Android: Fix NullPointerException seen on Google Play

According to Google Plays automated crash detection, we get a
NullPointerException when trying to parse a null string as a
Uri.

This turns out to be caused by us trying to open a PDF attachment
from gmail. This is because MuPDF is invoked with a content:// URL
that does not have a file associated with it. Instead we can open
that URL as an InputStream.

Here we amend MuPDF to spot that case, and to open the InputStream,
suck the data into a byteArray, and then to use that to open the
file from.

4 files changed, 213 insertions, 7 deletions

diff --git a/android/jni/mupdf.c b/android/jni/mupdf.c
index ecb9f20b..a4180e54 100644
--- a/android/jni/mupdf.c
+++ b/android/jni/mupdf.c
@@ -13,6 +13,7 @@
 #endif
 
 #include "fitz.h"
+#include "fitz-internal.h"
 #include "mupdf.h"
 
 #define JNI_FN(A) Java_com_artifex_mupdfdemo_ ## A
@@ -89,9 +90,15 @@ struct globals_s
 	int alert_reply;
 	pthread_cond_t alert_request_cond;
 	pthread_cond_t alert_reply_cond;
+
+	// For the buffer reading mode, we need to implement stream reading, which
+	// needs access to the following.
+	JNIEnv *env;
+	jclass thiz;
 };
 
 static jfieldID global_fid;
+static jfieldID buffer_fid;
 
 static void drop_page_cache(globals *glo, page_cache *pc)
 {
@@ -225,7 +232,10 @@ static void alerts_fin(globals *glo)
 
 static globals *get_globals(JNIEnv *env, jobject thiz)
 {
-	return (globals *)(void *)((*env)->GetLongField(env, thiz, global_fid));
+	globals *glo = (globals *)(void *)((*env)->GetLongField(env, thiz, global_fid));
+	glo->env = env;
+	glo->thiz = thiz;
+	return glo;
 }
 
 JNIEXPORT jlong JNICALL
@@ -281,7 +291,7 @@ JNI_FN(MuPDFCore_openFile)(JNIEnv * env, jobject thiz, jstring jfilename)
 		}
 		fz_catch(ctx)
 		{
-			fz_throw(ctx, "Cannot open document: '%s'\n", filename);
+			fz_throw(ctx, "Cannot open document: '%s'", filename);
 		}
 		LOGE("Done!");
 	}
@@ -301,6 +311,123 @@ JNI_FN(MuPDFCore_openFile)(JNIEnv * env, jobject thiz, jstring jfilename)
 	return (jlong)(void *)glo;
 }
 
+static int bufferStreamRead(fz_stream *stream, unsigned char *buf, int len)
+{
+	globals    *glo = (globals *)stream->state;
+	JNIEnv     *env = glo->env;
+	jbyteArray  array = (jbyteArray)(void *)((*env)->GetObjectField(env, glo->thiz, buffer_fid));
+	int         arrayLength = (*env)->GetArrayLength(env, array);
+
+	if (stream->pos > arrayLength)
+		stream->pos = arrayLength;
+	if (stream->pos < 0)
+		stream->pos = 0;
+	if (len + stream->pos > arrayLength)
+		len = arrayLength - stream->pos;
+
+	(*env)->GetByteArrayRegion(env, array, stream->pos, len, buf);
+	(*env)->DeleteLocalRef(env, array);
+	return len;
+}
+
+static void bufferStreamClose(fz_context *ctx, void *state)
+{
+	/* Nothing to do */
+}
+
+static void bufferStreamSeek(fz_stream *stream, int offset, int whence)
+{
+	globals    *glo = (globals *)stream->state;
+	JNIEnv     *env = glo->env;
+	jbyteArray  array = (jbyteArray)(void *)((*env)->GetObjectField(env, glo->thiz, buffer_fid));
+	int         arrayLength = (*env)->GetArrayLength(env, array);
+
+	(*env)->DeleteLocalRef(env, array);
+
+	if (whence == 0) /* SEEK_SET */
+		stream->pos = offset;
+	else if (whence == 1) /* SEEK_CUR */
+		stream->pos += offset;
+	else if (whence == 2) /* SEEK_END */
+		stream->pos = arrayLength + offset;
+
+	if (stream->pos > arrayLength)
+		stream->pos = arrayLength;
+	if (stream->pos < 0)
+		stream->pos = 0;
+
+	stream->rp = stream->bp;
+	stream->wp = stream->bp;
+}
+
+JNIEXPORT jlong JNICALL
+JNI_FN(MuPDFCore_openBuffer)(JNIEnv * env, jobject thiz)
+{
+	globals    *glo;
+	fz_context *ctx;
+	jclass      clazz;
+	fz_stream *stream;
+
+#ifdef NDK_PROFILER
+	monstartup("libmupdf.so");
+#endif
+
+	clazz = (*env)->GetObjectClass(env, thiz);
+	global_fid = (*env)->GetFieldID(env, clazz, "globals", "J");
+
+	glo = calloc(1, sizeof(*glo));
+	if (glo == NULL)
+		return 0;
+	glo->resolution = 160;
+	glo->alerts_initialised = 0;
+	glo->env = env;
+	glo->thiz = thiz;
+	buffer_fid = (*env)->GetFieldID(env, clazz, "fileBuffer", "[B");
+
+	/* 128 MB store for low memory devices. Tweak as necessary. */
+	glo->ctx = ctx = fz_new_context(NULL, NULL, 128 << 20);
+	if (!ctx)
+	{
+		LOGE("Failed to initialise context");
+		free(glo);
+		return 0;
+	}
+
+	glo->doc = NULL;
+	fz_try(ctx)
+	{
+		stream = fz_new_stream(ctx, glo, bufferStreamRead, bufferStreamClose);
+		stream->seek = bufferStreamSeek;
+
+		glo->colorspace = fz_device_rgb;
+
+		LOGE("Opening document...");
+		fz_try(ctx)
+		{
+			glo->current_path = NULL;
+			glo->doc = fz_open_document_with_stream(ctx, "", stream);
+			alerts_init(glo);
+		}
+		fz_catch(ctx)
+		{
+			fz_throw(ctx, "Cannot open memory document");
+		}
+		LOGE("Done!");
+	}
+	fz_catch(ctx)
+	{
+		LOGE("Failed: %s", ctx->error->message);
+		fz_close_document(glo->doc);
+		glo->doc = NULL;
+		fz_free_context(ctx);
+		glo->ctx = NULL;
+		free(glo);
+		glo = NULL;
+	}
+
+	return (jlong)(void *)glo;
+}
+
 JNIEXPORT int JNICALL
 JNI_FN(MuPDFCore_countPagesInternal)(JNIEnv *env, jobject thiz)
 {
diff --git a/android/res/values/strings.xml b/android/res/values/strings.xml
index 72794bcc..1468d963 100644
--- a/android/res/values/strings.xml
+++ b/android/res/values/strings.xml
@@ -1,10 +1,11 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <string name="app_name">MuPDF</string>
-    <string name="version">1.1</string>
+    <string name="version">1.1 (Build 6)</string>
     <string name="no_media_warning">Storage Media not present</string>
     <string name="no_media_hint">Sharing the storage media with a PC can make it inaccessible</string>
     <string name="open_failed">Unable to open document</string>
+    <string name="content_failure">%1$s: %2$s</string>
     <string name="cancel">Cancel</string>
     <string name="search_backwards">Search backwards</string>
     <string name="search_forwards">Search forwards</string>
diff --git a/android/src/com/artifex/mupdfdemo/MuPDFActivity.java b/android/src/com/artifex/mupdfdemo/MuPDFActivity.java
index f41b6178..f095a041 100644
--- a/android/src/com/artifex/mupdfdemo/MuPDFActivity.java
+++ b/android/src/com/artifex/mupdfdemo/MuPDFActivity.java
@@ -1,6 +1,8 @@
 package com.artifex.mupdfdemo;
 
 import java.util.concurrent.Executor;
+import java.io.InputStream;
+import java.io.FileInputStream;
 
 import android.animation.Animator;
 import android.animation.AnimatorInflater;
@@ -12,6 +14,7 @@ import android.content.Context;
 import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.SharedPreferences;
+import android.content.res.Resources;
 import android.database.Cursor;
 import android.graphics.Color;
 import android.graphics.RectF;
@@ -260,6 +263,23 @@ public class MuPDFActivity extends Activity
 		return core;
 	}
 
+	private MuPDFCore openBuffer(byte buffer[])
+	{
+		System.out.println("Trying to open byte buffer");
+		try
+		{
+			core = new MuPDFCore(buffer);
+			// New file: drop the old outline data
+			OutlineActivityData.set(null);
+		}
+		catch (Exception e)
+		{
+			System.out.println(e);
+			return null;
+		}
+		return core;
+	}
+
 	/** Called when the activity is first created. */
 	@Override
 	public void onCreate(Bundle savedInstanceState)
@@ -292,6 +312,7 @@ public class MuPDFActivity extends Activity
 		}
 		if (core == null) {
 			Intent intent = getIntent();
+			byte buffer[] = null;
 			if (Intent.ACTION_VIEW.equals(intent.getAction())) {
 				Uri uri = intent.getData();
 				if (uri.toString().startsWith("content://")) {
@@ -300,10 +321,51 @@ public class MuPDFActivity extends Activity
 					// using explicit paths.
 					Cursor cursor = getContentResolver().query(uri, new String[]{"_data"}, null, null, null);
 					if (cursor.moveToFirst()) {
-						uri = Uri.parse(cursor.getString(0));
+						String str = cursor.getString(0);
+						String failString = null;
+						if (str == null) {
+							try {
+								InputStream is = getContentResolver().openInputStream(uri);
+								int len = is.available();
+								buffer = new byte[len];
+								is.read(buffer, 0, len);
+								is.close();
+							}
+							catch (java.lang.OutOfMemoryError e)
+							{
+								System.out.println("Out of memory during buffer reading");
+								failString = e.toString();
+							}
+							catch (Exception e) {
+								failString = e.toString();
+							}
+							if (failString != null)
+							{
+								buffer = null;
+								Resources res = getResources();
+								AlertDialog alert = mAlertBuilder.create();
+								String contentFailure = res.getString(R.string.content_failure);
+								String openFailed = res.getString(R.string.open_failed);
+								setTitle(String.format(contentFailure, openFailed, failString));
+								alert.setButton(AlertDialog.BUTTON_POSITIVE, "Dismiss",
+										new DialogInterface.OnClickListener() {
+											public void onClick(DialogInterface dialog, int which) {
+												finish();
+											}
+										});
+								alert.show();
+								return;
+							}
+						} else {
+							uri = Uri.parse(str);
+						}
 					}
 				}
-				core = openFile(Uri.decode(uri.getEncodedPath()));
+				if (buffer != null) {
+					core = openBuffer(buffer);
+				} else {
+					core = openFile(Uri.decode(uri.getEncodedPath()));
+				}
 				SearchTaskResult.set(null);
 			}
 			if (core != null && core.needsPassword()) {
@@ -1023,17 +1085,21 @@ public class MuPDFActivity extends Activity
 	@Override
 	protected void onStart() {
 		if (core != null)
+		{
 			core.startAlerts();
+			createAlertWaiter();
+		}
 
-		createAlertWaiter();
 		super.onStart();
 	}
 
 	@Override
 	protected void onStop() {
-		destroyAlertWaiter();
 		if (core != null)
+		{
+			destroyAlertWaiter();
 			core.stopAlerts();
+		}
 
 		super.onStop();
 	}
diff --git a/android/src/com/artifex/mupdfdemo/MuPDFCore.java b/android/src/com/artifex/mupdfdemo/MuPDFCore.java
index cf35be8d..ed9ded92 100644
--- a/android/src/com/artifex/mupdfdemo/MuPDFCore.java
+++ b/android/src/com/artifex/mupdfdemo/MuPDFCore.java
@@ -18,9 +18,11 @@ public class MuPDFCore
 	private float pageWidth;
 	private float pageHeight;
 	private long globals;
+	private byte fileBuffer[];
 
 	/* The native functions */
 	private native long openFile(String filename);
+	private native long openBuffer();
 	private native int countPagesInternal();
 	private native void gotoPageInternal(int localActionPageNum);
 	private native float getPageWidth();
@@ -68,6 +70,16 @@ public class MuPDFCore
 		}
 	}
 
+	public MuPDFCore(byte buffer[]) throws Exception
+	{
+		fileBuffer = buffer;
+		globals = openBuffer();
+		if (globals == 0)
+		{
+			throw new Exception("Failed to open buffer");
+		}
+	}
+
 	public  int countPages()
 	{
 		if (numPages < 0)