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UTF-8-encoded, preceded by varint-encoded integer length of string in bytes Repeated value with the same tag or, for varint-encoded integers only, values packed contiguously and prefixed by tag and total byte length
MessagePack is more compact than JSON, but imposes limitations on array and integer sizes.On the other hand, it allows binary data and non-UTF-8 encoded strings. In JSON, map keys have to be strings, but in MessagePack there is no such limitation and any type can be a map key, including types like maps and arrays, and, like YAML, numbers.
A tag of 2 indicates that the following byte string encodes an unsigned bignum. A tag of 32 indicates that the following text string is a URI as defined in RFC 3986. RFC 8746 defines tags 64–87 to encode homogeneous arrays of fixed-size integer or floating-point values as byte strings. The tag 55799 is allocated to mean "CBOR data follows".
The length is the number of bytes in the string, encoded in base 10. A colon (:) separates the length and the contents. The contents are the exact number of bytes specified by the length. Examples: An empty string is encoded as 0:. The string "bencode" is encoded as 6:bencode. Lists are encoded as l<elements>e. Begins with l and ends with e.
Only a small subset of possible byte strings are error-free UTF-8: several bytes cannot appear; a byte with the high bit set cannot be alone; and in a truly random string a byte with a high bit set has only a 1 ⁄ 15 chance of starting a valid UTF-8 character. This has the (possibly unintended) consequence of making it easy to detect if a ...
A "character" in the algorithm can be a byte, or a bit, or any other convenient size. One may also make the observation that mathematically, the encoded string can be computed as a simple modification of the suffix array, and suffix arrays can be computed with linear time and memory. The BWT can be defined with regards to the suffix array SA of ...
UTF-8 shares these advantages, but many earlier multi-byte encoding schemes (such as Shift JIS and other Asian multi-byte encodings) did not allow unambiguous searching and could only be synchronized by re-parsing from the start of the string. UTF-16 is not self-synchronizing if one byte is lost or if traversal starts at a random byte.
Because of the appended zero byte, this is always possible. Encode each group by deleting the trailing zero byte (if any) and prepending the number of non-zero bytes, plus one. Thus, each encoded group is the same size as the original, except that 254 non-zero bytes are encoded into 255 bytes by prepending a byte of 255.