new file mode 100644
--- /dev/null
+++ b/src/json.c
@@ -0,0 +1,509 @@
+/* vi:set ts=8 sts=4 sw=4:
+ *
+ * VIM - Vi IMproved	by Bram Moolenaar
+ *
+ * Do ":help uganda"  in Vim to read copying and usage conditions.
+ * Do ":help credits" in Vim to see a list of people who contributed.
+ * See README.txt for an overview of the Vim source code.
+ */
+
+/*
+ * json.c: Encoding and decoding JSON.
+ *
+ * Follows this standard: http://www.ietf.org/rfc/rfc4627.txt
+ */
+
+#include "vim.h"
+
+#if defined(FEAT_EVAL) || defined(PROTO)
+static void json_decode_item(js_read_T *reader, typval_T *res);
+
+/*
+ * Encode "val" into a JSON format string.
+ */
+    char_u *
+json_encode(typval_T *val)
+{
+    garray_T ga;
+
+    /* Store bytes in the growarray. */
+    ga_init2(&ga, 1, 4000);
+    json_encode_item(&ga, val, get_copyID());
+    return ga.ga_data;
+}
+
+    static void
+write_string(garray_T *gap, char_u *str)
+{
+    char_u	*res = str;
+    char_u	numbuf[NUMBUFLEN];
+
+    if (res == NULL)
+	ga_concat(gap, (char_u *)"null");
+    else
+    {
+	ga_append(gap, '"');
+	while (*res != NUL)
+	{
+	    int c = PTR2CHAR(res);
+
+	    switch (c)
+	    {
+		case 0x08:
+		    ga_append(gap, '\\'); ga_append(gap, 'b'); break;
+		case 0x09:
+		    ga_append(gap, '\\'); ga_append(gap, 't'); break;
+		case 0x0a:
+		    ga_append(gap, '\\'); ga_append(gap, 'n'); break;
+		case 0x0c:
+		    ga_append(gap, '\\'); ga_append(gap, 'f'); break;
+		case 0x0d:
+		    ga_append(gap, '\\'); ga_append(gap, 'r'); break;
+		case 0x22: /* " */
+		case 0x5c: /* \ */
+		    ga_append(gap, '\\');
+		    ga_append(gap, c);
+		    break;
+		default:
+		    if (c >= 0x20)
+		    {
+			numbuf[mb_char2bytes(c, numbuf)] = NUL;
+			ga_concat(gap, numbuf);
+		    }
+		    else
+		    {
+			vim_snprintf((char *)numbuf, NUMBUFLEN,
+							 "\\u%04lx", (long)c);
+			ga_concat(gap, numbuf);
+		    }
+	    }
+	    mb_cptr_adv(res);
+	}
+	ga_append(gap, '"');
+    }
+}
+
+    void
+json_encode_item(garray_T *gap, typval_T *val, int copyID)
+{
+    char_u	numbuf[NUMBUFLEN];
+    char_u	*res;
+    list_T	*l;
+    dict_T	*d;
+
+    switch (val->v_type)
+    {
+	case VAR_SPECIAL:
+	    switch(val->vval.v_number)
+	    {
+		case VVAL_FALSE: ga_concat(gap, (char_u *)"false"); break;
+		case VVAL_TRUE: ga_concat(gap, (char_u *)"true"); break;
+		case VVAL_NONE: break;
+		case VVAL_NULL: ga_concat(gap, (char_u *)"null"); break;
+	    }
+	    break;
+
+	case VAR_NUMBER:
+	    vim_snprintf((char *)numbuf, NUMBUFLEN, "%ld",
+						    (long)val->vval.v_number);
+	    ga_concat(gap, numbuf);
+	    break;
+
+	case VAR_STRING:
+	    res = val->vval.v_string;
+	    write_string(gap, res);
+	    break;
+
+	case VAR_FUNC:
+	    /* no JSON equivalent, skip */
+	    break;
+
+	case VAR_LIST:
+	    l = val->vval.v_list;
+	    if (l == NULL)
+		ga_concat(gap, (char_u *)"null");
+	    else
+	    {
+		if (l->lv_copyID == copyID)
+		    ga_concat(gap, (char_u *)"[]");
+		else
+		{
+		    listitem_T	*li;
+
+		    l->lv_copyID = copyID;
+		    ga_append(gap, '[');
+		    for (li = l->lv_first; li != NULL && !got_int; )
+		    {
+			json_encode_item(gap, &li->li_tv, copyID);
+			li = li->li_next;
+			if (li != NULL)
+			    ga_append(gap, ',');
+		    }
+		    ga_append(gap, ']');
+		}
+	    }
+	    break;
+
+	case VAR_DICT:
+	    d = val->vval.v_dict;
+	    if (d == NULL)
+		ga_concat(gap, (char_u *)"null");
+	    else
+	    {
+		if (d->dv_copyID == copyID)
+		    ga_concat(gap, (char_u *)"{}");
+		else
+		{
+		    int		first = TRUE;
+		    int		todo = (int)d->dv_hashtab.ht_used;
+		    hashitem_T	*hi;
+
+		    d->dv_copyID = copyID;
+		    ga_append(gap, '{');
+
+		    for (hi = d->dv_hashtab.ht_array; todo > 0 && !got_int;
+									 ++hi)
+			if (!HASHITEM_EMPTY(hi))
+			{
+			    --todo;
+			    if (first)
+				first = FALSE;
+			    else
+				ga_append(gap, ',');
+			    write_string(gap, hi->hi_key);
+			    ga_append(gap, ':');
+			    json_encode_item(gap, &dict_lookup(hi)->di_tv,
+								      copyID);
+			}
+		    ga_append(gap, '}');
+		}
+	    }
+	    break;
+
+#ifdef FEAT_FLOAT
+	case VAR_FLOAT:
+	    vim_snprintf((char *)numbuf, NUMBUFLEN, "%g", val->vval.v_float);
+	    ga_concat(gap, numbuf);
+	    break;
+#endif
+	default: EMSG2(_(e_intern2), "json_encode_item()"); break;
+    }
+}
+
+/*
+ * Skip white space in "reader".
+ */
+    static void
+json_skip_white(js_read_T *reader)
+{
+    int c;
+
+    while ((c = reader->js_buf[reader->js_used]) == ' '
+					   || c == TAB || c == NL || c == CAR)
+	++reader->js_used;
+}
+
+/*
+ * Make sure there are at least enough characters buffered to read a number.
+ */
+    static void
+json_fill_buffer(js_read_T *reader UNUSED)
+{
+    /* TODO */
+}
+
+    static void
+json_decode_array(js_read_T *reader, typval_T *res)
+{
+    char_u	*p;
+    typval_T	item;
+    listitem_T	*li;
+
+    if (rettv_list_alloc(res) == FAIL)
+	goto fail;
+    ++reader->js_used; /* consume the '[' */
+
+    while (TRUE)
+    {
+	json_skip_white(reader);
+	p = reader->js_buf + reader->js_used;
+	if (*p == NUL)
+	    goto fail;
+	if (*p == ']')
+	{
+	    ++reader->js_used; /* consume the ']' */
+	    return;
+	}
+
+	if (!reader->js_eof && (int)(reader->js_end - p) < NUMBUFLEN)
+	    json_fill_buffer(reader);
+
+	json_decode_item(reader, &item);
+	li = listitem_alloc();
+	if (li == NULL)
+	    return;
+	li->li_tv = item;
+	list_append(res->vval.v_list, li);
+
+	json_skip_white(reader);
+	p = reader->js_buf + reader->js_used;
+	if (*p == ',')
+	    ++reader->js_used;
+	else if (*p != ']')
+	    goto fail;
+    }
+fail:
+    res->v_type = VAR_SPECIAL;
+    res->vval.v_number = VVAL_NONE;
+}
+
+    static void
+json_decode_object(js_read_T *reader, typval_T *res)
+{
+    char_u	*p;
+    typval_T	tvkey;
+    typval_T	item;
+    dictitem_T	*di;
+    char_u	buf[NUMBUFLEN];
+    char_u	*key;
+
+    if (rettv_dict_alloc(res) == FAIL)
+	goto fail;
+    ++reader->js_used; /* consume the '{' */
+
+    while (TRUE)
+    {
+	json_skip_white(reader);
+	p = reader->js_buf + reader->js_used;
+	if (*p == NUL)
+	    goto fail;
+	if (*p == '}')
+	{
+	    ++reader->js_used; /* consume the '}' */
+	    return;
+	}
+
+	if (!reader->js_eof && (int)(reader->js_end - p) < NUMBUFLEN)
+	    json_fill_buffer(reader);
+	json_decode_item(reader, &tvkey);
+	key = get_tv_string_buf_chk(&tvkey, buf);
+	if (key == NULL || *key == NUL)
+	{
+	    /* "key" is NULL when get_tv_string_buf_chk() gave an errmsg */
+	    if (key != NULL)
+		EMSG(_(e_emptykey));
+	    clear_tv(&tvkey);
+	    goto fail;
+	}
+
+	json_skip_white(reader);
+	p = reader->js_buf + reader->js_used;
+	if (*p != ':')
+	{
+	    clear_tv(&tvkey);
+	    goto fail;
+	}
+	++reader->js_used;
+	json_skip_white(reader);
+
+	if (!reader->js_eof && (int)(reader->js_end - p) < NUMBUFLEN)
+	    json_fill_buffer(reader);
+	json_decode_item(reader, &item);
+
+	di = dictitem_alloc(key);
+	clear_tv(&tvkey);
+	if (di == NULL)
+	{
+	    clear_tv(&item);
+	    goto fail;
+	}
+	di->di_tv = item;
+	dict_add(res->vval.v_dict, di);
+
+	json_skip_white(reader);
+	p = reader->js_buf + reader->js_used;
+	if (*p == ',')
+	    ++reader->js_used;
+	else if (*p != '}')
+	    goto fail;
+    }
+fail:
+    res->v_type = VAR_SPECIAL;
+    res->vval.v_number = VVAL_NONE;
+}
+
+    static void
+json_decode_string(js_read_T *reader, typval_T *res)
+{
+    garray_T    ga;
+    int		len;
+    char_u	*p = reader->js_buf + reader->js_used + 1;
+    int		c;
+    long	nr;
+    char_u	buf[NUMBUFLEN];
+
+    ga_init2(&ga, 1, 200);
+
+    /* TODO: fill buffer when needed. */
+    while (*p != NUL && *p != '"')
+    {
+	if (*p == '\\')
+	{
+	    c = -1;
+	    switch (p[1])
+	    {
+		case 'b': c = BS; break;
+		case 't': c = TAB; break;
+		case 'n': c = NL; break;
+		case 'f': c = FF; break;
+		case 'r': c = CAR; break;
+		case 'u':
+		    vim_str2nr(p + 2, NULL, &len,
+				     STR2NR_HEX + STR2NR_FORCE, &nr, NULL, 4);
+		    p += len + 2;
+#ifdef FEAT_MBYTE
+		    buf[(*mb_char2bytes)((int)nr, buf)] = NUL;
+		    ga_concat(&ga, buf);
+#else
+		    ga_append(&ga, nr);
+#endif
+		    break;
+		default: c = p[1]; break;
+	    }
+	    if (c > 0)
+	    {
+		p += 2;
+		ga_append(&ga, c);
+	    }
+	}
+	else
+	{
+	    len = MB_PTR2LEN(p);
+	    if (ga_grow(&ga, len) == OK)
+	    {
+		mch_memmove((char *)ga.ga_data + ga.ga_len, p, (size_t)len);
+		ga.ga_len += len;
+	    }
+	    p += len;
+	}
+	if (!reader->js_eof && (int)(reader->js_end - p) < NUMBUFLEN)
+	{
+	    reader->js_used = (int)(p - reader->js_buf);
+	    json_fill_buffer(reader);
+	    p = reader->js_buf + reader->js_used;
+	}
+    }
+    reader->js_used = (int)(p - reader->js_buf);
+    if (*p == '"')
+    {
+	++reader->js_used;
+	res->v_type = VAR_STRING;
+	res->vval.v_string = vim_strsave(ga.ga_data);
+    }
+    else
+    {
+	res->v_type = VAR_SPECIAL;
+	res->vval.v_number = VVAL_NONE;
+    }
+    ga_clear(&ga);
+}
+
+/*
+ * Decode one item and put it in "result".
+ * Must already have skipped white space.
+ */
+    static void
+json_decode_item(js_read_T *reader, typval_T *res)
+{
+    char_u	*p = reader->js_buf + reader->js_used;
+
+    switch (*p)
+    {
+	case '[': /* array */
+	    json_decode_array(reader, res);
+	    return;
+
+	case '{': /* object */
+	    json_decode_object(reader, res);
+	    return;
+
+	case '"': /* string */
+	    json_decode_string(reader, res);
+	    return;
+
+	case ',': /* comma: empty item */
+	case NUL: /* empty */
+	    res->v_type = VAR_SPECIAL;
+	    res->vval.v_number = VVAL_NONE;
+	    return;
+
+	default:
+	    if (VIM_ISDIGIT(*p) || *p == '-')
+	    {
+		int	len;
+		char_u  *sp = p;
+#ifdef FEAT_FLOAT
+		if (*sp == '-')
+		    ++sp;
+		sp = skipdigits(sp);
+		if (*sp == '.' || *sp == 'e' || *sp == 'E')
+		{
+		    res->v_type = VAR_FLOAT;
+		    len = string2float(p, &res->vval.v_float);
+		}
+		else
+#endif
+		{
+		    long nr;
+
+		    res->v_type = VAR_NUMBER;
+		    vim_str2nr(reader->js_buf + reader->js_used,
+			    NULL, &len, 0, /* what */
+			    &nr, NULL, 0);
+		    res->vval.v_number = nr;
+		}
+		reader->js_used += len;
+		return;
+	    }
+	    if (STRNICMP((char *)p, "false", 5) == 0)
+	    {
+		reader->js_used += 5;
+		res->v_type = VAR_SPECIAL;
+		res->vval.v_number = VVAL_FALSE;
+		return;
+	    }
+	    if (STRNICMP((char *)p, "true", 4) == 0)
+	    {
+		reader->js_used += 4;
+		res->v_type = VAR_SPECIAL;
+		res->vval.v_number = VVAL_TRUE;
+		return;
+	    }
+	    if (STRNICMP((char *)p, "null", 4) == 0)
+	    {
+		reader->js_used += 4;
+		res->v_type = VAR_SPECIAL;
+		res->vval.v_number = VVAL_NULL;
+		return;
+	    }
+	    break;
+    }
+
+    EMSG(_(e_invarg));
+    res->v_type = VAR_SPECIAL;
+    res->vval.v_number = VVAL_NONE;
+}
+
+/*
+ * Decode the JSON from "reader" and store the result in "res".
+ */
+    void
+json_decode(js_read_T *reader, typval_T *res)
+{
+    json_skip_white(reader);
+    json_decode_item(reader, res);
+    json_skip_white(reader);
+    if (reader->js_buf[reader->js_used] != NUL)
+	EMSG(_(e_invarg));
+}
+#endif