add fuzzer for cellToChildPos (#732)

* add fuzzer for cellToChildPos

* Remove assertion check

CMakeLists.txt

@@ -256,6 +256,7 @@ set(OTHER_SOURCE_FILES
     src/apps/fuzzers/fuzzerLocalIj.c
     src/apps/fuzzers/fuzzerPolygonToCells.c
     src/apps/fuzzers/fuzzerPolygonToCellsNoHoles.c
+    src/apps/fuzzers/fuzzerCellToChildPos.c
     src/apps/fuzzers/fuzzerInternalAlgos.c
     src/apps/benchmarks/benchmarkPolygonToCells.c
     src/apps/benchmarks/benchmarkPolygon.c
@@ -508,6 +509,7 @@ if(BUILD_FUZZERS)
     add_h3_fuzzer(fuzzerLocalIj src/apps/fuzzers/fuzzerLocalIj.c)
     add_h3_fuzzer(fuzzerPolygonToCells src/apps/fuzzers/fuzzerPolygonToCells.c)
     add_h3_fuzzer(fuzzerPolygonToCellsNoHoles src/apps/fuzzers/fuzzerPolygonToCellsNoHoles.c)
+    add_h3_fuzzer(fuzzerCellToChildPos src/apps/fuzzers/fuzzerCellToChildPos.c)
     if(ENABLE_REQUIRES_ALL_SYMBOLS)
         add_h3_fuzzer(fuzzerInternalAlgos src/apps/fuzzers/fuzzerInternalAlgos.c)
     endif()

src/apps/fuzzers/README.md

@@ -61,6 +61,8 @@ The public API of H3 is covered in the following fuzzers:
 | gridPathCells | [fuzzerLocalIj](./fuzzerLocalIj.c)
 | cellToLocalIj | [fuzzerLocalIj](./fuzzerLocalIj.c)
 | localIjToCell | [fuzzerLocalIj](./fuzzerLocalIj.c)
+| cellToChildPos| [fuzzerCellToChildPos](./fuzzerCellToChildPos.c)
+| childPosToCell| [fuzzerCellToChildPos](./fuzzerCellToChildPos.c)
 
 ## Internal function coverage
 

src/apps/fuzzers/fuzzerCellToChildPos.c

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2022 Uber Technologies, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/** @file
+ * @brief Fuzzer program for cellToChildPos and related functions
+ */
+
+#include <assert.h>
+
+#include "aflHarness.h"
+#include "h3api.h"
+#include "utility.h"
+
+typedef struct {
+    H3Index index;
+    int64_t childPos;
+    int res;
+} inputArgs;
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+    if (size < sizeof(inputArgs)) {
+        return 0;
+    }
+    const inputArgs *args = (const inputArgs *)data;
+
+    int64_t posOut;
+    H3_EXPORT(cellToChildPos)(args->index, args->res, &posOut);
+    H3Index cellOut;
+    H3_EXPORT(childPosToCell)(args->childPos, args->index, args->res, &cellOut);
+    return 0;
+}
+
+AFL_HARNESS_MAIN(sizeof(inputArgs));