auras: scan through GetAuraSlots instead of by-index loops

Every aura scan loop (unit frame buffs/debuffs, dispel indicators, buff and
custom indicators, player buff frame, buffwatch bars, tooltip buff row) now
enumerates a unit's auras once with C_UnitAuras.GetAuraSlots and reads each
aura by slot id via the positional C_UnitAuras.UnitAuraBySlot. The by-index
getters re-walk the aura array from slot 0 on every call, so a per-button
loop over them was quadratic in the aura count; one enumeration plus a
by-slot read per aura is linear.

pfUI.api.ScanAuraSlots(unit, filter, buf, max) wraps GetAuraSlots' fill-a-
table form (table as the 5th argument) so no vararg Lua frame is involved:
Lua 5.0 allocates an `arg` table for every vararg call, which showed up as
nameplate OnUpdate/OnEvent memory growth in the first cut of this change.

Single by-index reads in tooltip and click handlers are unchanged (one call
each, and SetUnitAura takes the same index).

Requires the ClassicAPI build that adds GetAuraSlots' fill form; on an older
DLL the 5th argument is ignored and ScanAuraSlots would read the first slot
id as the count.

api/api.lua

@@ -204,6 +204,26 @@ function pfUI.api.UnitHasBuff(unit, name)
   return C_UnitAuras.GetAuraDataBySpellName(unit, name, "HELPFUL") ~= nil or nil
 end
 
+-- [ ScanAuraSlots ]
+-- Fills `buf` with the slot ids of the auras on `unit` that match `filter` and
+-- returns how many (buf[1..n]; entries past n are cleared), so a module can
+-- keep one buffer and refill it every refresh. Read each aura with
+-- C_UnitAuras.UnitAuraBySlot(unit, buf[i]) (positional, no table) or
+-- GetAuraDataBySlot. One enumeration walks the aura array once, where a
+-- by-index loop (UnitAura(unit, i)) re-walks it from the start for every i.
+-- Uses GetAuraSlots' fill-a-table form (table as the 5th argument) instead of
+-- its vararg return: Lua 5.0 builds an `arg` table for every vararg call, so
+-- collecting the returns in a Lua helper would allocate once per scan.
+-- unit         [string]        unit token
+-- filter       [string]        aura filter ("HELPFUL", "HARMFUL|PLAYER", ...)
+-- buf          [table]         reusable buffer, filled in place
+-- max          [number]        optional cap on the slot count (nil = all)
+-- return:      [number]        count of slot ids written to buf
+function pfUI.api.ScanAuraSlots(unit, filter, buf, max)
+  local _, n = C_UnitAuras.GetAuraSlots(unit, filter, max, nil, buf)
+  return n
+end
+
 -- [ IsPlayerGuid ]
 -- Returns whether a GUID or unit token refers to the local player.
 -- guid         [string]        A unit GUID (or unitID) to test.

api/unitframes.lua

@@ -4,6 +4,12 @@ setfenv(1, pfUI:GetEnvironment())
 pfUI.uf = CreateFrame("Frame", nil, UIParent)
 pfUI.uf.frames = {}
 
+-- Reusable buffer for C_UnitAuras.GetAuraSlots slot ids (filled by
+-- ScanAuraSlots, api.lua). Each aura scan in RefreshUnit fills it once, then
+-- reads every aura by slot id: one array walk per scan instead of one per index.
+-- Scans run back to back and consume the buffer before the next refill.
+local auraSlots = {}
+
 -- ============================================================================
 -- GUID-based Roster Tracking for Smart Updates
 -- Only updates frames where the unit actually changed, not ALL 40 frames
@@ -1635,11 +1641,13 @@ function pfUI.uf:RefreshUnit(unit, component)
 
   -- buffs
   if unit.buffs and ( component == "all" or component == "aura" ) then
+    -- one GetAuraSlots enumeration per refresh, then a positional read per
+    -- slot id: allocates nothing and never re-walks the aura array per icon
+    ScanAuraSlots(unitstr, "HELPFUL", auraSlots, unit.config.bufflimit)
     for i=1, unit.config.bufflimit do
       if not unit.buffs[i] then break end
 
-      -- positional UnitBuff allocates nothing (vs a table per icon per refresh)
-      local name, icon, count, _, duration, expirationTime, _, _, _, spellId = C_UnitAuras.UnitBuff(unitstr, i)
+      local name, icon, count, _, duration, expirationTime, _, _, _, spellId = C_UnitAuras.UnitAuraBySlot(unitstr, auraSlots[i])
 
       if name then
         unit.buffs[i].texture:SetTexture(icon)
@@ -1723,6 +1731,13 @@ function pfUI.uf:RefreshUnit(unit, component)
       reposition = true
     end
 
+    -- selfdebuff narrows to player-cast harmful auras via the PLAYER filter.
+    -- Player-frame debuffs aren't gated on it (it'd hide most party-applied
+    -- effects on you). One GetAuraSlots enumeration per refresh; the i-th slot
+    -- is the i-th aura of the filtered list, so `i` stays the tooltip index.
+    local filter = (unit.label ~= "player" and selfdebuff == "1") and "HARMFUL|PLAYER" or "HARMFUL"
+    ScanAuraSlots(unitstr, filter, auraSlots, unit.config.debufflimit)
+
     for i=1, unit.config.debufflimit do
       if not unit.debuffs[i] then break end
 
@@ -1739,12 +1754,8 @@ function pfUI.uf:RefreshUnit(unit, component)
         invert_h * ((row+buffrow)*(multiply*default_border + unit.config.debuffsize + 1) + (multiply*default_border + 1)))
       end
 
-      -- selfdebuff narrows to player-cast harmful auras via the PLAYER filter.
-      -- Player-frame debuffs aren't gated on it (it'd hide most party-applied
-      -- effects on you).
-      -- positional UnitDebuff allocates nothing; PLAYER predicate honored for selfdebuff
-      local filter = (unit.label ~= "player" and selfdebuff == "1") and "PLAYER" or nil
-      local name, icon, count, dispelType, duration, expirationTime = C_UnitAuras.UnitDebuff(unitstr, i, filter)
+      -- positional read by slot id allocates nothing
+      local name, icon, count, dispelType, duration, expirationTime = C_UnitAuras.UnitAuraBySlot(unitstr, auraSlots[i])
       if name then
         texture, stacks, dtype = icon, count, dispelType
       else
@@ -1834,8 +1845,9 @@ function pfUI.uf:RefreshUnit(unit, component)
       local present = pfUI.uf.dispelPresent or {}
       pfUI.uf.dispelPresent = present
       for k in pairs(present) do present[k] = nil end
-      for i=1,16 do
-        local name, _, _, dispelType = C_UnitAuras.UnitDebuff(unitstr, i)
+      local n = ScanAuraSlots(unitstr, "HARMFUL", auraSlots)
+      for i=1,n do
+        local name, _, _, dispelType = C_UnitAuras.UnitAuraBySlot(unitstr, auraSlots[i])
         if name and dispelType and dispelType ~= "" then present[dispelType] = true end
       end
 
@@ -1925,9 +1937,9 @@ function pfUI.uf:RefreshUnit(unit, component)
 
     local pos = 1
     if table.getn(unit.indicators) > 0 then
-      local i = 1
-      while true do
-        local name, icon, count, _, _, expirationTime = C_UnitAuras.UnitBuff(unitstr, i)
+      local n = ScanAuraSlots(unitstr, "HELPFUL", auraSlots)
+      for i=1,n do
+        local name, icon, count, _, _, expirationTime = C_UnitAuras.UnitAuraBySlot(unitstr, auraSlots[i])
         if not name then break end
         local texLower = string.lower(icon)
         local timeleft = expirationTime > 0 and (expirationTime - GetTime()) or nil
@@ -1948,14 +1960,13 @@ function pfUI.uf:RefreshUnit(unit, component)
             break
           end
         end
-        i = i + 1
       end
     end
 
     if table.getn(unit.indicator_custom) > 0 then
-      local ai = 1
-      while true do
-        local name, icon, count, _, _, expirationTime = C_UnitAuras.UnitBuff(unitstr, ai)
+      local n = ScanAuraSlots(unitstr, "HELPFUL", auraSlots)
+      for i=1,n do
+        local name, icon, count, _, _, expirationTime = C_UnitAuras.UnitAuraBySlot(unitstr, auraSlots[i])
         if not name then break end
         local timeleft = expirationTime > 0 and (expirationTime - GetTime()) or nil
         local lowerName = string.lower(name)
@@ -1966,12 +1977,12 @@ function pfUI.uf:RefreshUnit(unit, component)
             break
           end
         end
-        ai = ai + 1
       end
 
-      local debuffFilter = unit.config.selfdebuff == "1" and "PLAYER" or nil
-      for i=1,16 do -- scan for custom debuffs
-        local name, icon, count, _, _, expirationTime = C_UnitAuras.UnitDebuff(unitstr, i, debuffFilter)
+      local debuffFilter = unit.config.selfdebuff == "1" and "HARMFUL|PLAYER" or "HARMFUL"
+      n = ScanAuraSlots(unitstr, debuffFilter, auraSlots)
+      for i=1,n do -- scan for custom debuffs
+        local name, icon, count, _, _, expirationTime = C_UnitAuras.UnitAuraBySlot(unitstr, auraSlots[i])
         if name then
           local timeleft = expirationTime > 0 and (expirationTime - GetTime()) or nil
           for _, filter in pairs(unit.indicator_custom) do

modules/buff.lua

@@ -7,6 +7,15 @@ pfUI:RegisterModule("buff", function ()
 
   local br, bg, bb, ba = GetStringColor(pfUI_config.appearance.border.color)
 
+  -- Player aura slot ids, enumerated once per refresh pass (ScanPlayerAuraSlots)
+  -- and read per button by its aura index: one GetAuraSlots walk per range
+  -- instead of a by-index walk per button.
+  local helpfulSlots, harmfulSlots = {}, {}
+  local function ScanPlayerAuraSlots()
+    ScanAuraSlots("player", "HELPFUL", helpfulSlots, 32)
+    ScanAuraSlots("player", "HARMFUL", harmfulSlots, 16)
+  end
+
   local function RefreshBuffButton(buff)
     if buff.btype == "HELPFUL" then
       if C.buffs.separateweapons == "1" then
@@ -23,7 +32,8 @@ pfUI:RegisterModule("buff", function ()
       CreateBackdropShadow(buff)
     end
 
-    local name, icon, count, dispelType, _, expirationTime, _, _, _, spellId = C_UnitAuras.UnitAura("player", buff.id, buff.btype)
+    local slots = buff.btype == "HELPFUL" and helpfulSlots or harmfulSlots
+    local name, icon, count, dispelType, _, expirationTime, _, _, _, spellId = C_UnitAuras.UnitAuraBySlot("player", slots[buff.id])
 
     --detect weapon buffs
     if buff.btype == "HELPFUL" and ((C.buffs.separateweapons == "0" and buff.gid <= pfUI.buff.wepbuffs.count) or (pfUI.buff.wepbuffs.count > 0 and buff.weapon ~= nil)) then
@@ -166,6 +176,8 @@ pfUI:RegisterModule("buff", function ()
       pfUI.buff.wepbuffs.count = 0
     end
 
+    ScanPlayerAuraSlots()
+
     for i=1,32 do
       RefreshBuffButton(pfUI.buff.buffs.buttons[i])
     end
@@ -246,6 +258,9 @@ pfUI:RegisterModule("buff", function ()
     end
   end)
 
+  -- CreateBuffButton refreshes each new button from the slot buffers
+  ScanPlayerAuraSlots()
+
   -- Weapon Buffs
   pfUI.buff.wepbuffs = CreateFrame("Frame", "pfWepBuffFrame", UIParent)
   pfUI.buff.wepbuffs.count = 0

modules/buffwatch.lua

@@ -73,9 +73,12 @@ pfUI:RegisterModule("buffwatch", function ()
     return anchor
   end
 
-  local function GetBuffData(unit, id, type, selfdebuff)
-    local filter = (selfdebuff and type == "HARMFUL") and "HARMFUL|PLAYER" or type
-    local name, icon, count, dispelType, _, expirationTime = C_UnitAuras.UnitAura(unit, id, filter)
+  -- reusable GetAuraSlots buffer, filled once per RefreshBuffBarFrame
+  local auraSlots = {}
+
+  -- Reads one aura by the slot id GetAuraSlots returned (nil slot -> nil).
+  local function GetBuffData(unit, slot)
+    local name, icon, count, dispelType, _, expirationTime = C_UnitAuras.UnitAuraBySlot(unit, slot)
     if not name then return end
     local remaining = expirationTime > 0 and (expirationTime - GetTime()) or 0
     return remaining, icon, name, count, dispelType
@@ -234,9 +237,15 @@ pfUI:RegisterModule("buffwatch", function ()
   local function RefreshBuffBarFrame(frame)
     -- reinitialize all active buffs
     local selfdebuff = frame.config.selfdebuff == "1"
+    local filter = (selfdebuff and frame.type == "HARMFUL") and "HARMFUL|PLAYER" or frame.type
+
+    -- one GetAuraSlots enumeration per refresh instead of a by-index walk per
+    -- bar; the i-th slot is the i-th aura of the filtered list, so `i` stays
+    -- the index the tooltip / cancel handlers pass to the by-index API
+    ScanAuraSlots(frame.unit, filter, auraSlots, 32)
 
     for i=1,32 do
-      local timeleft, texture, name, stacks, dtype = GetBuffData(frame.unit, i, frame.type, selfdebuff)
+      local timeleft, texture, name, stacks, dtype = GetBuffData(frame.unit, auraSlots[i])
       timeleft = timeleft or 0
 
       if texture and name and name ~= "" and BuffIsVisible(frame.config, name) then

modules/nameplates.lua

@@ -116,6 +116,7 @@ pfUI:RegisterModule("nameplates", function ()
   -- Reusable per-plate debuff display buffer (avoid GC churn from per-call table creation)
   local debuffDisplayBuf = {}  -- [i] = { effect, texture, stacks, dtype, duration, timeleft }
   for i = 1, 16 do debuffDisplayBuf[i] = {} end
+  local auraSlots = {}  -- reusable GetAuraSlots buffer for the per-plate aura scan
   local threatMemory = {}   -- guid -> true if mob had player targeted
   -- local debuffSeen = {}     -- reusable table for debuff tracking (avoid GC churn)
 
@@ -1312,11 +1313,12 @@ nameplates:RegisterEvent("PLAYER_GUILD_UPDATE")
       if unitstr then
         local filter = cfg.owndebuffs and "HARMFUL|PLAYER" or "HARMFUL"
         local now = GetTime()
-        -- positional UnitAura writes straight into the reusable buffer, so the
-        -- per-plate scan allocates nothing (no per-aura table, no result array)
-        local i = 1
-        while debuffCount < 16 do
-          local aname, icon, count, dispelType, duration, expirationTime = C_UnitAuras.UnitAura(unitstr, i, filter)
+        -- one GetAuraSlots enumeration, then positional by-slot reads straight
+        -- into the reusable buffer: the per-plate scan allocates nothing (no
+        -- per-aura table, no result array) and walks the aura array once
+        local n = ScanAuraSlots(unitstr, filter, auraSlots, 16)
+        for i = 1, n do
+          local aname, icon, count, dispelType, duration, expirationTime = C_UnitAuras.UnitAuraBySlot(unitstr, auraSlots[i])
           if not aname then break end
           debuffCount = debuffCount + 1
           local b = debuffDisplayBuf[debuffCount]
@@ -1326,7 +1328,6 @@ nameplates:RegisterEvent("PLAYER_GUILD_UPDATE")
           b.dtype = dispelType
           b.duration = duration
           b.timeleft = (expirationTime and expirationTime > 0) and (expirationTime - now) or nil
-          i = i + 1
         end
       end
       for i = 1, 16 do

modules/tooltip.lua

@@ -189,6 +189,7 @@ pfUI:RegisterModule("tooltip", function ()
   -- Icons come from a ClassicAPI object pool: ReleaseAll hides the whole
   -- set each refresh, then we Acquire and re-anchor left-to-right.
   local BUFF_SIZE, BUFF_SPACING, BUFF_MAX = 20, 2, 32
+  local auraSlots = {}  -- reusable GetAuraSlots buffer for UpdateBuffs
   pfUI.tooltip.buffs = CreateFrame("Frame", "pfTooltipBuffs", GameTooltip)
   pfUI.tooltip.buffs:SetPoint("BOTTOMLEFT", GameTooltipStatusBar, "TOPLEFT", 0, default_border + 2)
   pfUI.tooltip.buffs:SetHeight(BUFF_SIZE)
@@ -239,17 +240,20 @@ pfUI:RegisterModule("tooltip", function ()
     end
 
     local prev, count = nil, 0
-    for i = 1, BUFF_MAX do
-      local aura = C_UnitAuras.GetBuffDataByIndex(unit, i)
-      if not aura then break end
+    -- one GetAuraSlots enumeration + positional by-slot reads: no per-aura
+    -- table and no per-index re-walk of the aura array
+    local n = ScanAuraSlots(unit, "HELPFUL", auraSlots, BUFF_MAX)
+    for i = 1, n do
+      local name, texture, applications, _, _, expirationTime = C_UnitAuras.UnitAuraBySlot(unit, auraSlots[i])
+      if not name then break end
 
       count = count + 1
       local icon = pfUI.tooltip.buffpool:Acquire()
-      icon.texture:SetTexture(aura.icon)
-      icon.stacks:SetText(aura.applications and aura.applications > 1 and aura.applications or "")
+      icon.texture:SetTexture(texture)
+      icon.stacks:SetText(applications and applications > 1 and applications or "")
 
-      icon.expirationTime = aura.expirationTime
-      local timeleft = aura.expirationTime and aura.expirationTime > 0 and (aura.expirationTime - GetTime()) or 0
+      icon.expirationTime = expirationTime
+      local timeleft = expirationTime and expirationTime > 0 and (expirationTime - GetTime()) or 0
       icon.timer:SetText(timeleft > 0 and GetColoredTimeString(timeleft) or "")
 
       if prev then