Add json_sprintf and json_vsprintf

Fixes #392

CMakeLists.txt

@@ -496,6 +496,7 @@ if (NOT JANSSON_WITHOUT_TESTS)
          test_object
          test_pack
          test_simple
+         test_sprintf
          test_unpack)
 
    # Doing arithmetic on void pointers is not allowed by Microsofts compiler

doc/apiref.rst

@@ -399,6 +399,16 @@ length-aware functions if you wish to embed null bytes in strings.
 
    .. versionadded:: 2.7
 
+.. function:: json_t *json_sprintf(const char *format, ...)
+              json_t *json_vsprintf(const char *format, va_list ap)
+
+   .. refcounting:: new
+
+   Construct a JSON string from a format string and varargs, just like
+   :func:`printf()`.
+
+   .. versionadded:: 2.11
+
 
 Number
 ======

src/jansson.def

@@ -3,6 +3,8 @@ EXPORTS
     json_true
     json_false
     json_null
+    json_sprintf
+    json_vsprintf
     json_string
     json_stringn
     json_string_nocheck

src/jansson.h

@@ -289,6 +289,11 @@ int json_unpack(json_t *root, const char *fmt, ...);
 int json_unpack_ex(json_t *root, json_error_t *error, size_t flags, const char *fmt, ...);
 int json_vunpack_ex(json_t *root, json_error_t *error, size_t flags, const char *fmt, va_list ap);
 
+/* sprintf */
+
+json_t *json_sprintf(const char *fmt, ...);
+json_t *json_vsprintf(const char *fmt, va_list ap);
+
 
 /* equality */
 

src/value.c

@@ -787,6 +787,40 @@ static json_t *json_string_copy(const json_t *string)
     return json_stringn_nocheck(s->value, s->length);
 }
 
+json_t *json_vsprintf(const char *fmt, va_list ap) {
+    int length;
+    char *buf;
+    va_list aq;
+    va_copy(aq, ap);
+
+    length = vsnprintf(NULL, 0, fmt, ap);
+    if (length == 0)
+        return json_string("");
+
+    buf = jsonp_malloc(length + 1);
+    if (!buf)
+        return NULL;
+
+    vsnprintf(buf, length + 1, fmt, aq);
+    if (!utf8_check_string(buf, length)) {
+        jsonp_free(buf);
+        return NULL;
+    }
+
+    return jsonp_stringn_nocheck_own(buf, length);
+}
+
+json_t *json_sprintf(const char *fmt, ...) {
+    json_t *result;
+    va_list ap;
+
+    va_start(ap, fmt);
+    result = json_vsprintf(fmt, ap);
+    va_end(ap);
+
+    return result;
+}
+
 
 /*** integer ***/
 

test/.gitignore

@@ -7,14 +7,15 @@ suites/api/test_dump
 suites/api/test_dump_callback
 suites/api/test_equal
 suites/api/test_load
+suites/api/test_load_callback
 suites/api/test_loadb
 suites/api/test_memory_funcs
 suites/api/test_number
 suites/api/test_object
 suites/api/test_pack
 suites/api/test_simple
+suites/api/test_sprintf
 suites/api/test_unpack
-suites/api/test_load_callback
 run-suites.log
 run-suites.trs
 test-suite.log

test/suites/api/Makefile.am

@@ -14,6 +14,7 @@ check_PROGRAMS = \
 	test_object \
 	test_pack \
 	test_simple \
+	test_sprintf \
 	test_unpack
 
 test_array_SOURCES = test_array.c util.h
@@ -27,6 +28,7 @@ test_number_SOURCES = test_number.c util.h
 test_object_SOURCES = test_object.c util.h
 test_pack_SOURCES = test_pack.c util.h
 test_simple_SOURCES = test_simple.c util.h
+test_sprintf_SOURCES = test_sprintf.c util.h
 test_unpack_SOURCES = test_unpack.c util.h
 
 AM_CPPFLAGS = -I$(top_builddir)/src -I$(top_srcdir)/src

test/suites/api/test_sprintf.c

@@ -0,0 +1,22 @@
+#include <string.h>
+#include <jansson.h>
+#include "util.h"
+
+
+static void test_sprintf() {
+    json_t *s = json_sprintf("foo bar %d", 42);
+    if (!s)
+        fail("json_sprintf returned NULL");
+    if (!json_is_string(s))
+        fail("json_sprintf didn't return a JSON string");
+    if (strcmp(json_string_value(s), "foo bar 42"))
+        fail("json_sprintf generated an unexpected string");
+
+    json_decref(s);
+}
+
+
+static void run_tests()
+{
+    test_sprintf();
+}