rust: use floor for conversion, add integer tests (#735)

Author: drinckes

rust/src/interface.rs

@@ -102,15 +102,15 @@ pub fn is_full(code: &str) -> bool {
 pub fn point_to_integers(pt: Point<f64>) -> (i64, i64) {
     let (lng, lat) = pt.x_y();
 
-    let mut lat_val = (lat * LAT_INTEGER_MULTIPLIER as f64).round() as i64;
+    let mut lat_val = (lat * LAT_INTEGER_MULTIPLIER as f64).floor() as i64;
     lat_val += LATITUDE_MAX as i64 * LAT_INTEGER_MULTIPLIER;
     if lat_val < 0 {
         lat_val = 0
     } else if lat_val >= 2 * LATITUDE_MAX as i64 * LAT_INTEGER_MULTIPLIER {
         lat_val = 2 * LATITUDE_MAX as i64 * LAT_INTEGER_MULTIPLIER - 1;
     }
 
-    let mut lng_val = (lng * LNG_INTEGER_MULTIPLIER as f64).round() as i64;
+    let mut lng_val = (lng * LNG_INTEGER_MULTIPLIER as f64).floor() as i64;
     lng_val += LONGITUDE_MAX as i64 * LNG_INTEGER_MULTIPLIER;
     if lng_val < 0 {
         lng_val = lng_val % (2 * LONGITUDE_MAX as i64 * LNG_INTEGER_MULTIPLIER)
@@ -131,15 +131,15 @@ pub fn point_to_integers(pt: Point<f64>) -> (i64, i64) {
 /// 11 or 12 are probably the limit of useful codes.
 pub fn encode(pt: Point<f64>, code_length: usize) -> String {
     let (lat_val, lng_val) = point_to_integers(pt);
-    let trimmed_code_length = min(max(code_length, MIN_CODE_LENGTH), MAX_CODE_LENGTH);
 
-    encode_integers(lat_val, lng_val, trimmed_code_length)
+    encode_integers(lat_val, lng_val, code_length)
 }
 
 /// Encode an integer location into an Open Location Code.
 ///
 /// This function is only exposed for testing and should not be called directly.
-pub fn encode_integers(mut lat_val: i64, mut lng_val: i64, code_length: usize) -> String {
+pub fn encode_integers(mut lat_val: i64, mut lng_val: i64, code_length_raw: usize) -> String {
+    let code_length = min(max(code_length_raw, MIN_CODE_LENGTH), MAX_CODE_LENGTH);
     // Compute the code digits. This largely ignores the requested length - it
     // generates either a 10 digit code, or a 15 digit code, and then truncates
     // it to the requested length.

rust/tests/all_test.rs

@@ -4,7 +4,10 @@ use std::time::Instant;
 
 use csv_reader::CSVReader;
 use geo::Point;
-use open_location_code::{decode, encode, is_full, is_short, is_valid, recover_nearest, shorten};
+use open_location_code::{
+    decode, encode, encode_integers, is_full, is_short, is_valid, point_to_integers,
+    recover_nearest, shorten,
+};
 use rand::random_range;
 
 /// CSVReader is written to swallow errors; as such, we might "pass" tests because we didn't
@@ -59,18 +62,87 @@ fn decode_test() {
 #[test]
 fn encode_test() {
     let mut tested = 0;
+    let mut errors = 0;
+    // Allow a small proportion of errors due to floating point.
+    let allowed_error_rate = 0.05;
     for line in CSVReader::new("encoding.csv") {
         if line.chars().count() == 0 {
             continue;
         }
         let cols: Vec<&str> = line.split(',').collect();
         let lat = cols[0].parse::<f64>().unwrap();
         let lng = cols[1].parse::<f64>().unwrap();
-        let len = cols[2].parse::<usize>().unwrap();
-        let code = cols[3];
+        let len = cols[4].parse::<usize>().unwrap();
+        let code = cols[5];
+
+        let got = encode(Point::new(lng, lat), len);
+        if got != code {
+            errors += 1;
+            println!(
+                "encode(Point::new({}, {}), {}) want {}, got {}",
+                lng, lat, len, code, got
+            );
+        }
+
+        tested += 1;
+    }
+    assert!(
+        errors as f32 / tested as f32 <= allowed_error_rate,
+        "too many encoding errors ({})",
+        errors
+    );
+    assert!(tested > 0);
+}
+
+#[test]
+fn point_to_integers_test() {
+    let mut tested = 0;
+    for line in CSVReader::new("encoding.csv") {
+        if line.chars().count() == 0 {
+            continue;
+        }
+        let cols: Vec<&str> = line.split(',').collect();
+        let lat_deg = cols[0].parse::<f64>().unwrap();
+        let lng_deg = cols[1].parse::<f64>().unwrap();
+        let lat_int = cols[2].parse::<i64>().unwrap();
+        let lng_int = cols[3].parse::<i64>().unwrap();
+
+        let (got_lat, got_lng) = point_to_integers(Point::new(lng_deg, lat_deg));
+        assert!(
+            got_lat >= lat_int - 1 && got_lat <= lat_int,
+            "converting lat={}, want={}, got={}",
+            lat_deg,
+            lat_int,
+            got_lat
+        );
+        assert!(
+            got_lng >= lng_int - 1 && got_lng <= lng_int,
+            "converting lng={}, want={}, got={}",
+            lng_deg,
+            lng_int,
+            got_lng
+        );
+
+        tested += 1;
+    }
+    assert!(tested > 0);
+}
+
+#[test]
+fn encode_integers_test() {
+    let mut tested = 0;
+    for line in CSVReader::new("encoding.csv") {
+        if line.chars().count() == 0 {
+            continue;
+        }
+        let cols: Vec<&str> = line.split(',').collect();
+        let lat = cols[2].parse::<i64>().unwrap();
+        let lng = cols[3].parse::<i64>().unwrap();
+        let len = cols[4].parse::<usize>().unwrap();
+        let code = cols[5];
 
         assert_eq!(
-            encode(Point::new(lng, lat), len),
+            encode_integers(lat, lng, len),
             code,
             "encoding lat={},lng={},len={}",
             lat,