Add CRYPTO_BUFFER and CRYPTO_BUFFER_POOL.

These structures allow for blobs of data (e.g. certificates) to be
deduplicated in memory.

Change-Id: Iebfec90b85d55565848a178b6951562b4ccc083e
Reviewed-on: https://boringssl-review.googlesource.com/11820
Reviewed-by: Adam Langley <alangley@gmail.com>
Commit-Queue: Adam Langley <alangley@gmail.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

include/openssl/pool.h

diff --git a/include/openssl/pool.h b/include/openssl/pool.h
new file mode 100644
index 0000000..0f6a3c8
--- /dev/null
+++ b/include/openssl/pool.h
@@ -0,0 +1,87 @@
+/* Copyright (c) 2016, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
+
+#ifndef OPENSSL_HEADER_POOL_H
+#define OPENSSL_HEADER_POOL_H
+
+#include <openssl/base.h>
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+
+/* Buffers and buffer pools.
+ *
+ * |CRYPTO_BUFFER|s are simply reference-counted blobs. A |CRYPTO_BUFFER_POOL| is
+ * an intern table for |CRYPTO_BUFFER|s. This allows for a single copy of a given
+ * blob to be kept in memory and referenced from multiple places. */
+
+
+/* CRYPTO_BUFFER_POOL_new returns a freshly allocated |CRYPTO_BUFFER_POOL| or
+ * NULL on error. */
+OPENSSL_EXPORT CRYPTO_BUFFER_POOL* CRYPTO_BUFFER_POOL_new(void);
+
+/* CRYPTO_BUFFER_POOL_free frees |pool|, which must be empty. */
+OPENSSL_EXPORT void CRYPTO_BUFFER_POOL_free(CRYPTO_BUFFER_POOL *pool);
+
+/* CRYPTO_BUFFER_new returns a |CRYPTO_BUFFER| containing a copy of |data|, or
+ * else NULL on error. If |pool| is not NULL then the returned value may be a
+ * reference to a previously existing |CRYPTO_BUFFER| that contained the same
+ * data. Otherwise, the returned, fresh |CRYPTO_BUFFER| will be added to the
+ * pool. */
+OPENSSL_EXPORT CRYPTO_BUFFER *CRYPTO_BUFFER_new(const uint8_t *data, size_t len,
+                                                CRYPTO_BUFFER_POOL *pool);
+
+/* CRYPTO_BUFFER_new_from_CBS acts the same as |CRYPTO_BUFFER_new|. */
+OPENSSL_EXPORT CRYPTO_BUFFER *CRYPTO_BUFFER_new_from_CBS(
+    CBS *cbs, CRYPTO_BUFFER_POOL *pool);
+
+/* CRYPTO_BUFFER_free decrements the reference count of |buf|. If there are no
+ * other references, or if the only remaining reference is from a pool, then
+ * |buf| will be freed. */
+OPENSSL_EXPORT void CRYPTO_BUFFER_free(CRYPTO_BUFFER *buf);
+
+/* CRYPTO_BUFFER_up_ref increments the reference count of |buf| and returns
+ * one. */
+OPENSSL_EXPORT int CRYPTO_BUFFER_up_ref(CRYPTO_BUFFER *buf);
+
+/* CRYPTO_BUFFER_data returns a pointer to the data contained in |buf|. */
+OPENSSL_EXPORT const uint8_t *CRYPTO_BUFFER_data(const CRYPTO_BUFFER *buf);
+
+/* CRYPTO_BUFFER_len returns the length, in bytes, of the data contained in
+ * |buf|. */
+OPENSSL_EXPORT const size_t CRYPTO_BUFFER_len(const CRYPTO_BUFFER *buf);
+
+/* CRYPTO_BUFFER_init_CBS initialises |out| to point at the data from |buf|. */
+OPENSSL_EXPORT void CRYPTO_BUFFER_init_CBS(const CRYPTO_BUFFER *buf, CBS *out);
+
+
+#if defined(__cplusplus)
+}  /* extern C */
+
+extern "C++" {
+
+namespace bssl {
+
+BORINGSSL_MAKE_DELETER(CRYPTO_BUFFER_POOL, CRYPTO_BUFFER_POOL_free)
+BORINGSSL_MAKE_DELETER(CRYPTO_BUFFER, CRYPTO_BUFFER_free)
+
+}  // namespace bssl
+
+}  /* extern C++ */
+
+#endif
+
+#endif  // OPENSSL_HEADER_POOL_H