In the following documentation, spec refers to a data layout
bindat-raw to a byte array, and struct to an
alist representing unpacked field data.
bindat-unpackspec bindat-raw &optional bindat-idx
This function unpacks data from the unibyte string or byte
according to spec. Normally, this starts unpacking at the
beginning of the byte array, but if bindat-idx is non-
specifies a zero-based starting position to use instead.
The value is an alist or nested alist in which each element describes one unpacked field.
bindat-get-fieldstruct &rest name
This function selects a field’s data from the nested alist
struct. Usually struct was returned by
bindat-unpack. If name corresponds to just one argument,
that means to extract a top-level field value. Multiple name
arguments specify repeated lookup of sub-structures. An integer name
acts as an array index.
For example, if name is
(a b 2 c), that means to find
c in the third element of subfield
b of field
a. (This corresponds to
struct.a.b.c in C.)
Although packing and unpacking operations change the organization of data (in memory), they preserve the data’s total length, which is the sum of all the fields’ lengths, in bytes. This value is not generally inherent in either the specification or alist alone; instead, both pieces of information contribute to its calculation. Likewise, the length of a string or array being unpacked may be longer than the data’s total length as described by the specification.
This function returns the total length of the data in struct, according to spec.
bindat-packspec struct &optional bindat-raw bindat-idx
This function returns a byte array packed according to spec from
the data in the alist struct. It normally creates and fills a
new byte array starting at the beginning. However, if bindat-raw
nil, it specifies a pre-allocated unibyte string or vector to
pack into. If bindat-idx is non-
nil, it specifies the starting
offset for packing into
When pre-allocating, you should make sure
meets or exceeds the total length to avoid an out-of-range error.
Convert the Internet address vector ip to a string in the usual dotted notation.
(bindat-ip-to-string [127 0 0 1]) ⇒ "127.0.0.1"