To read the structure of a literate programming web from a path in the file system.

§1. Introduction. Webs are literate programs for the Inweb LP system. A single web consists of a number of chapters (though sometimes just one, called "Sections"), each of which consists of a number of sections. A web can represent a stand-alone program, or a library to be used in multiple programs, in which case it is called a "module".

Inweb syntax has gradually shifted over the years, but there are two main versions: the second was cleaned up and simplified from the first in 2019. 

enum V1_SYNTAX from 1
enum V2_SYNTAX

§2. Web MD. No relation to the website of the same name: MD here stands for metadata. Our task in this section will be to read a web from the filing system and produce the following metadata structure.

Each web produces a single instance of web_md: 

typedef struct web_md {
    struct pathname *path_to_web;  relative to the current working directory
    struct filename *single_file;  relative to the current working directory
    struct linked_list *bibliographic_data;  of web_bibliographic_datum
    struct semantic_version_number version_number;  as deduced from bibliographic data
    int default_syntax;  which version syntax the sections will have
    int chaptered;  has the author explicitly divided it into named chapters?
    struct text_stream *main_language_name;  in which most of the sections are written

    struct module *as_module;  the root of a small dependency graph

    struct filename *contents_filename;  or NULL for a single-file web
    struct linked_list *tangle_target_names;  of text_stream
    struct linked_list *header_filenames;  of filename

    struct linked_list *chapters_md;  of chapter_md
    struct linked_list *sections_md;  of section_md
    CLASS_DEFINITION
} web_md;

§3. The chapters_md list in a web_md contains these as its entries: 

typedef struct chapter_md {
    struct text_stream *ch_range;  e.g., P for Preliminaries, 7 for Chapter 7, C for Appendix C
    struct text_stream *ch_title;  e.g., "Chapter 3: Fresh Water Fish"
    struct text_stream *ch_basic_title;  e.g., "Chapter 3"
    struct text_stream *ch_decorated_title;  e.g., "Fresh Water Fish"
    struct text_stream *rubric;  optional; without double-quotation marks

    struct text_stream *ch_language_name;  in which most of the sections are written

    int imported;  from a different web?

    struct linked_list *sections_md;  of section_md
    CLASS_DEFINITION
} chapter_md;

§4. And the sections_md list in a chapter_md contains these as its entries: 

typedef struct section_md {
    struct text_stream *sect_title;  e.g., "Program Control"
    struct text_stream *sect_range;  e.g., "2/ct"
    int using_syntax;  which syntax the web is written in
    int is_a_singleton;  is this the only section in its entire web?

    struct filename *source_file_for_section;

    struct text_stream *tag_name;
    struct text_stream *sect_independent_language;
    struct text_stream *sect_language_name;
    struct text_stream *titling_line_to_insert;

    struct module *owning_module;
    CLASS_DEFINITION
} section_md;

§5. Reading from the file system. Webs can be stored in two ways: as a directory containing a multitude of files, in which case the pathname P is supplied; or as a single file with everything in one (and thus, implicitly, a single chapter and a single section), in which case a filename alt_F is supplied. 

web_md *WebMetadata::get_without_modules(pathname *P, filename *alt_F) {
    return WebMetadata::get(P, alt_F, V2_SYNTAX, NULL, FALSE, FALSE, NULL);
}

web_md *WebMetadata::get(pathname *P, filename *alt_F, int syntax_version,
    module_search *I, int verbosely, int including_modules, pathname *path_to_inweb) {
    if ((including_modules) && (I == NULL)) I = WebModules::make_search_path(NULL);
    web_md *Wm = CREATE(web_md);
    Begin the bibliographic data5.1;
    Initialise the rest of the web MD5.2;
    WebMetadata::read_contents_page(Wm, Wm->as_module, I, verbosely,
        including_modules, NULL, path_to_inweb);
    Consolidate the bibliographic data5.3;
    Work out the section ranges5.4;
    return Wm;
}

§5.1. Begin the bibliographic data5.1 = 

    Wm->bibliographic_data = NEW_LINKED_LIST(web_bibliographic_datum);
    Bibliographic::initialise_data(Wm);

§5.2. Initialise the rest of the web MD5.2 = 

    if (P) {
        Wm->path_to_web = P;
        Wm->single_file = NULL;
        Wm->contents_filename = WebMetadata::contents_filename(P);
    } else {
        Wm->path_to_web = Filenames::up(alt_F);
        Wm->single_file = alt_F;
        Wm->contents_filename = NULL;
    }
    Wm->version_number = VersionNumbers::null();
    Wm->default_syntax = syntax_version;
    Wm->chaptered = FALSE;
    Wm->sections_md = NEW_LINKED_LIST(sections_md);
    Wm->chapters_md = NEW_LINKED_LIST(chapter_md);
    Wm->tangle_target_names = NEW_LINKED_LIST(text_stream);
    Wm->main_language_name = Str::new();
    Wm->header_filenames = NEW_LINKED_LIST(filename);
    Wm->as_module = WebModules::create_main_module(Wm);

§5.3. Consolidate the bibliographic data5.3 = 

    Bibliographic::check_required_data(Wm);
    BuildFiles::set_bibliographic_data_for(Wm);
    BuildFiles::deduce_semver(Wm);

§5.4. If no range is supplied, we make one ourselves.

Work out the section ranges5.4 = 

    int sequential = FALSE;  are we numbering sections sequentially?
    if (Str::eq(Bibliographic::get_datum(Wm, I"Sequential Section Ranges"), I"On"))
        sequential = TRUE;
    chapter_md *Cm;
    section_md *Sm;
    LOOP_OVER_LINKED_LIST(Cm, chapter_md, Wm->chapters_md) {
        int section_counter = 1;
        LOOP_OVER_LINKED_LIST(Sm, section_md, Cm->sections_md) {
            if (Str::len(Sm->sect_range) == 0)
                Concoct a range for section Sm in chapter Cm in web Wm5.4.1;
            section_counter++;
        }
    }

§5.4.1. Concoct a range for section Sm in chapter Cm in web Wm5.4.1 = 

    if (sequential) {
        WRITE_TO(Sm->sect_range, "%S/", Cm->ch_range);
        WRITE_TO(Sm->sect_range, "s%d", section_counter);
    } else {
        text_stream *from = Sm->sect_title;
        int letters_from_each_word = 5;
        do {
            Str::clear(Sm->sect_range);
            WRITE_TO(Sm->sect_range, "%S/", Cm->ch_range);
            Make the tail using this many consonants from each word5.4.1.1;
            if (--letters_from_each_word == 0) break;
        } while (Str::len(Sm->sect_range) > 5);

        Terminate with disambiguating numbers in case of collisions5.4.1.2;
    }

§5.4.1.1. We collapse words to an initial letter plus consonants: thus "electricity" would be "elctrcty", since we don't count "y" as a vowel here.

Make the tail using this many consonants from each word5.4.1.1 = 

    int sn = 0, sw = Str::len(Sm->sect_range);
    if (Platform::is_folder_separator(Str::get_at(from, sn))) sn++;
    int letters_from_current_word = 0;
    while ((Str::get_at(from, sn)) && (Str::get_at(from, sn) != '.')) {
        if (Str::get_at(from, sn) == ' ') letters_from_current_word = 0;
        else {
            if (letters_from_current_word < letters_from_each_word) {
                if (Str::get_at(from, sn) != '-') {
                    inchar32_t l = Characters::tolower(Str::get_at(from, sn));
                    if ((letters_from_current_word == 0) ||
                        ((l != 'a') && (l != 'e') && (l != 'i') &&
                            (l != 'o') && (l != 'u'))) {
                        Str::put_at(Sm->sect_range, sw++, l);
                        Str::put_at(Sm->sect_range, sw, 0);
                        letters_from_current_word++;
                    }
                }
            }
        }
        sn++;
    }

§5.4.1.2. We never want two sections to have the same range.

Terminate with disambiguating numbers in case of collisions5.4.1.2 = 

    TEMPORARY_TEXT(original_range)
    Str::copy(original_range, Sm->sect_range);
    int disnum = 0, collision = FALSE;
    do {
        if (disnum++ > 0) {
            int ldn = 4;
            if (disnum >= 1000) ldn = 3;
            else if (disnum >= 100) ldn = 2;
            else if (disnum >= 10) ldn = 1;
            else ldn = 0;
            Str::clear(Sm->sect_range);
            WRITE_TO(Sm->sect_range, "%S", original_range);
            Str::truncate(Sm->sect_range, Str::len(Sm->sect_range) - ldn);
            WRITE_TO(Sm->sect_range, "%d", disnum);
        }
        collision = FALSE;
        chapter_md *Cm2;
        section_md *Sm2;
        LOOP_OVER_LINKED_LIST(Cm2, chapter_md, Wm->chapters_md)
            LOOP_OVER_LINKED_LIST(Sm2, section_md, Cm2->sections_md)
                if ((Sm2 != Sm) && (Str::eq(Sm2->sect_range, Sm->sect_range))) {
                    collision = TRUE; break;
                }
    } while (collision);
    DISCARD_TEXT(original_range)

§6. Reading the contents page. Making the web begins by reading the contents section, which really isn't a section at all (and perhaps we shouldn't pretend that it is by the use of the .w file extension, but we probably want it to have the same file extension, and its syntax is chosen so that syntax-colouring for regular sections doesn't make it look odd). When the word "section" is used in the Inweb code, it almost always means "section other than the contents".

Because a contents page can, by importing a module, cause a further contents page to be read, we set this up as a recursion.

We then run through an individual contents page line by line, using the following slate of variables to keep track of where we are.

With a single-file web, the "contents section" doesn't exist as a file in its own right: instead, it's the top few lines of the single file. We handle that by halting at the junction point. 

typedef struct reader_state {
    struct web_md *Wm;
    struct filename *contents_filename;
    int in_biblio;
    int in_purpose;  Reading the bit just after the new chapter?
    struct chapter_md *chapter_being_scanned;
    struct text_stream *chapter_dir_name;  Where sections in the current chapter live
    struct text_stream *titling_line_to_insert;  To be inserted automagically
    struct pathname *path_to;  Where web material is being read from
    struct module *reading_from;
    struct module_search *import_from;  Where imported webs are
    struct pathname *path_to_inweb;
    int scan_verbosely;
    int including_modules;
    int main_web_not_module;  Reading the original web, or an included one?
    int halt_at_at;  Used for reading contents pages of single-file webs
    int halted;  Set when such a halt has occurred
    int section_count;
    struct section_md *last_section;
} reader_state;

void WebMetadata::read_contents_page(web_md *Wm, module *of_module,
    module_search *import_path, int verbosely,
    int including_modules, pathname *path, pathname *X) {
    reader_state RS;
    Initialise the reader state6.1;

    int cl = TextFiles::read(RS.contents_filename, FALSE, "can't open contents file",
        TRUE, WebMetadata::read_contents_line, NULL, &RS);
    if (verbosely) {
        if (Wm->single_file) {
            PRINT("Read %d lines of contents part at top of file\n", cl);
        } else {
            PRINT("Read contents section (%d lines)\n", cl);
        }
    }
    if (RS.section_count == 1) RS.last_section->is_a_singleton = TRUE;
}

§6.1. Initialise the reader state6.1 = 

    RS.Wm = Wm;
    RS.reading_from = of_module;
    RS.in_biblio = TRUE;
    RS.in_purpose = FALSE;
    RS.chapter_being_scanned = NULL;
    RS.chapter_dir_name = Str::new();
    RS.titling_line_to_insert = Str::new();
    RS.scan_verbosely = verbosely;
    RS.including_modules = including_modules;
    RS.path_to = path;
    RS.import_from = import_path;
    RS.halted = FALSE;
    RS.path_to_inweb = X;

    if (path == NULL) {
        path = Wm->path_to_web;
        RS.main_web_not_module = TRUE;
    } else {
        RS.main_web_not_module = FALSE;
    }

    if (Wm->single_file) {
        RS.contents_filename = Wm->single_file;
        RS.halt_at_at = TRUE;
    } else {
        RS.contents_filename = WebMetadata::contents_filename(path);
        RS.halt_at_at = FALSE;
    }
    RS.section_count = 0;
    RS.last_section = NULL;

§7. The contents section has a syntax quite different from all other sections, and sets out bibliographic information about the web, the sections and their organisation, and so on. 

void WebMetadata::read_contents_line(text_stream *line, text_file_position *tfp, void *X) {
    reader_state *RS = (reader_state *) X;
    if (RS->halted) return;

    int begins_with_white_space = FALSE;
    if (Characters::is_whitespace(Str::get_first_char(line)))
        begins_with_white_space = TRUE;
    Str::trim_white_space(line);

    Act immediately if the web syntax version is changed7.1;
    int syntax = RS->Wm->default_syntax;

    filename *filename_of_single_file_web = NULL;
    if ((RS->halt_at_at) && (Str::get_at(line, 0) == '@'))
        Halt at this point in the single file, and make the rest of it a one-chapter section7.2;

    Read regular contents material7.3;
}

§7.1. Since the web syntax version affects how the rest of the file is read, it's no good simply to store this up for later: we have to change the web structure immediately.

Act immediately if the web syntax version is changed7.1 = 

    if (Str::eq(line, I"Web Syntax Version: 1"))
        RS->Wm->default_syntax = V1_SYNTAX;
    else if (Str::eq(line, I"Web Syntax Version: 2"))
        RS->Wm->default_syntax = V2_SYNTAX;

§7.2. Suppose we're reading a single-file web, and we hit the first @ marker. The contents part has now ended, so we should halt scanning. But we also need to give the web a single chapter ("Sections", range "S"), which contains a single section ("All") consisting of the remainder of the single file.

Halt at this point in the single file, and make the rest of it a one-chapter section7.2 = 

    RS->halted = TRUE;
    text_stream *new_chapter_range = I"S";
    text_stream *language_name = NULL;
    line = I"Sections";
    Create the new chapter with these details7.2.1;
    line = I"All";
    filename_of_single_file_web = tfp->text_file_filename;
    Read about, and read in, a new section7.2.2;
    return;

§7.3. With those two complications out of the way, we now know that we're reading a line of contents material. At the start of the contents, this will be a series of bibliographic data values; then there's a blank line, and then we're into the section listing.

Read regular contents material7.3 = 

    if (Str::len(line) == 0) End bibliographic data here, at the blank line7.3.1
    else if (RS->in_biblio) Read the bibliographic data block at the top7.3.2
    else Read the roster of sections at the bottom7.3.3;

§7.3.1. At this point we've gone through the bibliographic lines at the top of the contents page, and are soon going to read in the sections.

End bibliographic data here, at the blank line7.3.1 = 

    RS->in_biblio = FALSE;

§7.3.2. The bibliographic data gives lines in any order specifying values of variables with fixed names; a blank line ends the block.

Read the bibliographic data block at the top7.3.2 = 

    if (RS->main_web_not_module) {
        match_results mr = Regexp::create_mr();
        if (Regexp::match(&mr, line, U"(%c+?): (%c+?) *")) {
            TEMPORARY_TEXT(key)
            Str::copy(key, mr.exp[0]);
            TEMPORARY_TEXT(value)
            Str::copy(value, mr.exp[1]);
            Set bibliographic key-value pair7.3.2.1;
            DISCARD_TEXT(key)
            DISCARD_TEXT(value)
        } else {
            TEMPORARY_TEXT(err)
            WRITE_TO(err, "expected 'Setting: Value' but found '%S'", line);
            Errors::in_text_file_S(err, tfp);
            DISCARD_TEXT(err)
        }
        Regexp::dispose_of(&mr);
    }

§7.3.2.1. Set bibliographic key-value pair7.3.2.1 = 

    if (Bibliographic::datum_can_be_declared(RS->Wm, key)) {
        if (Bibliographic::datum_on_or_off(RS->Wm, key)) {
            if ((Str::ne_wide_string(value, U"On")) && (Str::ne_wide_string(value, U"Off"))) {
                TEMPORARY_TEXT(err)
                WRITE_TO(err, "this setting must be 'On' or 'Off': %S", key);
                Errors::in_text_file_S(err, tfp);
                DISCARD_TEXT(err)
                Str::clear(value);
                WRITE_TO(value, "Off");
            }
        }
        Bibliographic::set_datum(RS->Wm, key, value);
    } else {
        TEMPORARY_TEXT(err)
        WRITE_TO(err, "no such bibliographic datum: %S", key);
        Errors::in_text_file_S(err, tfp);
        DISCARD_TEXT(err)
    }

§7.3.3. In the bulk of the contents, we find indented lines for sections and unindented ones for chapters.

Read the roster of sections at the bottom7.3.3 = 

    if (begins_with_white_space == FALSE) {
        if (Str::get_first_char(line) == '"') {
            RS->in_purpose = TRUE; Str::delete_first_character(line);
        }
        if (RS->in_purpose == TRUE) Record the purpose of the current chapter7.3.3.1
        else Read about a new chapter7.3.3.2;
    } else Read about, and read in, a new section7.2.2;

§7.3.3.1. After a declared chapter heading, subsequent lines form its purpose, until we reach a closed quote: we then stop, but remove the quotation marks. Because we like a spoonful of syntactic sugar on our porridge, that's why.

Record the purpose of the current chapter7.3.3.1 = 

    if ((Str::len(line) > 0) && (Str::get_last_char(line) == '"')) {
        Str::truncate(line, Str::len(line)-1); RS->in_purpose = FALSE;
    }
    if (RS->chapter_being_scanned) {
        text_stream *r = RS->chapter_being_scanned->rubric;
        if (Str::len(r) > 0) WRITE_TO(r, " ");
        WRITE_TO(r, "%S", line);
    }

§7.3.3.2. The title tells us everything we need to know about a chapter:

Read about a new chapter7.3.3.2 = 

    TEMPORARY_TEXT(new_chapter_range)  e.g., S, P, 1, 2, 3, A, B, ...
    TEMPORARY_TEXT(pdf_leafname)
    text_stream *language_name = NULL;

    match_results mr = Regexp::create_mr();
    if (Regexp::match(&mr, line, U"(%c*%C) %(Independent(%c*)%)")) {
        text_stream *title_alone = mr.exp[0];
        language_name = mr.exp[1];
        Mark this chapter as an independent tangle target7.3.3.2.1;
        Str::copy(line, title_alone);
    }
    int this_is_a_chapter = TRUE;
    Str::clear(RS->chapter_dir_name);
    if (Str::eq_wide_string(line, U"Sections")) {
        WRITE_TO(new_chapter_range, "S");
        WRITE_TO(RS->chapter_dir_name, "Sections");
        WRITE_TO(pdf_leafname, "Sections.pdf");
        RS->Wm->chaptered = FALSE;
        Str::clear(RS->titling_line_to_insert);
    } else if (Str::eq_wide_string(line, U"Preliminaries")) {
        WRITE_TO(new_chapter_range, "P");
        WRITE_TO(RS->chapter_dir_name, "Preliminaries");
        Str::clear(RS->titling_line_to_insert);
        WRITE_TO(RS->titling_line_to_insert, "%S.", line);
        WRITE_TO(pdf_leafname, "Preliminaries.pdf");
        RS->Wm->chaptered = TRUE;
    } else if (Str::eq_wide_string(line, U"Manual")) {
        WRITE_TO(new_chapter_range, "M");
        WRITE_TO(RS->chapter_dir_name, "Manual");
        Str::clear(RS->titling_line_to_insert);
        WRITE_TO(RS->titling_line_to_insert, "%S.", line);
        WRITE_TO(pdf_leafname, "Manual.pdf");
        RS->Wm->chaptered = TRUE;
    } else if (Regexp::match(&mr, line, U"Header: (%c+)")) {
        pathname *P = RS->path_to;
        if (P == NULL) P = RS->Wm->path_to_web;
        P = Pathnames::down(P, I"Headers");
        filename *HF = Filenames::in(P, mr.exp[0]);
        ADD_TO_LINKED_LIST(HF, filename, RS->Wm->header_filenames);
        this_is_a_chapter = FALSE;
    } else if (Regexp::match(&mr, line, U"Import: (%c+)")) {
        if (RS->halt_at_at)
            Errors::in_text_file_S(I"single-file webs cannot Import modules", tfp);
        else if (RS->import_from) {
            module *imported =
                WebModules::find(RS->Wm, RS->import_from, mr.exp[0], RS->path_to_inweb);
            if (imported == NULL) {
                TEMPORARY_TEXT(err)
                WRITE_TO(err, "unable to find module: %S", line);
                Errors::in_text_file_S(err, tfp);
                DISCARD_TEXT(err)
            } else {
                if (RS->including_modules) {
                    int save_syntax = RS->Wm->default_syntax;
                    WebMetadata::read_contents_page(RS->Wm, imported, RS->import_from,
                        RS->scan_verbosely, RS->including_modules,
                        imported->module_location, RS->path_to_inweb);
                    RS->Wm->default_syntax = save_syntax;
                }
            }
        }
        this_is_a_chapter = FALSE;
    } else if (Regexp::match(&mr, line, U"Chapter (%d+): %c+")) {
        int n = Str::atoi(mr.exp[0], 0);
        WRITE_TO(new_chapter_range, "%d", n);
        WRITE_TO(RS->chapter_dir_name, "Chapter %d", n);
        Str::clear(RS->titling_line_to_insert);
        WRITE_TO(RS->titling_line_to_insert, "%S.", line);
        WRITE_TO(pdf_leafname, "Chapter-%d.pdf", n);
        RS->Wm->chaptered = TRUE;
    } else if (Regexp::match(&mr, line, U"Appendix (%c): %c+")) {
        text_stream *letter = mr.exp[0];
        Str::copy(new_chapter_range, letter);
        WRITE_TO(RS->chapter_dir_name, "Appendix %S", letter);
        Str::clear(RS->titling_line_to_insert);
        WRITE_TO(RS->titling_line_to_insert, "%S.", line);
        WRITE_TO(pdf_leafname, "Appendix-%S.pdf", letter);
        RS->Wm->chaptered = TRUE;
    } else {
        TEMPORARY_TEXT(err)
        WRITE_TO(err, "segment not understood: %S", line);
        Errors::in_text_file_S(err, tfp);
        WRITE_TO(STDERR, "(Must be 'Chapter <number>: Title', "
            "'Appendix <letter A to O>: Title',\n");
        WRITE_TO(STDERR, "'Manual', 'Preliminaries' or 'Sections')\n");
        DISCARD_TEXT(err)
    }

    if (this_is_a_chapter) Create the new chapter with these details7.2.1;
    DISCARD_TEXT(new_chapter_range)
    DISCARD_TEXT(pdf_leafname)
    Regexp::dispose_of(&mr);

§7.3.3.2.1. A chapter whose title marks it as Independent becomes a new tangle target, with the same language as the main web unless stated otherwise.

Mark this chapter as an independent tangle target7.3.3.2.1 = 

    match_results mr = Regexp::create_mr();
    if (Regexp::match(&mr, language_name, U" *"))
        language_name = Bibliographic::get_datum(RS->Wm, I"Language");
    else if (Regexp::match(&mr, language_name, U" *(%c*?) *"))
        language_name = mr.exp[0];
    Regexp::dispose_of(&mr);

§7.2.1. Create the new chapter with these details7.2.1 = 

    chapter_md *Cm = CREATE(chapter_md);
    Cm->ch_range = Str::duplicate(new_chapter_range);
    if (line == NULL) PRINT("Nullity!\n");
    Cm->ch_title = Str::duplicate(line);
    match_results mr = Regexp::create_mr();
    if (Regexp::match(&mr, Cm->ch_title, U"(%c*?): *(%c*)")) {
        Cm->ch_basic_title = Str::duplicate(mr.exp[0]);
        Cm->ch_decorated_title = Str::duplicate(mr.exp[1]);
    } else {
        Cm->ch_basic_title = Str::duplicate(Cm->ch_title);
        Cm->ch_decorated_title = Str::new();
    }
    Regexp::dispose_of(&mr);
    Cm->rubric = Str::new();
    Cm->ch_language_name = language_name;
    Cm->imported = TRUE;
    Cm->sections_md = NEW_LINKED_LIST(section_md);
    if (RS->main_web_not_module) Cm->imported = FALSE;

    ADD_TO_LINKED_LIST(Cm, chapter_md, RS->Wm->chapters_md);
    ADD_TO_LINKED_LIST(Cm, chapter_md, RS->reading_from->chapters_md);
    RS->chapter_being_scanned = Cm;

§7.2.2. That's enough on creating chapters. This is the more interesting business of registering a new section within a chapter — more interesting because we also read in and process its file.

Read about, and read in, a new section7.2.2 = 

    section_md *Sm = CREATE(section_md);
    Initialise the section structure7.2.2.1;
    Add the section to the web and the current chapter7.2.2.2;
    Work out the language and tangle target for the section7.2.2.3;

    if (Sm->source_file_for_section == NULL)
        Work out the filename of this section file7.2.2.4;

§7.2.2.1. Initialise the section structure7.2.2.1 = 

    Sm->source_file_for_section = filename_of_single_file_web;
    Sm->using_syntax = syntax;
    Sm->is_a_singleton = FALSE;
    Sm->titling_line_to_insert = Str::duplicate(RS->titling_line_to_insert);
    Sm->sect_range = Str::new();
    Str::clear(RS->titling_line_to_insert);

    match_results mr = Regexp::create_mr();
    if (Regexp::match(&mr, line, U"(%c+) %^\"(%c+)\" *")) {
        Sm->sect_title = Str::duplicate(mr.exp[0]);
        Sm->tag_name = Str::duplicate(mr.exp[1]);
    } else {
        Sm->sect_title = Str::duplicate(line);
        Sm->tag_name = NULL;
    }
    Regexp::dispose_of(&mr);
    Sm->owning_module = RS->reading_from;

§7.2.2.2. Add the section to the web and the current chapter7.2.2.2 = 

    chapter_md *Cm = RS->chapter_being_scanned;
    RS->section_count++;
    RS->last_section = Sm;
    ADD_TO_LINKED_LIST(Sm, section_md, Cm->sections_md);
    ADD_TO_LINKED_LIST(Sm, section_md, RS->Wm->sections_md);
    ADD_TO_LINKED_LIST(Sm, section_md, RS->reading_from->sections_md);

§7.2.2.3. Work out the language and tangle target for the section7.2.2.3 = 

    Sm->sect_language_name = RS->chapter_being_scanned->ch_language_name;  by default
    match_results mr = Regexp::create_mr();
    if (Regexp::match(&mr, line, U"(%c*%C) %(Independent (%c*) *%)")) {
        text_stream *title_alone = mr.exp[0];
        text_stream *language_name = mr.exp[1];
        Mark this section as an independent tangle target7.2.2.3.1;
        Str::copy(Sm->sect_title, title_alone);
    }
    Regexp::dispose_of(&mr);

§7.2.2.3.1. Mark this section as an independent tangle target7.2.2.3.1 = 

    text_stream *p = language_name;
    if (Str::len(p) == 0) p = Bibliographic::get_datum(RS->Wm, I"Language");
    Sm->sect_independent_language = Str::duplicate(p);

§7.2.2.4. If we're told that a section is called "Bells and Whistles", what filename is it stored in? Firstly, the leafname is normally Bells and Whistles.w, but the extension used doesn't have to be .w: for Inform 6 template files, the extension needs to be .i6t. We allow either.

Work out the filename of this section file7.2.2.4 = 

    TEMPORARY_TEXT(leafname_to_use)
    WRITE_TO(leafname_to_use, "%S.i6t", Sm->sect_title);
    pathname *P = RS->path_to;
    if (P == NULL) P = RS->Wm->path_to_web;
    if (Str::len(RS->chapter_dir_name) > 0)
        P = Pathnames::down(P, RS->chapter_dir_name);
    Sm->source_file_for_section = Filenames::in(P, leafname_to_use);
    if (TextFiles::exists(Sm->source_file_for_section) == FALSE) {
        Str::clear(leafname_to_use);
        WRITE_TO(leafname_to_use, "%S.w", Sm->sect_title);
        Sm->source_file_for_section = Filenames::in(P, leafname_to_use);
    }
    DISCARD_TEXT(leafname_to_use)

§8. Relative pathnames or filenames. 

int WebMetadata::directory_looks_like_a_web(pathname *P) {
    return TextFiles::exists(WebMetadata::contents_filename(P));
}

filename *WebMetadata::contents_filename(pathname *P) {
    return Filenames::in(P, I"Contents.w");
}

§9. Statistics. 

int WebMetadata::chapter_count(web_md *Wm) {
    int n = 0;
    chapter_md *Cm;
    LOOP_OVER_LINKED_LIST(Cm, chapter_md, Wm->chapters_md) n++;
    return n;
}
int WebMetadata::section_count(web_md *Wm) {
    int n = 0;
    chapter_md *Cm;
    LOOP_OVER_LINKED_LIST(Cm, chapter_md, Wm->chapters_md) {
        section_md *Sm;
        LOOP_OVER_LINKED_LIST(Sm, section_md, Cm->sections_md) n++;
    }
    return n;
}