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Unified Diff: src/shared/Registry.cpp

Issue 5171515343503360: Issue #41 - Bring method of determining IE version up to date (Closed)
Patch Set: simplify Registry_Key Created July 26, 2014, 5 p.m.
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Index: src/shared/Registry.cpp
===================================================================
new file mode 100644
--- /dev/null
+++ b/src/shared/Registry.cpp
@@ -0,0 +1,70 @@
+#include "Registry.h"
+#include <memory>
+
+using namespace AdblockPlus;
+
+Registry_Key::Registry_Key(HKEY parent, std::wstring key_name)
+{
+ if (key_name.empty())
+ {
+ throw std::runtime_error("key_name may not be empty");
+ }
+ HRESULT hr = RegOpenKeyExW(parent, key_name.c_str(), 0, KEY_QUERY_VALUE, &key);
+ if (hr != ERROR_SUCCESS || !key)
+ {
+ throw std::runtime_error("Failure in RegOpenKeyExW");
+ }
+}
+
+Registry_Key::~Registry_Key()
+{
+ RegCloseKey(key);
+}
+
+std::wstring Registry_Key::value_wstring(std::wstring name) const
+{
+ /*
+ * Step one is to determine the presence of the value, along with its type and byte size.
+ */
+ DWORD type;
+ DWORD size = 0;
+ HRESULT hr = ::RegQueryValueExW(static_cast<HKEY>(key), name.c_str(), 0, &type, 0, &size);
+ if (hr != ERROR_SUCCESS)
+ {
+ throw std::runtime_error("Failure in RegQueryValueEx to query name");
sergei 2014/07/28 11:46:27 It's not descriptive. Is it possible to find a roo
Eric 2014/07/29 12:42:25 No, it's not, and it doesn't really matter at the
sergei 2014/07/29 14:45:56 It does always matter. - There is no real reason t
Eric 2014/07/29 15:17:22 Yes, and when we get unified and regular error han
sergei 2014/07/30 10:42:04 I'm pretty sure that std::system_error can be used
Eric 2014/07/30 13:02:04 It's not the exception that's the main problem, it
+ }
+ if (type != REG_SZ)
+ {
+ throw std::runtime_error("Value is not string type");
sergei 2014/07/28 11:46:27 The same as above, it's completely not descriptive
+ }
+
+ /*
+ * Step two is to allocate a buffer for the string and query for its value.
+ * Note that 'size' is the size in bytes, which we need for the system call,
+ * but that 'psize' is the size in words, which we need to manipulate the wchar_t array 'p'.
+ */
+ // Round the byte size up to the nearest multiple of two.
+ size = (size + 1) & ~ DWORD(1);
+ size_t psize = size >> 1;
+ // We need to allocate a temporary buffer to receive the value, because there's no interface to write directly into the buffer of std::basic_string.
+ std::unique_ptr< wchar_t[] > p(new wchar_t[ psize ]);
sergei 2014/07/28 11:46:27 not sure about it, One one hand it's correct, but
Eric 2014/07/29 12:42:25 We need an allocated buffer, because writing into
sergei 2014/07/29 14:45:56 But we have already decided, that `&x[0]` is OK fo
Eric 2014/07/29 15:17:22 I am not convinced that we have already decided th
+ hr = RegQueryValueExW(key, name.c_str(), 0, 0, reinterpret_cast<BYTE*>(p.get()), &size);
+ if (hr != ERROR_SUCCESS)
+ {
+ throw std::runtime_error("Failure in RegQueryValueExW to retrieve value");
+ }
+
+ /*
+ * Step three is to construct a return string.
+ *
+ * There's the possibility of an extra terminating null character in the return value of the query.
+ * If so, we have to decrement the length of the return value to eliminate it.
+ * If it persists, it will interfere with later string operations such as concatenation.
+ */
+ if (p[ psize - 1 ] == L'\0')
Oleksandr 2014/07/27 22:13:30 Nit: No spaces before and after array index: if (
+ {
+ --psize;
+ }
+ return std::wstring(p.get(), psize);
+}
+

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