--- CBOR-XS/XS.pm 2013/12/01 16:40:25 1.35 +++ CBOR-XS/XS.pm 2014/01/05 14:24:54 1.40 @@ -66,7 +66,7 @@ use common::sense; -our $VERSION = 1.11; +our $VERSION = 1.25; our @ISA = qw(Exporter); our @EXPORT = qw(encode_cbor decode_cbor); @@ -335,6 +335,70 @@ =back +=head2 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 C knows where +a CBOR value ends, and doesn't need an explicit length. + +The following methods help with this: + +=over 4 + +=item @decoded = $cbor->incr_parse ($buffer) + +This method attempts to decode exactly one CBOR value from the beginning +of the given C<$buffer>. The value is removed from the C<$buffer> on +success. When C<$buffer> doesn't contain a complete value yet, it returns +nothing. Finally, when the C<$buffer> doesn't start with something +that could ever be a valid CBOR value, it raises an exception, just as +C would. In the latter case the decoder state is undefined and +must be reset before being able to parse further. + +This method modifies the C<$buffer> in place. When no CBOR value can be +decoded, the decoder stores the current string offset. On the next call, +continues decoding at the place where it stopped before. For this to make +sense, the C<$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 C. This makes it impossible to +distinguish between CBOR null values (which decode to C) and an +unsuccessful decode, which is often acceptable. + +=item @decoded = $cbor->incr_parse_multiple ($buffer) + +Same as C, but attempts to decode as many CBOR values as +possible in one go, instead of at most one. Calls to C and +C can be interleaved. + +=item $cbor->incr_reset + +Resets the incremental decoder. This throws away any saved state, so that +subsequent calls to C or C start to parse +a new CBOR value from the beginning of the C<$buffer> again. + +This method can be caled at any time, but it I be called if you want +to change your C<$buffer> or there was a decoding error and you want to +reuse the C<$cbor> object for future incremental parsings. + +=back + =head1 MAPPING @@ -989,18 +1053,20 @@ # from FreeBSD, which can't parse ISO 8601, RFC3339, RFC4287 or much of anything # else either. Whats incredibe over standard strptime totally escapes me. # doesn't do fractional times, either. sigh. + # In fact, it's all a lie, it uses whatever strptime it wants, and of course, + # they are all incomptible. The openbsd one simply ignores %z (but according to the + # docs, it would be much more incredibly flexible indeed. If it worked, that is.). scalar eval { my $s = $_[1]; $s =~ s/Z$/+00:00/; - $s =~ s/(\.[0-9]+)?([+-][0-9][0-9]):([0-9][0-9])/$2$3/ + $s =~ s/(\.[0-9]+)?([+-][0-9][0-9]):([0-9][0-9])$// or die; - my $f = $1; # fractional part. hopefully - - my $d = Time::Piece->strptime ($s, "%Y-%m-%dT%H:%M:%S%z"); + my $b = $1 - ($2 * 60 + $3) * 60; # fractional part + offset. hopefully + my $d = Time::Piece->strptime ($s, "%Y-%m-%dT%H:%M:%S"); - Time::Piece::gmtime ($d->epoch + $f) + Time::Piece::gmtime ($d->epoch + $b) } || die "corrupted CBOR date/time string ($_[0])"; }, @@ -1072,7 +1138,7 @@ } sub Time::Piece::TO_CBOR { - tag 1, $_[0]->epoch + tag 1, 0 + $_[0]->epoch } XSLoader::load "CBOR::XS", $VERSION;