json_out: new module for authoring JSON strings.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/json_out/LICENSE

+../../licenses/BSD-MIT
\ No newline at end of file

ccan/json_out/_info

+#include "config.h"
+#include <stdio.h>
+#include <string.h>
+
+/**
+ * json_out - Code for creating simple JSON output.
+ *
+ * This code helps you create well-formed JSON strings.
+ *
+ * Author: Rusty Russell <rusty@rustcorp.com.au>
+ * License: BSD-MIT
+ *
+ * Example:
+ *	// Given "a 1 true" outputs {"argv1":"a","argv2":1,"argv3":true}
+ *	// Print arguments as a JSON array.
+ *	#include <ccan/json_out/json_out.h>
+ *	#include <stdio.h>
+ *	#include <string.h>
+ *	#include <unistd.h>
+ *
+ *	// Simplistic test to see if str needs quotes.
+ *	static bool can_be_json_literal(const char *str)
+ *	{
+ *		char *endp;
+ *		if (strtol(str, &endp, 10) != LONG_MIN
+ *		    && endp != str
+ *		    && *endp == '\0')
+ *			return true;
+ *		return !strcmp(str, "true")
+ *			|| !strcmp(str, "false")
+ *			|| !strcmp(str, "null");
+ *	}
+ *		
+ *	int main(int argc, char *argv[])
+ *	{
+ *		struct json_out *jout = json_out_new(NULL);
+ *		size_t len;
+ *		const char *p;
+ *
+ *		json_out_start(jout, NULL, '{');
+ *		for (int i = 1; i < argc; i++) {
+ *			char fieldname[80];
+ *			sprintf(fieldname, "argv%i", i);
+ *			json_out_add(jout, fieldname,
+ *				     !can_be_json_literal(argv[i]),
+ *				     "%s", argv[i]);
+ *		}
+ *		json_out_end(jout, '}');
+ *		// Force appending of \n
+ *		json_out_direct(jout, 1)[0] = '\n';
+ *		json_out_finished(jout);
+ *
+ *		// Now write it out.
+ *		while ((p = json_out_contents(jout, &len)) != NULL) {
+ *			int i = write(STDOUT_FILENO, p, len);
+ *			if (i <= 0)
+ *				exit(1);
+ *			json_out_consume(jout, i);
+ *		}
+ *
+ *		tal_free(jout);
+ *		return 0;
+ *	}
+ *	
+ */
+int main(int argc, char *argv[])
+{
+	/* Expect exactly one argument */
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0) {
+		printf("ccan/compiler\n");
+		printf("ccan/json_escape\n");
+		printf("ccan/membuf\n");
+		printf("ccan/tal\n");
+		printf("ccan/typesafe_cb\n");
+		return 0;
+	}
+
+	return 1;
+}

ccan/json_out/json_out.c

+/* MIT (BSD) license - see LICENSE file for details */
+#include <ccan/json_escape/json_escape.h>
+#include <ccan/json_out/json_out.h>
+#include <ccan/membuf/membuf.h>
+#include <stdarg.h>
+#include <stdio.h>
+
+struct json_out {
+	/* Callback if we reallocate. */
+	void (*move_cb)(struct json_out *jout, ptrdiff_t delta, void *arg);
+	void *cb_arg;
+	
+#ifdef CCAN_JSON_OUT_DEBUG
+	/* tal_arr of types ( or [ we're enclosed in. */
+	char *wrapping;
+#endif
+	/* True if we haven't yet put an element in current wrapping */
+	bool empty;
+
+	/* Output. */
+	MEMBUF(char) outbuf;
+};
+
+/* Realloc helper for tal membufs */
+static void *membuf_tal_realloc(struct membuf *mb,
+				void *rawelems, size_t newsize)
+{
+	char *p = rawelems;
+
+	tal_resize(&p, newsize);
+	return p;
+}
+
+struct json_out *json_out_new(const tal_t *ctx)
+{
+	struct json_out *jout = tal(ctx, struct json_out);
+
+	membuf_init(&jout->outbuf,
+		    tal_arr(jout, char, 64), 64, membuf_tal_realloc);
+#ifdef CCAN_JSON_OUT_DEBUG
+	jout->wrapping = tal_arr(jout, char, 0);
+#endif
+	jout->empty = true;
+	jout->move_cb = NULL;
+	return jout;
+}
+
+void json_out_call_on_move_(struct json_out *jout,
+			    void (*cb)(struct json_out *jout, ptrdiff_t delta,
+				       void *arg),
+			    void *arg)
+{
+	if (cb)
+		assert(!jout->move_cb);
+	jout->move_cb = cb;
+	jout->cb_arg = arg;
+}
+
+struct json_out *json_out_dup(const tal_t *ctx, const struct json_out *src)
+{
+	size_t num_elems = membuf_num_elems(&src->outbuf);
+	char *elems = membuf_elems(&src->outbuf);
+	struct json_out *jout = tal_dup(ctx, struct json_out, src);
+	membuf_init(&jout->outbuf,
+		    tal_dup_arr(jout, char, elems, num_elems, 0),
+		    num_elems, membuf_tal_realloc);
+	membuf_added(&jout->outbuf, num_elems);
+#ifdef CCAN_JSON_OUT_DEBUG
+	jout->wrapping = tal_dup_arr(jout, char,
+				     jout->wrapping, tal_count(jout->wrapping),
+				     0);
+#endif
+	return jout;
+}
+
+static void indent(struct json_out *jout, char type)
+{
+#ifdef CCAN_JSON_OUT_DEBUG
+	size_t n = tal_count(jout->wrapping);
+	tal_resize(&jout->wrapping, n+1);
+	jout->wrapping[n] = type;
+#endif
+	jout->empty = true;
+}
+
+static void unindent(struct json_out *jout, char type)
+{
+#ifdef CCAN_JSON_OUT_DEBUG
+	size_t indent = tal_count(jout->wrapping);
+	assert(indent > 0);
+	/* Both [ and ] and { and } are two apart in ASCII */
+	assert(jout->wrapping[indent-1] == type - 2);
+	tal_resize(&jout->wrapping, indent-1);
+#endif
+	jout->empty = false;
+}
+
+/* Make sure jout->outbuf has room for len: return pointer */
+static char *mkroom(struct json_out *jout, size_t len)
+{
+	ptrdiff_t delta = membuf_prepare_space(&jout->outbuf, len);
+
+	if (delta && jout->move_cb)
+		jout->move_cb(jout, delta, jout->cb_arg);
+
+	return membuf_space(&jout->outbuf);
+}
+
+static void check_fieldname(const struct json_out *jout,
+			    const char *fieldname)
+{
+#ifdef CCAN_JSON_OUT_DEBUG
+	size_t n = tal_count(jout->wrapping);
+	if (n == 0)
+		/* Can't have a fieldname if not in anything! */
+		assert(!fieldname);
+	else if (jout->wrapping[n-1] == '[')
+		/* No fieldnames in arrays. */
+		assert(!fieldname);
+	else {
+		/* Must have fieldnames in objects. */
+		assert(fieldname);
+		/* We don't escape this for you */
+		assert(!json_escape_needed(fieldname, strlen(fieldname)));
+	}
+#endif
+}
+
+char *json_out_member_direct(struct json_out *jout,
+			     const char *fieldname, size_t extra)
+{
+	char *dest;
+
+	/* Prepend comma if required. */
+	if (!jout->empty)
+		extra++;
+
+	check_fieldname(jout, fieldname);
+	if (fieldname)
+		extra += 1 + strlen(fieldname) + 2;
+
+	if (!extra) {
+		dest = NULL;
+		goto out;
+	}
+
+	dest = mkroom(jout, extra);
+
+	if (!jout->empty)
+		*(dest++) = ',';
+	if (fieldname) {
+		*(dest++) = '"';
+		memcpy(dest, fieldname, strlen(fieldname));
+		dest += strlen(fieldname);
+		*(dest++) = '"';
+		*(dest++) = ':';
+	}
+	membuf_added(&jout->outbuf, extra);
+
+out:
+	jout->empty = false;
+	return dest;
+}
+
+void json_out_start(struct json_out *jout, const char *fieldname, char type)
+{
+	assert(type == '[' || type == '{');
+	json_out_member_direct(jout, fieldname, 1)[0] = type;
+	indent(jout, type);
+}
+
+void json_out_end(struct json_out *jout, char type)
+{
+	assert(type == '}' || type == ']');
+	json_out_direct(jout, 1)[0] = type;
+	unindent(jout, type);
+}
+
+void json_out_addv(struct json_out *jout,
+		   const char *fieldname,
+		   bool quote,
+		   const char *fmt,
+		   va_list ap)
+{
+	size_t fmtlen, avail;
+	va_list ap2;
+	char *dst;
+
+	json_out_member_direct(jout, fieldname, 0);
+
+	/* Make a copy in case we need it below. */
+	va_copy(ap2, ap);
+
+	/* We can use any additional space, but need room for ". */
+	avail = membuf_num_space(&jout->outbuf);
+	if (quote) {
+		if (avail < 2)
+			avail = 0;
+		else
+			avail -= 2;
+	}
+
+	/* Try printing in place first. */
+	dst = membuf_space(&jout->outbuf);
+	fmtlen = vsnprintf(dst + quote, avail, fmt, ap);
+
+	/* Horrible subtlety: vsnprintf *will* NUL terminate, even if it means
+	 * chopping off the last character.  So if fmtlen ==
+	 * membuf_num_space(&jout->outbuf), the result was truncated! */
+	if (fmtlen + (int)quote*2 >= membuf_num_space(&jout->outbuf)) {
+		/* Make room for NUL terminator, even though we don't want it */
+		dst = mkroom(jout, fmtlen + 1 + (int)quote*2);
+		vsprintf(dst + quote, fmt, ap2);
+	}
+
+	/* Of course, if we need to escape it, we have to redo it all. */
+	if (json_escape_needed(dst + quote, fmtlen)) {
+		struct json_escape *e;
+		e = json_escape_len(NULL, dst + quote, fmtlen);
+		fmtlen = strlen(e->s);
+		dst = mkroom(jout, fmtlen + (int)quote*2);
+		memcpy(dst + quote, e, fmtlen);
+		tal_free(e);
+	}
+
+	if (quote) {
+		dst[0] = '"';
+		dst[fmtlen+1] = '"';
+	}
+	membuf_added(&jout->outbuf, fmtlen + (int)quote*2);
+	va_end(ap2);
+}
+
+void json_out_add(struct json_out *jout,
+		  const char *fieldname,
+		  bool quote,
+		  const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	json_out_addv(jout, fieldname, quote, fmt, ap);
+	va_end(ap);
+}
+
+void json_out_addstr(struct json_out *jout,
+		     const char *fieldname,
+		     const char *str)
+{
+	size_t len = strlen(str);
+	char *p;
+
+	p = json_out_member_direct(jout, fieldname, len + 2);
+	p[0] = p[1+len] = '"';
+	memcpy(p+1, str, len);
+}
+
+void json_out_add_splice(struct json_out *jout,
+			 const char *fieldname,
+			 const struct json_out *src)
+{
+	const char *p;
+	size_t len;
+
+	p = json_out_contents(src, &len);
+	memcpy(json_out_member_direct(jout, fieldname, len), p, len);
+}
+
+char *json_out_direct(struct json_out *jout, size_t len)
+{
+	char *p = mkroom(jout, len);
+	membuf_added(&jout->outbuf, len);
+	return p;
+}
+
+void json_out_finished(const struct json_out *jout)
+{
+#ifdef CCAN_JSON_OUT_DEBUG
+	assert(tal_count(jout->wrapping) == 0);
+#endif
+}
+
+const char *json_out_contents(const struct json_out *jout, size_t *len)
+{
+	*len = membuf_num_elems(&jout->outbuf);
+	return *len ? membuf_elems(&jout->outbuf) : NULL;
+}
+
+void json_out_consume(struct json_out *jout, size_t len)
+{
+	membuf_consume(&jout->outbuf, len);
+}

ccan/json_out/json_out.h

+/* MIT (BSD) license - see LICENSE file for details */
+#ifndef CCAN_JSON_OUT_H
+#define CCAN_JSON_OUT_H
+#include <ccan/compiler/compiler.h>
+#include <ccan/tal/tal.h>
+#include <ccan/typesafe_cb/typesafe_cb.h>
+#include <stddef.h>
+
+struct json_out;
+
+/**
+ * json_out_new - allocate a json_out stream.
+ * @ctx: the tal_context to allocate from, or NULL
+ */
+struct json_out *json_out_new(const tal_t *ctx);
+
+/**
+ * json_out_call_on_move - callback for when buffer is reallocated.
+ * @jout: the json_out object to attach to.
+ * @cb: the callback to call.
+ * @arg: the argument to @cb (must match type).
+ *
+ * A NULL @cb disables.  You can't currently have more than one callback.
+ * The @delta argument to @cb is the difference between the old location
+ * and the new one, and is never zero.
+ */
+#define json_out_call_on_move(jout, cb, arg)				\
+	json_out_call_on_move_((jout),					\
+			       typesafe_cb_preargs(void, void *,	\
+						   (cb), (arg),		\
+						   struct json_out *,	\
+						   ptrdiff_t),		\
+			       (arg))
+
+void json_out_call_on_move_(struct json_out *jout,
+			    void (*cb)(struct json_out *jout, ptrdiff_t delta,
+				       void *arg),
+			    void *arg);
+
+/**
+ * json_out_dup - duplicate a json_out stream.
+ * @ctx: the tal_context to allocate from, or NULL
+ * @src: the json_out to copy.
+ */
+struct json_out *json_out_dup(const tal_t *ctx, const struct json_out *src);
+
+/**
+ * json_out_start - start an array or object.
+ * @jout: the json_out object to write into.
+ * @fieldname: the fieldname, if inside an object, or NULL if inside an array.
+ * @type: '[' or '{' to start an array or object, respectively.
+ *
+ * Literally writes '"@fieldname": @type' or '@type ' if fieldname is NULL.
+ * @fieldname must not need JSON escaping.
+ */
+void json_out_start(struct json_out *jout, const char *fieldname, char type);
+
+/**
+ * json_out_end - end an array or object.
+ * @jout: the json_out object to write into.
+ * @type: '}' or ']' to end an array or object, respectively.
+ *
+ * Literally writes ']' or '}', keeping track of whether we need to append
+ * a comma.
+ */
+void json_out_end(struct json_out *jout, char type);
+
+/**
+ * json_out_add - add a formatted member.
+ * @jout: the json_out object to write into.
+ * @fieldname: optional fieldname to prepend (must not need escaping).
+ * @quote: if true, surround fmt by " and ".
+ * @fmt...: the printf-style format
+ *
+ * If you're in an array, @fieldname must be NULL.  If you're in an
+ * object, @fieldname must be non-NULL.  This is checked if
+ * CCAN_JSON_OUT_DEBUG is defined.
+ * @fieldname must not need JSON escaping.
+ *
+ * If the resulting string requires escaping, we call json_escape().
+ */
+PRINTF_FMT(4,5)
+void json_out_add(struct json_out *jout,
+		  const char *fieldname,
+		  bool quote,
+		  const char *fmt, ...);
+
+/**
+ * json_out_addv - add a formatted member (vararg variant)
+ * @jout: the json_out object to write into.
+ * @fieldname: optional fieldname to prepend.
+ * @quote: if true, surround fmt by " and ".
+ * @fmt: the printf-style format
+ * @ap: the argument list.
+ *
+ * See json_out_add() above.
+ */
+void json_out_addv(struct json_out *jout,
+		   const char *fieldname,
+		   bool quote,
+		   const char *fmt,
+		   va_list ap);
+
+/**
+ * json_out_addstr - convenience helper to add a string field.
+ * @jout: the json_out object to write into.
+ * @fieldname: optional fieldname to prepend.
+ * @str: the string to add (must not be NULL).
+ *
+ * Equivalent to json_out_add(@jout, @fieldname, true, "%s", @str);
+ */
+void json_out_addstr(struct json_out *jout,
+		     const char *fieldname,
+		     const char *str);
+
+/**
+ * json_out_member_direct - add a field, with direct access.
+ * @jout: the json_out object to write into.
+ * @fieldname: optional fieldname to prepend.
+ * @extra: how many bytes to allocate.
+ *
+ * @fieldname must not need JSON escaping.  Returns a direct pointer into
+ * the @extra bytes.
+ *
+ * This allows you to write your own efficient type-specific helpers.
+ */
+char *json_out_member_direct(struct json_out *jout,
+			     const char *fieldname, size_t extra);
+
+/**
+ * json_out_direct - make room in output and access directly.
+ * @jout: the json_out object to write into.
+ * @len: the length to allocate.
+ *
+ * This lets you access the json_out stream directly, to save a copy,
+ * if you know exactly how much you will write.
+ *
+ * Returns a pointer to @len bytes at the end of @jout.
+ *
+ * This is dangerous, since it doesn't automatically prepend a ","
+ * like the internal logic does, but can be used (carefully) to add
+ * entire objects, or whitespace.
+ */
+char *json_out_direct(struct json_out *jout, size_t extra);
+
+/**
+ * json_out_add_splice - copy a field from another json_out.
+ * @jout: the json_out object to write into.
+ * @fieldname: optional fieldname to prepend.
+ * @src: the json_out object to copy from.
+ *
+ * This asserts that @src is well-formed (as per json_out_finished()),
+ * then places it into @jout with optional @fieldname prepended.  This
+ * can be used to assemble sub-objects for your JSON and then copy
+ * them in.
+ *
+ * Note that it will call json_out_contents(@src), so it expects that
+ * object to be unconsumed.
+ */
+void json_out_add_splice(struct json_out *jout,
+			 const char *fieldname,
+			 const struct json_out *src);
+
+/**
+ * json_out_finished - assert that the json buffer is finished.
+ * @jout: the json_out object written to.
+ *
+ * This simply causes internal assertions that all arrays and objects are
+ * finished.  It needs CCAN_JSON_OUT_DEBUG defined to have any effect.
+ */
+void json_out_finished(const struct json_out *jout);
+
+/**
+ * json_out_contents - read contents from json_out stream.
+ * @jout: the json_out object we want to read from.
+ * @len: set to the length of the buffer returned.
+ *
+ * This returns a pointer into the JSON written so far.  Returns NULL
+ * and sets @len to 0 if there's nothing left in the buffer.
+ */
+const char *json_out_contents(const struct json_out *jout, size_t *len);
+
+/**
+ * json_out_consume - discard contents from json_out stream.
+ * @jout: the json_out object we read from.
+ * @len: the length to consume (must be <= @len from json_out_contents)
+ */
+void json_out_consume(struct json_out *jout, size_t len);
+#endif /* CCAN_JSON_OUT_H */

ccan/json_out/test/run-debugging.c

+#define CCAN_JSON_OUT_DEBUG 1
+#include "run.c"

ccan/json_out/test/run-move_cb.c

+#include <ccan/json_out/json_out.h>
+/* Include the C files directly. */
+#include <ccan/json_out/json_out.c>
+#include <ccan/tap/tap.h>
+
+static const char *ptr;
+static bool called = false;
+
+static void move_cb(struct json_out *jout, ptrdiff_t delta,
+		    struct json_out *arg)
+{
+	ptr += delta;
+	called = true;
+	ok1(arg == jout);
+}
+
+int main(void)
+{
+	const tal_t *ctx = tal(NULL, char);
+	struct json_out *jout;
+	char *p;
+	size_t len;
+
+	/* This is how many tests you plan to run */
+	plan_tests(3);
+
+	/* Test nested arrays. */
+	jout = json_out_new(ctx);
+	json_out_call_on_move(jout, move_cb, jout);
+
+	json_out_start(jout, NULL, '{');
+	ptr = json_out_contents(jout, &len);
+
+	p = json_out_member_direct(jout, "fieldname", 102);
+	p[0] = '"';
+	p[101] = '"';
+	memset(p+1, 'p', 100);
+
+	json_out_finished(jout);
+	ok1(called);
+	/* Contents should have moved correctly. */
+	ok1(json_out_contents(jout, &len) == ptr);
+
+	tal_free(ctx);
+
+	/* This exits depending on whether all tests passed */
+	return exit_status();
+}

ccan/json_out/test/run.c

+#include <ccan/json_out/json_out.h>
+/* Include the C files directly. */
+#include <ccan/json_out/json_out.c>
+#include <ccan/tap/tap.h>
+
+static void test_json_out_add(const tal_t *ctx,
+			      char c, bool quote, const char *escaped)
+{
+	/* 64 is the size of the initial buf, so we test that. */
+	for (size_t i = 1; i < 64; i++) {
+		struct json_out *jout;
+		char str[64 + 1];
+		const char *r;
+		size_t len;
+		char fieldname[64 + 1];
+
+		jout = json_out_new(ctx);
+		json_out_start(jout, NULL, '{');
+		memset(str, c, i);
+		str[i] = '\0';
+		memset(fieldname, 'f', i);
+		fieldname[i] = '\0';
+		json_out_add(jout, fieldname, quote, "%s", str);
+		json_out_end(jout, '}');
+		json_out_finished(jout);
+
+		r = json_out_contents(jout, &len);
+		ok1(len == strlen("{\"") + i + strlen("\":")
+		    + quote * 2 + strlen(escaped) * i + strlen("}"));
+
+		ok1(len > strlen("{\""));
+		ok1(memcmp(r, "{\"", strlen("{\"")) == 0);
+		json_out_consume(jout, strlen("{\""));
+
+		r = json_out_contents(jout, &len);
+		ok1(len > strlen(fieldname));
+		ok1(memcmp(r, fieldname, strlen(fieldname)) == 0);
+		json_out_consume(jout, strlen(fieldname));
+
+		r = json_out_contents(jout, &len);
+		ok1(len > strlen("\":"));
+		ok1(memcmp(r, "\":", strlen("\":")) == 0);
+		json_out_consume(jout, strlen("\":"));
+
+		r = json_out_contents(jout, &len);
+		if (quote) {
+			ok1(len > 0);
+			ok1(r[0] == '"');
+			json_out_consume(jout, 1);
+		}
+		for (size_t n = 0; n < i; n++) {
+			r = json_out_contents(jout, &len);
+			ok1(len > strlen(escaped));
+			ok1(memcmp(r, escaped, strlen(escaped)) == 0);
+			json_out_consume(jout, strlen(escaped));
+		}
+		r = json_out_contents(jout, &len);
+		if (quote) {
+			ok1(len > 0);
+			ok1(r[0] == '"');
+			json_out_consume(jout, 1);
+		}
+		r = json_out_contents(jout, &len);
+		ok1(len == 1);
+		ok1(memcmp(r, "}", 1) == 0);
+		json_out_consume(jout, 1);
+		ok1(!json_out_contents(jout, &len));
+		ok1(len == 0);
+	}
+}
+
+static void json_eq(const struct json_out *jout, const char *expect)
+{
+	size_t len;
+	const char *p;
+
+	json_out_finished(jout);
+	p = json_out_contents(jout, &len);
+	ok1(len == strlen(expect));
+	ok1(memcmp(expect, p, len) == 0);
+}
+	
+int main(void)
+{
+	const tal_t *ctx = tal(NULL, char);
+	struct json_out *jout;
+	char *p;
+
+	/* This is how many tests you plan to run */
+	plan_tests(14689);
+
+	/* Simple tests */
+	test_json_out_add(ctx, '1', false, "1");
+	test_json_out_add(ctx, 'x', true, "x");
+	test_json_out_add(ctx, '\n', true, "\\n");
+
+	/* Test nested arrays. */
+	jout = json_out_new(ctx);
+	for (size_t i = 0; i < 64; i++)
+		json_out_start(jout, NULL, '[');
+	for (size_t i = 0; i < 64; i++)
+		json_out_end(jout, ']');
+	json_eq(jout, "[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]");
+
+	/* Test nested objects. */
+	jout = json_out_new(ctx);
+	json_out_start(jout, NULL, '{');
+	for (size_t i = 0; i < 63; i++)
+		json_out_start(jout, "x", '{');
+	for (size_t i = 0; i < 64; i++)
+		json_out_end(jout, '}');
+	json_eq(jout, "{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{\"x\":{}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}");
+
+	jout = json_out_new(ctx);
+	json_out_start(jout, NULL, '{');
+	p = json_out_member_direct(jout, "x", 7);
+	memcpy(p, "\"hello\"", 7);
+	json_out_end(jout, '}');
+	json_eq(jout, "{\"x\":\"hello\"}");
+
+	jout = json_out_new(ctx);
+	p = json_out_direct(jout, strlen("{\"x\":\"hello\"}\n"));
+	memcpy(p, "{\"x\":\"hello\"}\n", strlen("{\"x\":\"hello\"}\n"));
+	json_eq(jout, "{\"x\":\"hello\"}\n");
+
+	jout = json_out_new(ctx);
+	json_out_start(jout, NULL, '{');
+	struct json_out *jout2 = json_out_new(ctx);
+	json_out_start(jout2, NULL, '{');
+	json_out_addstr(jout2, "x", "hello");
+	json_out_end(jout2, '}');
+	json_out_finished(jout2);
+	json_out_add_splice(jout, "inner", jout2);
+	json_out_end(jout, '}');
+	json_eq(jout, "{\"inner\":{\"x\":\"hello\"}}");
+
+	tal_free(ctx);
+
+	/* This exits depending on whether all tests passed */
+	return exit_status();
+}