Update Android port

* doc/emacs/android.texi (Android Document Providers): Improve
wording of paragraph clarifying limits on subprocesses.
* java/org/gnu/emacs/EmacsService.java (getDocumentTrees): Use
Java standard US-ASCII coding standard instead of the
undocumented ``ASCII'' alias.
(decodeFileName): Remove unused function.
(documentIdFromName):
* src/android.c (android_init_emacs_service): Take a String for
NAME instead of a byte array.
* src/androidvfs.c (android_verify_jni_string): New function.
(android_document_id_from_name): Verify that STRING is a valid
Modified UTF-8 string.

2 files changed, 73 insertions, 5 deletions

diff --git a/src/android.c b/src/android.c
index d8b264a8491..098fa6c383d 100644
--- a/src/android.c
+++ b/src/android.c
@@ -1556,7 +1556,8 @@ android_init_emacs_service (void)
   FIND_METHOD (get_document_trees, "getDocumentTrees",
                "([B)[Ljava/lang/String;");
   FIND_METHOD (document_id_from_name, "documentIdFromName",
-               "(Ljava/lang/String;[B[Ljava/lang/String;)I");
+               "(Ljava/lang/String;Ljava/lang/String;"
+               "[Ljava/lang/String;)I");
   FIND_METHOD (get_tree_uri, "getTreeUri",
                "(Ljava/lang/String;Ljava/lang/String;)"
                "Ljava/lang/String;");
diff --git a/src/androidvfs.c b/src/androidvfs.c
index bab3977ed5a..c174c35f02b 100644
--- a/src/androidvfs.c
+++ b/src/androidvfs.c
@@ -3936,6 +3936,66 @@ static struct android_vops saf_new_vfs_ops;
 /* Chain of all open SAF directory streams.  */
 static struct android_saf_tree_vdir *all_saf_tree_vdirs;
 
+/* Verify that the specified NULL-terminated STRING is a valid JNI
+   ``UTF-8'' string.  Return 0 if so, 1 otherwise.
+
+   The native coding system used by the JVM to store strings derives
+   from UTF-8, but deviates from it in two aspects in an attempt to
+   better represent the UCS-16 based Java String format, and to let
+   strings contain NULL characters while remaining valid C strings:
+   NULL bytes are encoded as two-byte sequences, and Unicode surrogate
+   pairs encoded as two-byte sequences are prefered to four-byte
+   sequences when encoding characters above the BMP.  */
+
+static int
+android_verify_jni_string (const char *name)
+{
+  const unsigned char *chars;
+
+  chars = (unsigned char *) name;
+  while (*chars)
+    {
+      /* Switch on the high 4 bits.  */
+
+      switch (*chars++ >> 4)
+        {
+        case 0 ... 7:
+          /* The 8th bit is clean, so this is a regular C
+             character.  */
+          break;
+
+        case 8 ... 0xb:
+          /* Invalid starting byte! */
+          return 1;
+
+        case 0xf:
+          /* The start of a four byte sequence.  These aren't allowed
+             in Java.  */
+          return 1;
+
+        case 0xe:
+          /* The start of a three byte sequence.  Verify that its
+             continued.  */
+
+          if ((*chars++ & 0xc0) != 0x80)
+            return 1;
+
+          FALLTHROUGH;
+
+        case 0xc ... 0xd:
+          /* The start of a two byte sequence.  Verify that the
+             next byte exists and has its high bit set.  */
+
+          if ((*chars++ & 0xc0) != 0x80)
+            return 1;
+
+          break;
+        }
+    }
+
+  return 0;
+}
+
 /* Find the document ID of the file within TREE_URI designated by
    NAME.
 
@@ -3943,6 +4003,9 @@ static struct android_saf_tree_vdir *all_saf_tree_vdirs;
    individual files.  Each constituent component prior to the last
    must name a directory file within TREE_URI.
 
+   If NAME is not correct for the Java ``modified UTF-8'' coding
+   system, return -1.
+
    Upon success, return 0 or 1 (contingent upon whether or not the
    last component within NAME is a directory) and place the document
    ID of the named file in ID.
@@ -3965,6 +4028,12 @@ android_document_id_from_name (const char *tree_uri, char *name,
   jmethodID method;
   const char *doc_id;
 
+  /* Verify the format of NAME.  Don't allow creating files that
+     contain characters that can't be encoded in Java.  */
+
+  if (android_verify_jni_string (name))
+    return -1;
+
   /* First, create the array that will hold the result.  */
   result = (*android_java_env)->NewObjectArray (android_java_env, 1,
                                                 java_string_class,
@@ -3972,11 +4041,9 @@ android_document_id_from_name (const char *tree_uri, char *name,
   android_exception_check ();
 
   /* Next, create the string for the tree URI and name.  */
-  length = strlen (name);
-  java_name = (*android_java_env)->NewByteArray (android_java_env, length);
+  java_name = (*android_java_env)->NewStringUTF (android_java_env,
+                                                 name);
   android_exception_check_1 (result);
-  (*android_java_env)->SetByteArrayRegion (android_java_env, java_name,
-                                           0, length, (jbyte *) name);
   uri = (*android_java_env)->NewStringUTF (android_java_env, tree_uri);
   android_exception_check_2 (result, java_name);