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struct

This moddule provides functions for converting between Blade values and C structs and vice-versa in the binary format.

Functions

pack(format, ...)

Packs the given arguments into a bytes object according to the specified format. This function behaves the same as the pack function from Perl and PHP (more similar to the PHP version) and uses the same formatting rules as the PHP version.

  • The format string consists of format codes followed by an optional repeater argument. The repeater argument can be either an integer value or * for repeating to the end of the input data. For a, A, h, H the repeat count specifies how many characters of one data argument are taken, for @ it is the absolute position where to put the next data, for everything else the repeat count specifies how many data arguments are consumed and packed into the resulting binary string.

  • The accepted characters in the format string are as defined below:

Code Description
a NUL-padded string
A SPACE-padded string
h Hex string, low nibble first
H Hex string, high nibble first
c signed char
C unsigned char
s signed short (always 16 bit, machine byte order)
S unsigned short (always 16 bit, machine byte order)
n unsigned short (always 16 bit, big endian byte order)
v unsigned short (always 16 bit, little endian byte order)
i signed integer (machine dependent size and byte order)
I unsigned integer (machine dependent size and byte order)
l signed long (always 32 bit, machine byte order)
L unsigned long (always 32 bit, machine byte order)
N unsigned long (always 32 bit, big endian byte order)
V unsigned long (always 32 bit, little endian byte order)
q signed long long (always 64 bit, machine byte order)
Q unsigned long long (always 64 bit, machine byte order)
J unsigned long long (always 64 bit, big endian byte order)
P unsigned long long (always 64 bit, little endian byte order)
f float (machine dependent size and representation)
g float (machine dependent size, little endian byte order)
G float (machine dependent size, big endian byte order)
d double (machine dependent size and representation)
e double (machine dependent size, little endian byte order)
E double (machine dependent size, big endian byte order)
x NUL byte
X Back up one byte
Z NUL-padded string
@ NUL-fill to absolute position
Parameters
  • string format
  • any... _args_
Returns
  • bytes

unpack(format, data, offset)

Unpacks from bytes or a string into a dictionary based on the given format.

  • You may have to name the different format codes and separate them by a slash / to return a string indexed dictionary for easy reference of the destructed parts. If a repeater argument is present, then each of the dictionary keys will have a sequence number behind the given name.

  • See pack() for format options

  • offset is the index of the bytes/string to begin unpacking from

Important If you do not name an element, numeric indices starting from 1 are used. Be aware that if you have more than one unnamed element, some data is overwritten because the numbering restarts from 1 for each element.

Parameters
  • string format
  • bytes|string data
  • number? offset: : Default value is 0
Returns
  • any

pack_from(format, args)

Same as pack() except that instead of accepting arbitrary values after format, it expects the values to be in a list.

Parameters
  • string format
  • list args
Returns
  • bytes

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