# Package org.apache.tomcat.util.buf

## Buffers and Encodings

This package contains buffers and utils to perform encoding/decoding of buffers. That includes byte to char conversions, URL encodings, etc.

Encoding is a critical operation for performance. There are few tricks in this package - the C2B and B2C converters are caching an ISReader/OSWriter and keep everything allocated to do the conversions in any VM without any garbage.

This package must accommodate future extensions and additional converters ( most important: the nio.charset, which should be detected and used if available ). Also, we do have one hand-written UTF8Decoder, and other tuned encoders could be added.

My benchmarks ( I'm costin :-) show only small differences between C2B, B2C and hand-written codders/decoders, so UTF8Decoder may be disabled.

Interface Summary
ByteChunk.ByteInputChannel: Input interface, used when the buffer is empty.
ByteChunk.ByteOutputChannel: When we need more space we'll either grow the buffer ( up to the limit ) or send it to a channel.
CharChunk.CharInputChannel: Input interface, used when the buffer is empty.
CharChunk.CharOutputChannel: When we need more space we'll either grow the buffer ( up to the limit ) or send it to a channel.

Class Summary
AbstractChunk: Base class for the *Chunk implementation to reduce duplication.
Ascii: This class implements some basic ASCII character handling functions.
Asn1Parser: This is a very basic ASN.1 parser that provides the limited functionality required by Tomcat.
Asn1Writer
B2CConverter: NIO based character decoder.
ByteBufferHolder: Simple wrapper for a `ByteBuffer` that remembers if the buffer has been flipped or not.
ByteBufferUtils
ByteChunk: This class is used to represent a chunk of bytes, and utilities to manipulate byte[].
C2BConverter: NIO based character encoder.
CharChunk: Utilities to manipulate char chunks.
CharsetCache
CharsetUtil
HexUtils: Tables useful when converting byte arrays to and from strings of hexadecimal digits.
MessageBytes: This class is used to represent a subarray of bytes in an HTTP message.
StringCache: This class implements a String cache for ByteChunk and CharChunk.
StringUtils: Utility methods to build a separated list from a given set (not java.util.Set) of inputs and return that list as a string or append it to an existing StringBuilder.
UDecoder: All URL decoding happens here.
UEncoder: Efficient implementation of a UTF-8 encoder.
UriUtil: Utility class for working with URIs and URLs.
Utf8Encoder: Encodes characters as bytes using UTF-8.

Enum Summary
EncodedSolidusHandling
UEncoder.SafeCharsSet

Exception Summary
ByteChunk.BufferOverflowException