get_bit: Added test cases.

+ Added test cases for get_bit.
+ get_bit declared as inline function instead of static inline
  to allow for testing in test_geohash.c

geohash.c

@@ -93,9 +93,8 @@ int geohash_encode(
     return 0;
 }
 
-static inline uint8_t get_bit(uint64_t bits, uint8_t pos)
+inline uint8_t get_bit(uint64_t bits, uint8_t pos)
 {
-    // TODO: Confirm with @yinqiwen if we should instead be using [ bits & (1 << pos) ]
     return (bits >> pos) & 0x01;
 }
 

geohash.h

@@ -101,6 +101,7 @@ extern "C"
     GeoHashBits geohash_next_lefttop(GeoHashBits bits);
     GeoHashBits geohash_next_righttop(GeoHashBits bits);
 
+    inline uint8_t get_bit(uint64_t bits, uint8_t pos);
 
 #if defined(__cplusplus)
 }

test-geohash.c

@@ -1,9 +1,42 @@
 #include <time.h>
 #include <stdio.h>
+#include <assert.h>
 #include <sys/time.h>
 
 #include "geohash.h"
 
+struct Tupled {
+    uint64_t n;
+    uint8_t i;
+    uint8_t expected:1;
+} get_bit_test_cases[] = {
+    {.n = -1, .i = 3, .expected = 1},           // .n = 0b1111111111111111111111111111111111111111111111111111111111111111
+    {.n = 99, .i = 3, .expected = 0},           // .n = 0b0000000000000000000000000000000000000000000000000000000001100011
+    {.n = 512, .i = 9, .expected = 1},          // .n = 0b0000000000000000000000000000000000000000000000000000001000000000
+    {.n = 512, .i = 19, .expected = 0},         // .n = 0b0000000000000000000000000000000000000000000000000000001000000000
+    {.n = 23457162, .i = 3, .expected = 1},     // .n = 0b0000000000000000000000000000000000000001011001011110110110001010
+    {.n = 293457162, .i = 255, .expected = 0},  // .n = 0b0000000000000000000000000000000000b10001011111011100110100001010
+    {.n = 1, .i = 3, .expected = 0},            // .n = 0b0000000000000000000000000000000000000000000000000000000000000001
+    {.n = 1, .i = 0, .expected = 1},            // .n = 0b0000000000000000000000000000000000000000000000000000000000000001
+    {.n = 0, .i = 1, .expected = 0},            // .n = 0b0000000000000000000000000000000000000000000000000000000000000000
+    {.n = 0, .i = 10, .expected = 0},           // .n = 0b0000000000000000000000000000000000000000000000000000000000000000
+};
+
+void test_get_bit() {
+    uint8_t result;
+    int i, t_len = sizeof(get_bit_test_cases)/sizeof(get_bit_test_cases[0]);
+
+    struct Tupled cur;    
+
+    for (i = 0; i < t_len; ++i) {
+        cur = get_bit_test_cases[i];
+        result = get_bit(cur.n, cur.i); 
+        assert(cur.expected == result);
+    }
+
+    printf("Passed test_get_bit\n");
+}
+
 uint64_t get_current_epoch_millis()
 {
     struct timeval timeValue;
@@ -116,7 +149,9 @@ int test_2()
 
     return 0;
 }
+
 int main() {
+    test_get_bit();
     test_1();
     test_2();
     return 0;