proc/variables: map types support

Use m[n:] to skip the first n keys of a map
Map indexing is implemented with a linear scan

Implements #61, #122

_fixtures/testvariables3.go

@@ -45,11 +45,57 @@ func main() {
 	var nilptr *int = nil
 	ch1 := make(chan int, 2)
 	var chnil chan int = nil
+	m1 := map[string]astruct{
+		"Malone":          astruct{2, 3},
+		"Adenauer":        astruct{},
+		"squadrons":       astruct{},
+		"quintuplets":     astruct{},
+		"parasite":        astruct{},
+		"wristwatches":    astruct{},
+		"flashgun":        astruct{},
+		"equivocally":     astruct{},
+		"sweetbrier":      astruct{},
+		"idealism":        astruct{},
+		"tangos":          astruct{},
+		"alterable":       astruct{},
+		"quaffing":        astruct{},
+		"arsenic":         astruct{},
+		"coincidentally":  astruct{},
+		"hindrances":      astruct{},
+		"zoning":          astruct{},
+		"egging":          astruct{},
+		"inserts":         astruct{},
+		"adaptive":        astruct{},
+		"orientations":    astruct{},
+		"periling":        astruct{},
+		"lip":             astruct{},
+		"chant":           astruct{},
+		"availing":        astruct{},
+		"fern":            astruct{},
+		"flummoxes":       astruct{},
+		"meanders":        astruct{},
+		"ravenously":      astruct{},
+		"reminisce":       astruct{},
+		"snorkel":         astruct{},
+		"gutters":         astruct{},
+		"jibbed":          astruct{},
+		"tiara":           astruct{},
+		"takers":          astruct{},
+		"animates":        astruct{},
+		"Zubenelgenubi":   astruct{},
+		"bantering":       astruct{},
+		"tumblers":        astruct{},
+		"horticulturists": astruct{},
+		"thallium":        astruct{},
+	}
+	var mnil map[string]astruct = nil
+	m2 := map[int]*astruct{1: &astruct{10, 11}}
+	m3 := map[astruct]int{{1, 1}: 42, {2, 2}: 43}
 
 	var amb1 = 1
 	runtime.Breakpoint()
 	for amb1 := 0; amb1 < 10; amb1++ {
 		fmt.Println(amb1)
 	}
-	fmt.Println(i1, i2, i3, p1, amb1, s1, a1, p2, p3, s2, as1, str1, f1, fn1, fn2, nilslice, nilptr, ch1, chnil)
+	fmt.Println(i1, i2, i3, p1, amb1, s1, a1, p2, p3, s2, as1, str1, f1, fn1, fn2, nilslice, nilptr, ch1, chnil, m1, mnil, m2, m3)
 }

proc/eval.go

@@ -250,9 +250,6 @@ func (scope *EvalScope) evalIndex(node *ast.IndexExpr) (*Variable, error) {
 	if xev.Unreadable != nil {
 		return nil, xev.Unreadable
 	}
-	if xev.base == 0 {
-		return nil, fmt.Errorf("can not index \"%s\"", exprToString(node.X))
-	}
 
 	idxev, err := scope.evalAST(node.Index)
 	if err != nil {
@@ -261,6 +258,9 @@ func (scope *EvalScope) evalIndex(node *ast.IndexExpr) (*Variable, error) {
 
 	switch xev.Kind {
 	case reflect.Slice, reflect.Array, reflect.String:
+		if xev.base == 0 {
+			return nil, fmt.Errorf("can not index \"%s\"", exprToString(node.X))
+		}
 		n, err := idxev.asInt()
 		if err != nil {
 			return nil, err
@@ -268,7 +268,11 @@ func (scope *EvalScope) evalIndex(node *ast.IndexExpr) (*Variable, error) {
 		return xev.sliceAccess(int(n))
 
 	case reflect.Map:
-		return nil, fmt.Errorf("map access not implemented")
+		idxev.loadValue()
+		if idxev.Unreadable != nil {
+			return nil, idxev.Unreadable
+		}
+		return xev.mapAccess(idxev)
 	default:
 		return nil, fmt.Errorf("invalid expression \"%s\" (type %s does not support indexing)", exprToString(node.X), xev.DwarfType.String())
 
@@ -285,16 +289,6 @@ func (scope *EvalScope) evalReslice(node *ast.SliceExpr) (*Variable, error) {
 	if xev.Unreadable != nil {
 		return nil, xev.Unreadable
 	}
-	if xev.base == 0 {
-		return nil, fmt.Errorf("can not slice \"%s\"", exprToString(node.X))
-	}
-
-	switch xev.Kind {
-	case reflect.Slice, reflect.Array, reflect.String:
-		//ok
-	default:
-		return nil, fmt.Errorf("cannot slice \"%s\" (type %s)", exprToString(node.X), xev.DwarfType.String())
-	}
 
 	var low, high int64
 
@@ -322,8 +316,21 @@ func (scope *EvalScope) evalReslice(node *ast.SliceExpr) (*Variable, error) {
 		}
 	}
 
-	r, err := xev.reslice(low, high)
-	return r, err
+	switch xev.Kind {
+	case reflect.Slice, reflect.Array, reflect.String:
+		if xev.base == 0 {
+			return nil, fmt.Errorf("can not slice \"%s\"", exprToString(node.X))
+		}
+		return xev.reslice(low, high)
+	case reflect.Map:
+		if node.High != nil {
+			return nil, fmt.Errorf("second slice argument must be empty for maps")
+		}
+		xev.mapSkip += int(low)
+		return xev, nil
+	default:
+		return nil, fmt.Errorf("can not slice \"%s\" (type %s)", exprToString(node.X), xev.DwarfType.String())
+	}
 }
 
 // Evaluates a pointer dereference expression: *<subexpr>
@@ -654,6 +661,24 @@ func (v *Variable) asInt() (int64, error) {
 	return n, nil
 }
 
+func (v *Variable) asUint() (uint64, error) {
+	if v.DwarfType == nil {
+		if v.Value.Kind() != constant.Int {
+			return 0, fmt.Errorf("can not convert constant %s to uint", v.Value)
+		}
+	} else {
+		v.loadValue()
+		if v.Unreadable != nil {
+			return 0, v.Unreadable
+		}
+		if _, ok := v.DwarfType.(*dwarf.UintType); !ok {
+			return 0, fmt.Errorf("can not convert value of type %s to uint", v.DwarfType.String())
+		}
+	}
+	n, _ := constant.Uint64Val(v.Value)
+	return n, nil
+}
+
 func (v *Variable) isType(typ dwarf.Type, kind reflect.Kind) error {
 	if v.DwarfType != nil {
 		if typ != nil && typ.String() != v.RealType.String() {
@@ -723,6 +748,40 @@ func (v *Variable) sliceAccess(idx int) (*Variable, error) {
 	return newVariable("", v.base+uintptr(int64(idx)*v.stride), v.fieldType, v.thread), nil
 }
 
+func (v *Variable) mapAccess(idx *Variable) (*Variable, error) {
+	it := v.mapIterator()
+	if it == nil {
+		return nil, fmt.Errorf("can not access unreadable map: %v", v.Unreadable)
+	}
+
+	first := true
+	for it.next() {
+		key := it.key()
+		key.loadValue()
+		if key.Unreadable != nil {
+			return nil, fmt.Errorf("can not access unreadable map: %v", key.Unreadable)
+		}
+		if first {
+			first = false
+			if err := idx.isType(key.DwarfType, key.Kind); err != nil {
+				return nil, err
+			}
+		}
+		eql, err := compareOp(token.EQL, key, idx)
+		if err != nil {
+			return nil, err
+		}
+		if eql {
+			return it.value(), nil
+		}
+	}
+	if v.Unreadable != nil {
+		return nil, v.Unreadable
+	}
+	// go would return zero for the map value type here, we do not have the ability to create zeroes
+	return nil, fmt.Errorf("key not found")
+}
+
 func (v *Variable) reslice(low int64, high int64) (*Variable, error) {
 	if low < 0 || low >= v.Len || high < 0 || high > v.Len {
 		return nil, fmt.Errorf("index out of bounds")

proc/variables.go

@@ -23,6 +23,9 @@ const (
 
 	ChanRecv = "chan receive"
 	ChanSend = "chan send"
+
+	hashTophashEmpty = 0 // used by map reading code, indicates an empty bucket
+	hashMinTopHash   = 4 // used by map reading code, indicates minimum value of tophash that isn't empty or evacuated
 )
 
 // Represents a variable.
@@ -42,12 +45,15 @@ type Variable struct {
 
 	// base address of arrays, base address of the backing array for slices (0 for nil slices)
 	// base address of the backing byte array for strings
-	// address of the struct backing a chan variable
+	// address of the struct backing chan and map variables
 	// address of the function entry point for function variables (0 for nil function pointers)
 	base      uintptr
 	stride    int64
 	fieldType dwarf.Type
 
+	// number of elements to skip when loading a map
+	mapSkip int
+
 	Children []Variable
 
 	loaded     bool
@@ -126,6 +132,8 @@ func newVariable(name string, addr uintptr, dwarfType dwarf.Type, thread *Thread
 		structtyp, isstruct := t.Type.(*dwarf.StructType)
 		if isstruct && strings.HasPrefix(structtyp.StructName, "hchan<") {
 			v.Kind = reflect.Chan
+		} else if isstruct && strings.HasPrefix(structtyp.StructName, "hash<") {
+			v.Kind = reflect.Map
 		} else {
 			v.Kind = reflect.Ptr
 		}
@@ -716,6 +724,9 @@ func (v *Variable) loadValueInternal(recurseLevel int) {
 		v.Len = sv.Len
 		v.base = sv.Addr
 
+	case reflect.Map:
+		v.loadMap(recurseLevel)
+
 	case reflect.String:
 		var val string
 		val, v.Unreadable = v.thread.readStringValue(v.base, v.Len)
@@ -762,8 +773,6 @@ func (v *Variable) loadValueInternal(recurseLevel int) {
 		v.Value = constant.MakeFloat64(val)
 	case reflect.Func:
 		v.readFunctionPtr()
-	case reflect.Map:
-		fallthrough
 	default:
 		v.Unreadable = fmt.Errorf("unknown or unsupported kind: \"%s\"", v.Kind.String())
 	}
@@ -1093,6 +1102,249 @@ func (v *Variable) readFunctionPtr() {
 	v.Value = constant.MakeString(fn.Name)
 }
 
+func (v *Variable) loadMap(recurseLevel int) {
+	it := v.mapIterator()
+	if it == nil {
+		return
+	}
+
+	for skip := 0; skip < v.mapSkip; skip++ {
+		if ok := it.next(); !ok {
+			return
+		}
+	}
+
+	count := 0
+	errcount := 0
+	for it.next() {
+		if count >= maxArrayValues {
+			break
+		}
+		key := it.key()
+		val := it.value()
+		key.loadValue()
+		val.loadValue()
+		if key.Unreadable != nil || val.Unreadable != nil {
+			errcount++
+		}
+		v.Children = append(v.Children, *key)
+		v.Children = append(v.Children, *val)
+		count++
+		if errcount > maxErrCount {
+			break
+		}
+	}
+}
+
+type mapIterator struct {
+	v          *Variable
+	numbuckets uint64
+	oldmask    uint64
+	buckets    *Variable
+	oldbuckets *Variable
+	b          *Variable
+	bidx       uint64
+
+	tophashes *Variable
+	keys      *Variable
+	values    *Variable
+	overflow  *Variable
+
+	idx int64
+}
+
+// Code derived from go/src/runtime/hashmap.go
+func (v *Variable) mapIterator() *mapIterator {
+	sv := v.maybeDereference()
+	v.base = sv.Addr
+
+	maptype, ok := sv.RealType.(*dwarf.StructType)
+	if !ok {
+		v.Unreadable = fmt.Errorf("wrong real type for map")
+		return nil
+	}
+
+	it := &mapIterator{v: v, bidx: 0, b: nil, idx: 0}
+
+	if sv.Addr == 0 {
+		it.numbuckets = 0
+		return it
+	}
+
+	for _, f := range maptype.Field {
+		var err error
+		field, _ := sv.toField(f)
+		switch f.Name {
+		case "count":
+			v.Len, err = field.asInt()
+		case "B":
+			var b uint64
+			b, err = field.asUint()
+			it.numbuckets = 1 << b
+			it.oldmask = (1 << (b - 1)) - 1
+		case "buckets":
+			it.buckets = field.maybeDereference()
+		case "oldbuckets":
+			it.oldbuckets = field.maybeDereference()
+		}
+		if err != nil {
+			v.Unreadable = err
+			return nil
+		}
+	}
+
+	return it
+}
+
+func (it *mapIterator) nextBucket() bool {
+	if it.overflow != nil && it.overflow.Addr > 0 {
+		it.b = it.overflow
+	} else {
+		it.b = nil
+
+		for it.bidx < it.numbuckets {
+			it.b = it.buckets.clone()
+			it.b.Addr += uintptr(uint64(it.buckets.DwarfType.Size()) * it.bidx)
+
+			if it.oldbuckets.Addr <= 0 {
+				break
+			}
+
+			// if oldbuckets is not nil we are iterating through a map that is in
+			// the middle of a grow.
+			// if the bucket we are looking at hasn't been filled in we iterate
+			// instead through its corresponding "oldbucket" (i.e. the bucket the
+			// elements of this bucket are coming from) but only if this is the first
+			// of the two buckets being created from the same oldbucket (otherwise we
+			// would print some keys twice)
+
+			oldbidx := it.bidx & it.oldmask
+			oldb := it.oldbuckets.clone()
+			oldb.Addr += uintptr(uint64(it.oldbuckets.DwarfType.Size()) * oldbidx)
+
+			if mapEvacuated(oldb) {
+				break
+			}
+
+			if oldbidx == it.bidx {
+				it.b = oldb
+				break
+			}
+
+			// oldbucket origin for current bucket has not been evacuated but we have already
+			// iterated over it so we should just skip it
+			it.b = nil
+			it.bidx++
+		}
+
+		if it.b == nil {
+			return false
+		}
+		it.bidx++
+	}
+
+	if it.b.Addr <= 0 {
+		return false
+	}
+
+	it.tophashes = nil
+	it.keys = nil
+	it.values = nil
+	it.overflow = nil
+
+	for _, f := range it.b.DwarfType.(*dwarf.StructType).Field {
+		field, err := it.b.toField(f)
+		if err != nil {
+			it.v.Unreadable = err
+			return false
+		}
+		if field.Unreadable != nil {
+			it.v.Unreadable = field.Unreadable
+			return false
+		}
+
+		switch f.Name {
+		case "tophash":
+			it.tophashes = field
+		case "keys":
+			it.keys = field
+		case "values":
+			it.values = field
+		case "overflow":
+			it.overflow = field.maybeDereference()
+		}
+	}
+
+	// sanity checks
+	if it.tophashes == nil || it.keys == nil || it.values == nil {
+		it.v.Unreadable = fmt.Errorf("malformed map type")
+		return false
+	}
+
+	if it.tophashes.Kind != reflect.Array || it.keys.Kind != reflect.Array || it.values.Kind != reflect.Array {
+		it.v.Unreadable = fmt.Errorf("malformed map type: keys, values or tophash of a bucket is not an array")
+		return false
+	}
+
+	if it.tophashes.Len != it.keys.Len || it.tophashes.Len != it.values.Len {
+		it.v.Unreadable = fmt.Errorf("malformed map type: inconsistent array length in bucket")
+		return false
+	}
+
+	return true
+}
+
+func (it *mapIterator) next() bool {
+	for {
+		if it.b == nil || it.idx >= it.tophashes.Len {
+			r := it.nextBucket()
+			if !r {
+				return false
+			}
+			it.idx = 0
+		}
+		tophash, _ := it.tophashes.sliceAccess(int(it.idx))
+		h, err := tophash.asUint()
+		if err != nil {
+			it.v.Unreadable = fmt.Errorf("unreadable tophash: %v", err)
+			return false
+		}
+		it.idx++
+		if h != hashTophashEmpty {
+			return true
+		}
+	}
+}
+
+func (it *mapIterator) key() *Variable {
+	k, _ := it.keys.sliceAccess(int(it.idx - 1))
+	return k
+}
+
+func (it *mapIterator) value() *Variable {
+	v, _ := it.values.sliceAccess(int(it.idx - 1))
+	return v
+}
+
+func mapEvacuated(b *Variable) bool {
+	if b.Addr == 0 {
+		return true
+	}
+	for _, f := range b.DwarfType.(*dwarf.StructType).Field {
+		if f.Name != "tophash" {
+			continue
+		}
+		tophashes, _ := b.toField(f)
+		tophash0var, _ := tophashes.sliceAccess(0)
+		tophash0, err := tophash0var.asUint()
+		if err != nil {
+			return true
+		}
+		return tophash0 > hashTophashEmpty && tophash0 < hashMinTopHash
+	}
+	return true
+}
+
 // Fetches all variables of a specific type in the current function scope
 func (scope *EvalScope) variablesByTag(tag dwarf.Tag) ([]*Variable, error) {
 	reader := scope.DwarfReader()

service/api/prettyprint.go

@@ -163,13 +163,13 @@ func (v *Variable) writeMapTo(buf *bytes.Buffer, newlines, includeType bool, ind
 		}
 	}
 
-	if len(v.Children) != int(v.Len) {
+	if len(v.Children)/2 != int(v.Len) {
 		if nl {
 			fmt.Fprintf(buf, "\n%s%s", indent, indentString)
 		} else {
 			fmt.Fprintf(buf, ",")
 		}
-		fmt.Fprintf(buf, "...+%d more", int(v.Len)-len(v.Children))
+		fmt.Fprintf(buf, "...+%d more", int(v.Len)-(len(v.Children)/2))
 	}
 
 	if nl {

service/test/variables_test.go

@@ -389,6 +389,14 @@ func TestEvalExpression(t *testing.T) {
 		{"ch1", true, "chan int 0/2", "", "chan int", nil},
 		{"ch1+1", false, "", "", "", fmt.Errorf("can not convert 1 constant to chan int")},
 
+		// maps
+		{"m1[\"Malone\"]", false, "struct main.astruct {A: 2, B: 3}", "", "struct main.astruct", nil},
+		{"m2[1].B", false, "11", "", "int", nil},
+		{"m2[c1.sa[2].B-4].A", false, "10", "", "int", nil},
+		{"m2[*p1].B", false, "11", "", "int", nil},
+		{"m3[as1]", false, "42", "", "int", nil},
+		{"mnil[\"Malone\"]", false, "", "", "", fmt.Errorf("key not found")},
+
 		// combined expressions
 		{"c1.pb.a.A", true, "1", "", "int", nil},
 		{"c1.sa[1].B", false, "3", "", "int", nil},
@@ -462,6 +470,9 @@ func TestEvalExpression(t *testing.T) {
 		{"ch1 == nil", false, "false", "", "", nil},
 		{"chnil == nil", false, "true", "", "", nil},
 		{"ch1 == chnil", false, "", "", "", fmt.Errorf("can not compare chan variables")},
+		{"m1 == nil", false, "false", "", "", nil},
+		{"mnil == m1", false, "", "", "", fmt.Errorf("can not compare map variables")},
+		{"mnil == nil", false, "true", "", "", nil},
 
 		// errors
 		{"&3", false, "", "", "", fmt.Errorf("can not take address of \"3\"")},
@@ -521,3 +532,38 @@ func TestEvalAddrAndCast(t *testing.T) {
 		assertVariable(t, a, varTest{aaddrstr, false, "struct main.astruct {A: 1, B: 2}", "", "struct main.astruct", nil})
 	})
 }
+
+func TestMapEvaluation(t *testing.T) {
+	withTestProcess("testvariables3", t, func(p *proc.Process, fixture protest.Fixture) {
+		assertNoError(p.Continue(), t, "Continue() returned an error")
+		m1v, err := evalVariable(p, "m1")
+		assertNoError(err, t, "EvalVariable()")
+		m1 := api.ConvertVar(m1v)
+		t.Logf("m1 = %v", m1.MultilineString(""))
+
+		if m1.Type != "map[string]main.astruct" {
+			t.Fatalf("Wrong type: %s", m1.Type)
+		}
+
+		if len(m1.Children)/2 != 41 {
+			t.Fatalf("Wrong number of children: %d", len(m1.Children)/2)
+		}
+
+		found := false
+		for i := range m1.Children {
+			if i%2 == 0 && m1.Children[i].Value == "Malone" {
+				found = true
+			}
+		}
+		if !found {
+			t.Fatalf("Could not find Malone")
+		}
+
+		m1sliced, err := evalVariable(p, "m1[10:]")
+		assertNoError(err, t, "EvalVariable(m1[10:])")
+		if len(m1sliced.Children)/2 != int(m1.Len-10) {
+			t.Fatalf("Wrong number of children (after slicing): %d", len(m1sliced.Children)/2)
+		}
+	})
+
+}