Module pickle

Index

Below is a list of all pickle functions.

pickle.pack(format, argument[, argument ...])¶

To use Tarantool binary protocol primitives from Lua, it’s necessary to convert Lua variables to binary format. The pickle.pack() helper function is prototyped after Perl pack.

Format specifiers

b, B	converts Lua scalar value to a 1-byte integer, and stores the integer in the resulting string
s, S	converts Lua scalar value to a 2-byte integer, and stores the integer in the resulting string, low byte first
i, I	converts Lua scalar value to a 4-byte integer, and stores the integer in the resulting string, low byte first
l, L	converts Lua scalar value to an 8-byte integer, and stores the integer in the resulting string, low byte first
n	converts Lua scalar value to a 2-byte integer, and stores the integer in the resulting string, big endian,
N	converts Lua scalar value to a 4-byte integer, and stores the integer in the resulting string, big
q, Q	converts Lua scalar value to an 8-byte integer, and stores the integer in the resulting string, big endian,
f	converts Lua scalar value to a 4-byte float, and stores the float in the resulting string
d	converts Lua scalar value to a 8-byte double, and stores the double in the resulting string
a, A	converts Lua scalar value to a sequence of bytes, and stores the sequence in the resulting string

Parameters:	format (string) – string containing format specifiers argument(s) (scalar-value) – scalar values to be formatted
Return:	a binary string containing all arguments, packed according to the format specifiers.
Rtype:	string

A scalar value can be either a variable or a literal. Remember that large integers should be entered with tonumber64() or LL or ULL suffixes.

Possible errors: unknown format specifier.

Example:

tarantool> pickle = require('pickle')
---
...
tarantool> box.space.tester:insert{0, 'hello world'}
---
- [0, 'hello world']
...
tarantool> box.space.tester:update({0}, {{'=', 2, 'bye world'}})
---
- [0, 'bye world']
...
tarantool> box.space.tester:update({0}, {
         >   {'=', 2, pickle.pack('iiA', 0, 3, 'hello')}
         > })
---
- [0, "\0\0\0\0\x03\0\0\0hello"]
...
tarantool> box.space.tester:update({0}, {{'=', 2, 4}})
---
- [0, 4]
...
tarantool> box.space.tester:update({0}, {{'+', 2, 4}})
---
- [0, 8]
...
tarantool> box.space.tester:update({0}, {{'^', 2, 4}})
---
- [0, 12]
...

pickle.unpack(format, binary-string)¶

Counterpart to pickle.pack(). Warning: if format specifier ‘A’ is used, it must be the last item.

Parameters:	format (string) – binary-string (string) –
Return:	A list of strings or numbers.
Rtype:	table

Example:

tarantool> pickle = require('pickle')
---
...
tarantool> tuple = box.space.tester:replace{0}
---
...
tarantool> string.len(tuple[1])
---
- 1
...
tarantool> pickle.unpack('b', tuple[1])
---
- 48
...
tarantool> pickle.unpack('bsi', pickle.pack('bsi', 255, 65535, 4294967295))
---
- 255
- 65535
- 4294967295
...
tarantool> pickle.unpack('ls', pickle.pack('ls', tonumber64('18446744073709551615'), 65535))
---
...
tarantool> num, num64, str = pickle.unpack('slA', pickle.pack('slA', 666,
         > tonumber64('666666666666666'), 'string'))
---
...