fs: uv_fs_{open,read}_dir for unix

Tested on Linux, MacOS X, SmartOS and Windows.

Fixes #1430.

Makefile.am

@@ -140,6 +140,7 @@ test_run_tests_SOURCES = test/blackhole-server.c \
                          test/test-fs-event.c \
                          test/test-fs-poll.c \
                          test/test-fs.c \
+                         test/test-fs-readdir.c \
                          test/test-get-currentexe.c \
                          test/test-get-loadavg.c \
                          test/test-get-memory.c \

include/uv-unix.h

@@ -158,6 +158,13 @@ typedef gid_t uv_gid_t;
 typedef uid_t uv_uid_t;
 
 typedef struct dirent uv__dirent_t;
+/*
+ * "dirent" is used to hold a buffer large enough for any dirent in the
+ * directory being read. Avoids allocating for each directory entry.
+ */
+#define UV_DIR_PRIVATE_FIELDS \
+  uv__dirent_t* dirent; \
+  DIR* dir;
 
 #if defined(DT_UNKNOWN)
 # define HAVE_DIRENT_TYPES

include/uv-win.h

@@ -294,6 +294,29 @@ typedef struct uv__dirent_s {
   char d_name[1];
 } uv__dirent_t;
 
+/*
+ * "handle" is the actual directory handle that is used to perform calls
+ * to FindFirstFile/FindNextFile.
+ *
+ * "find_data" is needed to store the result of the FindFirstFile call that
+ * happened in uv_fs_opendir so that it can be used in the subsequent
+ * uv_fs_readdir call.
+ *
+ * "need_find_call" is a boolean determining if the next call to uv_fs_readdir
+ * must call FindNextFile. In uv_fs_opendir, FindFirstFile reads the first
+ * entry of the directory, and thus the subsequent call to uv_fs_readdir must
+ * not call FindNextFile, or otherwise it would miss the first directory entry.
+ * The next uv_fs_readdir calls after the first one will use FindNextFile.
+ *
+ * "dirent" is used to hold a buffer large enough for any dirent in the
+ * directory being read. It avoids allocating for each directory entry.
+ */
+#define UV_DIR_PRIVATE_FIELDS \
+  HANDLE dir_handle; \
+  WIN32_FIND_DATAW find_data; \
+  BOOL need_find_call; \
+  uv__dirent_t* dirent;
+
 #define UV__DT_DIR     UV_DIRENT_DIR
 #define UV__DT_FILE    UV_DIRENT_FILE
 #define UV__DT_LINK    UV_DIRENT_LINK

include/uv.h

@@ -197,6 +197,7 @@ typedef enum {
 /* Handle types. */
 typedef struct uv_loop_s uv_loop_t;
 typedef struct uv_handle_s uv_handle_t;
+typedef struct uv_dir_s uv_dir_t;
 typedef struct uv_stream_s uv_stream_t;
 typedef struct uv_tcp_s uv_tcp_t;
 typedef struct uv_udp_s uv_udp_t;
@@ -1033,13 +1034,20 @@ typedef enum {
   UV_FS_MKDTEMP,
   UV_FS_RENAME,
   UV_FS_SCANDIR,
+  UV_FS_OPENDIR,
+  UV_FS_READDIR,
+  UV_FS_CLOSEDIR,
   UV_FS_LINK,
   UV_FS_SYMLINK,
   UV_FS_READLINK,
   UV_FS_CHOWN,
   UV_FS_FCHOWN
 } uv_fs_type;
 
+struct uv_dir_s {
+  UV_DIR_PRIVATE_FIELDS
+};
+
 /* uv_fs_t is a subclass of uv_req_t. */
 struct uv_fs_s {
   UV_REQ_FIELDS
@@ -1050,6 +1058,9 @@ struct uv_fs_s {
   void* ptr;
   const char* path;
   uv_stat_t statbuf;  /* Stores the result of uv_fs_stat() and uv_fs_fstat(). */
+  const uv_dir_t* dir; /* Stores the result of uv_fs_opendir() */
+  uv_dirent_t* dirents;
+  size_t nentries;
   UV_FS_PRIVATE_FIELDS
 };
 
@@ -1102,6 +1113,22 @@ UV_EXTERN int uv_fs_scandir(uv_loop_t* loop,
                             uv_fs_cb cb);
 UV_EXTERN int uv_fs_scandir_next(uv_fs_t* req,
                                  uv_dirent_t* ent);
+
+UV_EXTERN int uv_fs_opendir(uv_loop_t* loop,
+                            uv_fs_t* req,
+                            const char* path,
+                            uv_fs_cb cb);
+UV_EXTERN int uv_fs_readdir(uv_loop_t* loop,
+                            uv_fs_t* req,
+                            const uv_dir_t* dir,
+                            uv_dirent_t dirents[],
+                            size_t nentries,
+                            uv_fs_cb cb);
+UV_EXTERN int uv_fs_closedir(uv_loop_t* loop,
+                             uv_fs_t* req,
+                             const uv_dir_t* dir,
+                             uv_fs_cb cb);
+
 UV_EXTERN int uv_fs_stat(uv_loop_t* loop,
                          uv_fs_t* req,
                          const char* path,