WIP: intrusive changes to upb_decoder.

5 files changed, 147 insertions, 158 deletions

diff --git a/src/upb.h b/src/upb.h
index c65a686..978ee5c 100644
--- a/src/upb.h
+++ b/src/upb.h
@@ -270,8 +270,8 @@ INLINE void upb_value_write(upb_valueptr ptr, upb_value val,
 enum upb_status_code {
   UPB_STATUS_OK = 0,
 
-  // The input byte stream ended in the middle of a record.
-  UPB_STATUS_NEED_MORE_DATA = 1,
+  // A read or write from a streaming src/sink could not be completed right now.
+  UPB_STATUS_TRYAGAIN = 1,
 
   // An unrecoverable error occurred.
   UPB_STATUS_ERROR = -1,
diff --git a/src/upb_decoder.c b/src/upb_decoder.c
index 32b8f16..5cb25a1 100644
--- a/src/upb_decoder.c
+++ b/src/upb_decoder.c
@@ -221,23 +221,6 @@ const uint8_t *upb_get_v_uint64_t_full(const uint8_t *buf, const uint8_t *end,
   return buf;
 }
 
-const uint8_t *upb_decode_wire_value(uint8_t *buf, uint8_t *end,
-                                     upb_wire_type_t wt, upb_wire_value *wv,
-                                     upb_status *status)
-{
-  switch(wt) {
-    case UPB_WIRE_TYPE_VARINT:
-      return upb_get_v_uint64_t(buf, end, &wv->varint, status);
-    case UPB_WIRE_TYPE_64BIT:
-      return upb_get_f_uint64_t(buf, end, &wv->_64bit, status);
-    case UPB_WIRE_TYPE_32BIT:
-      return upb_get_f_uint32_t(buf, end, &wv->_32bit, status);
-    default:
-      status->code = UPB_STATUS_ERROR;  // Doesn't handle delimited, groups.
-      return end;
-  }
-}
-
 // Advances buf past the current wire value (of type wt), saving the result in
 // outbuf.
 static const uint8_t *skip_wire_value(const uint8_t *buf, const uint8_t *end,
@@ -293,7 +276,7 @@ static const uint8_t *upb_decode_value(const uint8_t *buf, const uint8_t *end,
 typedef struct {
   upb_msgdef *msgdef;
   upb_fielddef *field;
-  size_t end_offset;  // For groups, 0.
+  int32_t end_offset;  // For groups, 0.
 } upb_decoder_frame;
 
 struct upb_decoder {
@@ -304,7 +287,15 @@ struct upb_decoder {
   // State pertaining to a particular decode (resettable).
   // Stack entries store the offset where the submsg ends (for groups, 0).
   upb_decoder_frame stack[UPB_MAX_NESTING], *top, *limit;
-  size_t completed_offset;
+
+  // The current buffer.
+  upb_string *buf;
+
+  // The overall stream offset of the beginning of this buffer.
+  uint32_t stream_offset;
+
+  // The current offset in this buffer.
+  uint32_t buffer_offset;
 };
 
 upb_decoder *upb_decoder_new(upb_msgdef *msgdef)
@@ -331,16 +322,6 @@ void upb_decoder_reset(upb_decoder *d, upb_sink *sink)
   d->top->end_offset = 0;
 }
 
-// Parses a tag, places the result in *tag.
-upb_key upb_decoder_src_getkey(upb_decoder *d)
-{
-  upb_key key;
-  upb_fill_buffer(d);
-  d->
-  const uint8_t *ret = upb_get_v_uint32_t(buf, end, &tag_int, status);
-  return ret;
-}
-
 
 
 static const void *get_msgend(upb_decoder *d, const uint8_t *start)
@@ -395,9 +376,78 @@ static const void *pop(upb_decoder *d, const uint8_t *start, upb_status *status)
   return get_msgend(d, start);
 }
 
+// Parses a tag, places the result in *tag.
+upb_fielddef *upb_decoder_src_getdef(upb_decoder *d)
+{
+  uint32_t key;
+  upb_fill_buffer(d);
+  d->buf = upb_get_v_uint32_t(d->buf, d->end, &key, &d->status);
+  if (!upb_ok(status)) return NULL;
+  if(upb_wiretype_from_key(key) == UPB_WIRE_TYPE_END_GROUP) {
+    if(!isgroup(d->submsg_end)) {
+      upb_seterr(d->status, UPB_STATUS_ERROR, "End group seen but current "
+                 "message is not a group, byte offset: %zd",
+                 d->completed_offset + (completed - start));
+      return NULL;
+    }
+    submsg_end = pop(d, start, status);
+    msgdef = d->top->msgdef;
+    completed = buf;
+    return NULL;
+  }
+  // Look up field by tag number.
+  return upb_msg_itof(d->top->msgdef, upb_fieldnum_from_key(key));
+}
 
-size_t upb_decoder_decode(upb_decoder *d, upb_strptr str, upb_status *status)
+bool upb_decoder_src_getval(upb_src *src, upb_valueptr val)
 {
+  if(upb_wiretype_from_key(d->key) == UPB_WIRE_TYPE_DELIMITED) {
+    int32_t delim_len;
+    d->buf = upb_get_INT32(d->buf, d->end, &delim_len, &d->status);
+    CHECK_STATUS();  // Checking decode_tag() and upb_get_INT32().
+    int32_t needed = 
+    const uint8_t *delim_end = buf + delim_len;
+    if(f->type == UPB_TYPE(MESSAGE)) {
+      submsg_end = push(d, start, delim_end - start, f, status);
+      msgdef = d->top->msgdef;
+    } else {
+      if(f && upb_isstringtype(f->type)) {
+        int32_t str_start = buf - start;
+        uint32_t len = str_start + delim_len;
+        sink_status = upb_sink_onstr(d->sink, f, str, str_start, len, status);
+      } // else { TODO: packed arrays }
+      // If field was not found, it is skipped silently.
+      buf = delim_end;  // Could be >end.
+    }
+  } else {
+    if(!upb_check_type(tag.wire_type, f->type)) {
+      buf = skip_wire_value(buf, end, tag.wire_type, status);
+    } else if (f->type == UPB_TYPE(GROUP)) {
+      submsg_end = push(d, start, 0, f, status);
+      msgdef = d->top->msgdef;
+    } else {
+      upb_value val;
+      buf = upb_decode_value(buf, end, f->type, upb_value_addrof(&val),
+                            status);
+      CHECK_STATUS();  // Checking upb_decode_value().
+      sink_status = upb_sink_onvalue(d->sink, f, val, status);
+    }
+  }
+  CHECK_STATUS();
+
+  while(buf >= submsg_end) {
+    if(buf > submsg_end) {
+      upb_seterr(status, UPB_STATUS_ERROR, "Expected submsg end offset "
+                 "did not lie on a tag/value boundary.");
+      goto err;
+    }
+    submsg_end = pop(d, start, status);
+    msgdef = d->top->msgdef;
+  }
+  // while(buf < d->packed_end) { TODO: packed arrays }
+  completed = buf;
+}
+
   // buf is our current offset, moves from start to end.
   const uint8_t *buf = (uint8_t*)upb_string_getrobuf(str);
   const uint8_t *const start = buf;  // ptr equivalent of d->completed_offset
@@ -421,68 +471,7 @@ size_t upb_decoder_decode(upb_decoder *d, upb_strptr str, upb_status *status)
     // Parse/handle tag.
     upb_tag tag;
     buf = decode_tag(buf, end, &tag, status);
-    if(tag.wire_type == UPB_WIRE_TYPE_END_GROUP) {
-      CHECK_STATUS();
-      if(!isgroup(submsg_end)) {
-        upb_seterr(status, UPB_STATUS_ERROR, "End group seen but current "
-                   "message is not a group, byte offset: %zd",
-                   d->completed_offset + (completed - start));
-        goto err;
-      }
-      submsg_end = pop(d, start, status);
-      msgdef = d->top->msgdef;
-      completed = buf;
-      continue;
-    }
-
-    // Look up field by tag number.
-    upb_fielddef *f = upb_msg_itof(msgdef, tag.field_number);
-
     // Parse/handle field.
-    if(tag.wire_type == UPB_WIRE_TYPE_DELIMITED) {
-      int32_t delim_len;
-      buf = upb_get_INT32(buf, end, &delim_len, status);
-      CHECK_STATUS();  // Checking decode_tag() and upb_get_INT32().
-      const uint8_t *delim_end = buf + delim_len;
-      if(f && f->type == UPB_TYPE(MESSAGE)) {
-        submsg_end = push(d, start, delim_end - start, f, status);
-        msgdef = d->top->msgdef;
-      } else {
-        if(f && upb_isstringtype(f->type)) {
-          int32_t str_start = buf - start;
-          uint32_t len = str_start + delim_len;
-          sink_status = upb_sink_onstr(d->sink, f, str, str_start, len, status);
-        } // else { TODO: packed arrays }
-        // If field was not found, it is skipped silently.
-        buf = delim_end;  // Could be >end.
-      }
-    } else {
-      if(!f || !upb_check_type(tag.wire_type, f->type)) {
-        buf = skip_wire_value(buf, end, tag.wire_type, status);
-      } else if (f->type == UPB_TYPE(GROUP)) {
-        submsg_end = push(d, start, 0, f, status);
-        msgdef = d->top->msgdef;
-      } else {
-        upb_value val;
-        buf = upb_decode_value(buf, end, f->type, upb_value_addrof(&val),
-                              status);
-        CHECK_STATUS();  // Checking upb_decode_value().
-        sink_status = upb_sink_onvalue(d->sink, f, val, status);
-      }
-    }
-    CHECK_STATUS();
-
-    while(buf >= submsg_end) {
-      if(buf > submsg_end) {
-        upb_seterr(status, UPB_STATUS_ERROR, "Expected submsg end offset "
-                   "did not lie on a tag/value boundary.");
-        goto err;
-      }
-      submsg_end = pop(d, start, status);
-      msgdef = d->top->msgdef;
-    }
-    // while(buf < d->packed_end) { TODO: packed arrays }
-    completed = buf;
   }
 
   size_t read;
diff --git a/src/upb_decoder.h b/src/upb_decoder.h
index b84c149..ea20d3d 100644
--- a/src/upb_decoder.h
+++ b/src/upb_decoder.h
@@ -39,15 +39,11 @@ void upb_decoder_free(upb_decoder *p);
 // state where it has not seen any data, and expects the next data to be from
 // the beginning of a new protobuf.  Parsers must be reset before they can be
 // used.  A decoder can be reset multiple times.
-void upb_decoder_reset(upb_decoder *p, upb_sink *sink);
-
-// Decodes protobuf data out of str, returning how much data was decoded.  The
-// next call to upb_decoder_decode should begin with the first byte that was
-// not decoded.  "status" indicates whether an error occurred.
-//
-// TODO: provide the following guarantee:
-//   retval will always be >= len.
-size_t upb_decoder_decode(upb_decoder *p, upb_strptr str, upb_status *status);
+void upb_decoder_reset(upb_decoder *p, upb_bytesrc *bytesrc);
+
+// Returns a upb_src pointer by which the decoder can be used.  The returned
+// upb_src is invalidated by upb_decoder_reset().
+upb_src *upb_decoder_getsrc(upb_decoder *p);
 
 #ifdef __cplusplus
 }  /* extern "C" */
diff --git a/src/upb_srcsink.h b/src/upb_srcsink.h
index 6dd11d1..97b9885 100644
--- a/src/upb_srcsink.h
+++ b/src/upb_srcsink.h
@@ -26,6 +26,8 @@ extern "C" {
 
 /* upb_src ********************************************************************/
 
+// TODO: decide how to handle unknown fields.
+
 // Retrieves the fielddef for the next field in the stream.  Returns NULL on
 // error or end-of-stream.
 upb_fielddef *upb_src_getdef(upb_src *src);
@@ -38,7 +40,8 @@ bool upb_src_getval(upb_src *src, upb_valueptr val);
 // Like upb_src_getval() but skips the value.
 bool upb_src_skipval(upb_src *src);
 
-// Descends into a submessage.
+// Descends into a submessage.  May only be called after a def has been
+// returned that indicates a submessage.
 bool upb_src_startmsg(upb_src *src);
 
 // Stops reading a submessage.  May be called before the stream is EOF, in
@@ -88,61 +91,61 @@ int32_t upb_bytesink_put(upb_bytesink *sink, upb_string *str);
 // Returns the current error status for the stream.
 upb_status *upb_bytesink_status(upb_bytesink *sink);
 
-/* upb_sink implementation ****************************************************/
-
-typedef struct upb_sink_callbacks {
-  upb_value_cb value_cb;
-  upb_str_cb str_cb;
-  upb_start_cb start_cb;
-  upb_end_cb end_cb;
-} upb_sink_callbacks;
-
-// These macros implement a mini virtual function dispatch for upb_sink instances.
-// This allows functions that call upb_sinks to just write:
-//
-//   upb_sink_onvalue(sink, field, val);
-//
-// The macro will handle the virtual function lookup and dispatch.  We could
-// potentially define these later to also be capable of calling a C++ virtual
-// method instead of doing the virtual dispatch manually.  This would make it
-// possible to write C++ sinks in a more natural style without loss of
-// efficiency.  We could have a flag in upb_sink defining whether it is a C
-// sink or a C++ one.
-#define upb_sink_onvalue(s, f, val, status) s->vtbl->value_cb(s, f, val, status)
-#define upb_sink_onstr(s, f, str, start, end, status) s->vtbl->str_cb(s, f, str, start, end, status)
-#define upb_sink_onstart(s, f, status) s->vtbl->start_cb(s, f, status)
-#define upb_sink_onend(s, f, status) s->vtbl->end_cb(s, f, status)
-
-// Initializes a plain C visitor with the given vtbl.  The sink must have been
-// allocated separately.
-INLINE void upb_sink_init(upb_sink *s, upb_sink_callbacks *vtbl) {
+/* Dynamic Dispatch implementation for src/sink interfaces ********************/
+
+// The rest of this file only concerns components that are implementing any of
+// the above interfaces.  To simple clients the code below should be considered
+// private.
+
+// Typedefs for function pointers to all of the above functions.
+typedef upb_fielddef (*upb_src_getdef_fptr)(upb_src *src);
+typedef bool (*upb_src_getval_fptr)(upb_src *src, upb_valueptr val);
+typedef bool (*upb_src_skipval_fptr)(upb_src *src);
+typedef bool (*upb_src_startmsg_fptr)(upb_src *src);
+typedef bool (*upb_src_endmsg_fptr)(upb_src *src);
+typedef upb_status *(*upb_src_status_fptr)(upb_src *src);
+
+typedef bool (*upb_sink_putdef_fptr)(upb_sink *sink, upb_fielddef *def);
+typedef bool (*upb_sink_putval_fptr)(upb_sink *sink, upb_value val);
+typedef bool (*upb_sink_startmsg_fptr)(upb_sink *sink);
+typedef bool (*upb_sink_endmsg_fptr)(upb_sink *sink);
+typedef upb_status *(*upb_sink_status_fptr)(upb_sink *sink);
+
+typedef upb_string *(*upb_bytesrc_get_fptr)(upb_bytesrc *src);
+typedef bool (*upb_bytesrc_append_fptr)(
+    upb_bytesrc *src, upb_string *str, upb_strlen_t len);
+typedef upb_status *(*upb_bytesrc_status_fptr)(upb_src *src);
+
+typedef int32_t (*upb_bytesink_put_fptr)(upb_bytesink *sink, upb_string *str);
+typedef upb_status *(*upb_bytesink_status_fptr)(upb_bytesink *sink);
+
+// Vtables for the above interfaces.
+typedef struct {
+  upb_src_getdef_fptr   getdef;
+  upb_src_getval_fptr   getval;
+  upb_src_skipval_fptr  skipval;
+  upb_src_startmsg_fptr startmsg;
+  upb_src_endmsg_fptr   endmsg;
+  upb_src_status_fptr   status;
+} upb_src_vtable;
+
+// "Base Class" definitions; components that implement these interfaces should
+// contain one of these structures.
+
+typedef struct {
+  upb_src_vtable *vtbl;
+#ifndef NDEBUG
+  int state;  // For debug-mode checking of API usage.
+#endif
+} upb_src;
+
+INLINE void upb_sink_init(upb_src *s, upb_src_vtable *vtbl) {
   s->vtbl = vtbl;
+#ifndef DEBUG
+  // TODO: initialize debug-mode checking.
+#endif
 }
 
-
-/* upb_bytesink ***************************************************************/
-
-// A upb_bytesink is like a upb_sync, but for bytes instead of structured
-// protobuf data.  Parsers implement upb_bytesink and push to a upb_sink,
-// serializers do the opposite (implement upb_sink and push to upb_bytesink).
-//
-// The two simplest kinds of sinks are "write to string" and "write to FILE*".
-
-// A forward declaration solely for the benefit of declaring upb_byte_cb below.
-// Always prefer upb_bytesink (without the "struct" keyword) instead.
-struct _upb_bytesink;
-
-// The single bytesink callback; it takes the bytes to be written and returns
-// how many were successfully written.  If the return value is <0, the caller
-// should stop processing.
-typedef int32_t (*upb_byte_cb)(struct _upb_bytesink *s, upb_strptr str,
-                               uint32_t start, uint32_t end,
-                               upb_status *status);
-
-typedef struct _upb_bytesink {
-  upb_byte_cb *cb;
-} upb_bytesink;
-
 #ifdef __cplusplus
 }  /* extern "C" */
 #endif
diff --git a/src/upb_string.h b/src/upb_string.h
index 0516377..c0d14d5 100644
--- a/src/upb_string.h
+++ b/src/upb_string.h
@@ -64,9 +64,10 @@ INLINE upb_strlen_t upb_string_len(upb_string *str) { return str->len; }
 
 // Use to read the bytes of the string.  The caller *must* call
 // upb_string_endread() after the data has been read.  The window between
-// upb_string_getrobuf() and upb_string_endread() should be kept as short
-// as possible.  No other functions may be called on the string during this
-// window except upb_string_len().
+// upb_string_getrobuf() and upb_string_endread() should be kept as short as
+// possible, because any pending upb_string_detach() may be blocked until
+// upb_string_endread is called().  No other functions may be called on the
+// string during this window except upb_string_len().
 INLINE const char *upb_string_getrobuf(upb_string *str) { return str->ptr; }
 INLINE void upb_string_endread(upb_string *str);