CODEWITHSUNDEEP
c#stringcstring
y2k
y2k

Reputation: 66006

Help with \0 terminated strings in C#

I'm using a low level native API where I send an unsafe byte buffer pointer to get a c-string value.

So it gives me 

// using byte[255] c_str
string s = new string(Encoding.ASCII.GetChars(c_str));

// now s == "heresastring\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0(etc)";

So obviously I'm not doing it right, how I get rid of the excess?

Upvotes: 24

Views: 45598

Answers (7)

Moss
Moss

Reputation: 905

From .NET Core 2.1 onward, the following can be use which will help prevent unnecessary allocations for intermediate arrays or strings:

var bytesAsSpan = bytes.AsSpan();
var terminatorIndex = bytesAsSpan.IndexOf(byte.MinValue);
var s = Encoding.ASCII.GetString(bytesAsSpan.Slice(0, terminatorIndex));

It's really the last line that requires .NET Core 2.1 or later because that's when the Encoding.GetString(ReadOnlySpan<byte>) overload was introduced. It's possible to do Span based operations using the System.Memory package but Encoding.GetString won't expose an overload that accepts ReadOnlySpan<byte>, so the last line would have to allocate an array:

var s = Encoding.ASCII.GetString(bytesAsSpan.Slice(0, terminatorIndex).ToArray());

Upvotes: 4

teodoric8 .
teodoric8 .

Reputation: 29

The safest way is to use:

s = s.Replace("\0", "");

Upvotes: 1

OldFart
OldFart

Reputation: 2479

How about one of the System.Runtime.InteropServices.Marshall.PtrToString* methods?

Marshal.PtrToStringAnsi - Copies all characters up to the first null character from an unmanaged ANSI string to a managed String, and widens each ANSI character to Unicode.

Marshal.PtrToStringUni - Allocates a managed String and copies all or part to the first null of an unmanaged Unicode string into it.

Upvotes: 3

John Fisher
John Fisher

Reputation: 22719

.NET strings are not null-terminated (as you may have guessed from this). So, you can treat the '\0' as you would treat any normal character. Normal string manipulation will fix things for you. Here are some (but not all) options.

s = s.Trim('\0');

s = s.Replace("\0", "");

var strings =  s.Split(new char[] {'\0'}, StringSplitOptions.RemoveEmptyEntries);

If you definitely want to throw away any values after the first null character, this might work better for you. But be careful, it only works on strings that actually include the null character.

s = s.Substring(0, Math.Max(0, s.IndexOf('\0')));

Upvotes: 44

MrHIDEn
MrHIDEn

Reputation: 1879

// s == "heresastring\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0(etc)"    
s = s.Split(new[] { '\0' }, 2)[0];
// s == "heresastring"

Upvotes: 5

Jason Williams
Jason Williams

Reputation: 57902

There may be an option to strip NULs in the conversion.

Beyond that, you could probably clean it up with:

s = s.Trim('\0');

...or, if you think there may be non-NUL characters after some NULs, this may be safer:

int pos = s.IndexOf('\0');  
if (pos >= 0)
    s = s.Substring(0, pos);

Upvotes: 6

Jason M
Jason M

Reputation: 512

I believe \0 is "null" in ascii -- are you sure the string you're getting is actually ascii encoded?

Upvotes: 0

Related Questions