Merge META-INF/services/* files in merge_zips -jar

kotlinx_coroutines_test and kotlinx_coroutine_android each provide a
META-INF/services/kotlinx.coroutines.CoroutineExceptionHandler with
different contents, and the final contents needs to be the combination
of the two files.  Implement service merging in merge_zips when the
-jar argument is provided.

Bug: 290933559
Test: TestMergeZips
Change-Id: I69f80d1265c64c671d308ef4cdccfa1564abe056

jar/Android.bp

@@ -21,6 +21,7 @@ bootstrap_go_package {
     pkgPath: "android/soong/jar",
     srcs: [
         "jar.go",
+        "services.go",
     ],
     testSrcs: [
         "jar_test.go",

jar/services.go

@@ -0,0 +1,128 @@
+// Copyright 2023 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package jar
+
+import (
+	"android/soong/third_party/zip"
+	"bufio"
+	"hash/crc32"
+	"sort"
+	"strings"
+)
+
+const servicesPrefix = "META-INF/services/"
+
+// Services is used to collect service files from multiple zip files and produce a list of ServiceFiles containing
+// the unique lines from all the input zip entries with the same name.
+type Services struct {
+	services map[string]*ServiceFile
+}
+
+// ServiceFile contains the combined contents of all input zip entries with a single name.
+type ServiceFile struct {
+	Name       string
+	FileHeader *zip.FileHeader
+	Contents   []byte
+	Lines      []string
+}
+
+// IsServiceFile returns true if the zip entry is in the META-INF/services/ directory.
+func (Services) IsServiceFile(entry *zip.File) bool {
+	return strings.HasPrefix(entry.Name, servicesPrefix)
+}
+
+// AddServiceFile adds a zip entry in the META-INF/services/ directory to the list of service files that need
+// to be combined.
+func (j *Services) AddServiceFile(entry *zip.File) error {
+	if j.services == nil {
+		j.services = map[string]*ServiceFile{}
+	}
+
+	service := entry.Name
+	serviceFile := j.services[service]
+	fh := entry.FileHeader
+	if serviceFile == nil {
+		serviceFile = &ServiceFile{
+			Name:       service,
+			FileHeader: &fh,
+		}
+		j.services[service] = serviceFile
+	}
+
+	f, err := entry.Open()
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if line != "" {
+			serviceFile.Lines = append(serviceFile.Lines, line)
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// ServiceFiles returns the list of combined service files, each containing all the unique lines from the
+// corresponding service files in the input zip entries.
+func (j *Services) ServiceFiles() []ServiceFile {
+	services := make([]ServiceFile, 0, len(j.services))
+
+	for _, serviceFile := range j.services {
+		serviceFile.Lines = dedupServicesLines(serviceFile.Lines)
+		serviceFile.Lines = append(serviceFile.Lines, "")
+		serviceFile.Contents = []byte(strings.Join(serviceFile.Lines, "\n"))
+
+		serviceFile.FileHeader.UncompressedSize64 = uint64(len(serviceFile.Contents))
+		serviceFile.FileHeader.CRC32 = crc32.ChecksumIEEE(serviceFile.Contents)
+		if serviceFile.FileHeader.Method == zip.Store {
+			serviceFile.FileHeader.CompressedSize64 = serviceFile.FileHeader.UncompressedSize64
+		}
+
+		services = append(services, *serviceFile)
+	}
+
+	sort.Slice(services, func(i, j int) bool {
+		return services[i].Name < services[j].Name
+	})
+
+	return services
+}
+
+func dedupServicesLines(in []string) []string {
+	writeIndex := 0
+outer:
+	for readIndex := 0; readIndex < len(in); readIndex++ {
+		for compareIndex := 0; compareIndex < writeIndex; compareIndex++ {
+			if interface{}(in[readIndex]) == interface{}(in[compareIndex]) {
+				// The value at readIndex already exists somewhere in the output region
+				// of the slice before writeIndex, skip it.
+				continue outer
+			}
+		}
+		if readIndex != writeIndex {
+			in[writeIndex] = in[readIndex]
+		}
+		writeIndex++
+	}
+	return in[0:writeIndex]
+}