Add validation caching interface.

src/trusted/validator/validation_cache.h

+/*
+ * Copyright (c) 2012 The Native Client Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef NATIVE_CLIENT_SRC_TRUSTED_VALIDATOR_VALIDATION_CACHE_H_
+#define NATIVE_CLIENT_SRC_TRUSTED_VALIDATOR_VALIDATION_CACHE_H_
+
+#include "native_client/src/include/nacl_base.h"
+
+EXTERN_C_BEGIN
+
+/*
+ * This interface allows the validator to query a database of validation results
+ * while hiding details of how the database is implemented.
+ *
+ * query = cache->CreateQuery(cache->handle);
+ * CreateQuery: create an opaque query object, given an opaque context object.
+ * The context object contains persistent variables that will be used for all
+ * queries, whereas the query object contains information relevant to a single
+ * validation result.
+ *
+ * cache->AddData(query, data, data_size);
+ * AddData: add a blob of binary data to the query.  Conceptually, the query
+ * will concatenate all the binary data it is given, in the order it is given,
+ * and use the concatenated blob as a key to look up validation results in a
+ * database.  In practice, all of the data is hashed into a reasonabally sized
+ * key.  The validation cache doesn't care what data it is given, it is the
+ * responsibility of the validator to provide enough information to uniquely
+ * identify the validation result.  This gives flexibility to use different
+ * types of keys for different validators and different sources of code.
+ *
+ * validation_passed = cache->QueryCodeValidates(query);
+ * QueryCodeValidates: the key is complete, query the validation status.
+ * AddData must not be called after calling this function.
+ *
+ * cache->SetCodeValidates(query);
+ * SetCodeValidates: set the database entry for the given key.
+ * QueryCodeValidates must be called first.
+ *
+ * cache->DestroyQuery(query);
+ * DestroyQuery: cleanup and deallocate the query object.
+ */
+
+typedef struct NaClValidationCache {

[Mark Seaborn, 2012/03/01 19:23:12]

Suggestion: I'd be inclined to refer to it as 'struct NaClValidationCache' and
not use the typedef, for consistency with service_runtime and NaClDesc.

[Nick Bray (chromium), 2012/03/01 21:16:58]

Done.

+  void *handle;
+  void *(*CreateQuery)(void *handle);
+  void (*AddData)(void *query, const unsigned char *data, size_t length);
+  int (*QueryCodeValidates)(void *query);
+  void (*SetCodeValidates)(void *query);
+  void (*DestroyQuery)(void *query);
+} NaClValidationCache;
+
+EXTERN_C_END
+
+#endif /* NATIVE_CLIENT_SRC_TRUSTED_VALIDATOR_VALIDATION_CACHE_H_ */