Represent invalid UUIDs as UUIDs with length zero

Summary:
During the previous attempt to generalize the UUID class, it was
suggested that we represent invalid UUIDs as length zero (previously, we
used an all-zero UUID for that). This meant that some valid build-ids
could not be represented (it's possible however unlikely that a checksum of
some file would be zero) and complicated adding support for variable
length build-ids (should a 16-byte empty UUID compare equal to a 20-byte
empty UUID?).

This patch resolves these issues by introducing a canonical
representation for an invalid UUID. The slight complication here is that
some clients (MachO) actually use the all-zero notation to mean "no UUID
has been set". To keep this use case working (while making it very
explicit about which construction semantices are wanted), replaced the
UUID constructors and the SetBytes functions with named factory methods.
- "fromData" creates a UUID from the given data, and it treats all bytes
  equally.
- "fromOptionalData" first checks the data contents - if all bytes are
  zero, it treats this as an invalid/empty UUID.

Reviewers: clayborg, sas, lemo, davide, espindola

Subscribers: emaste, lldb-commits, arichardson

Differential Revision: https://reviews.llvm.org/D48479

llvm-svn: 335612

12 files changed, 111 insertions, 144 deletions

diff --git a/lldb/include/lldb/Utility/DataExtractor.h b/lldb/include/lldb/Utility/DataExtractor.h
index b4886700e1a..50c88db8e35 100644
--- a/lldb/include/lldb/Utility/DataExtractor.h
+++ b/lldb/include/lldb/Utility/DataExtractor.h
@@ -223,22 +223,6 @@ public:
                           const char *type_format = nullptr) const;
 
   //------------------------------------------------------------------
-  /// Dump a UUID value at \a offset.
-  ///
-  /// Dump a UUID starting at \a offset bytes into this object's data. If the
-  /// stream \a s is nullptr, the output will be sent to Log().
-  ///
-  /// @param[in] s
-  ///     The stream to dump the output to. If nullptr the output will
-  ///     be dumped to Log().
-  ///
-  /// @param[in] offset
-  ///     The offset into the data at which to extract and dump a
-  ///     UUID value.
-  //------------------------------------------------------------------
-  void DumpUUID(Stream *s, lldb::offset_t offset) const;
-
-  //------------------------------------------------------------------
   /// Extract an arbitrary number of bytes in the specified byte order.
   ///
   /// Attemps to extract \a length bytes starting at \a offset bytes into this
diff --git a/lldb/include/lldb/Utility/UUID.h b/lldb/include/lldb/Utility/UUID.h
index 617b76617cb..a6ce7de2299 100644
--- a/lldb/include/lldb/Utility/UUID.h
+++ b/lldb/include/lldb/Utility/UUID.h
@@ -33,15 +33,38 @@ public:
   //------------------------------------------------------------------
   // Constructors and Destructors
   //------------------------------------------------------------------
-  UUID();
-  UUID(const UUID &rhs);
-  UUID(const void *uuid_bytes, uint32_t num_uuid_bytes);
+  UUID() = default;
+
+  /// Creates a UUID from the data pointed to by the bytes argument. No special
+  /// significance is attached to any of the values.
+  static UUID fromData(const void *bytes, uint32_t num_bytes) {
+    if (bytes)
+      return fromData({reinterpret_cast<const uint8_t *>(bytes), num_bytes});
+    return UUID();
+  }
 
-  ~UUID();
+  /// Creates a uuid from the data pointed to by the bytes argument. No special
+  /// significance is attached to any of the values.
+  static UUID fromData(llvm::ArrayRef<uint8_t> bytes) { return UUID(bytes); }
+
+  /// Creates a UUID from the data pointed to by the bytes argument. Data
+  /// consisting purely of zero bytes is treated as an invalid UUID.
+  static UUID fromOptionalData(const void *bytes, uint32_t num_bytes) {
+    if (bytes)
+      return fromOptionalData(
+          {reinterpret_cast<const uint8_t *>(bytes), num_bytes});
+    return UUID();
+  }
 
-  const UUID &operator=(const UUID &rhs);
+  /// Creates a UUID from the data pointed to by the bytes argument. Data
+  /// consisting purely of zero bytes is treated as an invalid UUID.
+  static UUID fromOptionalData(llvm::ArrayRef<uint8_t> bytes) {
+    if (llvm::all_of(bytes, [](uint8_t b) { return b == 0; }))
+      return UUID();
+    return UUID(bytes);
+  }
 
-  void Clear();
+  void Clear() { m_num_uuid_bytes = 0; }
 
   void Dump(Stream *s) const;
 
@@ -49,9 +72,8 @@ public:
     return {m_uuid, m_num_uuid_bytes};
   }
 
-  bool IsValid() const;
-
-  bool SetBytes(const void *uuid_bytes, uint32_t num_uuid_bytes = 16);
+  explicit operator bool() const { return IsValid(); }
+  bool IsValid() const { return m_num_uuid_bytes > 0; }
 
   std::string GetAsString(const char *separator = nullptr) const;
 
@@ -81,11 +103,10 @@ public:
                             uint32_t &bytes_decoded,
                             uint32_t num_uuid_bytes = 16);
 
-protected:
-  //------------------------------------------------------------------
-  // Classes that inherit from UUID can see and modify these
-  //------------------------------------------------------------------
-  uint32_t m_num_uuid_bytes; // Should be 16 or 20
+private:
+  UUID(llvm::ArrayRef<uint8_t> bytes);
+
+  uint32_t m_num_uuid_bytes = 0; // Should be 0, 16 or 20
   ValueType m_uuid;
 };
 
diff --git a/lldb/source/API/SBModuleSpec.cpp b/lldb/source/API/SBModuleSpec.cpp
index 0e6e7c9b0b9..afabd9ace2b 100644
--- a/lldb/source/API/SBModuleSpec.cpp
+++ b/lldb/source/API/SBModuleSpec.cpp
@@ -90,7 +90,8 @@ size_t SBModuleSpec::GetUUIDLength() {
 }
 
 bool SBModuleSpec::SetUUIDBytes(const uint8_t *uuid, size_t uuid_len) {
-  return m_opaque_ap->GetUUID().SetBytes(uuid, uuid_len);
+  m_opaque_ap->GetUUID() = UUID::fromOptionalData(uuid, uuid_len);
+  return m_opaque_ap->GetUUID().IsValid();
 }
 
 bool SBModuleSpec::GetDescription(lldb::SBStream &description) {
diff --git a/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp b/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
index c1e6809d1ff..8999000dff8 100644
--- a/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
+++ b/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
@@ -1368,7 +1368,7 @@ uint32_t DynamicLoaderDarwinKernel::ReadKextSummaries(
       if (name_data == NULL)
         break;
       image_infos[i].SetName((const char *)name_data);
-      UUID uuid(extractor.GetData(&offset, 16), 16);
+      UUID uuid = UUID::fromOptionalData(extractor.GetData(&offset, 16), 16);
       image_infos[i].SetUUID(uuid);
       image_infos[i].SetLoadAddress(extractor.GetU64(&offset));
       image_infos[i].SetSize(extractor.GetU64(&offset));
diff --git a/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderMacOSXDYLD.cpp b/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderMacOSXDYLD.cpp
index 864ad7dea70..265f19d0ca0 100644
--- a/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderMacOSXDYLD.cpp
+++ b/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderMacOSXDYLD.cpp
@@ -898,7 +898,7 @@ uint32_t DynamicLoaderMacOSXDYLD::ParseLoadCommands(const DataExtractor &data,
         break;
 
       case llvm::MachO::LC_UUID:
-        dylib_info.uuid.SetBytes(data.GetData(&offset, 16));
+        dylib_info.uuid = UUID::fromOptionalData(data.GetData(&offset, 16), 16);
         break;
 
       default:
@@ -1110,7 +1110,7 @@ bool DynamicLoaderMacOSXDYLD::GetSharedCacheInformation(
         uuid_t shared_cache_uuid;
         if (m_process->ReadMemory(sharedCacheUUID_address, shared_cache_uuid,
                                   sizeof(uuid_t), err) == sizeof(uuid_t)) {
-          uuid.SetBytes(shared_cache_uuid);
+          uuid = UUID::fromOptionalData(shared_cache_uuid, 16);
           if (uuid.IsValid()) {
             using_shared_cache = eLazyBoolYes;
           }
diff --git a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
index 1b70f8a933e..de7b391a3b4 100644
--- a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
+++ b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
@@ -733,13 +733,13 @@ size_t ObjectFileELF::GetModuleSpecifications(
             if (gnu_debuglink_crc) {
               // Use 4 bytes of crc from the .gnu_debuglink section.
               uint32_t uuidt[4] = {gnu_debuglink_crc, 0, 0, 0};
-              uuid.SetBytes(uuidt, sizeof(uuidt));
+              uuid = UUID::fromData(uuidt, sizeof(uuidt));
             } else if (core_notes_crc) {
               // Use 8 bytes - first 4 bytes for *magic* prefix, mainly to make
               // it look different form .gnu_debuglink crc followed by 4 bytes
               // of note segments crc.
               uint32_t uuidt[4] = {g_core_uuid_magic, core_notes_crc, 0, 0};
-              uuid.SetBytes(uuidt, sizeof(uuidt));
+              uuid = UUID::fromData(uuidt, sizeof(uuidt));
             }
           }
 
@@ -926,7 +926,7 @@ bool ObjectFileELF::GetUUID(lldb_private::UUID *uuid) {
       // different form .gnu_debuglink crc - followed by 4 bytes of note
       // segments crc.
       uint32_t uuidt[4] = {g_core_uuid_magic, core_notes_crc, 0, 0};
-      m_uuid.SetBytes(uuidt, sizeof(uuidt));
+      m_uuid = UUID::fromData(uuidt, sizeof(uuidt));
     }
   } else {
     if (!m_gnu_debuglink_crc)
@@ -935,7 +935,7 @@ bool ObjectFileELF::GetUUID(lldb_private::UUID *uuid) {
     if (m_gnu_debuglink_crc) {
       // Use 4 bytes of crc from the .gnu_debuglink section.
       uint32_t uuidt[4] = {m_gnu_debuglink_crc, 0, 0, 0};
-      m_uuid.SetBytes(uuidt, sizeof(uuidt));
+      m_uuid = UUID::fromData(uuidt, sizeof(uuidt));
     }
   }
 
@@ -1284,7 +1284,7 @@ ObjectFileELF::RefineModuleDetailsFromNote(lldb_private::DataExtractor &data,
             }
 
             // Save the build id as the UUID for the module.
-            uuid.SetBytes(uuidbuf, note.n_descsz);
+            uuid = UUID::fromData(uuidbuf, note.n_descsz);
           }
         }
         break;
diff --git a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
index b2cb6bd23f9..91e7f335327 100644
--- a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
+++ b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
@@ -2087,10 +2087,8 @@ UUID ObjectFileMachO::GetSharedCacheUUID(FileSpec dyld_shared_cache,
   version_str[6] = '\0';
   if (strcmp(version_str, "dyld_v") == 0) {
     offset = offsetof(struct lldb_copy_dyld_cache_header_v1, uuid);
-    uint8_t uuid_bytes[sizeof(uuid_t)];
-    memcpy(uuid_bytes, dsc_header_data.GetData(&offset, sizeof(uuid_t)),
-           sizeof(uuid_t));
-    dsc_uuid.SetBytes(uuid_bytes);
+    dsc_uuid = UUID::fromOptionalData(
+        dsc_header_data.GetData(&offset, sizeof(uuid_t)), sizeof(uuid_t));
   }
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_SYMBOLS));
   if (log && dsc_uuid.IsValid()) {
@@ -4861,7 +4859,7 @@ bool ObjectFileMachO::GetUUID(const llvm::MachO::mach_header &header,
         if (!memcmp(uuid_bytes, opencl_uuid, 16))
           return false;
 
-        uuid.SetBytes(uuid_bytes);
+        uuid = UUID::fromOptionalData(uuid_bytes, 16);
         return true;
       }
       return false;
@@ -5392,12 +5390,11 @@ bool ObjectFileMachO::GetCorefileMainBinaryInfo (addr_t &address, UUID &uuid) {
                   uuid_t raw_uuid;
                   memset (raw_uuid, 0, sizeof (uuid_t));
 
-                  if (m_data.GetU32 (&offset, &type, 1)
-                      && m_data.GetU64 (&offset, &address, 1)
-                      && m_data.CopyData (offset, sizeof (uuid_t), raw_uuid) != 0
-                      && uuid.SetBytes (raw_uuid, sizeof (uuid_t)))
-                  {
-                      return true;
+                  if (m_data.GetU32(&offset, &type, 1) &&
+                      m_data.GetU64(&offset, &address, 1) &&
+                      m_data.CopyData(offset, sizeof(uuid_t), raw_uuid) != 0) {
+                    uuid = UUID::fromOptionalData(raw_uuid, sizeof(uuid_t));
+                    return true;
                   }
               }
           }
@@ -5660,7 +5657,7 @@ void ObjectFileMachO::GetLLDBSharedCacheUUID(addr_t &base_addr, UUID &uuid) {
                           + 100); // sharedCacheBaseAddress <mach-o/dyld_images.h>
           }
         }
-        uuid.SetBytes(sharedCacheUUID_address);
+        uuid = UUID::fromOptionalData(sharedCacheUUID_address, sizeof(uuid_t));
       }
     }
   } else {
@@ -5685,7 +5682,7 @@ void ObjectFileMachO::GetLLDBSharedCacheUUID(addr_t &base_addr, UUID &uuid) {
         dyld_process_info_get_cache (process_info, &sc_info);
         if (sc_info.cacheBaseAddress != 0) {
           base_addr = sc_info.cacheBaseAddress;
-          uuid.SetBytes (sc_info.cacheUUID);
+          uuid = UUID::fromOptionalData(sc_info.cacheUUID, sizeof(uuid_t));
         }
         dyld_process_info_release (process_info);
       }
diff --git a/lldb/source/Plugins/Process/minidump/MinidumpParser.cpp b/lldb/source/Plugins/Process/minidump/MinidumpParser.cpp
index 58cafc737fc..6f43e6add7d 100644
--- a/lldb/source/Plugins/Process/minidump/MinidumpParser.cpp
+++ b/lldb/source/Plugins/Process/minidump/MinidumpParser.cpp
@@ -114,18 +114,9 @@ UUID MinidumpParser::GetModuleUUID(const MinidumpModule *module) {
     const CvRecordPdb70 *pdb70_uuid = nullptr;
     Status error = consumeObject(cv_record, pdb70_uuid);
     if (!error.Fail())
-      return UUID(pdb70_uuid, sizeof(*pdb70_uuid));
-  } else if (cv_signature == CvSignature::ElfBuildId) {
-    // ELF BuildID (found in Breakpad/Crashpad generated minidumps)
-    //
-    // This is variable-length, but usually 20 bytes
-    // as the binutils ld default is a SHA-1 hash.
-    // (We'll handle only 16 and 20 bytes signatures,
-    // matching LLDB support for UUIDs)
-    //
-    if (cv_record.size() == 16 || cv_record.size() == 20)
-      return UUID(cv_record.data(), cv_record.size());
-  }
+      return UUID::fromData(pdb70_uuid, sizeof(*pdb70_uuid));
+  } else if (cv_signature == CvSignature::ElfBuildId)
+    return UUID::fromData(cv_record);
 
   return UUID();
 }
diff --git a/lldb/source/Utility/DataExtractor.cpp b/lldb/source/Utility/DataExtractor.cpp
index 38481e004ce..947232943aa 100644
--- a/lldb/source/Utility/DataExtractor.cpp
+++ b/lldb/source/Utility/DataExtractor.cpp
@@ -1093,24 +1093,6 @@ lldb::offset_t DataExtractor::PutToLog(Log *log, offset_t start_offset,
   return offset; // Return the offset at which we ended up
 }
 
-//----------------------------------------------------------------------
-// DumpUUID
-//
-// Dump out a UUID starting at 'offset' bytes into the buffer
-//----------------------------------------------------------------------
-void DataExtractor::DumpUUID(Stream *s, offset_t offset) const {
-  if (s) {
-    const uint8_t *uuid_data = PeekData(offset, 16);
-    if (uuid_data) {
-      lldb_private::UUID uuid(uuid_data, 16);
-      uuid.Dump(s);
-    } else {
-      s->Printf("<not enough data for UUID at offset 0x%8.8" PRIx64 ">",
-                offset);
-    }
-  }
-}
-
 size_t DataExtractor::Copy(DataExtractor &dest_data) const {
   if (m_data_sp) {
     // we can pass along the SP to the data
diff --git a/lldb/source/Utility/UUID.cpp b/lldb/source/Utility/UUID.cpp
index dc2e8c035c0..3dfd5d957ea 100644
--- a/lldb/source/Utility/UUID.cpp
+++ b/lldb/source/Utility/UUID.cpp
@@ -21,29 +21,12 @@
 
 using namespace lldb_private;
 
-UUID::UUID() { Clear(); }
+UUID::UUID(llvm::ArrayRef<uint8_t> bytes) {
+  if (bytes.size() != 20 && bytes.size() != 16)
+    bytes = {};
 
-UUID::UUID(const UUID &rhs) {
-  SetBytes(rhs.m_uuid, rhs.m_num_uuid_bytes);
-}
-
-UUID::UUID(const void *uuid_bytes, uint32_t num_uuid_bytes) {
-  SetBytes(uuid_bytes, num_uuid_bytes);
-}
-
-const UUID &UUID::operator=(const UUID &rhs) {
-  if (this != &rhs) {
-    m_num_uuid_bytes = rhs.m_num_uuid_bytes;
-    ::memcpy(m_uuid, rhs.m_uuid, sizeof(m_uuid));
-  }
-  return *this;
-}
-
-UUID::~UUID() {}
-
-void UUID::Clear() {
-  m_num_uuid_bytes = 16;
-  ::memset(m_uuid, 0, sizeof(m_uuid));
+  m_num_uuid_bytes = bytes.size();
+  std::memcpy(m_uuid, bytes.data(), bytes.size());
 }
 
 std::string UUID::GetAsString(const char *separator) const {
@@ -74,38 +57,6 @@ void UUID::Dump(Stream *s) const {
   s->PutCString(GetAsString().c_str());
 }
 
-bool UUID::SetBytes(const void *uuid_bytes, uint32_t num_uuid_bytes) {
-  if (uuid_bytes) {
-    switch (num_uuid_bytes) {
-    case 20:
-      m_num_uuid_bytes = 20;
-      break;
-    case 16:
-      m_num_uuid_bytes = 16;
-      m_uuid[16] = m_uuid[17] = m_uuid[18] = m_uuid[19] = 0;
-      break;
-    default:
-      // Unsupported UUID byte size
-      m_num_uuid_bytes = 0;
-      break;
-    }
-
-    if (m_num_uuid_bytes > 0) {
-      ::memcpy(m_uuid, uuid_bytes, m_num_uuid_bytes);
-      return true;
-    }
-  }
-  ::memset(m_uuid, 0, sizeof(m_uuid));
-  return false;
-}
-
-bool UUID::IsValid() const {
-  return m_uuid[0] || m_uuid[1] || m_uuid[2] || m_uuid[3] || m_uuid[4] ||
-         m_uuid[5] || m_uuid[6] || m_uuid[7] || m_uuid[8] || m_uuid[9] ||
-         m_uuid[10] || m_uuid[11] || m_uuid[12] || m_uuid[13] || m_uuid[14] ||
-         m_uuid[15] || m_uuid[16] || m_uuid[17] || m_uuid[18] || m_uuid[19];
-}
-
 static inline int xdigit_to_int(char ch) {
   ch = tolower(ch);
   if (ch >= 'a' && ch <= 'f')
@@ -155,14 +106,15 @@ size_t UUID::SetFromStringRef(llvm::StringRef str, uint32_t num_uuid_bytes) {
   // Skip leading whitespace characters
   p = p.ltrim();
 
+  ValueType bytes;
   uint32_t bytes_decoded = 0;
   llvm::StringRef rest =
-      UUID::DecodeUUIDBytesFromString(p, m_uuid, bytes_decoded, num_uuid_bytes);
+      UUID::DecodeUUIDBytesFromString(p, bytes, bytes_decoded, num_uuid_bytes);
 
   // If we successfully decoded a UUID, return the amount of characters that
   // were consumed
   if (bytes_decoded == num_uuid_bytes) {
-    m_num_uuid_bytes = num_uuid_bytes;
+    *this = fromData(bytes, bytes_decoded);
     return str.size() - rest.size();
   }
 
diff --git a/lldb/unittests/Process/gdb-remote/GDBRemoteCommunicationClientTest.cpp b/lldb/unittests/Process/gdb-remote/GDBRemoteCommunicationClientTest.cpp
index 420e011803d..41ca091c8f1 100644
--- a/lldb/unittests/Process/gdb-remote/GDBRemoteCommunicationClientTest.cpp
+++ b/lldb/unittests/Process/gdb-remote/GDBRemoteCommunicationClientTest.cpp
@@ -194,7 +194,8 @@ TEST_F(GDBRemoteCommunicationClientTest, GetModulesInfo) {
   ASSERT_EQ(1u, result->size());
   EXPECT_EQ("/foo/bar.so", result.getValue()[0].GetFileSpec().GetPath());
   EXPECT_EQ(triple, result.getValue()[0].GetArchitecture().GetTriple());
-  EXPECT_EQ(UUID("@ABCDEFGHIJKLMNO", 16), result.getValue()[0].GetUUID());
+  EXPECT_EQ(UUID::fromData("@ABCDEFGHIJKLMNO", 16),
+            result.getValue()[0].GetUUID());
   EXPECT_EQ(0u, result.getValue()[0].GetObjectOffset());
   EXPECT_EQ(1234u, result.getValue()[0].GetObjectSize());
 }
@@ -218,7 +219,8 @@ TEST_F(GDBRemoteCommunicationClientTest, GetModulesInfo_UUID20) {
   ASSERT_EQ(1u, result->size());
   EXPECT_EQ("/foo/bar.so", result.getValue()[0].GetFileSpec().GetPath());
   EXPECT_EQ(triple, result.getValue()[0].GetArchitecture().GetTriple());
-  EXPECT_EQ(UUID("@ABCDEFGHIJKLMNOPQRS", 20), result.getValue()[0].GetUUID());
+  EXPECT_EQ(UUID::fromData("@ABCDEFGHIJKLMNOPQRS", 20),
+            result.getValue()[0].GetUUID());
   EXPECT_EQ(0u, result.getValue()[0].GetObjectOffset());
   EXPECT_EQ(1234u, result.getValue()[0].GetObjectSize());
 }
diff --git a/lldb/unittests/Utility/UUIDTest.cpp b/lldb/unittests/Utility/UUIDTest.cpp
index f66efa618e0..8c64d493680 100644
--- a/lldb/unittests/Utility/UUIDTest.cpp
+++ b/lldb/unittests/Utility/UUIDTest.cpp
@@ -15,10 +15,10 @@ using namespace lldb_private;
 
 TEST(UUIDTest, RelationalOperators) {
   UUID empty;
-  UUID a16("1234567890123456", 16);
-  UUID b16("1234567890123457", 16);
-  UUID a20("12345678901234567890", 20);
-  UUID b20("12345678900987654321", 20);
+  UUID a16 = UUID::fromData("1234567890123456", 16);
+  UUID b16 = UUID::fromData("1234567890123457", 16);
+  UUID a20 = UUID::fromData("12345678901234567890", 20);
+  UUID b20 = UUID::fromData("12345678900987654321", 20);
 
   EXPECT_EQ(empty, empty);
   EXPECT_EQ(a16, a16);
@@ -34,3 +34,40 @@ TEST(UUIDTest, RelationalOperators) {
   EXPECT_LT(a16, b16);
   EXPECT_GT(a20, b20);
 }
+
+TEST(UUIDTest, Validity) {
+  UUID empty;
+  std::vector<uint8_t> zeroes(20, 0);
+  UUID a16 = UUID::fromData(zeroes.data(), 16);
+  UUID a20 = UUID::fromData(zeroes.data(), 20);
+  UUID a16_0 = UUID::fromOptionalData(zeroes.data(), 16);
+  UUID a20_0 = UUID::fromOptionalData(zeroes.data(), 20);
+  EXPECT_FALSE(empty);
+  EXPECT_TRUE(a16);
+  EXPECT_TRUE(a20);
+  EXPECT_FALSE(a16_0);
+  EXPECT_FALSE(a20_0);
+}
+
+TEST(UUIDTest, SetFromStringRef) {
+  UUID u;
+  EXPECT_EQ(32u, u.SetFromStringRef("404142434445464748494a4b4c4d4e4f"));
+  EXPECT_EQ(UUID::fromData("@ABCDEFGHIJKLMNO", 16), u);
+
+  EXPECT_EQ(36u, u.SetFromStringRef("40-41-42-43-4445464748494a4b4c4d4e4f"));
+  EXPECT_EQ(UUID::fromData("@ABCDEFGHIJKLMNO", 16), u);
+
+  EXPECT_EQ(45u, u.SetFromStringRef(
+                     "40-41-42-43-4445464748494a4b4c4d4e4f-50515253", 20));
+  EXPECT_EQ(UUID::fromData("@ABCDEFGHIJKLMNOPQRS", 20), u);
+
+  EXPECT_EQ(0u, u.SetFromStringRef("40-41-42-43-4445464748494a4b4c4d4e4f", 20));
+  EXPECT_EQ(0u, u.SetFromStringRef("40xxxxx"));
+  EXPECT_EQ(0u, u.SetFromStringRef(""));
+  EXPECT_EQ(UUID::fromData("@ABCDEFGHIJKLMNOPQRS", 20), u)
+      << "uuid was changed by failed parse calls";
+
+  EXPECT_EQ(
+      32u, u.SetFromStringRef("404142434445464748494a4b4c4d4e4f-50515253", 16));
+  EXPECT_EQ(UUID::fromData("@ABCDEFGHIJKLMNO", 16), u);
+}