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Binread

Parse any binary format 📖


Installation

pip install binread

Usage

Just create a class with each field representing a certain data-type and decorate it with formatclass, then pass some bytes to <cls>.read():

from binread import Format, U16, Array, formatclass

data = open('example.bin', 'rb').read()

@formatclass
class Fmt:
  field0 = U16,
  field1 = Array(U16, length=5)

print(Fmt.read(data))
# Fmt(field0=16, field1=[1, 2, 3, 4, 5])

Or create a dictionary mapping for each field and it's type and construct a Format object.

fmt = Format({
  "field0": U16,
  "field1": Array(U16, length=5)
})

print(fmt.read(data))
# {
#   "field0": 16,
#   "field1": [1, 2, 3, 4, 5]
# }

Format.read() expects a bytes object and by default raises an exception if there are bytes left over. Set allow_leftover=True to disable this behaviour. If leftover bytes are allowed, the number of bytes that where read can be inspected with return_bytes=True.

Arrays

Other than supporting fixed length arrays with passing an integer to length, binread supports multiple techniques of defining variable length arrays.

Using a previously defined field in the same Format.

Format({
  "length_key": U16,
  "array": Array(U8, length="length_key")
})

Using a function or lambda (with access to previously defined fields as a dict)

Format({
  "length_key": U16,
  "array": Array(U8, length=lambda x: x["length_key"] + 1)
})

When specifying length_bytes instead of length the bytes are counted instead of the elements.

Format({
  "length_key": U16,
  "array": Array(String(length=7, encoding='ascii'), length_bytes="length_key")
})

When dealing with a terminated array, terminator can be used to define when to stop.

fmt = Format({
  "array": Array(U8, terminator=b'\x00')
})

The terminator is checked at the first byte or the byte immediately after an element.

Nested Formats

The Format type can be used a in another Format or Array just as any other type.

Format({
  "field1": I32,
  "nested_format": Format({
    "field1": U64
  })
})

Format({
  "array": Array(Format({
    "field1": Bool,
    "field2": Char,
  }), length=4)
})

Byte Order

Any field type (or formatclass decorator) accepts a byteorder value in it's constructor, which can be little, big or native (default). The fields inside of Format, Tuple, Array and formatclass inherit it's parent byteorder if one is not explicitly given to that field.

No padding or alignment is done at all. For packing C structures with padding and alignment see struct

Supported Types

Binread supports the following types

  • Structural: Array, Tuple and Format
  • Signed integers: I8, I16, I32, I64
  • Unsigned Integers: U8, U16, U32, U64
  • Floats: F16, F32, F64
  • Misc: Char, String, Bool, Bytes