[iOS] Upstream iOS geolocation code

ios/chrome/browser/geolocation/CLLocation+XGeoHeader.mm

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "ios/chrome/browser/geolocation/CLLocation+XGeoHeader.h"
+
+#include "base/basictypes.h"
+#import "third_party/google_toolbox_for_mac/src/Foundation/GTMStringEncoding.h"
+
+NSString* const kGMOLocationDescriptorFormat =
+    @"role: CURRENT_LOCATION\n"
+    @"producer: DEVICE_LOCATION\n"
+    @"timestamp: %lld\n"
+    @"radius: %ld\n"
+    @"latlng <\n"
+    @"  latitude_e7: %.f\n"
+    @"  longitude_e7: %.f\n"
+    @">";
+
+@implementation CLLocation (XGeoHeader)
+
+- (NSString*)cr_serializeStringToWebSafeBase64String:(NSString*)data {
+  GTMStringEncoding* encoder =
+      [GTMStringEncoding rfc4648Base64WebsafeStringEncoding];
+  NSString* base64 =
+      [encoder encode:[data dataUsingEncoding:NSUTF8StringEncoding]];
+  if (base64) {
+    return base64;
+  } else {
+    return @"";
+  }
+}
+
+// Returns the timestamp of this location in microseconds since the UNIX epoch.
+// Returns 0 if the timestamp is unavailable or invalid.
+- (int64)cr_timestampInMicroseconds {
+  NSTimeInterval seconds = [self.timestamp timeIntervalSince1970];
+  if (seconds > 0) {
+    const int64 kSecondsToMicroseconds = 1000000;
+    return (int64)(seconds * kSecondsToMicroseconds);
+  }
+  return 0;
+}
+
+// Returns the horizontal accuracy radius of |location|. The smaller the value,
+// the more accurate the location. A value -1 is returned if accuracy is
+// unavailable.
+- (long)cr_accuracyInMillimeters {
+  const long kMetersToMillimeters = 1000;
+  if (self.horizontalAccuracy > 0) {
+    return (long)(self.horizontalAccuracy * kMetersToMillimeters);
+  }
+  return -1L;
+}
+
+// Returns the LocationDescriptor as an ASCII proto.
+- (NSString*)cr_locationDescriptor {
+  // Construct the location descriptor using its format string.
+  return [NSString stringWithFormat:kGMOLocationDescriptorFormat,
+                                    [self cr_timestampInMicroseconds],
+                                    [self cr_accuracyInMillimeters],
+                                    floor(self.coordinate.latitude * 1e7),
+                                    floor(self.coordinate.longitude * 1e7)];
+}
+
+- (NSString*)cr_xGeoString {
+  NSString* locationDescriptor = [self cr_locationDescriptor];
+  // The "a" indicates that it is an ASCII proto.
+  return [NSString
+      stringWithFormat:@"a %@", [self cr_serializeStringToWebSafeBase64String:
+                                          locationDescriptor]];
+}
+
+@end