gotosocial/vendor/github.com/godbus/dbus/v5/encoder.go
Daniele Sluijters acc333c40b
[feature] Inherit resource limits from cgroups (#1336)
When GTS is running in a container runtime which has configured CPU or
memory limits or under an init system that uses cgroups to impose CPU
and memory limits the values the Go runtime sees for GOMAXPROCS and
GOMEMLIMIT are still based on the host resources, not the cgroup.

At least for the throttling middlewares which use GOMAXPROCS to
configure their queue size, this can result in GTS running with values
too big compared to the resources that will actuall be available to it.

This introduces 2 dependencies which can pick up resource contraints
from the current cgroup and tune the Go runtime accordingly. This should
result in the different queues being appropriately sized and in general
more predictable performance. These dependencies are a no-op on
non-Linux systems or if running in a cgroup that doesn't set a limit on
CPU or memory.

The automatic tuning of GOMEMLIMIT can be disabled by either explicitly
setting GOMEMLIMIT yourself or by setting AUTOMEMLIMIT=off. The
automatic tuning of GOMAXPROCS can similarly be counteracted by setting
GOMAXPROCS yourself.
2023-01-17 20:59:04 +00:00

210 lines
5.4 KiB
Go

package dbus
import (
"bytes"
"encoding/binary"
"io"
"reflect"
)
// An encoder encodes values to the D-Bus wire format.
type encoder struct {
out io.Writer
order binary.ByteOrder
pos int
}
// NewEncoder returns a new encoder that writes to out in the given byte order.
func newEncoder(out io.Writer, order binary.ByteOrder) *encoder {
return newEncoderAtOffset(out, 0, order)
}
// newEncoderAtOffset returns a new encoder that writes to out in the given
// byte order. Specify the offset to initialize pos for proper alignment
// computation.
func newEncoderAtOffset(out io.Writer, offset int, order binary.ByteOrder) *encoder {
enc := new(encoder)
enc.out = out
enc.order = order
enc.pos = offset
return enc
}
// Aligns the next output to be on a multiple of n. Panics on write errors.
func (enc *encoder) align(n int) {
pad := enc.padding(0, n)
if pad > 0 {
empty := make([]byte, pad)
if _, err := enc.out.Write(empty); err != nil {
panic(err)
}
enc.pos += pad
}
}
// pad returns the number of bytes of padding, based on current position and additional offset.
// and alignment.
func (enc *encoder) padding(offset, algn int) int {
abs := enc.pos + offset
if abs%algn != 0 {
newabs := (abs + algn - 1) & ^(algn - 1)
return newabs - abs
}
return 0
}
// Calls binary.Write(enc.out, enc.order, v) and panics on write errors.
func (enc *encoder) binwrite(v interface{}) {
if err := binary.Write(enc.out, enc.order, v); err != nil {
panic(err)
}
}
// Encode encodes the given values to the underlying reader. All written values
// are aligned properly as required by the D-Bus spec.
func (enc *encoder) Encode(vs ...interface{}) (err error) {
defer func() {
err, _ = recover().(error)
}()
for _, v := range vs {
enc.encode(reflect.ValueOf(v), 0)
}
return nil
}
// encode encodes the given value to the writer and panics on error. depth holds
// the depth of the container nesting.
func (enc *encoder) encode(v reflect.Value, depth int) {
enc.align(alignment(v.Type()))
switch v.Kind() {
case reflect.Uint8:
var b [1]byte
b[0] = byte(v.Uint())
if _, err := enc.out.Write(b[:]); err != nil {
panic(err)
}
enc.pos++
case reflect.Bool:
if v.Bool() {
enc.encode(reflect.ValueOf(uint32(1)), depth)
} else {
enc.encode(reflect.ValueOf(uint32(0)), depth)
}
case reflect.Int16:
enc.binwrite(int16(v.Int()))
enc.pos += 2
case reflect.Uint16:
enc.binwrite(uint16(v.Uint()))
enc.pos += 2
case reflect.Int, reflect.Int32:
enc.binwrite(int32(v.Int()))
enc.pos += 4
case reflect.Uint, reflect.Uint32:
enc.binwrite(uint32(v.Uint()))
enc.pos += 4
case reflect.Int64:
enc.binwrite(v.Int())
enc.pos += 8
case reflect.Uint64:
enc.binwrite(v.Uint())
enc.pos += 8
case reflect.Float64:
enc.binwrite(v.Float())
enc.pos += 8
case reflect.String:
enc.encode(reflect.ValueOf(uint32(len(v.String()))), depth)
b := make([]byte, v.Len()+1)
copy(b, v.String())
b[len(b)-1] = 0
n, err := enc.out.Write(b)
if err != nil {
panic(err)
}
enc.pos += n
case reflect.Ptr:
enc.encode(v.Elem(), depth)
case reflect.Slice, reflect.Array:
if depth >= 64 {
panic(FormatError("input exceeds container depth limit"))
}
// Lookahead offset: 4 bytes for uint32 length (with alignment),
// plus alignment for elements.
n := enc.padding(0, 4) + 4
offset := enc.pos + n + enc.padding(n, alignment(v.Type().Elem()))
var buf bytes.Buffer
bufenc := newEncoderAtOffset(&buf, offset, enc.order)
for i := 0; i < v.Len(); i++ {
bufenc.encode(v.Index(i), depth+1)
}
enc.encode(reflect.ValueOf(uint32(buf.Len())), depth)
length := buf.Len()
enc.align(alignment(v.Type().Elem()))
if _, err := buf.WriteTo(enc.out); err != nil {
panic(err)
}
enc.pos += length
case reflect.Struct:
if depth >= 64 && v.Type() != signatureType {
panic(FormatError("input exceeds container depth limit"))
}
switch t := v.Type(); t {
case signatureType:
str := v.Field(0)
enc.encode(reflect.ValueOf(byte(str.Len())), depth+1)
b := make([]byte, str.Len()+1)
copy(b, str.String())
b[len(b)-1] = 0
n, err := enc.out.Write(b)
if err != nil {
panic(err)
}
enc.pos += n
case variantType:
variant := v.Interface().(Variant)
enc.encode(reflect.ValueOf(variant.sig), depth+1)
enc.encode(reflect.ValueOf(variant.value), depth+1)
default:
for i := 0; i < v.Type().NumField(); i++ {
field := t.Field(i)
if field.PkgPath == "" && field.Tag.Get("dbus") != "-" {
enc.encode(v.Field(i), depth+1)
}
}
}
case reflect.Map:
// Maps are arrays of structures, so they actually increase the depth by
// 2.
if depth >= 63 {
panic(FormatError("input exceeds container depth limit"))
}
if !isKeyType(v.Type().Key()) {
panic(InvalidTypeError{v.Type()})
}
keys := v.MapKeys()
// Lookahead offset: 4 bytes for uint32 length (with alignment),
// plus 8-byte alignment
n := enc.padding(0, 4) + 4
offset := enc.pos + n + enc.padding(n, 8)
var buf bytes.Buffer
bufenc := newEncoderAtOffset(&buf, offset, enc.order)
for _, k := range keys {
bufenc.align(8)
bufenc.encode(k, depth+2)
bufenc.encode(v.MapIndex(k), depth+2)
}
enc.encode(reflect.ValueOf(uint32(buf.Len())), depth)
length := buf.Len()
enc.align(8)
if _, err := buf.WriteTo(enc.out); err != nil {
panic(err)
}
enc.pos += length
case reflect.Interface:
enc.encode(reflect.ValueOf(MakeVariant(v.Interface())), depth)
default:
panic(InvalidTypeError{v.Type()})
}
}