Add readlink, xreadlink(), and change xrealloc() to not fight the stupid

compiler so much.

2 files changed, 31 insertions, 4 deletions

diff --git a/lib/lib.c b/lib/lib.c
index 6c8abb03..1f37eb59 100644
--- a/lib/lib.c
+++ b/lib/lib.c
@@ -94,10 +94,12 @@ void *xzalloc(size_t size)
 
 // Die unless we can change the size of an existing allocation, possibly
 // moving it.  (Notice different arguments from libc function.)
-void xrealloc(void **ptr, size_t size)
+void *xrealloc(void *ptr, size_t size)
 {
-	*ptr = realloc(*ptr, size);
-	if (!*ptr) error_exit("xrealloc");
+	ptr = realloc(ptr, size);
+	if (!ptr) error_exit("xrealloc");
+
+	return ptr;
 }
 
 // Die unless we can allocate a copy of this many bytes of string.
@@ -452,6 +454,30 @@ off_t fdlength(int fd)
 	return pos + 1;
 }
 
+// This can return null (meaning file not found).  It just won't return null
+// for memory allocation reasons.
+char *xreadlink(char *name)
+{
+	int len, size = 0;
+	char *buf = 0;
+
+	// Grow by 64 byte chunks until it's big enough.
+	for(;;) {
+		size +=64;
+		buf = xrealloc(buf, size);
+		len = readlink(name, buf, size);
+
+		if (len<0) {
+			free(buf);
+			return 0;
+		}
+		if (len<size) {
+			buf[len]=0;
+			return buf;
+		}
+	}
+}
+
 /*
  This might be of use or might not.  Unknown yet...
 
diff --git a/lib/lib.h b/lib/lib.h
index e2d055bc..c95a743e 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -40,7 +40,7 @@ void usage_exit(void);
 void strlcpy(char *dest, char *src, size_t size);
 void *xmalloc(size_t size);
 void *xzalloc(size_t size);
-void xrealloc(void **ptr, size_t size);
+void *xrealloc(void *ptr, size_t size);
 void *xstrndup(char *s, size_t n);
 void *xstrdup(char *s);
 char *xmsprintf(char *format, ...);
@@ -67,6 +67,7 @@ char *utoa(unsigned n);
 char *itoa(int n);
 long atolx(char *c);
 off_t fdlength(int fd);
+char *xreadlink(char *name);
 struct dirtree *read_dirtree_node(char *path);
 struct dirtree *read_dirtree(char *path, struct dirtree *parent);