--- CBOR-XS/README 2013/11/30 18:42:27 1.11 +++ CBOR-XS/README 2014/10/25 06:36:34 1.14 @@ -180,8 +180,13 @@ If $enable is false (the default), then "decode" will throw an error when it encounters a self-referential/cyclic data structure. + FUTURE DIRECTION: the motivation behind this option is to avoid + *real* cycles - future versions of this module might chose to decode + cyclic data structures using weak references when this option is + off, instead of throwing an error. + This option does not affect "encode" in any way - shared values and - references will always be decoded properly if present. + references will always be encoded properly if present. $cbor = $cbor->pack_strings ([$enable]) $enabled = $cbor->get_pack_strings @@ -202,6 +207,29 @@ This option does not affect "decode" in any way - string references will always be decoded properly if present. + $cbor = $cbor->validate_utf8 ([$enable]) + $enabled = $cbor->get_validate_utf8 + If $enable is true (or missing), then "decode" will validate that + elements (text strings) containing UTF-8 data in fact contain valid + UTF-8 data (instead of blindly accepting it). This validation + obviously takes extra time during decoding. + + The concept of "valid UTF-8" used is perl's concept, which is a + superset of the official UTF-8. + + If $enable is false (the default), then "decode" will blindly accept + UTF-8 data, marking them as valid UTF-8 in the resulting data + structure regardless of whether thats true or not. + + Perl isn't too happy about corrupted UTF-8 in strings, but should + generally not crash or do similarly evil things. Extensions might be + not so forgiving, so it's recommended to turn on this setting if you + receive untrusted CBOR. + + This option does not affect "encode" in any way - strings that are + supposedly valid UTF-8 will simply be dumped into the resulting CBOR + string without checking whether that is, in fact, true or not. + $cbor = $cbor->filter ([$cb->($tag, $value)]) $cb_or_undef = $cbor->get_filter Sets or replaces the tagged value decoding filter (when $cb is @@ -266,6 +294,64 @@ CBOR::XS->new->decode_prefix ("......") => ("...", 3) + INCREMENTAL PARSING + In some cases, there is the need for incremental parsing of JSON texts. + While this module always has to keep both CBOR text and resulting Perl + data structure in memory at one time, it does allow you to parse a CBOR + stream incrementally, using a similar to using "decode_prefix" to see if + a full CBOR object is available, but is much more efficient. + + It basically works by parsing as much of a CBOR string as possible - if + the CBOR data is not complete yet, the pasrer will remember where it + was, to be able to restart when more data has been accumulated. Once + enough data is available to either decode a complete CBOR value or raise + an error, a real decode will be attempted. + + A typical use case would be a network protocol that consists of sending + and receiving CBOR-encoded messages. The solution that works with CBOR + and about anything else is by prepending a length to every CBOR value, + so the receiver knows how many octets to read. More compact (and + slightly slower) would be to just send CBOR values back-to-back, as + "CBOR::XS" knows where a CBOR value ends, and doesn't need an explicit + length. + + The following methods help with this: + + @decoded = $cbor->incr_parse ($buffer) + This method attempts to decode exactly one CBOR value from the + beginning of the given $buffer. The value is removed from the + $buffer on success. When $buffer doesn't contain a complete value + yet, it returns nothing. Finally, when the $buffer doesn't start + with something that could ever be a valid CBOR value, it raises an + exception, just as "decode" would. In the latter case the decoder + state is undefined and must be reset before being able to parse + further. + + This method modifies the $buffer in place. When no CBOR value can be + decoded, the decoder stores the current string offset. On the next + call, continues decoding at the place where it stopped before. For + this to make sense, the $buffer must begin with the same octets as + on previous unsuccessful calls. + + You can call this method in scalar context, in which case it either + returns a decoded value or "undef". This makes it impossible to + distinguish between CBOR null values (which decode to "undef") and + an unsuccessful decode, which is often acceptable. + + @decoded = $cbor->incr_parse_multiple ($buffer) + Same as "incr_parse", but attempts to decode as many CBOR values as + possible in one go, instead of at most one. Calls to "incr_parse" + and "incr_parse_multiple" can be interleaved. + + $cbor->incr_reset + Resets the incremental decoder. This throws away any saved state, so + that subsequent calls to "incr_parse" or "incr_parse_multiple" start + to parse a new CBOR value from the beginning of the $buffer again. + + This method can be caled at any time, but it *must* be called if you + want to change your $buffer or there was a decoding error and you + want to reuse the $cbor object for future incremental parsings. + MAPPING This section describes how CBOR::XS maps Perl values to CBOR values and vice versa. These mappings are designed to "do the right thing" in most @@ -656,6 +742,16 @@ to provide these modules. The decoding usually fails with an exception if the required module cannot be loaded. + 0, 1 (date/time string, seconds since the epoch) + These tags are decoded into Time::Piece objects. The corresponding + "Time::Piece::TO_CBOR" method always encodes into tag 1 values + currently. + + The Time::Piece API is generally surprisingly bad, and fractional + seconds are only accidentally kept intact, so watch out. On the plus + side, the module comes with perl since 5.10, which has to count for + something. + 2, 3 (positive/negative bignum) These tags are decoded into Math::BigInt objects. The corresponding "Math::BigInt::TO_CBOR" method encodes "small" bigints into normal