Coalesced some grpc_slice_buffer_tiny_add calls in hpack_enc

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

@@ -381,10 +381,11 @@ static void emit_lithdr_incidx(grpc_chttp2_hpack_compressor* c,
   uint32_t len_val_len;
   GPR_ASSERT(len_val <= UINT32_MAX);
   len_val_len = GRPC_CHTTP2_VARINT_LENGTH((uint32_t)len_val, 1);
-  GRPC_CHTTP2_WRITE_VARINT(key_index, 2, 0x40,
+  GPR_DEBUG_ASSERT(len_pfx + len_val_len < GRPC_SLICE_INLINED_SIZE);
-                           add_tiny_header_data(st, len_pfx), len_pfx);
+  uint8_t* data = add_tiny_header_data(st, len_pfx + len_val_len);
+  GRPC_CHTTP2_WRITE_VARINT(key_index, 2, 0x40, data, len_pfx);
   GRPC_CHTTP2_WRITE_VARINT((uint32_t)len_val, 1, value.huffman_prefix,
-                           add_tiny_header_data(st, len_val_len), len_val_len);
+                           &data[len_pfx], len_val_len);
   add_wire_value(st, value);
 }
 
@@ -398,10 +399,11 @@ static void emit_lithdr_noidx(grpc_chttp2_hpack_compressor* c,
   uint32_t len_val_len;
   GPR_ASSERT(len_val <= UINT32_MAX);
   len_val_len = GRPC_CHTTP2_VARINT_LENGTH((uint32_t)len_val, 1);
-  GRPC_CHTTP2_WRITE_VARINT(key_index, 4, 0x00,
+  GPR_DEBUG_ASSERT(len_pfx + len_val_len < GRPC_SLICE_INLINED_SIZE);
-                           add_tiny_header_data(st, len_pfx), len_pfx);
+  uint8_t* data = add_tiny_header_data(st, len_pfx + len_val_len);
+  GRPC_CHTTP2_WRITE_VARINT(key_index, 4, 0x00, data, len_pfx);
   GRPC_CHTTP2_WRITE_VARINT((uint32_t)len_val, 1, value.huffman_prefix,
-                           add_tiny_header_data(st, len_val_len), len_val_len);
+                           &data[len_pfx], len_val_len);
   add_wire_value(st, value);
 }
 
@@ -418,9 +420,10 @@ static void emit_lithdr_incidx_v(grpc_chttp2_hpack_compressor* c,
   uint32_t len_val_len = GRPC_CHTTP2_VARINT_LENGTH(len_val, 1);
   GPR_ASSERT(len_key <= UINT32_MAX);
   GPR_ASSERT(wire_value_length(value) <= UINT32_MAX);
-  *add_tiny_header_data(st, 1) = 0x40;
+  GPR_DEBUG_ASSERT(1 + len_key_len < GRPC_SLICE_INLINED_SIZE);
-  GRPC_CHTTP2_WRITE_VARINT(len_key, 1, 0x00,
+  uint8_t* data = add_tiny_header_data(st, 1 + len_key_len);
-                           add_tiny_header_data(st, len_key_len), len_key_len);
+  data[0] = 0x40;
+  GRPC_CHTTP2_WRITE_VARINT(len_key, 1, 0x00, &data[1], len_key_len);
   add_header_data(st, grpc_slice_ref_internal(GRPC_MDKEY(elem)));
   GRPC_CHTTP2_WRITE_VARINT(len_val, 1, value.huffman_prefix,
                            add_tiny_header_data(st, len_val_len), len_val_len);
@@ -440,9 +443,10 @@ static void emit_lithdr_noidx_v(grpc_chttp2_hpack_compressor* c,
   uint32_t len_val_len = GRPC_CHTTP2_VARINT_LENGTH(len_val, 1);
   GPR_ASSERT(len_key <= UINT32_MAX);
   GPR_ASSERT(wire_value_length(value) <= UINT32_MAX);
-  *add_tiny_header_data(st, 1) = 0x00;
+  /* Preconditions passed; emit header. */
-  GRPC_CHTTP2_WRITE_VARINT(len_key, 1, 0x00,
+  uint8_t* data = add_tiny_header_data(st, 1 + len_key_len);
-                           add_tiny_header_data(st, len_key_len), len_key_len);
+  data[0] = 0x00;
+  GRPC_CHTTP2_WRITE_VARINT(len_key, 1, 0x00, &data[1], len_key_len);
   add_header_data(st, grpc_slice_ref_internal(GRPC_MDKEY(elem)));
   GRPC_CHTTP2_WRITE_VARINT(len_val, 1, value.huffman_prefix,
                            add_tiny_header_data(st, len_val_len), len_val_len);

src/core/lib/slice/slice_buffer.cc

@@ -103,7 +103,7 @@ uint8_t* grpc_slice_buffer_tiny_add(grpc_slice_buffer* sb, size_t n) {
 
   sb->length += n;
 
-  if (sb->count == 0) goto add_new;
+  if (sb->count == 0) goto add_first;
   back = &sb->slices[sb->count - 1];
   if (back->refcount) goto add_new;
   if ((back->data.inlined.length + n) > sizeof(back->data.inlined.bytes))
@@ -115,6 +115,7 @@ uint8_t* grpc_slice_buffer_tiny_add(grpc_slice_buffer* sb, size_t n) {
 
 add_new:
   maybe_embiggen(sb);
+add_first:
   back = &sb->slices[sb->count];
   sb->count++;
   back->refcount = nullptr;