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markdown_lib.c - markdown in C using a PEG grammar.
(c) 2008 John MacFarlane (jgm at berkeley dot edu).
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License or the MIT
license. See LICENSE for details.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "markdown_peg.h"
#define TABSTOP 4
/* preformat_text - allocate and copy text buffer while
* performing tab expansion. */
static GString *preformat_text(char *text) {
GString *buf;
char next_char;
int charstotab;
int len = 0;
buf = g_string_new("");
charstotab = TABSTOP;
while ((next_char = *text++) != '\0') {
switch (next_char) {
case '\t':
while (charstotab > 0)
g_string_append_c(buf, ' '), len++, charstotab--;
case '\n':
g_string_append_c(buf, '\n'), len++, charstotab = TABSTOP;
g_string_append_c(buf, next_char), len++, charstotab--;
if (charstotab == 0)
charstotab = TABSTOP;
g_string_append(buf, "\n\n");
/* print_tree - print tree of elements, for debugging only. */
static void print_tree(element * elt, int indent) {
int i;
char * key;
while (elt != NULL) {
for (i = 0; i < indent; i++)
fputc(' ', stderr);
switch (elt->key) {
case LIST: key = "LIST"; break;
case RAW: key = "RAW"; break;
case SPACE: key = "SPACE"; break;
case LINEBREAK: key = "LINEBREAK"; break;
case ELLIPSIS: key = "ELLIPSIS"; break;
case EMDASH: key = "EMDASH"; break;
case ENDASH: key = "ENDASH"; break;
case APOSTROPHE: key = "APOSTROPHE"; break;
case STR: key = "STR"; break;
case LINK: key = "LINK"; break;
case IMAGE: key = "IMAGE"; break;
case CODE: key = "CODE"; break;
case HTML: key = "HTML"; break;
case EMPH: key = "EMPH"; break;
case STRONG: key = "STRONG"; break;
case PLAIN: key = "PLAIN"; break;
case PARA: key = "PARA"; break;
case LISTITEM: key = "LISTITEM"; break;
case BULLETLIST: key = "BULLETLIST"; break;
case ORDEREDLIST: key = "ORDEREDLIST"; break;
case H1: key = "H1"; break;
case H2: key = "H2"; break;
case H3: key = "H3"; break;
case H4: key = "H4"; break;
case H5: key = "H5"; break;
case H6: key = "H6"; break;
case BLOCKQUOTE: key = "BLOCKQUOTE"; break;
case VERBATIM: key = "VERBATIM"; break;
case HTMLBLOCK: key = "HTMLBLOCK"; break;
case HRULE: key = "HRULE"; break;
case REFERENCE: key = "REFERENCE"; break;
case NOTE: key = "NOTE"; break;
default: key = "?";
if ( elt->key == STR ) {
fprintf(stderr, "0x%x: %s '%s'\n", (int)elt, key, elt->contents.str);
} else {
fprintf(stderr, "0x%x: %s\n", (int)elt, key);
if (elt->children)
print_tree(elt->children, indent + 4);
elt = elt->next;
/* process_raw_blocks - traverses an element list, replacing any RAW elements with
* the result of parsing them as markdown text, and recursing into the children
* of parent elements. The result should be a tree of elements without any RAWs. */
static element * process_raw_blocks(element *input, int extensions, element *references, element *notes) {
element *current = NULL;
element *last_child = NULL;
char *contents;
current = input;
while (current != NULL) {
if (current->key == RAW) {
/* \001 is used to indicate boundaries between nested lists when there
* is no blank line. We split the string by \001 and parse
* each chunk separately. */
contents = strtok(current->contents.str, "\001");
current->key = LIST;
current->children = parse_markdown(contents, extensions, references, notes);
last_child = current->children;
while ((contents = strtok(NULL, "\001"))) {
while (last_child->next != NULL)
last_child = last_child->next;
last_child->next = parse_markdown(contents, extensions, references, notes);
current->contents.str = NULL;
if (current->children != NULL)
current->children = process_raw_blocks(current->children, extensions, references, notes);
current = current->next;
return input;
/* markdown_to_gstring - convert markdown text to the output format specified.
* Returns a GString, which must be freed after use using g_string_free(). */
GString * markdown_to_g_string(char *text, int extensions, int output_format) {
element *result;
element *references;
element *notes;
GString *formatted_text;
GString *out;
out = g_string_new("");
formatted_text = preformat_text(text);
references = parse_references(formatted_text->str, extensions);
notes = parse_notes(formatted_text->str, extensions, references);
result = parse_markdown(formatted_text->str, extensions, references, notes);
result = process_raw_blocks(result, extensions, references, notes);
g_string_free(formatted_text, TRUE);
print_element_list(out, result, output_format, extensions);
return out;
/* markdown_to_string - convert markdown text to the output format specified.
* Returns a null-terminated string, which must be freed after use. */
char * markdown_to_string(char *text, int extensions, int output_format) {
GString *out;
char *char_out;
out = markdown_to_g_string(text, extensions, output_format);
char_out = out->str;
g_string_free(out, FALSE);
return char_out;
/* vim:set ts=4 sw=4: */
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