[vdagent-win PATCH v2 5/6] Factor out an utility function to read strings from registry

[Frediano Ziglio <fziglio@xxxxxxxxxx>]

Signed-off-by: Frediano Ziglio <fziglio@xxxxxxxxxx>
---
 vdagent/display_setting.cpp | 89 ++++++++++++++++++-------------------
 1 file changed, 44 insertions(+), 45 deletions(-)

diff --git a/vdagent/display_setting.cpp b/vdagent/display_setting.cpp
index cef3401..4b47276 100644
--- a/vdagent/display_setting.cpp
+++ b/vdagent/display_setting.cpp
@@ -282,30 +282,60 @@ bool DisplaySetting::disable_wallpaper()
     }
 }
 
-bool DisplaySetting::reload_wallpaper(HKEY desktop_reg_key)
+#if defined(UNICODE) || defined(_UNICODE)
+#define PRIsTSTR "ls"
+#else
+#define PRIsTSTR "s"
+#endif
+
+static bool RegReadString(HKEY key, const TCHAR *name, TCHAR *buffer, size_t buffer_len)
 {
-    TCHAR wallpaper_path[MAX_PATH + 1];
-    DWORD value_size = sizeof(wallpaper_path) - sizeof(wallpaper_path[0]);
+    DWORD value_size = buffer_len * sizeof(buffer[0]);
     DWORD value_type;
     LONG status;
-    TCHAR cur_wallpaper[MAX_PATH + 1];
 
-    vd_printf("");
-    status = RegQueryValueEx(desktop_reg_key, TEXT("Wallpaper"), NULL,
-                             &value_type, (LPBYTE)wallpaper_path, &value_size);
+    status = RegQueryValueEx(key, name, NULL, &value_type, (LPBYTE)buffer, &value_size);
+    if (status == ERROR_SUCCESS && value_type == REG_SZ) {
+        // assure NUL-terminated
+        value_size /= sizeof(buffer[0]);
+        if (value_size == buffer_len) {
+            // full buffer but not terminated?
+            if (buffer[value_size-1] != '\0') {
+                status = ERROR_MORE_DATA;
+            }
+        } else {
+            // append a NUL. If there's already a NUL character this
+            // new one will be ignored
+            buffer[value_size] = '\0';
+        }
+    }
     if (status != ERROR_SUCCESS) {
-        vd_printf("RegQueryValueEx(Wallpaper) : fail %ld", status);
+        vd_printf("RegQueryValueEx(%" PRIsTSTR ") : fail %ld", name, status);
         return false;
     }
 
     if (value_type != REG_SZ) {
-        vd_printf("bad wallpaper value type %lu (expected REG_SZ)", value_type);
+        vd_printf("bad %" PRIsTSTR " value type %lu (expected REG_SZ)", name, value_type);
         return false;
     }
 
-    value_size /= sizeof(wallpaper_path[0]);
-    if (!value_size || wallpaper_path[value_size - 1] != '\0') {
-        wallpaper_path[value_size] = '\0';
+    return true;
+}
+
+template <size_t N>
+static inline bool RegReadString(HKEY key, const TCHAR *name, TCHAR (&buffer)[N])
+{
+    return RegReadString(key, name, buffer, N);
+}
+
+bool DisplaySetting::reload_wallpaper(HKEY desktop_reg_key)
+{
+    TCHAR wallpaper_path[MAX_PATH + 1];
+    TCHAR cur_wallpaper[MAX_PATH + 1];
+
+    vd_printf("");
+    if (!RegReadString(desktop_reg_key, TEXT("Wallpaper"), wallpaper_path)) {
+        return false;
     }
 
     if (SystemParametersInfo(SPI_GETDESKWALLPAPER, SPICE_N_ELEMENTS(cur_wallpaper), cur_wallpaper, 0)) {
@@ -340,29 +370,13 @@ bool DisplaySetting::disable_font_smoothing()
 bool DisplaySetting::reload_font_smoothing(HKEY desktop_reg_key)
 {
     TCHAR smooth_value[4];
-    DWORD value_size = sizeof(smooth_value)-sizeof(smooth_value[0]);
-    DWORD value_type;
-    LONG status;
     BOOL cur_font_smooth;
 
     vd_printf("");
-    status = RegQueryValueEx(desktop_reg_key, TEXT("FontSmoothing"), NULL,
-                             &value_type, (LPBYTE)smooth_value, &value_size);
-    if (status != ERROR_SUCCESS) {
-        vd_printf("RegQueryValueEx(FontSmoothing) : fail %ld", status);
+    if (!RegReadString(desktop_reg_key, TEXT("FontSmoothing"), smooth_value)) {
         return false;
     }
 
-    if (value_type != REG_SZ) {
-        vd_printf("bad font smoothing value type %lu (expected REG_SZ)", value_type);
-        return false;
-    }
-
-    value_size /= sizeof(smooth_value[0]);
-    if (!value_size || smooth_value[value_size - 1] != '\0') {
-        smooth_value[value_size] = '\0';
-    }
-
     if (_tcscmp(smooth_value, TEXT("0")) == 0) {
         vd_printf("font smoothing is disabled in registry. do nothing");
         return true;
@@ -414,8 +428,6 @@ bool DisplaySetting::reload_win_animation(HKEY desktop_reg_key)
 {
     HKEY win_metrics_hkey;
     TCHAR win_anim_value[4];
-    DWORD value_size = sizeof(win_anim_value)-sizeof(win_anim_value[0]);
-    DWORD value_type;
     LONG status;
     ANIMATIONINFO active_win_animation;
 
@@ -428,26 +440,13 @@ bool DisplaySetting::reload_win_animation(HKEY desktop_reg_key)
         return false;
     }
 
-    status = RegQueryValueEx(win_metrics_hkey, TEXT("MinAnimate"), NULL,
-                             &value_type, (LPBYTE)win_anim_value, &value_size);
-    if (status != ERROR_SUCCESS) {
-        vd_printf("RegQueryValueEx(MinAnimate) : fail %ld", status);
+    if (!RegReadString(win_metrics_hkey, TEXT("MinAnimate"), win_anim_value)) {
         RegCloseKey(win_metrics_hkey);
         return false;
     }
 
     RegCloseKey(win_metrics_hkey);
 
-    if (value_type != REG_SZ) {
-        vd_printf("bad MinAnimate value type %lu (expected REG_SZ)", value_type);
-        return false;
-    }
-
-    value_size /= sizeof(win_anim_value[0]);
-    if (!value_size || win_anim_value[value_size - 1] != '\0') {
-        win_anim_value[value_size] = '\0';
-    }
-
     if (!_tcscmp(win_anim_value, TEXT("0"))) {
         vd_printf("window animation is disabled in registry. do nothing");
         return true;
-- 
2.17.0

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