[PATCH] D74359: [compiler-rt] FuzzedDataProvider: add ConsumeMemory and hash methods.

[Max Moroz via Phabricator via llvm-commits]

Dor1s created this revision.
Dor1s added a reviewer: metzman.
Herald added subscribers: llvm-commits, Sanitizers, dberris.
Herald added projects: Sanitizers, LLVM.

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D74359

Files:
  compiler-rt/include/fuzzer/FuzzedDataProvider.h


Index: compiler-rt/include/fuzzer/FuzzedDataProvider.h
===================================================================
--- compiler-rt/include/fuzzer/FuzzedDataProvider.h
+++ compiler-rt/include/fuzzer/FuzzedDataProvider.h
@@ -237,6 +237,27 @@
     return result + range * ConsumeProbability<T>();
   }
 
+  // Writes |num_bytes| of input data to the given destination pointer. If there
+  // is not enough data left, writes all remaining bytes. Return value is the
+  // number of bytes written.
+  // In general, it's better to avoid using this function, but it may be useful
+  // in cases when it's necessary to fill a certain buffer or object with
+  // fuzzing data.
+  size_t ConsumeMemory(void *destination, size_t num_bytes) {
+    num_bytes = std::min(num_bytes, remaining_bytes_);
+    CopyAndAdvance(destination, num_bytes);
+    return num_bytes;
+  }
+
+  // Returns the hash of the remaining data. Not recommended in general, but is
+  // useful when you need a pseudo-random value that changes significantly with
+  // any change in the fuzzing data.
+  size_t hash() {
+    // TODO(Dor1s): change to `string_view` once C++17 becomes mainstream.
+    std::string str(data_ptr_, remaining_bytes_);
+    return std::hash(decltype(str));
+  }
+
   // Reports the remaining bytes available for fuzzed input.
   size_t remaining_bytes() { return remaining_bytes_; }
 
@@ -244,6 +265,11 @@
   FuzzedDataProvider(const FuzzedDataProvider &) = delete;
   FuzzedDataProvider &operator=(const FuzzedDataProvider &) = delete;
 
+  void CopyAndAdvance(void *destination, size_t num_bytes) {
+    std::memcpy(destination, data_ptr_, num_bytes);
+    Advance(num_bytes);
+  }
+
   void Advance(size_t num_bytes) {
     if (num_bytes > remaining_bytes_)
       abort();
@@ -253,7 +279,7 @@
   }
 
   template <typename T>
-  std::vector<T> ConsumeBytes(size_t size, size_t num_bytes_to_consume) {
+  std::vector<T> ConsumeBytes(size_t size, size_t num_bytes) {
     static_assert(sizeof(T) == sizeof(uint8_t), "Incompatible data type.");
 
     // The point of using the size-based constructor below is to increase the
@@ -264,13 +290,12 @@
     // To increase the odds even more, we also call |shrink_to_fit| below.
     std::vector<T> result(size);
     if (size == 0) {
-      if (num_bytes_to_consume != 0)
+      if (num_bytes != 0)
         abort();
       return result;
     }
 
-    std::memcpy(result.data(), data_ptr_, num_bytes_to_consume);
-    Advance(num_bytes_to_consume);
+    CopyAndAdvance(result.data(), num_bytes);
 
     // Even though |shrink_to_fit| is also implementation specific, we expect it
     // to provide an additional assurance in case vector's constructor allocated


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