Refactoring the iff decoder

[deark.git] / modules / hlp.c

// This file is part of Deark.
// Copyright (C) 2017 Jason Summers
// See the file COPYING for terms of use.

// Windows HLP

// This module was developed with the help of information from the helpfile.txt
// document included with the helpdeco software by M. Winterhoff.

#include <deark-config.h>
#include <deark-private.h>
#include <deark-fmtutil.h>
DE_DECLARE_MODULE(de_module_hlp);

#define TOPICBLOCKHDRSIZE 12
#define INVALIDPOS 0xffffffffU

enum hlp_filetype {
        FILETYPE_UNKNOWN = 0,
        FILETYPE_OTHERSPECIAL,
        FILETYPE_EXTRACTABLE,
        FILETYPE_INTERNALDIR,
        FILETYPE_SYSTEM,
        FILETYPE_TOPIC,
        FILETYPE_SHG,
        FILETYPE_PHRASES,
        FILETYPE_PHRINDEX,
        FILETYPE_PHRIMAGE
};

struct bptree {
        unsigned int flags;
        i64 pagesize;
        i64 root_page;
        i64 num_levels;
        i64 num_pages;
        i64 num_entries;
        i64 pagesdata_pos;
        i64 first_leaf_page;
};

struct phrase_item {
        u32 pos; // pos in ->phrases_data
        u32 len;
};

typedef struct localctx_struct {
        int input_encoding;
        int output_is_utf8;
        int extract_text;
        u8 extract_raw_streams;
        i64 internal_dir_FILEHEADER_offs;
        struct bptree bpt;
        u8 found_system_file;
        u8 found_Phrases_file;
        u8 found_PhrIndex_file;
        u8 found_PhrImage_file;
        u8 found_TOPIC_file;
        u8 valid_Phrases_file;
        i64 offset_of_system_file;
        i64 offset_of_Phrases;
        i64 offset_of_PhrIndex;
        i64 offset_of_PhrImage;
        i64 offset_of_TOPIC;
        int ver_major;
        int ver_minor;
        i64 topic_block_size;
        int is_lz77_compressed;
        int uses_old_phrase_compression;
        int uses_hall_compression;
        int pass;
        int has_shg, has_ico, has_bmp;
        i64 internal_dir_num_levels;
        dbuf *outf_text;
        i64 num_topic_blocks;
        dbuf *tmpdbuf1;
        dbuf *unc_linkdata2_dbuf;
        i64 PhrImageUncSize;
        i64 PhrImageCmprSize;
        dbuf *phrases_data;
        unsigned int num_phrases;
        struct phrase_item *phrase_info; // array [num_phrases]
        de_ucstring *tmpucstring1;
        de_ucstring *help_file_title;
        de_ucstring *help_file_copyright;
        struct de_timestamp gendate;
} lctx;

static void do_file(deark *c, lctx *d, i64 pos1, enum hlp_filetype file_fmt, int extract_only,
        struct de_stringreaderdata *fn);

struct systemrec_info {
        unsigned int rectype;

        // low 8 bits = version info
        // 0x0010 = STRINGZ type
        unsigned int flags;

        const char *name;
        void *reserved;
};
static const struct systemrec_info systemrec_info_arr[] = {
        { 1,  0x0010, "Title", NULL },
        { 2,  0x0010, "Copyright", NULL },
        { 3,  0x0000, "Contents", NULL },
        { 4,  0x0010, "Macro", NULL },
        { 5,  0x0000, "Icon", NULL },
        { 6,  0x0000, "Window", NULL },
        { 8,  0x0010, "Citation", NULL },
        { 9,  0x0000, "Language ID", NULL },
        { 10, 0x0010, "CNT file name", NULL },
        { 11, 0x0000, "Charset", NULL },
        { 12, 0x0000, "Default dialog font", NULL },
        { 13, 0x0010, "Defined GROUPs", NULL },
        { 14, 0x0011, "IndexSeparators", NULL },
        { 14, 0x0002, "Multimedia Help Files", NULL },
        { 18, 0x0010, "Defined language", NULL },
        { 19, 0x0000, "Defined DLLMAPS", NULL }
};
static const struct systemrec_info systemrec_info_default =
        { 0, 0x0000, "?", NULL };

static void format_topiclink(deark *c, lctx *d, u32 n, char *buf, size_t buf_len)
{
        if(d->ver_minor<=16) {
                de_snprintf(buf, buf_len, "%u", (UI)n);
        }
        else {
                if(n==INVALIDPOS) {
                        de_strlcpy(buf, "-1", buf_len);
                }
                else {
                        de_snprintf(buf, buf_len, "Blk%u:%u", (UI)(n/16384),
                                (UI)(n%16384));
                }
        }
}

static void hlptime_to_timestamp(i64 ht, struct de_timestamp *ts)
{
        if(ht!=0) {
                de_unix_time_to_timestamp(ht, ts, 0);
        }
        else {
                ts->is_valid = 0;
        }
}

// s can be NULL, or it can be a string to save the value in.
static void do_display_and_store_STRINGZ(deark *c, lctx *d, i64 pos1, i64 len,
        const char *name, de_ucstring *s1)
{
        de_ucstring *s_tmp = NULL;
        de_ucstring *s;

        if(s1) {
                s = s1;
        }
        else {
                s_tmp = ucstring_create(c);
                s = s_tmp;
        }

        ucstring_empty(s);
        if(len<1) return;

        dbuf_read_to_ucstring_n(c->infile,
                pos1, len, DE_DBG_MAX_STRLEN,
                s, DE_CONVFLAG_STOP_AT_NUL, d->input_encoding);
        de_dbg(c, "%s: \"%s\"", name, ucstring_getpsz(s));

        if(s_tmp) ucstring_destroy(s_tmp);
}

static void do_SYSTEMREC_STRINGZ(deark *c, lctx *d, unsigned int recordtype,
        i64 pos1, i64 len, const struct systemrec_info *sti, de_ucstring *s)
{
        do_display_and_store_STRINGZ(c, d, pos1, len, sti->name, s);
}

static void do_SYSTEMREC_uint32_hex(deark *c, lctx *d, unsigned int recordtype,
        i64 pos1, i64 len)
{
        unsigned int n;

        if(len!=4) return;
        n = (unsigned int)de_getu32le(pos1);
        de_dbg(c, "value: 0x%08x", n);
}

static void extract_system_icon(deark *c, lctx *d, i64 pos, i64 len)
{
        de_finfo *fi = NULL;

        fi = de_finfo_create(c);
        fi->timestamp[DE_TIMESTAMPIDX_MODIFY] = d->gendate;
        dbuf_create_file_from_slice(c->infile, pos, len, "ico", fi, DE_CREATEFLAG_IS_AUX);
        de_finfo_destroy(c, fi);
}

static void do_SYSTEMREC(deark *c, lctx *d, unsigned int recordtype,
        i64 pos1, i64 len, const struct systemrec_info *sti)
{
        if(recordtype==1) { // title
                if(!d->help_file_title) {
                        d->help_file_title = ucstring_create(c);
                }
                do_SYSTEMREC_STRINGZ(c, d, recordtype, pos1, len, sti, d->help_file_title);
        }
        else if(recordtype==2) { // copyright
                if(!d->help_file_copyright) {
                        d->help_file_copyright = ucstring_create(c);
                }
                do_SYSTEMREC_STRINGZ(c, d, recordtype, pos1, len, sti, d->help_file_copyright);
        }
        else if(recordtype==3 && len==4) { // contents
                do_SYSTEMREC_uint32_hex(c, d, recordtype, pos1, len);
        }
        else if(recordtype==5) { // Icon
                d->has_ico = 1;
                extract_system_icon(c, d, pos1, len);
        }
        else if(sti->flags&0x10) {
                do_SYSTEMREC_STRINGZ(c, d, recordtype, pos1, len, sti, NULL);
        }
        else {
                if(c->debug_level>=2) {
                        de_dbg_hexdump(c, c->infile, pos1, len, 256, NULL, 0x1);
                }
        }
}

static const struct systemrec_info *find_sysrec_info(deark *c, lctx *d, unsigned int t)
{
        size_t i;

        for(i=0; i<DE_ARRAYCOUNT(systemrec_info_arr); i++) {
                const struct systemrec_info *sti;
                sti = &systemrec_info_arr[i];
                if(sti->rectype==t &&
                        (sti->flags&0x0f)==0)
                {
                        return sti;
                }
        }
        return &systemrec_info_default;
}

static int do_file_SYSTEM_header(deark *c, lctx *d, i64 pos1)
{
        i64 pos = pos1;
        i64 magic;
        i64 gen_date;
        unsigned int flags;
        char timestamp_buf[64];
        int retval = 0;

        magic = de_getu16le_p(&pos);
        if(magic!=0x036c) {
                de_err(c, "Expected SYSTEM data at %d not found", (int)pos1);
                goto done;
        }

        de_dbg(c, "SYSTEM file data at %d", (int)pos1);
        de_dbg_indent(c, 1);

        d->ver_minor = (int)de_getu16le_p(&pos);
        d->ver_major = (int)de_getu16le_p(&pos);
        de_dbg(c, "help format version: %d.%d", d->ver_major, d->ver_minor);

        if(d->ver_major!=1) {
                de_err(c, "Unsupported file version: %d.%d", d->ver_major, d->ver_minor);
                goto done;
        }

        gen_date = de_geti32le_p(&pos);
        hlptime_to_timestamp(gen_date, &d->gendate);
        de_timestamp_to_string(&d->gendate, timestamp_buf, sizeof(timestamp_buf), 0);
        de_dbg(c, "GenDate: %d (%s)", (int)gen_date, timestamp_buf);

        flags = (unsigned int)de_getu16le_p(&pos);
        de_dbg(c, "system flags: 0x%04x", flags);

        if(d->ver_minor>16) {
                if(flags==8) {
                        d->is_lz77_compressed = 1;
                        d->topic_block_size = 2048;
                }
                else if(flags==4) {
                        d->is_lz77_compressed = 1;
                        d->topic_block_size = 4096;
                }
                else {
                        d->is_lz77_compressed = 0;
                        d->topic_block_size = 4096;
                }
        }
        else {
                d->is_lz77_compressed = 0;
                d->topic_block_size = 2048;
        }
        de_dbg(c, "lz77 compression: %d", d->is_lz77_compressed);
        de_dbg(c, "topic block size: %d", (int)d->topic_block_size);

        retval = 1;
done:
        return retval;
}

static void do_file_SYSTEM_SYSTEMRECS(deark *c, lctx *d, i64 pos1, i64 len,
        int systemrecs_pass)
{
        i64 pos = pos1;

        while((pos1+len)-pos >=4) {
                unsigned int recordtype;
                i64 datasize;
                i64 systemrec_startpos;
                const struct systemrec_info *sti;

                systemrec_startpos = pos;

                recordtype = (unsigned int)de_getu16le_p(&pos);
                datasize = de_getu16le_p(&pos);

                sti = find_sysrec_info(c, d, recordtype);
                de_dbg(c, "SYSTEMREC type %u (%s) at %d, dpos=%d, dlen=%d",
                        recordtype, sti->name,
                        (int)systemrec_startpos, (int)pos, (int)datasize);

                if(pos+datasize > pos1+len) break; // bad data
                de_dbg_indent(c, 1);
                do_SYSTEMREC(c, d, recordtype, pos, datasize, sti);
                de_dbg_indent(c, -1);
                pos += datasize;
        }
}

static void do_file_SYSTEM(deark *c, lctx *d, i64 pos1, i64 len)
{
        i64 pos = pos1;
        int saved_indent_level;

        de_dbg_indent_save(c, &saved_indent_level);

        // We'll read the SYSTEM "file" before pass 2, most importantly to record
        // the format version information.
        //
        // The SYSTEM file may contain a series of SYSTEMREC records that we want
        // to parse.
        // Note: It seems like we might have to make two (sub)passes over the
        // SYSTEMREC records, the first pass to collect the "charset" setting, so it
        // can be used to interpret records that appear before it. But I've never
        // seen a charset record that I can make sense of -- it's usually just a
        // random number of NUL bytes.

        if(d->pass!=1) goto done;

        if(!do_file_SYSTEM_header(c, d, pos)) goto done;
        pos += 12;

        if(d->ver_minor<=16) {
                d->help_file_title = ucstring_create(c);
                do_display_and_store_STRINGZ(c, d, pos, (pos1+len)-pos, "HelpFileTitle", d->help_file_title);
        }
        else {
                // A sequence of variable-sized SYSTEMRECs
                do_file_SYSTEM_SYSTEMRECS(c, d, pos, (pos1+len)-pos, 1);
        }

done:
        de_dbg_indent_restore(c, saved_indent_level);
}

static void do_file_SHG(deark *c, lctx *d, i64 pos1, i64 used_space)
{
        i64 oldsig;
        const char *ext;
        dbuf *outf = NULL;
        de_finfo *fi = NULL;

        // Reportedly, 0x506c = SHG = 1 image, and 0x706c = MRB = >1 image.
        // But I'm not convinced that's correct.
        // I'm to sure what to do, as far as selecting a file extension, and potentially
        // correcting the signature. Current behavior is to leave the signature the same,
        // and derive the file extension from the number of images.
        oldsig = de_getu16le(pos1);

        if(oldsig==0x506c || oldsig==0x706c) {
                i64 num_images;

                num_images = de_getu16le(pos1+2);
                if(num_images>1) {
                        ext="mrb";
                }
                else {
                        ext="shg";
                }
        }
        else {
                ext="bin";
        }

        fi = de_finfo_create(c);
        // (Note that if we were to correct the signature, we probably should not copy
        // the mod time.)
        fi->timestamp[DE_TIMESTAMPIDX_MODIFY] = d->gendate;
        outf = dbuf_create_output_file(c, ext, fi, 0);
        dbuf_copy(c->infile, pos1, used_space, outf);
        dbuf_close(outf);
        de_finfo_destroy(c, fi);
}

static void do_extract_raw_file(deark *c, lctx *d, i64 pos1, i64 used_space,
        struct de_stringreaderdata *fn)
{
        de_finfo *fi = NULL;
        const char *ext = NULL;

        fi = de_finfo_create(c);
        fi->timestamp[DE_TIMESTAMPIDX_MODIFY] = d->gendate;
        if(fn && ucstring_isnonempty(fn->str)) {
                de_finfo_set_name_from_ucstring(c, fi, fn->str, 0);
                fi->original_filename_flag = 1;
        }
        else {
                ext = "bin";
        }
        dbuf_create_file_from_slice(c->infile, pos1, used_space, ext, fi, 0);

        de_finfo_destroy(c, fi);
}

struct topiclink_data {
        i64 blocksize;
        i64 datalen2;
        u32 prevblock;
        u32 nextblock;
        i64 datalen1;
        u8 recordtype;

        i64 linkdata1_pos;
        i64 linkdata1_len;
        i64 linkdata2_pos;
        i64 linkdata2_cmprlen;
        i64 linkdata2_uncmprlen;

        i64 paragraphinfo_pos;
        u8 seems_compressed;
};

struct topic_block_info_item {
        i64 pos; // position in ->unc_topicdata
        i64 len;
};

struct topic_ctx {
        i64 num_topic_blocks;
        struct topic_block_info_item *topic_block_info; // array [num_topic_blocks]
        dbuf *unc_topicdata;
        u32 pos_of_first_topiclink;
};

static void ensure_text_output_file_open(deark *c, lctx *d)
{
        if(d->outf_text) return;
        d->outf_text = dbuf_create_output_file(c, "dump.txt", NULL, 0);
        if(d->output_is_utf8 && c->write_bom) {
                dbuf_write_uchar_as_utf8(d->outf_text, 0xfeff);
        }
        if(ucstring_isnonempty(d->help_file_title)) {
                dbuf_puts(d->outf_text, "Title: ");
                // TODO: This doesn't do the right thing if !d->output_is_utf8.
                ucstring_write_as_utf8(c, d->help_file_title, d->outf_text, 0);
                dbuf_puts(d->outf_text, "\n");
        }
        if(ucstring_isnonempty(d->help_file_copyright)) {
                dbuf_puts(d->outf_text, "Copyright: ");
                ucstring_write_as_utf8(c, d->help_file_copyright, d->outf_text, 0);
                dbuf_puts(d->outf_text, "\n");
        }
}

// Emit a string that needs no conversion.
static void emit_raw_sz(deark *c, lctx *d, const char *sz)
{
        if(!d->outf_text) return;
        dbuf_puts(d->outf_text, sz);
}

// Emit a content string, i.e. one that might need character encoding conversion
// or escaping.
static void emit_slice(deark *c, lctx *d, dbuf *inf, i64 pos, i64 len)
{
        if(!d->outf_text) return;

        if(!d->output_is_utf8) {
                dbuf_copy(inf, pos, len, d->outf_text);
                return;
        }

        ucstring_empty(d->tmpucstring1);
        dbuf_read_to_ucstring(inf, pos, len, d->tmpucstring1, 0, d->input_encoding);
        ucstring_write_as_utf8(c, d->tmpucstring1, d->outf_text, 0);
}

static void emit_phrase(deark *c, lctx *d, dbuf *outf, unsigned int phrasenum)
{
        if(phrasenum < d->num_phrases) {
                dbuf_copy(d->phrases_data, (i64)d->phrase_info[phrasenum].pos,
                        (i64)d->phrase_info[phrasenum].len, outf);
        }
}

static void do_phrase_decompression(deark *c, lctx *d, dbuf *inf, i64 pos1, i64 len,
        dbuf *outf,  i64 unc_len_expected)
{
        i64 pos = pos1;
        i64 endpos = pos1+len;

        if(!d->phrases_data) return;

        while(1) {
                u8 b;

                if(pos >= endpos) break;
                b = dbuf_getbyte_p(inf, &pos);
                if(b==0 || b>=0x10) {
                        dbuf_writebyte(outf, b);
                }
                else {
                        u8 b2;
                        unsigned int n;

                        if(pos >= endpos) break;
                        b2 = dbuf_getbyte_p(inf, &pos);
                        n = ((unsigned int)(b-1)<<8) | b2;
                        emit_phrase(c, d, outf, n>>1);
                        if(n & 0x1) {
                                dbuf_writebyte(outf, ' ');
                        }
                }
        }
}

static void do_hall_decompression(deark *c, lctx *d, dbuf *inf, i64 pos1, i64 len,
        dbuf *outf, i64 unc_len_expected)
{
        static const u8 action[16] = {0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4};
        i64 pos = pos1;
        i64 endpos = pos1+len;
        unsigned int n;
        i64 outf_expected_endpos;

        outf_expected_endpos = outf->len + unc_len_expected;

        while(1) {
                u8 b;

                if(outf->len >= outf_expected_endpos) goto unc_done;
                if(pos >= endpos) goto unc_done;
                b = dbuf_getbyte_p(inf, &pos);
                switch(action[b&0x0f]) {
                case 0:
                        emit_phrase(c, d, outf, b>>1);
                        break;
                case 1:
                        if(pos >= endpos) goto unc_done;
                        n = (((unsigned int)b & 0xfc) << 6) | 0x80;
                        n += dbuf_getbyte_p(inf, &pos);
                        emit_phrase(c, d, outf, n);
                        break;
                case 2:
                        n = (b >> 3) +1;
                        if(pos + (i64)n > endpos) goto unc_done;
                        dbuf_copy(inf, pos, (i64)n, outf);
                        pos += (i64)n;
                        break;
                case 3:
                        dbuf_write_run(outf, ' ', (i64)(b>>4)+1);
                        break;
                default: // 4
                        dbuf_write_zeroes(outf, (i64)(b>>4)+1);
                        break;
                }
        }
unc_done:
        ;
}

static int do_topiclink_rectype_32_linkdata1(deark *c, lctx *d,
        struct topic_ctx *tctx, struct topiclink_data *tld)
{
        i64 pos = tld->linkdata1_pos;
        dbuf *inf = tctx->unc_topicdata;
        i64 topicsize;
        i64 topiclength;
        unsigned int id;
        unsigned int bits;
        int retval = 0;

        // TODO: type 33 (table)
        if(tld->recordtype!=1 && tld->recordtype!=32) goto done;

        topicsize = fmtutil_hlp_get_csl_p(inf, &pos);
        de_dbg(c, "topic size: %"I64_FMT, topicsize);

        if(tld->recordtype==32) {
                topiclength = fmtutil_hlp_get_cus_p(inf, &pos);
                de_dbg(c, "topic length: %"I64_FMT, topiclength);
        }

        pos++; // unknownUnsignedChar
        pos++; // unknownBiasedChar
        id = (unsigned int)dbuf_getu16le_p(inf, &pos);
        de_dbg(c, "id: %u", id);
        bits = (unsigned int)dbuf_getu16le_p(inf, &pos);
        de_dbg(c, "bits: 0x%04x", bits);

        if(bits & 0x0001) { // Unknown
                (void)fmtutil_hlp_get_csl_p(inf, &pos);
        }
        if(bits & 0x0002) { // SpacingAbove
                (void)fmtutil_hlp_get_css_p(inf, &pos);
        }
        if(bits & 0x0004) { // SpacingBelow
                (void)fmtutil_hlp_get_css_p(inf, &pos);
        }
        if(bits & 0x0008) { // SpacingLines
                (void)fmtutil_hlp_get_css_p(inf, &pos);
        }
        if(bits & 0x0010) { // LeftIndent
                (void)fmtutil_hlp_get_css_p(inf, &pos);
        }
        if(bits & 0x0020) { // RightIndent
                (void)fmtutil_hlp_get_css_p(inf, &pos);
        }
        if(bits & 0x0040) { // FirstlineIndent
                (void)fmtutil_hlp_get_css_p(inf, &pos);
        }
        // 0x0080 = unused
        if(bits & 0x0100) { // Borderinfo
                goto done; // TODO
        }
        if(bits & 0x0200) { // Tabinfo
                goto done; // TODO
        }
        // 0x0400 = RightAlignedParagraph
        // 0x0800 = CenterAlignedParagraph

        tld->paragraphinfo_pos = pos;
        retval = 1;
done:
        return retval;
}

// linkdata2 = after Phrase/Hall decompression
static void do_topiclink_rectype_1_32(deark *c, lctx *d,
        struct topic_ctx *tctx, struct topiclink_data *tld, dbuf *linkdata2)
{
        i64 pos;
        int in_string = 0;
        int string_count = 0;
        int byte_count = 0;

        if(!d->extract_text) goto done;
        ensure_text_output_file_open(c, d);

        do_topiclink_rectype_32_linkdata1(c, d, tctx, tld);

        // TODO: This is very quick & dirty.
        // The linkdata2 is a collection of NUL-terminated strings. We'd have to
        // interpret the command bytes from linkdata1 to know how to format them.

        pos = 0;
        dbuf_truncate(d->tmpdbuf1, 0); // A place to collect the current output string

        while(1) {
                u8 b;

                if(pos >= linkdata2->len) break;
                b = dbuf_getbyte_p(linkdata2, &pos);
                if(b==0x00) {
                        if(in_string) {
                                emit_slice(c, d, d->tmpdbuf1, 0, d->tmpdbuf1->len);
                                dbuf_truncate(d->tmpdbuf1, 0);
                                emit_raw_sz(c, d, "\n");
                                string_count++;
                                in_string = 0;
                        }
                }
                else {
                        dbuf_writebyte(d->tmpdbuf1, b);
                        byte_count++;
                        in_string = 1;
                }
        }
        if(in_string) {
                emit_slice(c, d, d->tmpdbuf1, 0, d->tmpdbuf1->len);
                dbuf_truncate(d->tmpdbuf1, 0);
                emit_raw_sz(c, d, "\n");
                string_count++;
        }
        de_dbg2(c, "[emitted %d strings, totaling %d bytes]", string_count, byte_count);

done:
        ;
}

// TOPIC header
static void do_topiclink_rectype_2_linkdata2(deark *c, lctx *d,
        struct topic_ctx *tctx, struct topiclink_data *tld, dbuf *linkdata2)
{
        i64 k;
        int bytecount = 0;

        dbuf_truncate(d->tmpdbuf1, 0);
        emit_raw_sz(c, d, "# ");

        for(k=0; k<linkdata2->len; k++) {
                u8 b;

                b = dbuf_getbyte(linkdata2, k);
                if(b==0) break;
                dbuf_writebyte(d->tmpdbuf1, b);
                bytecount++;
        }

        if(bytecount>0) {
                emit_slice(c, d, d->tmpdbuf1, 0, d->tmpdbuf1->len);
        }
        else {
                emit_raw_sz(c, d, "(untitled topic)");
        }

        emit_raw_sz(c, d, " #\n");
}

// topic header and title
static void do_topiclink_rectype_2(deark *c, lctx *d,
        struct topic_ctx *tctx, struct topiclink_data *tld, dbuf *linkdata2)
{
        if(!d->extract_text) goto done;
        ensure_text_output_file_open(c, d);

        do_topiclink_rectype_2_linkdata2(c, d, tctx, tld, linkdata2);
done:
        ;
}

// Returns 1 if we set next_pos_code
static int do_topiclink(deark *c, lctx *d, struct topic_ctx *tctx, i64 pos1, u32 *next_pos_code)
{
        struct topiclink_data *tld = NULL;
        i64 pos = pos1;
        i64 linkdata2_nbytes_avail;
        int retval = 0;
        dbuf *inf = tctx->unc_topicdata;
        char tmpbuf[24];

        tld = de_malloc(c, sizeof(struct topiclink_data));

        tld->blocksize = dbuf_geti32le_p(inf, &pos);
        de_dbg(c, "blocksize: %d", (int)tld->blocksize);
        if((tld->blocksize<21) || (pos1 + tld->blocksize > inf->len)) {
                de_dbg(c, "bad topiclink blocksize");
                goto done;
        }
        tld->datalen2 = dbuf_geti32le_p(inf, &pos);
        de_dbg(c, "datalen2 (after any decompression): %d", (int)tld->datalen2);

        tld->prevblock = (u32)dbuf_getu32le_p(inf, &pos);
        format_topiclink(c, d, tld->prevblock, tmpbuf, sizeof(tmpbuf));
        de_dbg(c, "prevblock: %s", tmpbuf);

        tld->nextblock = (u32)dbuf_getu32le_p(inf, &pos);
        format_topiclink(c, d, tld->nextblock, tmpbuf, sizeof(tmpbuf));
        de_dbg(c, "nextblock: %s", tmpbuf);
        *next_pos_code = (u32)tld->nextblock;
        retval = 1;

        tld->datalen1 = dbuf_geti32le_p(inf, &pos);
        de_dbg(c, "datalen1: %d", (int)tld->datalen1);
        tld->recordtype = dbuf_getbyte_p(inf, &pos);
        de_dbg(c, "record type: %d", (int)tld->recordtype);

        tld->linkdata1_pos = pos1 + 21;
        tld->linkdata1_len = tld->datalen1 - 21;
        de_dbg(c, "linkdata1: pos=[%"I64_FMT"], len=%"I64_FMT, tld->linkdata1_pos, tld->linkdata1_len);

        tld->linkdata2_pos = tld->linkdata1_pos + tld->linkdata1_len;
        linkdata2_nbytes_avail = tld->blocksize - tld->datalen1;

        if(d->uses_old_phrase_compression || d->uses_hall_compression) {
                if(tld->datalen2 > linkdata2_nbytes_avail) {
                        // Phrase/Hall compression used in this topiclink
                        tld->seems_compressed = 1;
                        tld->linkdata2_cmprlen = linkdata2_nbytes_avail;
                        tld->linkdata2_uncmprlen = tld->datalen2;
                }
                else {
                        // Phrase/Hall compression used in this file, but not in this topiclink
                        tld->linkdata2_cmprlen = tld->datalen2;
                        tld->linkdata2_uncmprlen = tld->datalen2;
                }
        }
        else {
                // Phrase/Hall compression not used in this file
                tld->linkdata2_cmprlen = de_min_int(tld->datalen2, linkdata2_nbytes_avail);
                tld->linkdata2_uncmprlen = tld->linkdata2_cmprlen;
        }

        if((tld->linkdata1_pos<pos1) || (tld->linkdata2_pos<pos1) ||
                (tld->linkdata1_len<0) || (tld->linkdata2_cmprlen<0) ||
                (tld->linkdata1_pos + tld->linkdata1_len > pos1+tld->blocksize) ||
                (tld->linkdata2_pos + tld->linkdata2_cmprlen > pos1+tld->blocksize))
        {
                de_dbg(c, "bad linkdata");
                goto done;
        }

        de_dbg(c, "linkdata2: pos=[%"I64_FMT"], cmprlen=%"I64_FMT", uncmprlen=%"I64_FMT,
                tld->linkdata2_pos, tld->linkdata2_cmprlen, tld->linkdata2_uncmprlen);

        // Decompress linkdata2 if necessary
        dbuf_truncate(d->unc_linkdata2_dbuf, 0);
        if(tld->seems_compressed && d->uses_old_phrase_compression) {
                do_phrase_decompression(c, d, inf, tld->linkdata2_pos, tld->linkdata2_cmprlen,
                        d->unc_linkdata2_dbuf, tld->linkdata2_uncmprlen);
        }
        else if(tld->seems_compressed && d->uses_hall_compression) {
                do_hall_decompression(c, d, inf, tld->linkdata2_pos, tld->linkdata2_cmprlen,
                        d->unc_linkdata2_dbuf,tld->linkdata2_uncmprlen);
        }
        else {
                dbuf_copy(inf, tld->linkdata2_pos, tld->linkdata2_cmprlen, d->unc_linkdata2_dbuf);
        }

        switch(tld->recordtype) {
        case 1:
        case 32:
        case 35:
                do_topiclink_rectype_1_32(c, d, tctx, tld, d->unc_linkdata2_dbuf);
                break;
        case 2:
                do_topiclink_rectype_2(c, d, tctx, tld, d->unc_linkdata2_dbuf);
                break;
        default:
                de_warn(c, "Unsupported record type: %d", (int)tld->recordtype);
        }

done:
        de_free(c, tld);
        return retval;
}

static int topicpos_to_abspos(deark *c, lctx *d, struct topic_ctx *tctx, i64 topicpos,
        i64 *pabspos)
{
        i64 blknum, blkoffs;

        if(!d->topic_block_size) return 0;
        blkoffs = topicpos % 16384;
        if(blkoffs<TOPICBLOCKHDRSIZE) return 0;
        blknum = topicpos / 16384;
        if(blknum<0 || blknum>=tctx->num_topic_blocks) return 0;
        *pabspos = tctx->topic_block_info[blknum].pos + (blkoffs-TOPICBLOCKHDRSIZE);
        return 1;
}

static i64 hc30_abspos_plus_offset_to_abspos(deark *c, lctx *d, i64 pos, i64 offset)
{
        i64 blksize = d->topic_block_size-TOPICBLOCKHDRSIZE;
        i64 start_of_curr_block;
        i64 end_of_curr_block;
        i64 n;

        // We're at a position in blocks of size (d->topic_block_size-12). We need to add
        // 'offset', but subtract 12 every time we cross a block boundary.
        start_of_curr_block = (pos/blksize)*blksize;
        end_of_curr_block = start_of_curr_block + blksize;
        if(pos+offset <= end_of_curr_block) {
                return pos + offset;
        }

        n = pos+offset - end_of_curr_block;
        return pos + offset - TOPICBLOCKHDRSIZE*(1+(n / blksize));
}

static int calc_next_topiclink_pos(deark *c, lctx *d, struct topic_ctx *tctx, i64 curpos,
        u32 next_pos_code, i64 *pnextpos)
{
        *pnextpos = 0;

        if(next_pos_code==INVALIDPOS) {
                de_dbg(c, "[stopping TOPIC parsing, end-of-links marker found]");
                return 0;
        }

        if(d->ver_minor<=16) {
                if(next_pos_code < 21) {
                        de_dbg(c, "[stopping TOPIC parsing, no nextblock available]");
                        return 0;
                }
                *pnextpos = hc30_abspos_plus_offset_to_abspos(c, d, curpos, next_pos_code);
        }
        else {
                if(!topicpos_to_abspos(c, d, tctx, next_pos_code, pnextpos)) {
                        de_dbg(c, "[stopping TOPIC parsing, no nextblock available]");
                        return 0;
                }

                if((*pnextpos) <= curpos) {
                        de_dbg(c, "[stopping TOPIC parsing, blocks not in order]");
                        return 0;
                }
        }

        return 1;
}

static void do_topicdata(deark *c, lctx *d, struct topic_ctx *tctx)
{
        i64 pos;
        int saved_indent_level, saved_indent_level2;
        dbuf *inf = tctx->unc_topicdata;

        de_dbg_indent_save(c, &saved_indent_level);

        de_dbg(c, "topic data");

        de_dbg_indent(c, 1);
        if(!inf) {
                goto done;
        }

        de_dbg_indent_save(c, &saved_indent_level2);

        if(tctx->pos_of_first_topiclink==INVALIDPOS || tctx->pos_of_first_topiclink<TOPICBLOCKHDRSIZE) {
                de_warn(c, "Bad first topic link");
                pos = 0;
        }
        else {
                // Maybe we should call topicpos_to_abspos(), etc., but this should be
                // correct since an offset in the first topicblock.
                pos = tctx->pos_of_first_topiclink - TOPICBLOCKHDRSIZE;
        }

        while(1) {
                u32 next_pos_code;
                i64 next_pos = 0;
                int ret;

                if(pos > inf->len) {
                        de_dbg(c, "[stopping TOPIC parsing, exceeded end of data]");
                        break;
                }
                if(pos == inf->len) {
                        de_dbg(c, "[stopping TOPIC parsing, reached end of data]");
                        break;
                }
                if(pos + 21 > inf->len) {
                        de_warn(c, "Error parsing TOPIC, not enough room for another TOPICLINK (%"I64_FMT
                                ", %"I64_FMT")", pos, inf->len);
                        break;
                }

                // TODO: Display as "Blk#:offs"
                de_dbg(c, "topiclink at [%"I64_FMT"]", pos);
                de_dbg_indent(c, 1);
                next_pos_code = 0;
                if(!do_topiclink(c, d, tctx, pos, &next_pos_code)) goto done;
                de_dbg_indent(c, -1);

                ret = calc_next_topiclink_pos(c, d, tctx, pos, next_pos_code, &next_pos);
                if(!ret) break;
                pos = next_pos;
        }

done:
        de_dbg_indent_restore(c, saved_indent_level);
}

static void decompress_topic_block(deark *c, lctx *d, struct topic_ctx *tctx,
        i64 blknum, i64 blk_dpos, i64 blk_dlen,
        dbuf *outf)
{
        struct de_dfilter_in_params dcmpri;
        struct de_dfilter_out_params dcmpro;
        struct de_dfilter_results dres;
        i64 len_before;

        de_dfilter_init_objects(c, &dcmpri, &dcmpro, &dres);

        dcmpri.f = c->infile;
        dcmpri.pos = blk_dpos;
        dcmpri.len = blk_dlen;
        dcmpro.f = outf;
        dcmpro.len_known = 1;
        // TODO: Confirm what happens if a block decompresses to more than 16384-12 bytes.
        dcmpro.expected_len = 16384-TOPICBLOCKHDRSIZE;
        len_before = outf->len;
        fmtutil_hlp_lz77_codectype1(c, &dcmpri, &dcmpro, &dres, NULL);
        de_dbg(c, "decompressed %"I64_FMT" to %"I64_FMT" bytes", blk_dlen,
                outf->len - len_before);
}

static void do_file_TOPIC(deark *c, lctx *d, i64 pos1, i64 len)
{
        i64 pos = pos1;
        int saved_indent_level;
        struct topic_ctx *tctx = NULL;
        i64 blknum;

        de_dbg_indent_save(c, &saved_indent_level);
        tctx = de_malloc(c, sizeof(struct topic_ctx));
        de_dbg(c, "TOPIC at %"I64_FMT", len=%"I64_FMT, pos1, len);
        de_dbg_indent(c, 1);

        if(!d->found_system_file || d->topic_block_size<2048) {
                de_err(c, "SYSTEM file not found");
                goto done;
        }

        if(d->extract_text) {
                tctx->unc_topicdata = dbuf_create_membuf(c, 0, 0);
        }
        tctx->num_topic_blocks = (len + (d->topic_block_size - TOPICBLOCKHDRSIZE)) % d->topic_block_size;
        tctx->topic_block_info = de_mallocarray(c, tctx->num_topic_blocks, sizeof(struct topic_block_info_item));

        tctx->pos_of_first_topiclink = INVALIDPOS;

        // A series of blocks, each with a 12-byte header
        for(blknum=0; blknum<tctx->num_topic_blocks; blknum++) {
                u32 lastlink, firstlink, lastheader;
                i64 blklen;
                i64 blk_dpos;
                i64 blk_dlen;
                char tbuf1[24], tbuf2[24], tbuf3[24];

                blklen = d->topic_block_size;
                if(blklen > (pos1+len)-pos) {
                        blklen = (pos1+len)-pos;
                }
                if(blklen<TOPICBLOCKHDRSIZE) break;
                blk_dpos = pos+TOPICBLOCKHDRSIZE;
                blk_dlen = blklen-TOPICBLOCKHDRSIZE;

                de_dbg(c, "TOPIC block #%d at %d, dpos=%d, dlen=%d", (int)blknum, (int)pos,
                        (int)blk_dpos, (int)blk_dlen);
                de_dbg_indent(c, 1);
                lastlink = (u32)de_getu32le(pos);
                firstlink = (u32)de_getu32le(pos+4);
                lastheader = (u32)de_getu32le(pos+8);
                format_topiclink(c, d, lastlink, tbuf1, sizeof(tbuf1));
                format_topiclink(c, d, firstlink, tbuf2, sizeof(tbuf2));
                format_topiclink(c, d, lastheader, tbuf3, sizeof(tbuf3));
                de_dbg(c, "LastLink=%s, FirstLink=%s, LastHeader=%s",
                        tbuf1, tbuf2, tbuf3);
                if(tctx->pos_of_first_topiclink==INVALIDPOS && firstlink!=INVALIDPOS) {
                        tctx->pos_of_first_topiclink = firstlink;
                }

                if(d->extract_text && tctx->unc_topicdata) {
                        // Record the position for later reference.
                        tctx->topic_block_info[blknum].pos = tctx->unc_topicdata->len;

                        if(d->is_lz77_compressed) {
                                decompress_topic_block(c, d, tctx, blknum, blk_dpos, blk_dlen, tctx->unc_topicdata);
                        }
                        else {
                                dbuf_copy(c->infile, blk_dpos, blk_dlen, tctx->unc_topicdata);
                        }

                        tctx->topic_block_info[blknum].len = tctx->unc_topicdata->len - tctx->topic_block_info[blknum].pos;

                        de_dbg2(c, "[current decompressed size: %"I64_FMT"]", tctx->unc_topicdata->len);
                }

                de_dbg_indent(c, -1);
                pos += blklen;
        }

        if(tctx->unc_topicdata && tctx->unc_topicdata->len>0) {
                do_topicdata(c, d, tctx);
        }

done:
        if(tctx) {
                dbuf_close(tctx->unc_topicdata);
                de_free(c, tctx->topic_block_info);
                de_free(c, tctx);
        }
        de_dbg_indent_restore(c, saved_indent_level);

}
static void do_index_page(deark *c, lctx *d, i64 pos1, i64 *prev_page)
{
        *prev_page = de_geti16le(pos1+4);
        de_dbg(c, "PreviousPage: %d", (int)*prev_page);
}

static int de_is_digit(char x)
{
        return (x>='0' && x<='9');
}

static enum hlp_filetype filename_to_filetype(deark *c, lctx *d, const char *fn)
{
        const char *ext;
        size_t extlen;

        if(fn[0]=='|') {
                if(!de_strcmp(fn, "|TOPIC")) return FILETYPE_TOPIC;
                if(!de_strcmp(fn, "|SYSTEM")) return FILETYPE_SYSTEM;
                if(!de_strncmp(fn, "|bm", 3) && de_is_digit(fn[3])) return FILETYPE_SHG;
                if(!de_strcmp(fn, "|Phrases")) return FILETYPE_PHRASES;
                if(!de_strcmp(fn, "|PhrIndex")) return FILETYPE_PHRINDEX;
                if(!de_strcmp(fn, "|PhrImage")) return FILETYPE_PHRIMAGE;
                return FILETYPE_OTHERSPECIAL;
        }

        ext = de_get_sz_ext(fn);
        extlen = de_strlen(ext);

        // Some SHG streams' names don't start with "|". Assume it is SHG if it
        // starts with "bm" and a digit, and doesn't have a ".".
        if(extlen==0) {
                if(!de_strncmp(fn, "bm", 2) && de_is_digit(fn[2])) return FILETYPE_SHG;
        }

        // Not sure how bold to be here. Should we extract every file that we can't
        // identify? Or maybe only those that have a filename extension?
        return FILETYPE_EXTRACTABLE;
}

static void do_leaf_page(deark *c, lctx *d, i64 pos1, i64 *pnext_page)
{
        i64 n;
        i64 pos = pos1;
        i64 foundpos;
        i64 num_entries;
        i64 file_offset;
        i64 k;
        struct de_stringreaderdata *fn_srd = NULL;
        enum hlp_filetype file_type;
        int saved_indent_level;

        de_dbg_indent_save(c, &saved_indent_level);
        n = de_getu16le_p(&pos); // "Unused"
        de_dbg(c, "free bytes at end of this page: %d", (int)n);

        num_entries = de_geti16le_p(&pos);
        de_dbg(c, "NEntries: %d", (int)num_entries);

        n = de_geti16le_p(&pos);
        de_dbg(c, "PreviousPage: %d", (int)n);

        n = de_geti16le_p(&pos);
        de_dbg(c, "NextPage: %d", (int)n);
        if(pnext_page) *pnext_page = n;

        for(k=0; k<num_entries; k++) {
                int pass_for_this_file;

                de_dbg(c, "entry[%d]", (int)k);
                de_dbg_indent(c, 1);

                if(!dbuf_search_byte(c->infile, 0x00, pos, 260, &foundpos)) {
                        de_err(c, "Malformed leaf page at %d", (int)pos1);
                        goto done;
                }

                if(fn_srd) {
                        de_destroy_stringreaderdata(c, fn_srd);
                }
                fn_srd = dbuf_read_string(c->infile, pos, foundpos-pos, foundpos-pos, 0, d->input_encoding);
                de_dbg(c, "FileName: \"%s\"", ucstring_getpsz_d(fn_srd->str));
                pos = foundpos + 1;

                file_offset = de_geti32le_p(&pos);
                de_dbg(c, "FileOffset: %d", (int)file_offset);

                file_type = filename_to_filetype(c, d, fn_srd->sz);

                switch(file_type) {
                case FILETYPE_SYSTEM:
                        d->found_system_file = 1;
                        d->offset_of_system_file = file_offset;
                        pass_for_this_file = 1;
                        break;
                case FILETYPE_TOPIC:
                        d->found_TOPIC_file = 1;
                        d->offset_of_TOPIC = file_offset;
                        pass_for_this_file = 1;
                        break;
                case FILETYPE_PHRASES:
                        d->found_Phrases_file = 1;
                        d->offset_of_Phrases = file_offset;
                        pass_for_this_file = 1;
                        break;
                case FILETYPE_PHRINDEX:
                        d->found_PhrIndex_file = 1;
                        d->offset_of_PhrIndex = file_offset;
                        pass_for_this_file = 1;
                        break;
                case FILETYPE_PHRIMAGE:
                        d->found_PhrImage_file = 1;
                        d->offset_of_PhrImage = file_offset;
                        pass_for_this_file = 1;
                        break;
                default:
                        pass_for_this_file = 2;
                }

                if(d->pass==2 && d->extract_raw_streams) {
                        do_file(c, d, file_offset, file_type, 1, fn_srd);
                }
                else if(d->pass==2 && pass_for_this_file==2) {
                        do_file(c, d, file_offset, file_type, 0, fn_srd);
                }

                de_dbg_indent(c, -1);
        }

done:
        de_destroy_stringreaderdata(c, fn_srd);
        de_dbg_indent_restore(c, saved_indent_level);
}

// Sets d->bpt.first_leaf_page
static int find_first_leaf_page(deark *c, lctx *d)
{
        i64 curr_page;
        i64 curr_level;
        int saved_indent_level;
        int retval = 0;

        de_dbg_indent_save(c, &saved_indent_level);
        curr_page = d->bpt.root_page;
        curr_level = d->bpt.num_levels;

        de_dbg(c, "looking for first leaf page");
        de_dbg_indent(c, 1);

        while(curr_level>1) {
                i64 prev_page;
                i64 page_pos;

                if(curr_page<0) goto done;
                page_pos = d->bpt.pagesdata_pos + curr_page*d->bpt.pagesize;

                de_dbg(c, "page %d is an index page, level=%d", (int)curr_page, (int)curr_level);

                prev_page = -1;
                de_dbg_indent(c, 1);
                do_index_page(c, d, page_pos, &prev_page);
                de_dbg_indent(c, -1);

                curr_page = prev_page;
                curr_level--;
        }

        de_dbg(c, "page %d is the first leaf page", (int)curr_page);
        d->bpt.first_leaf_page = curr_page;

        retval = 1;

done:
        de_dbg_indent_restore(c, saved_indent_level);
        return retval;
}

static void sanitize_phrase_info(deark *c, lctx *d)
{
        unsigned int k;

        if(!d->phrases_data) {
                d->num_phrases = 0;
                return;
        }

        for(k=0; k<d->num_phrases; k++) {
                if((i64)d->phrase_info[k].pos + (i64)d->phrase_info[k].len > d->phrases_data->len) {
                        d->phrase_info[k].pos = 0;
                        d->phrase_info[k].len = 0;
                }
        }
}

static void do_after_pass_1(deark *c, lctx *d)
{
        // Read the SYSTEM file first -- lots of other things depend on it.
        if(d->found_system_file) {
                do_file(c, d, d->offset_of_system_file, FILETYPE_SYSTEM, 0, NULL);
        }

        if(d->found_Phrases_file) {
                d->uses_old_phrase_compression = 1;
        }
        else if(d->found_PhrIndex_file && d->found_PhrImage_file) {
                d->uses_hall_compression = 1;
        }

        if(d->input_encoding==DE_ENCODING_UNKNOWN || d->input_encoding==DE_ENCODING_ASCII) {
                d->output_is_utf8 = 0;
        }
        else {
                d->output_is_utf8 = 1;
        }

        // Read other special files, in a suitable order.

        if(d->found_Phrases_file && d->uses_old_phrase_compression) {
                do_file(c, d, d->offset_of_Phrases, FILETYPE_PHRASES, 0, NULL);
        }

        if(d->found_PhrIndex_file && d->uses_hall_compression) {
                do_file(c, d, d->offset_of_PhrIndex, FILETYPE_PHRINDEX, 0, NULL);
        }
        if(d->found_PhrImage_file && d->uses_hall_compression) {
                do_file(c, d, d->offset_of_PhrImage, FILETYPE_PHRIMAGE, 0, NULL);
        }
        sanitize_phrase_info(c, d);

        if(d->found_TOPIC_file) {
                do_file(c, d, d->offset_of_TOPIC, FILETYPE_TOPIC, 0, NULL);
        }
}

// This function is only for the "internal directory" tree.
// There are other data objects in HLP files that use the same kind of data
// structure. If we ever want to parse them, this function will have to be
// genericized.
static void do_bplustree(deark *c, lctx *d, i64 pos1, i64 len,
        int is_internaldir)
{
        i64 pos = pos1;
        i64 n;
        int saved_indent_level;
        u8 *page_seen = NULL;
        struct de_stringreaderdata *structure = NULL;

        if(!is_internaldir) return;

        de_dbg_indent_save(c, &saved_indent_level);

        n = de_getu16le_p(&pos);
        if(n != 0x293b) {
                de_err(c, "Expected B+ tree structure at %d not found", (int)pos1);
                goto done;
        }

        //de_dbg(c, "B+ tree at %d", (int)pos1);
        de_dbg_indent(c, 1);

        d->bpt.flags = (unsigned int)de_getu16le_p(&pos);
        de_dbg(c, "Btree flags: 0x%04x", d->bpt.flags);

        d->bpt.pagesize = de_getu16le_p(&pos);
        de_dbg(c, "PageSize: %d", (int)d->bpt.pagesize);

        // TODO: Understand the Structure field
        structure = dbuf_read_string(c->infile, pos, 16, 16, DE_CONVFLAG_STOP_AT_NUL,
                DE_ENCODING_ASCII);
        de_dbg(c, "Structure: \"%s\"", ucstring_getpsz_d(structure->str));
        de_destroy_stringreaderdata(c, structure);
        structure = NULL;
        pos += 16;

        pos += 2; // MustBeZero
        pos += 2; // PageSplits

        d->bpt.root_page = de_geti16le_p(&pos);
        de_dbg(c, "RootPage: %d", (int)d->bpt.root_page);

        pos += 2; // MustBeNegOne

        d->bpt.num_pages = de_geti16le_p(&pos);
        de_dbg(c, "TotalPages: %d", (int)d->bpt.num_pages);

        d->bpt.num_levels = de_geti16le_p(&pos);
        de_dbg(c, "NLevels: %d", (int)d->bpt.num_levels);
        if(is_internaldir) d->internal_dir_num_levels = d->bpt.num_levels;

        d->bpt.num_entries = de_geti32le_p(&pos);
        de_dbg(c, "TotalBtreeEntries: %d", (int)d->bpt.num_entries);

        d->bpt.pagesdata_pos = pos;
        de_dbg(c, "num pages: %d, %d bytes each, at %d (total size=%d)",
                (int)d->bpt.num_pages, (int)d->bpt.pagesize, (int)d->bpt.pagesdata_pos,
                (int)(d->bpt.num_pages * d->bpt.pagesize));

        if(!find_first_leaf_page(c, d)) goto done;

        page_seen = de_malloc(c, d->bpt.num_pages); // For loop detection

        for(d->pass=1; d->pass<=2; d->pass++) {
                i64 curr_page;

                de_zeromem(page_seen, (size_t)d->bpt.num_pages);

                de_dbg(c, "pass %d", d->pass);
                de_dbg_indent(c, 1);

                curr_page = d->bpt.first_leaf_page;

                while(1) {
                        i64 page_pos;
                        i64 next_page;

                        if(curr_page<0) break;
                        if(curr_page>d->bpt.num_pages) goto done;

                        if(d->pass==1 && page_seen[curr_page]) {
                                de_err(c, "Page loop detected");
                                goto done;
                        }
                        page_seen[curr_page] = 1;

                        page_pos = d->bpt.pagesdata_pos + curr_page*d->bpt.pagesize;

                        de_dbg(c, "page[%d] at %d (leaf page)", (int)curr_page, (int)page_pos);

                        next_page = -1;
                        de_dbg_indent(c, 1);
                        do_leaf_page(c, d, page_pos, &next_page);
                        de_dbg_indent(c, -1);

                        curr_page = next_page;
                }

                de_dbg_indent(c, -1);

                if(d->pass==1) {
                        de_dbg(c, "reading items after pass 1");
                        de_dbg_indent(c, 1);
                        do_after_pass_1(c, d);
                        de_dbg_indent(c, -1);
                }
        }

done:
        de_free(c, page_seen);
        if(structure) de_destroy_stringreaderdata(c, structure);
        de_dbg_indent_restore(c, saved_indent_level);
}

static void do_file_INTERNALDIR(deark *c, lctx *d, i64 pos1, i64 len)
{
        de_dbg(c, "internal dir data at %d", (int)pos1);
        do_bplustree(c, d, pos1, len, 1);
}

static void dump_phrase_offset_table(deark *c, lctx *d)
{
        unsigned int k;

        for(k=0; k<d->num_phrases; k++) {
                de_dbg2(c, "phrase[%u]: offs=%u, len=%u", k, d->phrase_info[k].pos,
                        d->phrase_info[k].len);
        }
}

static void decompress_Phrases(deark *c, lctx *d, i64 pos, i64 cmpr_len, i64 uncmpr_len)
{
        struct de_dfilter_in_params dcmpri;
        struct de_dfilter_out_params dcmpro;
        struct de_dfilter_results dres;

        de_dfilter_init_objects(c, &dcmpri, &dcmpro, &dres);
        dcmpri.f = c->infile;
        dcmpri.pos = pos;
        dcmpri.len = cmpr_len;
        dcmpro.f = d->phrases_data;
        dcmpro.len_known = 1;
        dcmpro.expected_len = uncmpr_len;
        fmtutil_hlp_lz77_codectype1(c, &dcmpri, &dcmpro, &dres, NULL);
        if(dres.errcode || (d->phrases_data->len!=uncmpr_len)) {
                de_warn(c, "Phrases decompression may have failed");
        }
}

static void do_file_Phrases(deark *c, lctx *d, i64 pos1, i64 len)
{
        i64 pos;
        i64 s0, s1, s2;
        i64 phrase_data_pos;
        i64 phrase_data_cmpr_len;
        i64 phrase_data_uncmpr_len = 0;
        i64 phrase_offset_table_pos;
        i64 phrase_offset_table_len;
        unsigned int k;
        int is_MVB_format = 0;
        int is_compressed = 0;
        int saved_indent_level;

        de_dbg_indent_save(c, &saved_indent_level);
        if(!d->extract_text) goto done;

        de_dbg(c, "Phrases data at %"I64_FMT", len=%"I64_FMT, pos1, len);
        de_dbg_indent(c, 1);
        if(len<6) goto done;

        s0 = de_getu16le(pos1);
        s1 = de_getu16le(pos1+2);
        s2 = de_getu16le(pos1+4);

        if(s0==0x0800 && s1!=0x0100 && s2==0x0100) {
                is_MVB_format = 1;
        }
        else if(s1==0x0100) {
                ;
        }
        else {
                de_err(c, "Unknown Phrases format");
                goto done;
        }
        de_dbg(c, "MVB format: %d", is_MVB_format);
        if(is_MVB_format) {
                de_err(c, "Unsupported Phrases format");
                goto done;
        }

        d->num_phrases = (unsigned int)s0;
        de_dbg(c, "num phrases: %u", d->num_phrases);
        pos = pos1+4;

        if(d->ver_minor>16) {
                is_compressed = 1;
        }
        de_dbg(c, "Phrases are lzw-compressed: %d", is_compressed);

        if(is_compressed) {
                phrase_data_uncmpr_len = de_getu32le_p(&pos);
                de_dbg(c, "decompressed len (reported): %"I64_FMT, phrase_data_uncmpr_len);
        }

        // Phrase offsets are measured from the start of the offset table.
        phrase_offset_table_pos = pos;
        phrase_offset_table_len = ((i64)d->num_phrases+1)*2;
        de_dbg(c, "offset table at %"I64_FMT", len=%"I64_FMT, phrase_offset_table_pos,
                phrase_offset_table_len);

        phrase_data_pos = phrase_offset_table_pos + phrase_offset_table_len;
        phrase_data_cmpr_len = pos1+len - phrase_data_pos; // (before any decompression)
        if(phrase_data_cmpr_len<0) goto done;
        if(!is_compressed) {
                phrase_data_uncmpr_len = phrase_data_cmpr_len;
        }

        d->phrase_info = de_mallocarray(c, (i64)d->num_phrases, sizeof(struct phrase_item));
        for(k=0; k<d->num_phrases+1; k++) {
                u32 offs;

                offs = (u32)de_getu16le_p(&pos);
                offs -= (u32)phrase_offset_table_len;

                if(k<d->num_phrases) {
                        d->phrase_info[k].pos = offs;
                }
                if(k>=1) {
                        d->phrase_info[k-1].len = offs - d->phrase_info[k-1].pos;
                }
        }
        if(c->debug_level>=2) {
                dump_phrase_offset_table(c, d);
        }

        de_dbg(c, "phrase data at %"I64_FMT", len=%"I64_FMT, phrase_data_pos, phrase_data_cmpr_len);

        if(is_compressed) {
                decompress_Phrases(c, d, phrase_data_pos, phrase_data_cmpr_len, phrase_data_uncmpr_len);
        }
        else {
                dbuf_copy(c->infile, phrase_data_pos, phrase_data_cmpr_len, d->phrases_data);
        }

        d->valid_Phrases_file = 1;

done:
        de_dbg_indent_restore(c, saved_indent_level);
}

static void phrdecompress(deark *c, lctx *d, i64 pos1, i64 len, unsigned int BitCount)
{
        unsigned int n;
        unsigned int i;
        struct de_bitreader bitrd;

        de_zeromem(&bitrd, sizeof(struct de_bitreader));
        bitrd.f = c->infile;
        bitrd.curpos = pos1;
        bitrd.endpos = pos1 + len;
        bitrd.bbll.is_lsb = 1;

        d->phrase_info[0].pos = 0;

        for(i=0; i<d->num_phrases; i++) {
                unsigned int num1bits = 0;

                while(de_bitreader_getbits(&bitrd, 1)) {
                        if(bitrd.eof_flag) goto done;
                        num1bits++;
                }
                n = num1bits<<BitCount;
                n += (UI)de_bitreader_getbits(&bitrd, BitCount) + 1;
                if(bitrd.eof_flag) goto done;

                d->phrase_info[i].len = n;
                if(i+1<d->num_phrases) {
                        d->phrase_info[i+1].pos = d->phrase_info[i].pos+n;
                }
        }

done:
        if(c->debug_level>=2) {
                dump_phrase_offset_table(c, d);
        }
}

static void do_file_PhrIndex(deark *c, lctx *d, i64 pos1, i64 len)
{
        i64 pos = pos1;
        i64 cmprsize;
        i64 n;
        unsigned int bits;
        unsigned int bitcount;
        int saved_indent_level;

        de_dbg_indent_save(c, &saved_indent_level);
        if(len<30) goto done;
        n = de_getu32le_p(&pos);
        if(n!=1) goto done;
        d->num_phrases = (unsigned int)de_getu32le_p(&pos);
        de_dbg(c, "num phrases: %u", d->num_phrases);
        d->phrase_info = de_mallocarray(c, (i64)d->num_phrases, sizeof(struct phrase_item));

        cmprsize = de_getu32le_p(&pos);
        de_dbg(c, "index cmpr size: %"I64_FMT, cmprsize);
        d->PhrImageUncSize = de_getu32le_p(&pos);
        de_dbg(c, "PhrImage uncmpr size: %"I64_FMT, d->PhrImageUncSize);
        d->PhrImageCmprSize = de_getu32le_p(&pos);
        de_dbg(c, "PhrImage cmpr size: %"I64_FMT, d->PhrImageCmprSize);
        pos += 4;
        bits = (unsigned int)de_getu16le_p(&pos);
        de_dbg(c, "bits: 0x%04x", bits);
        de_dbg_indent(c, 1);
        bitcount = bits & 0xf;
        de_dbg(c, "bit count: %u", bitcount);
        de_dbg_indent(c, -1);
        pos += 2;

        de_dbg(c, "avail size: %d", (int)(pos1+len-pos));
        phrdecompress(c, d, pos, pos1+len-pos, bitcount);
done:
        de_dbg_indent_restore(c, saved_indent_level);
}

static void do_file_PhrImage(deark *c, lctx *d, i64 pos1, i64 len)
{
        de_dbg(c, "PhrImage data at %"I64_FMT", len=%"I64_FMT, pos1, len);
        if(len < d->PhrImageCmprSize) {
                return;
        }

        if(d->PhrImageCmprSize == d->PhrImageUncSize) {
                dbuf_copy(c->infile, pos1, d->PhrImageCmprSize, d->phrases_data);
        }
        else {
                decompress_Phrases(c, d, pos1, d->PhrImageCmprSize, d->PhrImageUncSize);
                de_dbg(c, "decompressed to %"I64_FMT" bytes", d->phrases_data->len);
        }
}

static const char* file_type_to_type_name(enum hlp_filetype file_fmt)
{
        const char *name = "unspecified";
        switch(file_fmt) {
        case FILETYPE_SYSTEM: name="system"; break;
        case FILETYPE_TOPIC: name="topic"; break;
        case FILETYPE_SHG: name="SHG/MRB"; break;
        case FILETYPE_INTERNALDIR: name="directory"; break;
        case FILETYPE_PHRASES: name="Phrases"; break;
        case FILETYPE_PHRINDEX: name="PhrIndex"; break;
        case FILETYPE_PHRIMAGE: name="PhrImage"; break;
        case FILETYPE_OTHERSPECIAL: name="other special stream"; break;
        case FILETYPE_EXTRACTABLE: name="other extractable file"; break;
        default: ;
        }
        return name;
}

static void do_file(deark *c, lctx *d, i64 pos1, enum hlp_filetype file_fmt, int force_extract,
        struct de_stringreaderdata *fn)
{
        i64 reserved_space;
        i64 used_space;
        i64 pos = pos1;
        unsigned int fileflags;

        de_dbg(c, "file at %d, type=%s", (int)pos1, file_type_to_type_name(file_fmt));
        de_dbg_indent(c, 1);

        // FILEHEADER
        reserved_space = de_getu32le_p(&pos);
        de_dbg(c, "ReservedSpace: %d", (int)reserved_space);

        used_space = de_getu32le_p(&pos);
        de_dbg(c, "UsedSpace: %d", (int)used_space);

        fileflags = (unsigned int)de_getbyte_p(&pos);
        de_dbg(c, "FileFlags: 0x%02x", fileflags);

        if(pos+used_space > c->infile->len) {
                de_err(c, "Bad file size");
                goto done;
        }

        if(force_extract) {
                do_extract_raw_file(c, d, pos, used_space, fn);
                goto done;
        }

        switch(file_fmt) {
        case FILETYPE_INTERNALDIR:
                do_file_INTERNALDIR(c, d, pos, used_space);
                break;
        case FILETYPE_TOPIC:
                do_file_TOPIC(c, d, pos, used_space);
                break;
        case FILETYPE_PHRASES:
                do_file_Phrases(c, d, pos, used_space);
                break;
        case FILETYPE_PHRINDEX:
                do_file_PhrIndex(c, d, pos, used_space);
                break;
        case FILETYPE_PHRIMAGE:
                do_file_PhrImage(c, d, pos, used_space);
                break;
        case FILETYPE_SYSTEM:
                do_file_SYSTEM(c, d, pos, used_space);
                break;
        case FILETYPE_SHG:
                d->has_shg = 1;
                do_file_SHG(c, d, pos, used_space);
                break;
        case FILETYPE_EXTRACTABLE:
                do_extract_raw_file(c, d, pos, used_space, fn);
                break;
        default: ;
        }

done:
        de_dbg_indent(c, -1);
}

static void do_header(deark *c, lctx *d, i64 pos)
{
        i64 n;

        de_dbg(c, "header at %d", (int)pos);
        de_dbg_indent(c, 1);

        d->internal_dir_FILEHEADER_offs = de_geti32le(4);
        de_dbg(c, "internal dir FILEHEADER pos: %d", (int)d->internal_dir_FILEHEADER_offs);

        n = de_geti32le(8);
        de_dbg(c, "FREEHEADER pos: %d", (int)n);

        n = de_geti32le(12);
        de_dbg(c, "reported file size: %d", (int)n);

        de_dbg_indent(c, -1);
}

static void de_run_hlp(deark *c, de_module_params *mparams)
{
        lctx *d = NULL;
        i64 pos;

        d = de_malloc(c, sizeof(lctx));

        d->input_encoding = de_get_input_encoding(c, NULL, DE_ENCODING_WINDOWS1252);
        d->extract_text = de_get_ext_option_bool(c, "hlp:extracttext",
                ((c->extract_level>=2)?1:0));
        d->extract_raw_streams = (u8)de_get_ext_option_bool(c, "hlp:extractstreams", 0);
        d->tmpdbuf1 = dbuf_create_membuf(c, 0, 0);
        d->unc_linkdata2_dbuf = dbuf_create_membuf(c, 0, 0);
        d->tmpucstring1 = ucstring_create(c);
        d->phrases_data = dbuf_create_membuf(c, 0, 0);

        pos = 0;
        do_header(c, d, pos);

        do_file(c, d, d->internal_dir_FILEHEADER_offs, FILETYPE_INTERNALDIR, 0, NULL);

        de_dbg(c, "summary: v%d.%d %s%s%s blksize=%d levels=%d%s%s%s",
                d->ver_major, d->ver_minor,
                d->is_lz77_compressed?"lz77":"no_lz77",
                d->uses_old_phrase_compression?" phrase_compression":"",
                d->uses_hall_compression?" Hall_compression":"",
                (int)d->topic_block_size,
                (int)d->internal_dir_num_levels,
                d->has_shg?" has-shg":"",
                d->has_ico?" has-ico":"",
                d->has_bmp?" has-bmp":"");

        if(d) {
                dbuf_close(d->tmpdbuf1);
                dbuf_close(d->unc_linkdata2_dbuf);
                dbuf_close(d->phrases_data);
                ucstring_destroy(d->tmpucstring1);
                ucstring_destroy(d->help_file_title);
                ucstring_destroy(d->help_file_copyright);
                dbuf_close(d->outf_text);
                de_free(c, d->phrase_info);
                de_free(c, d);
        }
}

static int de_identify_hlp(deark *c)
{
        if(!dbuf_memcmp(c->infile, 0, "\x3f\x5f\x03\x00", 4))
                return 100;
        return 0;
}

static void de_help_hlp(deark *c)
{
        de_msg(c, "-opt hlp:extracttext : Write the text (unformatted) to a file");
        de_msg(c, "-opt hlp:extractstreams : Extract raw files, instead of decoding");
}

void de_module_hlp(deark *c, struct deark_module_info *mi)
{
        mi->id = "hlp";
        mi->desc = "HLP";
        mi->run_fn = de_run_hlp;
        mi->identify_fn = de_identify_hlp;
        mi->help_fn = de_help_hlp;
}