win32: introduce relative path handling function

Add a function that takes a (possibly) relative UTF-8 path and emits a
UTF-16 path with forward slashes translated to backslashes.  If the
given path is, in fact, absolute, it will be translated to absolute path
handling rules.

2 files changed, 41 insertions, 2 deletions

diff --git a/src/win32/path_w32.c b/src/win32/path_w32.c
index eda85abf4..18b43e728 100644
--- a/src/win32/path_w32.c
+++ b/src/win32/path_w32.c
@@ -25,6 +25,9 @@
 #define path__is_unc(p) \
 	(((p)[0] == '\\' && (p)[1] == '\\') || ((p)[0] == '/' && (p)[1] == '/'))
 
+#define path__startswith_slash(p) \
+	((p)[0] == '\\' || (p)[0] == '/')
+
 GIT_INLINE(int) path__cwd(wchar_t *path, int size)
 {
 	int len;
@@ -221,7 +224,7 @@ int git_win32_path_from_utf8(git_win32_path out, const char *src)
 			goto on_error;
 	}
 	/* Absolute paths omitting the drive letter */
-	else if (src[0] == '\\' || src[0] == '/') {
+	else if (path__startswith_slash(src)) {
 		if (path__cwd(dest, MAX_PATH) < 0)
 			goto on_error;
 
@@ -257,6 +260,30 @@ on_error:
 	return -1;
 }
 
+int git_win32_path_relative_from_utf8(git_win32_path out, const char *src)
+{
+	wchar_t *dest = out, *p;
+	int len;
+
+	/* Handle absolute paths */
+	if (git_path_is_absolute(src) ||
+	    path__is_nt_namespace(src) ||
+	    path__is_unc(src) ||
+	    path__startswith_slash(src)) {
+		return git_win32_path_from_utf8(out, src);
+	}
+
+	if ((len = git__utf8_to_16(dest, MAX_PATH, src)) < 0)
+		return -1;
+
+	for (p = dest; p < (dest + len); p++) {
+		if (*p == L'/')
+			*p = L'\\';
+	}
+
+	return len;
+}
+
 int git_win32_path_to_utf8(git_win32_utf8_path dest, const wchar_t *src)
 {
 	char *out = dest;
diff --git a/src/win32/path_w32.h b/src/win32/path_w32.h
index 6d546f2f8..dab8b96fa 100644
--- a/src/win32/path_w32.h
+++ b/src/win32/path_w32.h
@@ -11,7 +11,9 @@
 #include "vector.h"
 
 /**
- * Create a Win32 path (in UCS-2 format) from a UTF-8 string.
+ * Create a Win32 path (in UCS-2 format) from a UTF-8 string.  If the given
+ * path is relative, then it will be turned into an absolute path by having
+ * the current working directory prepended.
  *
  * @param dest The buffer to receive the wide string.
  * @param src The UTF-8 string to convert.
@@ -20,6 +22,16 @@
 extern int git_win32_path_from_utf8(git_win32_path dest, const char *src);
 
 /**
+ * Create a Win32 path (in UCS-2 format) from a UTF-8 string.  If the given
+ * path is relative, then it will not be turned into an absolute path.
+ *
+ * @param dest The buffer to receive the wide string.
+ * @param src The UTF-8 string to convert.
+ * @return The length of the wide string, in characters (not counting the NULL terminator), or < 0 for failure
+ */
+extern int git_win32_path_relative_from_utf8(git_win32_path dest, const char *src);
+
+/**
  * Canonicalize a Win32 UCS-2 path so that it is suitable for delivery to the
  * Win32 APIs: remove multiple directory separators, squashing to a single one,
  * strip trailing directory separators, ensure directory separators are all