GUACAMOLE-637: Add strlcpy() implementation. Use libc strlcpy() if available.

configure.ac

@@ -120,6 +120,11 @@ AC_CHECK_DECL([poll],
                [Whether poll() is defined])],,
 	[#include <poll.h>])
 
+AC_CHECK_DECL([strlcpy],
+	[AC_DEFINE([HAVE_STRLCPY],,
+               [Whether strlcpy() is defined])],,
+	[#include <string.h>])
+
 # Typedefs
 AC_TYPE_SIZE_T
 AC_TYPE_SSIZE_T

src/libguac/Makefile.am

@@ -61,6 +61,7 @@ libguacinc_HEADERS =                  \
     guacamole/socket-types.h          \
     guacamole/stream.h                \
     guacamole/stream-types.h          \
+    guacamole/string.h                \
     guacamole/timestamp.h             \
     guacamole/timestamp-types.h       \
     guacamole/unicode.h               \
@@ -96,6 +97,7 @@ libguac_la_SOURCES =   \
     socket-fd.c        \
     socket-nest.c      \
     socket-tee.c       \
+    string.c           \
     timestamp.c        \
     unicode.c          \
     user.c             \

src/libguac/guacamole/string.h

@@ -0,0 +1,68 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#ifndef GUAC_STRING_H
+#define GUAC_STRING_H
+
+/**
+ * Provides convenience functions for manipulating strings.
+ *
+ * @file string.h
+ */
+
+#include <stddef.h>
+#include <string.h>
+
+/**
+ * Copies a limited number of bytes from the given source string to the given
+ * destination buffer. The resulting buffer will always be null-terminated,
+ * even if doing so means that the intended string is truncated, unless the
+ * destination buffer has no space available at all. As this function always
+ * returns the length of the string it tried to create (the length of the
+ * source string), whether truncation has occurred can be detected by comparing
+ * the return value against the size of the destination buffer. If the value
+ * returned is greater than or equal to the size of the destination buffer, then
+ * the string has been truncated.
+ *
+ * The source and destination buffers MAY NOT overlap.
+ *
+ * @param dest
+ *     The buffer which should receive the contents of the source string. This
+ *     buffer will always be null terminated unless zero bytes are available
+ *     within the buffer.
+ *
+ * @param src
+ *     The source string to copy into the destination buffer. This string MUST
+ *     be null terminated.
+ *
+ * @param n
+ *     The number of bytes available within the destination buffer. If this
+ *     value is zero, no bytes will be written to the destination buffer, and
+ *     the destination buffer may not be null terminated. In all other cases,
+ *     the destination buffer will always be null terminated, even if doing
+ *     so means that the copied data from the source string will be truncated.
+ *
+ * @return
+ *     The length of the copied string (the source string) in bytes, excluding
+ *     the null terminator.
+ */
+size_t guac_strlcpy(char* restrict dest, const char* restrict src, size_t n);
+
+#endif
+

src/libguac/string.c

@@ -0,0 +1,52 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#include "config.h"
+
+#include <stddef.h>
+#include <string.h>
+
+size_t guac_strlcpy(char* restrict dest, const char* restrict src, size_t n) {
+
+#ifdef HAVE_STRLCPY
+    return strlcpy(dest, src, n);
+#else
+    /* Calculate actual length of desired string */
+    size_t length = strlen(src);
+
+    /* Copy nothing if there is no space */
+    if (n <= 0)
+        return length;
+
+    /* Calculate length of the string which will be copied */
+    size_t copy_length = length;
+    if (copy_length >= n)
+        copy_length = n - 1;
+
+    /* Copy only as much of string as possible, manually adding a null
+     * terminator */
+    memcpy(dest, src, copy_length);
+    dest[copy_length] = '\0';
+
+    /* Return the overall length of the desired string */
+    return length;
+#endif
+
+}
+