wrap-json: add unpacking tool for json

The functions wrap_json_unpack, wrap_json_vunpack,
wrap_json_check, wrap_json_vcheck, wrap_json_match and
wrap_json_vmatch can be used to get items in a json
object.

These functions are likely to be compatible in the
format with the unpacking functions of the library
jansson [1].

[1] http://jansson.readthedocs.io/en/2.10/apiref.html#parsing-and-validating-values

Change-Id: I18ad702498b9a70215d88b2a3c13bd0f6194bb45
Signed-off-by: José Bollo <jose.bollo@iot.bzh>

4 files changed, 892 insertions, 107 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 7d2db4a5..6db4d4f2 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -69,6 +69,7 @@ ADD_LIBRARY(afb-lib STATIC
 	sig-monitor.c
 	verbose.c
 	websock.c
+	wrap-json.c
 )
 
 ###########################################
diff --git a/src/wrap-json.c b/src/wrap-json.c
index 1b4b13ea..2354ea72 100644
--- a/src/wrap-json.c
+++ b/src/wrap-json.c
@@ -20,61 +20,73 @@
 
 #include "wrap-json.h"
 
-#define STACKCOUNT 32
-#define STRCOUNT   8
+#define STACKCOUNT  32
+#define STRCOUNT    8
 
 enum {
-	wrap_json_pack_error_none,
-	wrap_json_pack_error_null_object,
-	wrap_json_pack_error_truncated,
-	wrap_json_pack_error_internal_error,
-	wrap_json_pack_error_out_of_memory,
-	wrap_json_pack_error_invalid_character,
-	wrap_json_pack_error_too_long,
-	wrap_json_pack_error_too_deep,
-	wrap_json_pack_error_null_spec,
-	wrap_json_pack_error_null_key,
-	wrap_json_pack_error_null_string,
-	_wrap_json_pack_error_count_
+	wrap_json_error_none,
+	wrap_json_error_null_object,
+	wrap_json_error_truncated,
+	wrap_json_error_internal_error,
+	wrap_json_error_out_of_memory,
+	wrap_json_error_invalid_character,
+	wrap_json_error_too_long,
+	wrap_json_error_too_deep,
+	wrap_json_error_null_spec,
+	wrap_json_error_null_key,
+	wrap_json_error_null_string,
+	wrap_json_error_out_of_range,
+	wrap_json_error_incomplete,
+	wrap_json_error_missfit_type,
+	wrap_json_error_key_not_found,
+	_wrap_json_error_count_
 };
 
 static const char ignore_all[] = " \t\n\r,:";
-static const char accept_arr[] = "][{snbiIfoO";
-static const char accept_key[] = "s}";
-#define accept_any (&accept_arr[1])
+static const char pack_accept_arr[] = "][{snbiIfoO";
+static const char pack_accept_key[] = "s}";
+#define pack_accept_any (&pack_accept_arr[1])
 
-static const char *pack_errors[_wrap_json_pack_error_count_] =
+static const char unpack_accept_arr[] = "*!][{snbiIfFoO";
+static const char unpack_accept_key[] = "*!s}";
+#define unpack_accept_any (&unpack_accept_arr[3])
+
+static const char *pack_errors[_wrap_json_error_count_] =
 {
-	[wrap_json_pack_error_none] = "unknown error",
-	[wrap_json_pack_error_null_object] = "null object",
-	[wrap_json_pack_error_truncated] = "truncated",
-	[wrap_json_pack_error_internal_error] = "internal error",
-	[wrap_json_pack_error_out_of_memory] = "out of memory",
-	[wrap_json_pack_error_invalid_character] = "invalid character",
-	[wrap_json_pack_error_too_long] = "too long",
-	[wrap_json_pack_error_too_deep] = "too deep",
-	[wrap_json_pack_error_null_spec] = "spec is NULL",
-	[wrap_json_pack_error_null_key] = "key is NULL",
-	[wrap_json_pack_error_null_string] = "string is NULL"
+	[wrap_json_error_none] = "unknown error",
+	[wrap_json_error_null_object] = "null object",
+	[wrap_json_error_truncated] = "truncated",
+	[wrap_json_error_internal_error] = "internal error",
+	[wrap_json_error_out_of_memory] = "out of memory",
+	[wrap_json_error_invalid_character] = "invalid character",
+	[wrap_json_error_too_long] = "too long",
+	[wrap_json_error_too_deep] = "too deep",
+	[wrap_json_error_null_spec] = "spec is NULL",
+	[wrap_json_error_null_key] = "key is NULL",
+	[wrap_json_error_null_string] = "string is NULL",
+	[wrap_json_error_out_of_range] = "array too small",
+	[wrap_json_error_incomplete] = "incomplete container",
+	[wrap_json_error_missfit_type] = "missfit of type",
+	[wrap_json_error_key_not_found] = "key not found"
 };
 
-int wrap_json_pack_error_position(int rc)
+int wrap_json_get_error_position(int rc)
 {
 	if (rc < 0)
 		rc = -rc;
 	return (rc >> 4) + 1;
 }
 
-int wrap_json_pack_error_code(int rc)
+int wrap_json_get_error_code(int rc)
 {
 	if (rc < 0)
 		rc = -rc;
 	return rc & 15;
 }
 
-const char *wrap_json_pack_error_string(int rc)
+const char *wrap_json_get_error_string(int rc)
 {
-	rc = wrap_json_pack_error_code(rc);
+	rc = wrap_json_get_error_code(rc);
 	if (rc >= sizeof pack_errors / sizeof *pack_errors)
 		rc = 0;
 	return pack_errors[rc];
@@ -91,6 +103,7 @@ static inline const char *skip(const char *d)
 
 int wrap_json_vpack(struct json_object **result, const char *desc, va_list args)
 {
+	/* TODO: the case of structs with key being single char should be optimized */
 	int nstr, notnull, nullable, rc;
 	size_t sz, dsz, ssz;
 	char *s;
@@ -106,7 +119,7 @@ int wrap_json_vpack(struct json_object **result, const char *desc, va_list args)
 	top = stack;
 	top->key = NULL;
 	top->cont = NULL;
-	top->acc = accept_any;
+	top->acc = pack_accept_any;
 	top->type = 0;
 	if (!desc)
 		goto null_spec;
@@ -163,7 +176,7 @@ int wrap_json_vpack(struct json_object **result, const char *desc, va_list args)
 					dsz -= strs[nstr].sz;
 					memcpy(&s[dsz], strs[nstr].str, strs[nstr].sz);
 				}
-				obj = json_object_new_string_len(s, sz);
+				obj = json_object_new_string_len(s, (int)sz);
 				if (!obj)
 					goto out_of_memory;
 			} else if (nullable)
@@ -211,11 +224,11 @@ int wrap_json_vpack(struct json_object **result, const char *desc, va_list args)
 			top->key = NULL;
 			if (c == '[') {
 				top->type = ']';
-				top->acc = accept_arr;
+				top->acc = pack_accept_arr;
 				top->cont = json_object_new_array();
 			} else {
 				top->type = '}';
-				top->acc = accept_key;
+				top->acc = pack_accept_key;
 				top->cont = json_object_new_object();
 			}
 			if (!top->cont)
@@ -224,7 +237,7 @@ int wrap_json_vpack(struct json_object **result, const char *desc, va_list args)
 		case '}':
 		case ']':
 			if (c != top->type || top <= stack)
-				goto invalid_character;
+				goto internal_error;
 			obj = (top--)->cont;
 			if (*d == '*' && !(c == '}' ? json_object_object_length(obj) : json_object_array_length(obj))) {
 				json_object_put(obj);
@@ -252,7 +265,7 @@ int wrap_json_vpack(struct json_object **result, const char *desc, va_list args)
 			if (!obj)
 				goto null_key;
 			top->key = obj;
-			top->acc = accept_any;
+			top->acc = pack_accept_any;
 			top->type = ':';
 			break;
 		case ':':
@@ -262,41 +275,43 @@ int wrap_json_vpack(struct json_object **result, const char *desc, va_list args)
 				d = skip(++d);
 			json_object_put(top->key);
 			top->key = NULL;
-			top->acc = accept_key;
+			top->acc = pack_accept_key;
 			top->type = '}';
 			break;
+		default:
+			goto internal_error;
 		}
 	}
 
 null_object:
-	rc = wrap_json_pack_error_null_object;
+	rc = wrap_json_error_null_object;
 	goto error;
 truncated:
-	rc = wrap_json_pack_error_truncated;
+	rc = wrap_json_error_truncated;
 	goto error;
 internal_error:
-	rc = wrap_json_pack_error_internal_error;
+	rc = wrap_json_error_internal_error;
 	goto error;
 out_of_memory:
-	rc = wrap_json_pack_error_out_of_memory;
+	rc = wrap_json_error_out_of_memory;
 	goto error;
 invalid_character:
-	rc = wrap_json_pack_error_invalid_character;
+	rc = wrap_json_error_invalid_character;
 	goto error;
 too_long:
-	rc = wrap_json_pack_error_too_long;
+	rc = wrap_json_error_too_long;
 	goto error;
 too_deep:
-	rc = wrap_json_pack_error_too_deep;
+	rc = wrap_json_error_too_deep;
 	goto error;
 null_spec:
-	rc = wrap_json_pack_error_null_spec;
+	rc = wrap_json_error_null_spec;
 	goto error;
 null_key:
-	rc = wrap_json_pack_error_null_key;
+	rc = wrap_json_error_null_key;
 	goto error;
 null_string:
-	rc = wrap_json_pack_error_null_string;
+	rc = wrap_json_error_null_string;
 	goto error;
 error:
 	do {
@@ -319,10 +334,317 @@ int wrap_json_pack(struct json_object **result, const char *desc, ...)
 	return rc;
 }
 
-#if 1
+static int vunpack(struct json_object *object, const char *desc, va_list args, int store)
+{
+	int rc, optionnal, ignore;
+	char c, xacc[2] = { 0, 0 };
+	const char *acc;
+	const char *d, *fit;
+	const char *key;
+	const char **ps;
+	double *pf;
+	int *pi;
+	int64_t *pI;
+	size_t *pz;
+	struct { struct json_object *parent; const char *acc; int index, count; char type; } stack[STACKCOUNT], *top;
+	struct json_object *obj;
+	struct json_object **po;
+
+	xacc[0] = 0;
+	ignore = 0;
+	top = NULL;
+	acc = unpack_accept_any;
+	if (!desc)
+		goto null_spec;
+	d = skip(desc);
+	obj = object;
+	for(;;) {
+		fit = d;
+		c = *d;
+		if (!c)
+			goto truncated;
+		if (!strchr(acc, c))
+			goto invalid_character;
+		d = skip(++d);
+		switch(c) {
+		case 's':
+			if (xacc[0] == '}') {
+				/* expects a key */
+				key = va_arg(args, const char *);
+				if (!key)
+					goto null_key;
+				if (*d != '?')
+					optionnal = 0;
+				else {
+					optionnal = 1;
+					d = skip(++d);
+				}
+				if (ignore)
+					ignore++;
+				else {
+					if (json_object_object_get_ex(top->parent, key, &obj)) {
+						/* found */
+						top->index++;
+					} else {
+						/* not found */
+						if (!optionnal)
+							goto key_not_found;
+						ignore = 1;
+						obj = NULL;
+					}
+				}
+				xacc[0] = ':';
+				acc = unpack_accept_any;
+				continue;
+			}
+			/* get a string */
+			if (store)
+				ps = va_arg(args, const char **);
+			if (!ignore) {
+				if (!json_object_is_type(obj, json_type_string))
+					goto missfit;
+				if (store && ps)
+					*ps = json_object_get_string(obj);
+			}
+			if (*d == '%') {
+				d = skip(++d);
+				if (store) {
+					pz = va_arg(args, size_t *);
+					if (!ignore && pz)
+						*pz = (size_t)json_object_get_string_len(obj);
+				}
+			}
+			break;
+		case 'n':
+			if (!ignore && !json_object_is_type(obj, json_type_null))
+				goto missfit;
+			break;
+		case 'b':
+			if (store)
+				pi = va_arg(args, int *);
+
+			if (!ignore) {
+				if (!json_object_is_type(obj, json_type_boolean))
+					goto missfit;
+				if (store && pi)
+					*pi = json_object_get_boolean(obj);
+			}
+			break;
+		case 'i':
+			if (store)
+				pi = va_arg(args, int *);
+
+			if (!ignore) {
+				if (!json_object_is_type(obj, json_type_int))
+					goto missfit;
+				if (store && pi)
+					*pi = json_object_get_int(obj);
+			}
+			break;
+		case 'I':
+			if (store)
+				pI = va_arg(args, int64_t *);
+
+			if (!ignore) {
+				if (!json_object_is_type(obj, json_type_int))
+					goto missfit;
+				if (store && pI)
+					*pI = json_object_get_int64(obj);
+			}
+			break;
+		case 'f':
+		case 'F':
+			if (store)
+				pf = va_arg(args, double *);
+
+			if (!ignore) {
+				if (!(json_object_is_type(obj, json_type_double) || (c == 'F' && json_object_is_type(obj, json_type_int))))
+					goto missfit;
+				if (store && pf)
+					*pf = json_object_get_double(obj);
+			}
+			break;
+		case 'o':
+		case 'O':
+			if (store) {
+				po = va_arg(args, struct json_object **);
+				if (!ignore && po) {
+					if (c == 'O')
+						obj = json_object_get(obj);
+					*po = obj;
+				}
+			}
+			break;
+
+		case '[':
+		case '{':
+			if (!top)
+				top = stack;
+			else if (++top  >= &stack[STACKCOUNT])
+				goto too_deep;
+
+			top->acc = acc;
+			top->type = xacc[0];
+			top->index = 0;
+			top->parent = obj;
+			if (ignore)
+				ignore++;
+			if (c == '[') {
+				if (!ignore) {
+					if (!json_object_is_type(obj, json_type_array))
+						goto missfit;
+					top->count = json_object_array_length(obj);
+				}
+				xacc[0] = ']';
+				acc = unpack_accept_arr;
+			} else {
+				if (!ignore) {
+					if (!json_object_is_type(obj, json_type_object))
+						goto missfit;
+					top->count = json_object_object_length(obj);
+				}
+				xacc[0] = '}';
+				acc = unpack_accept_key;
+				continue;
+			}
+			break;
+		case '}':
+		case ']':
+			if (!top || c != xacc[0])
+				goto internal_error;
+			acc = top->acc;
+			xacc[0] = top->type;
+			top = top == stack ? NULL : top - 1;
+			if (ignore)
+				ignore--;
+			break;
+		case '!':
+			if (*d != xacc[0])
+				goto invalid_character;
+			if (!ignore && top->index != top->count)
+				goto incomplete;
+		case '*':
+			acc = xacc;
+			continue;
+		default:
+			goto internal_error;
+		}
+		switch (xacc[0]) {
+		case 0:
+			if (top)
+				goto internal_error;
+			if (*d)
+				goto invalid_character;
+			return 0;
+		case ']':
+			if (!ignore) {
+				key = strchr(unpack_accept_arr, *d);
+				if (key && key >= unpack_accept_any) {
+					if (top->index >= top->count)
+						goto out_of_range;
+					obj = json_object_array_get_idx(top->parent, top->index++);
+				}
+			}
+			break;
+		case ':':
+			acc = unpack_accept_key;
+			xacc[0] = '}';
+			if (ignore)
+				ignore--;
+			break;
+		default:
+			goto internal_error;
+		}
+	}
+truncated:
+	rc = wrap_json_error_truncated;
+	goto error;
+internal_error:
+	rc = wrap_json_error_internal_error;
+	goto error;
+invalid_character:
+	rc = wrap_json_error_invalid_character;
+	goto error;
+too_deep:
+	rc = wrap_json_error_too_deep;
+	goto error;
+null_spec:
+	rc = wrap_json_error_null_spec;
+	goto error;
+null_key:
+	rc = wrap_json_error_null_key;
+	goto error;
+out_of_range:
+	rc = wrap_json_error_out_of_range;
+	goto error;
+incomplete:
+	rc = wrap_json_error_incomplete;
+	goto error;
+missfit:
+	rc = wrap_json_error_missfit_type;
+	goto errorfit;
+key_not_found:
+	rc = wrap_json_error_key_not_found;
+	goto error;
+errorfit:
+	d = fit;
+error:
+	rc = rc | (int)((d - desc) << 4);
+	return -rc;
+}
+
+int wrap_json_vcheck(struct json_object *object, const char *desc, va_list args)
+{
+	return vunpack(object, desc, args, 0);
+}
+
+int wrap_json_check(struct json_object *object, const char *desc, ...)
+{
+	int rc;
+	va_list args;
+
+	va_start(args, desc);
+	rc = vunpack(object, desc, args, 0);
+	va_end(args);
+	return rc;
+}
+
+int wrap_json_vmatch(struct json_object *object, const char *desc, va_list args)
+{
+	return !vunpack(object, desc, args, 0);
+}
+
+int wrap_json_match(struct json_object *object, const char *desc, ...)
+{
+	int rc;
+	va_list args;
+
+	va_start(args, desc);
+	rc = vunpack(object, desc, args, 0);
+	va_end(args);
+	return !rc;
+}
+
+int wrap_json_vunpack(struct json_object *object, const char *desc, va_list args)
+{
+	return vunpack(object, desc, args, 1);
+}
+
+int wrap_json_unpack(struct json_object *object, const char *desc, ...)
+{
+	int rc;
+	va_list args;
+
+	va_start(args, desc);
+	rc = vunpack(object, desc, args, 1);
+	va_end(args);
+	return rc;
+}
+
+#if defined(WRAP_JSON_TEST)
 #include <stdio.h>
 
-void T(const char *desc, ...)
+void p(const char *desc, ...)
 {
 	int rc;
 	va_list args;
@@ -334,69 +656,219 @@ void T(const char *desc, ...)
 	if (!rc) 
 		printf("  SUCCESS %s\n\n", json_object_to_json_string(result));
 	else
-		printf("  ERROR[char %d err %d] %s\n\n", wrap_json_pack_error_position(rc), wrap_json_pack_error_code(rc), wrap_json_pack_error_string(rc));
+		printf("  ERROR[char %d err %d] %s\n\n", wrap_json_get_error_position(rc), wrap_json_get_error_code(rc), wrap_json_get_error_string(rc));
 	json_object_put(result);
 }
 
-#define t(...) printf("testing(%s)\n",#__VA_ARGS__); T(__VA_ARGS__);
+const char *xs[10];
+int *xi[10];
+int64_t *xI[10];
+double *xf[10];
+struct json_object *xo[10];
+size_t xz[10];
+
+void u(const char *value, const char *desc, ...)
+{
+	unsigned m, k;
+	int rc;
+	va_list args;
+	struct json_object *obj, *o;
+
+	memset(xs, 0, sizeof xs);
+	memset(xi, 0, sizeof xi);
+	memset(xI, 0, sizeof xI);
+	memset(xf, 0, sizeof xf);
+	memset(xo, 0, sizeof xo);
+	memset(xz, 0, sizeof xz);
+	obj = json_tokener_parse(value);
+	va_start(args, desc);
+	rc = wrap_json_vunpack(obj, desc, args);
+	va_end(args);
+	if (rc) 
+		printf("  ERROR[char %d err %d] %s\n\n", wrap_json_get_error_position(rc), wrap_json_get_error_code(rc), wrap_json_get_error_string(rc));
+	else {
+		value = NULL;
+		printf("  SUCCESS");
+		va_start(args, desc);
+		k = m = 0;
+		while(*desc) {
+			switch(*desc) {
+			case '{': m = (m << 1) | 1; k = 1; break;
+			case '}': m = m >> 1; k = m&1; break;
+			case '[': m = m << 1; k = 0; break;
+			case ']': m = m >> 1; k = m&1; break;
+			case 's': printf(" s:%s", k ? va_arg(args, const char*) : *(va_arg(args, const char**)?:&value)); k ^= m&1; break;
+			case '%': printf(" %%:%zu", *va_arg(args, size_t*)); k = m&1; break;
+			case 'n': printf(" n"); k = m&1; break;
+			case 'b': printf(" b:%d", *va_arg(args, int*)); k = m&1; break;
+			case 'i': printf(" i:%d", *va_arg(args, int*)); k = m&1; break;
+			case 'I': printf(" I:%lld", *va_arg(args, int64_t*)); k = m&1; break;
+			case 'f': printf(" f:%f", *va_arg(args, double*)); k = m&1; break;
+			case 'F': printf(" F:%f", *va_arg(args, double*)); k = m&1; break;
+			case 'o': printf(" o:%s", json_object_to_json_string(*va_arg(args, struct json_object**))); k = m&1; break;
+			case 'O': o = *va_arg(args, struct json_object**); printf(" O:%s", json_object_to_json_string(o)); json_object_put(o); k = m&1; break;
+			default: break;
+			}
+			desc++;
+		}
+		va_end(args);
+		printf("\n\n");
+	}
+	json_object_put(obj);
+}
+
+#define P(...) do{ printf("pack(%s)\n",#__VA_ARGS__); p(__VA_ARGS__); } while(0)
+#define U(...) do{ printf("unpack(%s)\n",#__VA_ARGS__); u(__VA_ARGS__); } while(0)
 
 int main()
 {
 	char buffer[4] = {'t', 'e', 's', 't'};
 
-	t("n");
-	t("b", 1);
-	t("b", 0);
-	t("i", 1);
-	t("I", (uint64_t)0x123456789abcdef);
-	t("f", 3.14);
-	t("s", "test");
-	t("s?", "test");
-	t("s?", NULL);
-	t("s#", "test asdf", 4);
-	t("s%", "test asdf", (size_t)4);
-	t("s#", buffer, 4);
-	t("s%", buffer, (size_t)4);
-	t("s++", "te", "st", "ing");
-	t("s#+#+", "test", 1, "test", 2, "test");
-	t("s%+%+", "test", (size_t)1, "test", (size_t)2, "test");
-	t("{}", 1.0);
-	t("[]", 1.0);
-	t("o", json_object_new_int(1));
-	t("o?", json_object_new_int(1));
-	t("o?", NULL);
-	t("O", json_object_new_int(1));
-	t("O?", json_object_new_int(1));
-	t("O?", NULL);
-	t("{s:[]}", "foo");
-	t("{s+#+: []}", "foo", "barbar", 3, "baz");
-	t("{s:s,s:o,s:O}", "a", NULL, "b", NULL, "c", NULL);
-	t("{s:**}", "a", NULL);
-	t("{s:s*,s:o*,s:O*}", "a", NULL, "b", NULL, "c", NULL);
-	t("[i,i,i]", 0, 1, 2);
-	t("[s,o,O]", NULL, NULL, NULL);
-	t("[**]", NULL);
-	t("[s*,o*,O*]", NULL, NULL, NULL);
-	t(" s ", "test");
-	t("[ ]");
-	t("[ i , i,  i ] ", 1, 2, 3);
-	t("{\n\n1");
-	t("[}");
-	t("{]");
-	t("[");
-	t("{");
-	t("[i]a", 42);
-	t("ia", 42);
-	t("s", NULL);
-	t("+", NULL);
-	t(NULL);
-	t("{s:i}", NULL, 1);
-	t("{ {}: s }", "foo");
-	t("{ s: {},  s:[ii{} }", "foo", "bar", 12, 13);
-	t("[[[[[   [[[[[  [[[[ }]]]] ]]]] ]]]]]");
+	P("n");
+	P("b", 1);
+	P("b", 0);
+	P("i", 1);
+	P("I", (uint64_t)0x123456789abcdef);
+	P("f", 3.14);
+	P("s", "test");
+	P("s?", "test");
+	P("s?", NULL);
+	P("s#", "test asdf", 4);
+	P("s%", "test asdf", (size_t)4);
+	P("s#", buffer, 4);
+	P("s%", buffer, (size_t)4);
+	P("s++", "te", "st", "ing");
+	P("s#+#+", "test", 1, "test", 2, "test");
+	P("s%+%+", "test", (size_t)1, "test", (size_t)2, "test");
+	P("{}", 1.0);
+	P("[]", 1.0);
+	P("o", json_object_new_int(1));
+	P("o?", json_object_new_int(1));
+	P("o?", NULL);
+	P("O", json_object_new_int(1));
+	P("O?", json_object_new_int(1));
+	P("O?", NULL);
+	P("{s:[]}", "foo");
+	P("{s+#+: []}", "foo", "barbar", 3, "baz");
+	P("{s:s,s:o,s:O}", "a", NULL, "b", NULL, "c", NULL);
+	P("{s:**}", "a", NULL);
+	P("{s:s*,s:o*,s:O*}", "a", NULL, "b", NULL, "c", NULL);
+	P("[i,i,i]", 0, 1, 2);
+	P("[s,o,O]", NULL, NULL, NULL);
+	P("[**]", NULL);
+	P("[s*,o*,O*]", NULL, NULL, NULL);
+	P(" s ", "test");
+	P("[ ]");
+	P("[ i , i,  i ] ", 1, 2, 3);
+	P("{\n\n1");
+	P("[}");
+	P("{]");
+	P("[");
+	P("{");
+	P("[i]a", 42);
+	P("ia", 42);
+	P("s", NULL);
+	P("+", NULL);
+	P(NULL);
+	P("{s:i}", NULL, 1);
+	P("{ {}: s }", "foo");
+	P("{ s: {},  s:[ii{} }", "foo", "bar", 12, 13);
+	P("[[[[[   [[[[[  [[[[ }]]]] ]]]] ]]]]]");
+
+	U("true", "b", &xi[0]);
+	U("false", "b", &xi[0]);
+	U("null", "n");
+	U("42", "i", &xi[0]);
+	U("123456789", "I", &xI[0]);
+	U("3.14", "f", &xf[0]);
+	U("12345", "F", &xf[0]);
+	U("3.14", "F", &xf[0]);
+	U("\"foo\"", "s", &xs[0]);
+	U("\"foo\"", "s%", &xs[0], &xz[0]);
+	U("{}", "{}");
+	U("[]", "[]");
+	U("{}", "o", &xo[0]);
+	U("{}", "O", &xo[0]);
+	U("{\"foo\":42}", "{si}", "foo", &xi[0]);
+	U("[1,2,3]", "[i,i,i]", &xi[0], &xi[1], &xi[2]);
+	U("{\"a\":1,\"b\":2,\"c\":3}", "{s:i, s:i, s:i}", "a", &xi[0], "b", &xi[1], "c", &xi[2]);
+	U("42", "z");
+	U("null", "[i]");
+	U("[]", "[}");
+	U("{}", "{]");
+	U("[]", "[");
+	U("{}", "{");
+	U("[42]", "[i]a", &xi[0]);
+	U("42", "ia", &xi[0]);
+	U("[]", NULL);
+	U("\"foo\"", "s", NULL);
+	U("42", "s", NULL);
+	U("42", "n");
+	U("42", "b", NULL);
+	U("42", "f", NULL);
+	U("42", "[i]", NULL);
+	U("42", "{si}", "foo", NULL);
+	U("\"foo\"", "n");
+	U("\"foo\"", "b", NULL);
+	U("\"foo\"", "i", NULL);
+	U("\"foo\"", "I", NULL);
+	U("\"foo\"", "f", NULL);
+	U("\"foo\"", "F", NULL);
+	U("true", "s", NULL);
+	U("true", "n");
+	U("true", "i", NULL);
+	U("true", "I", NULL);
+	U("true", "f", NULL);
+	U("true", "F", NULL);
+	U("[42]", "[ii]", &xi[0], &xi[1]);
+	U("{\"foo\":42}", "{si}", NULL, &xi[0]);
+	U("{\"foo\":42}", "{si}", "baz", &xi[0]);
+	U("[1,2,3]", "[iii!]", &xi[0], &xi[1], &xi[2]);
+	U("[1,2,3]", "[ii!]", &xi[0], &xi[1]);
+	U("[1,2,3]", "[ii]", &xi[0], &xi[1]);
+	U("[1,2,3]", "[ii*]", &xi[0], &xi[1]);
+	U("{\"foo\":42,\"baz\":45}", "{sisi}", "baz", &xi[0], "foo", &xi[1]);
+	U("{\"foo\":42,\"baz\":45}", "{sisi*}", "baz", &xi[0], "foo", &xi[1]);
+	U("{\"foo\":42,\"baz\":45}", "{sisi!}", "baz", &xi[0], "foo", &xi[1]);
+	U("{\"foo\":42,\"baz\":45}", "{si}", "baz", &xi[0], "foo", &xi[1]);
+	U("{\"foo\":42,\"baz\":45}", "{si*}", "baz", &xi[0], "foo", &xi[1]);
+	U("{\"foo\":42,\"baz\":45}", "{si!}", "baz", &xi[0], "foo", &xi[1]);
+	U("[1,{\"foo\":2,\"bar\":null},[3,4]]", "[i{sisn}[ii]]", &xi[0], "foo", &xi[1], "bar", &xi[2], &xi[3]);
+	U("[1,2,3]", "[ii!i]", &xi[0], &xi[1], &xi[2]);
+	U("[1,2,3]", "[ii*i]", &xi[0], &xi[1], &xi[2]);
+	U("{\"foo\":1,\"bar\":2}", "{si!si}", "foo", &xi[1], "bar", &xi[2]);
+	U("{\"foo\":1,\"bar\":2}", "{si*si}", "foo", &xi[1], "bar", &xi[2]);
+	U("{\"foo\":{\"baz\":null,\"bar\":null}}", "{s{sn!}}", "foo", "bar");
+	U("[[1,2,3]]", "[[ii!]]", &xi[0], &xi[1]);
+	U("{}", "{s?i}", "foo", &xi[0]);
+	U("{\"foo\":1}", "{s?i}", "foo", &xi[0]);
+	U("{}", "{s?[ii]s?{s{si!}}}", "foo", &xi[0], &xi[1], "bar", "baz", "quux", &xi[2]);
+	U("{\"foo\":[1,2]}", "{s?[ii]s?{s{si!}}}", "foo", &xi[0], &xi[1], "bar", "baz", "quux", &xi[2]);
+	U("{\"bar\":{\"baz\":{\"quux\":15}}}", "{s?[ii]s?{s{si!}}}", "foo", &xi[0], &xi[1], "bar", "baz", "quux", &xi[2]);
+	U("{\"foo\":{\"bar\":4}}", "{s?{s?i}}", "foo", "bar", &xi[0]);
+	U("{\"foo\":{}}", "{s?{s?i}}", "foo", "bar", &xi[0]);
+	U("{}", "{s?{s?i}}", "foo", "bar", &xi[0]);
+	U("{\"foo\":42,\"baz\":45}", "{s?isi!}", "baz", &xi[0], "foo", &xi[1]);
+	U("{\"foo\":42}", "{s?isi!}", "baz", &xi[0], "foo", &xi[1]);
 	return 0;
 }
 
 #endif
 
+#if 0
+
 
+    /* Unpack the same item twice */
+    j = json_pack("{s:s, s:i, s:b}", "foo", "bar", "baz", 42, "quux", 1);
+    if(!json_unpack_ex(j, &error, 0, "{s:s,s:s!}", "foo", &s, "foo", &s))
+        fail("json_unpack object with strict validation failed");
+    {
+        const char *possible_errors[] = {
+            "2 object item(s) left unpacked: baz, quux",
+            "2 object item(s) left unpacked: quux, baz"
+        };
+        check_errors(possible_errors, 2, "<validation>", 1, 10, 10);
+    }
+    json_decref(j);
+
+#endif
diff --git a/src/wrap-json.h b/src/wrap-json.h
index 1e95dcf2..7fe90eee 100644
--- a/src/wrap-json.h
+++ b/src/wrap-json.h
@@ -21,9 +21,16 @@
 #include <stdarg.h>
 #include <json-c/json.h>
 
-extern int wrap_json_pack_error_position(int rc);
-extern int wrap_json_pack_error_code(int rc);
-extern const char *wrap_json_pack_error_string(int rc);
+extern int wrap_json_get_error_position(int rc);
+extern int wrap_json_get_error_code(int rc);
+extern const char *wrap_json_get_error_string(int rc);
+
 extern int wrap_json_vpack(struct json_object **result, const char *desc, va_list args);
 extern int wrap_json_pack(struct json_object **result, const char *desc, ...);
 
+extern int wrap_json_vunpack(struct json_object *object, const char *desc, va_list args);
+extern int wrap_json_unpack(struct json_object *object, const char *desc, ...);
+extern int wrap_json_vcheck(struct json_object *object, const char *desc, va_list args);
+extern int wrap_json_check(struct json_object *object, const char *desc, ...);
+extern int wrap_json_vmatch(struct json_object *object, const char *desc, va_list args);
+extern int wrap_json_match(struct json_object *object, const char *desc, ...);
diff --git a/src/wrap-json.md b/src/wrap-json.md
new file mode 100644
index 00000000..92940f1a
--- /dev/null
+++ b/src/wrap-json.md
@@ -0,0 +1,305 @@
+WRAP-JSON facility
+==================
+
+The facility wrap-json is based on the pack/unpack API on the
+libray jansson. The two chapters below are copied from the
+documentation of jansson library copyrighted by Petri Lehtinen
+(see at end).
+
+Building Values
+---------------
+
+This section describes functions that help to create, or *pack*, complex
+JSON values, especially nested objects and arrays. Value building is
+based on a *format string* that is used to tell the functions about the
+expected arguments.
+
+For example, the format string `"i"` specifies a single integer value,
+while the format string `"[ssb]"` or the equivalent `"[s, s, b]"`
+specifies an array value with two strings and a boolean as its items:
+
+    /* Create the JSON integer 42 */
+    wrap_json_pack(&result, "i", 42);
+
+    /* Create the JSON array ["foo", "bar", true] */
+    wrap_json_pack(&result, "[ssb]", "foo", "bar", 1);
+
+Here's the full list of format specifiers. The type in parentheses
+denotes the resulting JSON type, and the type in brackets (if any)
+denotes the C type that is expected as the corresponding argument or
+arguments.
+
+`s` (string) \[const char \*\]
+
+:   Convert a null terminated UTF-8 string to a JSON string.
+
+`s?` (string) \[const char \*\]
+
+:   Like `s`, but if the argument is *NULL*, output a JSON null value.
+
+`s*` (string) \[const char \*\]
+
+:   Like `s`, but if the argument is *NULL*, do not output any value.
+    This format can only be used inside an object or an array. If used
+    inside an object, the corresponding key is additionally suppressed
+    when the value is omitted. See below for an example.
+
+`s#` (string) \[const char \*, int\]
+
+:   Convert a UTF-8 buffer of a given length to a JSON string.
+
+`s%` (string) \[const char \*, size\_t\]
+
+:   Like `s#` but the length argument is of type size\_t.
+
+`+` \[const char \*\]
+
+:   Like `s`, but concatenate to the previous string. Only valid after
+    `s`, `s#`, `+` or `+#`.
+
+`+#` \[const char \*, int\]
+
+:   Like `s#`, but concatenate to the previous string. Only valid after
+    `s`, `s#`, `+` or `+#`.
+
+`+%` (string) \[const char \*, size\_t\]
+
+:   Like `+#` but the length argument is of type size\_t.
+
+`n` (null)
+
+:   Output a JSON null value. No argument is consumed.
+
+`b` (boolean) \[int\]
+
+:   Convert a C int to JSON boolean value. Zero is converted to `false`
+    and non-zero to `true`.
+
+`i` (integer) \[int\]
+
+:   Convert a C int to JSON integer.
+
+`I` (integer) \[json\_int\_t\]
+
+:   Convert a C json\_int\_t to JSON integer.
+
+`f` (real) \[double\]
+
+:   Convert a C double to JSON real.
+
+`o` (any value) \[json\_t \*\]
+
+:   Output any given JSON value as-is. If the value is added to an array
+    or object, the reference to the value passed to `o` is stolen by the
+    container.
+
+`O` (any value) \[json\_t \*\]
+
+:   Like `o`, but the argument's reference count is incremented. This is
+    useful if you pack into an array or object and want to keep the
+    reference for the JSON value consumed by `O` to yourself.
+
+`o?`, `O?` (any value) \[json\_t \*\]
+
+:   Like `o` and `O`, respectively, but if the argument is *NULL*,
+    output a JSON null value.
+
+`o*`, `O*` (any value) \[json\_t \*\]
+
+:   Like `o` and `O`, respectively, but if the argument is *NULL*, do
+    not output any value. This format can only be used inside an object
+    or an array. If used inside an object, the corresponding key is
+    additionally suppressed. See below for an example.
+
+`[fmt]` (array)
+
+:   Build an array with contents from the inner format string. `fmt` may
+    contain objects and arrays, i.e. recursive value building is
+    supported.
+
+`{fmt}` (object)
+
+:   Build an object with contents from the inner format string `fmt`.
+    The first, third, etc. format specifier represent a key, and must be
+    a string (see `s`, `s#`, `+` and `+#` above), as object keys are
+    always strings. The second, fourth, etc. format specifier represent
+    a value. Any value may be an object or array, i.e. recursive value
+    building is supported.
+
+Whitespace, `:` and `,` are ignored.
+
+More examples:
+
+    /* Build an empty JSON object */
+    wrap_json_pack(&result, "{}");
+
+    /* Build the JSON object {"foo": 42, "bar": 7} */
+    wrap_json_pack(&result, "{sisi}", "foo", 42, "bar", 7);
+
+    /* Like above, ':', ',' and whitespace are ignored */
+    wrap_json_pack(&result, "{s:i, s:i}", "foo", 42, "bar", 7);
+
+    /* Build the JSON array [[1, 2], {"cool": true}] */
+    wrap_json_pack(&result, "[[i,i],{s:b}]", 1, 2, "cool", 1);
+
+    /* Build a string from a non-null terminated buffer */
+    char buffer[4] = {'t', 'e', 's', 't'};
+    wrap_json_pack(&result, "s#", buffer, 4);
+
+    /* Concatenate strings together to build the JSON string "foobarbaz" */
+    wrap_json_pack(&result, "s++", "foo", "bar", "baz");
+
+    /* Create an empty object or array when optional members are missing */
+    wrap_json_pack(&result, "{s:s*,s:o*,s:O*}", "foo", NULL, "bar", NULL, "baz", NULL);
+    wrap_json_pack(&result, "[s*,o*,O*]", NULL, NULL, NULL);
+
+Parsing and Validating Values
+-----------------------------
+
+This section describes functions that help to validate complex values
+and extract, or *unpack*, data from them. Like building values
+&lt;apiref-pack&gt;, this is also based on format strings.
+
+While a JSON value is unpacked, the type specified in the format string
+is checked to match that of the JSON value. This is the validation part
+of the process. In addition to this, the unpacking functions can also
+check that all items of arrays and objects are unpacked. This check be
+enabled with the format specifier `!` or by using the flag
+`JSON_STRICT`. See below for details.
+
+Here's the full list of format specifiers. The type in parentheses
+denotes the JSON type, and the type in brackets (if any) denotes the C
+type whose address should be passed.
+
+`s` (string) \[const char \*\]
+
+:   Convert a JSON string to a pointer to a null terminated UTF-8
+    string. The resulting string is extracted by using
+    json\_string\_value() internally, so it exists as long as there are
+    still references to the corresponding JSON string.
+
+`s%` (string) \[const char \*, size\_t \*\]
+
+:   Convert a JSON string to a pointer to a null terminated UTF-8 string
+    and its length.
+
+`n` (null)
+
+:   Expect a JSON null value. Nothing is extracted.
+
+`b` (boolean) \[int\]
+
+:   Convert a JSON boolean value to a C int, so that `true` is converted
+    to 1 and `false` to 0.
+
+`i` (integer) \[int\]
+
+:   Convert a JSON integer to C int.
+
+`I` (integer) \[json\_int\_t\]
+
+:   Convert a JSON integer to C json\_int\_t.
+
+`f` (real) \[double\]
+
+:   Convert a JSON real to C double.
+
+`F` (integer or real) \[double\]
+
+:   Convert a JSON number (integer or real) to C double.
+
+`o` (any value) \[json\_t \*\]
+
+:   Store a JSON value with no conversion to a json\_t pointer.
+
+`O` (any value) \[json\_t \*\]
+
+:   Like `O`, but the JSON value's reference count is incremented.
+
+`[fmt]` (array)
+
+:   Convert each item in the JSON array according to the inner format
+    string. `fmt` may contain objects and arrays, i.e. recursive value
+    extraction is supported.
+
+`{fmt}` (object)
+
+:   Convert each item in the JSON object according to the inner format
+    string `fmt`. The first, third, etc. format specifier represent a
+    key, and must be `s`. The corresponding argument to unpack functions
+    is read as the object key. The second fourth, etc. format specifier
+    represent a value and is written to the address given as the
+    corresponding argument. **Note** that every other argument is read
+    from and every other is written to.
+
+    `fmt` may contain objects and arrays as values, i.e. recursive value
+    extraction is supported.
+
+`!`
+
+:   This special format specifier is used to enable the check that all
+    object and array items are accessed, on a per-value basis. It must
+    appear inside an array or object as the last format specifier before
+    the closing bracket or brace.
+
+`*`
+
+:   This special format specifier is the opposite of `!`. This is the default.
+    It must appear inside an array or object as the last format specifier
+    before the closing bracket or brace.
+
+Whitespace, `:` and `,` are ignored.
+
+Examples:
+
+    /* root is the JSON integer 42 */
+    int myint;
+    wrap_json_unpack(root, "i", &myint);
+    assert(myint == 42);
+
+    /* root is the JSON object {"foo": "bar", "quux": true} */
+    const char *str;
+    int boolean;
+    wrap_json_unpack(root, "{s:s, s:b}", "foo", &str, "quux", &boolean);
+    assert(strcmp(str, "bar") == 0 && boolean == 1);
+
+    /* root is the JSON array [[1, 2], {"baz": null} */
+    wrap_json_check(root, "[[i,i], {s:n}]", "baz");
+    /* returns 0 for validation success, nothing is extracted */
+
+    /* root is the JSON array [1, 2, 3, 4, 5] */
+    int myint1, myint2;
+    wrap_json_unpack(root, "[ii!]", &myint1, &myint2);
+    /* returns -1 for failed validation */
+
+    /* root is an empty JSON object */
+    int myint = 0, myint2 = 0, myint3 = 0;
+    wrap_json_unpack(root, "{s?i, s?[ii]}",
+                "foo", &myint1,
+                "bar", &myint2, &myint3);
+    /* myint1, myint2 or myint3 is no touched as "foo" and "bar" don't exist */
+
+
+Copyright
+---------
+
+Copyright (c) 2009-2016 Petri Lehtinen <petri@digip.org>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+