Replace all occurrences of a string in given char/byte array in C#

Question

I come from C++ background and was wondering whether in C# exist any magic that would let me to do the following:

char[] buf = new char[128*1024*1024];
// filling the arr
buf = buf.ToString().Replace(oldstring, newstring).ToArray();

Is there a chance to do it fast (not write all things by hand) and efficient (have one copy of buffer)?

score 1 · Answer 1 · answered Aug 05 '11 at 08:28

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Not very clear what is really your char array is in code provided, but... Use String[] ctor overload to construct the string from your char array, and after call replace with desired parameters.

answered Aug 05 '11 at 08:28

Tigran

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it's used as (binary / text) file buffer. Suppose you got a really big file, get a piece of it and process the data in a iterative manner. btw calling `string strbuf = new string(buf)` will allocate more memory, it this true? – rjeczalik Aug 05 '11 at 08:38
Yes, strings are immutable in C#, so it will allocate a new block of memory. – Tigran Aug 05 '11 at 08:44

score 1 · Answer 2 · edited May 23 '17 at 12:11

1

Since strings are immutable in .NET, the most memory efficient way of manipulating them is by using the StringBuilder class, which internally treats them as mutable.

Here's an example:

var buffer = new StringBuilder(128*1024*1024);

// Fill the buffer using the 'StringBuilder.Append' method.
// Examples:
// buffer.Append('E');
// buffer.Append("foo");
// buffer.Append(new char[] { 'A', 'w', 'e', 's', 'o', 'm', 'e' });
// Alternatively you can access the elements of the underlying char array directly
// through 'StringBuilder.Chars' indexer.
// Example:
// buffer.Chars[9] = 'E';

buffer = buffer.Replace(oldstring, newstring);

edited May 23 '17 at 12:11

Community

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answered Aug 05 '11 at 08:28

Enrico Campidoglio

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ToString() generates a copy. So: no. – Hans Passant Aug 05 '11 at 10:28
@Hans Passant Mine was just an example. The `StringBuilder` class treats strings as mutable, so the manipulation itself is memory efficient. – Enrico Campidoglio Aug 05 '11 at 10:40

score 1 · Answer 3 · answered Aug 05 '11 at 08:37

If you need to stay with the array (and cannot use something else to start with, e.g. as others suggested a StringBuilder), then no. There is no built in, "zero-copy", way to "replace a (sub-)char-array with another (sub-)char-array in a given char-array".

Replace all occurrences of a string in given char/byte array in C#

3 Answers3