libc: Implement freopen()

libs/libc/include/stdio.h

@@ -42,6 +42,9 @@ extern "C"
     /* Returns a new file associated with the file descriptor fd. */
     FILE* fdopen(int fd, const char* mode);
 
+    /* Opens the file specified by pathname and points the file handle stream to it. */
+    FILE* freopen(const char* pathname, const char* mode, FILE* stream);
+
     /* Returns the file descriptor associated with the file stream. */
     int fileno(FILE* stream);
 

libs/libc/src/file.cpp

@@ -51,6 +51,20 @@ extern "C"
         return stream;
     }
 
+    FILE* freopen(const char* pathname, const char* mode,
+                  FILE* stream) // FIXME: If pathname is NULL, open the original file with the new mode.
+    {
+        int fd = open(pathname, O_RDWR); // FIXME: Use the mode string.
+        if (fd < 0) { return 0; }
+
+        fflush(stream); // To make it future-proof.
+        fclose(stream);
+
+        stream->f_fd = fd;
+        clearerr(stream);
+        return stream;
+    }
+
     int fileno(FILE* stream)
     {
         return stream->f_fd;