefix gid list
blob = blob .. Util.marshall_int32(#auth.gids)
for _,gid in ipairs(auth.gids) do
@@ -337,8 +339,9 @@ Comm = {
else
blob = blob .. Util.marshall_int32(0)
end
packet = packet .. Util.marshall_vopaque(blob)
packet = packet .. bin.pack( "II", 0, 0 ) --AUTH_NULL verf
packet = (packet .. Util.marshall_vopaque(blob)
.. bin.pack( "II", 0, 0 ) --AUTH_NULL verf
)
else
return false, "Comm.CreateHeader: invalid authentication type specified"
end
@@ -2981,10 +2984,7 @@ Util =
-- @param mode number containing the ACL mode
-- @return string containing the ACL characters
FpermToString = function(mode)
local tmpacl, acl = {}, ""
for i = 1, 9 do
tmpacl[i] = "-"
end
local tmpacl = { "-", "-", "-", "-", "-", "-", "-", "-", "-" }
for user,_ in pairs(Util.Fperm) do
local t = Util.Fperm[user]
@@ -3009,11 +3009,7 @@ Util =
end
end
for i = 1,#tmpacl do
acl = acl .. tmpacl[i]
end
return acl
return table.concat(tmpacl)
end,
--- Converts the NFS file attributes to a string.
@@ -3096,11 +3092,7 @@ Util =
end,
marshall_opaque = function(data)
local opaque = bin.pack(">A", data)
for i = 1, Util.CalcFillBytes(data:len()) do
opaque = opaque .. string.char(0x00)
end
return opaque
return bin.pack(">A", data) .. string.rep("\0", Util.CalcFillBytes(data:len()))
end,
unmarshall_opaque = function(len, data, pos)
@@ -3108,13 +3100,11 @@ Util =
end,
marshall_vopaque = function(data)
local opaque, l
l = data:len()
opaque = Util.marshall_uint32(l) .. bin.pack(">A", data)
for i = 1, Util.CalcFillBytes(l) do
opaque = opaque .. string.char(0x00)
end
return opaque
local l = data:len()
return (
Util.marshall_uint32(l) .. bin.pack(">A", data) ..
string.rep("\0", Util.CalcFillBytes(l))
)
end,
unmarshall_vopaque = function(len, data, pos)