symbian 描述符 TBuf和const char*的转换

 

Buf和const char*的转换

http://wiki.forum.nokia.com/index.php/How_to_Convert_TBuf_to_Char_and_Vice_Versa

How to Convert TBuf to Char and Vice Versa
From Forum Nokia Wiki

void stringToDescriptor(const char* aString, TDes& aDescriptor)
{
    TPtrC8 ptr(reinterpret_cast<const TUint8*>(aString));
    aDescriptor.Copy(ptr);
}

Usage:

const char* str = "Hello, world!";
    TBuf<32> buffer;  // Make it large enough for str
    stringToDescriptor(str, buffer);

Problem with the code above is that defining a TBuf not large enough will raise a USER 23 panic.

Some ways to avoid this include:

Using either __ASSERT_DEBUG or __ASSERT_ALWAYS, depending on your needs. Note that you can use alternatives to User::Panic(), as long as you avoid executing sensitive code.

void stringToDescriptor(const char* aString, TDes& aDescriptor)
{
    TPtrC8 ptr(reinterpret_cast<const TUint8*>(aString));
    _LIT(KMyPanicDescriptor, "My panic text");
    __ASSERT_ALWAYS(User::StringLength(reinterpret_cast<const TUint8*>(aString))
 <= aDescriptor.MaxLength(), User::Panic(KMyPanicDescriptor, 0));
    aDescriptor.Copy(ptr);
}

The other way is relying on a dynamic buffer, using HBufC for instance:

HBufC* stringToDescriptorL(const char* aString)
{
    TPtrC8 ptr(reinterpret_cast<const TUint8*>(aString));
    HBufC* buffer = HBufC::NewL(ptr.Length());
    buffer->Des().Copy(ptr);
 
    return buffer;
}

Note that the caller is responsible of freeing the HBufC returned. Also note the trailing "L" in the function's name.

Depending on your code, you may prefere one of these over the others. Also, you may need to add extra checks (for instance, checking whether the char pointer is null or not).

Converting descriptors to C-strings may be done this way:

const char* descriptorToStringL(const TDesC& aDescriptor)
{
    TInt length = aDescriptor.Length();
 
    HBufC8* buffer = HBufC8::NewLC(length);
    buffer->Des().Copy(aDescriptor);
 
    char* str = new(ELeave) char[length + 1];
    Mem::Copy(str, buffer->Ptr(), length);
    str[length] = '/0';
 
    CleanupStack::PopAndDestroy(buffer);
 
    return str;
}