TinyFrame, Python version
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PonyFrame/PayloadParser.py

89 lines
2.5 KiB

import struct
class PayloadParser:
"""
Utility for parsing a binary payload
"""
def __init__(self, buf, endian='little'):
""" buf - buffer to parse (bytearray or binary string) """
self.buf = buf
self.ptr = 0
self.endian = endian
def _slice(self, n):
""" Extract a slice and advance the read pointer for the next slice """
if self.ptr + n > len(self.buf):
raise Exception("Out of bounds")
slice = self.buf[self.ptr:self.ptr + n]
self.ptr += n
return slice
def rewind(self):
""" Reset the slice pointer to the beginning """
self.ptr = 0
def tail(self):
""" Get all remaining bytes """
return self._slice(len(self.buf) - self.ptr)
def u8(self):
""" Read a uint8_t """
slice = self._slice(1)
return int.from_bytes(slice, byteorder=self.endian, signed=False)
def u16(self):
""" Read a uint16_t """
slice = self._slice(2)
return int.from_bytes(slice, byteorder=self.endian, signed=False)
def u32(self):
""" Read a uint32_t """
slice = self._slice(4)
return int.from_bytes(slice, byteorder=self.endian, signed=False)
def i8(self):
""" Read a int8_t """
slice = self._slice(1)
return int.from_bytes(slice, byteorder=self.endian, signed=True)
def i16(self):
""" Read a int16_t """
slice = self._slice(2)
return int.from_bytes(slice, byteorder=self.endian, signed=True)
def i32(self):
""" Read a int32_t """
slice = self._slice(4)
return int.from_bytes(slice, byteorder=self.endian, signed=True)
def float(self):
""" Read a float (4 bytes) """
slice = self._slice(4)
fmt = '<f' if self.endian == 'little' else '>f'
return struct.unpack(fmt, slice)[0]
def double(self):
""" Read a double (8 bytes) """
slice = self._slice(8)
fmt = '<d' if self.endian == 'little' else '>d'
return struct.unpack(fmt, slice)[0]
def bool(self):
""" Read a bool (1 byte, True if != 0) """
return 0 != self._slice(1)[0]
def str(self):
""" Read a zero-terminated string """
p = self.ptr
while p < len(self.buf) and self.buf[p] != 0:
p += 1
bs = self._slice(p - self.ptr)
self.ptr += 1
return bs.decode('utf-8')
def blob(self, length):
""" Read a blob of given length """
return self._slice(length)