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std.debug: optimized printLineFromFileAnyOs (#18142)
* std.debug: optimized printLineFromFileAnyOs Uses mem.indexOfScalar to speed line iteration instead of byte for byte. Also prints the whole line in a single write (or up to a page size at a time) Closes #18099 * add test cases for printLineFromFileAnyOs
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tjog
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@ -1395,31 +1395,169 @@ fn printLineFromFileAnyOs(out_stream: anytype, line_info: LineInfo) !void {
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// TODO fstat and make sure that the file has the correct size
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var buf: [mem.page_size]u8 = undefined;
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var line: usize = 1;
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var column: usize = 1;
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while (true) {
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const amt_read = try f.read(buf[0..]);
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const slice = buf[0..amt_read];
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for (slice) |byte| {
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if (line == line_info.line) {
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switch (byte) {
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'\t' => try out_stream.writeByte(' '),
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else => try out_stream.writeByte(byte),
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}
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if (byte == '\n') {
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return;
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}
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}
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if (byte == '\n') {
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line += 1;
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column = 1;
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var amt_read = try f.read(buf[0..]);
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const line_start = seek: {
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var current_line_start: usize = 0;
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var next_line: usize = 1;
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while (next_line != line_info.line) {
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const slice = buf[current_line_start..amt_read];
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if (mem.indexOfScalar(u8, slice, '\n')) |pos| {
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next_line += 1;
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if (pos == slice.len - 1) {
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amt_read = try f.read(buf[0..]);
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current_line_start = 0;
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} else current_line_start += pos + 1;
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} else if (amt_read < buf.len) {
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return error.EndOfFile;
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} else {
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column += 1;
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amt_read = try f.read(buf[0..]);
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current_line_start = 0;
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}
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}
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break :seek current_line_start;
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};
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const slice = buf[line_start..amt_read];
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if (mem.indexOfScalar(u8, slice, '\n')) |pos| {
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const line = slice[0 .. pos + 1];
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mem.replaceScalar(u8, line, '\t', ' ');
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return out_stream.writeAll(line);
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} else { // Line is the last inside the buffer, and requires another read to find delimiter. Alternatively the file ends.
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mem.replaceScalar(u8, slice, '\t', ' ');
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try out_stream.writeAll(slice);
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while (amt_read == buf.len) {
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amt_read = try f.read(buf[0..]);
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if (mem.indexOfScalar(u8, buf[0..amt_read], '\n')) |pos| {
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const line = buf[0 .. pos + 1];
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mem.replaceScalar(u8, line, '\t', ' ');
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return out_stream.writeAll(line);
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} else {
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const line = buf[0..amt_read];
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mem.replaceScalar(u8, line, '\t', ' ');
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try out_stream.writeAll(line);
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}
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}
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// Make sure printing last line of file inserts extra newline
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try out_stream.writeByte('\n');
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}
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}
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if (amt_read < buf.len) return error.EndOfFile;
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test "printLineFromFileAnyOs" {
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var output = std.ArrayList(u8).init(std.testing.allocator);
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defer output.deinit();
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const output_stream = output.writer();
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const allocator = std.testing.allocator;
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const join = std.fs.path.join;
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const expectError = std.testing.expectError;
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const expectEqualStrings = std.testing.expectEqualStrings;
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var test_dir = std.testing.tmpDir(.{});
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defer test_dir.cleanup();
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// Relies on testing.tmpDir internals which is not ideal, but LineInfo requires paths.
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const test_dir_path = try join(allocator, &.{ "zig-cache", "tmp", test_dir.sub_path[0..] });
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defer allocator.free(test_dir_path);
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// Cases
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{
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const path = try join(allocator, &.{ test_dir_path, "one_line.zig" });
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defer allocator.free(path);
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try test_dir.dir.writeFile("one_line.zig", "no new lines in this file, but one is printed anyway");
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try expectError(error.EndOfFile, printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = 2, .column = 0 }));
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try printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = 1, .column = 0 });
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try expectEqualStrings("no new lines in this file, but one is printed anyway\n", output.items);
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output.clearRetainingCapacity();
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}
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{
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const path = try fs.path.join(allocator, &.{ test_dir_path, "three_lines.zig" });
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defer allocator.free(path);
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try test_dir.dir.writeFile("three_lines.zig",
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\\1
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\\2
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\\3
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);
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try printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = 1, .column = 0 });
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try expectEqualStrings("1\n", output.items);
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output.clearRetainingCapacity();
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try printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = 3, .column = 0 });
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try expectEqualStrings("3\n", output.items);
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output.clearRetainingCapacity();
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}
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{
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const file = try test_dir.dir.createFile("line_overlaps_page_boundary.zig", .{});
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defer file.close();
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const path = try fs.path.join(allocator, &.{ test_dir_path, "line_overlaps_page_boundary.zig" });
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defer allocator.free(path);
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const overlap = 10;
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var writer = file.writer();
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try writer.writeByteNTimes('a', mem.page_size - overlap);
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try writer.writeByte('\n');
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try writer.writeByteNTimes('a', overlap);
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try printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = 2, .column = 0 });
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try expectEqualStrings(("a" ** overlap) ++ "\n", output.items);
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output.clearRetainingCapacity();
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}
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{
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const file = try test_dir.dir.createFile("file_ends_on_page_boundary.zig", .{});
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defer file.close();
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const path = try fs.path.join(allocator, &.{ test_dir_path, "file_ends_on_page_boundary.zig" });
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defer allocator.free(path);
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var writer = file.writer();
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try writer.writeByteNTimes('a', mem.page_size);
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try printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = 1, .column = 0 });
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try expectEqualStrings(("a" ** mem.page_size) ++ "\n", output.items);
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output.clearRetainingCapacity();
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}
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{
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const file = try test_dir.dir.createFile("very_long_first_line_spanning_multiple_pages.zig", .{});
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defer file.close();
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const path = try fs.path.join(allocator, &.{ test_dir_path, "very_long_first_line_spanning_multiple_pages.zig" });
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defer allocator.free(path);
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var writer = file.writer();
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try writer.writeByteNTimes('a', 3 * mem.page_size);
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try expectError(error.EndOfFile, printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = 2, .column = 0 }));
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try printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = 1, .column = 0 });
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try expectEqualStrings(("a" ** (3 * mem.page_size)) ++ "\n", output.items);
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output.clearRetainingCapacity();
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try writer.writeAll("a\na");
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try printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = 1, .column = 0 });
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try expectEqualStrings(("a" ** (3 * mem.page_size)) ++ "a\n", output.items);
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output.clearRetainingCapacity();
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try printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = 2, .column = 0 });
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try expectEqualStrings("a\n", output.items);
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output.clearRetainingCapacity();
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}
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{
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const file = try test_dir.dir.createFile("file_of_newlines.zig", .{});
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defer file.close();
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const path = try fs.path.join(allocator, &.{ test_dir_path, "file_of_newlines.zig" });
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defer allocator.free(path);
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var writer = file.writer();
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const real_file_start = 3 * mem.page_size;
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try writer.writeByteNTimes('\n', real_file_start);
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try writer.writeAll("abc\ndef");
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try printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = real_file_start + 1, .column = 0 });
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try expectEqualStrings("abc\n", output.items);
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output.clearRetainingCapacity();
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try printLineFromFileAnyOs(output_stream, .{ .file_name = path, .line = real_file_start + 2, .column = 0 });
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try expectEqualStrings("def\n", output.items);
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output.clearRetainingCapacity();
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}
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}
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