unix, win: count null byte on UV_ENOBUFS

If an API function returns UV_ENOBUFS make sure we count the terminating
null, which we need space for. In case of success the null byte is not
included in the count, but the buffer *is* null terminated.

PR-URL: https://github.com/libuv/libuv/pull/690
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

docs/src/misc.rst

@@ -265,8 +265,9 @@ API
     `uv_os_homedir()` first checks the `HOME` environment variable using
     :man:`getenv(3)`. If `HOME` is not set, :man:`getpwuid_r(3)` is called. The
     user's home directory is stored in `buffer`. When `uv_os_homedir()` is
-    called, `size` indicates the maximum size of `buffer`. On success or
-    `UV_ENOBUFS` failure, `size` is set to the string length of `buffer`.
+    called, `size` indicates the maximum size of `buffer`. On success `size` is set
+    to the string length of `buffer`. On `UV_ENOBUFS` failure `size` is set to the
+    required length for `buffer`, including the null byte.
 
     .. warning::
         `uv_os_homedir()` is not thread safe.
@@ -281,8 +282,9 @@ API
     If none of these are found, the path `"/tmp"` is used, or, on Android,
     `"/data/local/tmp"` is used. The temp directory is stored in `buffer`. When
     `uv_os_tmpdir()` is called, `size` indicates the maximum size of `buffer`.
-    On success or `UV_ENOBUFS` failure, `size` is set to the string length of
-    `buffer` (which does not include the terminating null).
+    On success `size` is set to the string length of `buffer` (which does not
+    include the terminating null). On `UV_ENOBUFS` failure `size` is set to the
+    required length for `buffer`, including the null byte.
 
     .. warning::
         `uv_os_tmpdir()` is not thread safe.

src/fs-poll.c

@@ -139,7 +139,7 @@ int uv_fs_poll_getpath(uv_fs_poll_t* handle, char* buffer, size_t* size) {
 
   required_len = strlen(ctx->path);
   if (required_len >= *size) {
-    *size = required_len;
+    *size = required_len + 1;
     return UV_ENOBUFS;
   }
 

src/unix/core.c

@@ -1036,7 +1036,7 @@ int uv_os_homedir(char* buffer, size_t* size) {
     len = strlen(buf);
 
     if (len >= *size) {
-      *size = len;
+      *size = len + 1;
       return -ENOBUFS;
     }
 
@@ -1091,7 +1091,7 @@ int uv_os_homedir(char* buffer, size_t* size) {
   len = strlen(pw.pw_dir);
 
   if (len >= *size) {
-    *size = len;
+    *size = len + 1;
     uv__free(buf);
     return -ENOBUFS;
   }
@@ -1138,7 +1138,7 @@ return_buffer:
   len = strlen(buf);
 
   if (len >= *size) {
-    *size = len;
+    *size = len + 1;
     return -ENOBUFS;
   }
 

src/unix/pipe.c

@@ -235,7 +235,7 @@ static int uv__pipe_getsockpeername(const uv_pipe_t* handle,
 
 
   if (addrlen >= *size) {
-    *size = addrlen;
+    *size = addrlen + 1;
     return UV_ENOBUFS;
   }
 

src/uv-common.c

@@ -452,7 +452,7 @@ int uv_fs_event_getpath(uv_fs_event_t* handle, char* buffer, size_t* size) {
 
   required_len = strlen(handle->path);
   if (required_len >= *size) {
-    *size = required_len;
+    *size = required_len + 1;
     return UV_ENOBUFS;
   }
 

src/win/pipe.c

@@ -2040,7 +2040,7 @@ static int uv__pipe_getname(const uv_pipe_t* handle, char* buffer, size_t* size)
     goto error;
   } else if (pipe_prefix_len + addrlen >= *size) {
     /* "\\\\.\\pipe" + name */
-    *size = pipe_prefix_len + addrlen;
+    *size = pipe_prefix_len + addrlen + 1;
     err = UV_ENOBUFS;
     goto error;
   }

src/win/util.c

@@ -210,7 +210,7 @@ int uv_cwd(char* buffer, size_t* size) {
   if (r == 0) {
     return uv_translate_sys_error(GetLastError());
   } else if (r > (int) *size) {
-    *size = r -1;
+    *size = r;
     return UV_ENOBUFS;
   }
 
@@ -1218,7 +1218,7 @@ convert_buffer:
   if (bufsize == 0) {
     return uv_translate_sys_error(GetLastError());
   } else if (bufsize > *size) {
-    *size = bufsize - 1;
+    *size = bufsize;
     return UV_ENOBUFS;
   }
 
@@ -1263,7 +1263,7 @@ int uv_os_tmpdir(char* buffer, size_t* size) {
   if (bufsize == 0) {
     return uv_translate_sys_error(GetLastError());
   } else if (bufsize > *size) {
-    *size = bufsize - 1;
+    *size = bufsize;
     return UV_ENOBUFS;
   }