use golang to get cache-id

7 files changed, 178 insertions, 23 deletions

diff --git a/.SRCINFO b/.SRCINFO
index cdc75a36056b..f4a9e8eff2f0 100644
--- a/.SRCINFO
+++ b/.SRCINFO
@@ -1,6 +1,6 @@
 pkgbase = mkinitcpio-docker-hooks
 	pkgdesc = mkinitcpio hooks that provides support for using docker image as root
-	pkgver = 1.0
+	pkgver = 1.1
 	pkgrel = 1
 	url = https://github.com/zasdfgbnm/mkinitcpio-docker-hooks
 	arch = any
@@ -8,13 +8,15 @@ pkgbase = mkinitcpio-docker-hooks
 	license = GPL
 	depends = mkinitcpio
 	depends = jq
-	backup = etc/docker-btrfs.sh
+	backup = etc/docker-btrfs.json
 	source = install_docker-btrfs
 	source = hooks_docker-btrfs
-	source = etc_docker-btrfs.sh
-	md5sums = 0da33ef9ff132737a09173fdd45cddd6
-	md5sums = e1d51dd467412b48361c648226e6b57e
-	md5sums = a1243d4a874f69ef696f5c6ac58424cb
+	source = etc_docker-btrfs.json
+	source = get-docker-cache-id.go
+	md5sums = 5ce9a3498b0af7e9fbbe830893da83e3
+	md5sums = b44c59a25ef2ff74e60d20aaabe683fd
+	md5sums = 4df2fd7306aef1e3d94ffc6b05056728
+	md5sums = bcae1950b172498e34c1aa4cb55ecad0
 
 pkgname = mkinitcpio-docker-hooks
 
diff --git a/PKGBUILD b/PKGBUILD
index c400a964914a..adbd2ed89295 100644
--- a/PKGBUILD
+++ b/PKGBUILD
@@ -1,6 +1,7 @@
 # Maintainer: Xiang Gao <qasdfgtyuiop at gmail dot com>
+
 pkgname=mkinitcpio-docker-hooks
-pkgver=1.0
+pkgver=1.1
 pkgrel=1
 pkgdesc="mkinitcpio hooks that provides support for using docker image as root"
 arch=(any)
@@ -8,14 +9,20 @@ url="https://github.com/zasdfgbnm/mkinitcpio-docker-hooks"
 license=('GPL')
 groups=('base')
 depends=('mkinitcpio' 'jq')
-backup=(etc/docker-btrfs.sh)
-source=('install_docker-btrfs' 'hooks_docker-btrfs' 'etc_docker-btrfs.sh')
-md5sums=('0da33ef9ff132737a09173fdd45cddd6'
-         'e1d51dd467412b48361c648226e6b57e'
-         'a1243d4a874f69ef696f5c6ac58424cb')
+backup=(etc/docker-btrfs.json)
+source=('install_docker-btrfs' 'hooks_docker-btrfs' 'etc_docker-btrfs.json' 'get-docker-cache-id.go')
+md5sums=('5ce9a3498b0af7e9fbbe830893da83e3'
+         'b44c59a25ef2ff74e60d20aaabe683fd'
+         '4df2fd7306aef1e3d94ffc6b05056728'
+         'bcae1950b172498e34c1aa4cb55ecad0')
+
+build() {
+    go build get-docker-cache-id.go
+}
 
 package() {
+    install -Dm755 get-docker-cache-id "${pkgdir}/usr/bin/get-docker-cache-id"
     install -Dm644 install_docker-btrfs "${pkgdir}/usr/lib/initcpio/install/docker-btrfs"
     install -Dm644 hooks_docker-btrfs "${pkgdir}/usr/lib/initcpio/hooks/docker-btrfs"
-    install -Dm644 etc_docker-btrfs.sh "${pkgdir}/etc/docker-btrfs.sh"
+    install -Dm644 etc_docker-btrfs.json "${pkgdir}/etc/docker-btrfs.json"
 }
diff --git a/etc_docker-btrfs.json b/etc_docker-btrfs.json
new file mode 100644
index 000000000000..7c5f8a2f6750
--- /dev/null
+++ b/etc_docker-btrfs.json
@@ -0,0 +1,4 @@
+{
+    "docker_image": "archlinux/base",
+    "docker_tag": "latest"
+}
diff --git a/etc_docker-btrfs.sh b/etc_docker-btrfs.sh
deleted file mode 100644
index 1843e6c864aa..000000000000
--- a/etc_docker-btrfs.sh
+++ /dev/null
@@ -1,2 +0,0 @@
-docker_image=archlinux/base
-docker_tag=latest
diff --git a/get-docker-cache-id.go b/get-docker-cache-id.go
new file mode 100644
index 000000000000..cbaf367cda6a
--- /dev/null
+++ b/get-docker-cache-id.go
@@ -0,0 +1,149 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+	"io/ioutil"
+)
+
+const DOCKER_DB_DIR = "/var/lib/docker/image/btrfs"
+const REPO_FILE = DOCKER_DB_DIR + "/repositories.json"
+const CFG_FILE = "/etc/docker-btrfs.json"
+
+func getImageTag() (string, string) {
+	buf, err := ioutil.ReadFile(CFG_FILE)
+	if err != nil {
+		panic(err)
+	}
+	var dat map[string]interface{}
+	err = json.Unmarshal(buf, &dat)
+	if err != nil {
+		panic(err)
+	}
+	return dat["docker_image"].(string), dat["docker_tag"].(string)
+}
+
+func getImageId(image string, tag string) string {
+	buf, err := ioutil.ReadFile(REPO_FILE)
+	if err != nil {
+		panic(err)
+	}
+	var dat map[string]interface{}
+	err = json.Unmarshal(buf, &dat)
+	if err != nil {
+		panic(err)
+	}
+	repositories := dat["Repositories"].(map[string]interface{})
+	imageTags := repositories[image].(map[string]interface{})
+	return imageTags[image+":"+tag].(string)
+}
+
+func getDiffIds(imgId string) []string {
+	imgPath := strings.Replace(imgId, ":", "/", 1)
+	buf, err := ioutil.ReadFile(DOCKER_DB_DIR + "/imagedb/content/" + imgPath)
+	if err != nil {
+		panic(err)
+	}
+	var dat map[string]interface{}
+	err = json.Unmarshal(buf, &dat)
+	if err != nil {
+		panic(err)
+	}
+	rootfs := dat["rootfs"].(map[string]interface{})
+	diffIdsInterface := rootfs["diff_ids"].([]interface{})
+	diffIdsStr := make([]string, len(diffIdsInterface))
+	for i, v := range diffIdsInterface {
+		diffIdsStr[i] = strings.Replace(v.(string), "sha256:", "", 1)
+	}
+	return diffIdsStr
+}
+
+type Node struct {
+	parent string
+	id string
+	diff string
+	cache string
+}
+
+func getNode(id string) Node {
+	var node Node
+
+	node.id = id
+
+	buf, err := ioutil.ReadFile(DOCKER_DB_DIR + "/layerdb/sha256/" + id + "/cache-id")
+	if err != nil {
+		panic(err)
+	}
+	node.cache = strings.Replace(string(buf), "sha256:", "", 1)
+
+	buf, err = ioutil.ReadFile(DOCKER_DB_DIR + "/layerdb/sha256/" + id + "/diff")
+	if err != nil {
+		panic(err)
+	}
+	node.diff = strings.Replace(string(buf), "sha256:", "", 1)
+
+	buf, err = ioutil.ReadFile(DOCKER_DB_DIR + "/layerdb/sha256/" + id + "/parent")
+	if os.IsNotExist(err) {
+		node.parent = ""
+	} else if err != nil {
+		panic(err)
+	} else {
+		node.parent = strings.Replace(string(buf), "sha256:", "", 1)
+	}
+	return node
+}
+
+func readLayerInfo() map[string]Node {
+	files, err := ioutil.ReadDir(DOCKER_DB_DIR + "/layerdb/sha256/")
+    if err != nil {
+        panic(err)
+	}
+	nodes := make(map[string]Node)
+	for i, _ := range files {
+		id := files[i].Name()
+		nodes[id] = getNode(id)
+	}
+	return nodes
+}
+
+func searchForCacheId(diffIds []string, layers map[string]Node) string {
+	candidates := make([]string, 0, len(layers))
+	last := diffIds[len(diffIds)-1]
+	for i, v := range layers {
+		if v.diff == last {
+			sz := len(candidates)
+			candidates = candidates[:sz+1]
+			candidates[sz] = i
+		}
+	}
+	candidatesCurrent := make([]string, len(candidates))
+	for i, v := range candidates {
+		candidatesCurrent[i] = layers[v].parent
+	}
+	for i := len(diffIds)-2; i>=0; i-- {
+		for j := 0; j < len(candidates); {
+			if layers[candidatesCurrent[j]].diff == diffIds[i] {
+				candidatesCurrent[j] = layers[candidatesCurrent[j]].parent
+				j++;
+			} else {
+				oldLen := len(candidates)
+				candidates[j] = candidates[oldLen-1]
+				candidatesCurrent[j] = candidatesCurrent[oldLen-1]
+				candidates = candidates[:oldLen-1]
+				candidatesCurrent = candidatesCurrent[:oldLen - 1]
+			}
+		}
+	}
+	return candidates[0]
+}
+
+func main() {
+	image, tag := getImageTag()
+	imgId := getImageId(image, tag)
+	diffIds := getDiffIds(imgId)
+	layers := readLayerInfo()
+	cacheId := searchForCacheId(diffIds, layers)
+	fmt.Print(cacheId)
+}
diff --git a/hooks_docker-btrfs b/hooks_docker-btrfs
index 31efedf9ebc9..3f764e95d7d8 100755
--- a/hooks_docker-btrfs
+++ b/hooks_docker-btrfs
@@ -1,7 +1,6 @@
 #!/usr/bin/bash
 
 run_hook() {
-    . /etc/docker-btrfs.sh
     docker_rwlayer=$(echo $rootflags | grep -o "subvol=[^,]*" | grep -o "[^=]*\$")
 
     mkdir -p /docker_root
@@ -25,11 +24,7 @@ run_hook() {
     fi
 
     msg ":: getting docker cache subvolume"
-    cd /var/lib/docker/image/btrfs
-    image_id=$(jq ".Repositories.\"$docker_image\".\"$docker_image:$docker_tag\"" repositories.json | sed 's/:/\//g;s/"//g')
-    last_layer_id=$(jq '.rootfs.diff_ids[]' imagedb/content/$image_id | sed 's/"//g' | tail -n 1)
-    cache_id_file=$(grep $last_layer_id -rl layerdb | sed 's/diff/cache-id/g')
-    cache_id=$(cat $cache_id_file)
+    cache_id=$(get-docker-cache-id)
 
     msg ":: creating rwlayer"
     [ -d /docker_root/"$docker_rwlayer" ] && btrfs subvolume delete /docker_root/"$docker_rwlayer"
diff --git a/install_docker-btrfs b/install_docker-btrfs
index 272329d55451..a0550a22b164 100755
--- a/install_docker-btrfs
+++ b/install_docker-btrfs
@@ -4,8 +4,8 @@ build() {
     add_module btrfs
     add_binary btrfs
     add_binary btrfsck
-    add_binary jq
-    add_file /etc/docker-btrfs.sh
+    add_binary get-docker-cache-id
+    add_file /etc/docker-btrfs.json
     add_runscript
 }