I am attempting to convert an array of bytes to a base64 encoded String using the EncodeBytesToString method of the TBase64Encoding class. The documentation for EncodeBytesToString states:
"Returns a string with the input array of bytes encoded up to the specified number of bytes."
Therefore, I attempted to encode my byte array like so:
TFile * File = new TFile();
TBytes Bytes = File->ReadAllBytes("D:\\Sample.pdf");
TBase64Encoding * Encoder = new TBase64Encoding();
String EncodedBytes = Encoder->EncodeBytesToString(Bytes, Bytes.Length);
However, I get the following error:
E2285 Could not find a match for 'TNetEncoding::EncodeBytesToString(TByteDynArray,int)'
I am confused, as the documentation seems to say that I should pass a TBytes object and an int into this function. What am I missing here?
Try this:
//------------------------------------------------------------------------------
String __fastcall BytesToBase64( TByteDynArray _ArrayIn )
{
TBase64Encoding * Encoding = new TBase64Encoding( 64, '\n' );
String Result = Encoding->EncodeBytesToString( &_ArrayIn[0], _ArrayIn.High );
delete Encoding;
return Result;
}
//------------------------------------------------------------------------------
TByteDynArray __fastcall Base64ToBytes( String _64String )
{
TByteDynArray My64Bytes = _64String.BytesOf();
return TNetEncoding::Base64->Decode(&My64Bytes[0], My64Bytes.High);
}
//------------------------------------------------------------------------------
System.NetEncoding.TNetEncoding provides the static property Base64 to retrieve an instance of TNetEncoding for base64 encoding.
So this will also work:
String __fastcall BytesToBase64(TByteDynArray _ArrayIn)
{
return TNetEncoding::Base64->EncodeBytesToString(&_ArrayIn[0], _ArrayIn.High);
}
Related
I'm trying to use System.IO.Pipelines to parse large text files.
But I can't find no conversion function from ReadOnlySequence to ReadOnlySequence. For example like MemoryMarshal.Cast<byte,char>.
IMHO it is pretty useless having a generic ReadOnlySequence<T> if there is only one particular type (byte) applicable.
static async Task ReadPipeAsync(PipeReader reader, IStringValueFactory factory)
{
while (true)
{
ReadResult result = await reader.ReadAsync();
ReadOnlySequence<byte> buffer = result.Buffer;
//ReadOnlySequence<char> chars = buffer.CastTo<char>(); ???
}
}
You would have to write a conversion operator to achieve this cast. You cannot cast it explicitly. Be aware that a char[] is two bytes, so you need to choose your encoding algorithm.
IMHO it is pretty useless having a generic ReadOnlySequence<T> if
there is only one particular type (byte) applicable.
While it's true that System.IO.Pipelines will only give you a ReadOnlySequence<byte> because of the fact that a PipeReader is attached to a Stream which is just a stream of bytes, there are other use cases for a ReadOnlySequence<T> eg,
ReadOnlySequence<char> roChars = new ReadOnlySequence<char>("some chars".ToCharArray());
ReadOnlySequence<string> roStrings = new ReadOnlySequence<string>(new string[] { "string1", "string2", "Another String" });
Your conversion operator would have similar logic to the below, but you would set your encoding appropriately.
static void Main(string[] args)
{
// create a 64k Readonly sequence of random bytes
var ros = new ReadOnlySequence<byte>(GenerateRandomBytes(64000));
//Optionally extract the section of the ReadOnlySequence we are interested in
var mySlice = ros.Slice(22222, 55555);
char[] charArray;
// Check if the slice is a single segment - not really necessary
// included for explanation only
if(mySlice.IsSingleSegment)
{
charArray = Encoding.ASCII.GetString(mySlice.FirstSpan).ToCharArray();
}
else
// Could only do this and always assume multiple spans
// which is highly likley for a PipeReader stream
{
Span<byte> theSpan = new byte[ros.Length];
mySlice.CopyTo(theSpan);
// ASCII Encoding - one byte of span = 2 bytes of char
charArray = Encoding.ASCII.GetString(theSpan).ToCharArray();
}
// Convert the char array back to a ReadOnlySegment<char>
var rosChar = new ReadOnlySequence<char>(charArray);
}
public static byte[] GenerateRandomBytes(int length)
{
// Create a buffer
byte[] randBytes;
if (length >= 1)
randBytes = new byte[length];
else
randBytes = new byte[1];
// Create a new RNGCryptoServiceProvider.
System.Security.Cryptography.RNGCryptoServiceProvider rand =
new System.Security.Cryptography.RNGCryptoServiceProvider();
// Fill the buffer with random bytes.
rand.GetBytes(randBytes);
// return the bytes.
return randBytes;
}
Am using wcstod() to convert to numeric type text data which I read from an XML file:
double x;
BSTR name;
MSXML::IXMLDOMNodeListPtr theList;
MSXML::IXMLDOMNodePtr theItem;
//Some XML API here...
theItem = theList->Getitem(0);
theItem->get_text(&name);
x = wcstod(name,NULL);
the problem is that this function returns NULL upon failure, but sometimes I do want to read and convert the valid string L"0".
Is there a workaround for this?
You can use std::stod which will throw exception if the function fails.
Make sure BSTR is initialized to NULL. Add error check for Getitem and get_text
#include <string>
BSTR name = nullptr;
...
double x = 0;
if(name)
{
try
{
x = std::stod(name);
}
catch(...)
{
//error ...
}
}
I am porting the openvr sample to jogl, after we created the binding with jna.
Almost at the end (before rendering the controllers and the tracking base stations), I got stuck trying to translate a char pointer in C to a String in Java.
C++ code here:
//-----------------------------------------------------------------------------
// Purpose: Helper to get a string from a tracked device property and turn it
// into a std::string
//-----------------------------------------------------------------------------
std::string GetTrackedDeviceString( vr::IVRSystem *pHmd, vr::TrackedDeviceIndex_t unDevice, vr::TrackedDeviceProperty prop, vr::TrackedPropertyError *peError = NULL )
{
uint32_t unRequiredBufferLen = pHmd->GetStringTrackedDeviceProperty( unDevice, prop, NULL, 0, peError );
if( unRequiredBufferLen == 0 )
return "";
char *pchBuffer = new char[ unRequiredBufferLen ];
unRequiredBufferLen = pHmd->GetStringTrackedDeviceProperty( unDevice, prop, pchBuffer, unRequiredBufferLen, peError );
std::string sResult = pchBuffer;
delete [] pchBuffer;
return sResult;
}
GetStringTrackedDeviceProperty here:
/** Returns a string property. If the device index is not valid or the property is not a string type this function will
* return 0. Otherwise it returns the length of the number of bytes necessary to hold this string including the trailing
* null. Strings will generally fit in buffers of k_unTrackingStringSize characters. */
virtual uint32_t GetStringTrackedDeviceProperty( vr::TrackedDeviceIndex_t unDeviceIndex, ETrackedDeviceProperty prop, VR_OUT_STRING() char *pchValue, uint32_t unBufferSize, ETrackedPropertyError *pError = 0L ) = 0;
Where VR_OUT_STRING() is defined here as:
# define VR_CLANG_ATTR(ATTR)
#define VR_OUT_STRING() VR_CLANG_ATTR( "out_string: ;" )
I have already done something similar where I had to call a function that expect the pointer to an array of TrackedDevicePose_t structures:
private TrackedDevicePose_t.ByReference trackedDevicePosesReference = new TrackedDevicePose_t.ByReference();
public TrackedDevicePose_t[] trackedDevicePose
= (TrackedDevicePose_t[]) trackedDevicePosesReference.toArray(VR.k_unMaxTrackedDeviceCount);
I created first the reference and then from it the actual array.
But here I can't have a class extending the char array..
private String getTrackedDeviceString(IVRSystem hmd, int device, int prop, IntBuffer propError) {
int requiredBufferLen = hmd.GetStringTrackedDeviceProperty.apply(device, prop, Pointer.NULL, 0, propError);
if(requiredBufferLen == 0) {
return "";
}
CharArray.ByReference charArrayReference = new CharArray.ByReference();
char[] cs = charArrayReference.toArray(requiredBufferLen);
return null;
}
Where apply (here) is:
public interface GetStringTrackedDeviceProperty_callback extends Callback {
int apply(int unDeviceIndex, int prop, Pointer pchValue, int unBufferSize, IntBuffer pError);
};
CharArray class, crap attempt here
Any ideas?
I've done some porting of C and C++ code to Java, and while it's probably horribly hacky, the best I've come up with to solve cases where a pointer to an int primitive or a char*/String is needed for a function call, is to create a small wrapper class with a single property, pass that object into the function, change the property as needed, and retrieve the new value after the function call. So something like:
public class StringPointer {
public String value = "";
}
StringPointer pchBuffer = new StringPointer();
unRequiredBufferLen = pHmd.GetStringTrackedDeviceProperty( unDevice, prop, pchBuffer, unRequiredBufferLen, peError );
String sResult = pchBuffer.value;
and inside GetStringTrackedDeviceProperty()
...
pchValue.value = "some string";
...
In this case, you can use a String, since that's what your code is doing with the char* after the function call, but if it actually really needs to be a char[], you can just create char[] pchBuffer = new char[unRequiredBufferLen]; and pass that into the function. It will be just like you were using a char* in C++, and any changes you make inside the array will be visible after the function ends, and you can even do String sResult = new String(pchBuffer);.
My question is nearly identical to this question, except that the linked question deals with char*, whereas I'm using std::string in my code. Like the linked question, I'm also using C# as my target language.
I have a class written in C++:
class MyClass
{
public:
const std::string get_value() const; // returns utf8-string
void set_value(const std::string &value); // sets utf8-string
private:
// ...
};
And this get's wrapped by SWIG in C# as follows:
public class MyClass
{
public string get_value();
public void set_value(string value);
}
SWIG does everything for me, except that it doesn't make an utf8 to utf16 string conversion during the calls to MyClass. My strings come through fine if they are representable in ASCII, but if I try passing a string with non-ascii characters in a round-trip through "set_value" and "get_value", I end up with unintelligible characters.
How can I make SWIG wrap UTF-8 encoded C++ strings in C#? n.b. I'm using std::string, not std::wstring, and not char*.
There's a partial solution on the SWIG sourceforge site, but it deals with char* not std::string, and it uses a (configurable) fixed length buffer.
With the help (read: genius!) of David Jeske in the linked Code Project article, I have finally been able to answer this question.
You'll need this class (from David Jeske's code) in your C# library.
public class UTF8Marshaler : ICustomMarshaler {
static UTF8Marshaler static_instance;
public IntPtr MarshalManagedToNative(object managedObj) {
if (managedObj == null)
return IntPtr.Zero;
if (!(managedObj is string))
throw new MarshalDirectiveException(
"UTF8Marshaler must be used on a string.");
// not null terminated
byte[] strbuf = Encoding.UTF8.GetBytes((string)managedObj);
IntPtr buffer = Marshal.AllocHGlobal(strbuf.Length + 1);
Marshal.Copy(strbuf, 0, buffer, strbuf.Length);
// write the terminating null
Marshal.WriteByte(buffer + strbuf.Length, 0);
return buffer;
}
public unsafe object MarshalNativeToManaged(IntPtr pNativeData) {
byte* walk = (byte*)pNativeData;
// find the end of the string
while (*walk != 0) {
walk++;
}
int length = (int)(walk - (byte*)pNativeData);
// should not be null terminated
byte[] strbuf = new byte[length];
// skip the trailing null
Marshal.Copy((IntPtr)pNativeData, strbuf, 0, length);
string data = Encoding.UTF8.GetString(strbuf);
return data;
}
public void CleanUpNativeData(IntPtr pNativeData) {
Marshal.FreeHGlobal(pNativeData);
}
public void CleanUpManagedData(object managedObj) {
}
public int GetNativeDataSize() {
return -1;
}
public static ICustomMarshaler GetInstance(string cookie) {
if (static_instance == null) {
return static_instance = new UTF8Marshaler();
}
return static_instance;
}
}
Then, in Swig's "std_string.i", on line 24 replace this line:
%typemap(imtype) string "string"
with this line:
%typemap(imtype, inattributes="[MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(UTF8Marshaler))]", outattributes="[return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(UTF8Marshaler))]") string "string"
and on line 61, replace this line:
%typemap(imtype) const string & "string"
with this line:
%typemap(imtype, inattributes="[MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(UTF8Marshaler))]", outattributes="[return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(UTF8Marshaler))]") string & "string"
Lo and behold, everything works. Read the linked article for a good understanding of how this works.
I've worked myself through the rapidXML sources and managed to read some values. Now I want to change them and save them to my XML file:
Parsing file and set a pointer
void SettingsHandler::getConfigFile() {
pcSourceConfig = parsing->readFileInChar(CONF);
cfg.parse<0>(pcSourceConfig);
}
Reading values from XML
void SettingsHandler::getDefinitions() {
SettingsHandler::getConfigFile();
stGeneral = cfg.first_node("settings")->value();
/* stGeneral = 60 */
}
Changing values and saving to file
void SettingsHandler::setDefinitions() {
SettingsHandler::getConfigFile();
stGeneral = "10";
cfg.first_node("settings")->value(stGeneral.c_str());
std::stringstream sStream;
sStream << *cfg.first_node();
std::ofstream ofFileToWrite;
ofFileToWrite.open(CONF, std::ios::trunc);
ofFileToWrite << "<?xml version=\"1.0\"?>\n" << sStream.str() << '\0';
ofFileToWrite.close();
}
Reading file into buffer
char* Parser::readFileInChar(const char* p_pccFile) {
char* cpBuffer;
size_t sSize;
std::ifstream ifFileToRead;
ifFileToRead.open(p_pccFile, std::ios::binary);
sSize = Parser::getFileLength(&ifFileToRead);
cpBuffer = new char[sSize];
ifFileToRead.read( cpBuffer, sSize);
ifFileToRead.close();
return cpBuffer;
}
However, it's not possible to save the new value. My code is just saving the original file with a value of "60" where it should be "10".
Rgds
Layne
I think this is a RapidXML Gotcha
Try adding the parse_no_data_nodes flag to cfg.parse<0>(pcSourceConfig)
You should definitely be testing that the output file opened correctly and that your write succeeded. At the simplest, you need something like:
if ( ! ofFileToWrite << "<?xml version=\"1.0\"?>\n"
<< sStream.str() << '\0' ) {
throw "write failed";
}
Note that you don't need the '\0' terminator, but it shouldn't do any harm.
Use the following method to add an attribute to a node. The method uses the allocation of memory for strings from rapidxml. So rapidxml takes care of the strings as long as the document is alive. See http://rapidxml.sourceforge.net/manual.html#namespacerapidxml_1modifying_dom_tree for further information.
void setStringAttribute(
xml_document<>& doc, xml_node<>* node,
const string& attributeName, const string& attributeValue)
{
// allocate memory assigned to document for attribute value
char* rapidAttributeValue = doc.allocate_string(attributeValue.c_str());
// search for the attribute at the given node
xml_attribute<>* attr = node->first_attribute(attributeName.c_str());
if (attr != 0) { // attribute already exists
// only change value of existing attribute
attr->value(rapidAttributeValue);
} else { // attribute does not exist
// allocate memory assigned to document for attribute name
char* rapidAttributeName = doc.allocate_string(attributeName.c_str());
// create new a new attribute with the given name and value
attr = doc.allocate_attribute(rapidAttributeName, rapidAttributeValue);
// append attribute to node
node->append_attribute(attr);
}
}