nasmlib: add function to splice pathnames

Add a function to splice a pathname consisting of a directory and a
filename.  It is worth noting that this function is limited to that
particular use case: in particular, it does NOT currently support
concatenating a filename which itself contains directory components to
a non-null directory.

Combining directory names is extremely system-dependent and probably
needs more than just parameterized code in many cases, for example,
on VMS combining "foo:[bar]" with "[baz]quux" should produce
"foo:[bar.baz]quux" whereas combining "foo:[bar]" and baz:quux" is an
outright error.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

2 files changed, 44 insertions, 1 deletions

diff --git a/include/nasmlib.h b/include/nasmlib.h
index 0b2bcb17..672764c6 100644
--- a/include/nasmlib.h
+++ b/include/nasmlib.h
@@ -395,7 +395,14 @@ char *nasm_opt_val(char *p, char **opt, char **val);
  *
  * The buffer returned must be freed by the caller
  */
-char *nasm_realpath(const char *rel_path);
+char * safe_alloc nasm_realpath(const char *rel_path);
+
+/*
+ * Path-splitting and merging functions
+ */
+char * safe_alloc nasm_dirname(const char *path);
+char * safe_alloc nasm_basename(const char *path);
+char * safe_alloc nasm_catfile(const char *dir, const char *path);
 
 const char * pure_func prefix_name(int);
 
diff --git a/nasmlib/path.c b/nasmlib/path.c
index 855440ea..72136546 100644
--- a/nasmlib/path.c
+++ b/nasmlib/path.c
@@ -42,17 +42,20 @@
 #if defined(unix) || defined(__unix) || defined(__unix__)
 # define separators "/"
 # define cleandirend "/"
+# define catsep '/'
 # define leaveonclean 1
 # define curdir "."
 #elif defined(__MSDOS__) || defined(__WINDOWS__) || \
     defined(__OS2__) || defined(_WIN16) || defined(_WIN32)
 # define separators "/\\:"
 # define cleandirend "/\\"
+# define catsep '\\'
 # define leaveonclean 2         /* Leave \\ at the start alone */
 # define curdir "."
 #elif defined(Macintosh)        /* MacOS classic? */
 # define separators ":"
 # define curdir ":"
+# define catsep ":"
 # define cleandirend ":"
 # define leaveonclean 0
 # define leave_leading 1
@@ -68,6 +71,10 @@
 # define curdir ""
 #endif
 
+/*
+ * This is an inline, because most compilers can greatly simplify this
+ * for a fixed string, like we have here.
+ */
 static inline bool ismatch(const char *charset, char ch)
 {
     const char *p;
@@ -129,3 +136,32 @@ char *nasm_dirname(const char *path)
 
     return nasm_strndup(path, p-path);
 }
+
+/* Concatenate a directory path and a filename */
+char *nasm_catfile(const char *dir, const char *file)
+{
+#ifndef catsep
+    return nasm_strcat(dir, file);
+#else
+    size_t dl = strlen(dir);
+    size_t fl = strlen(file);
+    char *p;
+    bool dosep = true;
+
+    if (!dl || ismatch(separators, dir[dl-1])) {
+        /* No separator necessary */
+        dosep = false;
+    }
+
+    p = nasm_malloc(dl + fl + dosep + 1);
+
+    memcpy(p, dir, dl);
+    p += dl;
+    if (dosep)
+        *p++ = catsep;
+
+    memcpy(p, file, fl+1);
+
+    return p;
+#endif
+}