support multiple filters in ltn12.{sink,source}.chain()

src/ltn12.lua

@@ -139,7 +139,9 @@ function source.rewind(src)
     end
 end
 
-function source.chain(src, f)
+-- chains a source with one or several filter(s)
+function source.chain(src, f, ...)
+    if ... then f=filter.chain(f, ...) end
     base.assert(src and f)
     local last_in, last_out = "", ""
     local state = "feeding"
@@ -254,8 +256,13 @@ function sink.error(err)
     end
 end
 
--- chains a sink with a filter
+-- chains a sink with one or several filter(s)
-function sink.chain(f, snk)
+function sink.chain(f, snk, ...)
+    if ... then
+        local args = { f, snk, ... }
+        snk = table.remove(args, #args)
+        f = filter.chain(unpack(args))
+    end
     base.assert(f and snk)
     return function(chunk, err)
         if chunk ~= "" then

test/ltn12test.lua

@@ -191,6 +191,21 @@ assert(table.concat(t) == s, "mismatch")
 assert(filter(nil, 1), "filter not empty")
 print("ok")
 
+--------------------------------
+io.write("testing source.chain (with several filters): ")
+local function double(x) -- filter turning "ABC" into "AABBCC"
+    if not x then return end
+    local b={}
+    for k in x:gmatch'.' do table.insert(b, k..k) end
+    return table.concat(b)
+end
+source = ltn12.source.string(s)
+source = ltn12.source.chain(source, double, double, double)
+sink, t = ltn12.sink.table()
+assert(ltn12.pump.all(source, sink), "returned error")
+assert(table.concat(t) == double(double(double(s))), "mismatch")
+print("ok")
+
 --------------------------------
 io.write("testing source.chain (with split) and sink.chain (with merge): ")
 source = ltn12.source.string(s)
@@ -205,6 +220,15 @@ assert(filter(nil, 1), "filter not empty")
 assert(filter2(nil, 1), "filter2 not empty")
 print("ok")
 
+--------------------------------
+io.write("testing sink.chain (with several filters): ")
+source = ltn12.source.string(s)
+sink, t = ltn12.sink.table()
+sink = ltn12.sink.chain(double, double, double, sink)
+assert(ltn12.pump.all(source, sink), "returned error")
+assert(table.concat(t) == double(double(double(s))), "mismatch")
+print("ok")
+
 --------------------------------
 io.write("testing filter.chain (and sink.chain, with split, merge): ")
 source = ltn12.source.string(s)
@@ -272,3 +296,4 @@ assert(filter3(nil, 1), "filter3 not empty")
 assert(filter4(nil, 1), "filter4 not empty")
 assert(filter5(nil, 1), "filter5 not empty")
 print("ok")
+