Refinement of upb_bytesrc interface.

Added a upb_byteregion that tracks a region of
the input buffer; decoders use this instead of
using a upb_bytesrc directly.  upb_byteregion
is also used as the way of passing a string to
a upb_handlers callback.  This symmetry makes
decoders compose better; if you want to take
a parsed string and decode it as something else,
you can take the string directly from the callback
and feed it as input to another parser.

A commented-out version of a pinning interface
is present; I decline to actually implement it
(and accept its extra complexity) until/unless
it is clear that it is actually a win.  But it
is included as a proof-of-concept, to show that
it fits well with the existing interface.

1 files changed, 6 insertions, 5 deletions

diff --git a/upb/msg.c b/upb/msg.c
index 87bb61b..78309cf 100644
--- a/upb/msg.c
+++ b/upb/msg.c
@@ -151,13 +151,14 @@ static void _upb_stdmsg_setstr(void *_dst, upb_value src) {
     *dstp = dst;
   }
   dst->len = 0;
-  const upb_strref *ref = upb_value_getstrref(src);
-  if (ref->len > dst->size) {
-    dst->size = ref->len;
+  const upb_byteregion *bytes = upb_value_getbyteregion(src);
+  uint32_t len = upb_byteregion_len(bytes);
+  if (len > dst->size) {
+    dst->size = len;
     dst->ptr = realloc(dst->ptr, dst->size);
   }
-  dst->len = ref->len;
-  upb_bytesrc_read(ref->bytesrc, ref->stream_offset, ref->len, dst->ptr);
+  dst->len = len;
+  upb_byteregion_copyall(bytes, dst->ptr);
 }
 
 upb_flow_t upb_stdmsg_setstr(void *_m, upb_value fval, upb_value val) {