net: Add fuzzer for HostResolverImpl.

net/base/fuzzed_data_provider.h

Index: net/base/fuzzed_data_provider.h
diff --git a/net/base/fuzzed_data_provider.h b/net/base/fuzzed_data_provider.h
index 47a45061cdf248b9a2da0bd5e94fb1399f04ba6b..81fded425a233116c9fc6eb100d09e3364cc29fc 100644
--- a/net/base/fuzzed_data_provider.h
+++ b/net/base/fuzzed_data_provider.h
@@ -33,24 +33,33 @@ class FuzzedDataProvider {
   // FuzzedDataProvider is destroyed.
   base::StringPiece ConsumeRemainingBytes();
 
-  // Returns an unsigned number in the range [min, max] by consuming bytes from
-  // the input data. The value might not be uniformly distributed in the given
-  // range. If there's no input data left, always returns |min|. |min| must be
-  // less than or equal to |max|.
-  uint32_t ConsumeValueInRange(uint32_t min, uint32_t max);
+  // Returns a number in the range [min, max] by consuming bytes from the input
+  // data. The value might not be uniformly distributed in the given range. If
+  // there's no input data left, always returns |min|. |min| must be less than
+  // or equal to |max|.
+  uint32_t ConsumeUint32InRange(uint32_t min, uint32_t max);
+  int ConsumeInt32InRange(int min, int max);
 
   // Returns a bool, or false when no data remains.
   bool ConsumeBool();
 
   // Returns a uint8_t from the input or 0 if nothing remains. This is
-  // equivalent to ConsumeValueInRange(0, 0xFF).
+  // equivalent to ConsumeUint32InRange(0, 0xFF).
   uint8_t ConsumeUint8();
 
   // Returns a uint16_t from the input. If fewer than 2 bytes of data remain
   // will fill the most significant bytes with 0. This is equivalent to
-  // ConsumeValueInRange(0, 0xFFFF).
+  // ConsumeUint32InRange(0, 0xFFFF).
   uint16_t ConsumeUint16();
 
+  // Returns a value from |array|, consuming as many bytes as needed to do so.
+  // |array| must be a fixed-size array. Equivalent to
+  // array[ConsumeUint32InRange(sizeof(array)-1)];
+  template <typename Type, int size>

[eroman, 2016/06/01 01:47:21]

nit: size_t -- Although I can't imagine it making a difference in practice.

[mmenke, 2016/06/01 21:21:51]

Done.

+  Type PickArrayEntry(Type (&array)[size]) {

[mmenke, 2016/05/19 19:09:46]

Open to other names here.  "ConsumeArrayEntry" or "ConsumeValueFromArray" both
sound like the array is being modified.  Also, is this what you had in mind, or
were you thinking of the (simpler, more reedable) "PickArrayEntry(Type* array,
size_t size)"

[eroman, 2016/06/01 01:47:21]

Yep this is what I was thinking.

Current name is fine by me.

Another idea is PickValueFromArray()

[mmenke, 2016/06/01 21:21:51]

I like the name much better...  Actually, though, I like PickValueInArray even
better, so I went with that.  It matches the "ConsumeBlahInRange" methods a bit
more closely.

+    return array[ConsumeUint32InRange(0, size - 1)];
+  }
+
   // Reports the remaining bytes available for fuzzed input.
   size_t remaining_bytes() { return remaining_data_.length(); }