1 files changed, 120 insertions, 0 deletions
diff --git a/site/udo/twigs/checkpointing.udo b/site/udo/twigs/checkpointing.udo
new file mode 100755
index 0000000..bd2594e
--- /dev/null
+++ b/site/udo/twigs/checkpointing.udo
@@ -0,0 +1,120 @@
+#ifndef UDO_TWIGS_CHECKPOINTING
+#define UDO_TWIGS_CHECKPOINTING ##
+
+gitwgs_maxundolevels = 32
+gitwgs_checkpoints[] init gitwgs_maxundolevels
+gitwgs_checkpointstate = 0
+gitwgs_checkpointencodemult = 10000
+
+
+opcode twgs_checkpoint_encode, i, ii
+	ifnL, ifnR xin
+	iencoded = (ifnL * gitwgs_checkpointencodemult) + (ifnR / gitwgs_checkpointencodemult)
+	xout iencoded
+endop
+
+opcode twgs_checkpoint_decode, ii, i
+	iencoded xin
+	ifnL = int(iencoded) / gitwgs_checkpointencodemult
+	ifnR = frac(iencoded) * gitwgs_checkpointencodemult
+	xout ifnL, ifnR
+endop
+
+opcode twgs_checkpoint_clear, 0, 0
+	icheckpointnumber = gitwgs_checkpointstate
+	while (icheckpointnumber >= 0) do
+		ifnL, ifnR twgs_checkpoint_decode gitwgs_checkpoints[icheckpointnumber]
+		if (ifnL > 0 && ftexists(ifnL) == 1) then
+			tpvf_destroy ifnL
+		endif
+		if (ifnR > 0  && ftexists(ifnR) == 1) then
+			tpvf_destroy ifnR
+		endif
+		icheckpointnumber -= 1
+	od
+	gitwgs_checkpointstate = 0
+endop
+
+opcode twgs_checkpoint, 0, 0
+	imaxundo chnget "twgs_maxundo"
+	imaxundo = (imaxundo == -1) ? gitwgs_maxundolevels : imaxundo
+	if (imaxundo == 0 || imaxundo > gitwgs_maxundolevels) then
+		goto complete
+	endif
+
+	icheckpointnumber = gitwgs_checkpointstate
+	if (icheckpointnumber >= imaxundo) then
+		ifnL, ifnR twgs_checkpoint_decode gitwgs_checkpoints[0]
+		if (ifnL > 0 && ftexists(ifnL) == 1) then
+			tpvf_destroy ifnL
+		endif
+		if (ifnR > 0 && ftexists(ifnR) == 1) then
+			tpvf_destroy ifnR
+		endif
+		index = 1
+		itemp[] = gitwgs_checkpoints
+		while (index <= imaxundo) do
+			gitwgs_checkpoints[index - 1] = itemp[index]
+			index += 1
+		od
+		gitwgs_checkpointstate = icheckpointnumber ;- 1
+	else
+		gitwgs_checkpointstate = icheckpointnumber + 1
+	endif
+	
+	ifnL = gitwgs_tpvfHandleL
+	ifnR = gitwgs_tpvfHandleR
+	
+	ifnCheckpointL tpvf_clone ifnL
+print ifnCheckpointL
+	if (ifnR > 0) then
+		ifnCheckpointR tpvf_clone ifnR
+	else
+		ifnCheckpointR = 0
+	endif
+	
+	iencoded twgs_checkpoint_encode ifnCheckpointL, ifnCheckpointR
+	gitwgs_checkpoints[icheckpointnumber] = iencoded
+	
+complete:
+endop
+
+opcode twgs_undo, i, p
+	iapplyundo xin
+
+	icheckpointnumber = gitwgs_checkpointstate
+
+	icheckpointnumber -= 1
+	if (icheckpointnumber < 0) then
+		istatus = -1
+		goto complete
+	endif
+
+	gitwgs_checkpointstate = icheckpointnumber
+	ifnL, ifnR twgs_checkpoint_decode gitwgs_checkpoints[icheckpointnumber]
+
+	if (iapplyundo == 1) then ; apply or just step back and forget
+		if (ifnL > 0 && ftexists(ifnL) = 1) then
+			tpvf_destroy gitwgs_tpvfHandleL
+			gitwgs_tpvfHandleL = ifnL
+		endif
+		if (ifnR > 0 && ftexists(ifnR) == 1) then
+			tpvf_destroy gitwgs_tpvfHandleR
+			gitwgs_tpvfHandleR = ifnR
+		endif
+	else
+		if (ifnL > 0 && ftexists(ifnL) = 1) then
+			tpvf_destroy ifnL
+		endif
+		if (ifnL > 0 && ftexists(ifnR) = 1) then
+			tpvf_destroy ifnR
+		endif
+	endif
+
+	istatus = 1
+	
+complete:
+	xout istatus
+endop
+
+#end