summaryrefslogtreecommitdiff
path: root/src/markdown/md4c-html.c
blob: d604aecb0460c2260be0d2c3572f2fb930537ab6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
/*
 * MD4C: Markdown parser for C
 * (http://github.com/mity/md4c)
 *
 * Copyright (c) 2016-2019 Martin Mitas
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <stdio.h>
#include <string.h>

#include "md4c-html.h"
#include "entity.h"


#if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 199409L
    /* C89/90 or old compilers in general may not understand "inline". */
    #if defined __GNUC__
        #define inline __inline__
    #elif defined _MSC_VER
        #define inline __inline
    #else
        #define inline
    #endif
#endif

#ifdef _WIN32
    #define snprintf _snprintf
#endif



typedef struct MD_HTML_tag MD_HTML;
struct MD_HTML_tag {
    void (*process_output)(const MD_CHAR*, MD_SIZE, void*);
    void* userdata;
    unsigned flags;
    int image_nesting_level;
    char escape_map[256];
};

#define NEED_HTML_ESC_FLAG   0x1
#define NEED_URL_ESC_FLAG    0x2


/*****************************************
 ***  HTML rendering helper functions  ***
 *****************************************/

#define ISDIGIT(ch)     ('0' <= (ch) && (ch) <= '9')
#define ISLOWER(ch)     ('a' <= (ch) && (ch) <= 'z')
#define ISUPPER(ch)     ('A' <= (ch) && (ch) <= 'Z')
#define ISALNUM(ch)     (ISLOWER(ch) || ISUPPER(ch) || ISDIGIT(ch))


static inline void
render_verbatim(MD_HTML* r, const MD_CHAR* text, MD_SIZE size)
{
    r->process_output(text, size, r->userdata);
}

/* Keep this as a macro. Most compiler should then be smart enough to replace
 * the strlen() call with a compile-time constant if the string is a C literal. */
#define RENDER_VERBATIM(r, verbatim)                                    \
        render_verbatim((r), (verbatim), (MD_SIZE) (strlen(verbatim)))


static void
render_html_escaped(MD_HTML* r, const MD_CHAR* data, MD_SIZE size)
{
    MD_OFFSET beg = 0;
    MD_OFFSET off = 0;

    /* Some characters need to be escaped in normal HTML text. */
    #define NEED_HTML_ESC(ch)   (r->escape_map[(unsigned char)(ch)] & NEED_HTML_ESC_FLAG)

    while(1) {
        /* Optimization: Use some loop unrolling. */
        while(off + 3 < size  &&  !NEED_HTML_ESC(data[off+0])  &&  !NEED_HTML_ESC(data[off+1])
                              &&  !NEED_HTML_ESC(data[off+2])  &&  !NEED_HTML_ESC(data[off+3]))
            off += 4;
        while(off < size  &&  !NEED_HTML_ESC(data[off]))
            off++;

        if(off > beg)
            render_verbatim(r, data + beg, off - beg);

        if(off < size) {
            switch(data[off]) {
                case '&':   RENDER_VERBATIM(r, "&amp;"); break;
                case '<':   RENDER_VERBATIM(r, "&lt;"); break;
                case '>':   RENDER_VERBATIM(r, "&gt;"); break;
                case '"':   RENDER_VERBATIM(r, "&quot;"); break;
            }
            off++;
        } else {
            break;
        }
        beg = off;
    }
}

static void
render_url_escaped(MD_HTML* r, const MD_CHAR* data, MD_SIZE size)
{
    static const MD_CHAR hex_chars[] = "0123456789ABCDEF";
    MD_OFFSET beg = 0;
    MD_OFFSET off = 0;

    /* Some characters need to be escaped in URL attributes. */
    #define NEED_URL_ESC(ch)    (r->escape_map[(unsigned char)(ch)] & NEED_URL_ESC_FLAG)

    while(1) {
        while(off < size  &&  !NEED_URL_ESC(data[off]))
            off++;
        if(off > beg)
            render_verbatim(r, data + beg, off - beg);

        if(off < size) {
            char hex[3];

            switch(data[off]) {
                case '&':   RENDER_VERBATIM(r, "&amp;"); break;
                default:
                    hex[0] = '%';
                    hex[1] = hex_chars[((unsigned)data[off] >> 4) & 0xf];
                    hex[2] = hex_chars[((unsigned)data[off] >> 0) & 0xf];
                    render_verbatim(r, hex, 3);
                    break;
            }
            off++;
        } else {
            break;
        }

        beg = off;
    }
}

static unsigned
hex_val(char ch)
{
    if('0' <= ch && ch <= '9')
        return ch - '0';
    if('A' <= ch && ch <= 'Z')
        return ch - 'A' + 10;
    else
        return ch - 'a' + 10;
}

static void
render_utf8_codepoint(MD_HTML* r, unsigned codepoint,
                      void (*fn_append)(MD_HTML*, const MD_CHAR*, MD_SIZE))
{
    static const MD_CHAR utf8_replacement_char[] = { 0xef, 0xbf, 0xbd };

    unsigned char utf8[4];
    size_t n;

    if(codepoint <= 0x7f) {
        n = 1;
        utf8[0] = codepoint;
    } else if(codepoint <= 0x7ff) {
        n = 2;
        utf8[0] = 0xc0 | ((codepoint >>  6) & 0x1f);
        utf8[1] = 0x80 + ((codepoint >>  0) & 0x3f);
    } else if(codepoint <= 0xffff) {
        n = 3;
        utf8[0] = 0xe0 | ((codepoint >> 12) & 0xf);
        utf8[1] = 0x80 + ((codepoint >>  6) & 0x3f);
        utf8[2] = 0x80 + ((codepoint >>  0) & 0x3f);
    } else {
        n = 4;
        utf8[0] = 0xf0 | ((codepoint >> 18) & 0x7);
        utf8[1] = 0x80 + ((codepoint >> 12) & 0x3f);
        utf8[2] = 0x80 + ((codepoint >>  6) & 0x3f);
        utf8[3] = 0x80 + ((codepoint >>  0) & 0x3f);
    }

    if(0 < codepoint  &&  codepoint <= 0x10ffff)
        fn_append(r, (char*)utf8, (MD_SIZE)n);
    else
        fn_append(r, utf8_replacement_char, 3);
}

/* Translate entity to its UTF-8 equivalent, or output the verbatim one
 * if such entity is unknown (or if the translation is disabled). */
static void
render_entity(MD_HTML* r, const MD_CHAR* text, MD_SIZE size,
              void (*fn_append)(MD_HTML*, const MD_CHAR*, MD_SIZE))
{
    if(r->flags & MD_HTML_FLAG_VERBATIM_ENTITIES) {
        render_verbatim(r, text, size);
        return;
    }

    /* We assume UTF-8 output is what is desired. */
    if(size > 3 && text[1] == '#') {
        unsigned codepoint = 0;

        if(text[2] == 'x' || text[2] == 'X') {
            /* Hexadecimal entity (e.g. "&#x1234abcd;")). */
            MD_SIZE i;
            for(i = 3; i < size-1; i++)
                codepoint = 16 * codepoint + hex_val(text[i]);
        } else {
            /* Decimal entity (e.g. "&1234;") */
            MD_SIZE i;
            for(i = 2; i < size-1; i++)
                codepoint = 10 * codepoint + (text[i] - '0');
        }

        render_utf8_codepoint(r, codepoint, fn_append);
        return;
    } else {
        /* Named entity (e.g. "&nbsp;"). */
        const struct entity* ent;

        ent = entity_lookup(text, size);
        if(ent != NULL) {
            render_utf8_codepoint(r, ent->codepoints[0], fn_append);
            if(ent->codepoints[1])
                render_utf8_codepoint(r, ent->codepoints[1], fn_append);
            return;
        }
    }

    fn_append(r, text, size);
}

static void
render_attribute(MD_HTML* r, const MD_ATTRIBUTE* attr,
                 void (*fn_append)(MD_HTML*, const MD_CHAR*, MD_SIZE))
{
    int i;

    for(i = 0; attr->substr_offsets[i] < attr->size; i++) {
        MD_TEXTTYPE type = attr->substr_types[i];
        MD_OFFSET off = attr->substr_offsets[i];
        MD_SIZE size = attr->substr_offsets[i+1] - off;
        const MD_CHAR* text = attr->text + off;

        switch(type) {
            case MD_TEXT_NULLCHAR:  render_utf8_codepoint(r, 0x0000, render_verbatim); break;
            case MD_TEXT_ENTITY:    render_entity(r, text, size, fn_append); break;
            default:                fn_append(r, text, size); break;
        }
    }
}


static void
render_open_ol_block(MD_HTML* r, const MD_BLOCK_OL_DETAIL* det)
{
    char buf[64];

    if(det->start == 1) {
        RENDER_VERBATIM(r, "<ol>\n");
        return;
    }

    snprintf(buf, sizeof(buf), "<ol start=\"%u\">\n", det->start);
    RENDER_VERBATIM(r, buf);
}

static void
render_open_li_block(MD_HTML* r, const MD_BLOCK_LI_DETAIL* det)
{
    if(det->is_task) {
        RENDER_VERBATIM(r, "<li class=\"task-list-item\">"
                          "<input type=\"checkbox\" class=\"task-list-item-checkbox\" disabled");
        if(det->task_mark == 'x' || det->task_mark == 'X')
            RENDER_VERBATIM(r, " checked");
        RENDER_VERBATIM(r, ">");
    } else {
        RENDER_VERBATIM(r, "<li>");
    }
}

static void
render_open_code_block(MD_HTML* r, const MD_BLOCK_CODE_DETAIL* det)
{
    RENDER_VERBATIM(r, "<pre><code");

    /* If known, output the HTML 5 attribute class="language-LANGNAME". */
    if(det->lang.text != NULL) {
        RENDER_VERBATIM(r, " class=\"language-");
        render_attribute(r, &det->lang, render_html_escaped);
        RENDER_VERBATIM(r, "\"");
    }

    RENDER_VERBATIM(r, ">");
}

static void
render_open_td_block(MD_HTML* r, const MD_CHAR* cell_type, const MD_BLOCK_TD_DETAIL* det)
{
    RENDER_VERBATIM(r, "<");
    RENDER_VERBATIM(r, cell_type);

    switch(det->align) {
        case MD_ALIGN_LEFT:     RENDER_VERBATIM(r, " align=\"left\">"); break;
        case MD_ALIGN_CENTER:   RENDER_VERBATIM(r, " align=\"center\">"); break;
        case MD_ALIGN_RIGHT:    RENDER_VERBATIM(r, " align=\"right\">"); break;
        default:                RENDER_VERBATIM(r, ">"); break;
    }
}

static void
render_open_a_span(MD_HTML* r, const MD_SPAN_A_DETAIL* det)
{
    RENDER_VERBATIM(r, "<a href=\"");
    render_attribute(r, &det->href, render_url_escaped);

    if(det->title.text != NULL) {
        RENDER_VERBATIM(r, "\" title=\"");
        render_attribute(r, &det->title, render_html_escaped);
    }

    RENDER_VERBATIM(r, "\">");
}

static void
render_open_img_span(MD_HTML* r, const MD_SPAN_IMG_DETAIL* det)
{
    RENDER_VERBATIM(r, "<img src=\"");
    render_attribute(r, &det->src, render_url_escaped);

    RENDER_VERBATIM(r, "\" alt=\"");

    r->image_nesting_level++;
}

static void
render_close_img_span(MD_HTML* r, const MD_SPAN_IMG_DETAIL* det)
{
    if(det->title.text != NULL) {
        RENDER_VERBATIM(r, "\" title=\"");
        render_attribute(r, &det->title, render_html_escaped);
    }

    RENDER_VERBATIM(r, (r->flags & MD_HTML_FLAG_XHTML) ? "\" />" : "\">");

    r->image_nesting_level--;
}

static void
render_open_wikilink_span(MD_HTML* r, const MD_SPAN_WIKILINK_DETAIL* det)
{
    RENDER_VERBATIM(r, "<x-wikilink data-target=\"");
    render_attribute(r, &det->target, render_html_escaped);

    RENDER_VERBATIM(r, "\">");
}


/**************************************
 ***  HTML renderer implementation  ***
 **************************************/

static int
enter_block_callback(MD_BLOCKTYPE type, void* detail, void* userdata)
{
    static const MD_CHAR* head[6] = { "<h1>", "<h2>", "<h3>", "<h4>", "<h5>", "<h6>" };
    MD_HTML* r = (MD_HTML*) userdata;

    switch(type) {
        case MD_BLOCK_DOC:      /* noop */ break;
        case MD_BLOCK_QUOTE:    RENDER_VERBATIM(r, "<blockquote>\n"); break;
        case MD_BLOCK_UL:       RENDER_VERBATIM(r, "<ul>\n"); break;
        case MD_BLOCK_OL:       render_open_ol_block(r, (const MD_BLOCK_OL_DETAIL*)detail); break;
        case MD_BLOCK_LI:       render_open_li_block(r, (const MD_BLOCK_LI_DETAIL*)detail); break;
        case MD_BLOCK_HR:       RENDER_VERBATIM(r, (r->flags & MD_HTML_FLAG_XHTML) ? "<hr />\n" : "<hr>\n"); break;
        case MD_BLOCK_H:        RENDER_VERBATIM(r, head[((MD_BLOCK_H_DETAIL*)detail)->level - 1]); break;
        case MD_BLOCK_CODE:     render_open_code_block(r, (const MD_BLOCK_CODE_DETAIL*) detail); break;
        case MD_BLOCK_HTML:     /* noop */ break;
        case MD_BLOCK_P:        RENDER_VERBATIM(r, "<p>"); break;
        case MD_BLOCK_TABLE:    RENDER_VERBATIM(r, "<table>\n"); break;
        case MD_BLOCK_THEAD:    RENDER_VERBATIM(r, "<thead>\n"); break;
        case MD_BLOCK_TBODY:    RENDER_VERBATIM(r, "<tbody>\n"); break;
        case MD_BLOCK_TR:       RENDER_VERBATIM(r, "<tr>\n"); break;
        case MD_BLOCK_TH:       render_open_td_block(r, "th", (MD_BLOCK_TD_DETAIL*)detail); break;
        case MD_BLOCK_TD:       render_open_td_block(r, "td", (MD_BLOCK_TD_DETAIL*)detail); break;
    }

    return 0;
}

static int
leave_block_callback(MD_BLOCKTYPE type, void* detail, void* userdata)
{
    static const MD_CHAR* head[6] = { "</h1>\n", "</h2>\n", "</h3>\n", "</h4>\n", "</h5>\n", "</h6>\n" };
    MD_HTML* r = (MD_HTML*) userdata;

    switch(type) {
        case MD_BLOCK_DOC:      /*noop*/ break;
        case MD_BLOCK_QUOTE:    RENDER_VERBATIM(r, "</blockquote>\n"); break;
        case MD_BLOCK_UL:       RENDER_VERBATIM(r, "</ul>\n"); break;
        case MD_BLOCK_OL:       RENDER_VERBATIM(r, "</ol>\n"); break;
        case MD_BLOCK_LI:       RENDER_VERBATIM(r, "</li>\n"); break;
        case MD_BLOCK_HR:       /*noop*/ break;
        case MD_BLOCK_H:        RENDER_VERBATIM(r, head[((MD_BLOCK_H_DETAIL*)detail)->level - 1]); break;
        case MD_BLOCK_CODE:     RENDER_VERBATIM(r, "</code></pre>\n"); break;
        case MD_BLOCK_HTML:     /* noop */ break;
        case MD_BLOCK_P:        RENDER_VERBATIM(r, "</p>\n"); break;
        case MD_BLOCK_TABLE:    RENDER_VERBATIM(r, "</table>\n"); break;
        case MD_BLOCK_THEAD:    RENDER_VERBATIM(r, "</thead>\n"); break;
        case MD_BLOCK_TBODY:    RENDER_VERBATIM(r, "</tbody>\n"); break;
        case MD_BLOCK_TR:       RENDER_VERBATIM(r, "</tr>\n"); break;
        case MD_BLOCK_TH:       RENDER_VERBATIM(r, "</th>\n"); break;
        case MD_BLOCK_TD:       RENDER_VERBATIM(r, "</td>\n"); break;
    }

    return 0;
}

static int
enter_span_callback(MD_SPANTYPE type, void* detail, void* userdata)
{
    MD_HTML* r = (MD_HTML*) userdata;

    if(r->image_nesting_level > 0) {
        /* We are inside a Markdown image label. Markdown allows to use any
         * emphasis and other rich contents in that context similarly as in
         * any link label.
         *
         * However, unlike in the case of links (where that contents becomes
         * contents of the <a>...</a> tag), in the case of images the contents
         * is supposed to fall into the attribute alt: <img alt="...">.
         *
         * In that context we naturally cannot output nested HTML tags. So lets
         * suppress them and only output the plain text (i.e. what falls into
         * text() callback).
         *
         * This make-it-a-plain-text approach is the recommended practice by
         * CommonMark specification (for HTML output).
         */
        return 0;
    }

    switch(type) {
        case MD_SPAN_EM:                RENDER_VERBATIM(r, "<em>"); break;
        case MD_SPAN_STRONG:            RENDER_VERBATIM(r, "<strong>"); break;
        case MD_SPAN_U:                 RENDER_VERBATIM(r, "<u>"); break;
        case MD_SPAN_A:                 render_open_a_span(r, (MD_SPAN_A_DETAIL*) detail); break;
        case MD_SPAN_IMG:               render_open_img_span(r, (MD_SPAN_IMG_DETAIL*) detail); break;
        case MD_SPAN_CODE:              RENDER_VERBATIM(r, "<code>"); break;
        case MD_SPAN_DEL:               RENDER_VERBATIM(r, "<del>"); break;
        case MD_SPAN_LATEXMATH:         RENDER_VERBATIM(r, "<x-equation>"); break;
        case MD_SPAN_LATEXMATH_DISPLAY: RENDER_VERBATIM(r, "<x-equation type=\"display\">"); break;
        case MD_SPAN_WIKILINK:          render_open_wikilink_span(r, (MD_SPAN_WIKILINK_DETAIL*) detail); break;
    }

    return 0;
}

static int
leave_span_callback(MD_SPANTYPE type, void* detail, void* userdata)
{
    MD_HTML* r = (MD_HTML*) userdata;

    if(r->image_nesting_level > 0) {
        /* Ditto as in enter_span_callback(), except we have to allow the
         * end of the <img> tag. */
        if(r->image_nesting_level == 1  &&  type == MD_SPAN_IMG)
            render_close_img_span(r, (MD_SPAN_IMG_DETAIL*) detail);
        return 0;
    }

    switch(type) {
        case MD_SPAN_EM:                RENDER_VERBATIM(r, "</em>"); break;
        case MD_SPAN_STRONG:            RENDER_VERBATIM(r, "</strong>"); break;
        case MD_SPAN_U:                 RENDER_VERBATIM(r, "</u>"); break;
        case MD_SPAN_A:                 RENDER_VERBATIM(r, "</a>"); break;
        case MD_SPAN_IMG:               /*noop, handled above*/ break;
        case MD_SPAN_CODE:              RENDER_VERBATIM(r, "</code>"); break;
        case MD_SPAN_DEL:               RENDER_VERBATIM(r, "</del>"); break;
        case MD_SPAN_LATEXMATH:         /*fall through*/
        case MD_SPAN_LATEXMATH_DISPLAY: RENDER_VERBATIM(r, "</x-equation>"); break;
        case MD_SPAN_WIKILINK:          RENDER_VERBATIM(r, "</x-wikilink>"); break;
    }

    return 0;
}

static int
text_callback(MD_TEXTTYPE type, const MD_CHAR* text, MD_SIZE size, void* userdata)
{
    MD_HTML* r = (MD_HTML*) userdata;

    switch(type) {
        case MD_TEXT_NULLCHAR:  render_utf8_codepoint(r, 0x0000, render_verbatim); break;
        case MD_TEXT_BR:        RENDER_VERBATIM(r, (r->image_nesting_level == 0
                                        ? ((r->flags & MD_HTML_FLAG_XHTML) ? "<br />\n" : "<br>\n")
                                        : " "));
                                break;
        case MD_TEXT_SOFTBR:    RENDER_VERBATIM(r, (r->image_nesting_level == 0 ? "\n" : " ")); break;
        case MD_TEXT_HTML:      render_verbatim(r, text, size); break;
        case MD_TEXT_ENTITY:    render_entity(r, text, size, render_html_escaped); break;
        default:                render_html_escaped(r, text, size); break;
    }

    return 0;
}

static void
debug_log_callback(const char* msg, void* userdata)
{
    MD_HTML* r = (MD_HTML*) userdata;
    if(r->flags & MD_HTML_FLAG_DEBUG)
        fprintf(stderr, "MD4C: %s\n", msg);
}

int
md_html(const MD_CHAR* input, MD_SIZE input_size,
        void (*process_output)(const MD_CHAR*, MD_SIZE, void*),
        void* userdata, unsigned parser_flags, unsigned renderer_flags)
{
    MD_HTML render = { process_output, userdata, renderer_flags, 0, { 0 } };
    int i;

    MD_PARSER parser = {
        0,
        parser_flags,
        enter_block_callback,
        leave_block_callback,
        enter_span_callback,
        leave_span_callback,
        text_callback,
        debug_log_callback,
        NULL
    };

    /* Build map of characters which need escaping. */
    for(i = 0; i < 256; i++) {
        unsigned char ch = (unsigned char) i;

        if(strchr("\"&<>", ch) != NULL)
            render.escape_map[i] |= NEED_HTML_ESC_FLAG;

        if(!ISALNUM(ch)  &&  strchr("~-_.+!*(),%#@?=;:/,+$", ch) == NULL)
            render.escape_map[i] |= NEED_URL_ESC_FLAG;
    }

    /* Consider skipping UTF-8 byte order mark (BOM). */
    if(renderer_flags & MD_HTML_FLAG_SKIP_UTF8_BOM  &&  sizeof(MD_CHAR) == 1) {
        static const MD_CHAR bom[3] = { 0xef, 0xbb, 0xbf };
        if(input_size >= sizeof(bom)  &&  memcmp(input, bom, sizeof(bom)) == 0) {
            input += sizeof(bom);
            input_size -= sizeof(bom);
        }
    }

    return md_parse(input, input_size, &parser, (void*) &render);
}