android: Make org.chromium.base.SysUtils.isLowEndDevice() work without native code.

base/android/java/src/org/chromium/base/SysUtils.java

Index: base/android/java/src/org/chromium/base/SysUtils.java
diff --git a/base/android/java/src/org/chromium/base/SysUtils.java b/base/android/java/src/org/chromium/base/SysUtils.java
index 7af5a40069af8aaf09f499f2a2849aa73cc1576b..ea33438e843c2d20b39193592e38ed60dc45e7e9 100644
--- a/base/android/java/src/org/chromium/base/SysUtils.java
+++ b/base/android/java/src/org/chromium/base/SysUtils.java
@@ -4,15 +4,30 @@
 
 package org.chromium.base;
 
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
 import android.app.ActivityManager;
 import android.app.ActivityManager.MemoryInfo;
 import android.content.Context;
 import android.os.Build;
+import android.util.Log;
 
 /**
  * Exposes system related information about the current device.
  */
 public class SysUtils {
+    // Any device that runs this or an older version of the system cannot be considered 'low-end'
+    private static final int ANDROID_LOW_MEMORY_ANDROID_SDK_THRESHOLD =
+            Build.VERSION_CODES.JELLY_BEAN_MR2;
+
+    // A device reporting strictly more total memory in megabytes cannot be considered 'low-end'.
+    private static final long ANDROID_LOW_MEMORY_DEVICE_THRESHOLD_MB = 512;
+
+    private static final String TAG = "SysUtils";
+
     private static Boolean sLowEndDevice;
 
     private SysUtils() { }
@@ -20,11 +35,63 @@ public class SysUtils {
     /**
      * @return Whether or not this device should be considered a low end device.
      */
+    @CalledByNative
     public static boolean isLowEndDevice() {
-        if (sLowEndDevice == null) sLowEndDevice = nativeIsLowEndDevice();
+        if (Build.VERSION.SDK_INT <= ANDROID_LOW_MEMORY_ANDROID_SDK_THRESHOLD)
+            return false;
+
+        if (sLowEndDevice == null) {
+          boolean isLowEnd = false;
+
+          // Extract total memory RAM size by parsing /proc/meminfo, note that

[bulach, 2013/11/06 12:16:39]

is /proc/meminfo always world readable?

an idea for test would be to extract 44-89 into a "@CalledByNative long
AmountOfPhysicalMemory()" ?
you can then have a gtest in base_unittests that calls that and compares with
the corresponding sysconf..

the decision about low-end-ness will become a simple if with a constant..

+          // this is exactly what the implementation of sysconf(_SC_PHYS_PAGES)
+          // does. However, it can't be called because this method must be
+          // usable before any native code is loaded.
+
+          // An alternative is to use ActivityManager.getMemoryInfo(), but this
+          // requires a valid ActivityManager handle, which can only come from
+          // a valid Context object, which itself cannot be retrieved
+          // during early startup, where this method is called. And making it
+          // an explicit parameter here makes all call paths _much_ more
+          // complicated.
+
+          Pattern pattern = Pattern.compile("^MemTotal:\\s+([0-9]+) kB$");
+          try {
+              FileReader fileReader = new FileReader("/proc/meminfo");
+              try {
+                  BufferedReader reader = new BufferedReader(fileReader);
+                  String line;
+                  for (;;) {
+                      line = reader.readLine();
+                      if (line == null)
+                          break;
+
+                      Matcher m = pattern.matcher(line);
+                      if (!m.find())
+                          continue;
+
+                      long totalMemoryKiloBytes = Long.parseLong(m.group(1));
+
+                      // Sanity check.
+                      if (totalMemoryKiloBytes <= 1024) {
+                          Log.w(TAG, "Invalid /proc/meminfo total size in kB: " + m.group(1));
+                          break;
+                      }
+                      long totalMemoryMegaBytes = totalMemoryKiloBytes * 1024;
+                      isLowEnd = (totalMemoryMegaBytes < ANDROID_LOW_MEMORY_DEVICE_THRESHOLD_MB);
+                      break;
+                  }
+              } finally {
+                  fileReader.close();
+              }
+          } catch (Exception e) {
+              // In case of error, assume this is _not_ a low-end device.
+              Log.w(TAG, "Cannot get total physical size from /proc/meminfo", e);
+          }
+
+          sLowEndDevice = isLowEnd;
+        }
 
         return sLowEndDevice.booleanValue();
     }
-
-    private static native boolean nativeIsLowEndDevice();
 }