Merge pull request #1 from michael-groble/add-implementation

Add implementation

.gitignore

@@ -1,65 +1,4 @@
-# Xcode
-#
-# gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore
-
-## Build generated
-build/
-DerivedData/
-
-## Various settings
-*.pbxuser
-!default.pbxuser
-*.mode1v3
-!default.mode1v3
-*.mode2v3
-!default.mode2v3
-*.perspectivev3
-!default.perspectivev3
-xcuserdata/
-
-## Other
-*.moved-aside
-*.xcuserstate
-
-## Obj-C/Swift specific
-*.hmap
-*.ipa
-*.dSYM.zip
-*.dSYM
-
-## Playgrounds
-timeline.xctimeline
-playground.xcworkspace
-
-# Swift Package Manager
-#
-# Add this line if you want to avoid checking in source code from Swift Package Manager dependencies.
-# Packages/
-.build/
-
-# CocoaPods
-#
-# We recommend against adding the Pods directory to your .gitignore. However
-# you should judge for yourself, the pros and cons are mentioned at:
-# https://guides.cocoapods.org/using/using-cocoapods.html#should-i-check-the-pods-directory-into-source-control
-#
-# Pods/
-
-# Carthage
-#
-# Add this line if you want to avoid checking in source code from Carthage dependencies.
-# Carthage/Checkouts
-
-Carthage/Build
-
-# fastlane
-#
-# It is recommended to not store the screenshots in the git repo. Instead, use fastlane to re-generate the
-# screenshots whenever they are needed.
-# For more information about the recommended setup visit:
-# https://github.com/fastlane/fastlane/blob/master/fastlane/docs/Gitignore.md
-
-fastlane/report.xml
-fastlane/Preview.html
-fastlane/screenshots
-fastlane/test_output
+.DS_Store
+/.build
+/Packages
+/*.xcodeproj

.travis.yml

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+os:
+  - linux
+  - osx
+language: generic
+sudo: required
+dist: trusty
+osx_image: xcode8
+script:
+  - eval "$(curl -sL https://swift.vapor.sh/ci)"

LICENSE

@@ -1,6 +1,6 @@
 BSD 3-Clause License
 
-Copyright (c) 2017, michael-groble
+Copyright (c) 2017, Michael Groble
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without

Package.swift

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+import PackageDescription
+
+let package = Package(
+    name: "Geohash"
+)

README.md

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 # Geohash
+[![Build Status](https://api.travis-ci.org/michael-groble/Geohash.svg?branch=master)](https://travis-ci.org/michael-groble/Geohash)
+
 Native Swift geohash package supporting binary and character encoding
+
+Geohashes are represented internally as 64 bit integers.  A hash can be constructed either using character
+precision (up to 12 characters) or binary precision (up to 32 bits per angle).
+
+```swift
+GeohashBits(location: Location(longitude: -0.1, latitude: 51.5), characterPrecision: 12).hash()
+=> "gcpuvxr1jzf"
+GeohashBits(location: Location(longitude: -0.1, latitude: 51.5), bitPrecision: 26).hash()
+=> "gcpuvxr1jz" 
+```
+
+Note that the last value is truncated at 10 characters (50 bits) even though the "full" representation is 
+52 bits total.  Since the character encoding is Base32, we require 5 bits for each.
+
+The Geohash boundaries and centroids are correctly handled when the character representation provides a 
+different number of bits for latitude and longitude (e.g. geohash 7 which has 18 bits of longitude and 17 
+bits of latitude).
+
+```swift
+GeohashBits(hash: "u10hfr2").boundingBox().center()
+=> (longitude: 0.0995635986328125, latitude: 51.5004730224609)
+```
+
+This is the same answer you will get from PostGIS 
+
+```sql
+select ST_AsText(ST_PointFromGeoHash('u10hfr2'));
+st_astext                  
+--------------------------------------------
+POINT(0.0995635986328125 51.5004730224609)
+```
+
+The library also supports computing neighbors
+
+```swift
+GeohashBits(hash: "u10hfr2c4pv").neighbor(.north).hash()
+=> "u10hfr2c60j"
+```
+
+## Acknowledgements
+Based on the [Redis implementation](https://github.com/antirez/redis/blob/unstable/src/geohash.c), 
+* Copyright (c) 2013-2014, yinqiwen <yinqiwen@gmail.com>
+* Copyright (c) 2014, Matt Stancliff <matt@genges.com>
+* Copyright (c) 2015-2016, Salvatore Sanfilippo <antirez@gmail.com>

Sources/Geohash/BoundingBox.swift

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+//
+//  BoundingBox.swift
+//  Geohash
+//
+//  Created by michael groble on 1/6/17.
+//
+//
+
+public class BoundingBox {
+  let min: Location
+  let max: Location
+
+  public init(min: Location, max: Location) {
+    self.min = min
+    self.max = max
+  }
+
+  public func center() -> Location {
+    return Location(
+      longitude: 0.5 * (self.min.longitude + self.max.longitude),
+      latitude:  0.5 * (self.min.latitude + self.max.latitude)
+    )
+  }
+}