Store blobs on file system as if blob key were a Unix filesystem path. (

#105)

This is a backwards-incompatible change. Blobs written using the previous implementation of FileSystemStorageClient will not be able to be read.

src/main/kotlin/org/wfanet/measurement/storage/filesystem/FileSystemStorageClient.kt

@@ -26,15 +26,16 @@ import org.wfanet.measurement.storage.StorageClient
 
 private const val READ_BUFFER_SIZE = 1024 * 4 // 4 KiB
 
-/** [StorageClient] implementation that utilizes flat files in the specified directory as blobs. */
+/** [StorageClient] implementation that stores blobs as files under [directory]. */
 class FileSystemStorageClient(private val directory: File) : StorageClient {
   init {
     require(directory.isDirectory) { "$directory is not a directory" }
   }
 
   override suspend fun writeBlob(blobKey: String, content: Flow<ByteString>): StorageClient.Blob {
-    val file = File(directory, blobKey.base64UrlEncode())
+    val file: File = resolvePath(blobKey)
     withContext(Dispatchers.IO) {
+      file.parentFile.mkdirs()
       file.outputStream().channel.use { byteChannel ->
         content.collect { bytes ->
           for (buffer in bytes.asReadOnlyByteBufferList()) {
@@ -49,8 +50,18 @@ class FileSystemStorageClient(private val directory: File) : StorageClient {
   }
 
   override suspend fun getBlob(blobKey: String): StorageClient.Blob? {
-    val file = File(directory, blobKey.base64UrlEncode())
-    return if (file.exists()) Blob(file) else null
+    val file: File = resolvePath(blobKey)
+    return withContext(Dispatchers.IO) { if (file.exists()) Blob(file) else null }
+  }
+
+  private fun resolvePath(blobKey: String): File {
+    val relativePath =
+      if (File.separatorChar == '/') {
+        blobKey
+      } else {
+        blobKey.replace('/', File.separatorChar)
+      }
+    return directory.resolve(relativePath)
   }
 
   private inner class Blob(private val file: File) : StorageClient.Blob {

src/test/kotlin/org/wfanet/measurement/storage/filesystem/FileSystemStorageClientTest.kt

@@ -14,11 +14,17 @@
 
 package org.wfanet.measurement.storage.filesystem
 
+import com.google.common.truth.Truth.assertThat
+import com.google.protobuf.kotlin.toByteStringUtf8
+import java.nio.file.Paths
+import kotlinx.coroutines.runBlocking
 import org.junit.Before
 import org.junit.Rule
+import org.junit.Test
 import org.junit.rules.TemporaryFolder
 import org.junit.runner.RunWith
 import org.junit.runners.JUnit4
+import org.wfanet.measurement.common.readByteString
 import org.wfanet.measurement.storage.testing.AbstractStorageClientTest
 
 @RunWith(JUnit4::class)
@@ -29,4 +35,17 @@ class FileSystemStorageClientTest : AbstractStorageClientTest<FileSystemStorageC
   fun initClient() {
     storageClient = FileSystemStorageClient(tempDirectory.root)
   }
+
+  @Test
+  fun `writeBlob writes blob to file in subdirectory`() {
+    val content = "Lorem ipsum dolor sit amet".toByteStringUtf8()
+    val blobKey = "a/b/c/file.txt"
+
+    runBlocking { storageClient.writeBlob(blobKey, content) }
+
+    val relativePath = Paths.get("a", "b", "c", "file.txt")
+    val file = tempDirectory.root.toPath().resolve(relativePath).toFile()
+    assertThat(file.exists()).isTrue()
+    assertThat(file.readByteString()).isEqualTo(content)
+  }
 }