Flag unrecognised critical tags, but allow ancilliary tags between IDAT and IEND

PNG spec 1.2, section 4.3, turns out tIME iTXt tEXt zTXt have no ordering constraints. Images with these after the IDATs but before IEND were being rejected, plus it's possible to encounter private ancilliary chunks - so it's safest just to let them all through.
Unexpected critical chunks are now explicitly faulted.

Version 1.46. Tagged as 'ChangeFSI-1_46'

VersionNum

-/* (1.45)
+/* (1.46)
  *
  * This file is automatically maintained by srccommit, do not edit manually.
  * Last processed by srccommit version: 1.1.
  *
  */
-#define Module_MajorVersion_CMHG        1.45
+#define Module_MajorVersion_CMHG        1.46
 #define Module_MinorVersion_CMHG        
-#define Module_Date_CMHG                11 Jan 2014
+#define Module_Date_CMHG                15 Jan 2014
 
-#define Module_MajorVersion             "1.45"
-#define Module_Version                  145
+#define Module_MajorVersion             "1.46"
+#define Module_Version                  146
 #define Module_MinorVersion             ""
-#define Module_Date                     "11 Jan 2014"
+#define Module_Date                     "15 Jan 2014"
 
-#define Module_ApplicationDate          "11-Jan-14"
+#define Module_ApplicationDate          "15-Jan-14"
 
 #define Module_ComponentName            "ChangeFSI"
 #define Module_ComponentPath            "mixed/RiscOS/Sources/Apps/ChangeFSI"
 
-#define Module_FullVersion              "1.45"
-#define Module_HelpVersion              "1.45 (11 Jan 2014)"
-#define Module_LibraryVersionInfo       "1:45"
+#define Module_FullVersion              "1.46"
+#define Module_HelpVersion              "1.46 (15 Jan 2014)"
+#define Module_LibraryVersionInfo       "1:46"

source/CFSI-PNG

@@ -585,7 +585,7 @@ load_row ROUT
         ; Exit
         ; r0 = V set and error else
         ;      buffer refilled
-        Push    "r0-r6, r8, lr"
+        Push    "r0-r5, r8, lr"
 
         TEQ     r0, #0
         MOVEQ   r0, #2_00010            ; First call
@@ -606,12 +606,11 @@ load_row ROUT
         STMIA   r7, { r2-r3, r5 }
 
         CMP     r0, #DECOMPRESS_NEED_INPUT
-        Pull    "r0-r6, r8, pc", NE     ; Complete
+        Pull    "r0-r5, r8, pc", NE     ; Complete
         
         ; Need to load some more from the file
         LDR     r5, [r7, #Wsp_FileBuf]
         STR     r5, [r7, #Wsp_InBuf]    ; Reset input buffer pointer to empty
-        LDR     r6, [sp, #3*4]          ; Keep handle handy
 20
         SUBS    r3, r3, #1              ; Re-present trailing bytes
         LDRPLB  r1, [r2], #1
@@ -631,7 +630,7 @@ load_row ROUT
         MOVCS   r8, r1                  ; Limit read to data available
 
         MOV     r0, #OSGBPB_ReadFromGiven
-        MOV     r1, r6
+        LDR     r1, [sp, #3*4]
         MOV     r2, r5
         MOV     r3, r8
         LDR     r4, [r7, #Wsp_FileOffset]
@@ -650,9 +649,9 @@ load_row ROUT
         STR     r4, [r7, #Wsp_FileOffset]
 50
         ; Hunt for the next IDAT
-        SUB     sp, sp, #8
         MOV     r0, #OSGBPB_ReadFromGiven
-        MOV     r1, r6
+        LDR     r1, [sp, #3*4]
+        SUB     sp, sp, #8
         MOV     r2, sp
         MOV     r3, #8
         LDR     r4, [r7, #Wsp_FileOffset]
@@ -660,24 +659,33 @@ load_row ROUT
         BVS     %FT60
 
         LDMIA   sp!, { r2-r3 }          ; r2 = BE length, r3 = tag
+
+        MOV     r14, #&FF000000
+        ORR     r14, r14, #&FF00
+        AND     r0, r14, r2, ROR #8     ; ABCD -> DABC -> D.B.
+        AND     r2, r14, r2             ; ABCD         -> A.C.
+        ORR     r2, r0, r2, ROR #24     ;              -> DCBA endian swapped
+
         LDR     r0, load_idat
         TEQ     r3, r0
         BEQ     %FT70
+
         LDR     r0, load_iend
         TEQ     r3, r0
         BEQ     %FT80
+
+        TST     r3, #1:SHL:5            ; Skip ancilliary tags
+        ADDNE   r4, r4, r2
+        BNE     %BT40
+
         ADR     r0, load_duff_err
         SETV
 60
         ADD     sp, sp, #4
-        Pull    "r1-r6, r8, pc"         ; Fatal
+        Pull    "r1-r5, r8, pc"         ; Fatal
 70
         ; It's an IDAT
-        MOV     r3, #&FF000000
-        ORR     r3, r3, #&FF00
-        AND     r0, r3, r2, ROR #8      ; ABCD -> DABC -> D.B.
-        AND     r2, r3, r2              ; ABCD         -> A.C.
-        ORRS    r2, r0, r2, ROR #24     ;              -> DCBA endian swapped
+        TEQ     r2, #0
         BEQ     %BT40                   ; Skip CRC32 after empty IDAT
 
         STR     r2, [r7, #Wsp_FileRem]
@@ -701,7 +709,7 @@ load_iend
         DCB     "IEND"
 load_duff_err
         DCD     42
-        DCB     "Non data tag between IDAT and IEND", 0
+        DCB     "Unrecognised critical tag between IDAT and IEND", 0
         ALIGN
 
 zlib_decompress ROUT

source/ChangeFSI

@@ -4117,7 +4117,8 @@ DEF FNChangeFSI(A$,spritearea%,workspace%,worklimit%,oksave%,okinfo%,RETURN ram%
             IF L%<>0 THEN ERROR42, "IEND contains data"
             C%=FNbeW:REM Skip CRC32
           OTHERWISE
-            PTR#c%=PTR#c%+L%+4:REM Skip unhandled tags
+            IF (ASC(t$) AND32)=0 THEN ERROR42, "Unhandled critical tag encountered":REM Not one in PNG spec 1.2
+            PTR#c%=PTR#c%+L%+4:REM Skip unhandled ancilliary tags
         ENDCASE
       UNTIL EOF#c%
       IF NOT V% THEN ERROR42,"Out of order tag in PNG"