Add some comments

src/parser3.h

@@ -17,6 +17,7 @@
 
 namespace parser3 {
 
+// Calling a continuation with buf == bufEnd means end of input
 typedef PRESERVE_NONE WeaselJsonStatus (*Continuation)(struct Parser3 *,
                                                        char *buf, char *bufEnd);
 
@@ -92,6 +93,9 @@ struct Parser3 {
     assert(!empty());
     --stackPtr;
   }
+
+  // Pushing symbols onto the stack roughly corresponds with "parse these
+  // nonterminals/terminals in order"
   [[nodiscard]] WeaselJsonStatus push(std::initializer_list<Symbol> symbols) {
     if (stackEnd - stackPtr < ptrdiff_t(symbols.size())) [[unlikely]] {
       return WeaselJson_OVERFLOW;
@@ -101,6 +105,7 @@ struct Parser3 {
     }
     return WeaselJson_OK;
   }
+
   [[nodiscard]] Symbol top() const {
     assert(!empty());
     return *(stackPtr - 1);
@@ -165,12 +170,13 @@ inline PRESERVE_NONE WeaselJsonStatus n_whitespace(Parser3 *self, char *buf,
 
 inline PRESERVE_NONE WeaselJsonStatus n_number(Parser3 *self, char *buf,
                                                char *bufEnd) {
-  bool complete = buf == bufEnd;
+  if (buf != bufEnd) {
     buf = (char *)self->numDfa.scan(buf, bufEnd);
-  if (buf == bufEnd && !complete) {
+    if (buf == bufEnd) {
       self->flushNumber(false, buf);
       return WeaselJson_AGAIN;
     }
+  }
   if (!self->numDfa.accept()) [[unlikely]] {
     return WeaselJson_REJECT;
   }