1 files changed, 76 insertions, 0 deletions
diff --git a/util/concat.c b/util/concat.c
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+/*  $Id$
+**
+**  Concatenate strings with dynamic memory allocation.
+**
+**  Written by Russ Allbery <rra@stanford.edu>
+**  This work is hereby placed in the public domain by its author.
+**
+**  Usage:
+** 
+**       string = concat(string1, string2, ..., (char *) 0);
+**       path = concatpath(base, name);
+**
+**  Dynamically allocates (using xmalloc) sufficient memory to hold all of
+**  the strings given and then concatenates them together into that
+**  allocated memory, returning a pointer to it.  Caller is responsible for
+**  freeing.  Assumes xmalloc is available.  The last argument must be a
+**  null pointer (to a char *, if you actually find a platform where it
+**  matters).
+**
+**  concatpath is similar, except that it only takes two arguments.  If the
+**  second argument begins with / or ./, a copy of it is returned;
+**  otherwise, the first argument, a slash, and the second argument are
+**  concatenated together and returned.  This is useful for building file
+**  names where names that aren't fully qualified are qualified with some
+**  particular directory.
+*/
+
+#include <config.h>
+#include <system.h>
+
+#include <util/util.h>
+
+/* Abbreviation for cleaner code. */
+#define VA_NEXT(var, type)      ((var) = (type) va_arg(args, type))
+
+/* ANSI C requires at least one named parameter. */
+char *
+concat(const char *first, ...)
+{
+    va_list args;
+    char *result, *p;
+    const char *string;
+    size_t length = 0;
+
+    /* Find the total memory required. */
+    va_start(args, first);
+    for (string = first; string != NULL; VA_NEXT(string, const char *))
+        length += strlen(string);
+    va_end(args);
+    length++;
+
+    /* Create the string.  Doing the copy ourselves avoids useless string
+       traversals of result, if using strcat, or string, if using strlen to
+       increment a pointer into result, at the cost of losing the native
+       optimization of strcat if any. */
+    result = xmalloc(length);
+    p = result;
+    va_start(args, first);
+    for (string = first; string != NULL; VA_NEXT(string, const char *))
+        while (*string != '\0')
+            *p++ = *string++;
+    va_end(args);
+    *p = '\0';
+
+    return result;
+}
+
+
+char *
+concatpath(const char *base, const char *name)
+{
+    if (name[0] == '/' || (name[0] == '.' && name[1] == '/'))
+        return xstrdup(name);
+    else
+        return concat(base != NULL ? base : ".", "/", name, (char *) 0);
+}