unix, windows: make uv_cwd be consistent with uv_exepath

Fixes #446

include/uv.h

@@ -2076,7 +2076,7 @@ UV_EXTERN int uv_inet_pton(int af, const char* src, void* dst);
 UV_EXTERN int uv_exepath(char* buffer, size_t* size);
 
 /* Gets the current working directory */
-UV_EXTERN int uv_cwd(char* buffer, size_t size);
+UV_EXTERN int uv_cwd(char* buffer, size_t* size);
 
 /* Changes the current working directory */
 UV_EXTERN int uv_chdir(const char* dir);

src/unix/core.c

@@ -589,16 +589,14 @@ ssize_t uv__recvmsg(int fd, struct msghdr* msg, int flags) {
 }
 
 
-int uv_cwd(char* buffer, size_t size) {
-  if (buffer == NULL)
+int uv_cwd(char* buffer, size_t* size) {
+  if (buffer == NULL || size == NULL)
     return -EINVAL;
 
-  if (size == 0)
-    return -EINVAL;
-
-  if (getcwd(buffer, size) == NULL)
+  if (getcwd(buffer, *size) == NULL)
     return -errno;
 
+  *size = strlen(buffer);
   return 0;
 }
 

src/win/util.c

@@ -163,12 +163,12 @@ int uv_exepath(char* buffer, size_t* size_ptr) {
 }
 
 
-int uv_cwd(char* buffer, size_t size) {
+int uv_cwd(char* buffer, size_t* size) {
   DWORD utf16_len;
   WCHAR utf16_buffer[MAX_PATH];
   int r;
 
-  if (buffer == NULL || size == 0) {
+  if (buffer == NULL || size == NULL) {
     return UV_EINVAL;
   }
 
@@ -192,19 +192,36 @@ int uv_cwd(char* buffer, size_t size) {
     utf16_buffer[utf16_len] = L'\0';
   }
 
+  /* Check how much space we need */
+  r = WideCharToMultiByte(CP_UTF8,
+                          0,
+                          utf16_buffer,
+                          -1,
+                          NULL,
+                          0,
+                          NULL,
+                          NULL);
+  if (r == 0) {
+    return uv_translate_sys_error(GetLastError());
+  } else if (r > (int) *size) {
+    *size = r;
+    return UV_ENOBUFS;
+  }
+
   /* Convert to UTF-8 */
   r = WideCharToMultiByte(CP_UTF8,
                           0,
                           utf16_buffer,
                           -1,
                           buffer,
-                          size > INT_MAX ? INT_MAX : (int) size,
+                          *size > INT_MAX ? INT_MAX : (int) *size,
                           NULL,
                           NULL);
   if (r == 0) {
     return uv_translate_sys_error(GetLastError());
   }
 
+  *size = r;
   return 0;
 }
 

test/test-cwd-and-chdir.c

@@ -33,8 +33,8 @@ TEST_IMPL(cwd_and_chdir) {
   char* last_slash;
   int err;
 
-  size = sizeof(buffer_orig) / sizeof(buffer_orig[0]);
-  err = uv_cwd(buffer_orig, size);
+  size = sizeof(buffer_orig);
+  err = uv_cwd(buffer_orig, &size);
   ASSERT(err == 0);
 
   /* Remove trailing slash unless at a root directory. */
@@ -55,7 +55,7 @@ TEST_IMPL(cwd_and_chdir) {
   err = uv_chdir(buffer_orig);
   ASSERT(err == 0);
 
-  err = uv_cwd(buffer_new, size);
+  err = uv_cwd(buffer_new, &size);
   ASSERT(err == 0);
 
   ASSERT(strcmp(buffer_orig, buffer_new) == 0);

test/test-fs.c

@@ -1465,8 +1465,10 @@ TEST_IMPL(fs_symlink_dir) {
 #ifdef _WIN32
   {
     static char src_path_buf[PATHMAX];
+    size_t size;
+    size = sizeof(src_path_buf);
     strcpy(src_path_buf, "\\\\?\\");
-    uv_cwd(src_path_buf + 4, sizeof(src_path_buf));
+    uv_cwd(src_path_buf + 4, &size);
     strcat(src_path_buf, "\\test_dir\\");
     test_dir = src_path_buf;
   }