Put infer_length_after_decode in bin_decoder

src/core/ext/transport/chttp2/transport/bin_decoder.cc

@@ -75,6 +75,24 @@ static bool input_is_valid(uint8_t* input_ptr, size_t length) {
 #define COMPOSE_OUTPUT_BYTE_2(input_ptr) \
   (uint8_t)((decode_table[input_ptr[2]] << 6) | decode_table[input_ptr[3]])
 
+size_t grpc_base64_infer_length_after_decode(const grpc_slice& slice) {
+  size_t len = GRPC_SLICE_LENGTH(slice);
+  const uint8_t* bytes = GRPC_SLICE_START_PTR(slice);
+  while (len > 0 && bytes[len - 1] == '=') {
+    len--;
+  }
+  size_t tuples = len / 4;
+  size_t tail_case = len % 4;
+  if (tail_case == 1) {
+    gpr_log(GPR_ERROR,
+            "Base64 decoding failed. Input has a length of %zu (without"
+            " padding), which is invalid.\n",
+            len);
+    tail_case = 0;
+  }
+  return tuples * 3 + tail_xtra[tail_case];
+}
+
 bool grpc_base64_decode_partial(struct grpc_base64_decode_context* ctx) {
   size_t input_tail;
 

src/core/ext/transport/chttp2/transport/bin_decoder.h

@@ -48,4 +48,7 @@ grpc_slice grpc_chttp2_base64_decode(grpc_slice input);
 grpc_slice grpc_chttp2_base64_decode_with_length(grpc_slice input,
                                                  size_t output_length);
 
+/* Infer the length of decoded data from encoded data. */
+size_t grpc_base64_infer_length_after_decode(const grpc_slice& slice);
+
 #endif /* GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_BIN_DECODER_H */

src/core/ext/transport/cronet/transport/cronet_transport.cc

@@ -216,26 +216,6 @@ void grpc_cronet_stream_unref(stream_obj* s) { grpc_stream_unref(s->refcount); }
 
 static enum e_op_result execute_stream_op(struct op_and_state* oas);
 
-static const size_t tail_xtra[4] = {0, 0, 1, 2};
-
-static size_t infer_length_after_decode(const grpc_slice& slice) {
-  size_t len = GRPC_SLICE_LENGTH(slice);
-  const uint8_t* bytes = GRPC_SLICE_START_PTR(slice);
-  while (len > 0 && bytes[len - 1] == '=') {
-    len--;
-  }
-  size_t tuples = len / 4;
-  size_t tail_case = len % 4;
-  if (tail_case == 1) {
-    gpr_log(GPR_ERROR,
-            "Base64 decoding failed. Input has a length of %zu (without"
-            " padding), which is invalid.\n",
-            len);
-    tail_case = 0;
-  }
-  return tuples * 3 + tail_xtra[tail_case];
-}
-
 /*
   Utility function to translate enum into string for printing
 */
@@ -427,7 +407,7 @@ static void convert_cronet_array_to_metadata(
     if (grpc_is_binary_header(key)) {
       value = grpc_slice_from_static_string(header_array->headers[i].value);
       value = grpc_slice_intern(grpc_chttp2_base64_decode_with_length(
-          value, infer_length_after_decode(value)));
+          value, grpc_base64_infer_length_after_decode(value)));
     } else {
       value = grpc_slice_intern(
           grpc_slice_from_static_string(header_array->headers[i].value));