Add tdemarkdown part - embeddable lightweight markdown viewing component.

TDEMarkdown is based on the md4c library and using TDEHTML for rendering
its output. For enhanced safety, on HTML widget is turned off everything
we don't need for viewing. It integrates nicely into Konqueror and
supports both Commonmark and GitHub markdown syntaxes.

Signed-off-by: Mavridis Philippe <mavridisf@gmail.com>

Prepare to merge tdemarkdown into tdelibs.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

1 files changed, 573 insertions, 0 deletions

diff --git a/tdemarkdown/md4c/src/md4c-html.c b/tdemarkdown/md4c/src/md4c-html.c
new file mode 100644
index 000000000..d604aecb0
--- /dev/null
+++ b/tdemarkdown/md4c/src/md4c-html.c
@@ -0,0 +1,573 @@
+/*
+ * 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);
+}
+