Sync from internal Google development.

Many improvements, too many to mention.  One significant
perf regression warrants investigation:

omitfp.parsetoproto2_googlemessage1.upb_jit: 343 -> 252 (-26.53)
plain.parsetoproto2_googlemessage1.upb_jit: 334 -> 251 (-24.85)

25% regression for this benchmark is bad, but since I don't think
there's any fundamental design issue that caused it I'm going to
go ahead with the commit anyway.  Can investigate and fix later.

Other benchmarks were neutral or showed slight improvement.

1 files changed, 33 insertions, 0 deletions

diff --git a/bindings/cpp/upb/bytestream.hpp b/bindings/cpp/upb/bytestream.hpp
index 968d542..81134b9 100644
--- a/bindings/cpp/upb/bytestream.hpp
+++ b/bindings/cpp/upb/bytestream.hpp
@@ -68,6 +68,7 @@
 
 #include "upb/bytestream.h"
 #include "upb/upb.hpp"
+#include <string>
 
 namespace upb {
 
@@ -204,6 +205,18 @@ class ByteRegion : public upb_byteregion {
     return upb_byteregion_strdup(this);
   }
 
+  template <typename T> void AssignToString(T* str) {
+    uint64_t ofs = start_ofs();
+    str->clear();
+    str->reserve(Length());
+    while (ofs < end_ofs()) {
+      size_t len;
+      const char *ptr = GetPtr(ofs, &len);
+      str->append(ptr, len);
+      ofs += len;
+    }
+  }
+
   // TODO: add if/when there is a demonstrated need.
   //
   // // Pins this byteregion's bytes in memory, allowing it to outlive its
@@ -220,12 +233,24 @@ class ByteRegion : public upb_byteregion {
 class StringSource : public upb_stringsrc {
  public:
   StringSource() : upb_stringsrc() { upb_stringsrc_init(this); }
+  template <typename T> explicit StringSource(const T& str) {
+    upb_stringsrc_init(this);
+    Reset(str);
+  }
+  StringSource(const char *data, size_t len) {
+    upb_stringsrc_init(this);
+    Reset(data, len);
+  }
   ~StringSource() { upb_stringsrc_uninit(this); }
 
   void Reset(const char* data, size_t len) {
     upb_stringsrc_reset(this, data, len);
   }
 
+  template <typename T> void Reset(const T& str) {
+    Reset(str.c_str(), str.size());
+  }
+
   ByteRegion* AllBytes() {
     return static_cast<ByteRegion*>(upb_stringsrc_allbytes(this));
   }
@@ -233,6 +258,14 @@ class StringSource : public upb_stringsrc {
   upb_bytesrc* ByteSource() { return upb_stringsrc_bytesrc(this); }
 };
 
+template <> inline ByteRegion* GetValue<ByteRegion*>(Value v) {
+  return static_cast<ByteRegion*>(upb_value_getbyteregion(v));
+}
+
+template <> inline Value MakeValue<ByteRegion*>(ByteRegion* v) {
+  return upb_value_byteregion(v);
+}
+
 }  // namespace upb
 
 #endif