ICU-22479 Improve collator_compare_fuzzer

See #2574

icu4c/source/test/fuzzer/collator_compare_fuzzer.cpp

@@ -1,6 +1,7 @@
 // © 2019 and later: Unicode, Inc. and others.
 // License & terms of use: http://www.unicode.org/copyright.html
 
+#include <array>
 #include <cstring>
 
 #include "fuzzer_utils.h"
@@ -10,23 +11,41 @@
 
 IcuEnvironment* env = new IcuEnvironment();
 
+static const std::array<icu::Collator::ECollationStrength, 5> kStrength = {
+    icu::Collator::PRIMARY,
+    icu::Collator::SECONDARY,
+    icu::Collator::TERTIARY,
+    icu::Collator::QUATERNARY,
+    icu::Collator::IDENTICAL
+};
+
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   UErrorCode status = U_ZERO_ERROR;
 
-  if (size < 2)
+  uint16_t rnd16;
+
+  if (size < 2 + sizeof(rnd16))
     return 0;
 
+  std::memcpy(&rnd16, data, sizeof(rnd16));
+  size -= sizeof(rnd16);
+  data += sizeof(rnd16);
+  icu::Collator::ECollationStrength strength = kStrength[rnd16 % kStrength.size()];
+  const icu::Locale& locale = GetRandomLocale(rnd16 / kStrength.size());
+
   std::unique_ptr<char16_t> compbuff1(new char16_t[size/4]);
   std::memcpy(compbuff1.get(), data, (size/4)*2);
   data = data + size/2;
   std::unique_ptr<char16_t> compbuff2(new char16_t[size/4]);
   std::memcpy(compbuff2.get(), data, (size/4)*2);
 
+
   icu::LocalPointer<icu::Collator> fuzzCollator(
-      icu::Collator::createInstance(icu::Locale::getUS(), status), status);
+      icu::Collator::createInstance(locale, status), status);
   if (U_FAILURE(status))
     return 0;
-  fuzzCollator->setStrength(icu::Collator::TERTIARY);
+
+  fuzzCollator->setStrength(strength);
 
   fuzzCollator->compare(compbuff1.get(), size/4,
                         compbuff2.get(), size/4);