| #------------------------------------------------------------------------------- |
| # elftools: common/utils.py |
| # |
| # Miscellaneous utilities for elftools |
| # |
| # Eli Bendersky (eliben@gmail.com) |
| # This code is in the public domain |
| #------------------------------------------------------------------------------- |
| from .exceptions import ELFParseError, ELFError, DWARFError |
| from ..construct import ConstructError |
| |
| |
| def bytelist2string(bytelist): |
| """ Convert a list of byte values (e.g. [0x10 0x20 0x00]) to a string |
| (e.g. '\x10\x20\x00'). |
| """ |
| return ''.join(chr(b) for b in bytelist) |
| |
| |
| def struct_parse(struct, stream, stream_pos=None): |
| """ Convenience function for using the given struct to parse a stream. |
| If stream_pos is provided, the stream is seeked to this position before |
| the parsing is done. Otherwise, the current position of the stream is |
| used. |
| Wraps the error thrown by construct with ELFParseError. |
| """ |
| try: |
| if stream_pos is not None: |
| stream.seek(stream_pos) |
| return struct.parse_stream(stream) |
| except ConstructError as e: |
| raise ELFParseError(e.message) |
| |
| |
| def parse_cstring_from_stream(stream, stream_pos=None): |
| """ Parse a C-string from the given stream. The string is returned without |
| the terminating \x00 byte. |
| If stream_pos is provided, the stream is seeked to this position before |
| the parsing is done. Otherwise, the current position of the stream is |
| used. |
| """ |
| # I could've just used construct.CString, but this function is 4x faster. |
| # Since it's needed a lot, I created it as an optimization. |
| if stream_pos is not None: |
| stream.seek(stream_pos) |
| return ''.join(iter(lambda: stream.read(1), '\x00')) |
| |
| |
| def elf_assert(cond, msg=''): |
| """ Assert that cond is True, otherwise raise ELFError(msg) |
| """ |
| _assert_with_exception(cond, msg, ELFError) |
| |
| |
| def dwarf_assert(cond, msg=''): |
| """ Assert that cond is True, otherwise raise DWARFError(msg) |
| """ |
| _assert_with_exception(cond, msg, DWARFError) |
| |
| |
| def _assert_with_exception(cond, msg, exception_type): |
| if not cond: |
| raise exception_type(msg) |
| |
| |
| from contextlib import contextmanager |
| |
| @contextmanager |
| def preserve_stream_pos(stream): |
| """ Usage: |
| |
| # stream has some position FOO (return value of stream.tell()) |
| with preserve_stream_pos(stream): |
| # do stuff that manipulates the stream |
| # stream still has position FOO |
| """ |
| saved_pos = stream.tell() |
| yield |
| stream.seek(saved_pos) |