Improve attachment memory allocation (#105)

* Improve attachment memory allocation

* added explicit garbage collection

* redundant GC

* added GCs in attachment processor and a FreeOSMemory helper

* added changelog

* linting

* Remove commented call to debug.FreeOSMemory

Co-authored-by: marin thiercelin <marin.thiercelin@pm.me>
Co-authored-by: marinthiercelin <marin.thiercelin@epfl.ch>

CHANGELOG.md

@@ -4,12 +4,19 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+### Added
+- `helper.FreeOSMemory()` to explicitly call the GC and release the memory to the OS
+
+### Changed
+- added new calls to `runtime.GC()` in the low memory attachment processor
+
 ## [2.1.2] 2020-12-01
 ### Added
 - `SetKeyGenerationOffset` to add an offset in key generation time and prevent not-yet-valid keys.
 
 ### Changed
 - Improved canonicalization performance
+- Reduced attachment memory allocation
 
 ## [2.1.1] 2020-11-16
 ### Changed

crypto/attachment.go

@@ -29,6 +29,9 @@ func (ap *AttachmentProcessor) Process(plainData []byte) {
 	if _, err := (*ap.w).Write(plainData); err != nil {
 		panic(err)
 	}
+	if ap.garbageCollector > 0 {
+		defer runtime.GC()
+	}
 }
 
 // Finish closes the attachment and returns the encrypted data.
@@ -36,19 +39,29 @@ func (ap *AttachmentProcessor) Finish() (*PGPSplitMessage, error) {
 	if ap.err != nil {
 		return nil, ap.err
 	}
+
 	if err := (*ap.w).Close(); err != nil {
 		return nil, errors.Wrap(err, "gopengpp: unable to close writer")
 	}
 
+	if ap.garbageCollector > 0 {
+		ap.w = nil
+		runtime.GC()
+	}
+
 	if err := (*ap.pipe).Close(); err != nil {
 		return nil, errors.Wrap(err, "gopengpp: unable to close pipe")
 	}
 
 	ap.done.Wait()
+	splitMsg := ap.split
+
 	if ap.garbageCollector > 0 {
-		runtime.GC()
+		ap.pipe = nil
+		ap.split = nil
+		defer runtime.GC()
 	}
-	return ap.split, nil
+	return splitMsg, nil
 }
 
 // newAttachmentProcessor creates an AttachmentProcessor which can be used to encrypt

helper/mobile.go

@@ -3,6 +3,7 @@ package helper
 import (
 	"encoding/json"
 	goerrors "errors"
+	"runtime/debug"
 
 	"github.com/ProtonMail/gopenpgp/v2/crypto"
 	"github.com/pkg/errors"
@@ -124,3 +125,10 @@ func EncryptSignBinaryDetachedMobile(
 		EncryptedSignatureArmored: encryptedSignature,
 	}, nil
 }
+
+// FreeOSMemory can be used to explicitly
+// call the garbage collector and
+// return the unused memory to the OS.
+func FreeOSMemory() {
+	debug.FreeOSMemory()
+}