[RFC PATCH 2/6] Add libiberty/concat styled concat_path function

[Omair Javaid <omair.javaid@linaro.org>]

From: Philipp Rudo <prudo@linux.ibm.com>

    This commit adds concat_path function to concatenate an arbitrary number of
    path elements.  The function automatically adds an directory separator between
    two elements as needed.

gdb/ChangeLog:

	* common/common-utils.h (endswith): New function.
	* utils.c (_concat_path, approx_path_length): New function.
	* utils.h (_concat_path): New export.
	(concat_path): New define.
---
 gdb/common/common-utils.h | 11 +++++++++++
 gdb/utils.c               | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 gdb/utils.h               | 16 ++++++++++++++++
 3 files changed, 73 insertions(+)

diff --git a/gdb/common/common-utils.h b/gdb/common/common-utils.h
index b2cb516..bb7c5b1 100644
--- a/gdb/common/common-utils.h
+++ b/gdb/common/common-utils.h
@@ -109,6 +109,17 @@ startswith (const char *string, const char *pattern)
   return strncmp (string, pattern, strlen (pattern)) == 0;
 }
 
+/* Return non-zero if the end of STRING matches PATTERN, zero
+   otherwise.  */
+
+static inline int
+endswith (const char *string, const char *pattern)
+{
+  return (strlen (string) > strlen (pattern)
+	  && strncmp (string + strlen (string) - strlen (pattern), pattern,
+		      strlen (pattern)) == 0);
+}
+
 ULONGEST strtoulst (const char *num, const char **trailer, int base);
 
 /* Skip leading whitespace characters in INP, returning an updated
diff --git a/gdb/utils.c b/gdb/utils.c
index 2394443..8c8e152 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -3077,6 +3077,52 @@ substitute_path_component (std::string &str, const std::string &from,
     }
 }
 
+/* Approximate length of final path.  Helper for concat_path.  */
+
+static inline unsigned long
+approx_path_length (const std::initializer_list<const std::string> args,
+		    const std::string &dir_separator)
+{
+  size_t length = 0;
+
+  for (const std::string &arg: args)
+      length += arg.length () + dir_separator.length ();
+
+  return length;
+}
+
+/* See utils.h.  */
+
+std::string
+_concat_path (const std::initializer_list<const std::string> args,
+	      const std::string &dir_separator)
+{
+  std::string ret;
+  ret.reserve (approx_path_length (args, dir_separator));
+
+  for (const std::string &arg : args)
+    {
+      if (arg.empty ())
+	continue;
+
+      if (startswith (arg.c_str (), dir_separator.c_str ())
+	  && endswith (ret.c_str (), dir_separator.c_str ()))
+	ret.erase (ret.length () - dir_separator.length (),
+		   dir_separator.length ());
+
+      else if (!ret.empty ()
+	       && !startswith (arg.c_str (), dir_separator.c_str ())
+	       && !endswith (ret.c_str (), dir_separator.c_str ())
+	       && ret != TARGET_SYSROOT_PREFIX)
+	ret += dir_separator;
+
+      ret += arg;
+    }
+
+  ret.shrink_to_fit ();
+  return ret;
+}
+
 #ifdef HAVE_WAITPID
 
 #ifdef SIGALRM
diff --git a/gdb/utils.h b/gdb/utils.h
index bc319de..f8178f8 100644
--- a/gdb/utils.h
+++ b/gdb/utils.h
@@ -301,6 +301,22 @@ extern void substitute_path_component (std::string &str,
 				       const std::string &from,
 				       const std::string &to);
 
+/* Concatenate an arbitrary number of path elements.  Adds and removes
+   directory separators as needed.
+
+   concat_path (/first, second)		=> /first/second
+   concat_path (first, second)		=> first/second
+   concat_path (first/, second)		=> first/second
+   concat_path (first, /second)		=> first/second
+   concat_path (first/, /second)	=> first/second
+   concat_path (target:, second)	=> target:second
+   */
+
+extern std::string _concat_path (const std::initializer_list<const std::string> args,
+				 const std::string &dir_separator);
+
+#define concat_path(...) _concat_path ({__VA_ARGS__}, SLASH_STRING)
+
 std::string ldirname (const char *filename);
 
 extern int count_path_elements (const char *path);
-- 
2.7.4