StringBuilder

A growable buffer for building strings efficiently.

Module: Std

Struct

struct StringBuilder {
    data:     *char8;
    length:   uint;
    capacity: uint;
}

A StringBuilder accumulates bytes in a buffer that grows as needed, avoiding the repeated allocations you'd get from concatenating String values in a loop. When the content is complete, convert it to a String with ToString (copy) or IntoString (hand over the buffer).

The buffer grows geometrically: when more room is needed, capacity starts at 16 and doubles until it fits, so appending N bytes costs amortized O(N).

Methods

Construction

Method	Description
New	Creates an empty builder.
WithCapacity	Creates a builder with space pre-allocated.

Capacity

Method	Description
Capacity	Current allocated capacity in bytes.
Reserve	Ensure room for additional bytes.
Shrink	Release unused capacity.

Appending

Method	Description
Append	Append a char8, slice, or String.

Conversion

Method	Description
ToString	Copy the contents into a new String.
IntoString	Consume the builder, transferring its buffer.

Inspection

Method	Description
Length	Number of bytes written so far.
IsEmpty	Whether nothing has been written.
Clear	Reset the length to zero, keep capacity.

Example

import Std::Io::*;
import Std::StringBuilder;

func Main() -> int {
    var sb = StringBuilder::New();
    sb.Append("Hello");
    sb.Append(c8',');
    sb.Append(" world");

    let greeting = sb.IntoString();
    PrintLine(greeting);            // Hello, world
    return 0;
}