tetragon-rthooks: move code to apply changes

Move applyChanges used to patch the containerd configuration file to its
own file. Useful for next commit.

Signed-off-by: Kornilios Kourtis <[email protected]>

contrib/tetragon-rthooks/cmd/setup/addline.go

@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright Authors of Tetragon
+
+package main
+
+import (
+	"bufio"
+	"os"
+	"strings"
+
+	"github.com/pelletier/go-toml"
+)
+
+// special line number to append at the end of the file
+const appendAtEndLine = -10
+
+type addLine struct {
+	pos         toml.Position
+	line        string
+	replaceLine bool
+}
+
+func applyChanges(fnameIn, fnameOut string, changes []addLine) error {
+	fIn, err := os.Open(fnameIn)
+	if err != nil {
+		return err
+	}
+	defer fIn.Close()
+	cr := "\n"
+	if usesCR(fIn) {
+		cr = "\r\n"
+	}
+
+	fOut, err := os.Create(fnameOut)
+	if err != nil {
+		return err
+	}
+	defer fOut.Close()
+
+	inLine := 0
+	inSc := bufio.NewScanner(fIn)
+	out := bufio.NewWriter(fOut)
+	defer out.Flush()
+	for inSc.Scan() {
+		inLine++
+		lines := []string{}
+		replaceLine := false
+		for i := range changes {
+			ch := &changes[i]
+			if ch.pos.Line == inLine {
+				line := strings.Repeat(" ", ch.pos.Col-1) + ch.line + cr
+				lines = append(lines, line)
+				if ch.replaceLine {
+					replaceLine = true
+				}
+			}
+		}
+		if !replaceLine {
+			out.WriteString(inSc.Text())
+			out.WriteString(cr)
+		}
+		for _, line := range lines {
+			out.WriteString(line)
+		}
+	}
+
+	for i := range changes {
+		ch := &changes[i]
+		if ch.pos.Line == appendAtEndLine {
+			indent := ""
+			if ch.pos.Col > 0 {
+				indent = strings.Repeat(" ", ch.pos.Col-1)
+			}
+			line := indent + ch.line + cr
+			out.WriteString(line)
+		}
+	}
+
+	return nil
+}

contrib/tetragon-rthooks/cmd/setup/patch-containerd-conf.go

@@ -8,7 +8,6 @@ import (
 	"fmt"
 	"log/slog"
 	"os"
-	"strings"
 
 	srvconf "github.com/containerd/containerd/services/server/config"
 	"github.com/pelletier/go-toml"
@@ -18,14 +17,6 @@ import (
 // solution would be to modify the config object and just marshall it instead of just doing text
 // replacements. TBD.
 
-const appendAtEndLine = -10
-
-type addLine struct {
-	pos         toml.Position
-	line        string
-	replaceLine bool
-}
-
 type addOCIHookState struct {
 	cnf *addOCIHookCmd
 	// poor man's patch
@@ -141,65 +132,6 @@ func usesCR(f *os.File) bool {
 	return false
 }
 
-func applyChanges(fnameIn, fnameOut string, changes []addLine) error {
-	fIn, err := os.Open(fnameIn)
-	if err != nil {
-		return err
-	}
-	defer fIn.Close()
-	cr := "\n"
-	if usesCR(fIn) {
-		cr = "\r\n"
-	}
-
-	fOut, err := os.Create(fnameOut)
-	if err != nil {
-		return err
-	}
-	defer fOut.Close()
-
-	inLine := 0
-	inSc := bufio.NewScanner(fIn)
-	out := bufio.NewWriter(fOut)
-	defer out.Flush()
-	for inSc.Scan() {
-		inLine++
-		lines := []string{}
-		replaceLine := false
-		for i := range changes {
-			ch := &changes[i]
-			if ch.pos.Line == inLine {
-				line := strings.Repeat(" ", ch.pos.Col-1) + ch.line + cr
-				lines = append(lines, line)
-				if ch.replaceLine {
-					replaceLine = true
-				}
-			}
-		}
-		if !replaceLine {
-			out.WriteString(inSc.Text())
-			out.WriteString(cr)
-		}
-		for _, line := range lines {
-			out.WriteString(line)
-		}
-	}
-
-	for i := range changes {
-		ch := &changes[i]
-		if ch.pos.Line == appendAtEndLine {
-			indent := ""
-			if ch.pos.Col > 0 {
-				indent = strings.Repeat(" ", ch.pos.Col-1)
-			}
-			line := indent + ch.line + cr
-			out.WriteString(line)
-		}
-	}
-
-	return nil
-}
-
 func (c *addOCIHookCmd) Run(log *slog.Logger) error {
 	changes, err := addOciHook(log, c)
 	if err != nil {