From caf92856098ecfc9594deb597c4bef11f9277e96 Mon Sep 17 00:00:00 2001
From: Tobias Taschner <TcT2k@users.noreply.github.com>
Date: Sun, 19 Jan 2020 21:32:11 +0100
Subject: [PATCH] Improved JSON string parsing

---
 include/wx/private/json.h | 62 +++++++++++++++++++--------------------
 src/msw/webview_edge.cpp  |  5 +++-
 2 files changed, 34 insertions(+), 33 deletions(-)

diff --git a/include/wx/private/json.h b/include/wx/private/json.h
index 2e7bbaf7f8..f9ddff7fca 100644
--- a/include/wx/private/json.h
+++ b/include/wx/private/json.h
@@ -14,74 +14,72 @@ namespace wxJSON
 {
 
 // Decode a string literal including escape sequences
-// If the input is not quoted string it will be returned as the input
-wxString DecodeString(const wxString& str)
+// Returns false if the input string is not a valid JSON string
+bool DecodeString(const wxString& in, wxString* out)
 {
-    if (!str.starts_with('"') || !str.ends_with('"'))
-        return str;
-
-    wxString result;
-    const wxWCharBuffer buf = str.wc_str();
+    const wxWCharBuffer buf = in.wc_str();
+    const wchar_t* ch = buf.data();
+    // String has to chart with a quote
+    if (*(ch++) != '"')
+        return false;
+    out->reserve(buf.length());
     const wchar_t* end = buf.data() + buf.length() - 1;
-    for (const wchar_t* ch = buf.data() + 1; ch < end; ++ch)
+    for (; ch < end; ++ch)
     {
         if (*ch == '\\')
         {
             switch (*(++ch))
             {
             case 'b':
-                result.append('\b');
+                out->append('\b');
                 break;
             case 'n':
-                result.append('\n');
+                out->append('\n');
                 break;
             case 'r':
-                result.append('\r');
+                out->append('\r');
                 break;
             case 't':
-                result.append('\t');
+                out->append('\t');
                 break;
-            case 'v':
-                result.append('\v');
+            case 'f':
+                out->append('\f');
                 break;
-            case '\'':
-                result.append('\'');
+            case '/':
+                out->append('/');
                 break;
             case '"':
-                result.append('"');
+                out->append('"');
                 break;
             case '\\':
-                result.append('\\');
+                out->append('\\');
                 break;
             case 'u':
+#if SIZEOF_WCHAR_T == 2
+                            // In this case, we handle surrogates without doing anything special was wchar_t strings use UTF-17 encoding.
                 if (wxIsxdigit(ch[1]) && wxIsxdigit(ch[2]) &&
                     wxIsxdigit(ch[3]) && wxIsxdigit(ch[4]))
                 {
-                    wxUChar uchar = wxHexToDec(wxString(&ch[3], 2)) |
+                    wchar_t uchar = wxHexToDec(wxString(&ch[3], 2)) |
                         wxHexToDec(wxString(&ch[1], 2)) >> 8;
-                    result.append(uchar);
+                    out->append(uchar);
                     ch += 4;
                 }
+#else
+    #error Implement correct surrogate handling.
+#endif
                 break;
-            case 'x':
-                if (wxIsxdigit(ch[1]) && wxIsxdigit(ch[2]))
-                {
-                    wxChar hchar = wxHexToDec(wxString(&ch[1], 2));
-                    result.append(hchar);
-                    ch += 2;
-                }
-                break;
-
             default:
-                result.append(*ch);
+                return false;
                 break;
             }
         }
         else
-            result.append(*ch);
+            out->append(*ch);
     }
 
-    return result;
+    // String has to end with a quote
+    return (*ch) == '"';
 }
 
 } // namespace JSON
diff --git a/src/msw/webview_edge.cpp b/src/msw/webview_edge.cpp
index 10f71b50e9..df38961a3f 100644
--- a/src/msw/webview_edge.cpp
+++ b/src/msw/webview_edge.cpp
@@ -811,7 +811,10 @@ bool wxWebViewEdge::RunScript(const wxString& javascript, wxString* output)
         if (RunScriptSync(wrapJS.GetUnwrappedOutputCode() + ";", &result))
         {
             if (output)
-                *output = wxJSON::DecodeString(result);
+                // Try to decode JSON string or return original
+                // result if it's not a valid JSON string
+                if (!wxJSON::DecodeString(result, output))
+                    *output = result;
             result.clear();
         }