Process XML events

std.xml reads one bounded event at a time from a byte stream. Event text has already been checked as UTF-8 and entity references have been decoded. Match the events your application needs, and keep reading through Eof to check the complete document:

import std.bytes
import std.io
import std.xml
from std.xml import Event

def main() -> Result[(), AllocError | IoError | std.bytes.BytesError | std.xml.XmlError]:
    source = "<items><item>Tea &amp; cake</item><item>Milk</item></items>"
    mut input = std.xml.reader(std.io.cursor(std.bytes.from_text(source)?), &std.xml.limits())?
    mut output = std.xml.writer(std.io.cursor(std.bytes.empty()?), &std.xml.limits())?
    mut done = False
    while not done:
        event = input.next()?
        match &event:
            case Event.Text(text):
                print(*text)?
            case Event.Eof:
                done = True
            case _:
                pass
        output.write(&event)?
    print(output.inner.data.to_text()?)?
    Ok(())

Tea & cake
Milk
<items><item>Tea &amp; cake</item><item>Milk</item></items>

The writer escapes values and checks the element structure. Passing Eof checks that the root has closed and flushes its stream. When constructing events yourself, call finish() after the final element. Events own their strings, so retaining an event also retains its memory.

Choose limits for the input you accept. max_token bounds a complete tag, comment, or text run; max_depth bounds nesting. The reference describes all limits and errors. This example lets errors propagate so malformed input and stream failures remain visible. A failed file writer may have emitted partial output; applications that need replacement only on success should manage a temporary destination.

This reader accepts UTF-8 XML 1.0 without a DTD. It never loads external entities. Namespace prefixes remain literal names, so applications needing namespace URI resolution must supply that policy themselves.