Added calculation of sizes for serialization (untested).

src/upb_msg.c

@@ -9,6 +9,7 @@
 #include "descriptor.h"
 #include "upb_msg.h"
 #include "upb_parse.h"
+#include "upb_serialize.h"
 
 /* Rounds p up to the next multiple of t. */
 #define ALIGN_UP(p, t) ((p) % (t) == 0 ? (p) : (p) + ((t) - ((p) % (t))))
@@ -248,7 +249,7 @@ void upb_msg_reuse_submsg(void **msg, struct upb_msg *m)
   if(!*msg) *msg = upb_msgdata_new(m);
 }
 
-/* Serialization/Deserialization.  ********************************************/
+/* Parsing.  ******************************************************************/
 
 static upb_field_type_t tag_cb(void *udata, struct upb_tag *tag,
                                void **user_field_desc)
@@ -390,6 +391,120 @@ void *upb_alloc_and_parse(struct upb_msg *m, struct upb_string *str, bool byref)
   }
 }
 
+/* Serialization.  ************************************************************/
+
+/* We store the message sizes linearly in post-order (size of parent after sizes
+ * of children) for a right-to-left traversal of the message tree.  Iterating
+ * over this in reverse gives us a pre-order (size of parent before sizes of
+ * children) left-to-right traversal, which is what we want for parsing. */
+struct upb_msgsizes {
+  int len;
+  int size;
+  size_t *sizes;
+};
+
+/* Declared below -- this and get_valuesize are mutually recursive. */
+static size_t get_msgsize(struct upb_msgsizes *sizes, void *data,
+                          struct upb_msg *m);
+
+/* Returns a size of a value as it will be serialized.  Does *not* include
+ * the size of the tag -- that is already accounted for. */
+static size_t get_valuesize(struct upb_msgsizes *sizes, union upb_value_ptr p,
+                            struct upb_msg_field *f,
+                            google_protobuf_FieldDescriptorProto *fd)
+{
+  switch(f->type) {
+    default: assert(false); return 0;  /* Internal corruption. */
+    case GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE_MESSAGE: {
+      size_t submsg_size = get_msgsize(sizes, p.msg, f->ref.msg);
+      return upb_get_INT32_size(submsg_size) + submsg_size;
+    }
+    case GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE_GROUP: {
+      size_t endgrp_tag_size = upb_get_tag_size(fd->number);
+      return endgrp_tag_size + get_msgsize(sizes, p.msg, f->ref.msg);
+    }
+#define CASE(type, member) \
+    case GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE_ ## type: \
+      return upb_get_ ## type ## _size(*p.member);
+    CASE(DOUBLE,   _double)
+    CASE(FLOAT,    _float)
+    CASE(INT32,    int32)
+    CASE(INT64,    int64)
+    CASE(UINT32,   uint32)
+    CASE(UINT64,   uint64)
+    CASE(SINT32,   int32)
+    CASE(SINT64,   int64)
+    CASE(FIXED32,  uint32)
+    CASE(FIXED64,  uint64)
+    CASE(SFIXED32, int32)
+    CASE(SFIXED64, int64)
+    CASE(BOOL,     _bool)
+    CASE(ENUM,     int32)
+#undef CASE
+  }
+}
+
+/* This is mostly just a pure recursive function to calculate the size of a
+ * message.  However it also stores the results of each level of the recursion
+ * in sizes, because we need all of this intermediate information later. */
+static size_t get_msgsize(struct upb_msgsizes *sizes, void *data,
+                          struct upb_msg *m)
+{
+  size_t size = 0;
+  /* We iterate over fields and arrays in reverse order. */
+  for(int32_t i = m->num_fields - 1; i >= 0; i--) {
+    struct upb_msg_field *f = &m->fields[i];
+    google_protobuf_FieldDescriptorProto *fd = upb_msg_field_descriptor(f, m);
+    if(!upb_msg_isset(data, f)) continue;
+    union upb_value_ptr p = upb_msg_getptr(data, f);
+    if(upb_isarray(f)) {
+      for(int32_t j = (*p.arr)->len - 1; j >= 0; j--) {
+        union upb_value_ptr elem = upb_array_getelementptr((*p.arr), j, f->type);
+        /* TODO: for packed arrays tag size goes outside the loop. */
+        size += upb_get_tag_size(fd->number);
+        size += get_valuesize(sizes, elem, f, fd);
+      }
+    } else {
+      size += upb_get_tag_size(fd->number);
+      size += get_valuesize(sizes, p, f, fd);
+    }
+  }
+  /* Resize the 'sizes' array if necessary. */
+  assert(sizes->len <= sizes->size);
+  if(sizes->len == sizes->size) {
+    sizes->size *= 2;
+    sizes->sizes = realloc(sizes->sizes, sizes->size * sizeof(size_t));
+  }
+  /* Add our size (already added our children, so post-order). */
+  sizes->sizes[sizes->len++] = size;
+  return size;
+}
+
+void upb_msgsizes_read(struct upb_msgsizes *sizes, void *data, struct upb_msg *m)
+{
+  get_msgsize(sizes, data, m);
+}
+
+/* Initialize/free a upb_msg_sizes for the given message. */
+void upb_msgsizes_init(struct upb_msgsizes *sizes)
+{
+  sizes->len = 0;
+  sizes->size = 0;
+  sizes->sizes = NULL;
+}
+
+void upb_msgsizes_free(struct upb_msgsizes *sizes)
+{
+  free(sizes->sizes);
+}
+
+size_t upb_msgsizes_totalsize(struct upb_msgsizes *sizes)
+{
+  return sizes->sizes[sizes->len-1];
+}
+
+/* Comparison.  ***************************************************************/
+
 bool upb_value_eql(union upb_value_ptr p1, union upb_value_ptr p2,
                    upb_field_type_t type)
 {

src/upb_msg.h

@@ -215,32 +215,39 @@ INLINE bool upb_isarray(struct upb_msg_field *f) {
 
 /* "Set" flag reading and writing.  *******************************************/
 
+/* Please note that these functions do not perform any memory management or in
+ * any way ensure that the fields are valid.  They *only* test/set/clear a bit
+ * that indicates whether the field is set or not. */
+
+/* Returns the byte offset where we store whether this field is set. */
 INLINE size_t upb_isset_offset(uint32_t field_index) {
   return field_index / 8;
 }
 
+/* Returns the mask within the appropriate byte that selects the set bit. */
 INLINE uint8_t upb_isset_mask(uint32_t field_index) {
   return 1 << (field_index % 8);
 }
 
-/* Functions for reading and writing the "set" flags in the msg.  Note that
+/* Returns true if the given field is set, false otherwise. */
- * these do not perform memory management associated with any dynamic memory
- * these fields may be referencing. These *only* set and test the flags. */
 INLINE void upb_msg_set(void *s, struct upb_msg_field *f)
 {
   ((char*)s)[upb_isset_offset(f->field_index)] |= upb_isset_mask(f->field_index);
 }
 
+/* Clears the set bit for this field in the given message. */
 INLINE void upb_msg_unset(void *s, struct upb_msg_field *f)
 {
   ((char*)s)[upb_isset_offset(f->field_index)] &= ~upb_isset_mask(f->field_index);
 }
 
+/* Tests whether the given field is set. */
 INLINE bool upb_msg_isset(void *s, struct upb_msg_field *f)
 {
   return ((char*)s)[upb_isset_offset(f->field_index)] & upb_isset_mask(f->field_index);
 }
 
+/* Returns true if *all* required fields are set, false otherwise. */
 INLINE bool upb_msg_all_required_fields_set(void *s, struct upb_msg *m)
 {
   int num_fields = m->num_required_fields;
@@ -253,6 +260,7 @@ INLINE bool upb_msg_all_required_fields_set(void *s, struct upb_msg *m)
   return true;
 }
 
+/* Clears the set bit for all fields. */
 INLINE void upb_msg_clear(void *s, struct upb_msg *m)
 {
   memset(s, 0, m->set_flags_bytes);
@@ -304,7 +312,7 @@ void upb_msg_reuse_array(struct upb_array **arr, uint32_t size,
 /* Reuse a submessage of the given type. */
 void upb_msg_reuse_submsg(void **msg, struct upb_msg *m);
 
-/* Serialization/Deserialization.  ********************************************/
+/* Parsing.  ******************************************************************/
 
 /* This is all just a layer on top of the stream-oriented facility in
  * upb_parse.h. */
@@ -352,6 +360,48 @@ upb_status_t upb_msg_parse(struct upb_msg_parse_state *s,
  * above.  "byref" works as in upb_msg_parse_init(). */
 void *upb_alloc_and_parse(struct upb_msg *m, struct upb_string *s, bool byref);
 
+/* Serialization  *************************************************************/
+
+/* For messages that contain any submessages, we must do a pre-pass on the
+ * message tree to discover the size of all submessages.  This is necessary
+ * because when serializing, the message length has to precede the message data
+ * itself.
+ *
+ * We can calculate these sizes once and reuse them as long as the message is
+ * known not to have changed. */
+struct upb_msgsizes;
+
+/* Initialize/free a upb_msgsizes for the given message. */
+void upb_msgsizes_init(struct upb_msgsizes *sizes);
+void upb_msgsizes_free(struct upb_msgsizes *sizes);
+
+/* Given a previously initialized sizes, recurse over the message and store its
+ * sizes in 'sizes'. */
+void upb_msgsizes_read(struct upb_msgsizes *sizes, void *data,
+                       struct upb_msg *m);
+
+/* Returns the total size of the serialized message given in sizes.  Must be
+ * preceeded by a call to upb_msgsizes_read. */
+size_t upb_msgsizes_totalsize(struct upb_msgsizes *sizes);
+
+struct upb_msg_serialize_state;
+
+/* Initializes the state of serialization.  The provided message must not
+ * change between the upb_msgsizes_read() call that was used to construct
+ * "sizes" and the parse being fully completed. */
+void upb_msg_serialize_alloc(struct upb_msg_serialize_state *s);
+void upb_msg_serialize_free(struct upb_msg_serialize_state *s);
+void upb_msg_serialize_init(struct upb_msg_serialize_state *s, void *data,
+                            struct upb_msg *m, struct upb_msgsizes *sizes);
+
+/* Serializes the next set of bytes into buf (which has size len).  Returns
+ * UPB_STATUS_OK if serialization is complete, or UPB_STATUS_NEED_MORE_DATA
+ * if there is more data from the message left to be serialized.
+ *
+ * The number of bytes written to buf is returned in *read.  This will be
+ * equal to len unless we finished serializing. */
+upb_status_t upb_msg_serialize(struct upb_msg_serialize_state *s,
+                               void *buf, size_t len, size_t *read);
 
 /* Text dump  *****************************************************************/
 

src/upb_parse.h

@@ -164,8 +164,7 @@ INLINE upb_status_t upb_get_v_uint32_t(uint8_t *buf, uint8_t *end,
 {
   uint64_t val64;
   UPB_CHECK(upb_get_v_uint64_t(buf, end, &val64, outbuf));
-  /* TODO: should we throw an error if any of the high bits in val64 are set? */
+  *val = (uint32_t)val64;  /* Discard the high bits. */
-  *val = (uint32_t)val64;
   return UPB_STATUS_OK;
 }
 

src/upb_serialize.h

@@ -44,11 +44,19 @@ INLINE upb_status_t upb_put_v_uint64_t(uint8_t *buf, uint8_t *end, uint64_t val,
   return UPB_STATUS_OK;
 }
 
-/* Puts a varint -- called when we only have 32 bits of data. */
+/* Puts an unsigned 32-bit varint, verbatim.  Never uses the high 64 bits. */
 INLINE upb_status_t upb_put_v_uint32_t(uint8_t *buf, uint8_t *end,
                                        uint32_t val, uint8_t **outbuf)
 {
-  return UPB_STATUS_OK;
+  return upb_put_v_uint64_t(buf, end, val, outbuf);
+}
+
+/* Puts a signed 32-bit varint, first sign-extending to 64-bits.  We do this to
+ * maintain wire-compatibility with 64-bit signed integers. */
+INLINE upb_status_t upb_put_v_int32_t(uint8_t *buf, uint8_t *end,
+                                      int32_t val, uint8_t **outbuf)
+{
+  return upb_put_v_uint64_t(buf, end, (int64_t)val, outbuf);
 }
 
 INLINE void upb_put32(uint8_t *buf, uint32_t val) {
@@ -183,9 +191,9 @@ T(FLOAT,    f, uint32_t, float,    _float)  {
 #undef PUT
 #undef T
 
-/* Functions to get sizes of serialized values without serializing. ***********/
+size_t upb_get_tag_size(uint32_t fieldnum) {
-
+  return upb_v_uint64_t_size((uint64_t)fieldnum << 3);
-
+}
 
 #ifdef __cplusplus
 }  /* extern "C" */