Add functions for shallow and deep copying JSON values

doc/apiref.rst

@@ -713,3 +713,35 @@ equal.
    *NULL*.
 
    .. versionadded:: 1.2
+
+
+Copying
+=======
+
+Because of reference counting, passing JSON values around doesn't
+require copying them. But sometimes a fresh copy of a JSON value is
+needed. For example, if you need to modify an array, but still want to
+use the original afterwards, you should take a copy of it first.
+
+Jansson supports two kinds of copying: shallow and deep. There is a
+difference between these methods only for arrays and objects. Shallow
+copying only copies the first level value (array or object) and uses
+the same child values in the copied value. Deep copying makes a fresh
+copy of the child values, too. Moreover, all the child values are deep
+copied in a recursive fashion.
+
+.. cfunction:: json_t *json_copy(json_t *value)
+
+   .. refcounting:: new
+
+   Returns a shallow copy of *value*, or *NULL* on error.
+
+   .. versionadded:: 1.2
+
+.. cfunction:: json_t *json_deep_copy(json_t *value)
+
+   .. refcounting:: new
+
+   Returns a deep copy of *value*, or *NULL* on error.
+
+   .. versionadded:: 1.2

src/jansson.h

@@ -142,6 +142,12 @@ int json_real_set(json_t *real, double value);
 int json_equal(json_t *value1, json_t *value2);
 
 
+/* copying */
+
+json_t *json_copy(json_t *value);
+json_t *json_deep_copy(json_t *value);
+
+
 /* loading, printing */
 
 #define JSON_ERROR_TEXT_LENGTH  160

src/value.c

@@ -243,6 +243,56 @@ static int json_object_equal(json_t *object1, json_t *object2)
     return 1;
 }
 
+static json_t *json_object_copy(json_t *object)
+{
+    json_t *result;
+    void *iter;
+
+    result = json_object();
+    if(!result)
+        return NULL;
+
+    iter = json_object_iter(object);
+    while(iter)
+    {
+        const char *key;
+        json_t *value;
+
+        key = json_object_iter_key(iter);
+        value = json_object_iter_value(iter);
+        json_object_set(result, key, value);
+
+        iter = json_object_iter_next(object, iter);
+    }
+
+    return result;
+}
+
+static json_t *json_object_deep_copy(json_t *object)
+{
+    json_t *result;
+    void *iter;
+
+    result = json_object();
+    if(!result)
+        return NULL;
+
+    iter = json_object_iter(object);
+    while(iter)
+    {
+        const char *key;
+        json_t *value;
+
+        key = json_object_iter_key(iter);
+        value = json_object_iter_value(iter);
+        json_object_set(result, key, json_deep_copy(value));
+
+        iter = json_object_iter_next(object, iter);
+    }
+
+    return result;
+}
+
 
 /*** array ***/
 
@@ -511,6 +561,35 @@ static int json_array_equal(json_t *array1, json_t *array2)
     return 1;
 }
 
+static json_t *json_array_copy(json_t *array)
+{
+    json_t *result;
+    unsigned int i;
+
+    result = json_array();
+    if(!result)
+        return NULL;
+
+    for(i = 0; i < json_array_size(array); i++)
+        json_array_append(result, json_array_get(array, i));
+
+    return result;
+}
+
+static json_t *json_array_deep_copy(json_t *array)
+{
+    json_t *result;
+    unsigned int i;
+
+    result = json_array();
+    if(!result)
+        return NULL;
+
+    for(i = 0; i < json_array_size(array); i++)
+        json_array_append(result, json_deep_copy(json_array_get(array, i)));
+
+    return result;
+}
 
 /*** string ***/
 
@@ -586,6 +665,12 @@ static int json_string_equal(json_t *string1, json_t *string2)
     return strcmp(json_string_value(string1), json_string_value(string2)) == 0;
 }
 
+static json_t *json_string_copy(json_t *string)
+{
+    return json_string(json_string_value(string));
+}
+
+
 /*** integer ***/
 
 json_t *json_integer(int value)
@@ -627,6 +712,12 @@ static int json_integer_equal(json_t *integer1, json_t *integer2)
     return json_integer_value(integer1) == json_integer_value(integer2);
 }
 
+static json_t *json_integer_copy(json_t *integer)
+{
+    return json_integer(json_integer_value(integer));
+}
+
+
 /*** real ***/
 
 json_t *json_real(double value)
@@ -668,6 +759,12 @@ static int json_real_equal(json_t *real1, json_t *real2)
     return json_real_value(real1) == json_real_value(real2);
 }
 
+static json_t *json_real_copy(json_t *real)
+{
+    return json_real(json_real_value(real));
+}
+
+
 /*** number ***/
 
 double json_number_value(const json_t *json)
@@ -767,3 +864,61 @@ int json_equal(json_t *json1, json_t *json2)
 
     return 0;
 }
+
+
+/*** copying ***/
+
+json_t *json_copy(json_t *json)
+{
+    if(!json)
+        return NULL;
+
+    if(json_is_object(json))
+        return json_object_copy(json);
+
+    if(json_is_array(json))
+        return json_array_copy(json);
+
+    if(json_is_string(json))
+        return json_string_copy(json);
+
+    if(json_is_integer(json))
+        return json_integer_copy(json);
+
+    if(json_is_real(json))
+        return json_real_copy(json);
+
+    if(json_is_true(json) || json_is_false(json) || json_is_null(json))
+        return json;
+
+    return NULL;
+}
+
+json_t *json_deep_copy(json_t *json)
+{
+    if(!json)
+        return NULL;
+
+    if(json_is_object(json))
+        return json_object_deep_copy(json);
+
+    if(json_is_array(json))
+        return json_array_deep_copy(json);
+
+    /* for the rest of the types, deep copying doesn't differ from
+       shallow copying */
+
+    if(json_is_string(json))
+        return json_string_copy(json);
+
+    if(json_is_integer(json))
+        return json_integer_copy(json);
+
+    if(json_is_real(json))
+        return json_real_copy(json);
+
+    if(json_is_true(json) || json_is_false(json) || json_is_null(json))
+        return json;
+
+    return NULL;
+}

test/.gitignore

@@ -2,6 +2,7 @@ logs
 bin/json_process
 suites/api/test_array
 suites/api/test_equal
+suites/api/test_copy
 suites/api/test_load
 suites/api/test_number
 suites/api/test_object

test/suites/api/Makefile.am

@@ -1,12 +1,14 @@
 check_PROGRAMS = \
 	test_array \
 	test_equal \
+	test_copy \
 	test_load \
 	test_simple \
 	test_number \
 	test_object
 
 test_array_SOURCES = test_array.c util.h
+test_copy_SOURCES = test_copy.c util.h
 test_load_SOURCES = test_load.c util.h
 test_simple_SOURCES = test_simple.c util.h
 test_number_SOURCES = test_number.c util.h

test/suites/api/check-exports

@@ -49,6 +49,8 @@ json_loads
 json_loadf
 json_load_file
 json_equal
+json_copy
+json_deep_copy
 EOF
 
 # The list of functions are not exported in the library because they

test/suites/api/test_copy.c

@@ -0,0 +1,319 @@
+/*
+ * Copyright (c) 2009 Petri Lehtinen <petri@digip.org>
+ *
+ * Jansson is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See LICENSE for details.
+ */
+
+#include <string.h>
+#include <jansson.h>
+#include "util.h"
+
+static void test_copy_simple(void)
+{
+    json_t *value, *copy;
+
+    if(json_copy(NULL))
+        fail("copying NULL doesn't return NULL");
+
+    /* true */
+    value = json_true();
+    copy = json_copy(value);
+    if(value != copy)
+        fail("copying true failed");
+    json_decref(value);
+    json_decref(copy);
+
+    /* false */
+    value = json_false();
+    copy = json_copy(value);
+    if(value != copy)
+        fail("copying false failed");
+    json_decref(value);
+    json_decref(copy);
+
+    /* null */
+    value = json_null();
+    copy = json_copy(value);
+    if(value != copy)
+        fail("copying null failed");
+    json_decref(value);
+    json_decref(copy);
+
+    /* string */
+    value = json_string("foo");
+    if(!value)
+        fail("unable to create a string");
+    copy = json_copy(value);
+    if(!copy)
+        fail("unable to copy a string");
+    if(copy == value)
+        fail("copying a string doesn't copy");
+    if(!json_equal(copy, value))
+        fail("copying a string produces an inequal copy");
+    if(value->refcount != 1 || copy->refcount != 1)
+        fail("invalid refcounts");
+    json_decref(value);
+    json_decref(copy);
+
+    /* integer */
+    value = json_integer(543);
+    if(!value)
+        fail("unable to create an integer");
+    copy = json_copy(value);
+    if(!copy)
+        fail("unable to copy an integer");
+    if(copy == value)
+        fail("copying an integer doesn't copy");
+    if(!json_equal(copy, value))
+        fail("copying an integer produces an inequal copy");
+    if(value->refcount != 1 || copy->refcount != 1)
+        fail("invalid refcounts");
+    json_decref(value);
+    json_decref(copy);
+
+    /* real */
+    value = json_real(123e9);
+    if(!value)
+        fail("unable to create a real");
+    copy = json_copy(value);
+    if(!copy)
+        fail("unable to copy a real");
+    if(copy == value)
+        fail("copying a real doesn't copy");
+    if(!json_equal(copy, value))
+        fail("copying a real produces an inequal copy");
+    if(value->refcount != 1 || copy->refcount != 1)
+        fail("invalid refcounts");
+    json_decref(value);
+    json_decref(copy);
+}
+
+static void test_deep_copy_simple(void)
+{
+    json_t *value, *copy;
+
+    if(json_deep_copy(NULL))
+        fail("deep copying NULL doesn't return NULL");
+
+    /* true */
+    value = json_true();
+    copy = json_deep_copy(value);
+    if(value != copy)
+        fail("deep copying true failed");
+    json_decref(value);
+    json_decref(copy);
+
+    /* false */
+    value = json_false();
+    copy = json_deep_copy(value);
+    if(value != copy)
+        fail("deep copying false failed");
+    json_decref(value);
+    json_decref(copy);
+
+    /* null */
+    value = json_null();
+    copy = json_deep_copy(value);
+    if(value != copy)
+        fail("deep copying null failed");
+    json_decref(value);
+    json_decref(copy);
+
+    /* string */
+    value = json_string("foo");
+    if(!value)
+        fail("unable to create a string");
+    copy = json_deep_copy(value);
+    if(!copy)
+        fail("unable to deep copy a string");
+    if(copy == value)
+        fail("deep copying a string doesn't copy");
+    if(!json_equal(copy, value))
+        fail("deep copying a string produces an inequal copy");
+    if(value->refcount != 1 || copy->refcount != 1)
+        fail("invalid refcounts");
+    json_decref(value);
+    json_decref(copy);
+
+    /* integer */
+    value = json_integer(543);
+    if(!value)
+        fail("unable to create an integer");
+    copy = json_deep_copy(value);
+    if(!copy)
+        fail("unable to deep copy an integer");
+    if(copy == value)
+        fail("deep copying an integer doesn't copy");
+    if(!json_equal(copy, value))
+        fail("deep copying an integer produces an inequal copy");
+    if(value->refcount != 1 || copy->refcount != 1)
+        fail("invalid refcounts");
+    json_decref(value);
+    json_decref(copy);
+
+    /* real */
+    value = json_real(123e9);
+    if(!value)
+        fail("unable to create a real");
+    copy = json_deep_copy(value);
+    if(!copy)
+        fail("unable to deep copy a real");
+    if(copy == value)
+        fail("deep copying a real doesn't copy");
+    if(!json_equal(copy, value))
+        fail("deep copying a real produces an inequal copy");
+    if(value->refcount != 1 || copy->refcount != 1)
+        fail("invalid refcounts");
+    json_decref(value);
+    json_decref(copy);
+}
+
+static void test_copy_array(void)
+{
+    const char *json_array_text = "[1, \"foo\", 3.141592, {\"foo\": \"bar\"}]";
+
+    json_t *array, *copy;
+    unsigned int i;
+
+    array = json_loads(json_array_text, NULL);
+    if(!array)
+        fail("unable to parse an array");
+
+    copy = json_copy(array);
+    if(!copy)
+        fail("unable to copy an array");
+    if(copy == array)
+        fail("copying an array doesn't copy");
+    if(!json_equal(copy, array))
+        fail("copying an array produces an inequal copy");
+
+    for(i = 0; i < json_array_size(copy); i++)
+    {
+        if(json_array_get(array, i) != json_array_get(copy, i))
+            fail("copying an array modifies its elements");
+    }
+
+    json_decref(array);
+    json_decref(copy);
+}
+
+static void test_deep_copy_array(void)
+{
+    const char *json_array_text = "[1, \"foo\", 3.141592, {\"foo\": \"bar\"}]";
+
+    json_t *array, *copy;
+    unsigned int i;
+
+    array = json_loads(json_array_text, NULL);
+    if(!array)
+        fail("unable to parse an array");
+
+    copy = json_deep_copy(array);
+    if(!copy)
+        fail("unable to deep copy an array");
+    if(copy == array)
+        fail("deep copying an array doesn't copy");
+    if(!json_equal(copy, array))
+        fail("deep copying an array produces an inequal copy");
+
+    for(i = 0; i < json_array_size(copy); i++)
+    {
+        if(json_array_get(array, i) == json_array_get(copy, i))
+            fail("deep copying an array doesn't copy its elements");
+    }
+
+    json_decref(array);
+    json_decref(copy);
+}
+
+static void test_copy_object(void)
+{
+    const char *json_object_text =
+        "{\"foo\": \"bar\", \"a\": 1, \"b\": 3.141592, \"c\": [1,2,3,4]}";
+
+    json_t *object, *copy;
+    void *iter;
+
+    object = json_loads(json_object_text, NULL);
+    if(!object)
+        fail("unable to parse an object");
+
+    copy = json_copy(object);
+    if(!copy)
+        fail("unable to copy an object");
+    if(copy == object)
+        fail("copying an object doesn't copy");
+    if(!json_equal(copy, object))
+        fail("copying an object produces an inequal copy");
+
+    iter = json_object_iter(object);
+    while(iter)
+    {
+        const char *key;
+        json_t *value1, *value2;
+
+        key = json_object_iter_key(iter);
+        value1 = json_object_iter_value(iter);
+        value2 = json_object_get(copy, key);
+
+        if(value1 != value2)
+            fail("deep copying an object modifies its items");
+
+        iter = json_object_iter_next(object, iter);
+    }
+
+    json_decref(object);
+    json_decref(copy);
+}
+
+static void test_deep_copy_object(void)
+{
+    const char *json_object_text =
+        "{\"foo\": \"bar\", \"a\": 1, \"b\": 3.141592, \"c\": [1,2,3,4]}";
+
+    json_t *object, *copy;
+    void *iter;
+
+    object = json_loads(json_object_text, NULL);
+    if(!object)
+        fail("unable to parse an object");
+
+    copy = json_deep_copy(object);
+    if(!copy)
+        fail("unable to deep copy an object");
+    if(copy == object)
+        fail("deep copying an object doesn't copy");
+    if(!json_equal(copy, object))
+        fail("deep copying an object produces an inequal copy");
+
+    iter = json_object_iter(object);
+    while(iter)
+    {
+        const char *key;
+        json_t *value1, *value2;
+
+        key = json_object_iter_key(iter);
+        value1 = json_object_iter_value(iter);
+        value2 = json_object_get(copy, key);
+
+        if(value1 == value2)
+            fail("deep copying an object doesn't copy its items");
+
+        iter = json_object_iter_next(object, iter);
+    }
+
+    json_decref(object);
+    json_decref(copy);
+}
+
+int main()
+{
+    test_copy_simple();
+    test_deep_copy_simple();
+    test_copy_array();
+    test_deep_copy_array();
+    test_copy_object();
+    test_deep_copy_object();
+    return 0;
+}