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authorGravatar Federico Mena Quintero2013-06-28 20:02:20 -0500
committerGravatar Federico Mena Quintero2013-07-02 20:31:44 -0500
commit42892465d4522cf19283b8a06bf48104bb387430 (patch)
treecdb38bd51c5bdc3ab65541071b70b566be3a11d5
parentef73e32751e86eca9ae34160708233da401a3297 (diff)
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common: Add utils.[ch] with a string_concat() function
Instead of doing malloc() and repeated strcat(), which is an O(n^2) way to concatenate multiple strings, we define a single O(total_len) function that uses stpcpy(). This will also make the rest of the code more legible and safer.
-rw-r--r--common/Makefile.am3
-rw-r--r--common/utils.c85
-rw-r--r--common/utils.h27
3 files changed, 114 insertions, 1 deletions
diff --git a/common/Makefile.am b/common/Makefile.am
index 664e13b..20bfe4d 100644
--- a/common/Makefile.am
+++ b/common/Makefile.am
@@ -10,7 +10,8 @@ libinternalcommon_la_SOURCES = \
socket.c socket.h \
thread.c thread.h \
debug.c debug.h \
- userpref.c userpref.h
+ userpref.c userpref.h \
+ utils.c utils.h
if WIN32
libinternalcommon_la_LIBADD += -lole32
diff --git a/common/utils.c b/common/utils.c
new file mode 100644
index 0000000..b2b3768
--- /dev/null
+++ b/common/utils.c
@@ -0,0 +1,85 @@
+/*
+ * utils.c
+ * Miscellaneous utilities for string manipulation
+ *
+ * Copyright (c) 2013 Federico Mena Quintero
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <stdarg.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "utils.h"
+
+/**
+ * Concatenate strings into a newly allocated string
+ *
+ * @note: Specify NULL for the last string in the varargs list
+ *
+ * @str: The first string in the list
+ * @...: Subsequent strings. Use NULL for the last item.
+ *
+ * @return a newly allocated string, or NULL if @str is NULL. This will also
+ * return NULL and set errno to ENOMEM if memory is exhausted.
+ */
+char *string_concat(const char *str, ...)
+{
+ size_t len;
+ va_list args;
+ char *s;
+ char *result;
+ char *dest;
+
+ if (!str)
+ return NULL;
+
+ /* Compute final length */
+
+ len = strlen(str) + 1; /* plus 1 for the null terminator */
+
+ va_start(args, str);
+ s = va_arg(args, char *);
+ while (s) {
+ len += strlen(s);
+ s = va_arg(args, char*);
+ }
+ va_end(args);
+
+ /* Concat each string */
+
+ result = malloc(len);
+ if (!result)
+ return NULL; /* errno remains set */
+
+ dest = result;
+
+ dest = stpcpy(dest, str);
+
+ va_start(args, str);
+ s = va_arg(args, char *);
+ while (s) {
+ dest = stpcpy(dest, s);
+ s = va_arg(args, char *);
+ }
+ va_end(args);
+
+ return result;
+}
diff --git a/common/utils.h b/common/utils.h
new file mode 100644
index 0000000..129f974
--- /dev/null
+++ b/common/utils.h
@@ -0,0 +1,27 @@
+/*
+ * utils.h
+ * Miscellaneous utilities for string manipulation
+ *
+ * Copyright (c) 2013 Federico Mena Quintero
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef __UTILS_H
+#define __UTILS_H
+
+char *string_concat(const char *str, ...);
+
+#endif