[vdagent-win PATCH 12/13] 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 | 97 +++++++++++++++++++++----------------
 1 file changed, 54 insertions(+), 43 deletions(-)

diff --git a/vdagent/display_setting.cpp b/vdagent/display_setting.cpp
index 5585bb5..cdc42c7 100644
--- a/vdagent/display_setting.cpp
+++ b/vdagent/display_setting.cpp
@@ -282,30 +282,70 @@ bool DisplaySetting::disable_wallpaper()
     }
 }
 
-bool DisplaySetting::reload_wallpaper(HKEY desktop_reg_key)
+template <typename T>
+static bool RegReadString(HKEY key, const T *name, T *buffer, size_t buffer_len)
 {
-    TCHAR wallpaper_path[MAX_PATH + 1];
-    DWORD value_size = sizeof(wallpaper_path) - sizeof(wallpaper_path[0]);
+    static_assert(sizeof(T) == sizeof(char) || sizeof(T) == sizeof(WCHAR));
+    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);
+    if (sizeof(T) == sizeof(char)) {
+        status = RegQueryValueExA(key, (const char*) name, NULL,
+                                  &value_type, (LPBYTE)buffer, &value_size);
+    } else {
+        status = RegQueryValueExW(key, (LPCWSTR) 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);
+        if (sizeof(T) == sizeof(char)) {
+            vd_printf("RegQueryValueEx(%s) : fail %ld", (const char*) name, status);
+        } else {
+            vd_printf("RegQueryValueEx(%ls) : fail %ld", (LPCWSTR) name, status);
+        }
         return false;
     }
 
     if (value_type != REG_SZ) {
-        vd_printf("bad wallpaper value type %lu (expected REG_SZ)", value_type);
+        if (sizeof(T) == sizeof(char)) {
+            vd_printf("bad %s value type %lu (expected REG_SZ)", (const char*) name, value_type);
+        } else {
+            vd_printf("bad %ls value type %lu (expected REG_SZ)", (LPCWSTR) 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 <typename T, size_t N>
+static inline bool RegReadString(HKEY key, const T *name, T (&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)) {
@@ -340,28 +380,13 @@ bool DisplaySetting::disable_font_smoothing()
 bool DisplaySetting::reload_font_smoothing(HKEY desktop_reg_key)
 {
     CHAR smooth_value[4+1];
-    DWORD value_size = sizeof(smooth_value)-1;
-    DWORD value_type;
-    LONG status;
     BOOL cur_font_smooth;
 
     vd_printf("");
-    status = RegQueryValueExA(desktop_reg_key, "FontSmoothing", NULL,
-                              &value_type, (LPBYTE)smooth_value, &value_size);
-    if (status != ERROR_SUCCESS) {
-        vd_printf("RegQueryValueEx(FontSmoothing) : fail %ld", status);
-        return false;
-    }
-
-    if (value_type != REG_SZ) {
-        vd_printf("bad font smoothing value type %lu (expected REG_SZ)", value_type);
+    if (!RegReadString(desktop_reg_key, "FontSmoothing", smooth_value)) {
         return false;
     }
 
-    if (!value_size || smooth_value[value_size - 1] != '\0') {
-        smooth_value[value_size] = '\0';
-    }
-
     if (strcmp(smooth_value, "0") == 0) {
         vd_printf("font smoothing is disabled in registry. do nothing");
         return true;
@@ -413,8 +438,6 @@ bool DisplaySetting::reload_win_animation(HKEY desktop_reg_key)
 {
     HKEY win_metrics_hkey;
     CHAR win_anim_value[4+1];
-    DWORD value_size = sizeof(win_anim_value)-1;
-    DWORD value_type;
     LONG status;
     ANIMATIONINFO active_win_animation;
 
@@ -427,25 +450,13 @@ bool DisplaySetting::reload_win_animation(HKEY desktop_reg_key)
         return false;
     }
 
-    status = RegQueryValueExA(win_metrics_hkey, "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, "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;
-    }
-
-    if (!value_size || win_anim_value[value_size - 1] != '\0') {
-        win_anim_value[value_size] = '\0';
-    }
-
     if (!strcmp(win_anim_value, "0")) {
         vd_printf("window animation is disabled in registry. do nothing");
         return true;
-- 
2.17.0

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