[lttng-dev] [lttng-tools PATCH 1/4] Introduce a new utils_resolve_relative function

[Raphaël Beamonte]

This function aims to resolve relative path such as './' and
'../' in the middle of a path string. This allows to use paths
such as '~/../test' that are received as '/home/x/../test' for
instance.

Signed-off-by: Raphaël Beamonte <raphael.beamonte at gmail.com>
---
 src/common/utils.c |   68 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/common/utils.h |    1 +
 2 files changed, 69 insertions(+)

diff --git a/src/common/utils.c b/src/common/utils.c
index da4c036..4ccf36a 100644
--- a/src/common/utils.c
+++ b/src/common/utils.c
@@ -36,6 +36,74 @@
 #include "defaults.h"
 
 /*
+ * Resolve the './' and '../' strings in the middle of a path using
+ * our very own way to do it, so that it works even if the directory
+ * does not exist
+ */
+LTTNG_HIDDEN
+char *utils_resolve_relative(const char *path)
+{
+	char *next, *previous, *slash, *start_path, *absolute_path = NULL;
+
+	/* Safety net */
+	if (path == NULL) {
+		goto error;
+	}
+
+	/* Allocate memory for the absolute path */
+	absolute_path = zmalloc(PATH_MAX);
+	if (absolute_path == NULL) {
+		PERROR("zmalloc expand path");
+		goto error;
+	}
+
+	/* Copy the path in the absolute path */
+	strncpy(absolute_path, path, PATH_MAX);
+
+	/* As long as we find '/./' in the path string */
+	while ((next = strstr(absolute_path, "/./"))) {
+
+		/* We prepare the start_path not containing it */
+		start_path = strndup(absolute_path, next - absolute_path);
+
+		/* And we concatenate it with the part after this string */
+		snprintf(absolute_path, PATH_MAX, "%s%s", start_path, next + 2);
+
+		free(start_path);
+	}
+
+	/* As long as we find '/../' in the path string */
+	while ((next = strstr(absolute_path, "/../"))) {
+		/* If the path starts with '/../', there's a problem */
+		if (next == absolute_path) {
+			ERR("%s: Path cannot be resolved", path);
+			goto error;
+		}
+
+		/* We find the last level of directory */
+		previous = absolute_path;
+		while ((slash = strpbrk(previous + 1, "/")) && slash != next) {
+			previous = slash;
+		}
+
+		/* Then we prepare the start_path not containing it */
+		start_path = strndup(absolute_path, previous - absolute_path);
+
+		/* And we concatenate it with the part after the '/../' */
+		snprintf(absolute_path, PATH_MAX, "%s%s", start_path, next + 3);
+
+		free(start_path);
+	}
+
+	return absolute_path;
+
+error:
+	free(absolute_path);
+	return NULL;
+}
+
+
+/*
  * Return the realpath(3) of the path even if the last directory token does not
  * exist. For example, with /tmp/test1/test2, if test2/ does not exist but the
  * /tmp/test1 does, the real path is returned. In normal time, realpath(3)
diff --git a/src/common/utils.h b/src/common/utils.h
index 52f2798..c56942f 100644
--- a/src/common/utils.h
+++ b/src/common/utils.h
@@ -26,6 +26,7 @@
 #define MEBI_LOG2 20
 #define GIBI_LOG2 30
 
+char *utils_resolve_relative(const char *path);
 char *utils_expand_path(const char *path);
 int utils_create_pipe(int *dst);
 int utils_create_pipe_cloexec(int *dst);
-- 
1.7.10.4