ICU-22528 Avoid unnecessary float division

icu4c/source/i18n/gregoimp.cpp

@@ -32,6 +32,15 @@ int64_t ClockMath::floorDivide(int64_t numerator, int64_t denominator) {
         numerator / denominator : ((numerator + 1) / denominator) - 1;
 }
 
+int32_t ClockMath::floorDivide(int32_t numerator, int32_t denominator,
+                          int32_t* remainder) {
+    auto quotient = floorDivide(numerator, denominator);
+    if (remainder != nullptr) {
+      *remainder = numerator - (quotient * denominator);
+    }
+    return quotient;
+}
+
 int32_t ClockMath::floorDivide(double numerator, int32_t denominator,
                           int32_t* remainder) {
     // For an integer n and representable ⌊x/n⌋, ⌊RN(x/n)⌋=⌊x/n⌋, where RN is

icu4c/source/i18n/gregoimp.h

@@ -62,6 +62,24 @@ class ClockMath {
      */
     static inline double floorDivide(double numerator, double denominator);
 
+    /**
+     * Divide two numbers, returning the floor of the quotient and
+     * the modulus remainder.  Unlike the built-in division, this is
+     * mathematically well-behaved.  E.g., <code>-1/4</code> => 0 and
+     * <code>-1%4</code> => -1, but <code>floorDivide(-1,4)</code> =>
+     * -1 with <code>remainder</code> => 3.  NOTE: If numerator is
+     * too large, the returned quotient may overflow.
+     * @param numerator the numerator
+     * @param denominator a divisor which must be != 0
+     * @param remainder output parameter to receive the
+     * remainder. Unlike <code>numerator % denominator</code>, this
+     * will always be non-negative, in the half-open range <code>[0,
+     * |denominator|)</code>.
+     * @return the floor of the quotient
+     */
+    static int32_t floorDivide(int32_t numerator, int32_t denominator,
+                               int32_t* remainder);
+
     /**
      * Divide two numbers, returning the floor of the quotient and
      * the modulus remainder.  Unlike the built-in division, this is