Includes cmark markdown parser library.

1 files changed, 1391 insertions, 0 deletions

diff --git a/lib/cmark/src/inlines.c b/lib/cmark/src/inlines.c
new file mode 100644
index 0000000..5b2edc6
--- /dev/null
+++ b/lib/cmark/src/inlines.c
@@ -0,0 +1,1391 @@
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "cmark_ctype.h"
+#include "config.h"
+#include "node.h"
+#include "parser.h"
+#include "references.h"
+#include "cmark.h"
+#include "houdini.h"
+#include "utf8.h"
+#include "scanners.h"
+#include "inlines.h"
+
+static const char *EMDASH = "\xE2\x80\x94";
+static const char *ENDASH = "\xE2\x80\x93";
+static const char *ELLIPSES = "\xE2\x80\xA6";
+static const char *LEFTDOUBLEQUOTE = "\xE2\x80\x9C";
+static const char *RIGHTDOUBLEQUOTE = "\xE2\x80\x9D";
+static const char *LEFTSINGLEQUOTE = "\xE2\x80\x98";
+static const char *RIGHTSINGLEQUOTE = "\xE2\x80\x99";
+
+// Macros for creating various kinds of simple.
+#define make_linebreak(mem) make_simple(mem, CMARK_NODE_LINEBREAK)
+#define make_softbreak(mem) make_simple(mem, CMARK_NODE_SOFTBREAK)
+#define make_emph(mem) make_simple(mem, CMARK_NODE_EMPH)
+#define make_strong(mem) make_simple(mem, CMARK_NODE_STRONG)
+
+#define MAXBACKTICKS 1000
+
+typedef struct delimiter {
+  struct delimiter *previous;
+  struct delimiter *next;
+  cmark_node *inl_text;
+  bufsize_t length;
+  unsigned char delim_char;
+  bool can_open;
+  bool can_close;
+} delimiter;
+
+typedef struct bracket {
+  struct bracket *previous;
+  struct delimiter *previous_delimiter;
+  cmark_node *inl_text;
+  bufsize_t position;
+  bool image;
+  bool active;
+  bool bracket_after;
+} bracket;
+
+typedef struct {
+  cmark_mem *mem;
+  cmark_chunk input;
+  int line;
+  bufsize_t pos;
+  int block_offset;
+  int column_offset;
+  cmark_reference_map *refmap;
+  delimiter *last_delim;
+  bracket *last_bracket;
+  bufsize_t backticks[MAXBACKTICKS + 1];
+  bool scanned_for_backticks;
+} subject;
+
+static CMARK_INLINE bool S_is_line_end_char(char c) {
+  return (c == '\n' || c == '\r');
+}
+
+static delimiter *S_insert_emph(subject *subj, delimiter *opener,
+                                delimiter *closer);
+
+static int parse_inline(subject *subj, cmark_node *parent, int options);
+
+static void subject_from_buf(cmark_mem *mem, int line_number, int block_offset, subject *e,
+                             cmark_chunk *chunk, cmark_reference_map *refmap);
+static bufsize_t subject_find_special_char(subject *subj, int options);
+
+// Create an inline with a literal string value.
+static CMARK_INLINE cmark_node *make_literal(subject *subj, cmark_node_type t,
+                                             int start_column, int end_column) {
+  cmark_node *e = (cmark_node *)subj->mem->calloc(1, sizeof(*e));
+  e->mem = subj->mem;
+  e->type = (uint16_t)t;
+  e->start_line = e->end_line = subj->line;
+  // columns are 1 based.
+  e->start_column = start_column + 1 + subj->column_offset + subj->block_offset;
+  e->end_column = end_column + 1 + subj->column_offset + subj->block_offset;
+  return e;
+}
+
+// Create an inline with no value.
+static CMARK_INLINE cmark_node *make_simple(cmark_mem *mem, cmark_node_type t) {
+  cmark_node *e = (cmark_node *)mem->calloc(1, sizeof(*e));
+  e->mem = mem;
+  e->type = t;
+  return e;
+}
+
+static cmark_node *make_str(subject *subj, int sc, int ec, cmark_chunk s) {
+  cmark_node *e = make_literal(subj, CMARK_NODE_TEXT, sc, ec);
+  e->data = (unsigned char *)subj->mem->realloc(NULL, s.len + 1);
+  if (s.data != NULL) {
+    memcpy(e->data, s.data, s.len);
+  }
+  e->data[s.len] = 0;
+  e->len = s.len;
+  return e;
+}
+
+static cmark_node *make_str_from_buf(subject *subj, int sc, int ec,
+                                     cmark_strbuf *buf) {
+  cmark_node *e = make_literal(subj, CMARK_NODE_TEXT, sc, ec);
+  e->len = buf->size;
+  e->data = cmark_strbuf_detach(buf);
+  return e;
+}
+
+// Like make_str, but parses entities.
+static cmark_node *make_str_with_entities(subject *subj,
+                                          int start_column, int end_column,
+                                          cmark_chunk *content) {
+  cmark_strbuf unescaped = CMARK_BUF_INIT(subj->mem);
+
+  if (houdini_unescape_html(&unescaped, content->data, content->len)) {
+    return make_str_from_buf(subj, start_column, end_column, &unescaped);
+  } else {
+    return make_str(subj, start_column, end_column, *content);
+  }
+}
+
+// Duplicate a chunk by creating a copy of the buffer not by reusing the
+// buffer like cmark_chunk_dup does.
+static unsigned char *cmark_strdup(cmark_mem *mem, unsigned char *src) {
+  if (src == NULL) {
+    return NULL;
+  }
+  size_t len = strlen((char *)src);
+  unsigned char *data = (unsigned char *)mem->realloc(NULL, len + 1);
+  memcpy(data, src, len + 1);
+  return data;
+}
+
+static unsigned char *cmark_clean_autolink(cmark_mem *mem, cmark_chunk *url,
+                                           int is_email) {
+  cmark_strbuf buf = CMARK_BUF_INIT(mem);
+
+  cmark_chunk_trim(url);
+
+  if (is_email)
+    cmark_strbuf_puts(&buf, "mailto:");
+
+  houdini_unescape_html_f(&buf, url->data, url->len);
+  return cmark_strbuf_detach(&buf);
+}
+
+static CMARK_INLINE cmark_node *make_autolink(subject *subj,
+                                              int start_column, int end_column,
+                                              cmark_chunk url, int is_email) {
+  cmark_node *link = make_simple(subj->mem, CMARK_NODE_LINK);
+  link->as.link.url = cmark_clean_autolink(subj->mem, &url, is_email);
+  link->as.link.title = NULL;
+  link->start_line = link->end_line = subj->line;
+  link->start_column = start_column + 1;
+  link->end_column = end_column + 1;
+  cmark_node_append_child(link, make_str_with_entities(subj, start_column + 1, end_column - 1, &url));
+  return link;
+}
+
+static void subject_from_buf(cmark_mem *mem, int line_number, int block_offset, subject *e,
+                             cmark_chunk *chunk, cmark_reference_map *refmap) {
+  int i;
+  e->mem = mem;
+  e->input = *chunk;
+  e->line = line_number;
+  e->pos = 0;
+  e->block_offset = block_offset;
+  e->column_offset = 0;
+  e->refmap = refmap;
+  e->last_delim = NULL;
+  e->last_bracket = NULL;
+  for (i = 0; i <= MAXBACKTICKS; i++) {
+    e->backticks[i] = 0;
+  }
+  e->scanned_for_backticks = false;
+}
+
+static CMARK_INLINE int isbacktick(int c) { return (c == '`'); }
+
+static CMARK_INLINE unsigned char peek_char(subject *subj) {
+  // NULL bytes should have been stripped out by now.  If they're
+  // present, it's a programming error:
+  assert(!(subj->pos < subj->input.len && subj->input.data[subj->pos] == 0));
+  return (subj->pos < subj->input.len) ? subj->input.data[subj->pos] : 0;
+}
+
+static CMARK_INLINE unsigned char peek_at(subject *subj, bufsize_t pos) {
+  return subj->input.data[pos];
+}
+
+// Return true if there are more characters in the subject.
+static CMARK_INLINE int is_eof(subject *subj) {
+  return (subj->pos >= subj->input.len);
+}
+
+// Advance the subject.  Doesn't check for eof.
+#define advance(subj) (subj)->pos += 1
+
+static CMARK_INLINE bool skip_spaces(subject *subj) {
+  bool skipped = false;
+  while (peek_char(subj) == ' ' || peek_char(subj) == '\t') {
+    advance(subj);
+    skipped = true;
+  }
+  return skipped;
+}
+
+static CMARK_INLINE bool skip_line_end(subject *subj) {
+  bool seen_line_end_char = false;
+  if (peek_char(subj) == '\r') {
+    advance(subj);
+    seen_line_end_char = true;
+  }
+  if (peek_char(subj) == '\n') {
+    advance(subj);
+    seen_line_end_char = true;
+  }
+  return seen_line_end_char || is_eof(subj);
+}
+
+// Take characters while a predicate holds, and return a string.
+static CMARK_INLINE cmark_chunk take_while(subject *subj, int (*f)(int)) {
+  unsigned char c;
+  bufsize_t startpos = subj->pos;
+  bufsize_t len = 0;
+
+  while ((c = peek_char(subj)) && (*f)(c)) {
+    advance(subj);
+    len++;
+  }
+
+  return cmark_chunk_dup(&subj->input, startpos, len);
+}
+
+// Return the number of newlines in a given span of text in a subject.  If
+// the number is greater than zero, also return the number of characters
+// between the last newline and the end of the span in `since_newline`.
+static int count_newlines(subject *subj, bufsize_t from, bufsize_t len, int *since_newline) {
+  int nls = 0;
+  int since_nl = 0;
+
+  while (len--) {
+    if (subj->input.data[from++] == '\n') {
+      ++nls;
+      since_nl = 0;
+    } else {
+      ++since_nl;
+    }
+  }
+
+  if (!nls)
+    return 0;
+
+  *since_newline = since_nl;
+  return nls;
+}
+
+// Adjust `node`'s `end_line`, `end_column`, and `subj`'s `line` and
+// `column_offset` according to the number of newlines in a just-matched span
+// of text in `subj`.
+static void adjust_subj_node_newlines(subject *subj, cmark_node *node, int matchlen, int extra, int options) {
+  if (!(options & CMARK_OPT_SOURCEPOS)) {
+    return;
+  }
+
+  int since_newline;
+  int newlines = count_newlines(subj, subj->pos - matchlen - extra, matchlen, &since_newline);
+  if (newlines) {
+    subj->line += newlines;
+    node->end_line += newlines;
+    node->end_column = since_newline;
+    subj->column_offset = -subj->pos + since_newline + extra;
+  }
+}
+
+// Try to process a backtick code span that began with a
+// span of ticks of length openticklength length (already
+// parsed).  Return 0 if you don't find matching closing
+// backticks, otherwise return the position in the subject
+// after the closing backticks.
+static bufsize_t scan_to_closing_backticks(subject *subj,
+                                           bufsize_t openticklength) {
+
+  bool found = false;
+  if (openticklength > MAXBACKTICKS) {
+    // we limit backtick string length because of the array subj->backticks:
+    return 0;
+  }
+  if (subj->scanned_for_backticks &&
+      subj->backticks[openticklength] <= subj->pos) {
+    // return if we already know there's no closer
+    return 0;
+  }
+  while (!found) {
+    // read non backticks
+    unsigned char c;
+    while ((c = peek_char(subj)) && c != '`') {
+      advance(subj);
+    }
+    if (is_eof(subj)) {
+      break;
+    }
+    bufsize_t numticks = 0;
+    while (peek_char(subj) == '`') {
+      advance(subj);
+      numticks++;
+    }
+    // store position of ender
+    if (numticks <= MAXBACKTICKS) {
+      subj->backticks[numticks] = subj->pos - numticks;
+    }
+    if (numticks == openticklength) {
+      return (subj->pos);
+    }
+  }
+  // got through whole input without finding closer
+  subj->scanned_for_backticks = true;
+  return 0;
+}
+
+// Destructively modify string, converting newlines to
+// spaces, then removing a single leading + trailing space,
+// unless the code span consists entirely of space characters.
+static void S_normalize_code(cmark_strbuf *s) {
+  bufsize_t r, w;
+  bool contains_nonspace = false;
+
+  for (r = 0, w = 0; r < s->size; ++r) {
+    switch (s->ptr[r]) {
+    case '\r':
+      if (s->ptr[r + 1] != '\n') {
+	s->ptr[w++] = ' ';
+      }
+      break;
+    case '\n':
+      s->ptr[w++] = ' ';
+      break;
+    default:
+      s->ptr[w++] = s->ptr[r];
+    }
+    if (s->ptr[r] != ' ') {
+      contains_nonspace = true;
+    }
+  }
+
+  // begins and ends with space?
+  if (contains_nonspace &&
+      s->ptr[0] == ' ' && s->ptr[w - 1] == ' ') {
+    cmark_strbuf_drop(s, 1);
+    cmark_strbuf_truncate(s, w - 2);
+  } else {
+    cmark_strbuf_truncate(s, w);
+  }
+
+}
+
+
+// Parse backtick code section or raw backticks, return an inline.
+// Assumes that the subject has a backtick at the current position.
+static cmark_node *handle_backticks(subject *subj, int options) {
+  cmark_chunk openticks = take_while(subj, isbacktick);
+  bufsize_t startpos = subj->pos;
+  bufsize_t endpos = scan_to_closing_backticks(subj, openticks.len);
+
+  if (endpos == 0) {      // not found
+    subj->pos = startpos; // rewind
+    return make_str(subj, subj->pos, subj->pos, openticks);
+  } else {
+    cmark_strbuf buf = CMARK_BUF_INIT(subj->mem);
+
+    cmark_strbuf_set(&buf, subj->input.data + startpos,
+                     endpos - startpos - openticks.len);
+    S_normalize_code(&buf);
+
+    cmark_node *node = make_literal(subj, CMARK_NODE_CODE, startpos,
+                                    endpos - openticks.len - 1);
+    node->len = buf.size;
+    node->data = cmark_strbuf_detach(&buf);
+    adjust_subj_node_newlines(subj, node, endpos - startpos, openticks.len, options);
+    return node;
+  }
+}
+
+
+// Scan ***, **, or * and return number scanned, or 0.
+// Advances position.
+static int scan_delims(subject *subj, unsigned char c, bool *can_open,
+                       bool *can_close) {
+  int numdelims = 0;
+  bufsize_t before_char_pos;
+  int32_t after_char = 0;
+  int32_t before_char = 0;
+  int len;
+  bool left_flanking, right_flanking;
+
+  if (subj->pos == 0) {
+    before_char = 10;
+  } else {
+    before_char_pos = subj->pos - 1;
+    // walk back to the beginning of the UTF_8 sequence:
+    while (peek_at(subj, before_char_pos) >> 6 == 2 && before_char_pos > 0) {
+      before_char_pos -= 1;
+    }
+    len = cmark_utf8proc_iterate(subj->input.data + before_char_pos,
+                                 subj->pos - before_char_pos, &before_char);
+    if (len == -1) {
+      before_char = 10;
+    }
+  }
+
+  if (c == '\'' || c == '"') {
+    numdelims++;
+    advance(subj); // limit to 1 delim for quotes
+  } else {
+    while (peek_char(subj) == c) {
+      numdelims++;
+      advance(subj);
+    }
+  }
+
+  len = cmark_utf8proc_iterate(subj->input.data + subj->pos,
+                               subj->input.len - subj->pos, &after_char);
+  if (len == -1) {
+    after_char = 10;
+  }
+  left_flanking = numdelims > 0 && !cmark_utf8proc_is_space(after_char) &&
+                  (!cmark_utf8proc_is_punctuation(after_char) ||
+                   cmark_utf8proc_is_space(before_char) ||
+                   cmark_utf8proc_is_punctuation(before_char));
+  right_flanking = numdelims > 0 && !cmark_utf8proc_is_space(before_char) &&
+                   (!cmark_utf8proc_is_punctuation(before_char) ||
+                    cmark_utf8proc_is_space(after_char) ||
+                    cmark_utf8proc_is_punctuation(after_char));
+  if (c == '_') {
+    *can_open = left_flanking &&
+                (!right_flanking || cmark_utf8proc_is_punctuation(before_char));
+    *can_close = right_flanking &&
+                 (!left_flanking || cmark_utf8proc_is_punctuation(after_char));
+  } else if (c == '\'' || c == '"') {
+    *can_open = left_flanking &&
+         (!right_flanking || before_char == '(' || before_char == '[') &&
+         before_char != ']' && before_char != ')';
+    *can_close = right_flanking;
+  } else {
+    *can_open = left_flanking;
+    *can_close = right_flanking;
+  }
+  return numdelims;
+}
+
+/*
+static void print_delimiters(subject *subj)
+{
+        delimiter *delim;
+        delim = subj->last_delim;
+        while (delim != NULL) {
+                printf("Item at stack pos %p: %d %d %d next(%p) prev(%p)\n",
+                       (void*)delim, delim->delim_char,
+                       delim->can_open, delim->can_close,
+                       (void*)delim->next, (void*)delim->previous);
+                delim = delim->previous;
+        }
+}
+*/
+
+static void remove_delimiter(subject *subj, delimiter *delim) {
+  if (delim == NULL)
+    return;
+  if (delim->next == NULL) {
+    // end of list:
+    assert(delim == subj->last_delim);
+    subj->last_delim = delim->previous;
+  } else {
+    delim->next->previous = delim->previous;
+  }
+  if (delim->previous != NULL) {
+    delim->previous->next = delim->next;
+  }
+  subj->mem->free(delim);
+}
+
+static void pop_bracket(subject *subj) {
+  bracket *b;
+  if (subj->last_bracket == NULL)
+    return;
+  b = subj->last_bracket;
+  subj->last_bracket = subj->last_bracket->previous;
+  subj->mem->free(b);
+}
+
+static void push_delimiter(subject *subj, unsigned char c, bool can_open,
+                           bool can_close, cmark_node *inl_text) {
+  delimiter *delim = (delimiter *)subj->mem->calloc(1, sizeof(delimiter));
+  delim->delim_char = c;
+  delim->can_open = can_open;
+  delim->can_close = can_close;
+  delim->inl_text = inl_text;
+  delim->length = inl_text->len;
+  delim->previous = subj->last_delim;
+  delim->next = NULL;
+  if (delim->previous != NULL) {
+    delim->previous->next = delim;
+  }
+  subj->last_delim = delim;
+}
+
+static void push_bracket(subject *subj, bool image, cmark_node *inl_text) {
+  bracket *b = (bracket *)subj->mem->calloc(1, sizeof(bracket));
+  if (subj->last_bracket != NULL) {
+    subj->last_bracket->bracket_after = true;
+  }
+  b->image = image;
+  b->active = true;
+  b->inl_text = inl_text;
+  b->previous = subj->last_bracket;
+  b->previous_delimiter = subj->last_delim;
+  b->position = subj->pos;
+  b->bracket_after = false;
+  subj->last_bracket = b;
+}
+
+// Assumes the subject has a c at the current position.
+static cmark_node *handle_delim(subject *subj, unsigned char c, bool smart) {
+  bufsize_t numdelims;
+  cmark_node *inl_text;
+  bool can_open, can_close;
+  cmark_chunk contents;
+
+  numdelims = scan_delims(subj, c, &can_open, &can_close);
+
+  if (c == '\'' && smart) {
+    contents = cmark_chunk_literal(RIGHTSINGLEQUOTE);
+  } else if (c == '"' && smart) {
+    contents =
+        cmark_chunk_literal(can_close ? RIGHTDOUBLEQUOTE : LEFTDOUBLEQUOTE);
+  } else {
+    contents = cmark_chunk_dup(&subj->input, subj->pos - numdelims, numdelims);
+  }
+
+  inl_text = make_str(subj, subj->pos - numdelims, subj->pos - 1, contents);
+
+  if ((can_open || can_close) && (!(c == '\'' || c == '"') || smart)) {
+    push_delimiter(subj, c, can_open, can_close, inl_text);
+  }
+
+  return inl_text;
+}
+
+// Assumes we have a hyphen at the current position.
+static cmark_node *handle_hyphen(subject *subj, bool smart) {
+  int startpos = subj->pos;
+
+  advance(subj);
+
+  if (!smart || peek_char(subj) != '-') {
+    return make_str(subj, subj->pos - 1, subj->pos - 1, cmark_chunk_literal("-"));
+  }
+
+  while (smart && peek_char(subj) == '-') {
+    advance(subj);
+  }
+
+  int numhyphens = subj->pos - startpos;
+  int en_count = 0;
+  int em_count = 0;
+  int i;
+  cmark_strbuf buf = CMARK_BUF_INIT(subj->mem);
+
+  if (numhyphens % 3 == 0) { // if divisible by 3, use all em dashes
+    em_count = numhyphens / 3;
+  } else if (numhyphens % 2 == 0) { // if divisible by 2, use all en dashes
+    en_count = numhyphens / 2;
+  } else if (numhyphens % 3 == 2) { // use one en dash at end
+    en_count = 1;
+    em_count = (numhyphens - 2) / 3;
+  } else { // use two en dashes at the end
+    en_count = 2;
+    em_count = (numhyphens - 4) / 3;
+  }
+
+  for (i = em_count; i > 0; i--) {
+    cmark_strbuf_puts(&buf, EMDASH);
+  }
+
+  for (i = en_count; i > 0; i--) {
+    cmark_strbuf_puts(&buf, ENDASH);
+  }
+
+  return make_str_from_buf(subj, startpos, subj->pos - 1, &buf);
+}
+
+// Assumes we have a period at the current position.
+static cmark_node *handle_period(subject *subj, bool smart) {
+  advance(subj);
+  if (smart && peek_char(subj) == '.') {
+    advance(subj);
+    if (peek_char(subj) == '.') {
+      advance(subj);
+      return make_str(subj, subj->pos - 3, subj->pos - 1, cmark_chunk_literal(ELLIPSES));
+    } else {
+      return make_str(subj, subj->pos - 2, subj->pos - 1, cmark_chunk_literal(".."));
+    }
+  } else {
+    return make_str(subj, subj->pos - 1, subj->pos - 1, cmark_chunk_literal("."));
+  }
+}
+
+static void process_emphasis(subject *subj, delimiter *stack_bottom) {
+  delimiter *closer = subj->last_delim;
+  delimiter *opener;
+  delimiter *old_closer;
+  bool opener_found;
+  int openers_bottom_index = 0;
+  delimiter *openers_bottom[6] = {stack_bottom, stack_bottom, stack_bottom,
+                                  stack_bottom, stack_bottom, stack_bottom};
+
+  // move back to first relevant delim.
+  while (closer != NULL && closer->previous != stack_bottom) {
+    closer = closer->previous;
+  }
+
+  // now move forward, looking for closers, and handling each
+  while (closer != NULL) {
+    if (closer->can_close) {
+      switch (closer->delim_char) {
+      case '"':
+        openers_bottom_index = 0;
+        break;
+      case '\'':
+        openers_bottom_index = 1;
+        break;
+      case '_':
+        openers_bottom_index = 2;
+        break;
+      case '*':
+        openers_bottom_index = 3 + (closer->length % 3);
+        break;
+      default:
+        assert(false);
+      }
+
+      // Now look backwards for first matching opener:
+      opener = closer->previous;
+      opener_found = false;
+      while (opener != NULL && opener != openers_bottom[openers_bottom_index]) {
+        if (opener->can_open && opener->delim_char == closer->delim_char) {
+          // interior closer of size 2 can't match opener of size 1
+          // or of size 1 can't match 2
+          if (!(closer->can_open || opener->can_close) ||
+	      closer->length % 3 == 0 ||
+              (opener->length + closer->length) % 3 != 0) {
+            opener_found = true;
+            break;
+          }
+        }
+        opener = opener->previous;
+      }
+      old_closer = closer;
+      if (closer->delim_char == '*' || closer->delim_char == '_') {
+        if (opener_found) {
+          closer = S_insert_emph(subj, opener, closer);
+        } else {
+          closer = closer->next;
+        }
+      } else if (closer->delim_char == '\'') {
+        cmark_node_set_literal(closer->inl_text, RIGHTSINGLEQUOTE);
+        if (opener_found) {
+          cmark_node_set_literal(opener->inl_text, LEFTSINGLEQUOTE);
+        }
+        closer = closer->next;
+      } else if (closer->delim_char == '"') {
+        cmark_node_set_literal(closer->inl_text, RIGHTDOUBLEQUOTE);
+        if (opener_found) {
+          cmark_node_set_literal(opener->inl_text, LEFTDOUBLEQUOTE);
+        }
+        closer = closer->next;
+      }
+      if (!opener_found) {
+        // set lower bound for future searches for openers
+        openers_bottom[openers_bottom_index] = old_closer->previous;
+        if (!old_closer->can_open) {
+          // we can remove a closer that can't be an
+          // opener, once we've seen there's no
+          // matching opener:
+          remove_delimiter(subj, old_closer);
+        }
+      }
+    } else {
+      closer = closer->next;
+    }
+  }
+  // free all delimiters in list until stack_bottom:
+  while (subj->last_delim != NULL && subj->last_delim != stack_bottom) {
+    remove_delimiter(subj, subj->last_delim);
+  }
+}
+
+static delimiter *S_insert_emph(subject *subj, delimiter *opener,
+                                delimiter *closer) {
+  delimiter *delim, *tmp_delim;
+  bufsize_t use_delims;
+  cmark_node *opener_inl = opener->inl_text;
+  cmark_node *closer_inl = closer->inl_text;
+  bufsize_t opener_num_chars = opener_inl->len;
+  bufsize_t closer_num_chars = closer_inl->len;
+  cmark_node *tmp, *tmpnext, *emph;
+
+  // calculate the actual number of characters used from this closer
+  use_delims = (closer_num_chars >= 2 && opener_num_chars >= 2) ? 2 : 1;
+
+  // remove used characters from associated inlines.
+  opener_num_chars -= use_delims;
+  closer_num_chars -= use_delims;
+  opener_inl->len = opener_num_chars;
+  opener_inl->data[opener_num_chars] = 0;
+  closer_inl->len = closer_num_chars;
+  closer_inl->data[closer_num_chars] = 0;
+
+  // free delimiters between opener and closer
+  delim = closer->previous;
+  while (delim != NULL && delim != opener) {
+    tmp_delim = delim->previous;
+    remove_delimiter(subj, delim);
+    delim = tmp_delim;
+  }
+
+  // create new emph or strong, and splice it in to our inlines
+  // between the opener and closer
+  emph = use_delims == 1 ? make_emph(subj->mem) : make_strong(subj->mem);
+
+  tmp = opener_inl->next;
+  while (tmp && tmp != closer_inl) {
+    tmpnext = tmp->next;
+    cmark_node_append_child(emph, tmp);
+    tmp = tmpnext;
+  }
+  cmark_node_insert_after(opener_inl, emph);
+
+  emph->start_line = opener_inl->start_line;
+  emph->end_line = closer_inl->end_line;
+  emph->start_column = opener_inl->start_column;
+  emph->end_column = closer_inl->end_column;
+
+  // if opener has 0 characters, remove it and its associated inline
+  if (opener_num_chars == 0) {
+    cmark_node_free(opener_inl);
+    remove_delimiter(subj, opener);
+  }
+
+  // if closer has 0 characters, remove it and its associated inline
+  if (closer_num_chars == 0) {
+    // remove empty closer inline
+    cmark_node_free(closer_inl);
+    // remove closer from list
+    tmp_delim = closer->next;
+    remove_delimiter(subj, closer);
+    closer = tmp_delim;
+  }
+
+  return closer;
+}
+
+// Parse backslash-escape or just a backslash, returning an inline.
+static cmark_node *handle_backslash(subject *subj) {
+  advance(subj);
+  unsigned char nextchar = peek_char(subj);
+  if (cmark_ispunct(
+          nextchar)) { // only ascii symbols and newline can be escaped
+    advance(subj);
+    return make_str(subj, subj->pos - 2, subj->pos - 1, cmark_chunk_dup(&subj->input, subj->pos - 1, 1));
+  } else if (!is_eof(subj) && skip_line_end(subj)) {
+    return make_linebreak(subj->mem);
+  } else {
+    return make_str(subj, subj->pos - 1, subj->pos - 1, cmark_chunk_literal("\\"));
+  }
+}
+
+// Parse an entity or a regular "&" string.
+// Assumes the subject has an '&' character at the current position.
+static cmark_node *handle_entity(subject *subj) {
+  cmark_strbuf ent = CMARK_BUF_INIT(subj->mem);
+  bufsize_t len;
+
+  advance(subj);
+
+  len = houdini_unescape_ent(&ent, subj->input.data + subj->pos,
+                             subj->input.len - subj->pos);
+
+  if (len <= 0)
+    return make_str(subj, subj->pos - 1, subj->pos - 1, cmark_chunk_literal("&"));
+
+  subj->pos += len;
+  return make_str_from_buf(subj, subj->pos - 1 - len, subj->pos - 1, &ent);
+}
+
+// Clean a URL: remove surrounding whitespace, and remove \ that escape
+// punctuation.
+unsigned char *cmark_clean_url(cmark_mem *mem, cmark_chunk *url) {
+  cmark_strbuf buf = CMARK_BUF_INIT(mem);
+
+  cmark_chunk_trim(url);
+
+  houdini_unescape_html_f(&buf, url->data, url->len);
+
+  cmark_strbuf_unescape(&buf);
+  return cmark_strbuf_detach(&buf);
+}
+
+unsigned char *cmark_clean_title(cmark_mem *mem, cmark_chunk *title) {
+  cmark_strbuf buf = CMARK_BUF_INIT(mem);
+  unsigned char first, last;
+
+  if (title->len == 0) {
+    return NULL;
+  }
+
+  first = title->data[0];
+  last = title->data[title->len - 1];
+
+  // remove surrounding quotes if any:
+  if ((first == '\'' && last == '\'') || (first == '(' && last == ')') ||
+      (first == '"' && last == '"')) {
+    houdini_unescape_html_f(&buf, title->data + 1, title->len - 2);
+  } else {
+    houdini_unescape_html_f(&buf, title->data, title->len);
+  }
+
+  cmark_strbuf_unescape(&buf);
+  return cmark_strbuf_detach(&buf);
+}
+
+// Parse an autolink or HTML tag.
+// Assumes the subject has a '<' character at the current position.
+static cmark_node *handle_pointy_brace(subject *subj, int options) {
+  bufsize_t matchlen = 0;
+  cmark_chunk contents;
+
+  advance(subj); // advance past first <
+
+  // first try to match a URL autolink
+  matchlen = scan_autolink_uri(&subj->input, subj->pos);
+  if (matchlen > 0) {
+    contents = cmark_chunk_dup(&subj->input, subj->pos, matchlen - 1);
+    subj->pos += matchlen;
+
+    return make_autolink(subj, subj->pos - 1 - matchlen, subj->pos - 1, contents, 0);
+  }
+
+  // next try to match an email autolink
+  matchlen = scan_autolink_email(&subj->input, subj->pos);
+  if (matchlen > 0) {
+    contents = cmark_chunk_dup(&subj->input, subj->pos, matchlen - 1);
+    subj->pos += matchlen;
+
+    return make_autolink(subj, subj->pos - 1 - matchlen, subj->pos - 1, contents, 1);
+  }
+
+  // finally, try to match an html tag
+  matchlen = scan_html_tag(&subj->input, subj->pos);
+  if (matchlen > 0) {
+    const unsigned char *src = subj->input.data + subj->pos - 1;
+    bufsize_t len = matchlen + 1;
+    subj->pos += matchlen;
+    cmark_node *node = make_literal(subj, CMARK_NODE_HTML_INLINE,
+                                    subj->pos - matchlen - 1, subj->pos - 1);
+    node->data = (unsigned char *)subj->mem->realloc(NULL, len + 1);
+    memcpy(node->data, src, len);
+    node->data[len] = 0;
+    node->len = len;
+    adjust_subj_node_newlines(subj, node, matchlen, 1, options);
+    return node;
+  }
+
+  // if nothing matches, just return the opening <:
+  return make_str(subj, subj->pos - 1, subj->pos - 1, cmark_chunk_literal("<"));
+}
+
+// Parse a link label.  Returns 1 if successful.
+// Note:  unescaped brackets are not allowed in labels.
+// The label begins with `[` and ends with the first `]` character
+// encountered.  Backticks in labels do not start code spans.
+static int link_label(subject *subj, cmark_chunk *raw_label) {
+  bufsize_t startpos = subj->pos;
+  int length = 0;
+  unsigned char c;
+
+  // advance past [
+  if (peek_char(subj) == '[') {
+    advance(subj);
+  } else {
+    return 0;
+  }
+
+  while ((c = peek_char(subj)) && c != '[' && c != ']') {
+    if (c == '\\') {
+      advance(subj);
+      length++;
+      if (cmark_ispunct(peek_char(subj))) {
+        advance(subj);
+        length++;
+      }
+    } else {
+      advance(subj);
+      length++;
+    }
+    if (length > MAX_LINK_LABEL_LENGTH) {
+      goto noMatch;
+    }
+  }
+
+  if (c == ']') { // match found
+    *raw_label =
+        cmark_chunk_dup(&subj->input, startpos + 1, subj->pos - (startpos + 1));
+    cmark_chunk_trim(raw_label);
+    advance(subj); // advance past ]
+    return 1;
+  }
+
+noMatch:
+  subj->pos = startpos; // rewind
+  return 0;
+}
+
+static bufsize_t manual_scan_link_url_2(cmark_chunk *input, bufsize_t offset,
+                                        cmark_chunk *output) {
+  bufsize_t i = offset;
+  size_t nb_p = 0;
+
+  while (i < input->len) {
+    if (input->data[i] == '\\' &&
+        i + 1 < input-> len &&
+        cmark_ispunct(input->data[i+1]))
+      i += 2;
+    else if (input->data[i] == '(') {
+      ++nb_p;
+      ++i;
+      if (nb_p > 32)
+        return -1;
+    } else if (input->data[i] == ')') {
+      if (nb_p == 0)
+        break;
+      --nb_p;
+      ++i;
+    } else if (cmark_isspace(input->data[i])) {
+      if (i == offset) {
+        return -1;
+      }
+      break;
+    } else {
+      ++i;
+    }
+  }
+
+  if (i >= input->len || nb_p != 0)
+    return -1;
+
+  {
+    cmark_chunk result = {input->data + offset, i - offset};
+    *output = result;
+  }
+  return i - offset;
+}
+
+static bufsize_t manual_scan_link_url(cmark_chunk *input, bufsize_t offset,
+                                      cmark_chunk *output) {
+  bufsize_t i = offset;
+
+  if (i < input->len && input->data[i] == '<') {
+    ++i;
+    while (i < input->len) {
+      if (input->data[i] == '>') {
+        ++i;
+        break;
+      } else if (input->data[i] == '\\')
+        i += 2;
+      else if (input->data[i] == '\n' || input->data[i] == '<')
+        return -1;
+      else
+        ++i;
+    }
+  } else {
+    return manual_scan_link_url_2(input, offset, output);
+  }
+
+  if (i >= input->len)
+    return -1;
+
+  {
+    cmark_chunk result = {input->data + offset + 1, i - 2 - offset};
+    *output = result;
+  }
+  return i - offset;
+}
+
+// Return a link, an image, or a literal close bracket.
+static cmark_node *handle_close_bracket(subject *subj) {
+  bufsize_t initial_pos, after_link_text_pos;
+  bufsize_t endurl, starttitle, endtitle, endall;
+  bufsize_t sps, n;
+  cmark_reference *ref = NULL;
+  cmark_chunk url_chunk, title_chunk;
+  unsigned char *url, *title;
+  bracket *opener;
+  cmark_node *inl;
+  cmark_chunk raw_label;
+  int found_label;
+  cmark_node *tmp, *tmpnext;
+  bool is_image;
+
+  advance(subj); // advance past ]
+  initial_pos = subj->pos;
+
+  // get last [ or ![
+  opener = subj->last_bracket;
+
+  if (opener == NULL) {
+    return make_str(subj, subj->pos - 1, subj->pos - 1, cmark_chunk_literal("]"));
+  }
+
+  if (!opener->active) {
+    // take delimiter off stack
+    pop_bracket(subj);
+    return make_str(subj, subj->pos - 1, subj->pos - 1, cmark_chunk_literal("]"));
+  }
+
+  // If we got here, we matched a potential link/image text.
+  // Now we check to see if it's a link/image.
+  is_image = opener->image;
+
+  after_link_text_pos = subj->pos;
+
+  // First, look for an inline link.
+  if (peek_char(subj) == '(' &&
+      ((sps = scan_spacechars(&subj->input, subj->pos + 1)) > -1) &&
+      ((n = manual_scan_link_url(&subj->input, subj->pos + 1 + sps,
+                                 &url_chunk)) > -1)) {
+
+    // try to parse an explicit link:
+    endurl = subj->pos + 1 + sps + n;
+    starttitle = endurl + scan_spacechars(&subj->input, endurl);
+
+    // ensure there are spaces btw url and title
+    endtitle = (starttitle == endurl)
+                   ? starttitle
+                   : starttitle + scan_link_title(&subj->input, starttitle);
+
+    endall = endtitle + scan_spacechars(&subj->input, endtitle);
+
+    if (peek_at(subj, endall) == ')') {
+      subj->pos = endall + 1;
+
+      title_chunk =
+          cmark_chunk_dup(&subj->input, starttitle, endtitle - starttitle);
+      url = cmark_clean_url(subj->mem, &url_chunk);
+      title = cmark_clean_title(subj->mem, &title_chunk);
+      cmark_chunk_free(&url_chunk);
+      cmark_chunk_free(&title_chunk);
+      goto match;
+
+    } else {
+      // it could still be a shortcut reference link
+      subj->pos = after_link_text_pos;
+    }
+  }
+
+  // Next, look for a following [link label] that matches in refmap.
+  // skip spaces
+  raw_label = cmark_chunk_literal("");
+  found_label = link_label(subj, &raw_label);
+  if (!found_label) {
+    // If we have a shortcut reference link, back up
+    // to before the spacse we skipped.
+    subj->pos = initial_pos;
+  }
+
+  if ((!found_label || raw_label.len == 0) && !opener->bracket_after) {
+    cmark_chunk_free(&raw_label);
+    raw_label = cmark_chunk_dup(&subj->input, opener->position,
+                                initial_pos - opener->position - 1);
+    found_label = true;
+  }
+
+  if (found_label) {
+    ref = cmark_reference_lookup(subj->refmap, &raw_label);
+    cmark_chunk_free(&raw_label);
+  }
+
+  if (ref != NULL) { // found
+    url = cmark_strdup(subj->mem, ref->url);
+    title = cmark_strdup(subj->mem, ref->title);
+    goto match;
+  } else {
+    goto noMatch;
+  }
+
+noMatch:
+  // If we fall through to here, it means we didn't match a link:
+  pop_bracket(subj); // remove this opener from delimiter list
+  subj->pos = initial_pos;
+  return make_str(subj, subj->pos - 1, subj->pos - 1, cmark_chunk_literal("]"));
+
+match:
+  inl = make_simple(subj->mem, is_image ? CMARK_NODE_IMAGE : CMARK_NODE_LINK);
+  inl->as.link.url = url;
+  inl->as.link.title = title;
+  inl->start_line = inl->end_line = subj->line;
+  inl->start_column = opener->inl_text->start_column;
+  inl->end_column = subj->pos + subj->column_offset + subj->block_offset;
+  cmark_node_insert_before(opener->inl_text, inl);
+  // Add link text:
+  tmp = opener->inl_text->next;
+  while (tmp) {
+    tmpnext = tmp->next;
+    cmark_node_append_child(inl, tmp);
+    tmp = tmpnext;
+  }
+
+  // Free the bracket [:
+  cmark_node_free(opener->inl_text);
+
+  process_emphasis(subj, opener->previous_delimiter);
+  pop_bracket(subj);
+
+  // Now, if we have a link, we also want to deactivate earlier link
+  // delimiters. (This code can be removed if we decide to allow links
+  // inside links.)
+  if (!is_image) {
+    opener = subj->last_bracket;
+    while (opener != NULL) {
+      if (!opener->image) {
+        if (!opener->active) {
+          break;
+        } else {
+          opener->active = false;
+        }
+      }
+      opener = opener->previous;
+    }
+  }
+
+  return NULL;
+}
+
+// Parse a hard or soft linebreak, returning an inline.
+// Assumes the subject has a cr or newline at the current position.
+static cmark_node *handle_newline(subject *subj) {
+  bufsize_t nlpos = subj->pos;
+  // skip over cr, crlf, or lf:
+  if (peek_at(subj, subj->pos) == '\r') {
+    advance(subj);
+  }
+  if (peek_at(subj, subj->pos) == '\n') {
+    advance(subj);
+  }
+  ++subj->line;
+  subj->column_offset = -subj->pos;
+  // skip spaces at beginning of line
+  skip_spaces(subj);
+  if (nlpos > 1 && peek_at(subj, nlpos - 1) == ' ' &&
+      peek_at(subj, nlpos - 2) == ' ') {
+    return make_linebreak(subj->mem);
+  } else {
+    return make_softbreak(subj->mem);
+  }
+}
+
+static bufsize_t subject_find_special_char(subject *subj, int options) {
+  // "\r\n\\`&_*[]<!"
+  static const int8_t SPECIAL_CHARS[256] = {
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1,
+      1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+
+  // " ' . -
+  static const char SMART_PUNCT_CHARS[] = {
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 1, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  };
+
+  bufsize_t n = subj->pos + 1;
+
+  while (n < subj->input.len) {
+    if (SPECIAL_CHARS[subj->input.data[n]])
+      return n;
+    if (options & CMARK_OPT_SMART && SMART_PUNCT_CHARS[subj->input.data[n]])
+      return n;
+    n++;
+  }
+
+  return subj->input.len;
+}
+
+// Parse an inline, advancing subject, and add it as a child of parent.
+// Return 0 if no inline can be parsed, 1 otherwise.
+static int parse_inline(subject *subj, cmark_node *parent, int options) {
+  cmark_node *new_inl = NULL;
+  cmark_chunk contents;
+  unsigned char c;
+  bufsize_t startpos, endpos;
+  c = peek_char(subj);
+  if (c == 0) {
+    return 0;
+  }
+  switch (c) {
+  case '\r':
+  case '\n':
+    new_inl = handle_newline(subj);
+    break;
+  case '`':
+    new_inl = handle_backticks(subj, options);
+    break;
+  case '\\':
+    new_inl = handle_backslash(subj);
+    break;
+  case '&':
+    new_inl = handle_entity(subj);
+    break;
+  case '<':
+    new_inl = handle_pointy_brace(subj, options);
+    break;
+  case '*':
+  case '_':
+  case '\'':
+  case '"':
+    new_inl = handle_delim(subj, c, (options & CMARK_OPT_SMART) != 0);
+    break;
+  case '-':
+    new_inl = handle_hyphen(subj, (options & CMARK_OPT_SMART) != 0);
+    break;
+  case '.':
+    new_inl = handle_period(subj, (options & CMARK_OPT_SMART) != 0);
+    break;
+  case '[':
+    advance(subj);
+    new_inl = make_str(subj, subj->pos - 1, subj->pos - 1, cmark_chunk_literal("["));
+    push_bracket(subj, false, new_inl);
+    break;
+  case ']':
+    new_inl = handle_close_bracket(subj);
+    break;
+  case '!':
+    advance(subj);
+    if (peek_char(subj) == '[') {
+      advance(subj);
+      new_inl = make_str(subj, subj->pos - 2, subj->pos - 1, cmark_chunk_literal("!["));
+      push_bracket(subj, true, new_inl);
+    } else {
+      new_inl = make_str(subj, subj->pos - 1, subj->pos - 1, cmark_chunk_literal("!"));
+    }
+    break;
+  default:
+    endpos = subject_find_special_char(subj, options);
+    contents = cmark_chunk_dup(&subj->input, subj->pos, endpos - subj->pos);
+    startpos = subj->pos;
+    subj->pos = endpos;
+
+    // if we're at a newline, strip trailing spaces.
+    if (S_is_line_end_char(peek_char(subj))) {
+      cmark_chunk_rtrim(&contents);
+    }
+
+    new_inl = make_str(subj, startpos, endpos - 1, contents);
+  }
+  if (new_inl != NULL) {
+    cmark_node_append_child(parent, new_inl);
+  }
+
+  return 1;
+}
+
+// Parse inlines from parent's string_content, adding as children of parent.
+void cmark_parse_inlines(cmark_mem *mem, cmark_node *parent,
+                         cmark_reference_map *refmap, int options) {
+  subject subj;
+  cmark_chunk content = {parent->data, parent->len};
+  subject_from_buf(mem, parent->start_line, parent->start_column - 1 + parent->internal_offset, &subj, &content, refmap);
+  cmark_chunk_rtrim(&subj.input);
+
+  while (!is_eof(&subj) && parse_inline(&subj, parent, options))
+    ;
+
+  process_emphasis(&subj, NULL);
+  // free bracket and delim stack
+  while (subj.last_delim) {
+    remove_delimiter(&subj, subj.last_delim);
+  }
+  while (subj.last_bracket) {
+    pop_bracket(&subj);
+  }
+}
+
+// Parse zero or more space characters, including at most one newline.
+static void spnl(subject *subj) {
+  skip_spaces(subj);
+  if (skip_line_end(subj)) {
+    skip_spaces(subj);
+  }
+}
+
+// Parse reference.  Assumes string begins with '[' character.
+// Modify refmap if a reference is encountered.
+// Return 0 if no reference found, otherwise position of subject
+// after reference is parsed.
+bufsize_t cmark_parse_reference_inline(cmark_mem *mem, cmark_chunk *input,
+                                       cmark_reference_map *refmap) {
+  subject subj;
+
+  cmark_chunk lab;
+  cmark_chunk url;
+  cmark_chunk title;
+
+  bufsize_t matchlen = 0;
+  bufsize_t beforetitle;
+
+  subject_from_buf(mem, -1, 0, &subj, input, NULL);
+
+  // parse label:
+  if (!link_label(&subj, &lab) || lab.len == 0)
+    return 0;
+
+  // colon:
+  if (peek_char(&subj) == ':') {
+    advance(&subj);
+  } else {
+    return 0;
+  }
+
+  // parse link url:
+  spnl(&subj);
+  if ((matchlen = manual_scan_link_url(&subj.input, subj.pos, &url)) > -1) {
+    subj.pos += matchlen;
+  } else {
+    return 0;
+  }
+
+  // parse optional link_title
+  beforetitle = subj.pos;
+  spnl(&subj);
+  matchlen = subj.pos == beforetitle ? 0 : scan_link_title(&subj.input, subj.pos);
+  if (matchlen) {
+    title = cmark_chunk_dup(&subj.input, subj.pos, matchlen);
+    subj.pos += matchlen;
+  } else {
+    subj.pos = beforetitle;
+    title = cmark_chunk_literal("");
+  }
+
+  // parse final spaces and newline:
+  skip_spaces(&subj);
+  if (!skip_line_end(&subj)) {
+    if (matchlen) { // try rewinding before title
+      subj.pos = beforetitle;
+      skip_spaces(&subj);
+      if (!skip_line_end(&subj)) {
+        return 0;
+      }
+    } else {
+      return 0;
+    }
+  }
+  // insert reference into refmap
+  cmark_reference_create(refmap, &lab, &url, &title);
+  return subj.pos;
+}