Enforce that \q may not be used anywhere within \c. It shouldn't be

[sgt/halibut] / input.c

/*
 * input.c: read the source form
 */

#include <stdio.h>
#include <assert.h>
#include <time.h>
#include "halibut.h"

#define TAB_STOP 8                     /* for column number tracking */

static void setpos(input *in, char *fname) {
    in->pos.filename = fname;
    in->pos.line = 1;
    in->pos.col = (in->reportcols ? 1 : -1);
}

static void unget(input *in, int c, filepos *pos) {
    if (in->npushback >= in->pushbacksize) {
        in->pushbacksize = in->npushback + 16;
        in->pushback = sresize(in->pushback, in->pushbacksize, pushback);
    }
    in->pushback[in->npushback].chr = c;
    in->pushback[in->npushback].pos = *pos;   /* structure copy */
    in->npushback++;
}

/* ---------------------------------------------------------------------- */
/*
 * Macro subsystem
 */
typedef struct macro_Tag macro;
struct macro_Tag {
    wchar_t *name, *text;
};
struct macrostack_Tag {
    macrostack *next;
    wchar_t *text;
    int ptr, npushback;
    filepos pos;
};
static int macrocmp(void *av, void *bv) {
    macro *a = (macro *)av, *b = (macro *)bv;
    return ustrcmp(a->name, b->name);
}
static void macrodef(tree234 *macros, wchar_t *name, wchar_t *text,
                     filepos fpos) {
    macro *m = snew(macro);
    m->name = name;
    m->text = text;
    if (add234(macros, m) != m) {
        error(err_macroexists, &fpos, name);
        sfree(name);
        sfree(text);
    }
}
static int macrolookup(tree234 *macros, input *in, wchar_t *name,
                       filepos *pos) {
    macro m, *gotit;
    m.name = name;
    gotit = find234(macros, &m, NULL);
    if (gotit) {
        macrostack *expansion = snew(macrostack);
        expansion->next = in->stack;
        expansion->text = gotit->text;
        expansion->pos = *pos;         /* structure copy */
        expansion->ptr = 0;
        expansion->npushback = in->npushback;
        in->stack = expansion;
        return TRUE;
    } else
        return FALSE;
}
static void macrocleanup(tree234 *macros) {
    int ti;
    macro *m;
    for (ti = 0; (m = (macro *)index234(macros, ti)) != NULL; ti++) {
        sfree(m->name);
        sfree(m->text);
        sfree(m);
    }
    freetree234(macros);
}

static void input_configure(input *in, paragraph *cfg) {
    assert(cfg->type == para_Config);

    if (!ustricmp(cfg->keyword, L"input-charset")) {
        char *csname = utoa_dup(uadv(cfg->keyword), CS_ASCII);
        in->charset = charset_from_localenc(csname);
        sfree(csname);
    }
}

/*
 * Can return EOF
 */
static int get(input *in, filepos *pos, rdstringc *rsc) {
    int pushbackpt = in->stack ? in->stack->npushback : 0;
    if (in->npushback > pushbackpt) {
        --in->npushback;
        if (pos)
            *pos = in->pushback[in->npushback].pos;   /* structure copy */
        return in->pushback[in->npushback].chr;
    }
    else if (in->stack) {
        wchar_t c = in->stack->text[in->stack->ptr];
        if (in->stack->text[++in->stack->ptr] == L'\0') {
            macrostack *tmp = in->stack;
            in->stack = tmp->next;
            sfree(tmp);
        }
        return c;
    }
    else if (in->currfp) {

        while (in->wcpos >= in->nwc) {

            int c = getc(in->currfp);

            if (c == EOF) {
                fclose(in->currfp);
                in->currfp = NULL;
                return EOF;
            }

            if (rsc)
                rdaddc(rsc, c);

            /* Track line numbers, for error reporting */
            if (pos)
                *pos = in->pos;
            if (in->reportcols) {
                switch (c) {
                  case '\t':
                    in->pos.col = 1 + (in->pos.col + TAB_STOP-1) % TAB_STOP;
                    break;
                  case '\n':
                    in->pos.col = 1;
                    in->pos.line++;
                    break;
                  default:
                    in->pos.col++;
                    break;
                }
            } else {
                in->pos.col = -1;
                if (c == '\n')
                    in->pos.line++;
            }

            /*
             * Do input character set translation, so that we return
             * Unicode.
             */
            {
                char buf[1];
                char const *p;
                int inlen;

                buf[0] = (char)c;
                p = buf;
                inlen = 1;

                in->nwc = charset_to_unicode(&p, &inlen,
                                             in->wc, lenof(in->wc),
                                             in->charset, &in->csstate,
                                             NULL, 0);
                assert(p == buf+1 && inlen == 0);

                in->wcpos = 0;
            }
        }

        return in->wc[in->wcpos++];

    } else
        return EOF;
}

/*
 * Lexical analysis of source files.
 */
typedef struct token_Tag token;
struct token_Tag {
    int type;
    int cmd, aux;
    wchar_t *text;
    char *origtext;
    filepos pos;
};
enum {
    tok_eof,                           /* end of file */
    tok_eop,                           /* end of paragraph */
    tok_white,                         /* whitespace */
    tok_word,                          /* a word or word fragment */
    tok_cmd,                           /* \command */
    tok_lbrace,                        /* { */
    tok_rbrace                         /* } */
};

/* Halibut command keywords. */
enum {
    c__invalid,                        /* invalid command */
    c__comment,                        /* comment command (\#) */
    c__escaped,                        /* escaped character */
    c__nop,                            /* no-op */
    c__nbsp,                           /* nonbreaking space */
    c_A,                               /* appendix heading */
    c_B,                               /* bibliography entry */
    c_BR,                              /* bibliography rewrite */
    c_C,                               /* chapter heading */
    c_H,                               /* heading */
    c_I,                               /* invisible index mark */
    c_IM,                              /* index merge/rewrite */
    c_K,                               /* capitalised cross-reference */
    c_S,                               /* aux field is 0, 1, 2, ... */
    c_U,                               /* unnumbered-chapter heading */
    c_W,                               /* Web hyperlink */
    c_b,                               /* bulletted list */
    c_c,                               /* code */
    c_cfg,                             /* configuration directive */
    c_copyright,                       /* copyright statement */
    c_cw,                              /* weak code */
    c_date,                            /* document processing date */
    c_dd,                              /* description list: description */
    c_define,                          /* macro definition */
    c_dt,                              /* description list: described thing */
    c_e,                               /* emphasis */
    c_i,                               /* visible index mark */
    c_ii,                              /* uncapitalised visible index mark */
    c_k,                               /* uncapitalised cross-reference */
    c_lcont,                           /* continuation para(s) for list item */
    c_n,                               /* numbered list */
    c_nocite,                          /* bibliography trickery */
    c_preamble,                        /* (obsolete) preamble text */
    c_q,                               /* quote marks */
    c_quote,                           /* block-quoted paragraphs */
    c_rule,                            /* horizontal rule */
    c_title,                           /* document title */
    c_u,                               /* aux field is char code */
    c_versionid                        /* document RCS id */
};

/* Perhaps whitespace should be defined in a more Unicode-friendly way? */
#define iswhite(c) ( (c)==32 || (c)==9 || (c)==13 || (c)==10 )
#define isnl(c) ( (c)==10 )
#define isdec(c) ( ((c)>='0'&&(c)<='9') )
#define fromdec(c) ( (c)-'0' )
#define ishex(c) ( ((c)>='0'&&(c)<='9') || ((c)>='A'&&(c)<='F') || ((c)>='a'&&(c)<='f'))
#define fromhex(c) ( (c)<='9' ? (c)-'0' : ((c)&0xDF) - ('A'-10) )
#define iscmd(c) ( ((c)>='0'&&(c)<='9') || ((c)>='A'&&(c)<='Z') || ((c)>='a'&&(c)<='z'))

/*
 * Keyword comparison function. Like strcmp, but between a wchar_t *
 * and a char *.
 */
static int kwcmp(wchar_t const *p, char const *q) {
    int i;
    do {
        i = *p - *q;
    } while (*p++ && *q++ && !i);
    return i;
}

/*
 * Match a keyword.
 */
static void match_kw(token *tok) {
    /*
     * FIXME. The ids are explicit in here so as to allow long-name
     * equivalents to the various very short keywords.
     */
    static const struct { char const *name; int id; } keywords[] = {
        {"#", c__comment},             /* comment command (\#) */
        {"-", c__escaped},             /* nonbreaking hyphen */
        {".", c__nop},                 /* no-op */
        {"A", c_A},                    /* appendix heading */
        {"B", c_B},                    /* bibliography entry */
        {"BR", c_BR},                  /* bibliography rewrite */
        {"C", c_C},                    /* chapter heading */
        {"H", c_H},                    /* heading */
        {"I", c_I},                    /* invisible index mark */
        {"IM", c_IM},                  /* index merge/rewrite */
        {"K", c_K},                    /* capitalised cross-reference */
        {"U", c_U},                    /* unnumbered-chapter heading */
        {"W", c_W},                    /* Web hyperlink */
        {"\\", c__escaped},            /* escaped backslash (\\) */
        {"_", c__nbsp},                /* nonbreaking space (\_) */
        {"b", c_b},                    /* bulletted list */
        {"c", c_c},                    /* code */
        {"cfg", c_cfg},                /* configuration directive */
        {"copyright", c_copyright},    /* copyright statement */
        {"cw", c_cw},                  /* weak code */
        {"date", c_date},              /* document processing date */
        {"dd", c_dd},                  /* description list: description */
        {"define", c_define},          /* macro definition */
        {"dt", c_dt},                  /* description list: described thing */
        {"e", c_e},                    /* emphasis */
        {"i", c_i},                    /* visible index mark */
        {"ii", c_ii},                  /* uncapitalised visible index mark */
        {"k", c_k},                    /* uncapitalised cross-reference */
        {"lcont", c_lcont},            /* continuation para(s) for list item */
        {"n", c_n},                    /* numbered list */
        {"nocite", c_nocite},          /* bibliography trickery */
        {"preamble", c_preamble},      /* (obsolete) preamble text */
        {"q", c_q},                    /* quote marks */
        {"quote", c_quote},            /* block-quoted paragraphs */
        {"rule", c_rule},              /* horizontal rule */
        {"title", c_title},            /* document title */
        {"versionid", c_versionid},    /* document RCS id */
        {"{", c__escaped},             /* escaped lbrace (\{) */
        {"}", c__escaped},             /* escaped rbrace (\}) */
    };
    int i, j, k, c;

    /*
     * Special cases: \S{0,1,2,...} and \uABCD. If the syntax
     * doesn't match correctly, we just fall through to the
     * binary-search phase.
     */
    if (tok->text[0] == 'S') {
        /* We expect numeric characters thereafter. */
        wchar_t *p = tok->text+1;
        int n;
        if (!*p)
            n = 1;
        else {
            n = 0;
            while (*p && isdec(*p)) {
                n = 10 * n + fromdec(*p);
                p++;
            }
        }
        if (!*p) {
            tok->cmd = c_S;
            tok->aux = n;
            return;
        }
    } else if (tok->text[0] == 'u') {
        /* We expect hex characters thereafter. */
        wchar_t *p = tok->text+1;
        int n = 0;
        while (*p && ishex(*p)) {
            n = 16 * n + fromhex(*p);
            p++;
        }
        if (!*p) {
            tok->cmd = c_u;
            tok->aux = n;
            return;
        }
    }

    i = -1;
    j = sizeof(keywords)/sizeof(*keywords);
    while (j-i > 1) {
        k = (i+j)/2;
        c = kwcmp(tok->text, keywords[k].name);
        if (c < 0)
            j = k;
        else if (c > 0)
            i = k;
        else /* c == 0 */ {
            tok->cmd = keywords[k].id;
            return;
        }
    }

    tok->cmd = c__invalid;
}


/*
 * Read a token from the input file, in the normal way (`normal' in
 * the sense that code paragraphs work a different way).
 */
token get_token(input *in) {
    int c;
    int nls;
    int prevpos;
    token ret;
    rdstring rs = { 0, 0, NULL };
    rdstringc rsc = { 0, 0, NULL };
    filepos cpos;

    ret.text = NULL;                   /* default */
    ret.origtext = NULL;               /* default */
    if (in->pushback_chars) {
        rdaddsc(&rsc, in->pushback_chars);
        sfree(in->pushback_chars);
        in->pushback_chars = NULL;
    }
    c = get(in, &cpos, &rsc);
    ret.pos = cpos;
    if (iswhite(c)) {                  /* tok_white or tok_eop */
        nls = 0;
        prevpos = 0;
        do {
            if (isnl(c))
                nls++;
            prevpos = rsc.pos;
        } while ((c = get(in, &cpos, &rsc)) != EOF && iswhite(c));
        if (c == EOF) {
            ret.type = tok_eof;
            sfree(rsc.text);
            return ret;
        }
        if (rsc.text) {
            in->pushback_chars = dupstr(rsc.text + prevpos);
            sfree(rsc.text);
        }
        unget(in, c, &cpos);
        ret.type = (nls > 1 ? tok_eop : tok_white);
        return ret;
    } else if (c == EOF) {             /* tok_eof */
        ret.type = tok_eof;
        sfree(rsc.text);
        return ret;
    } else if (c == '\\') {            /* tok_cmd */
        rsc.pos = prevpos = 0;
        c = get(in, &cpos, &rsc);
        if (c == '-' || c == '\\' || c == '_' ||
            c == '#' || c == '{' || c == '}' || c == '.') {
            /* single-char command */
            rdadd(&rs, c);
        } else if (c == 'u') {
            int len = 0;
            do {
                rdadd(&rs, c);
                len++;
                prevpos = rsc.pos;
                c = get(in, &cpos, &rsc);
            } while (ishex(c) && len < 5);
            unget(in, c, &cpos);
        } else if (iscmd(c)) {
            do {
                rdadd(&rs, c);
                prevpos = rsc.pos;
                c = get(in, &cpos, &rsc);
            } while (iscmd(c));
            unget(in, c, &cpos);
        }
        /*
         * Now match the command against the list of available
         * ones.
         */
        ret.type = tok_cmd;
        ret.text = ustrdup(rs.text);
        if (rsc.text) {
            in->pushback_chars = dupstr(rsc.text + prevpos);
            rsc.text[prevpos] = '\0';
            ret.origtext = dupstr(rsc.text);
        } else {
            ret.origtext = dupstr("");
        }
        match_kw(&ret);
        sfree(rs.text);
        sfree(rsc.text);
        return ret;
    } else if (c == '{') {             /* tok_lbrace */
        ret.type = tok_lbrace;
        sfree(rsc.text);
        return ret;
    } else if (c == '}') {             /* tok_rbrace */
        ret.type = tok_rbrace;
        sfree(rsc.text);
        return ret;
    } else {                           /* tok_word */
        /*
         * Read a word: the longest possible contiguous sequence of
         * things other than whitespace, backslash, braces and
         * hyphen. A hyphen terminates the word but is returned as
         * part of it; everything else is pushed back for the next
         * token. The `aux' field contains TRUE if the word ends in
         * a hyphen.
         */
        ret.aux = FALSE;               /* assumed for now */
        prevpos = 0;
        while (1) {
            if (iswhite(c) || c=='{' || c=='}' || c=='\\' || c==EOF) {
                /* Put back the character that caused termination */
                unget(in, c, &cpos);
                break;
            } else {
                rdadd(&rs, c);
                if (c == '-') {
                    prevpos = rsc.pos;
                    ret.aux = TRUE;
                    break;             /* hyphen terminates word */
                }
            }
            prevpos = rsc.pos;
            c = get(in, &cpos, &rsc);
        }
        ret.type = tok_word;
        ret.text = ustrdup(rs.text);
        if (rsc.text) {
            in->pushback_chars = dupstr(rsc.text + prevpos);
            rsc.text[prevpos] = '\0';
            ret.origtext = dupstr(rsc.text);
        } else {
            ret.origtext = dupstr("");
        }
        sfree(rs.text);
        sfree(rsc.text);
        return ret;
    }
}

/*
 * Determine whether the next input character is an open brace (for
 * telling code paragraphs from paragraphs which merely start with
 * code).
 */
int isbrace(input *in) {
    int c;
    filepos cpos;

    c = get(in, &cpos, NULL);
    unget(in, c, &cpos);
    return (c == '{');
}

/*
 * Read the rest of a line that starts `\c'. Including nothing at
 * all (tok_word with empty text).
 */
token get_codepar_token(input *in) {
    int c;
    token ret;
    rdstring rs = { 0, 0, NULL };
    filepos cpos;

    ret.type = tok_word;
    ret.origtext = NULL;
    c = get(in, &cpos, NULL);          /* expect (and discard) one space */
    ret.pos = cpos;
    if (c == ' ') {
        c = get(in, &cpos, NULL);
        ret.pos = cpos;
    }
    while (!isnl(c) && c != EOF) {
        int c2 = c;
        c = get(in, &cpos, NULL);
        /* Discard \r just before \n. */
        if (c2 != 13 || !isnl(c))
            rdadd(&rs, c2);
    }
    unget(in, c, &cpos);
    ret.text = ustrdup(rs.text);
    sfree(rs.text);
    return ret;
}

/*
 * Adds a new word to a linked list
 */
static word *addword(word newword, word ***hptrptr) {
    word *mnewword;
    if (!hptrptr)
        return NULL;
    mnewword = snew(word);
    *mnewword = newword;               /* structure copy */
    mnewword->next = NULL;
    **hptrptr = mnewword;
    *hptrptr = &mnewword->next;
    return mnewword;
}

/*
 * Adds a new paragraph to a linked list
 */
static paragraph *addpara(paragraph newpara, paragraph ***hptrptr) {
    paragraph *mnewpara = snew(paragraph);
    *mnewpara = newpara;               /* structure copy */
    mnewpara->next = NULL;
    **hptrptr = mnewpara;
    *hptrptr = &mnewpara->next;
    return mnewpara;
}

/*
 * Destructor before token is reassigned; should catch most memory
 * leaks
 */
#define dtor(t) ( sfree(t.text), sfree(t.origtext) )

/*
 * Reads a single file (ie until get() returns EOF)
 */
static void read_file(paragraph ***ret, input *in, indexdata *idx) {
    token t;
    paragraph par;
    word wd, **whptr, **idximplicit;
    tree234 *macros;
    wchar_t utext[2], *wdtext;
    int style, spcstyle;
    int already;
    int iswhite, seenwhite;
    int type;
    int prev_para_type;
    struct stack_item {
        enum {
            stack_nop = 0,             /* do nothing (for error recovery) */
            stack_ualt = 1,            /* \u alternative */
            stack_style = 2,           /* \e, \c, \cw */
            stack_idx = 4,             /* \I, \i, \ii */
            stack_hyper = 8,           /* \W */
            stack_quote = 16,          /* \q */
        } type;
        word **whptr;                  /* to restore from \u alternatives */
        word **idximplicit;            /* to restore from \u alternatives */
        filepos fpos;
        int in_code;
    } *sitem;
    stack parsestk;
    struct crossparaitem {
        int type;                      /* currently c_lcont, c_quote or -1 */
        int seen_lcont, seen_quote;
    };
    stack crossparastk;
    word *indexword, *uword, *iword;
    word *idxwordlist;
    rdstring indexstr;
    int index_downcase, index_visible, indexing;
    const rdstring nullrs = { 0, 0, NULL };
    wchar_t uchr;

    t.text = NULL;
    t.origtext = NULL;
    macros = newtree234(macrocmp);
    already = FALSE;

    crossparastk = stk_new();

    /*
     * Loop on each paragraph.
     */
    while (1) {
        int start_cmd = c__invalid;
        par.words = NULL;
        par.keyword = NULL;
        par.origkeyword = NULL;
        whptr = &par.words;

        /*
         * Get a token.
         */
        do {
            if (!already) {
                dtor(t), t = get_token(in);
            }
            already = FALSE;
        } while (t.type == tok_eop);
        if (t.type == tok_eof)
            break;

        /*
         * Parse code paragraphs separately.
         */
        if (t.type == tok_cmd && t.cmd == c_c && !isbrace(in)) {
            int wtype = word_WeakCode;

            par.type = para_Code;
            par.fpos = t.pos;
            while (1) {
                dtor(t), t = get_codepar_token(in);
                wd.type = wtype;
                wd.breaks = FALSE;     /* shouldn't need this... */
                wd.text = ustrdup(t.text);
                wd.alt = NULL;
                wd.fpos = t.pos;
                addword(wd, &whptr);
                dtor(t), t = get_token(in);
                if (t.type == tok_white) {
                    /*
                     * The newline after a code-paragraph line
                     */
                    dtor(t), t = get_token(in);
                }
                if (t.type == tok_eop || t.type == tok_eof ||
                    t.type == tok_rbrace) { /* might be } terminating \lcont */
                    if (t.type == tok_rbrace)
                        already = TRUE;
                    break;
                } else if (t.type == tok_cmd && t.cmd == c_c) {
                    wtype = word_WeakCode;
                } else if (t.type == tok_cmd && t.cmd == c_e &&
                           wtype == word_WeakCode) {
                    wtype = word_Emph;
                } else {
                    error(err_brokencodepara, &t.pos);
                    prev_para_type = par.type;
                    addpara(par, ret);
                    while (t.type != tok_eop)   /* error recovery: */
                        dtor(t), t = get_token(in);   /* eat rest of paragraph */
                    goto codeparabroken;   /* ick, but such is life */
                }
            }
            prev_para_type = par.type;
            addpara(par, ret);
            codeparabroken:
            continue;
        }

        /*
         * Spot the special commands that define a grouping of more
         * than one paragraph, and also the closing braces that
         * finish them.
         */
        if (t.type == tok_cmd &&
            (t.cmd == c_lcont || t.cmd == c_quote)) {
            struct crossparaitem *sitem, *stop;
            int cmd = t.cmd;

            /*
             * Expect, and swallow, an open brace.
             */
            dtor(t), t = get_token(in);
            if (t.type != tok_lbrace) {
                error(err_explbr, &t.pos);
                continue;
            }

            /*
             * Also expect, and swallow, any whitespace after that
             * (a newline before a code paragraph wouldn't be
             * surprising).
             */
            do {
                dtor(t), t = get_token(in);
            } while (t.type == tok_white);
            already = TRUE;

            if (cmd == c_lcont) {
                /*
                 * \lcont causes a continuation of a list item into
                 * multiple paragraphs (which may in turn contain
                 * nested lists, code paras etc). Hence, the previous
                 * paragraph must be of a list type.
                 */
                sitem = snew(struct crossparaitem);
                stop = (struct crossparaitem *)stk_top(crossparastk);
                if (stop)
                    *sitem = *stop;
                else
                    sitem->seen_quote = sitem->seen_lcont = 0;

                if (prev_para_type == para_Bullet ||
                    prev_para_type == para_NumberedList ||
                    prev_para_type == para_Description) {
                    sitem->type = c_lcont;
                    sitem->seen_lcont = 1;
                    par.type = para_LcontPush;
                    prev_para_type = par.type;
                    addpara(par, ret);
                } else {
                    /*
                     * Push a null item on the cross-para stack so that
                     * when we see the corresponding closing brace we
                     * don't give a cascade error.
                     */
                    sitem->type = -1;
                    error(err_misplacedlcont, &t.pos);
                }
            } else {
                /*
                 * \quote causes a group of paragraphs to be
                 * block-quoted (typically they will be indented a
                 * bit).
                 */
                sitem = snew(struct crossparaitem);
                stop = (struct crossparaitem *)stk_top(crossparastk);
                if (stop)
                    *sitem = *stop;
                else
                    sitem->seen_quote = sitem->seen_lcont = 0;
                sitem->type = c_quote;
                sitem->seen_quote = 1;
                par.type = para_QuotePush;
                prev_para_type = par.type;
                addpara(par, ret);
            }
            stk_push(crossparastk, sitem);
            continue;
        } else if (t.type == tok_rbrace) {
            struct crossparaitem *sitem = stk_pop(crossparastk);
            if (!sitem)
                error(err_unexbrace, &t.pos);
            else {
                switch (sitem->type) {
                  case c_lcont:
                    par.type = para_LcontPop;
                    prev_para_type = par.type;
                    addpara(par, ret);
                    break;
                  case c_quote:
                    par.type = para_QuotePop;
                    prev_para_type = par.type;
                    addpara(par, ret);
                    break;
                }
                sfree(sitem);
            }
            continue;
        }

        /*
         * This token begins a paragraph. See if it's one of the
         * special commands that define a paragraph type.
         *
         * (note that \# is special in a way, and \nocite takes no
         * text)
         */
        par.type = para_Normal;
        if (t.type == tok_cmd) {
            int needkw;
            int is_macro = FALSE;

            par.fpos = t.pos;
            switch (t.cmd) {
              default:
                needkw = -1;
                break;
              case c__invalid:
                error(err_badparatype, t.text, &t.pos);
                needkw = 4;
                break;
              case c__comment:
                if (isbrace(in))
                    break;             /* `\#{': isn't a comment para */
                do {
                    dtor(t), t = get_token(in);
                } while (t.type != tok_eop && t.type != tok_eof);
                continue;              /* next paragraph */
                /*
                 * `needkw' values:
                 *
                 *   1 -- exactly one keyword
                 *   2 -- at least one keyword
                 *   4 -- any number of keywords including zero
                 *   8 -- at least one keyword and then nothing else
                 *  16 -- nothing at all! no keywords, no body
                 *  32 -- no keywords at all
                 */
              case c_A: needkw = 2; par.type = para_Appendix; break;
              case c_B: needkw = 2; par.type = para_Biblio; break;
              case c_BR: needkw = 1; par.type = para_BR;
                start_cmd = c_BR; break;
              case c_C: needkw = 2; par.type = para_Chapter; break;
              case c_H: needkw = 2; par.type = para_Heading;
                par.aux = 0;
                break;
              case c_IM: needkw = 2; par.type = para_IM;
                start_cmd = c_IM; break;
              case c_S: needkw = 2; par.type = para_Subsect;
                par.aux = t.aux; break;
              case c_U: needkw = 32; par.type = para_UnnumberedChapter; break;
                /* For \b and \n the keyword is optional */
              case c_b: needkw = 4; par.type = para_Bullet; break;
              case c_dt: needkw = 4; par.type = para_DescribedThing; break;
              case c_dd: needkw = 4; par.type = para_Description; break;
              case c_n: needkw = 4; par.type = para_NumberedList; break;
              case c_cfg: needkw = 8; par.type = para_Config;
                start_cmd = c_cfg; break;
              case c_copyright: needkw = 32; par.type = para_Copyright; break;
              case c_define: is_macro = TRUE; needkw = 1; break;
                /* For \nocite the keyword is _everything_ */
              case c_nocite: needkw = 8; par.type = para_NoCite; break;
              case c_preamble: needkw = 32; par.type = para_Normal; break;
              case c_rule: needkw = 16; par.type = para_Rule; break;
              case c_title: needkw = 32; par.type = para_Title; break;
              case c_versionid: needkw = 32; par.type = para_VersionID; break;
            }

            if (par.type == para_Chapter ||
                par.type == para_Heading ||
                par.type == para_Subsect ||
                par.type == para_Appendix ||
                par.type == para_UnnumberedChapter) {
                struct crossparaitem *sitem = stk_top(crossparastk);
                if (sitem && (sitem->seen_lcont || sitem->seen_quote)) {
                    error(err_sectmarkerinblock,
                          &t.pos,
                          (sitem->seen_lcont ? "lcont" : "quote"));
                }
            }

            if (needkw > 0) {
                rdstring rs = { 0, 0, NULL };
                rdstringc rsc = { 0, 0, NULL };
                int nkeys = 0;
                filepos fp;

                /* Get keywords. */
                dtor(t), t = get_token(in);
                fp = t.pos;
                while (t.type == tok_lbrace) {
                    /* This is a keyword. */
                    nkeys++;
                    /* FIXME: there will be bugs if anyone specifies an
                     * empty keyword (\foo{}), so trap this case. */
                    while (dtor(t), t = get_token(in),
                           t.type == tok_word || 
                           t.type == tok_white ||
                           (t.type == tok_cmd && t.cmd == c__nbsp) ||
                           (t.type == tok_cmd && t.cmd == c__escaped) ||
                           (t.type == tok_cmd && t.cmd == c_u)) {
                        if (t.type == tok_white ||
                            (t.type == tok_cmd && t.cmd == c__nbsp)) {
                            rdadd(&rs, ' ');
                            rdaddc(&rsc, ' ');
                        } else if (t.type == tok_cmd && t.cmd == c_u) {
                            rdadd(&rs, t.aux);
                            rdaddc(&rsc, '\\');
                            rdaddsc(&rsc, t.origtext);
                        } else {
                            rdadds(&rs, t.text);
                            rdaddsc(&rsc, t.origtext);
                        }
                    }
                    if (t.type != tok_rbrace) {
                        error(err_kwunclosed, &t.pos);
                        continue;
                    }
                    rdadd(&rs, 0);     /* add string terminator */
                    rdaddc(&rsc, 0);   /* add string terminator */
                    dtor(t), t = get_token(in); /* eat right brace */
                }

                rdadd(&rs, 0);         /* add string terminator */
                rdaddc(&rsc, 0);       /* add string terminator */

                /* See whether we have the right number of keywords. */
                if ((needkw & 48) && nkeys > 0)
                    error(err_kwillegal, &fp);
                if ((needkw & 11) && nkeys == 0)
                    error(err_kwexpected, &fp);
                if ((needkw & 5) && nkeys > 1)
                    error(err_kwtoomany, &fp);

                if (is_macro) {
                    /*
                     * Macro definition. Get the rest of the line
                     * as a code-paragraph token, repeatedly until
                     * there's nothing more left of it. Separate
                     * with newlines.
                     */
                    rdstring macrotext = { 0, 0, NULL };
                    while (1) {
                        dtor(t), t = get_codepar_token(in);
                        if (macrotext.pos > 0)
                            rdadd(&macrotext, L'\n');
                        rdadds(&macrotext, t.text);
                        dtor(t), t = get_token(in);
                        if (t.type == tok_eop) break;
                    }
                    macrodef(macros, rs.text, macrotext.text, fp);
                    continue;          /* next paragraph */
                }

                par.keyword = rdtrim(&rs);
                par.origkeyword = rdtrimc(&rsc);

                /* Move to EOP in case of needkw==8 or 16 (no body) */
                if (needkw & 24) {
                    /* We allow whitespace even when we expect no para body */
                    while (t.type == tok_white)
                        dtor(t), t = get_token(in);
                    if (t.type != tok_eop && t.type != tok_eof &&
                        (start_cmd == c__invalid ||
                         t.type != tok_cmd || t.cmd != start_cmd)) {
                        error(err_bodyillegal, &t.pos);
                        /* Error recovery: eat the rest of the paragraph */
                        while (t.type != tok_eop && t.type != tok_eof &&
                               (start_cmd == c__invalid ||
                                t.type != tok_cmd || t.cmd != start_cmd))
                            dtor(t), t = get_token(in);
                    }
                    if (t.type == tok_cmd)
                        already = TRUE;/* inhibit get_token at top of loop */
                    prev_para_type = par.type;
                    addpara(par, ret);

                    if (par.type == para_Config) {
                        input_configure(in, &par);
                    }
                    continue;          /* next paragraph */
                }
            }
        }                 

        /*
         * Now read the actual paragraph, word by word, adding to
         * the paragraph list.
         *
         * Mid-paragraph commands:
         *
         *  \K \k
         *  \c \cw
         *  \e
         *  \i \ii
         *  \I
         *  \u
         *  \W
         *  \date
         *  \\ \{ \}
         */
        parsestk = stk_new();
        style = word_Normal;
        spcstyle = word_WhiteSpace;
        indexing = FALSE;
        seenwhite = TRUE;
        while (t.type != tok_eop && t.type != tok_eof) {
            iswhite = FALSE;
            already = FALSE;

            /* Handle implicit paragraph breaks after \IM, \BR etc */
            if (start_cmd != c__invalid &&
                t.type == tok_cmd && t.cmd == start_cmd) {
                already = TRUE;        /* inhibit get_token at top of loop */
                break;
            }

            if (t.type == tok_cmd && t.cmd == c__nop) {
                dtor(t), t = get_token(in);
                continue;              /* do nothing! */
            }

            if (t.type == tok_cmd && t.cmd == c__escaped) {
                t.type = tok_word;     /* nice and simple */
                t.aux = 0;             /* even if `\-' - nonbreaking! */
            }
            if (t.type == tok_cmd && t.cmd == c__nbsp) {
                t.type = tok_word;     /* nice and simple */
                sfree(t.text);
                t.text = ustrdup(L" ");  /* text is ` ' not `_' */
                t.aux = 0;             /* (nonbreaking) */
            }
            switch (t.type) {
              case tok_white:
                if (whptr == &par.words)
                    break;             /* strip whitespace at start of para */
                wd.text = NULL;
                wd.type = spcstyle;
                wd.alt = NULL;
                wd.aux = 0;
                wd.fpos = t.pos;
                wd.breaks = FALSE;

                /*
                 * Inhibit use of whitespace if it's (probably the
                 * newline) before a repeat \IM / \BR type
                 * directive.
                 */
                if (start_cmd != c__invalid) {
                    dtor(t), t = get_token(in);
                    already = TRUE;
                    if (t.type == tok_cmd && t.cmd == start_cmd)
                        break;
                }

                if (indexing)
                    rdadd(&indexstr, ' ');
                if (!indexing || index_visible)
                    addword(wd, &whptr);
                if (indexing)
                    addword(wd, &idximplicit);
                iswhite = TRUE;
                break;
              case tok_word:
                if (indexing)
                    rdadds(&indexstr, t.text);
                wd.type = style;
                wd.alt = NULL;
                wd.aux = 0;
                wd.fpos = t.pos;
                wd.breaks = t.aux;
                if (!indexing || index_visible) {
                    wd.text = ustrdup(t.text);
                    addword(wd, &whptr);
                }
                if (indexing) {
                    wd.text = ustrdup(t.text);
                    addword(wd, &idximplicit);
                }
                break;
              case tok_lbrace:
                error(err_unexbrace, &t.pos);
                /* Error recovery: push nop */
                sitem = snew(struct stack_item);
                sitem->type = stack_nop;
                sitem->fpos = t.pos;
                stk_push(parsestk, sitem);
                break;
              case tok_rbrace:
                sitem = stk_pop(parsestk);
                if (!sitem) {
                    /*
                     * This closing brace could have been an
                     * indication that the cross-paragraph stack
                     * wants popping. Accordingly, we treat it here
                     * as an indication that the paragraph is over.
                     */
                    already = TRUE;
                    goto finished_para;
                } else {
                    if (sitem->type & stack_ualt) {
                        whptr = sitem->whptr;
                        idximplicit = sitem->idximplicit;
                    }
                    if (sitem->type & stack_style) {
                        style = word_Normal;
                        spcstyle = word_WhiteSpace;
                    }
                    if (sitem->type & stack_idx) {
                        indexword->text = ustrdup(indexstr.text);
                        if (index_downcase) {
                            word *w;

                            ustrlow(indexword->text);
                            ustrlow(indexstr.text);

                            for (w = idxwordlist; w; w = w->next)
                                if (w->text)
                                    ustrlow(w->text);
                        }
                        indexing = FALSE;
                        rdadd(&indexstr, L'\0');
                        index_merge(idx, FALSE, indexstr.text,
                                    idxwordlist, &sitem->fpos);
                        sfree(indexstr.text);
                    }
                    if (sitem->type & stack_hyper) {
                        wd.text = NULL;
                        wd.type = word_HyperEnd;
                        wd.alt = NULL;
                        wd.aux = 0;
                        wd.fpos = t.pos;
                        wd.breaks = FALSE;
                        if (!indexing || index_visible)
                            addword(wd, &whptr);
                        if (indexing)
                            addword(wd, &idximplicit);
                    }
                    if (sitem->type & stack_quote) {
                        wd.text = NULL;
                        wd.type = toquotestyle(style);
                        wd.alt = NULL;
                        wd.aux = quote_Close;
                        wd.fpos = t.pos;
                        wd.breaks = FALSE;
                        if (!indexing || index_visible)
                            addword(wd, &whptr);
                        if (indexing) {
                            rdadd(&indexstr, L'"');
                            addword(wd, &idximplicit);
                        }
                    }
                }
                sfree(sitem);
                break;
              case tok_cmd:
                switch (t.cmd) {
                  case c__comment:
                    /*
                     * In-paragraph comment: \#{ balanced braces }
                     *
                     * Anything goes here; even tok_eop. We should
                     * eat whitespace after the close brace _if_
                     * there was whitespace before the \#.
                     */
                    dtor(t), t = get_token(in);
                    if (t.type != tok_lbrace) {
                        error(err_explbr, &t.pos);
                    } else {
                        int braces = 1;
                        while (braces > 0) {
                            dtor(t), t = get_token(in);
                            if (t.type == tok_lbrace)
                                braces++;
                            else if (t.type == tok_rbrace)
                                braces--;
                            else if (t.type == tok_eof) {
                                error(err_commenteof, &t.pos);
                                break;
                            }
                        }
                    }
                    if (seenwhite) {
                        already = TRUE;
                        dtor(t), t = get_token(in);
                        if (t.type == tok_white) {
                            iswhite = TRUE;
                            already = FALSE;
                        }
                    }
                    break;
                  case c_q:
                    dtor(t), t = get_token(in);
                    if (t.type != tok_lbrace) {
                        error(err_explbr, &t.pos);
                    } else {
                        /*
                         * Enforce that \q may not be used anywhere
                         * within \c. (It shouldn't be necessary
                         * since the whole point of \c should be
                         * that the user wants to exercise exact
                         * control over the glyphs used, and
                         * forbidding it has the useful effect of
                         * relieving some backends of having to
                         * make difficult decisions.)
                         */
                        int stype;

                        if (style != word_Code && style != word_WeakCode) {
                            wd.text = NULL;
                            wd.type = toquotestyle(style);
                            wd.alt = NULL;
                            wd.aux = quote_Open;
                            wd.fpos = t.pos;
                            wd.breaks = FALSE;
                            if (!indexing || index_visible)
                                addword(wd, &whptr);
                            if (indexing) {
                                rdadd(&indexstr, L'"');
                                addword(wd, &idximplicit);
                            }
                            stype = stack_quote;
                        } else {
                            error(err_codequote, &t.pos);
                            stype = stack_nop;
                        }
                        sitem = snew(struct stack_item);
                        sitem->fpos = t.pos;
                        sitem->type = stype;
                        stk_push(parsestk, sitem);
                    }
                    break;
                  case c_K:
                  case c_k:
                  case c_W:
                  case c_date:
                    /*
                     * Keyword, hyperlink, or \date. We expect a
                     * left brace, some text, and then a right
                     * brace. No nesting; no arguments.
                     */
                    wd.fpos = t.pos;
                    wd.breaks = FALSE;
                    if (t.cmd == c_K)
                        wd.type = word_UpperXref;
                    else if (t.cmd == c_k)
                        wd.type = word_LowerXref;
                    else if (t.cmd == c_W)
                        wd.type = word_HyperLink;
                    else
                        wd.type = word_Normal;
                    dtor(t), t = get_token(in);
                    if (t.type != tok_lbrace) {
                        if (wd.type == word_Normal) {
                            time_t thetime = time(NULL);
                            struct tm *broken = localtime(&thetime);
                            already = TRUE;
                            wdtext = ustrftime(NULL, broken);
                            wd.type = style;
                        } else {
                            error(err_explbr, &t.pos);
                            wdtext = NULL;
                        }
                    } else {
                        rdstring rs = { 0, 0, NULL };
                        while (dtor(t), t = get_token(in),
                               t.type == tok_word || t.type == tok_white) {
                            if (t.type == tok_white)
                                rdadd(&rs, ' ');
                            else
                                rdadds(&rs, t.text);
                        }
                        if (wd.type == word_Normal) {
                            time_t thetime = time(NULL);
                            struct tm *broken = localtime(&thetime);
                            wdtext = ustrftime(rs.text, broken);
                            wd.type = style;
                        } else {
                            wdtext = ustrdup(rs.text);
                        }
                        sfree(rs.text);
                        if (t.type != tok_rbrace) {
                            error(err_kwexprbr, &t.pos);
                        }
                    }
                    wd.alt = NULL;
                    wd.aux = 0;
                    if (!indexing || index_visible) {
                        wd.text = ustrdup(wdtext);
                        addword(wd, &whptr);
                    }
                    if (indexing) {
                        wd.text = ustrdup(wdtext);
                        addword(wd, &idximplicit);
                    }
                    sfree(wdtext);
                    if (wd.type == word_HyperLink) {
                        /*
                         * Hyperlinks are different: they then
                         * expect another left brace, to begin
                         * delimiting the text marked by the link.
                         */
                        dtor(t), t = get_token(in);
                        sitem = snew(struct stack_item);
                        sitem->fpos = wd.fpos;
                        sitem->type = stack_hyper;
                        /*
                         * Special cases: \W{}\i, \W{}\ii
                         */
                        if (t.type == tok_cmd &&
                            (t.cmd == c_i || t.cmd == c_ii)) {
                            if (indexing) {
                                error(err_nestedindex, &t.pos);
                            } else {
                                /* Add an index-reference word with no
                                 * text as yet */
                                wd.type = word_IndexRef;
                                wd.text = NULL;
                                wd.alt = NULL;
                                wd.aux = 0;
                                wd.breaks = FALSE;
                                indexword = addword(wd, &whptr);
                                /* Set up a rdstring to read the
                                 * index text */
                                indexstr = nullrs;
                                /* Flags so that we do the Right
                                 * Things with text */
                                index_visible = (type != c_I);
                                index_downcase = (type == c_ii);
                                indexing = TRUE;
                                idxwordlist = NULL;
                                idximplicit = &idxwordlist;

                                sitem->type |= stack_idx;
                            }
                            dtor(t), t = get_token(in);
                        }
                        /*
                         * Special cases: \W{}\c, \W{}\e, \W{}\cw
                         */
                        if (t.type == tok_cmd &&
                            (t.cmd == c_e || t.cmd == c_c || t.cmd == c_cw)) {
                            if (style != word_Normal)
                                error(err_nestedstyles, &t.pos);
                            else {
                                style = (t.cmd == c_c ? word_Code :
                                         t.cmd == c_cw ? word_WeakCode :
                                         word_Emph);
                                spcstyle = tospacestyle(style);
                                sitem->type |= stack_style;
                            }
                            dtor(t), t = get_token(in);
                        }
                        if (t.type != tok_lbrace) {
                            error(err_explbr, &t.pos);
                            sfree(sitem);
                        } else {
                            stk_push(parsestk, sitem);
                        }
                    }
                    break;
                  case c_c:
                  case c_cw:
                  case c_e:
                    type = t.cmd;
                    if (style != word_Normal) {
                        error(err_nestedstyles, &t.pos);
                        /* Error recovery: eat lbrace, push nop. */
                        dtor(t), t = get_token(in);
                        sitem = snew(struct stack_item);
                        sitem->fpos = t.pos;
                        sitem->type = stack_nop;
                        stk_push(parsestk, sitem);
                    }
                    dtor(t), t = get_token(in);
                    if (t.type != tok_lbrace) {
                        error(err_explbr, &t.pos);
                    } else {
                        style = (type == c_c ? word_Code :
                                 type == c_cw ? word_WeakCode :
                                 word_Emph);
                        spcstyle = tospacestyle(style);
                        sitem = snew(struct stack_item);
                        sitem->fpos = t.pos;
                        sitem->type = stack_style;
                        stk_push(parsestk, sitem);
                    }
                    break;
                  case c_i:
                  case c_ii:
                  case c_I:
                    type = t.cmd;
                    if (indexing) {
                        error(err_nestedindex, &t.pos);
                        /* Error recovery: eat lbrace, push nop. */
                        dtor(t), t = get_token(in);
                        sitem = snew(struct stack_item);
                        sitem->fpos = t.pos;
                        sitem->type = stack_nop;
                        stk_push(parsestk, sitem);
                    }
                    sitem = snew(struct stack_item);
                    sitem->fpos = t.pos;
                    sitem->type = stack_idx;
                    dtor(t), t = get_token(in);
                    /*
                     * Special cases: \i\c, \i\e, \i\cw
                     */
                    wd.fpos = t.pos;
                    if (t.type == tok_cmd &&
                        (t.cmd == c_e || t.cmd == c_c || t.cmd == c_cw)) {
                        if (style != word_Normal)
                            error(err_nestedstyles, &t.pos);
                        else {
                            style = (t.cmd == c_c ? word_Code :
                                     t.cmd == c_cw ? word_WeakCode :
                                     word_Emph);
                            spcstyle = tospacestyle(style);
                            sitem->type |= stack_style;
                        }
                        dtor(t), t = get_token(in);
                    }
                    if (t.type != tok_lbrace) {
                        sfree(sitem);
                        error(err_explbr, &t.pos);
                    } else {
                        /* Add an index-reference word with no text as yet */
                        wd.type = word_IndexRef;
                        wd.text = NULL;
                        wd.alt = NULL;
                        wd.aux = 0;
                        wd.breaks = FALSE;
                        indexword = addword(wd, &whptr);
                        /* Set up a rdstring to read the index text */
                        indexstr = nullrs;
                        /* Flags so that we do the Right Things with text */
                        index_visible = (type != c_I);
                        index_downcase = (type == c_ii);
                        indexing = TRUE;
                        idxwordlist = NULL;
                        idximplicit = &idxwordlist;
                        /* Stack item to close the indexing on exit */
                        stk_push(parsestk, sitem);
                    }
                    break;
                  case c_u:
                    uchr = t.aux;
                    utext[0] = uchr; utext[1] = 0;
                    wd.type = style;
                    wd.breaks = FALSE;
                    wd.alt = NULL;
                    wd.aux = 0;
                    wd.fpos = t.pos;
                    if (!indexing || index_visible) {
                        wd.text = ustrdup(utext);
                        uword = addword(wd, &whptr);
                    } else
                        uword = NULL;
                    if (indexing) {
                        wd.text = ustrdup(utext);
                        iword = addword(wd, &idximplicit);
                    } else
                        iword = NULL;
                    dtor(t), t = get_token(in);
                    if (t.type == tok_lbrace) {
                        /*
                         * \u with a left brace. Until the brace
                         * closes, all further words go on a
                         * sidetrack from the main thread of the
                         * paragraph.
                         */
                        sitem = snew(struct stack_item);
                        sitem->fpos = t.pos;
                        sitem->type = stack_ualt;
                        sitem->whptr = whptr;
                        sitem->idximplicit = idximplicit;
                        stk_push(parsestk, sitem);
                        whptr = uword ? &uword->alt : NULL;
                        idximplicit = iword ? &iword->alt : NULL;
                    } else {
                        if (indexing)
                            rdadd(&indexstr, uchr);
                        already = TRUE;
                    }
                    break;
                  default:
                    if (!macrolookup(macros, in, t.text, &t.pos))
                        error(err_badmidcmd, t.text, &t.pos);
                    break;
                }
            }
            if (!already)
                dtor(t), t = get_token(in);
            seenwhite = iswhite;
        }
        finished_para:
        /* Check the stack is empty */
        if (stk_top(parsestk)) {
            while ((sitem = stk_pop(parsestk)))
                sfree(sitem);
            error(err_missingrbrace, &t.pos);
        }
        stk_free(parsestk);
        prev_para_type = par.type;
        addpara(par, ret);
        if (t.type == tok_eof)
            already = TRUE;
    }

    if (stk_top(crossparastk)) {
        void *p;

        error(err_missingrbrace2, &t.pos);
        while ((p = stk_pop(crossparastk)))
            sfree(p);
    }

    /*
     * We break to here rather than returning, because otherwise
     * this cleanup doesn't happen.
     */
    dtor(t);
    macrocleanup(macros);

    stk_free(crossparastk);
}

paragraph *read_input(input *in, indexdata *idx) {
    paragraph *head = NULL;
    paragraph **hptr = &head;

    while (in->currindex < in->nfiles) {
        in->currfp = fopen(in->filenames[in->currindex], "r");
        if (in->currfp) {
            setpos(in, in->filenames[in->currindex]);
            in->charset = in->defcharset;
            in->csstate = charset_init_state;
            in->wcpos = in->nwc = 0;
            in->pushback_chars = NULL;
            read_file(&hptr, in, idx);
        }
        in->currindex++;
    }

    return head;
}