Revise APIs for pushJsonbValue() and associated routines.

Instead of passing "JsonbParseState **" to pushJsonbValue(),
pass a pointer to a JsonbInState, which will contain the
parseState stack pointer as well as other useful fields.
Also, instead of returning a JsonbValue pointer that is often
meaningless/ignored, return the top-level JsonbValue pointer
in the "result" field of the JsonbInState.

This involves a lot of (mostly mechanical) edits, but I think
the results are notationally cleaner and easier to understand.
Certainly the business with sometimes capturing the result of
pushJsonbValue() and sometimes not was bug-prone and incapable of
mechanical verification.  In the new arrangement, JsonbInState.result
remains null until we've completed a valid sequence of pushes, so
that an incorrect sequence will result in a null-pointer dereference,
not mistaken use of a partial result.

However, this isn't simply an exercise in prettier notation.
The real reason for doing it is to provide a mechanism whereby
pushJsonbValue() can be told to construct the JsonbValue tree
in a context that is not CurrentMemoryContext.  That happens
when a non-null "outcontext" is specified in the JsonbInState.
No callers exercise that option in this patch, but the next
patch in the series will make use of it.

I tried to improve the comments in this area too.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: jian he <jian.universality@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/1060917.1753202222@sss.pgh.pa.us

1 files changed, 12 insertions, 14 deletions

diff --git a/contrib/hstore/hstore_io.c b/contrib/hstore/hstore_io.c
index 6b01f27c5a4..34e3918811c 100644
--- a/contrib/hstore/hstore_io.c
+++ b/contrib/hstore/hstore_io.c
@@ -1439,10 +1439,9 @@ hstore_to_jsonb(PG_FUNCTION_ARGS)
 	int			count = HS_COUNT(in);
 	char	   *base = STRPTR(in);
 	HEntry	   *entries = ARRPTR(in);
-	JsonbParseState *state = NULL;
-	JsonbValue *res;
+	JsonbInState state = {0};
 
-	(void) pushJsonbValue(&state, WJB_BEGIN_OBJECT, NULL);
+	pushJsonbValue(&state, WJB_BEGIN_OBJECT, NULL);
 
 	for (i = 0; i < count; i++)
 	{
@@ -1453,7 +1452,7 @@ hstore_to_jsonb(PG_FUNCTION_ARGS)
 		key.val.string.len = HSTORE_KEYLEN(entries, i);
 		key.val.string.val = HSTORE_KEY(entries, base, i);
 
-		(void) pushJsonbValue(&state, WJB_KEY, &key);
+		pushJsonbValue(&state, WJB_KEY, &key);
 
 		if (HSTORE_VALISNULL(entries, i))
 		{
@@ -1465,12 +1464,12 @@ hstore_to_jsonb(PG_FUNCTION_ARGS)
 			val.val.string.len = HSTORE_VALLEN(entries, i);
 			val.val.string.val = HSTORE_VAL(entries, base, i);
 		}
-		(void) pushJsonbValue(&state, WJB_VALUE, &val);
+		pushJsonbValue(&state, WJB_VALUE, &val);
 	}
 
-	res = pushJsonbValue(&state, WJB_END_OBJECT, NULL);
+	pushJsonbValue(&state, WJB_END_OBJECT, NULL);
 
-	PG_RETURN_POINTER(JsonbValueToJsonb(res));
+	PG_RETURN_POINTER(JsonbValueToJsonb(state.result));
 }
 
 PG_FUNCTION_INFO_V1(hstore_to_jsonb_loose);
@@ -1482,13 +1481,12 @@ hstore_to_jsonb_loose(PG_FUNCTION_ARGS)
 	int			count = HS_COUNT(in);
 	char	   *base = STRPTR(in);
 	HEntry	   *entries = ARRPTR(in);
-	JsonbParseState *state = NULL;
-	JsonbValue *res;
+	JsonbInState state = {0};
 	StringInfoData tmp;
 
 	initStringInfo(&tmp);
 
-	(void) pushJsonbValue(&state, WJB_BEGIN_OBJECT, NULL);
+	pushJsonbValue(&state, WJB_BEGIN_OBJECT, NULL);
 
 	for (i = 0; i < count; i++)
 	{
@@ -1499,7 +1497,7 @@ hstore_to_jsonb_loose(PG_FUNCTION_ARGS)
 		key.val.string.len = HSTORE_KEYLEN(entries, i);
 		key.val.string.val = HSTORE_KEY(entries, base, i);
 
-		(void) pushJsonbValue(&state, WJB_KEY, &key);
+		pushJsonbValue(&state, WJB_KEY, &key);
 
 		if (HSTORE_VALISNULL(entries, i))
 		{
@@ -1541,10 +1539,10 @@ hstore_to_jsonb_loose(PG_FUNCTION_ARGS)
 				val.val.string.val = HSTORE_VAL(entries, base, i);
 			}
 		}
-		(void) pushJsonbValue(&state, WJB_VALUE, &val);
+		pushJsonbValue(&state, WJB_VALUE, &val);
 	}
 
-	res = pushJsonbValue(&state, WJB_END_OBJECT, NULL);
+	pushJsonbValue(&state, WJB_END_OBJECT, NULL);
 
-	PG_RETURN_POINTER(JsonbValueToJsonb(res));
+	PG_RETURN_POINTER(JsonbValueToJsonb(state.result));
 }