1 files changed, 23 insertions, 7 deletions
diff --git a/pw_varint/stream.cc b/pw_varint/stream.cc
index 00fe1fb37..83a80de08 100644
--- a/pw_varint/stream.cc
+++ b/pw_varint/stream.cc
@@ -16,8 +16,8 @@
 
 #include <cstddef>
 #include <cstdint>
-#include <span>
 
+#include "pw_span/span.h"
 #include "pw_status/status_with_size.h"
 #include "pw_stream/stream.h"
 #include "pw_varint/varint.h"
@@ -25,9 +25,9 @@
 namespace pw {
 namespace varint {
 
-StatusWithSize Read(stream::Reader& reader, int64_t* output) {
+StatusWithSize Read(stream::Reader& reader, int64_t* output, size_t max_size) {
   uint64_t value = 0;
-  StatusWithSize count = Read(reader, &value);
+  StatusWithSize count = Read(reader, &value, max_size);
   if (!count.ok()) {
     return count;
   }
@@ -36,18 +36,34 @@ StatusWithSize Read(stream::Reader& reader, int64_t* output) {
   return count;
 }
 
-StatusWithSize Read(stream::Reader& reader, uint64_t* output) {
+StatusWithSize Read(stream::Reader& reader, uint64_t* output, size_t max_size) {
   uint64_t value = 0;
   size_t count = 0;
 
   while (true) {
     if (count >= varint::kMaxVarint64SizeBytes) {
-      // Varint can't fit a uint64_t.
-      return StatusWithSize::OutOfRange();
+      // Varint can't fit a uint64_t, this likely means we're reading binary
+      // data that is not actually a varint.
+      return StatusWithSize::DataLoss();
+    }
+
+    if (count >= max_size) {
+      // Varint didn't fit within the range given; return OutOfRange() if
+      // max_size was 0, but DataLoss if we were reading something we thought
+      // was going to be a varint.
+      return count > 0 ? StatusWithSize::DataLoss()
+                       : StatusWithSize::OutOfRange();
     }
 
     std::byte b;
-    if (auto result = reader.Read(std::span(&b, 1)); !result.ok()) {
+    if (auto result = reader.Read(span(&b, 1)); !result.ok()) {
+      if (count > 0 && result.status().IsOutOfRange()) {
+        // Status::OutOfRange on the first byte means we tried to read a varint
+        // when we reached the end of file. But after the first byte it means we
+        // failed to decode a varint we were in the middle of, and that's not
+        // a normal error condition.
+        return StatusWithSize(Status::DataLoss(), 0);
+      }
       return StatusWithSize(result.status(), 0);
     }