Implemented UUID generation (RFC4122)

This patch adds new API:
  * xmpp_uuid_gen()

.gitignore

@@ -34,6 +34,7 @@ examples/basic
 examples/bot
 examples/component
 examples/roster
+examples/uuid
 test_stamp
 test-suite.log
 tests/*.o

Makefile.am

@@ -23,7 +23,7 @@ libstrophe_la_SOURCES = src/auth.c src/conn.c src/ctx.c \
 	src/event.c src/handler.c src/hash.c \
 	src/jid.c src/md5.c src/sasl.c src/scram.c src/sha1.c \
 	src/snprintf.c src/sock.c src/stanza.c src/thread.c \
-	src/tls_openssl.c src/util.c src/rand.c \
+	src/tls_openssl.c src/util.c src/rand.c src/uuid.c \
 	src/common.h src/hash.h src/md5.h src/ostypes.h src/parser.h \
 	src/sasl.h src/scram.h src/sha1.h src/sock.h src/thread.h src/tls.h \
 	src/util.h src/rand.h
@@ -42,7 +42,8 @@ pkgconfig_DATA = libstrophe.pc
 EXTRA_DIST = docs
 
 ## Examples
-noinst_PROGRAMS = examples/active examples/roster examples/basic examples/bot examples/component
+noinst_PROGRAMS = examples/active examples/roster examples/basic examples/bot \
+	examples/component examples/uuid
 examples_active_SOURCES = examples/active.c
 examples_active_CFLAGS = $(STROPHE_FLAGS)
 examples_active_LDADD = $(STROPHE_LIBS) 
@@ -58,6 +59,9 @@ examples_bot_LDADD = $(STROPHE_LIBS)
 examples_component_SOURCES = examples/component.c
 examples_component_CFLAGS = $(STROPHE_FLAGS)
 examples_component_LDADD = $(STROPHE_LIBS)
+examples_uuid_SOURCES = examples/uuid.c
+examples_uuid_CFLAGS = $(STROPHE_FLAGS)
+examples_uuid_LDADD = $(STROPHE_LIBS)
 
 
 ## Tests

examples/uuid.c

@@ -0,0 +1,23 @@
+#include <stdio.h>
+#include <strophe.h>
+
+int main(int argc, char **argv)
+{
+    xmpp_ctx_t *ctx;
+    char *uuid;
+    int rc = 0;
+
+    ctx = xmpp_ctx_new(NULL, NULL);
+
+    uuid = xmpp_uuid_gen(ctx);
+    if (uuid != NULL) {
+        printf("%s\n", uuid);
+        xmpp_free(ctx, uuid);
+    } else {
+        fprintf(stderr, "Couldn't allocate memory.\n");
+        rc = 1;
+    }
+
+    xmpp_ctx_free(ctx);
+    return rc;
+}

src/uuid.c

@@ -0,0 +1,70 @@
+/* uuid.c
+ * strophe XMPP client library -- UUID generation
+ *
+ * Copyright (C) 2015 Dmitry Podgorny <pasis.ua@gmail.com>
+ *
+ *  This software is provided AS-IS with no warranty, either express
+ *  or implied.
+ *
+ *  This program is dual licensed under the MIT and GPLv3 licenses.
+ */
+
+/** @file
+ *  Generation of UUID version 4 according to RFC4122.
+ */
+
+#include "strophe.h"
+#include "common.h"
+#include "rand.h"
+
+/** @def XMPP_UUID_LEN
+ *  UUID length in string representation excluding '\0'.
+ */
+#define XMPP_UUID_LEN 36
+
+/** Generate UUID version 4 in pre-allocated buffer.
+ *
+ *  @param uuid pre-allocated buffer of size (XMPP_UUID_LEN + 1)
+ */
+static void crypto_uuid_gen(xmpp_ctx_t *ctx, char *uuid)
+{
+    uint8_t buf[16];
+    int i = 0; /* uuid iterator */
+    int j = 0; /* buf iterator */
+
+    static const char hex[] = {'0', '1', '2', '3', '4', '5', '6', '7',
+                               '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+
+    xmpp_rand_bytes(ctx, buf, sizeof(buf));
+    buf[8] &= 0x3f;
+    buf[8] |= 0x80;
+    buf[6] &= 0x0f;
+    buf[6] |= 0x40;
+    while (i < XMPP_UUID_LEN) {
+        if (i == 8 || i == 13 || i == 18 || i == 23)
+            uuid[i++] = '-';
+        else {
+            uuid[i++] = hex[buf[j] >> 4];
+            uuid[i++] = hex[buf[j] & 0x0f];
+            ++j;
+        }
+    }
+    uuid[XMPP_UUID_LEN] = '\0';
+}
+
+/** Generate UUID version 4.
+ *  This function allocates memory for the resulting string and must be freed
+ *  with xmpp_free().
+ *
+ *  @return ASCIIZ string
+ */
+char *xmpp_uuid_gen(xmpp_ctx_t *ctx)
+{
+    char *uuid;
+
+    uuid = xmpp_alloc(ctx, XMPP_UUID_LEN + 1);
+    if (uuid != NULL) {
+        crypto_uuid_gen(ctx, uuid);
+    }
+    return uuid;
+}

strophe.h

@@ -363,6 +363,9 @@ void xmpp_iq_new();
 void xmpp_presence_new();
 */
 
+/** UUID **/
+char *xmpp_uuid_gen(xmpp_ctx_t *ctx);
+
 /** event loop **/
 void xmpp_run_once(xmpp_ctx_t *ctx, const unsigned long  timeout);
 void xmpp_run(xmpp_ctx_t *ctx);