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package moe.anita.mai.buffer;
import java.nio.charset.StandardCharsets;
import java.util.Objects;
/**
* An in-memory UTF-8 source buffer.
*
* Offsets and lengths are measured in UTF-8 bytes.
*/
public final class MemBuf implements Buffer {
private final byte[] data;
public MemBuf(String source) {
Objects.requireNonNull(source);
data = source.getBytes(StandardCharsets.UTF_8);
}
@Override
public int length() {
return data.length;
}
@Override
public int get(int offset) {
int first = Byte.toUnsignedInt(data[offset]);
if ((first & 0x80) == 0) {
return first;
}
if ((first & 0xE0) == 0xC0) {
return ((first & 0x1F) << 6) | (Byte.toUnsignedInt(data[offset + 1]) & 0x3F);
}
if ((first & 0xF0) == 0xE0) {
return ((first & 0x0F) << 12)
| ((Byte.toUnsignedInt(data[offset + 1]) & 0x3F) << 6)
| (Byte.toUnsignedInt(data[offset + 2]) & 0x3F);
}
return ((first & 0x07) << 18)
| ((Byte.toUnsignedInt(data[offset + 1]) & 0x3F) << 12)
| ((Byte.toUnsignedInt(data[offset + 2]) & 0x3F) << 6)
| (Byte.toUnsignedInt(data[offset + 3]) & 0x3F);
}
@Override
public int width(int offset) {
int first = Byte.toUnsignedInt(data[offset]);
if ((first & 0x80) == 0) {
return 1;
}
if ((first & 0xE0) == 0xC0) {
return 2;
}
if ((first & 0xF0) == 0xE0) {
return 3;
}
return 4;
}
@Override
public CharSequence slice(int start, int end) {
return new String(data, start, end - start, StandardCharsets.UTF_8);
}
}
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