Fixing a long-running issue in the TXR pattern language: premature

opening of files, prior to directives that actually need data.
The documentation basically lied that this is the case: namely,
the text "A file isn't opened until the query demands material from
that file, and then the contents are read on demand, not all at
once."   This is now a fact.

* match.c (non_matching_directive_table): New global variable.
(open_data_source): New static function. Contains an almost
verbatim migration of the source-opening logic that used
to be in match_files. The useless assignment to c->nil is gone,
and c->data == t is explicitly tested for. Instead of assuming
that only the @(next) directive does not need to have a data source
open, the table of non-matching directives is consulted. Opening
the data source is now skipped for numerous directives.
(match_files): Call open_data_source within the loop. This
means that even after processing numerous non-matching directives,
we will still correctly set up the data lazy list.
(dir_tables_init): Initialize non_matching_directive_table,
protect from GC and populate with numerous directives.

* txr.1: Improved documentation for @(next :args), and removed
a description of the hack that a single @(next) at the top of the
query suppressed the opening of the data source.

0 files changed, 0 insertions, 0 deletions