// ReadValues fetches values of the variables that were passed to the Collector
// with AddVariable. The values of any new variables found are also fetched,
// e.g. the targets of pointers or the members of structs, until we reach the
// size limit or we run out of values to fetch.
// The results are output as a []*cd.Variable, which is the type we need to send
// to the Debuglet Controller after we trigger a breakpoint.
func (c *Collector) ReadValues() (out []*cd.Variable) {
for i := 0; i < len(c.table); i++ {
// Create a new cd.Variable for this value, and append it to the output.
dcv := new(cd.Variable)
out = append(out, dcv)
if i == 0 {
// The first element is unused.
continue
}
switch x := c.table[i].(type) {
case mapElement:
key, value, err := c.prog.MapElement(x.Map, x.index)
if err != nil {
dcv.Status = statusMessage(err.Error(), true, refersToVariableValue)
continue
}
// Add a member for the key.
member := addMember(dcv, "key")
if index, ok := c.add(key); !ok {
// The table is full.
member.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
continue
} else {
member.VarTableIndex = int64(index)
}
// Add a member for the value.
member = addMember(dcv, "value")
if index, ok := c.add(value); !ok {
// The table is full.
member.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
} else {
member.VarTableIndex = int64(index)
}
case debug.Var:
if v, err := c.prog.Value(x); err != nil {
dcv.Status = statusMessage(err.Error(), true, refersToVariableValue)
} else {
c.FillValue(v, dcv)
}
}
}
return out
}
// FillValue copies a value into a cd.Variable. Any variables referred to by
// that value, e.g. struct members and pointer targets, are added to the
// collector's queue, to be fetched later by ReadValues.
func (c *Collector) FillValue(v debug.Value, dcv *cd.Variable) {
if c, ok := v.(debug.Channel); ok {
// Convert to channel, which implements indexable.
v = channel{c}
}
// Fill in dcv in a manner depending on the type of the value we got.
switch val := v.(type) {
case int8, int16, int32, int64, bool, uint8, uint16, uint32, uint64, float32, float64, complex64, complex128:
// For simple types, we just print the value to dcv.Value.
dcv.Value = fmt.Sprint(val)
case string:
// Put double quotes around strings.
dcv.Value = strconv.Quote(val)
case debug.String:
if uint64(len(val.String)) < val.Length {
// This string value was truncated.
dcv.Value = strconv.Quote(val.String + "...")
} else {
dcv.Value = strconv.Quote(val.String)
}
case debug.Struct:
// For structs, we add an entry to dcv.Members for each field in the
// struct.
// Each member will contain the name of the field, and the index in the
// output table which will contain the value of that field.
for _, f := range val.Fields {
member := addMember(dcv, f.Name)
if index, ok := c.add(f.Var); !ok {
// The table is full.
member.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
} else {
member.VarTableIndex = int64(index)
}
}
case debug.Map:
dcv.Value = fmt.Sprintf("len = %d", val.Length)
for i := uint64(0); i < val.Length; i++ {
field := addMember(dcv, `⚫`)
if i == maxMapLength {
field.Name = "..."
field.Status = statusMessage(messageTruncated, true, refersToVariableName)
break
}
if index, ok := c.add(mapElement{val, i}); !ok {
// The value table is full; add a member to contain the error message.
field.Name = "..."
field.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
break
} else {
field.VarTableIndex = int64(index)
}
}
case debug.Pointer:
if val.Address == 0 {
dcv.Value = "<nil>"
} else if val.TypeID == 0 {
// We don't know the type of the pointer, so just output the address as
// the value.
dcv.Value = fmt.Sprintf("0x%X", val.Address)
dcv.Status = statusMessage(messageUnknownPointerType, false, refersToVariableName)
} else {
// Adds the pointed-to variable to the table, and links this value to
// that table entry through VarTableIndex.
dcv.Value = fmt.Sprintf("0x%X", val.Address)
target := addMember(dcv, "")
if index, ok := c.add(debug.Var(val)); !ok {
target.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
} else {
target.VarTableIndex = int64(index)
}
}
case indexable:
// Arrays, slices and channels.
dcv.Value = "len = " + fmt.Sprint(val.Len())
for j := uint64(0); j < val.Len(); j++ {
field := addMember(dcv, fmt.Sprint(`[`, j, `]`))
if j == maxArrayLength {
field.Name = "..."
field.Status = statusMessage(messageTruncated, true, refersToVariableName)
break
}
vr := val.Element(j)
if index, ok := c.add(vr); !ok {
// The value table is full; add a member to contain the error message.
field.Name = "..."
field.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
break
} else {
// Add a member with the index as the name.
field.VarTableIndex = int64(index)
}
}
default:
dcv.Status = statusMessage(messageUnknownType, false, refersToVariableName)
}
}
func addMember(v *cd.Variable, name string) *cd.Variable {
v2 := &cd.Variable{Name: name}
v.Members = append(v.Members, v2)
return v2
}