Clean regex fuzzer API

Introduces a class to clearly identify the interface of the mutation
functions used during regex-based fuzzing.

Bug: None

Change-Id: Ia6d125227cffc1c0b8944764c4e21825fd31d5cd
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/96360
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Alastair Donaldson <allydonaldson@googlemail.com>

src/tint/fuzzers/tint_regex_fuzzer/fuzzer.cc

@@ -64,39 +64,40 @@ extern "C" size_t LLVMFuzzerCustomMutator(uint8_t* data,
     MutationKind mutation_kind = static_cast<MutationKind>(
         generator.GetUInt32(static_cast<uint32_t>(MutationKind::kNumMutationKinds)));
 
+    WgslMutator mutator(generator);
     switch (mutation_kind) {
         case MutationKind::kSwapIntervals:
-            if (!SwapRandomIntervals(delimiter, wgsl_code, generator)) {
+            if (!mutator.SwapRandomIntervals(delimiter, wgsl_code)) {
                 return 0;
             }
             break;
 
         case MutationKind::kDeleteInterval:
-            if (!DeleteRandomInterval(delimiter, wgsl_code, generator)) {
+            if (!mutator.DeleteRandomInterval(delimiter, wgsl_code)) {
                 return 0;
             }
             break;
 
         case MutationKind::kDuplicateInterval:
-            if (!DuplicateRandomInterval(delimiter, wgsl_code, generator)) {
+            if (!mutator.DuplicateRandomInterval(delimiter, wgsl_code)) {
                 return 0;
             }
             break;
 
         case MutationKind::kReplaceIdentifier:
-            if (!ReplaceRandomIdentifier(wgsl_code, generator)) {
+            if (!mutator.ReplaceRandomIdentifier(wgsl_code)) {
                 return 0;
             }
             break;
 
         case MutationKind::kReplaceLiteral:
-            if (!ReplaceRandomIntLiteral(wgsl_code, generator)) {
+            if (!mutator.ReplaceRandomIntLiteral(wgsl_code)) {
                 return 0;
             }
             break;
 
         case MutationKind::kInsertReturnStatement:
-            if (!InsertReturnStatement(wgsl_code, generator)) {
+            if (!mutator.InsertReturnStatement(wgsl_code)) {
                 return 0;
             }
             break;

src/tint/fuzzers/tint_regex_fuzzer/regex_fuzzer_tests.cc

@@ -21,26 +21,44 @@
 namespace tint::fuzzers::regex_fuzzer {
 namespace {
 
+class WgslMutatorTest : public WgslMutator {
+  public:
+    explicit WgslMutatorTest(RandomGenerator& generator) : WgslMutator(generator) {}
+
+    using WgslMutator::DeleteInterval;
+    using WgslMutator::DuplicateInterval;
+    using WgslMutator::FindClosingBrace;
+    using WgslMutator::GetFunctionBodyPositions;
+    using WgslMutator::GetIdentifiers;
+    using WgslMutator::GetIntLiterals;
+    using WgslMutator::ReplaceRegion;
+    using WgslMutator::SwapIntervals;
+};
+
 // Swaps two non-consecutive regions in the edge
 TEST(SwapRegionsTest, SwapIntervalsEdgeNonConsecutive) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = ";region1;", R2 = ";regionregion2;", R3 = ";regionregionregion3;";
     std::string all_regions = R1 + R2 + R3;
 
     // this call should swap R1 with R3.
-    SwapIntervals(0, R1.length(), R1.length() + R2.length(), R3.length(), all_regions);
+    mutator.SwapIntervals(0, R1.length(), R1.length() + R2.length(), R3.length(), all_regions);
 
     ASSERT_EQ(R3 + R2 + R1, all_regions);
 }
 
 // Swaps two non-consecutive regions not in the edge
 TEST(SwapRegionsTest, SwapIntervalsNonConsecutiveNonEdge) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = ";region1;", R2 = ";regionregion2;", R3 = ";regionregionregion3;",
                 R4 = ";regionregionregionregion4;", R5 = ";regionregionregionregionregion5;";
     std::string all_regions = R1 + R2 + R3 + R4 + R5;
 
     // this call should swap R2 with R4.
-    SwapIntervals(R1.length(), R2.length(), R1.length() + R2.length() + R3.length(), R4.length(),
+    mutator.SwapIntervals(R1.length(), R2.length(), R1.length() + R2.length() + R3.length(),
-                  all_regions);
+                          R4.length(), all_regions);
 
     ASSERT_EQ(R1 + R4 + R3 + R2 + R5, all_regions);
 }
@@ -48,12 +66,15 @@ TEST(SwapRegionsTest, SwapIntervalsNonConsecutiveNonEdge) {
 // Swaps two consecutive regions not in the edge (sorrounded by other
 // regions)
 TEST(SwapRegionsTest, SwapIntervalsConsecutiveEdge) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = ";region1;", R2 = ";regionregion2;", R3 = ";regionregionregion3;",
                 R4 = ";regionregionregionregion4;", R5 = ";regionregionregionregionregion5;";
     std::string all_regions = R1 + R2 + R3 + R4;
 
     // this call should swap R2 with R3.
-    SwapIntervals(R1.length(), R2.length(), R1.length() + R2.length(), R3.length(), all_regions);
+    mutator.SwapIntervals(R1.length(), R2.length(), R1.length() + R2.length(), R3.length(),
+                          all_regions);
 
     ASSERT_EQ(R1 + R3 + R2 + R4, all_regions);
 }
@@ -61,113 +82,137 @@ TEST(SwapRegionsTest, SwapIntervalsConsecutiveEdge) {
 // Swaps two consecutive regions not in the edge (not sorrounded by other
 // regions)
 TEST(SwapRegionsTest, SwapIntervalsConsecutiveNonEdge) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = ";region1;", R2 = ";regionregion2;", R3 = ";regionregionregion3;",
                 R4 = ";regionregionregionregion4;", R5 = ";regionregionregionregionregion5;";
     std::string all_regions = R1 + R2 + R3 + R4 + R5;
 
     // this call should swap R4 with R5.
-    SwapIntervals(R1.length() + R2.length() + R3.length(), R4.length(),
+    mutator.SwapIntervals(R1.length() + R2.length() + R3.length(), R4.length(),
-                  R1.length() + R2.length() + R3.length() + R4.length(), R5.length(), all_regions);
+                          R1.length() + R2.length() + R3.length() + R4.length(), R5.length(),
+                          all_regions);
 
     ASSERT_EQ(R1 + R2 + R3 + R5 + R4, all_regions);
 }
 
 // Deletes the first region.
 TEST(DeleteRegionTest, DeleteFirstRegion) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = ";region1;", R2 = ";regionregion2;", R3 = ";regionregionregion3;",
                 R4 = ";regionregionregionregion4;", R5 = ";regionregionregionregionregion5;";
     std::string all_regions = R1 + R2 + R3 + R4 + R5;
 
     // This call should delete R1.
-    DeleteInterval(0, R1.length(), all_regions);
+    mutator.DeleteInterval(0, R1.length(), all_regions);
 
     ASSERT_EQ(";" + R2 + R3 + R4 + R5, all_regions);
 }
 
 // Deletes the last region.
 TEST(DeleteRegionTest, DeleteLastRegion) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = ";region1;", R2 = ";regionregion2;", R3 = ";regionregionregion3;",
                 R4 = ";regionregionregionregion4;", R5 = ";regionregionregionregionregion5;";
     std::string all_regions = R1 + R2 + R3 + R4 + R5;
 
     // This call should delete R5.
-    DeleteInterval(R1.length() + R2.length() + R3.length() + R4.length(), R5.length(), all_regions);
+    mutator.DeleteInterval(R1.length() + R2.length() + R3.length() + R4.length(), R5.length(),
+                           all_regions);
 
     ASSERT_EQ(R1 + R2 + R3 + R4 + ";", all_regions);
 }
 
 // Deletes the middle region.
 TEST(DeleteRegionTest, DeleteMiddleRegion) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = ";region1;", R2 = ";regionregion2;", R3 = ";regionregionregion3;",
                 R4 = ";regionregionregionregion4;", R5 = ";regionregionregionregionregion5;";
     std::string all_regions = R1 + R2 + R3 + R4 + R5;
 
     // This call should delete R3.
-    DeleteInterval(R1.length() + R2.length(), R3.length(), all_regions);
+    mutator.DeleteInterval(R1.length() + R2.length(), R3.length(), all_regions);
 
     ASSERT_EQ(R1 + R2 + ";" + R4 + R5, all_regions);
 }
 
 TEST(InsertRegionTest, InsertRegionTest1) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = ";region1;", R2 = ";regionregion2;", R3 = ";regionregionregion3;",
                 R4 = ";regionregionregionregion4;", R5 = ";regionregionregionregionregion5;";
     std::string all_regions = R1 + R2 + R3 + R4 + R5;
 
     // This call should insert R2 after R4.
-    DuplicateInterval(R1.length(), R2.length(),
+    mutator.DuplicateInterval(R1.length(), R2.length(),
-                      R1.length() + R2.length() + R3.length() + R4.length() - 1, all_regions);
+                              R1.length() + R2.length() + R3.length() + R4.length() - 1,
+                              all_regions);
 
     ASSERT_EQ(R1 + R2 + R3 + R4 + R2.substr(1, R2.size() - 1) + R5, all_regions);
 }
 
 TEST(InsertRegionTest, InsertRegionTest2) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = ";region1;", R2 = ";regionregion2;", R3 = ";regionregionregion3;",
                 R4 = ";regionregionregionregion4;", R5 = ";regionregionregionregionregion5;";
 
     std::string all_regions = R1 + R2 + R3 + R4 + R5;
 
     // This call should insert R3 after R1.
-    DuplicateInterval(R1.length() + R2.length(), R3.length(), R1.length() - 1, all_regions);
+    mutator.DuplicateInterval(R1.length() + R2.length(), R3.length(), R1.length() - 1, all_regions);
 
     ASSERT_EQ(R1 + R3.substr(1, R3.length() - 1) + R2 + R3 + R4 + R5, all_regions);
 }
 
 TEST(InsertRegionTest, InsertRegionTest3) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = ";region1;", R2 = ";regionregion2;", R3 = ";regionregionregion3;",
                 R4 = ";regionregionregionregion4;", R5 = ";regionregionregionregionregion5;";
 
     std::string all_regions = R1 + R2 + R3 + R4 + R5;
 
     // This call should insert R2 after R5.
-    DuplicateInterval(R1.length(), R2.length(), all_regions.length() - 1, all_regions);
+    mutator.DuplicateInterval(R1.length(), R2.length(), all_regions.length() - 1, all_regions);
 
     ASSERT_EQ(R1 + R2 + R3 + R4 + R5 + R2.substr(1, R2.length() - 1), all_regions);
 }
 
 TEST(ReplaceIdentifierTest, ReplaceIdentifierTest1) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = "|region1|", R2 = "; region2;", R3 = "---------region3---------",
                 R4 = "++region4++", R5 = "***region5***";
     std::string all_regions = R1 + R2 + R3 + R4 + R5;
 
     // Replaces R3 with R1.
-    ReplaceRegion(0, R1.length(), R1.length() + R2.length(), R3.length(), all_regions);
+    mutator.ReplaceRegion(0, R1.length(), R1.length() + R2.length(), R3.length(), all_regions);
 
     ASSERT_EQ(R1 + R2 + R1 + R4 + R5, all_regions);
 }
 
 TEST(ReplaceIdentifierTest, ReplaceIdentifierTest2) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string R1 = "|region1|", R2 = "; region2;", R3 = "---------region3---------",
                 R4 = "++region4++", R5 = "***region5***";
     std::string all_regions = R1 + R2 + R3 + R4 + R5;
 
     // Replaces R5 with R3.
-    ReplaceRegion(R1.length() + R2.length(), R3.length(),
+    mutator.ReplaceRegion(R1.length() + R2.length(), R3.length(),
-                  R1.length() + R2.length() + R3.length() + R4.length(), R5.length(), all_regions);
+                          R1.length() + R2.length() + R3.length() + R4.length(), R5.length(),
+                          all_regions);
 
     ASSERT_EQ(R1 + R2 + R3 + R4 + R3, all_regions);
 }
 
 TEST(GetIdentifierTest, GetIdentifierTest1) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string wgsl_code =
         R"(fn clamp_0acf8f() {
         var res: vec2<f32> = clamp(vec2<f32>(), vec2<f32>(), vec2<f32>());
@@ -187,7 +232,7 @@ TEST(GetIdentifierTest, GetIdentifierTest1) {
         clamp_0acf8f();
       })";
 
-    std::vector<std::pair<size_t, size_t>> identifiers_pos = GetIdentifiers(wgsl_code);
+    std::vector<std::pair<size_t, size_t>> identifiers_pos = mutator.GetIdentifiers(wgsl_code);
 
     std::vector<std::pair<size_t, size_t>> ground_truth = {
         std::make_pair(3, 12),   std::make_pair(28, 3),  std::make_pair(37, 4),
@@ -204,6 +249,8 @@ TEST(GetIdentifierTest, GetIdentifierTest1) {
 }
 
 TEST(TestGetLiteralsValues, TestGetLiteralsValues1) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string wgsl_code =
         R"(fn clamp_0acf8f() {
         var res: vec2<f32> = clamp(vec2<f32>(), vec2<f32>(), vec2<f32>());
@@ -227,7 +274,7 @@ TEST(TestGetLiteralsValues, TestGetLiteralsValues1) {
       foo_1 = 5 + 7;
       var foo_3 : i32 = -20;)";
 
-    std::vector<std::pair<size_t, size_t>> literals_pos = GetIntLiterals(wgsl_code);
+    std::vector<std::pair<size_t, size_t>> literals_pos = mutator.GetIntLiterals(wgsl_code);
 
     std::vector<std::string> ground_truth = {"3", "10", "5", "7", "-20"};
 
@@ -241,6 +288,8 @@ TEST(TestGetLiteralsValues, TestGetLiteralsValues1) {
 }
 
 TEST(InsertReturnTest, FindClosingBrace) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string wgsl_code =
         R"(fn clamp_0acf8f() {
         if(false){
@@ -269,7 +318,7 @@ TEST(InsertReturnTest, FindClosingBrace) {
         var foo_3 : i32 = -20;
       )";
     size_t opening_bracket_pos = 18;
-    size_t closing_bracket_pos = FindClosingBrace(opening_bracket_pos, wgsl_code);
+    size_t closing_bracket_pos = mutator.FindClosingBrace(opening_bracket_pos, wgsl_code);
 
     // The -1 is needed since the function body starts after the left bracket.
     std::string function_body =
@@ -286,6 +335,8 @@ TEST(InsertReturnTest, FindClosingBrace) {
 }
 
 TEST(InsertReturnTest, FindClosingBraceFailing) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string wgsl_code =
         R"(fn clamp_0acf8f() {
       // This comment } causes the test to fail.
@@ -314,7 +365,7 @@ TEST(InsertReturnTest, FindClosingBraceFailing) {
       foo_1 = 5 + 7;
       var foo_3 : i32 = -20;)";
     size_t opening_bracket_pos = 18;
-    size_t closing_bracket_pos = FindClosingBrace(opening_bracket_pos, wgsl_code);
+    size_t closing_bracket_pos = mutator.FindClosingBrace(opening_bracket_pos, wgsl_code);
 
     // The -1 is needed since the function body starts after the left bracket.
     std::string function_body =
@@ -330,6 +381,8 @@ TEST(InsertReturnTest, FindClosingBraceFailing) {
 }
 
 TEST(TestInsertReturn, TestInsertReturn1) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string wgsl_code =
         R"(fn clamp_0acf8f() {
         var res: vec2<f32> = clamp(vec2<f32>(), vec2<f32>(), vec2<f32>());
@@ -390,6 +443,8 @@ TEST(TestInsertReturn, TestInsertReturn1) {
 }
 
 TEST(TestInsertReturn, TestFunctionPositions) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string wgsl_code =
         R"(fn clamp_0acf8f() {
           var res: vec2<f32> = clamp(vec2<f32>(), vec2<f32>(), vec2<f32>());
@@ -418,12 +473,14 @@ TEST(TestInsertReturn, TestFunctionPositions) {
         foo_1 = 5 + 7;
         var foo_3 : i32 = -20;)";
 
-    std::vector<size_t> function_positions = GetFunctionBodyPositions(wgsl_code);
+    std::vector<size_t> function_positions = mutator.GetFunctionBodyPositions(wgsl_code);
     std::vector<size_t> expected_positions = {180, 586};
     ASSERT_EQ(expected_positions, function_positions);
 }
 
 TEST(TestInsertReturn, TestMissingSemicolon) {
+    RandomGenerator generator(0);
+    WgslMutatorTest mutator(generator);
     std::string wgsl_code =
         R"(fn clamp_0acf8f() {
           var res: vec2<f32> = clamp(vec2<f32>(), vec2<f32>(), vec2<f32>())
@@ -452,8 +509,7 @@ TEST(TestInsertReturn, TestMissingSemicolon) {
         foo_1 = 5 + 7;
         var foo_3 : i32 = -20;)";
 
-    RandomGenerator generator(0);
+    mutator.InsertReturnStatement(wgsl_code);
-    InsertReturnStatement(wgsl_code, generator);
 
     // No semicolons found in the function's body, so wgsl_code
     // should remain unchanged.

src/tint/fuzzers/tint_regex_fuzzer/wgsl_mutator.cc

@@ -26,7 +26,9 @@
 
 namespace tint::fuzzers::regex_fuzzer {
 
-std::vector<size_t> FindDelimiterIndices(const std::string& delimiter,
+WgslMutator::WgslMutator(RandomGenerator& generator) : generator_(generator) {}
+
+std::vector<size_t> WgslMutator::FindDelimiterIndices(const std::string& delimiter,
                                                       const std::string& wgsl_code) {
     std::vector<size_t> result;
     for (size_t pos = wgsl_code.find(delimiter, 0); pos != std::string::npos;
@@ -37,7 +39,7 @@ std::vector<size_t> FindDelimiterIndices(const std::string& delimiter,
     return result;
 }
 
-std::vector<std::pair<size_t, size_t>> GetIdentifiers(const std::string& wgsl_code) {
+std::vector<std::pair<size_t, size_t>> WgslMutator::GetIdentifiers(const std::string& wgsl_code) {
     std::vector<std::pair<size_t, size_t>> result;
 
     // This regular expression works by looking for a character that
@@ -61,7 +63,7 @@ std::vector<std::pair<size_t, size_t>> GetIdentifiers(const std::string& wgsl_co
     return result;
 }
 
-std::vector<std::pair<size_t, size_t>> GetIntLiterals(const std::string& s) {
+std::vector<std::pair<size_t, size_t>> WgslMutator::GetIntLiterals(const std::string& s) {
     std::vector<std::pair<size_t, size_t>> result;
 
     // Looks for integer literals in decimal or hexadecimal form.
@@ -83,7 +85,7 @@ std::vector<std::pair<size_t, size_t>> GetIntLiterals(const std::string& s) {
     return result;
 }
 
-size_t FindClosingBrace(size_t opening_bracket_pos, const std::string& wgsl_code) {
+size_t WgslMutator::FindClosingBrace(size_t opening_bracket_pos, const std::string& wgsl_code) {
     size_t open_bracket_count = 1;
     size_t pos = opening_bracket_pos + 1;
     while (open_bracket_count >= 1 && pos < wgsl_code.size()) {
@@ -97,7 +99,7 @@ size_t FindClosingBrace(size_t opening_bracket_pos, const std::string& wgsl_code
     return (pos == wgsl_code.size() && open_bracket_count >= 1) ? 0 : pos - 1;
 }
 
-std::vector<size_t> GetFunctionBodyPositions(const std::string& wgsl_code) {
+std::vector<size_t> WgslMutator::GetFunctionBodyPositions(const std::string& wgsl_code) {
     // Finds all the functions with a non-void return value.
     std::regex function_regex("fn.*?->.*?\\{");
     std::smatch match;
@@ -113,7 +115,7 @@ std::vector<size_t> GetFunctionBodyPositions(const std::string& wgsl_code) {
     return result;
 }
 
-bool InsertReturnStatement(std::string& wgsl_code, RandomGenerator& generator) {
+bool WgslMutator::InsertReturnStatement(std::string& wgsl_code) {
     std::vector<size_t> function_body_positions = GetFunctionBodyPositions(wgsl_code);
 
     // No function was found in wgsl_code.
@@ -123,7 +125,7 @@ bool InsertReturnStatement(std::string& wgsl_code, RandomGenerator& generator) {
 
     // Pick a random function's opening bracket, find the corresponding closing
     // bracket, and find a semi-colon within the function body.
-    size_t left_bracket_pos = generator.GetRandomElement(function_body_positions);
+    size_t left_bracket_pos = generator_.GetRandomElement(function_body_positions);
 
     size_t right_bracket_pos = FindClosingBrace(left_bracket_pos, wgsl_code);
 
@@ -141,14 +143,14 @@ bool InsertReturnStatement(std::string& wgsl_code, RandomGenerator& generator) {
         return false;
     }
 
-    size_t semicolon_position = generator.GetRandomElement(semicolon_positions);
+    size_t semicolon_position = generator_.GetRandomElement(semicolon_positions);
 
     // Get all identifiers and integer literals to use as potential return values.
     std::vector<std::pair<size_t, size_t>> identifiers = GetIdentifiers(wgsl_code);
     auto return_values = identifiers;
     std::vector<std::pair<size_t, size_t>> int_literals = GetIntLiterals(wgsl_code);
     return_values.insert(return_values.end(), int_literals.begin(), int_literals.end());
-    std::pair<size_t, size_t> return_value = generator.GetRandomElement(return_values);
+    std::pair<size_t, size_t> return_value = generator_.GetRandomElement(return_values);
     std::string return_statement =
         "return " + wgsl_code.substr(return_value.first, return_value.second) + ";";
 
@@ -157,7 +159,7 @@ bool InsertReturnStatement(std::string& wgsl_code, RandomGenerator& generator) {
     return true;
 }
 
-void SwapIntervals(size_t idx1,
+void WgslMutator::SwapIntervals(size_t idx1,
                                 size_t reg1_len,
                                 size_t idx2,
                                 size_t reg2_len,
@@ -172,16 +174,19 @@ void SwapIntervals(size_t idx1,
     wgsl_code.replace(idx1 + 1, region_1.size(), region_2);
 }
 
-void DeleteInterval(size_t idx1, size_t reg_len, std::string& wgsl_code) {
+void WgslMutator::DeleteInterval(size_t idx1, size_t reg_len, std::string& wgsl_code) {
     wgsl_code.erase(idx1 + 1, reg_len - 1);
 }
 
-void DuplicateInterval(size_t idx1, size_t reg1_len, size_t idx2, std::string& wgsl_code) {
+void WgslMutator::DuplicateInterval(size_t idx1,
+                                    size_t reg1_len,
+                                    size_t idx2,
+                                    std::string& wgsl_code) {
     std::string region = wgsl_code.substr(idx1 + 1, reg1_len - 1);
     wgsl_code.insert(idx2 + 1, region);
 }
 
-void ReplaceRegion(size_t idx1,
+void WgslMutator::ReplaceRegion(size_t idx1,
                                 size_t id1_len,
                                 size_t idx2,
                                 size_t id2_len,
@@ -191,7 +196,7 @@ void ReplaceRegion(size_t idx1,
     wgsl_code.replace(idx2, region_2.size(), region_1);
 }
 
-void ReplaceInterval(size_t start_index,
+void WgslMutator::ReplaceInterval(size_t start_index,
                                   size_t length,
                                   std::string replacement_text,
                                   std::string& wgsl_code) {
@@ -199,9 +204,7 @@ void ReplaceInterval(size_t start_index,
     wgsl_code.replace(start_index, length, replacement_text);
 }
 
-bool SwapRandomIntervals(const std::string& delimiter,
+bool WgslMutator::SwapRandomIntervals(const std::string& delimiter, std::string& wgsl_code) {
-                         std::string& wgsl_code,
-                         RandomGenerator& generator) {
     std::vector<size_t> delimiter_positions = FindDelimiterIndices(delimiter, wgsl_code);
 
     // Need to have at least 3 indices.
@@ -212,12 +215,12 @@ bool SwapRandomIntervals(const std::string& delimiter,
     // Choose indices:
     //   interval_1_start < interval_1_end <= interval_2_start < interval_2_end
     uint32_t interval_1_start =
-        generator.GetUInt32(static_cast<uint32_t>(delimiter_positions.size()) - 2u);
+        generator_.GetUInt32(static_cast<uint32_t>(delimiter_positions.size()) - 2u);
-    uint32_t interval_1_end = generator.GetUInt32(
+    uint32_t interval_1_end = generator_.GetUInt32(
         interval_1_start + 1u, static_cast<uint32_t>(delimiter_positions.size()) - 1u);
-    uint32_t interval_2_start =
+    uint32_t interval_2_start = generator_.GetUInt32(
-        generator.GetUInt32(interval_1_end, static_cast<uint32_t>(delimiter_positions.size()) - 1u);
+        interval_1_end, static_cast<uint32_t>(delimiter_positions.size()) - 1u);
-    uint32_t interval_2_end = generator.GetUInt32(
+    uint32_t interval_2_end = generator_.GetUInt32(
         interval_2_start + 1u, static_cast<uint32_t>(delimiter_positions.size()));
 
     SwapIntervals(delimiter_positions[interval_1_start],
@@ -229,9 +232,7 @@ bool SwapRandomIntervals(const std::string& delimiter,
     return true;
 }
 
-bool DeleteRandomInterval(const std::string& delimiter,
+bool WgslMutator::DeleteRandomInterval(const std::string& delimiter, std::string& wgsl_code) {
-                          std::string& wgsl_code,
-                          RandomGenerator& generator) {
     std::vector<size_t> delimiter_positions = FindDelimiterIndices(delimiter, wgsl_code);
 
     // Need to have at least 2 indices.
@@ -240,9 +241,9 @@ bool DeleteRandomInterval(const std::string& delimiter,
     }
 
     uint32_t interval_start =
-        generator.GetUInt32(static_cast<uint32_t>(delimiter_positions.size()) - 1u);
+        generator_.GetUInt32(static_cast<uint32_t>(delimiter_positions.size()) - 1u);
-    uint32_t interval_end =
+    uint32_t interval_end = generator_.GetUInt32(interval_start + 1u,
-        generator.GetUInt32(interval_start + 1u, static_cast<uint32_t>(delimiter_positions.size()));
+                                                 static_cast<uint32_t>(delimiter_positions.size()));
 
     DeleteInterval(delimiter_positions[interval_start],
                    delimiter_positions[interval_end] - delimiter_positions[interval_start],
@@ -251,9 +252,7 @@ bool DeleteRandomInterval(const std::string& delimiter,
     return true;
 }
 
-bool DuplicateRandomInterval(const std::string& delimiter,
+bool WgslMutator::DuplicateRandomInterval(const std::string& delimiter, std::string& wgsl_code) {
-                             std::string& wgsl_code,
-                             RandomGenerator& generator) {
     std::vector<size_t> delimiter_positions = FindDelimiterIndices(delimiter, wgsl_code);
 
     // Need to have at least 2 indices
@@ -262,11 +261,11 @@ bool DuplicateRandomInterval(const std::string& delimiter,
     }
 
     uint32_t interval_start =
-        generator.GetUInt32(static_cast<uint32_t>(delimiter_positions.size()) - 1u);
+        generator_.GetUInt32(static_cast<uint32_t>(delimiter_positions.size()) - 1u);
-    uint32_t interval_end =
+    uint32_t interval_end = generator_.GetUInt32(interval_start + 1u,
-        generator.GetUInt32(interval_start + 1u, static_cast<uint32_t>(delimiter_positions.size()));
+                                                 static_cast<uint32_t>(delimiter_positions.size()));
     uint32_t duplication_point =
-        generator.GetUInt32(static_cast<uint32_t>(delimiter_positions.size()));
+        generator_.GetUInt32(static_cast<uint32_t>(delimiter_positions.size()));
 
     DuplicateInterval(delimiter_positions[interval_start],
                       delimiter_positions[interval_end] - delimiter_positions[interval_start],
@@ -275,7 +274,7 @@ bool DuplicateRandomInterval(const std::string& delimiter,
     return true;
 }
 
-bool ReplaceRandomIdentifier(std::string& wgsl_code, RandomGenerator& generator) {
+bool WgslMutator::ReplaceRandomIdentifier(std::string& wgsl_code) {
     std::vector<std::pair<size_t, size_t>> identifiers = GetIdentifiers(wgsl_code);
 
     // Need at least 2 identifiers
@@ -283,12 +282,12 @@ bool ReplaceRandomIdentifier(std::string& wgsl_code, RandomGenerator& generator)
         return false;
     }
 
-    uint32_t id1_index = generator.GetUInt32(static_cast<uint32_t>(identifiers.size()));
+    uint32_t id1_index = generator_.GetUInt32(static_cast<uint32_t>(identifiers.size()));
-    uint32_t id2_index = generator.GetUInt32(static_cast<uint32_t>(identifiers.size()));
+    uint32_t id2_index = generator_.GetUInt32(static_cast<uint32_t>(identifiers.size()));
 
     // The two identifiers must be different
     while (id1_index == id2_index) {
-        id2_index = generator.GetUInt32(static_cast<uint32_t>(identifiers.size()));
+        id2_index = generator_.GetUInt32(static_cast<uint32_t>(identifiers.size()));
     }
 
     ReplaceRegion(identifiers[id1_index].first, identifiers[id1_index].second,
@@ -297,7 +296,7 @@ bool ReplaceRandomIdentifier(std::string& wgsl_code, RandomGenerator& generator)
     return true;
 }
 
-bool ReplaceRandomIntLiteral(std::string& wgsl_code, RandomGenerator& generator) {
+bool WgslMutator::ReplaceRandomIntLiteral(std::string& wgsl_code) {
     std::vector<std::pair<size_t, size_t>> literals = GetIntLiterals(wgsl_code);
 
     // Need at least one integer literal
@@ -305,13 +304,13 @@ bool ReplaceRandomIntLiteral(std::string& wgsl_code, RandomGenerator& generator)
         return false;
     }
 
-    uint32_t literal_index = generator.GetUInt32(static_cast<uint32_t>(literals.size()));
+    uint32_t literal_index = generator_.GetUInt32(static_cast<uint32_t>(literals.size()));
 
     // INT_MAX = 2147483647, INT_MIN = -2147483648
     std::vector<std::string> boundary_values = {"2147483647", "-2147483648", "1",
                                                 "-1",         "0",           "4294967295"};
 
-    uint32_t boundary_index = generator.GetUInt32(static_cast<uint32_t>(boundary_values.size()));
+    uint32_t boundary_index = generator_.GetUInt32(static_cast<uint32_t>(boundary_values.size()));
 
     ReplaceInterval(literals[literal_index].first, literals[literal_index].second,
                     boundary_values[boundary_index], wgsl_code);

src/tint/fuzzers/tint_regex_fuzzer/wgsl_mutator.h

@@ -23,27 +23,70 @@
 
 namespace tint::fuzzers::regex_fuzzer {
 
-/// A function that given a delimiter, returns a vector that contains
+/// Class encapsulating code for regex-based mutation of WGSL shaders.
-/// all the positions of the delimiter in the WGSL code.
+class WgslMutator {
-/// @param delimiter - the delimiter of the enclosed region.
+  public:
+    /// Constructor
+    /// @param generator - pseudo-random generator to use in mutator
+    explicit WgslMutator(RandomGenerator& generator);
+
+    /// A function that, given WGSL-like string and a delimiter,
+    /// generates another WGSL-like string by picking two random regions
+    /// enclosed by the delimiter and swapping them.
+    /// @param delimiter - the delimiter that will be used to find enclosed regions.
     /// @param wgsl_code - the initial string (WGSL code) that will be mutated.
-/// @return a vector with the positions of the delimiter in the WGSL code.
+    /// @return true if a swap happened or false otherwise.
-std::vector<size_t> FindDelimiterIndices(const std::string& delimiter,
+    bool SwapRandomIntervals(const std::string& delimiter, std::string& wgsl_code);
-                                         const std::string& wgsl_code);
 
-/// A function that finds all the identifiers in a WGSL-like string.
+    /// A function that, given a WGSL-like string and a delimiter,
-/// @param wgsl_code - the WGSL-like string where the identifiers will be found.
+    /// generates another WGSL-like string by deleting a random
-/// @return a vector with the positions and the length of all the
+    /// region enclosed by the delimiter.
-/// identifiers in wgsl_code.
+    /// @param delimiter - the delimiter that will be used to find enclosed regions.
-std::vector<std::pair<size_t, size_t>> GetIdentifiers(const std::string& wgsl_code);
+    /// @param wgsl_code - the initial string (WGSL code) that will be mutated.
+    /// @return true if a deletion happened or false otherwise.
+    bool DeleteRandomInterval(const std::string& delimiter, std::string& wgsl_code);
 
-/// A function that returns returns the starting position
+    /// A function that, given a WGSL-like string and a delimiter,
-/// and the length of all the integer literals in a WGSL-like string.
+    /// generates another WGSL-like string by duplicating a random
-/// @param wgsl_code - the WGSL-like string where the int literals
+    /// region enclosed by the delimiter.
-/// will be found.
+    /// @param delimiter - the delimiter that will be used to find enclosed regions.
-/// @return a vector with the starting positions and the length
+    /// @param wgsl_code - the initial string (WGSL code) that will be mutated.
-/// of all the integer literals.
+    /// @return true if a duplication happened or false otherwise.
-std::vector<std::pair<size_t, size_t>> GetIntLiterals(const std::string& wgsl_code);
+    bool DuplicateRandomInterval(const std::string& delimiter, std::string& wgsl_code);
+
+    /// Replaces a randomly-chosen identifier in wgsl_code.
+    /// @param wgsl_code - WGSL-like string where the replacement will occur.
+    /// @return true if a replacement happened or false otherwise.
+    bool ReplaceRandomIdentifier(std::string& wgsl_code);
+
+    /// Replaces the value of a randomly-chosen integer with one of
+    /// the values in the set {INT_MAX, INT_MIN, 0, -1}.
+    /// @param wgsl_code - WGSL-like string where the replacement will occur.
+    /// @return true if a replacement happened or false otherwise.
+    bool ReplaceRandomIntLiteral(std::string& wgsl_code);
+
+    /// Inserts a return statement in a randomly chosen function of a
+    /// WGSL-like string. The return value is a randomly-chosen identifier
+    /// or literal in the string.
+    /// @param wgsl_code - WGSL-like string that will be mutated.
+    /// @return true if the mutation was succesful or false otherwise.
+    bool InsertReturnStatement(std::string& wgsl_code);
+
+  protected:
+    /// Given index idx1 it delets the region of length interval_len
+    /// starting at index idx1;
+    /// @param idx1 - starting index of the first region.
+    /// @param reg_len - terminating index of the second region.
+    /// @param wgsl_code - the string where the swap will occur.
+    void DeleteInterval(size_t idx1, size_t reg_len, std::string& wgsl_code);
+
+    /// Given 2 indices, idx1, idx2, it inserts the region of length
+    /// reg1_len starting at idx1 after idx2.
+    /// @param idx1 - starting index of region.
+    /// @param reg1_len - length of the region.
+    /// @param idx2 - the position where the region will be inserted.
+    /// @param wgsl_code - the string where the swap will occur.
+    void DuplicateInterval(size_t idx1, size_t reg1_len, size_t idx2, std::string& wgsl_code);
 
     /// Finds a possible closing brace corresponding to the opening
     /// brace at position opening_bracket_pos.
@@ -62,34 +105,19 @@ size_t FindClosingBrace(size_t opening_bracket_pos, const std::string& wgsl_code
     /// wgsl_code.
     std::vector<size_t> GetFunctionBodyPositions(const std::string& wgsl_code);
 
-/// Given 4 indices, idx1, idx2, idx3 and idx4 it swaps the regions
+    /// A function that finds all the identifiers in a WGSL-like string.
-/// in the interval (idx1, idx2] with the region in the interval (idx3, idx4]
+    /// @param wgsl_code - the WGSL-like string where the identifiers will be found.
-/// in wgsl_text.
+    /// @return a vector with the positions and the length of all the
-/// @param idx1 - starting index of the first region.
+    /// identifiers in wgsl_code.
-/// @param reg1_len - length of the first region.
+    std::vector<std::pair<size_t, size_t>> GetIdentifiers(const std::string& wgsl_code);
-/// @param idx2 - starting index of the second region.
-/// @param reg2_len - length of the second region.
-/// @param wgsl_code - the string where the swap will occur.
-void SwapIntervals(size_t idx1,
-                   size_t reg1_len,
-                   size_t idx2,
-                   size_t reg2_len,
-                   std::string& wgsl_code);
 
-/// Given index idx1 it delets the region of length interval_len
+    /// A function that returns returns the starting position
-/// starting at index idx1;
+    /// and the length of all the integer literals in a WGSL-like string.
-/// @param idx1 - starting index of the first region.
+    /// @param wgsl_code - the WGSL-like string where the int literals
-/// @param reg_len - terminating index of the second region.
+    /// will be found.
-/// @param wgsl_code - the string where the swap will occur.
+    /// @return a vector with the starting positions and the length
-void DeleteInterval(size_t idx1, size_t reg_len, std::string& wgsl_code);
+    /// of all the integer literals.
-
+    std::vector<std::pair<size_t, size_t>> GetIntLiterals(const std::string& wgsl_code);
-/// Given 2 indices, idx1, idx2, it inserts the region of length
-/// reg1_len starting at idx1 after idx2.
-/// @param idx1 - starting index of region.
-/// @param reg1_len - length of the region.
-/// @param idx2 - the position where the region will be inserted.
-/// @param wgsl_code - the string where the swap will occur.
-void DuplicateInterval(size_t idx1, size_t reg1_len, size_t idx2, std::string& wgsl_code);
 
     /// Replaces a region of a WGSL-like string of length id2_len starting
     /// at position idx2 with a region of length id1_len starting at
@@ -105,6 +133,29 @@ void ReplaceRegion(size_t idx1,
                        size_t id2_len,
                        std::string& wgsl_code);
 
+    /// Given 4 indices, idx1, idx2, idx3 and idx4 it swaps the regions
+    /// in the interval (idx1, idx2] with the region in the interval (idx3, idx4]
+    /// in wgsl_text.
+    /// @param idx1 - starting index of the first region.
+    /// @param reg1_len - length of the first region.
+    /// @param idx2 - starting index of the second region.
+    /// @param reg2_len - length of the second region.
+    /// @param wgsl_code - the string where the swap will occur.
+    void SwapIntervals(size_t idx1,
+                       size_t reg1_len,
+                       size_t idx2,
+                       size_t reg2_len,
+                       std::string& wgsl_code);
+
+  private:
+    /// A function that given a delimiter, returns a vector that contains
+    /// all the positions of the delimiter in the WGSL code.
+    /// @param delimiter - the delimiter of the enclosed region.
+    /// @param wgsl_code - the initial string (WGSL code) that will be mutated.
+    /// @return a vector with the positions of the delimiter in the WGSL code.
+    std::vector<size_t> FindDelimiterIndices(const std::string& delimiter,
+                                             const std::string& wgsl_code);
+
     /// Replaces an interval of length `length` starting at start_index
     /// with the `replacement_text`.
     /// @param start_index - starting position of the interval to be replaced.
@@ -116,59 +167,9 @@ void ReplaceInterval(size_t start_index,
                          std::string replacement_text,
                          std::string& wgsl_code);
 
-/// A function that, given WGSL-like string and a delimiter,
+    RandomGenerator& generator_;
-/// generates another WGSL-like string by picking two random regions
+};
-/// enclosed by the delimiter and swapping them.
-/// @param delimiter - the delimiter that will be used to find enclosed regions.
-/// @param wgsl_code - the initial string (WGSL code) that will be mutated.
-/// @param generator - the random number generator.
-/// @return true if a swap happened or false otherwise.
-bool SwapRandomIntervals(const std::string& delimiter,
-                         std::string& wgsl_code,
-                         RandomGenerator& generator);
 
-/// A function that, given a WGSL-like string and a delimiter,
-/// generates another WGSL-like string by deleting a random
-/// region enclosed by the delimiter.
-/// @param delimiter - the delimiter that will be used to find enclosed regions.
-/// @param wgsl_code - the initial string (WGSL code) that will be mutated.
-/// @param generator - the random number generator.
-/// @return true if a deletion happened or false otherwise.
-bool DeleteRandomInterval(const std::string& delimiter,
-                          std::string& wgsl_code,
-                          RandomGenerator& generator);
-
-/// A function that, given a WGSL-like string and a delimiter,
-/// generates another WGSL-like string by duplicating a random
-/// region enclosed by the delimiter.
-/// @param delimiter - the delimiter that will be used to find enclosed regions.
-/// @param wgsl_code - the initial string (WGSL code) that will be mutated.
-/// @param generator - the random number generator.
-/// @return true if a duplication happened or false otherwise.
-bool DuplicateRandomInterval(const std::string& delimiter,
-                             std::string& wgsl_code,
-                             RandomGenerator& generator);
-
-/// Replaces a randomly-chosen identifier in wgsl_code.
-/// @param wgsl_code - WGSL-like string where the replacement will occur.
-/// @param generator - the random number generator.
-/// @return true if a replacement happened or false otherwise.
-bool ReplaceRandomIdentifier(std::string& wgsl_code, RandomGenerator& generator);
-
-/// Replaces the value of a randomly-chosen integer with one of
-/// the values in the set {INT_MAX, INT_MIN, 0, -1}.
-/// @param wgsl_code - WGSL-like string where the replacement will occur.
-/// @param generator - the random number generator.
-/// @return true if a replacement happened or false otherwise.
-bool ReplaceRandomIntLiteral(std::string& wgsl_code, RandomGenerator& generator);
-
-/// Inserts a return statement in a randomly chosen function of a
-/// WGSL-like string. The return value is a randomly-chosen identifier
-/// or literal in the string.
-/// @param wgsl_code - WGSL-like string that will be mutated.
-/// @param generator - the random number generator.
-/// @return true if the mutation was succesful or false otherwise.
-bool InsertReturnStatement(std::string& wgsl_code, RandomGenerator& generator);
 }  // namespace tint::fuzzers::regex_fuzzer
 
 #endif  // SRC_TINT_FUZZERS_TINT_REGEX_FUZZER_WGSL_MUTATOR_H_