Store SSMC text without char-matrix padding

bindings/matlab/binsparse_to_ssmc_problem.m

@@ -442,16 +442,26 @@ function require_strictly_increasing(values, label)
 end
 
 function value = text_rows(value)
+% Rebuild a Matlab char matrix from metadata text.  The text is normally a
+% single multi-line string, but older files store an array of rows, so any
+% embedded line terminators are split out of every element.  Rows are never
+% deblanked here: whatever padding the writer kept is what char() needs to
+% restore the original width.
 if ischar(value)
-    return;
+    value = num2cell(value, 2);
 elseif isstring(value)
     value = cellstr(value(:));
 elseif iscellstr(value)
     value = value(:);
 else
     error('BinSparse:InvalidMetadata', 'notes must contain text');
 end
-value = char(value);
+rows = cell(0, 1);
+for k = 1:numel(value)
+    pieces = regexp(value{k}, '\r\n|\n|\r', 'split');
+    rows = [rows; pieces(:)];                                   %#ok<AGROW>
+end
+value = char(rows);
 end
 
 function value = normalize_component_text(value, use_cellstr)

bindings/matlab/binsparse_write_ssmc_problem.m

@@ -185,20 +185,23 @@ function write_string_dataset(output_filename, name, value)
               'BSP text output requires binsparse_write_string_dataset on the path');
     end
 
+    % Trailing blanks are stripped row by row, as sstextwrite does for the
+    % MM and RB formats.  A single row is left alone: it is the widest row,
+    % so its blanks are what a char() rebuild needs to recover the width.
     if isstring(value)
         if isscalar(value)
             value = char(value);
         else
-            value = cellstr(value(:));
+            value = strip_text_rows(value);
         end
     elseif ischar(value)
         if size(value, 1) > 1
-            value = char_rows(value);
+            value = strip_text_rows(value);
         else
             value = char(value);
         end
     elseif iscellstr(value)
-        value = value(:);
+        value = strip_text_rows(value);
     else
         error('binsparse_write_ssmc_problem:InvalidStringValue', ...
               'Text aux value must be char, string, or cellstr');
@@ -244,7 +247,7 @@ function write_string_dataset(output_filename, name, value)
     ok = false;
     if ischar(value)
         if size(value, 1) > 1
-            value = char_rows(value);
+            value = text_block(value);
         else
             value = char(value);
         end
@@ -253,21 +256,42 @@ function write_string_dataset(output_filename, name, value)
         if isscalar(value)
             value = char(value);
         else
-            value = cellstr(value(:));
+            value = text_block(value);
         end
         ok = true;
     elseif (islogical(value) || isnumeric(value)) && numel(value) <= 64
         ok = true;
     end
 end
 
-function rows = char_rows(value)
-    rows = cell(size(value, 1), 1);
-    for k = 1:size(value, 1)
-        rows{k} = value(k, :);
+function rows = strip_text_rows(value)
+    % Strip the trailing blanks that Matlab uses to pad the rows of a char
+    % matrix.  A reader rebuilds the matrix with char(), which pads every
+    % row to the longest one, so the original width survives only if some
+    % row reaches it; when none does, the widest row keeps just enough
+    % padding to preserve it.  The round trip is then exact, with trailing
+    % blanks left on at most one row.  Cell and string arrays carry no such
+    % padding, so their elements are simply stripped.
+    if ischar(value)
+        raw = num2cell(value, 2);
+        width = size(value, 2);
+    else
+        raw = cellstr(value(:));
+        width = 0;
+    end
+    rows = regexprep(raw, ' +$', '');
+    lengths = cellfun('length', rows);
+    if ~isempty(lengths) && max(lengths) < width
+        [~, k] = max(lengths);
+        rows{k} = [rows{k} repmat(' ', 1, width - lengths(k))];
     end
 end
 
+function text = text_block(value)
+    % Join multi-row text into a single multi-line string.
+    text = strjoin(reshape(strip_text_rows(value), 1, []), sprintf('\n'));
+end
+
 function json = encode_json_or_empty(value)
     try
         json = jsonencode(value);

bindings/matlab/test_binsparse_to_ssmc_problem.m

@@ -74,11 +74,43 @@
 assert(isequal(Problem.aux.seq{2}, [7; 8]));
 assert(isequal(Problem.aux.label, char({'abc'; 'def'})));
 
+% A stripped string dataset rebuilds the char matrix it was written from,
+% including the width carried by the widest row.
+raw.aux.label = {'hello '; 'there'};
+Problem = binsparse_to_ssmc_problem(raw);
+assert(isequal(Problem.aux.label, ['hello '; 'there ']), ...
+    'stripped string dataset mismatch');
+
 dmat = dense_matrix([1; 2; 3; 4; 5; 6], 2, 3, 'DMAT');
 raw = struct('metadata', metadata, 'A', formats{1}, 'b', dmat);
 Problem = binsparse_to_ssmc_problem(raw);
 assert(isequal(Problem.b, [1 2 3; 4 5 6]));
 
+% notes may be a single multi-line string, and blank rows are preserved.
+notes_meta = metadata;
+notes_meta.notes = sprintf('a longest line with trailing space \nshort\n\nlast');
+Problem = binsparse_to_ssmc_problem( ...
+    struct('metadata', notes_meta, 'A', formats{1}));
+assert(isequal(Problem.notes, char({'a longest line with trailing space '; ...
+    'short'; ''; 'last'})), 'multi-line notes mismatch');
+assert(isequal(size(Problem.notes), [4 35]), 'multi-line notes width mismatch');
+
+notes_meta.notes = sprintf('abc\n');
+Problem = binsparse_to_ssmc_problem( ...
+    struct('metadata', notes_meta, 'A', formats{1}));
+assert(isequal(Problem.notes, char({'abc'; ''})), 'trailing blank note row lost');
+
+% Padded row arrays written by older versions read back the same way.
+notes_meta.notes = {'first note '; 'second note'};
+legacy = binsparse_to_ssmc_problem( ...
+    struct('metadata', notes_meta, 'A', formats{1}));
+notes_meta.notes = sprintf('first note\nsecond note');
+joined = binsparse_to_ssmc_problem( ...
+    struct('metadata', notes_meta, 'A', formats{1}));
+assert(isequal(legacy.notes, joined.notes), ...
+    'legacy and multi-line notes disagree');
+assert(isequal(joined.notes, char({'first note'; 'second note'})));
+
 bad = formats{1};
 bad.indices_1([1 2]) = bad.indices_1([2 1]);
 assert_throws(@() binsparse_to_ssmc_problem( ...

bindings/matlab/test_binsparse_write_ssmc_problem.m

@@ -53,6 +53,7 @@ function test_binsparse_write_ssmc_problem()
 Problem.aux.D = [1 0 2; 3 4 5];
 Problem.aux.S = sparse([1 2], [2 3], [9 8], 3, 3);
 Problem.aux.note = ['hello '; 'there '];
+Problem.aux.note2 = ['hello!'; 'there '];
 Problem.aux.tags = {'alpha'; 'beta'};
 
 problem = struct('Problem', Problem);
@@ -84,15 +85,49 @@ function test_binsparse_write_ssmc_problem()
 expected_sparse = full(Problem.aux.S);
 assert(matrices_equal(aux_sparse_mat, expected_sparse), 'Aux sparse matrix mismatch');
 
-check_string_dataset(out_file, 'note', {'hello '; 'there '});
+% String datasets are stripped row by row.  No row of note reaches the char
+% matrix width, so the widest row keeps one blank; note2 needs none.  Either
+% way char() rebuilds the original char matrix exactly.
+check_string_dataset(out_file, 'note', {'hello '; 'there'});
+check_string_dataset(out_file, 'note2', {'hello!'; 'there'});
 check_string_dataset(out_file, 'tags', {'alpha'; 'beta'});
+assert(isequal(char(as_cellstr(h5read(out_file, '/note'))), Problem.aux.note), ...
+       'Aux note round trip is not exact');
+assert(isequal(char(as_cellstr(h5read(out_file, '/note2'))), Problem.aux.note2), ...
+       'Aux note2 round trip is not exact');
 
 json = h5readatt(out_file, '/', 'binsparse');
 assert(contains(json, '"metadata"'), 'Primary metadata not nested');
 assert(~isempty(regexp(json, '"id"\s*:\s*7', 'once')), ...
        'Primary metadata id is not a JSON number');
 assert(~contains(json, '"ssmc_metadata"'), 'Unexpected legacy metadata key');
 
+% notes are stored as one multi-line string.  Trailing blanks are stripped,
+% except on the widest row when that row is what carries the char matrix
+% width, so that char() rebuilds the original notes exactly.
+decoded = jsondecode(json);
+notes_text = decoded.metadata.notes;
+assert(ischar(notes_text) && isrow(notes_text), ...
+       'Notes metadata is not a single string');
+assert(isequal(notes_text, sprintf('first note\nsecond note ')), ...
+       'Notes metadata text mismatch');
+rebuilt = char(regexp(notes_text, '\r\n|\n|\r', 'split'));
+assert(isequal(rebuilt, Problem.notes), 'Notes round trip is not exact');
+
+% When the widest row has no padding, no trailing blanks survive at all.
+clean = Problem;
+clean.notes = ['abc'; 'de '];
+clean_file = [tempname() '.bsp.h5'];
+cleanup_clean = onCleanup(@() delete_if_exists(clean_file)); %#ok<NASGU>
+binsparse_write_ssmc_problem(struct('Problem', clean), clean_file, ...
+                             format, compression_level);
+clean_notes = jsondecode(h5readatt(clean_file, '/', 'binsparse'));
+clean_notes = clean_notes.metadata.notes;
+assert(isequal(clean_notes, sprintf('abc\nde')), ...
+       'Notes metadata retained recoverable padding');
+assert(isequal(char(regexp(clean_notes, '\n', 'split')), clean.notes), ...
+       'Notes round trip is not exact');
+
 fprintf('Test passed.\n');
 
 end