unix, windows: set required size on UV_ENOBUFS

When the supplied buffer is not big enough and UV_ENOBUFS is
returned, hint the user about the required size by setting
the len paramemeter to the required value.

Applies to:
- uv_pipe_getsockname
- uv_fs_event_getpath
- uv_fs_poll_getpath

include/uv.h

@@ -1203,9 +1203,12 @@ UV_EXTERN void uv_pipe_connect(uv_connect_t* req,
  *
  * A preallocated buffer must be provided. The len parameter holds the
  * length of the buffer and it's set to the number of bytes written to the
- * buffer on output.
+ * buffer on output. If the buffer is not big enough UV_ENOBUFS will be
+ * returned and len will contain the required size.
  */
-UV_EXTERN int uv_pipe_getsockname(const uv_pipe_t* handle, char* buf, size_t* len);
+UV_EXTERN int uv_pipe_getsockname(const uv_pipe_t* handle,
+                                  char* buf,
+                                  size_t* len);
 
 /*
  * This setting applies to Windows only.
@@ -1934,9 +1937,11 @@ UV_EXTERN int uv_fs_poll_start(uv_fs_poll_t* handle,
 UV_EXTERN int uv_fs_poll_stop(uv_fs_poll_t* handle);
 
 /*
- * Get the path befing monitored by the handle. The buffer must be preallocated
+ * Get the path being monitored by the handle. The buffer must be preallocated
  * by the user. Returns 0 on success or an error code < 0 in case of failure.
- * On sucess, `buf` will contain the path and `len` its length.
+ * On sucess, `buf` will contain the path and `len` its length. If the buffer
+ * is not big enough UV_ENOBUFS will be returned and len will be set to the
+ * required size.
  */
 UV_EXTERN int uv_fs_poll_getpath(uv_fs_poll_t* handle, char* buf, size_t* len);
 
@@ -2044,9 +2049,11 @@ UV_EXTERN int uv_fs_event_start(uv_fs_event_t* handle,
 UV_EXTERN int uv_fs_event_stop(uv_fs_event_t* handle);
 
 /*
- * Get the path befing monitored by the handle. The buffer must be preallocated
+ * Get the path being monitored by the handle. The buffer must be preallocated
  * by the user. Returns 0 on success or an error code < 0 in case of failure.
- * On sucess, `buf` will contain the path and `len` its length.
+ * On sucess, `buf` will contain the path and `len` its length. If the buffer
+ * is not big enough UV_ENOBUFS will be returned and len will be set to the
+ * required size.
  */
 UV_EXTERN int uv_fs_event_getpath(uv_fs_event_t* handle,
                                   char* buf,

src/fs-poll.c

@@ -132,7 +132,7 @@ int uv_fs_poll_getpath(uv_fs_poll_t* handle, char* buf, size_t* len) {
 
   required_len = strlen(ctx->path) + 1;
   if (required_len > *len) {
-    *len = 0;
+    *len = required_len;
     return UV_ENOBUFS;
   }
 

src/unix/pipe.c

@@ -233,7 +233,7 @@ int uv_pipe_getsockname(const uv_pipe_t* handle, char* buf, size_t* len) {
 
 
   if (addrlen > *len) {
-    *len = 0;
+    *len = addrlen;
     return UV_ENOBUFS;
   }
 

src/uv-common.c

@@ -455,7 +455,7 @@ int uv_fs_event_getpath(uv_fs_event_t* handle, char* buf, size_t* len) {
 
   required_len = strlen(handle->path) + 1;
   if (required_len > *len) {
-    *len = 0;
+    *len = required_len;
     return UV_ENOBUFS;
   }
 

src/win/pipe.c

@@ -1779,8 +1779,10 @@ int uv_pipe_getsockname(const uv_pipe_t* handle, char* buf, size_t* len) {
   if (nt_status == STATUS_BUFFER_OVERFLOW) {
     name_size = sizeof(*name_info) + tmp_name_info.FileNameLength;
     name_info = malloc(name_size);
-    if (!name_info)
-      uv_fatal_error(ERROR_OUTOFMEMORY, "malloc");
+    if (!name_info) {
+      *len = 0;
+      return UV_ENOMEM;
+    }
 
     nt_status = pNtQueryInformationFile(handle->handle,
                                         &io_status,
@@ -1790,6 +1792,7 @@ int uv_pipe_getsockname(const uv_pipe_t* handle, char* buf, size_t* len) {
   }
 
   if (nt_status != STATUS_SUCCESS) {
+    *len = 0;
     err = uv_translate_sys_error(pRtlNtStatusToDosError(nt_status));
     goto error;
   }
@@ -1804,6 +1807,7 @@ int uv_pipe_getsockname(const uv_pipe_t* handle, char* buf, size_t* len) {
   }
 
   if (name_len == 0) {
+    *len = 0;
     err = 0;
     goto error;
   }
@@ -1820,10 +1824,12 @@ int uv_pipe_getsockname(const uv_pipe_t* handle, char* buf, size_t* len) {
                                 NULL,
                                 NULL);
   if (!addrlen) {
+    *len = 0;
     err = uv_translate_sys_error(GetLastError());
     goto error;
   } else if (pipe_prefix_len + addrlen + 1 > *len) {
     /* "\\\\.\\pipe" + name + '\0' */
+    *len = pipe_prefix_len + addrlen + 1;
     err = UV_ENOBUFS;
     goto error;
   }
@@ -1838,6 +1844,7 @@ int uv_pipe_getsockname(const uv_pipe_t* handle, char* buf, size_t* len) {
                                 NULL,
                                 NULL);
   if (!addrlen) {
+    *len = 0;
     err = uv_translate_sys_error(GetLastError());
     goto error;
   }
@@ -1850,6 +1857,5 @@ int uv_pipe_getsockname(const uv_pipe_t* handle, char* buf, size_t* len) {
 
 error:
   free(name_info);
-  *len = 0;
   return err;
 }