Re: [tarantool-patches] Re: [PATCH v5 2/9] lib: implement JSON tree class for json library

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Wed, Dec 05, 2018 at 12:07:40PM +0300, Vladimir Davydov wrote:
> On Wed, Dec 05, 2018 at 11:37:06AM +0300, Kirill Shcherbatov wrote:
> > Hi! Thank you for review.
> > 
> > >>> BTW, json array start indexing from 0, not 1 AFAIK. Starting indexing
> > >>> from 1 looks weird to me.
> > > 
> > > You left this comment from my previous review unattended.
> > 
> > In fact, it is not so; we use [token.num - 1] to retrieve field.
> > Let's better describe it in comment:
> > 	/**
> > 	 * Array of child records. Indexes in this array
> > 	 * match [token.num-1] index for JSON_TOKEN_NUM  type
> > 	 * and are allocated sequentially for JSON_TOKEN_STR child
> > 	 * tokens.
> > 	 */
> > 	struct json_token **children;
> 
> This is weird: AFAIU json_lexer may return token.num equal to 0.
> What happens if we try to insert such a token into a tree? I think 
> we should insert a token at children[token.num], not [toekn.num-1].

Discussed verbally. Agreed that we should pass index_base to
json_lexer_create, as we do, for example, in case of tuple_update.
json_lexer_next will subtract index_base from token.num before
returning the token. json_tree will use token.num as is when
inserting it into the children array. Tuple-related routines
will pass TUPLE_INDEX_BASE to json_lexer_create when parsing user
input so that Lua 1-base indexes are converted to 0-base.