From abe0bef99ac3ad7bd5f9dadc90235ecc8a13260b Mon Sep 17 00:00:00 2001
From: Martin Preuss <martin@aquamaniac.de>
Date: Fri, 8 May 2026 22:08:47 +0200
Subject: [PATCH] gui, heap: modified how the heap works.

not well enough tested, yet.
---
 avr/modules/heap/main.asm            | 272 ++++++++++++++++-----------
 avr/modules/lcd2/gui/base/layout.asm |   4 +-
 2 files changed, 160 insertions(+), 116 deletions(-)

diff --git a/avr/modules/heap/main.asm b/avr/modules/heap/main.asm
index a3938ac..9f05225 100644
--- a/avr/modules/heap/main.asm
+++ b/avr/modules/heap/main.asm
@@ -48,24 +48,31 @@ heapDblFree: .byte 1
 Heap_Init:
   ldi xl, LOW(HEAP_START)
   ldi xh, HIGH(HEAP_START)
-  ldi r24, LOW((HEAP_SIZE-6) & 0xfffc)  ; size minus chunk header, chunk footer, start, end
-  ldi r25, HIGH((HEAP_SIZE-6) & 0xfffc) ; we allocate multiples of 4 bytes
+  ldi r24, LOW((HEAP_SIZE-8) & 0xfffc)  ; size minus chunk header, chunk footer, start, end
+  ldi r25, HIGH((HEAP_SIZE-8) & 0xfffc) ; we allocate multiples of 4 bytes
   clr r16
   sts heapUsed, r16
   sts heapUsed+1, r16
-  st X+, r16                 ; write start header
+  ; write start header (two zero bytes)
   st X+, r16
+  st X+, r16
+  ; X now points to first chunk
   sts heapPtr, xl            ; store global vars
   sts heapPtr+1, xh
   sts heapFree, r24
   sts heapFree+1, r25
-  st X+, r24                 ; store header of first chunk
+  ; store header of first chunk (bit0=0, meaning: free chunk)
+  st X+, r24
   st X+, r25
   add xl, r24
   adc xh, r25
-  st X+, r24                 ; store footer of first chunk
+  ; store footer of first chunk
+  st X+, r24
   st X+, r25
-  st X+, r16                 ; write end footer
+  ; write end header (two zero bytes)
+  st X+, r16
+  st X+, r16
+  ; okay
   sec
   ret
 ; @end
@@ -124,7 +131,7 @@ Heap_AllocAndZero_ret:
 ; @routine heapAllocFirstFit
 ;
 ; @param r25:r24 number of bytes to alloc
-; @return CFLAG set of okay, cleared otherwise
+; @return CFLAG set if okay, cleared otherwise
 ; @return X start of allocated memory
 ; @clobbers r16, r17, r18, r19, r24, r25, X
 
@@ -136,20 +143,24 @@ heapAllocFirstFit:
   lds xh, heapPtr+1
 
 heapAllocFirstFit_loop:
-    ld r18, X+                    ; read chunk header
-    ld r19, X+
-    mov r16, r18                  ; heap end reached?
+    ; read chunk header
+    ld r18, X+
+    ld r19, X+                      ; X now points to first data byte of chunk
+    ; zero-header found?
+    mov r16, r18
     or r16, r19
-    breq heapAllocFirstFit_memFull
+    breq heapAllocFirstFit_memFull  ; yes, memory full
+    ; chunk in use?
     sbrc r18, HEAP_HEADER_BIT_USED
       rjmp heapAllocFirstFit_next ; jump if used
     ; current chunk free, check size
-    andi r18, 0xfc
+    andi r18, 0xfc                ; clear lower two bits
     mov r16, r18
     mov r17, r19
     sub r16, r24
     sbc r17, r25                  ; r17:r16=remainder
     brcs heapAllocFirstFit_next   ; too small
+    ; chunk size is okay, use it
     rcall heapUseChunk
     sec
     ret
@@ -161,12 +172,82 @@ heapAllocFirstFit_next:
   rjmp heapAllocFirstFit_loop  
 
 heapAllocFirstFit_memFull:
+  bigcall Led1_SetFastTiming
   clc
   ret
 ; @end
 
 
 
+; ---------------------------------------------------------------------------
+; @routine heapUseChunk
+;
+; @param r25:r24 wanted size
+; @param r17:r16 size of current chunk minus wanted size (remainder)
+; @param X points to data of current chunk
+; @clobbers 
+
+heapUseChunk:
+  push xl
+    push xh
+      tst r17
+      brne heapUseChunk_split
+      cpi r16, 8                     ; at least 8 bytes left?
+      brcs heapUseChunk_directAlloc  ; nope, use full chunk
+heapUseChunk_split:
+      sbiw xh:xl, 2                  ; go back to chunk header
+      ; X points to start of chunk header
+      mov r18, r24
+      sbr r18, (1<<HEAP_HEADER_BIT_USED)
+      ; write new chunk start header
+      st X+, r18                ; with used bit set
+      st X+, r25                ; X now points to start of chunk data
+      add xl, r24
+      adc xh, r25
+      ; X now points to the start of chunk footer
+      st X+, r18                ; write new chunk footer (with USED bit set)
+      st X+, r25                ; X now points behind chunk end header
+      ; create chunk header for new free chunk
+      subi r16, 4               ; sub chunk header and footer from size
+      sbci r17, 0
+      andi r16, 0xfc            ; clear USED bit
+      ; store new heap pointer
+      sts heapPtr, xl
+      sts heapPtr+1, xh
+      ; write new chunk header
+      st X+, r16                ; write new chunk header (with USED bit cleared)
+      st X+, r17                ; X now points to begin of next chunk data
+      add xl, r16
+      adc xh, r17               ; X now points behind chunk end header
+      st X+, r16                ; write new chunk footer (with USED bit cleared)
+      st X+, r17                ; X points to next chunk header
+      ; update stats, pop X and return
+      rjmp heapUseChunk_statsPopRet
+heapUseChunk_directAlloc:
+      ld r17, -X                          ; load allocated size from chunk header
+      ld r16, -X
+      mov r18, r16
+      sbr r18, (1<<HEAP_HEADER_BIT_USED)  
+      st X, r18                           ; set USED bit in chunk header
+      adiw xh:xl, 2                       ; skip chunk header
+      add xl, r16                         ; skip chunk data
+      adc xh, r17
+      st X, r18                           ; set USED bit in chunk footer
+      adiw xh:xl, 2                       ; X points to next chunk header
+      ; store new heap pointer
+      sts heapPtr, xl
+      sts heapPtr+1, xh
+      ; update stats, pop X and return
+heapUseChunk_statsPopRet:
+      rcall heapAdjustStatsAlloc ; (r16, r17)
+    pop xh
+  pop xl
+  sec
+  ret
+; @end
+
+
+
 ; ---------------------------------------------------------------------------
 ; @routine heapAdjustStatsAlloc
 ;
@@ -225,7 +306,7 @@ heapAdjustStatsFree:
 ; @routine Heap_Free
 ;
 ; @param X pointer to previously allocated data
-; @clobbers r16, r17, r24, r25, X
+; @clobbers r16, r17, r18, r19, r24, r25, X
 
 Heap_Free:
   sbiw xh:xl, 2 ; go back to chunk header
@@ -244,10 +325,10 @@ Heap_Free:
       st X+, r24                        ; write chunk footer
       st X+, r25                        ; X points to the next chunk header now
       rcall heapAdjustStatsFree         ; update stats (r16, r17)
-      rcall heapCoalecseUp              ; try to coalecse following chunk with this (r16, r17, r24, r25, X)
+      rcall heapCoalecseUp              ; try to coalecse following chunk with this (r16, r17, r18, r19, r24, r25, X)
     pop xh
   pop xl
-  rcall heapCoalecseUp                  ; try to coalesce this chunk with predecessor (r16, r17, r24, r25, X)
+  rcall heapCoalecseUp                  ; try to coalesce this chunk with predecessor (r16, r17, r18, r19, r24, r25, X)
   rjmp Heap_Free_ret
 Heap_Free_dblFree:
   lds r24, heapDblFree
@@ -266,119 +347,82 @@ Heap_Free_ret:
 ; ---------------------------------------------------------------------------
 ; @routine heapCoalecseUp
 ;
+; Check whether the given chunk and the previous one are both free.
+; If so combine them into a common free chunk.
+;
 ; @param X pointer to chunk header
-; @clobbers r16, r17, r24, r25, X
+; @clobbers r16, r17, r18, r19, r24, r25, X
 
 heapCoalecseUp:
-  ld r16, X+                    ; end of heap reached(header==0x0000)?
-  ld r17, X
-  sbiw xh:xl, 1
-  or r16, r17
-  breq heapCoalecseUp_ret        ; yes, jump
-  ; read footer of preceeding chunk 
-  ld r25, -X
-  ld r24, -X
-  ; R25:R24=footer of preceeding chunk (i.e. size of previous chunk), X points to previous footer
-  mov r16, r24                   ; check: beginning of heap reached (header==0x0000)?
+  ; read current chunk header
+  ld r24, X+
+  ld r25, X
+  sbiw xh:xl, 3
+  ; read previous chunk footer
+  ld r18, X+
+  ld r19, X+
+  ; current chunk=end_of_heap?
+  mov r16, r24
   or r16, r25
-  breq heapCoalecseUp_ret        ; yes, jump
-  sbrc r24, HEAP_HEADER_BIT_USED ; block used?
-    rjmp heapCoalecseUp_ret      ; jump if used
-  ; previous chunk also free, coalesce, X points to current chunk header
-  adiw xh:xl, 2
-; skip footer
-  ld r16, X+
-  ld r17, X+
- sbrc r16, HEAP_HEADER_BIT_USED ; current block used?
-    rjmp heapCoalecseUp_ret      ; jump if used
- 
-  ; X now points to beginning of current chunk's data, R17:r16=size of current chunk, R25:R24=size of previous chunk
-  ; to go to start of previous chunk header: sub this chunk header, previous chunk footer, previous chunk header and previous data
-  sbiw xh:xl, 6
-  sub xl, r24
-  sbc xh, r25
-  ; X points now to the beginning of the previous chunk header
-  ; calculate size of new coalecsed chunk: add size of this chunk, size of previous chunk, 1 chunk header and 1 footer which are
-  ; no longer needed now (since the one header and footer of the previous chunk now cover both chunks)
+  breq heapCoalecseUp_done
+  ; current chunk in use?
+  sbrc r24, HEAP_HEADER_BIT_USED
+    rjmp heapCoalecseUp_done
+  ; previous chunk=begin of heap?
+  mov r16, r18
+  or r16, r19
+  breq heapCoalecseUp_done
+  ; previous chunk in use?
+  sbrc r18, HEAP_HEADER_BIT_USED
+    rjmp heapCoalecseUp_done
+  
+  ; clear lower two bits
+  andi r18, 0xfc
+  andi r24, 0xfc
+  
+  ; now:
+  ; - both chunks are free and can be combined
+  ; - X points to beginning of current header
+
+  ; calc combined size (sizes of both chunks plus 1 header and 1 footer)
+  add r24, r18
+  adc r25, r19
+  ldi r16, 4
+  clr r17
   add r24, r16
-  adc r25, r17
-  adiw r25:r24, 4
-  ; write new chunk header
+  adc r25, r17  ; r25:r24=combined size
+
+  ; check for heapPtr
+  lds r16, heapPtr
+  lds r17, heapPtr+1
+  sub r16, xl
+  sbc r17, xh
+  or r16, r17    ; r16=0 if heapPtr=current chunk
+
+  sbiw xh:xl, 4  ; subtract previous footer and header from pos
+  sub xl, r18    ; subtract size of previous chunk from pos
+  sbc xh, r19    ; X now points to beginning of previous chunk
+  
+  ; test heapPtr
+  tst r16
+  brne heapCoalecseUp_l1
+  ; adjust heapPtr
+  sts heapPtr, xl
+  sts heapPtr+1, xh
+heapCoalecseUp_l1:
+  ; write new combined header
   st X+, r24
   st X+, r25
-  ; skip full data size of the coalesced chunk
   add xl, r24
   adc xh, r25
-  ; write new chunk footer
+  ; write new combined footer
   st X+, r24
   st X+, r25
-  ; X now points to header of following chunk
-heapCoalecseUp_ret:
+heapCoalecseUp_done:
   ret
 ; @end
 
-
-
-; ---------------------------------------------------------------------------
-; @routine heapUseChunk
-;
-; @param r25:r24 wanted size
-; @param r17:r16 size of current chunk minus wanted size (remainder)
-; @param X points to data of current chunk
-; @clobbers 
-
-heapUseChunk:
-  push xl
-    push xh
-      tst r17
-      brne heapUseChunk_split
-      cpi r16, 8                     ; at least 8 bytes left?
-      brcs heapUseChunk_directAlloc  ; nope, use full chunk
-heapUseChunk_split:
-      sbiw xh:xl, 2             ; go back to chunk header
-      ; X points to start of chunk header
-      mov r18, r24
-      sbr r18, (1<<HEAP_HEADER_BIT_USED)
-      st X+, r18                ; set used bit
-      st X+, r25
-      add xl, r24
-      adc xh, r25
-      ; X now points to the start of chunk footer
-      st X+, r18
-      st X+, r25
-      ; create chunk header for new free chunk
-      subi r16, 4               ; sub chunk header and footer from size
-      sbci r17, 0
-      andi r16, 0xfc            ; clear USED bit
-      st X+, r16                ; write new chunk header
-      st X+, r17
-      add xl, r16
-      adc xh, r17
-      st X+, r16                ; write new chunk footer
-      st X+, r17
-      ; update stats, pop X and return
-      rjmp heapUseChunk_statsPopRet
-heapUseChunk_directAlloc:
-      ld r17, -X                          ; load allocated size from chunk header
-      ld r16, -X
-      mov r18, r16
-      sbr r18, (1<<HEAP_HEADER_BIT_USED)  
-      st X, r18                           ; set USED bit in chunk header
-      adiw xh:xl, 2                       ; skip chunk header
-      add xl, r16                         ; skip chunk data
-      adc xh, r17
-      st X, r18                           ; set USED bit in chunk footer
-      ; update stats, pop X and return
-heapUseChunk_statsPopRet:
-      rcall heapAdjustStatsAlloc ; (r16, r17)
-    pop xh
-  pop xl
-  sec
-  ret
-; @end
-
-
-
+  
 
 
 
diff --git a/avr/modules/lcd2/gui/base/layout.asm b/avr/modules/lcd2/gui/base/layout.asm
index 0137209..c5878d3 100644
--- a/avr/modules/lcd2/gui/base/layout.asm
+++ b/avr/modules/lcd2/gui/base/layout.asm
@@ -120,10 +120,10 @@ LayoutCtx_new_ret:
 ; @routine LayoutCtx_free @global
 ;
 ; @param X pointer to layout context
-; @clobbers r16, r17, r24, r25, X
+; @clobbers r16, r17, r18, r19, r24, r25, X
 
 LayoutCtx_free:
-  bigjmp Heap_Free   ; (r16, r17, r24, r25, X)
+  bigjmp Heap_Free   ; (r16, r17, r18, r19, r24, r25, X)
 ; @end