SL-19110 Fast hashing classes for use in place of the slow LLMD5, where speed matters. (#64)

This commit adds the HBXX64 and HBXX128 classes for use as a drop-in
replacement for the slow LLMD5 hashing class, where speed matters and
backward compatibility (with standard hashing algorithms) and/or
cryptographic hashing qualities are not required.
It also replaces LLMD5 with HBXX* in a few existing hot (well, ok, just
"warm" for some) paths meeting the above requirements, while paving the way for
future use cases, such as in the DRTVWR-559 and sibling branches where the slow
LLMD5 is used (e.g. to hash materials and vertex buffer cache entries), and
could be use such a (way) faster algorithm with very significant benefits and
no negative impact.

Here is the comment I added in indra/llcommon/hbxx.h:

// HBXXH* classes are to be used where speed matters and cryptographic quality
// is not required (no "one-way" guarantee, though they are likely not worst in
// this respect than MD5 which got busted and is now considered too weak). The
// xxHash code they are built upon is vectorized and about 50 times faster than
// MD5. A 64 bits hash class is also provided for when 128 bits of entropy are
// not needed. The hashes collision rate is similar to MD5's.
// See https://github.com/Cyan4973/xxHash#readme for details.

4 files changed, 646 insertions, 20 deletions

diff --git a/indra/llcommon/CMakeLists.txt b/indra/llcommon/CMakeLists.txt
index 991c3f70a1..fab7550c9a 100644
--- a/indra/llcommon/CMakeLists.txt
+++ b/indra/llcommon/CMakeLists.txt
@@ -119,6 +119,7 @@ set(llcommon_SOURCE_FILES
     lluriparser.cpp
     lluuid.cpp
     llworkerthread.cpp
+    hbxxh.cpp
     u64.cpp
     threadpool.cpp
     workqueue.cpp
@@ -257,6 +258,7 @@ set(llcommon_HEADER_FILES
     llwin32headers.h
     llwin32headerslean.h
     llworkerthread.h
+    hbxxh.h
     lockstatic.h
     stdtypes.h
     stringize.h
diff --git a/indra/llcommon/hbxxh.cpp b/indra/llcommon/hbxxh.cpp
new file mode 100644
index 0000000000..e94581d415
--- /dev/null
+++ b/indra/llcommon/hbxxh.cpp
@@ -0,0 +1,377 @@
+/**
+ * @file hbxxh.cpp
+ * @brief High performances vectorized hashing based on xxHash.
+ *
+ * $LicenseInfo:firstyear=2023&license=viewergpl$
+ * Second Life Viewer Source Code
+ * Copyright (c) 2023, Henri Beauchamp.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation;
+ * version 2.1 of the License only.
+ * 
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ * 
+ * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
+ * $/LicenseInfo$
+ */
+
+#include "linden_common.h"
+
+// This define ensures that xxHash will be compiled within this module, with
+// vectorized (*) and inlined functions (with no exported API symbol); our
+// xxhash "pre-built library" package actually only contains the xxhash.h
+// header (no library needed at link time).
+// (*) SSE2 is normally used for x86(_64) builds, unless you enabled AVX2
+// in your build, in which case the latter would be used instead. For ARM64
+// builds, this would also automatically enable NEON vectorization.
+#define XXH_INLINE_ALL
+#include "xxhash.h"
+
+#include "hbxxh.h"
+
+// How many bytes to grab at a time when hashing files or streams
+constexpr size_t BLOCK_LEN = 4096;
+
+///////////////////////////////////////////////////////////////////////////////
+// HBXXH64 class
+///////////////////////////////////////////////////////////////////////////////
+
+//static
+U64 HBXXH64::digest(const void* buffer, size_t len)
+{
+    return XXH3_64bits(buffer, len);
+}
+
+//static
+U64 HBXXH64::digest(const char* str)
+{
+    return XXH3_64bits((const void*)str, strlen(str));
+}
+
+//static
+U64 HBXXH64::digest(const std::string& str)
+{
+    return XXH3_64bits((const void*)str.c_str(), str.size());
+}
+
+// Must be called by all constructors.
+void HBXXH64::init()
+{
+    mDigest = 0;
+    mState = (void*)XXH3_createState();
+    if (!mState || XXH3_64bits_reset((XXH3_state_t*)mState) != XXH_OK)
+    {
+        LL_WARNS() << "Failed to initialize state !" << LL_ENDL;
+    }
+}
+
+HBXXH64::~HBXXH64()
+{
+    if (mState)
+    {
+        XXH3_freeState((XXH3_state_t*)mState);
+    }
+}
+
+void HBXXH64::update(const void* buffer, size_t len)
+{
+    if (mState)
+    {
+        XXH3_64bits_update((XXH3_state_t*)mState, buffer, len);
+    }
+    else
+    {
+        LL_WARNS() << "Cannot update a finalized digest !" << LL_ENDL;
+    }
+}
+
+void HBXXH64::update(const std::string& str)
+{
+    if (mState)
+    {
+        XXH3_64bits_update((XXH3_state_t*)mState, (const void*)str.c_str(),
+                           str.length());
+    }
+    else
+    {
+        LL_WARNS() << "Cannot update a finalized digest !" << LL_ENDL;
+    }
+}
+
+void HBXXH64::update(std::istream& stream)
+{
+    if (!mState)
+    {
+        LL_WARNS() << "Cannot update a finalized digest !" << LL_ENDL;
+        return;
+    }
+
+    char buffer[BLOCK_LEN];
+    size_t len;
+    while (stream.good())
+    {
+        stream.read(buffer, BLOCK_LEN);
+        len = stream.gcount();
+        XXH3_64bits_update((XXH3_state_t*)mState, (const void*)buffer, len);
+    }
+}
+
+void HBXXH64::update(FILE* file)
+{
+    if (!mState)
+    {
+        LL_WARNS() << "Cannot update a finalized digest !" << LL_ENDL;
+        return;
+    }
+
+    char buffer[BLOCK_LEN];
+    size_t len;
+    while ((len = fread((void*)buffer, 1, BLOCK_LEN, file)))
+    {
+        XXH3_64bits_update((XXH3_state_t*)mState, (const void*)buffer, len);
+    }
+    fclose(file);
+}
+
+void HBXXH64::finalize()
+{
+    if (!mState)
+    {
+        LL_WARNS() << "Already finalized !" << LL_ENDL;
+        return;
+    }
+    mDigest = XXH3_64bits_digest((XXH3_state_t*)mState);
+    XXH3_freeState((XXH3_state_t*)mState);
+    mState = NULL;
+}
+
+U64 HBXXH64::digest() const
+{
+    return mState ? XXH3_64bits_digest((XXH3_state_t*)mState) : mDigest;
+}
+
+std::ostream& operator<<(std::ostream& stream, HBXXH64 context)
+{
+    stream << context.digest();
+    return stream;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// HBXXH128 class
+///////////////////////////////////////////////////////////////////////////////
+
+//static
+LLUUID HBXXH128::digest(const void* buffer, size_t len)
+{
+    XXH128_hash_t hash = XXH3_128bits(buffer, len);
+    LLUUID id;
+    U64* data = (U64*)id.mData;
+    // Note: we do not check endianness here and we just store in the same
+    // order as XXH128_hash_t, that is low word "first".
+    data[0] = hash.low64;
+    data[1] = hash.high64;
+    return id;
+}
+
+//static
+LLUUID HBXXH128::digest(const char* str)
+{
+    XXH128_hash_t hash = XXH3_128bits((const void*)str, strlen(str));
+    LLUUID id;
+    U64* data = (U64*)id.mData;
+    // Note: we do not check endianness here and we just store in the same
+    // order as XXH128_hash_t, that is low word "first".
+    data[0] = hash.low64;
+    data[1] = hash.high64;
+    return id;
+}
+
+//static
+LLUUID HBXXH128::digest(const std::string& str)
+{
+    XXH128_hash_t hash = XXH3_128bits((const void*)str.c_str(), str.size());
+    LLUUID id;
+    U64* data = (U64*)id.mData;
+    // Note: we do not check endianness here and we just store in the same
+    // order as XXH128_hash_t, that is low word "first".
+    data[0] = hash.low64;
+    data[1] = hash.high64;
+    return id;
+}
+
+//static
+void HBXXH128::digest(LLUUID& result, const void* buffer, size_t len)
+{
+    XXH128_hash_t hash = XXH3_128bits(buffer, len);
+    U64* data = (U64*)result.mData;
+    // Note: we do not check endianness here and we just store in the same
+    // order as XXH128_hash_t, that is low word "first".
+    data[0] = hash.low64;
+    data[1] = hash.high64;
+}
+
+//static
+void HBXXH128::digest(LLUUID& result, const char* str)
+{
+    XXH128_hash_t hash = XXH3_128bits((const void*)str, strlen(str));
+    U64* data = (U64*)result.mData;
+    // Note: we do not check endianness here and we just store in the same
+    // order as XXH128_hash_t, that is low word "first".
+    data[0] = hash.low64;
+    data[1] = hash.high64;
+}
+
+//static
+void HBXXH128::digest(LLUUID& result, const std::string& str)
+{
+    XXH128_hash_t hash = XXH3_128bits((const void*)str.c_str(), str.size());
+    U64* data = (U64*)result.mData;
+    // Note: we do not check endianness here and we just store in the same
+    // order as XXH128_hash_t, that is low word "first".
+    data[0] = hash.low64;
+    data[1] = hash.high64;
+}
+
+// Must be called by all constructors.
+void HBXXH128::init()
+{
+    mState = (void*)XXH3_createState();
+    if (!mState || XXH3_128bits_reset((XXH3_state_t*)mState) != XXH_OK)
+    {
+        LL_WARNS() << "Failed to initialize state !" << LL_ENDL;
+    }
+}
+
+HBXXH128::~HBXXH128()
+{
+    if (mState)
+    {
+        XXH3_freeState((XXH3_state_t*)mState);
+    }
+}
+
+void HBXXH128::update(const void* buffer, size_t len)
+{
+    if (mState)
+    {
+        XXH3_128bits_update((XXH3_state_t*)mState, buffer, len);
+    }
+    else
+    {
+        LL_WARNS() << "Cannot update a finalized digest !" << LL_ENDL;
+    }
+}
+
+void HBXXH128::update(const std::string& str)
+{
+    if (mState)
+    {
+        XXH3_128bits_update((XXH3_state_t*)mState, (const void*)str.c_str(),
+                           str.length());
+    }
+    else
+    {
+        LL_WARNS() << "Cannot update a finalized digest !" << LL_ENDL;
+    }
+}
+
+void HBXXH128::update(std::istream& stream)
+{
+    if (!mState)
+    {
+        LL_WARNS() << "Cannot update a finalized digest !" << LL_ENDL;
+        return;
+    }
+
+    char buffer[BLOCK_LEN];
+    size_t len;
+    while (stream.good())
+    {
+        stream.read(buffer, BLOCK_LEN);
+        len = stream.gcount();
+        XXH3_128bits_update((XXH3_state_t*)mState, (const void*)buffer, len);
+    }
+}
+
+void HBXXH128::update(FILE* file)
+{
+    if (!mState)
+    {
+        LL_WARNS() << "Cannot update a finalized digest !" << LL_ENDL;
+        return;
+    }
+
+    char buffer[BLOCK_LEN];
+    size_t len;
+    while ((len = fread((void*)buffer, 1, BLOCK_LEN, file)))
+    {
+        XXH3_128bits_update((XXH3_state_t*)mState, (const void*)buffer, len);
+    }
+    fclose(file);
+}
+
+void HBXXH128::finalize()
+{
+    if (!mState)
+    {
+        LL_WARNS() << "Already finalized !" << LL_ENDL;
+        return;
+    }
+    XXH128_hash_t hash = XXH3_128bits_digest((XXH3_state_t*)mState);
+    U64* data = (U64*)mDigest.mData;
+    // Note: we do not check endianness here and we just store in the same
+    // order as XXH128_hash_t, that is low word "first".
+    data[0] = hash.low64;
+    data[1] = hash.high64;
+    XXH3_freeState((XXH3_state_t*)mState);
+    mState = NULL;
+}
+
+const LLUUID& HBXXH128::digest() const
+{
+    if (mState)
+    {
+        XXH128_hash_t hash = XXH3_128bits_digest((XXH3_state_t*)mState);
+        // We cheat the const-ness of the method here, but this is OK, since
+        // mDigest is private and cannot be accessed indirectly by other
+        // methods than digest() ones, that do check for mState to decide
+        // wether mDigest's current value may be provided as is or not. This
+        // cheat saves us a temporary LLLUID copy.
+        U64* data = (U64*)mDigest.mData;
+        // Note: we do not check endianness here and we just store in the same
+        // order as XXH128_hash_t, that is low word "first".
+        data[0] = hash.low64;
+        data[1] = hash.high64;
+    }
+    return mDigest;
+}
+
+void HBXXH128::digest(LLUUID& result) const
+{
+    if (!mState)
+    {
+        result = mDigest;
+        return;
+    }
+    XXH128_hash_t hash = XXH3_128bits_digest((XXH3_state_t*)mState);
+    U64* data = (U64*)result.mData;
+    // Note: we do not check endianness here and we just store in the same
+    // order as XXH128_hash_t, that is low word "first".
+    data[0] = hash.low64;
+    data[1] = hash.high64;
+}
+
+std::ostream& operator<<(std::ostream& stream, HBXXH128 context)
+{
+    stream << context.digest();
+    return stream;
+}
diff --git a/indra/llcommon/hbxxh.h b/indra/llcommon/hbxxh.h
new file mode 100644
index 0000000000..8a5f977648
--- /dev/null
+++ b/indra/llcommon/hbxxh.h
@@ -0,0 +1,259 @@
+/**
+ * @file hbxxh.h
+ * @brief High performances vectorized hashing based on xxHash.
+ *
+ * $LicenseInfo:firstyear=2023&license=viewergpl$
+ * Second Life Viewer Source Code
+ * Copyright (c) 2023, Henri Beauchamp.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation;
+ * version 2.1 of the License only.
+ * 
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ * 
+ * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
+ * $/LicenseInfo$
+ */
+
+#ifndef LL_HBXXH_H
+#define LL_HBXXH_H
+
+#include "lluuid.h"
+
+// HBXXH* classes are to be used where speed matters and cryptographic quality
+// is not required (no "one-way" guarantee, though they are likely not worst in
+// this respect than MD5 which got busted and is now considered too weak). The
+// xxHash code they are built upon is vectorized and about 50 times faster than
+// MD5. A 64 bits hash class is also provided for when 128 bits of entropy are
+// not needed. The hashes collision rate is similar to MD5's.
+// See https://github.com/Cyan4973/xxHash#readme for details.
+
+// 64 bits hashing class
+
+class HBXXH64
+{
+    friend std::ostream& operator<<(std::ostream&, HBXXH64);
+
+protected:
+    LOG_CLASS(HBXXH64);
+
+public:
+    inline HBXXH64()                            { init(); }
+
+    // Constructors for special circumstances; they all digest the first passed
+    // parameter. Set 'do_finalize' to false if you do not want to finalize the
+    // context, which is useful/needed when you want to update() it afterwards.
+    // Ideally, the compiler should be smart enough to get our clue and
+    // optimize out the const bool test during inlining...
+
+    inline HBXXH64(const void* buffer, size_t len,
+                   const bool do_finalize = true)
+    {
+        init();
+        update(buffer, len);
+        if (do_finalize)
+        {
+            finalize();
+        }
+    }
+
+    inline HBXXH64(const std::string& str, const bool do_finalize = true)
+    {
+        init();
+        update(str);
+        if (do_finalize)
+        {
+            finalize();
+        }
+    }
+
+    inline HBXXH64(std::istream& s, const bool do_finalize = true)
+    {
+        init();
+        update(s);
+        if (do_finalize)
+        {
+            finalize();
+        }
+    }
+
+    inline HBXXH64(FILE* file, const bool do_finalize = true)
+    {
+        init();
+        update(file);
+        if (do_finalize)
+        {
+            finalize();
+        }
+    }
+
+    ~HBXXH64();
+
+    void update(const void* buffer, size_t len);
+    void update(const std::string& str);
+    void update(std::istream& s);
+    void update(FILE* file);
+
+    // Note that unlike what happens with LLMD5, you do not need to finalize()
+    // HBXXH64 before using digest(), and you may keep updating() it even after
+    // you got a first digest() (the next digest would of course change after
+    // any update). It is still useful to use finalize() when you do not want
+    // to store a final digest() result in a separate U64; after this method
+    // has been called, digest() simply returns mDigest value.
+    void finalize();
+
+    U64 digest() const;
+
+    // Fast static methods. Use them when hashing just one contiguous block of
+    // data.
+    static U64 digest(const void* buffer, size_t len);
+    static U64 digest(const char* str);    // str must be NUL-terminated
+    static U64 digest(const std::string& str);
+
+private:
+    void init();
+
+private:
+    // We use a void pointer to avoid including xxhash.h here for XXH3_state_t
+    // (which cannot either be trivially forward-declared, due to complex API
+    // related pre-processor macros in xxhash.h).
+    void*   mState;
+    U64     mDigest;
+};
+
+inline bool operator==(const HBXXH64& a, const HBXXH64& b)
+{
+    return a.digest() == b.digest();
+}
+
+inline bool operator!=(const HBXXH64& a, const HBXXH64& b)
+{
+    return a.digest() != b.digest();
+}
+
+// 128 bits hashing class
+
+class HBXXH128
+{
+    friend std::ostream& operator<<(std::ostream&, HBXXH128);
+
+protected:
+    LOG_CLASS(HBXXH128);
+
+public:
+    inline HBXXH128()                           { init(); }
+
+    // Constructors for special circumstances; they all digest the first passed
+    // parameter. Set 'do_finalize' to false if you do not want to finalize the
+    // context, which is useful/needed when you want to update() it afterwards.
+    // Ideally, the compiler should be smart enough to get our clue and
+    // optimize out the const bool test during inlining...
+
+    inline HBXXH128(const void* buffer, size_t len,
+                    const bool do_finalize = true)
+    {
+        init();
+        update(buffer, len);
+        if (do_finalize)
+        {
+            finalize();
+        }
+    }
+
+    inline HBXXH128(const std::string& str, const bool do_finalize = true)
+    {
+        init();
+        update(str);
+        if (do_finalize)
+        {
+            finalize();
+        }
+    }
+
+    inline HBXXH128(std::istream& s, const bool do_finalize = true)
+    {
+        init();
+        update(s);
+        if (do_finalize)
+        {
+            finalize();
+        }
+    }
+
+    inline HBXXH128(FILE* file, const bool do_finalize = true)
+    {
+        init();
+        update(file);
+        if (do_finalize)
+        {
+            finalize();
+        }
+    }
+
+    ~HBXXH128();
+
+    void update(const void* buffer, size_t len);
+    void update(const std::string& str);
+    void update(std::istream& s);
+    void update(FILE* file);
+
+    // Note that unlike what happens with LLMD5, you do not need to finalize()
+    // HBXXH128 before using digest(), and you may keep updating() it even
+    // after you got a first digest() (the next digest would of course change
+    // after any update). It is still useful to use finalize() when you do not
+    // want to store a final digest() result in a separate LLUUID; after this
+    // method has been called, digest() simply returns a reference on mDigest.
+    void finalize();
+
+    // We use an LLUUID for the digest, since this is a 128 bits wide native
+    // type available in the viewer code, making it easy to manipulate. It also
+    // allows to use HBXXH128 efficiently in LLUUID generate() and combine()
+    // methods.
+    const LLUUID& digest() const;
+
+    // Here, we avoid an LLUUID copy whenever we already got one to store the
+    // result *and* we did not yet call finalize().
+    void digest(LLUUID& result) const;
+
+    // Fast static methods. Use them when hashing just one contiguous block of
+    // data.
+    static LLUUID digest(const void* buffer, size_t len);
+    static LLUUID digest(const char* str);    // str must be NUL-terminated
+    static LLUUID digest(const std::string& str);
+    // Same as above, but saves you from an LLUUID copy when you already got
+    // one for storage use.
+    static void digest(LLUUID& result, const void* buffer, size_t len);
+    static void digest(LLUUID& result, const char* str); // str NUL-terminated
+    static void digest(LLUUID& result, const std::string& str);
+
+private:
+    void init();
+
+private:
+    // We use a void pointer to avoid including xxhash.h here for XXH3_state_t
+    // (which cannot either be trivially forward-declared, due to complex API
+    // related pre-processor macros in xxhash.h).
+    void*   mState;
+    LLUUID  mDigest;
+};
+
+inline bool operator==(const HBXXH128& a, const HBXXH128& b)
+{
+    return a.digest() == b.digest();
+}
+
+inline bool operator!=(const HBXXH128& a, const HBXXH128& b)
+{
+    return a.digest() != b.digest();
+}
+
+#endif // LL_HBXXH_H
diff --git a/indra/llcommon/lluuid.cpp b/indra/llcommon/lluuid.cpp
index acce8366ea..8ff6c45760 100644
--- a/indra/llcommon/lluuid.cpp
+++ b/indra/llcommon/lluuid.cpp
@@ -40,11 +40,11 @@
 #include "lluuid.h"
 #include "llerror.h"
 #include "llrand.h"
-#include "llmd5.h"
 #include "llstring.h"
 #include "lltimer.h"
 #include "llthread.h"
 #include "llmutex.h"
+#include "hbxxh.h"
 
 const LLUUID LLUUID::null;
 const LLTransactionID LLTransactionID::tnull;
@@ -402,11 +402,9 @@ LLUUID LLUUID::operator^(const LLUUID& rhs) const
 
 void LLUUID::combine(const LLUUID& other, LLUUID& result) const
 {
-	LLMD5 md5_uuid;
-	md5_uuid.update((unsigned char*)mData, 16);
-	md5_uuid.update((unsigned char*)other.mData, 16);
-	md5_uuid.finalize();
-	md5_uuid.raw_digest(result.mData);
+	HBXXH128 hash((const void*)mData, 16, false);	// false = do not finalize
+	hash.update((const void*)other.mData, 16);
+	hash.digest(result);
 }
 
 LLUUID LLUUID::combine(const LLUUID &other) const
@@ -857,17 +855,12 @@ void LLUUID::generate()
 	tmp >>= 8;
 	mData[8] = (unsigned char) tmp;
 
-	LLMD5 md5_uuid;
-	
-	md5_uuid.update(mData,16);
-	md5_uuid.finalize();
-	md5_uuid.raw_digest(mData);
+	HBXXH128::digest(*this, (const void*)mData, 16);
 }
 
 void LLUUID::generate(const std::string& hash_string)
 {
-	LLMD5 md5_uuid((U8*)hash_string.c_str());
-	md5_uuid.raw_digest(mData);
+	HBXXH128::digest(*this, hash_string);
 }
 
 U32 LLUUID::getRandomSeed()
@@ -885,13 +878,8 @@ U32 LLUUID::getRandomSeed()
    seed[7]=(unsigned char)(pid);
    getSystemTime((uuid_time_t *)(&seed[8]));
 
-   LLMD5 md5_seed;
-	
-   md5_seed.update(seed,16);
-   md5_seed.finalize();
-   md5_seed.raw_digest(seed);
-   
-   return(*(U32 *)seed);
+   U64 seed64 = HBXXH64((const void*)seed, 16).digest();
+   return U32(seed64) ^ U32(seed64 >> 32);
 }
 
 BOOL LLUUID::parseUUID(const std::string& buf, LLUUID* value)