Make the scanned form of the io_lib format strings available for processing

This adds three new functions to io_lib - scan_format/2, unscan_format/1,
and build_text/1 - which expose the parsed form of the format control
sequences to make it possible to easily modify or filter the input to
io_lib:format/2. This can e.g. be used in order to replace unbounded-size
control sequences like ~w or ~p with corresponding depth-limited ~W and ~P
before doing the actual formatting.

1 files changed, 40 insertions, 2 deletions

diff --git a/lib/stdlib/src/io_lib.erl b/lib/stdlib/src/io_lib.erl
index adc9a0cf5f..e90cda0533 100644
--- a/lib/stdlib/src/io_lib.erl
+++ b/lib/stdlib/src/io_lib.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2014. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -60,6 +60,7 @@
 -module(io_lib).
 
 -export([fwrite/2,fread/2,fread/3,format/2]).
+-export([scan_format/2,unscan_format/1,build_text/1]).
 -export([print/1,print/4,indentation/2]).
 
 -export([write/1,write/2,write/3,nl/0,format_prompt/1,format_prompt/2]).
@@ -83,7 +84,7 @@
          deep_unicode_char_list/1]).
 
 -export_type([chars/0, latin1_string/0, continuation/0,
-              fread_error/0, fread_item/0]).
+              fread_error/0, fread_item/0, format_spec/0]).
 
 %%----------------------------------------------------------------------
 
@@ -108,6 +109,18 @@
 
 -type fread_item() :: string() | atom() | integer() | float().
 
+-type format_spec() ::
+        #{
+           control_char => char(),
+           args         => [any()],
+           width        => 'none' | integer(),
+           adjust       => 'left' | 'right',
+           precision    => 'none' | integer(),
+           pad_char     => char(),
+           encoding     => 'unicode' | 'latin1',
+           strings      => boolean()
+         }.
+
 %%----------------------------------------------------------------------
 
 %% Interface calls to sub-modules.
@@ -156,6 +169,31 @@ format(Format, Args) ->
 	    Other
     end.
 
+-spec scan_format(Format, Data) -> FormatList when
+      Format :: io:format(),
+      Data :: [term()],
+      FormatList :: [char() | format_spec()].
+
+scan_format(Format, Args) ->
+    try io_lib_format:scan(Format, Args)
+    catch
+        _:_ -> erlang:error(badarg, [Format, Args])
+    end.
+
+-spec unscan_format(FormatList) -> {Format, Data} when
+      FormatList :: [char() | format_spec()],
+      Format :: io:format(),
+      Data :: [term()].
+
+unscan_format(FormatList) ->
+    io_lib_format:unscan(FormatList).
+
+-spec build_text(FormatList) -> chars() when
+      FormatList :: [char() | format_spec()].
+
+build_text(FormatList) ->
+    io_lib_format:build(FormatList).
+
 -spec print(Term) -> chars() when
       Term :: term().