From 0c6f9a36049423283052dfaf6eb9e211afe95c89 Mon Sep 17 00:00:00 2001
From: sbwml <admin@cooluc.com>
Date: Fri, 20 Mar 2026 10:11:24 +0800
Subject: [PATCH 3/3] perf(unpack): Use memory mapping to reduce memory usage

Replaced `os.ReadFile` with `mmap` to avoid loading the entire geoip.dat
or geosite.dat file into memory during unpacking. This fixes
out-of-memory errors on low-memory devices.

Signed-off-by: sbwml <admin@cooluc.com>
---
 cmd/unpack/geoip.go   | 18 ++++++++++++++----
 cmd/unpack/geosite.go | 11 ++++++++++-
 go.mod                |  4 +++-
 go.sum                |  4 ++++
 4 files changed, 31 insertions(+), 6 deletions(-)

--- a/cmd/unpack/geoip.go
+++ b/cmd/unpack/geoip.go
@@ -3,14 +3,16 @@ package unpack
 import (
 	"bufio"
 	"fmt"
-	"github.com/spf13/cobra"
-	"github.com/urlesistiana/v2dat/v2data"
-	"go.uber.org/zap"
 	"io"
 	"net/netip"
 	"os"
 	"path/filepath"
 	"strings"
+
+	"github.com/edsrzf/mmap-go"
+	"github.com/spf13/cobra"
+	"github.com/urlesistiana/v2dat/v2data"
+	"go.uber.org/zap"
 )
 
 func newGeoIPCmd() *cobra.Command {
@@ -34,10 +36,18 @@ func newGeoIPCmd() *cobra.Command {
 
 func unpackGeoIP(args *unpackArgs) error {
 	filePath, wantTags, ourDir := args.file, args.filters, args.outDir
-	b, err := os.ReadFile(filePath)
+
+	file, err := os.Open(filePath)
 	if err != nil {
 		return err
 	}
+	defer file.Close()
+
+	b, err := mmap.Map(file, mmap.RDONLY, 0)
+	if err != nil {
+		return fmt.Errorf("error mapping file: %w", err)
+	}
+	defer b.Unmap()
 	geoIPList, err := v2data.LoadGeoIPListFromDAT(b)
 	if err != nil {
 		return err
--- a/cmd/unpack/geosite.go
+++ b/cmd/unpack/geosite.go
@@ -3,6 +3,7 @@ package unpack
 import (
 	"bufio"
 	"fmt"
+	"github.com/edsrzf/mmap-go"
 	"github.com/spf13/cobra"
 	"github.com/urlesistiana/v2dat/v2data"
 	"go.uber.org/zap"
@@ -39,10 +40,18 @@ func newGeoSiteCmd() *cobra.Command {
 
 func unpackGeoSite(args *unpackArgs) error {
 	filePath, suffixes, outDir := args.file, args.filters, args.outDir
-	b, err := os.ReadFile(filePath)
+
+	file, err := os.Open(filePath)
 	if err != nil {
 		return err
 	}
+	defer file.Close()
+
+	b, err := mmap.Map(file, mmap.RDONLY, 0)
+	if err != nil {
+		return fmt.Errorf("error mapping file: %w", err)
+	}
+	defer b.Unmap()
 	geoSiteList, err := v2data.LoadGeoSiteList(b)
 	if err != nil {
 		return err
--- a/go.mod
+++ b/go.mod
@@ -1,8 +1,9 @@
 module github.com/urlesistiana/v2dat
 
-go 1.23
+go 1.25.0
 
 require (
+	github.com/edsrzf/mmap-go v1.2.0
 	github.com/spf13/cobra v1.10.2
 	go.uber.org/zap v1.27.1
 	google.golang.org/protobuf v1.36.11
@@ -12,4 +13,5 @@ require (
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/spf13/pflag v1.0.10 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
+	golang.org/x/sys v0.42.0 // indirect
 )
--- a/go.sum
+++ b/go.sum
@@ -1,6 +1,8 @@
 github.com/cpuguy83/go-md2man/v2 v2.0.6/go.mod h1:oOW0eioCTA6cOiMLiUPZOpcVxMig6NIQQ7OS05n1F4g=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/edsrzf/mmap-go v1.2.0 h1:hXLYlkbaPzt1SaQk+anYwKSRNhufIDCchSPkUD6dD84=
+github.com/edsrzf/mmap-go v1.2.0/go.mod h1:19H/e8pUPLicwkyNgOykDXkJ9F0MHE+Z52B8EIth78Q=
 github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
@@ -22,6 +24,8 @@ go.uber.org/multierr v1.11.0/go.mod h1:2
 go.uber.org/zap v1.27.1 h1:08RqriUEv8+ArZRYSTXy1LeBScaMpVSTBhCeaZYfMYc=
 go.uber.org/zap v1.27.1/go.mod h1:GB2qFLM7cTU87MWRP2mPIjqfIDnGu+VIO4V/SdhGo2E=
 go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
+golang.org/x/sys v0.42.0 h1:omrd2nAlyT5ESRdCLYdm3+fMfNFE/+Rf4bDIQImRJeo=
+golang.org/x/sys v0.42.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
 google.golang.org/protobuf v1.36.11 h1:fV6ZwhNocDyBLK0dj+fg8ektcVegBBuEolpbTQyBNVE=
 google.golang.org/protobuf v1.36.11/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=