Added fp_t division

3 files changed, 70 insertions, 6 deletions

diff --git a/include/fixed_point.h b/include/fixed_point.h
index ff8e2b3..9df6376 100644
--- a/include/fixed_point.h
+++ b/include/fixed_point.h
@@ -15,6 +15,7 @@ struct fp_t {
     fp_t operator+(const fp_t& other) const;
     fp_t operator-(const fp_t& other) const;
     fp_t operator*(const fp_t& other) const;
+    fp_t operator/(const fp_t& other) const;
     bool operator==(const fp_t& other) const;
 };
 
diff --git a/src/fixed_point.cpp b/src/fixed_point.cpp
index 847a5f7..8b4b937 100644
--- a/src/fixed_point.cpp
+++ b/src/fixed_point.cpp
@@ -1,22 +1,39 @@
 #include "fixed_point.h"
+#include <cstdlib>
+#include <cstdio>
 
 fp_t fp_t::operator+(const fp_t& other) const {
-    return {(int32_t)((uint32_t)raw + (uint32_t)other.raw)};
+    return {(std::int32_t)((std::uint32_t)raw + (std::uint32_t)other.raw)};
 }
 
 fp_t fp_t::operator-(const fp_t& other) const {
-    return {(int32_t)((uint32_t)raw - (uint32_t)other.raw)};
+    return {(std::int32_t)((std::uint32_t)raw - (std::uint32_t)other.raw)};
 }
 
 fp_t fp_t::operator*(const fp_t& other) const {
-    int32_t result;
-    int64_t temp;
-    temp = (int64_t)raw * (int64_t)other.raw;
+    std::int32_t result;
+    std::int64_t temp;
+    temp = (std::int64_t)raw * (std::int64_t)other.raw;
     temp += fp_t::K;
-    result = (int32_t)(temp >> fp_t::Q);
+    result = (std::int32_t)(temp >> fp_t::Q);
     return {result};
 }
 
+fp_t fp_t::operator/(const fp_t& other) const {
+    if (other.raw == 0) {
+        std::fprintf(stderr, "fp_t: division by zero\n");
+        std::abort();
+    }
+    std::int64_t temp = (std::int64_t)raw << fp_t::Q;
+
+    if ((temp >= 0 && other.raw >= 0) || (temp < 0 && other.raw < 0)) {
+        temp += (other.raw / 2);
+    } else {
+        temp -= (other.raw / 2);
+    }
+    return {(std::int32_t)(temp / other.raw)};
+}
+
 bool fp_t::operator==(const fp_t& other) const {
     return raw == other.raw;
 }
diff --git a/tests/test_fixed_point.cpp b/tests/test_fixed_point.cpp
index 6d1a594..8c5c269 100644
--- a/tests/test_fixed_point.cpp
+++ b/tests/test_fixed_point.cpp
@@ -50,3 +50,49 @@ TEST_CASE("fp_t multiplication drops percision under 1 ULP") {
     fp_t b = fp_t::from_raw(0);
     CHECK(a * a == b);
 }
+
+TEST_CASE("fp_t division is basic") {
+    fp_t a = fp_t::from_int(10);
+    fp_t b = fp_t::from_int(2);
+    fp_t c = fp_t::from_int(5);
+    CHECK(a / b == c);
+}
+
+TEST_CASE("fp_t division is sign-symmetric") {
+    fp_t a = fp_t::from_int(1);
+    fp_t b = fp_t::from_raw(-3);
+    fp_t neg_a = fp_t::from_raw(-a.raw);
+    fp_t neg_b = fp_t::from_raw(-b.raw);
+    CHECK(neg_a / b == a / neg_b);
+}
+
+TEST_CASE("fp_t division rounds to nearest") {
+    fp_t a = fp_t::from_int(1);
+    fp_t b = fp_t::from_int(3);
+    fp_t c = fp_t::from_raw(21845);
+    CHECK(a / b == c);
+}
+
+TEST_CASE("fp_t division handles negative operands") {
+    fp_t a = fp_t::from_int(-10);
+    fp_t b = fp_t::from_int(2);
+    fp_t c = fp_t::from_int(-5);
+    CHECK(a / b == c);
+
+    fp_t d = fp_t::from_int(10);
+    fp_t e = fp_t::from_int(-2);
+    fp_t f = fp_t::from_int(-5);
+    CHECK(d / e == f);
+
+    fp_t g = fp_t::from_int(-10);
+    fp_t h = fp_t::from_int(-2);
+    fp_t i = fp_t::from_int(5);
+    CHECK(g / h == i);
+}
+
+TEST_CASE("fp_t division truncates precision below 1 ULP") {
+    fp_t a = fp_t::from_raw(1);
+    fp_t b = fp_t::from_int(100000);
+    fp_t c = fp_t::from_raw(0);
+    CHECK(a / b == c);
+}