fix(vag_vehicle): unzip without overflowing gopher-lua's value stack

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## vag_vehicle 0.1.1
+
+A dataset of more than a few kB failed on a box with "registry overflow". FTW runs gopher-lua, whose `table.concat` puts every item of the range on a value stack of about 5,000 slots, and the unzip joined its whole output in one call. It now joins at most 256 items per call. The test harness refuses longer `table.concat` ranges too, since the C Lua the tests run has no such limit. The dataset cap drops from 4 MiB to 2 MiB: in FTW's host, 1 MB of JSON took 0.6 s to unzip and read on an Apple M-series core, a poll has 10 seconds, and a Raspberry Pi is several times slower.
+
 ## vag_vehicle 0.1.0
 
 Read-only VW, Audi, Škoda, SEAT and Cupra telemetry from the VW Group EU Data Act portal, the one owner door left now that We Connect's third-party APIs are closed. The owner orders a continuous 15-minute All Data delivery on the portal and pastes the Cookie header of a logged-in portal session: the Lua host has no cookie jar and cannot complete the portal's OIDC login, so the driver stops when that session ends. Every 5 minutes it lists the delivered files, downloads the newest one with content, unzips it in Lua (streamed zip entries included, 4 MiB cap) and emits `DerVehicle`: SoC, charge limit, charging state and time to full. Data keys follow VW's data dictionary V5.0. The newest file at start has an unknown age, so it is reported stale until a newer file arrives. Portal data are about 15 minutes old, so Core will mostly show this SoC rather than steer by it. Cloud access is not a charging prerequisite. Porsche, wake and charge start are out of scope. Not yet run against the portal or a car.

SUPPORT_STATUS.md

@@ -166,8 +166,8 @@ Catalog source is not proof that a target can install or run a driver.
 | teslamate_vehicle | 0.1.0 | blixt-l1 | not_assessed | — | not_recorded | not_assessed |
 | tibber | 1.1.2 | ftw-core | not_assessed | — | not_recorded | not_assessed |
 | tibber | 1.1.2 | blixt-l1 | not_assessed | — | not_recorded | not_assessed |
-| vag_vehicle | 0.1.0 | ftw-core | not_assessed | — | not_recorded | not_assessed |
-| vag_vehicle | 0.1.0 | blixt-l1 | not_assessed | — | not_recorded | not_assessed |
+| vag_vehicle | 0.1.1 | ftw-core | not_assessed | — | not_recorded | not_assessed |
+| vag_vehicle | 0.1.1 | blixt-l1 | not_assessed | — | not_recorded | not_assessed |
 | varta | 1.1.1 | ftw-core | not_assessed | — | not_recorded | not_assessed |
 | varta | 1.1.1 | blixt-l1 | not_assessed | — | not_recorded | not_assessed |
 | victron | 2.1.2 | ftw-core | not_assessed | — | not_recorded | not_assessed |

devices.yaml

@@ -2051,7 +2051,7 @@ manufacturers:
         protocols:
           - protocol: http
             driver: "vag_vehicle"
-            version: "0.1.0"
+            version: "0.1.1"
             ders: [vehicle]
             control: false
         firmware_versions: ""

drivers/lua/vag_vehicle.lua

@@ -52,7 +52,7 @@ DRIVER = {
   id           = "vag_vehicle",
   name         = "VAG Vehicle (EU Data Act)",
   manufacturer = "Volkswagen Group",
-  version      = "0.1.0",
+  version      = "0.1.1",
   protocols    = { "http" },
   capabilities = { "vehicle" },
   read_only    = true,
@@ -165,10 +165,31 @@ local function u32le(s, i)
 end
 
 -- A dataset larger than this is refused rather than inflated: the charging
--- fields need far less, and every driver shares the host's memory.
-local MAX_JSON_BYTES = 4194304
+-- fields need far less, every driver shares the host's memory, and a poll
+-- has 10 seconds. In FTW's gopher-lua, 1 MB of JSON took 0.6 s on an Apple
+-- M-series core; a Raspberry Pi is several times slower.
+local MAX_JSON_BYTES = 2097152
 -- DEFLATE back-references reach at most this far back.
 local WINDOW = 32768
+-- FTW runs gopher-lua, whose table.concat puts every item of the range on
+-- a value stack of about 5,000 slots, so a long range fails with "registry
+-- overflow". Join at most JOIN_STEP items per call.
+local JOIN_STEP = 256
+
+local function join(parts, first, last)
+  local level = {}
+  for i = first, last, JOIN_STEP do
+    level[#level + 1] = table.concat(parts, "", i, math.min(i + JOIN_STEP - 1, last))
+  end
+  while #level > 1 do
+    local up = {}
+    for i = 1, #level, JOIN_STEP do
+      up[#up + 1] = table.concat(level, "", i, math.min(i + JOIN_STEP - 1, #level))
+    end
+    level = up
+  end
+  return level[1] or ""
+end
 
 local function inflate_raw(src)
   local pos = 1
@@ -180,7 +201,7 @@ local function inflate_raw(src)
 
   local function flush()
     local keep = n - WINDOW
-    chunks[#chunks + 1] = table.concat(out, "", 1, keep)
+    chunks[#chunks + 1] = join(out, 1, keep)
     flushed = flushed + keep
     for i = 1, WINDOW do out[i] = out[keep + i] end
     for i = WINDOW + 1, n do out[i] = nil end
@@ -421,8 +442,8 @@ local function inflate_raw(src)
       return nil
     end
     if bfinal == 1 then
-      chunks[#chunks + 1] = table.concat(out, "", 1, n)
-      return table.concat(chunks)
+      chunks[#chunks + 1] = join(out, 1, n)
+      return join(chunks, 1, #chunks)
     end
   end
 end

drivers/tests/lua_harness/test_vag_vehicle.lua

@@ -1,12 +1,24 @@
 -- Telemetry-only VAG / EU Data Act vehicle driver.
--- Args: stored.zip deflated.zip streamed.zip oversized.zip nosoc.zip
+-- Args: stored.zip deflated.zip streamed.zip oversized.zip nosoc.zip large.zip
 
 dofile("drivers/tests/lua_harness/host_mock.lua")
 
-local stored_path, deflated_path, streamed_path, oversized_path, nosoc_path =
-    arg[1], arg[2], arg[3], arg[4], arg[5]
-assert(stored_path and deflated_path and streamed_path and oversized_path and nosoc_path,
-    "usage: test_vag_vehicle.lua stored.zip deflated.zip streamed.zip oversized.zip nosoc.zip")
+-- FTW runs gopher-lua, whose table.concat puts every item of the range on a
+-- value stack of about 5,000 slots. C Lua has no such limit, so refuse long
+-- ranges here too, or a driver that needs them passes this test and fails
+-- on a box with "registry overflow".
+local c_concat = table.concat
+table.concat = function(t, sep, i, j)
+    i = i or 1
+    j = j or #t
+    assert(j - i < 2000, "table.concat over " .. (j - i + 1) .. " items overflows gopher-lua")
+    return c_concat(t, sep, i, j)
+end
+
+local stored_path, deflated_path, streamed_path, oversized_path, nosoc_path, large_path =
+    arg[1], arg[2], arg[3], arg[4], arg[5], arg[6]
+assert(stored_path and deflated_path and streamed_path and oversized_path and nosoc_path and large_path,
+    "usage: test_vag_vehicle.lua stored.zip deflated.zip streamed.zip oversized.zip nosoc.zip large.zip")
 
 local function read_bin(path)
     local f = assert(io.open(path, "rb"))
@@ -20,6 +32,7 @@ local deflated_zip = read_bin(deflated_path)
 local streamed_zip = read_bin(streamed_path)
 local oversized_zip = read_bin(oversized_path)
 local nosoc_zip = read_bin(nosoc_path)
+local large_zip = read_bin(large_path)
 assert(#stored_zip > 0 and #deflated_zip > 0 and #streamed_zip > 0, "empty zip fixture")
 
 local VIN = "WVWZZZTESTVIN0001"
@@ -170,6 +183,18 @@ assert(logged("dataset too large"), "oversized dataset is logged")
 driver_poll()
 assert(#host._download_log == 1, "a refused file is not downloaded again")
 
+-- A few hundred kB of data points: the unzip flushes chunks, and every join
+-- stays short enough for gopher-lua.
+boot()
+listing({ file(OLD, "2026-09-26T06:45:00Z") })
+host._downloads[OLD] = stored_zip
+driver_poll()
+listing({ file(OLD, "2026-09-26T06:45:00Z"), file(FILE, "2026-09-26T07:00:00Z") })
+host._downloads[FILE] = large_zip
+driver_poll()
+assert(last_row().soc == 71, "large dataset decodes, got " .. tostring(last_row().soc))
+assert(last_row().soc_fresh == true, "large dataset is a fresh reading")
+
 -- A new file without SoC is read once and replays the last reading.
 boot()
 listing({ file(OLD, "2026-09-26T06:45:00Z") })

drivers/tests/test_vag_vehicle.py

@@ -56,18 +56,32 @@ def _zip_streamed() -> bytes:
 
 
 def _zip_oversized() -> bytes:
-    # About 5 MB of JSON that deflates to a few kB: over the driver's 4 MiB cap.
+    # About 5 MB of JSON that deflates to a few kB: over the driver's 2 MiB cap.
     text = json.dumps({"vin": "WVWZZZTESTVIN0001", "Data": [], "pad": " " * 5_000_000})
     return _zip(zipfile.ZIP_DEFLATED, text)
 
 
+def _zip_large() -> bytes:
+    # About 360 kB of data points: enough that unzipping flushes chunks.
+    rows = [
+        {"key": "00000000-0000-3000-8000-%012d" % i, "dataFieldName": "mileage",
+         "value": str(i), "timestampUtc": "2026-09-26T07:00:00Z"}
+        for i in range(3000)
+    ]
+    rows.append({"key": "162c2a75-edf4-3990-b8ed-7c600b3dbc40",
+                 "dataFieldName": "battery_level_HV.value", "value": "71",
+                 "timestampUtc": "2026-09-26T07:00:00Z"})
+    return _zip(zipfile.ZIP_DEFLATED, json.dumps({"vin": "WVWZZZTESTVIN0001", "Data": rows}))
+
+
 def test_vag_vehicle_dataset_and_freshness(tmp_path: Path) -> None:
     fixtures = {
         "stored": _zip(zipfile.ZIP_STORED),
         "deflated": _zip(zipfile.ZIP_DEFLATED),
         "streamed": _zip_streamed(),
         "oversized": _zip_oversized(),
         "nosoc": _zip(zipfile.ZIP_DEFLATED, NO_SOC),
+        "large": _zip_large(),
     }
     paths = []
     for name, blob in fixtures.items():

index.yaml

@@ -748,15 +748,15 @@ drivers:
     size_bytes: 12472
     sha256: "3cf10b93755fa8b840375f53343e91b5efa98ddffe119a5679b43ee4bfb61c88"
   - name: "vag_vehicle"
-    version: "0.1.0"
+    version: "0.1.1"
     tier: community
     protocol: http
     connectivity: cloud
     setup: [vendor_portal]
     ders: [vehicle]
     control: false
-    size_bytes: 27869
-    sha256: "eaa1b985db5deb897a1aa95596eeb8bedc6c0ac50cabcf14e273a9070edfe227"
+    size_bytes: 28621
+    sha256: "907bb6f845765771a026d3b63f2080f941a6225a7fb51789898ee37e890f0856"
   - name: "varta"
     version: "1.1.1"
     tier: community

manifests/vag_vehicle.yaml

@@ -1,5 +1,5 @@
 name: "vag_vehicle"
-version: "0.1.0"
+version: "0.1.1"
 tier: community
 author: "Sourceful Labs AB"
 protocol: http
@@ -21,9 +21,9 @@ upstream_docs:
     kind: other
     url_stability: stable
 min_host_version: "2.0.0"
-size_bytes: 27869
+size_bytes: 28621
 dkb_id: "vag_vehicle"
-sha256: "eaa1b985db5deb897a1aa95596eeb8bedc6c0ac50cabcf14e273a9070edfe227"
+sha256: "907bb6f845765771a026d3b63f2080f941a6225a7fb51789898ee37e890f0856"
 signature: ""
 
 bytecode_sha256: ""

support-status.json

@@ -1703,7 +1703,7 @@
     },
     {
       "catalog_source": true,
-      "catalog_version": "0.1.0",
+      "catalog_version": "0.1.1",
       "driver_id": "vag_vehicle",
       "targets": {
         "blixt-l1": {