From 649ae829220d6ddd8758d24c3bc2ea7d43e788d6 Mon Sep 17 00:00:00 2001
From: Antonio Navarro Perez <antnavper@gmail.com>
Date: Wed, 20 Mar 2024 11:15:48 +0100
Subject: feat: Add simple Dump creation and recovery.

Memory Dump functionality that can restore the previous VM state.

It dumps *global* variables, the only ones defining the program state.

The dump depends on the program itself, and on the index system, which right now is defined by the variable order.

Signed-off-by: Antonio Navarro Perez <antnavper@gmail.com>
---
 parser/compiler.go | 93 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 90 insertions(+), 3 deletions(-)

(limited to 'parser/compiler.go')

diff --git a/parser/compiler.go b/parser/compiler.go
index 4594ab9..568ed4a 100644
--- a/parser/compiler.go
+++ b/parser/compiler.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"reflect"
 	"strconv"
 
 	"github.com/mvertes/parscan/lang"
@@ -328,18 +329,104 @@ type entry struct {
 	*symbol
 }
 
+func (e entry) String() string {
+	if e.symbol != nil {
+		return fmt.Sprintf("name: %s,local: %t, i: %d, k: %d, t: %s, v: %v",
+			e.name,
+			e.symbol.local,
+			e.symbol.index,
+			e.symbol.kind,
+			e.symbol.Type,
+			e.symbol.value,
+		)
+	}
+
+	return e.name
+}
+
 func (c *Compiler) PrintData() {
+	dict := c.symbolsByIndex()
+
+	fmt.Fprintln(os.Stderr, "# Data:")
+	for i, d := range c.Data {
+		fmt.Fprintf(os.Stderr, "%4d %T %v %v\n", i, d.Data.Interface(), d.Data, dict[i])
+	}
+}
+
+func (c *Compiler) symbolsByIndex() map[int]entry {
 	dict := map[int]entry{}
 	for name, sym := range c.symbols {
-		if !sym.used || sym.local || sym.kind == symLabel {
+		if sym.index == unsetAddr {
 			continue
 		}
 		dict[sym.index] = entry{name, sym}
 	}
-	fmt.Fprintln(os.Stderr, "# Data:")
+
+	return dict
+}
+
+type Dump struct {
+	Values []*DumpValue
+}
+
+type DumpValue struct {
+	Index int
+	Name  string
+	Kind  int
+	Type  string
+	Value any
+}
+
+// Dump gets the execution state of global variables.
+func (c *Compiler) Dump() *Dump {
+	var dv []*DumpValue
+	dict := c.symbolsByIndex()
 	for i, d := range c.Data {
-		fmt.Fprintf(os.Stderr, "%4d %T %v %v\n", i, d.Data.Interface(), d.Data, dict[i])
+		e := dict[i]
+		dv = append(dv, &DumpValue{
+			Index: e.index,
+			Name:  e.name,
+			Kind:  int(e.kind),
+			Type:  e.Type.Name,
+			Value: d.Data.Interface(),
+		})
 	}
+
+	return &Dump{Values: dv}
+}
+
+// ApplyDump sets previously saved dump, restoring the state of global variables.
+func (c *Compiler) ApplyDump(d *Dump) error {
+	dict := c.symbolsByIndex()
+	for _, dv := range d.Values {
+		// do all the checks to be sure we are applying the correct values
+		e, ok := dict[dv.Index]
+		if !ok {
+			return fmt.Errorf("entry not found on index %d", dv.Index)
+		}
+
+		if dv.Name != e.name ||
+			dv.Type != e.Type.Name ||
+			dv.Kind != int(e.kind) {
+			return fmt.Errorf("entry with index %d does not match with provided entry. "+
+				"dumpValue: %s, %s, %d. memoryValue: %s, %s, %d",
+				dv.Index,
+				dv.Name, dv.Type, dv.Kind,
+				e.name, e.Type, e.kind)
+		}
+
+		if dv.Index >= len(c.Data) {
+			return fmt.Errorf("index (%d) bigger than memory (%d)", dv.Index, len(c.Data))
+		}
+
+		if !c.Data[dv.Index].Data.CanSet() {
+			return fmt.Errorf("value %v cannot be set", dv.Value)
+		}
+
+		c.Data[dv.Index].Data.Set(reflect.ValueOf(dv.Value))
+	}
+
+	return nil
 }
 
 func (c *Compiler) typeSym(t *vm.Type) *symbol {
-- 
cgit v1.2.3


From 7a9ac73037f207e3895332e5ba2b30d465c9c339 Mon Sep 17 00:00:00 2001
From: Antonio Navarro Perez <antnavper@gmail.com>
Date: Thu, 21 Mar 2024 15:46:33 +0100
Subject: Add extra GoDoc to explain why Dump is on the Compiler.

Signed-off-by: Antonio Navarro Perez <antnavper@gmail.com>
---
 parser/compiler.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

(limited to 'parser/compiler.go')

diff --git a/parser/compiler.go b/parser/compiler.go
index 568ed4a..fb79720 100644
--- a/parser/compiler.go
+++ b/parser/compiler.go
@@ -377,7 +377,13 @@ type DumpValue struct {
 	Value any
 }
 
-// Dump gets the execution state of global variables.
+// Dump creates a snapshot of the execution state of global variables.
+// This method is specifically implemented in the Compiler to minimize the coupling between
+// the dump format and other components. By situating the dump logic in the Compiler,
+// it relies solely on the program being executed and the indexing algorithm used for ordering variables
+// (currently, this is an integer that corresponds to the order of variables in the program).
+// This design choice allows the Virtual Machine (VM) to evolve its memory management strategies
+// without compromising backward compatibility with dumps generated by previous versions.
 func (c *Compiler) Dump() *Dump {
 	var dv []*DumpValue
 	dict := c.symbolsByIndex()
-- 
cgit v1.2.3