205 lines
8.3 KiB
ReStructuredText
205 lines
8.3 KiB
ReStructuredText
.. _mpy_files:
|
|
|
|
MicroPython .mpy files
|
|
======================
|
|
|
|
MicroPython defines the concept of an .mpy file which is a binary container
|
|
file format that holds precompiled code, and which can be imported like a
|
|
normal .py module. The file ``foo.mpy`` can be imported via ``import foo``,
|
|
as long as ``foo.mpy`` can be found in the usual way by the import machinery.
|
|
Usually, each directory listed in ``sys.path`` is searched in order. When
|
|
searching a particular directory ``foo.py`` is looked for first and if that
|
|
is not found then ``foo.mpy`` is looked for, then the search continues in the
|
|
next directory if neither is found. As such, ``foo.py`` will take precedence
|
|
over ``foo.mpy``.
|
|
|
|
These .mpy files can contain bytecode which is usually generated from Python
|
|
source files (.py files) via the ``mpy-cross`` program. For some architectures
|
|
an .mpy file can also contain native machine code, which can be generated in
|
|
a variety of ways, most notably from C source code.
|
|
|
|
Versioning and compatibility of .mpy files
|
|
------------------------------------------
|
|
|
|
A given .mpy file may or may not be compatible with a given MicroPython system.
|
|
Compatibility is based on the following:
|
|
|
|
* Version of the .mpy file: the version of the file must match the version
|
|
supported by the system loading it.
|
|
|
|
* Sub-version of the .mpy file: if the .mpy file contains native machine code
|
|
then the sub-version of the file must match the version support by the
|
|
system loading it. Otherwise, if there is no native machine code in the .mpy
|
|
file, then the sub-version is ignored when loading.
|
|
|
|
* Small integer bits: the .mpy file will require a minimum number of bits in
|
|
a small integer and the system loading it must support at least this many
|
|
bits.
|
|
|
|
* Native architecture: if the .mpy file contains native machine code then
|
|
it will specify the architecture of that machine code and the system
|
|
loading it must support execution of that architecture's code.
|
|
|
|
If a MicroPython system supports importing .mpy files then the
|
|
``sys.implementation._mpy`` field will exist and return an integer which
|
|
encodes the version (lower 8 bits), features and native architecture.
|
|
|
|
Trying to import an .mpy file that fails one of the first four tests will
|
|
raise ``ValueError('incompatible .mpy file')``. Trying to import an .mpy
|
|
file that fails the native architecture test (if it contains native machine
|
|
code) will raise ``ValueError('incompatible .mpy arch')``.
|
|
|
|
If importing an .mpy file fails then try the following:
|
|
|
|
* Determine the .mpy version and flags supported by your MicroPython system
|
|
by executing::
|
|
|
|
import sys
|
|
sys_mpy = sys.implementation._mpy
|
|
arch = [None, 'x86', 'x64',
|
|
'armv6', 'armv6m', 'armv7m', 'armv7em', 'armv7emsp', 'armv7emdp',
|
|
'xtensa', 'xtensawin'][sys_mpy >> 10]
|
|
print('mpy version:', sys_mpy & 0xff)
|
|
print('mpy sub-version:', sys_mpy >> 8 & 3)
|
|
print('mpy flags:', end='')
|
|
if arch:
|
|
print(' -march=' + arch, end='')
|
|
print()
|
|
|
|
* Check the validity of the .mpy file by inspecting the first two bytes of
|
|
the file. The first byte should be an uppercase 'M' and the second byte
|
|
will be the version number, which should match the system version from above.
|
|
If it doesn't match then rebuild the .mpy file.
|
|
|
|
* Check if the system .mpy version matches the version emitted by ``mpy-cross``
|
|
that was used to build the .mpy file, found by ``mpy-cross --version``.
|
|
If it doesn't match then recompile ``mpy-cross`` from the Git repository
|
|
checked out at the tag (or hash) reported by ``mpy-cross --version``.
|
|
|
|
* Make sure you are using the correct ``mpy-cross`` flags, found by the code
|
|
above, or by inspecting the ``MPY_CROSS_FLAGS`` Makefile variable for the
|
|
port that you are using.
|
|
|
|
The following table shows the correspondence between MicroPython release
|
|
and .mpy version.
|
|
|
|
=================== ============
|
|
MicroPython release .mpy version
|
|
=================== ============
|
|
v1.22.0 and up 6.2
|
|
v1.20 - v1.21.0 6.1
|
|
v1.19.x 6
|
|
v1.12 - v1.18 5
|
|
v1.11 4
|
|
v1.9.3 - v1.10 3
|
|
v1.9 - v1.9.2 2
|
|
v1.5.1 - v1.8.7 0
|
|
=================== ============
|
|
|
|
For completeness, the next table shows the Git commit of the main
|
|
MicroPython repository at which the .mpy version was changed.
|
|
|
|
=================== ========================================
|
|
.mpy version change Git commit
|
|
=================== ========================================
|
|
6.1 to 6.2 6967ff3c581a66f73e9f3d78975f47528db39980
|
|
6 to 6.1 d94141e1473aebae0d3c63aeaa8397651ad6fa01
|
|
5 to 6 f2040bfc7ee033e48acef9f289790f3b4e6b74e5
|
|
4 to 5 5716c5cf65e9b2cb46c2906f40302401bdd27517
|
|
3 to 4 9a5f92ea72754c01cc03e5efcdfe94021120531e
|
|
2 to 3 ff93fd4f50321c6190e1659b19e64fef3045a484
|
|
1 to 2 dd11af209d226b7d18d5148b239662e30ed60bad
|
|
0 to 1 6a11048af1d01c78bdacddadd1b72dc7ba7c6478
|
|
initial version 0 d8c834c95d506db979ec871417de90b7951edc30
|
|
=================== ========================================
|
|
|
|
Binary encoding of .mpy files
|
|
-----------------------------
|
|
|
|
MicroPython .mpy files are a binary container format with code objects (bytecode
|
|
and native machine code) stored internally in a nested hierarchy. The code for
|
|
the outer module is stored first, and then its children follow. Each child may
|
|
have further children, for example in the case of a class having methods, or a
|
|
function defining a lambda or comprehension. To keep files small while still
|
|
providing a large range of possible values it uses the concept of a
|
|
variably-encoded-unsigned-integer (vuint) in many places. Similar to utf-8
|
|
encoding, this encoding stores 7 bits per byte with the 8th bit (MSB) set
|
|
if one or more bytes follow. The bits of the unsigned integer are stored
|
|
in the vuint in LSB form.
|
|
|
|
The top-level of an .mpy file consists of three parts:
|
|
|
|
* The header.
|
|
|
|
* The global qstr and constant tables.
|
|
|
|
* The raw-code for the outer scope of the module.
|
|
This outer scope is executed when the .mpy file is imported.
|
|
|
|
You can inspect the contents of a .mpy file by using ``mpy-tool.py``, for
|
|
example (run from the root of the main MicroPython repository)::
|
|
|
|
$ ./tools/mpy-tool.py -xd myfile.mpy
|
|
|
|
The header
|
|
~~~~~~~~~~
|
|
|
|
The .mpy header is:
|
|
|
|
====== ================================
|
|
size field
|
|
====== ================================
|
|
byte value 0x4d (ASCII 'M')
|
|
byte .mpy major version number
|
|
byte native arch and minor version number (was feature flags in older versions)
|
|
byte number of bits in a small int
|
|
====== ================================
|
|
|
|
The global qstr and constant tables
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
An .mpy file contains a single qstr table, and a single constant object table.
|
|
These are global to the .mpy file, they are referenced by all nested raw-code
|
|
objects. The qstr table maps internal qstr number (internal to the .mpy file)
|
|
to the resolved qstr number of the runtime that the .mpy file is imported into.
|
|
This links the .mpy file with the rest of the system that it executes within.
|
|
The constant object table is populated with references to all constant objects
|
|
that the .mpy file needs.
|
|
|
|
====== ================================
|
|
size field
|
|
====== ================================
|
|
vuint number of qstrs
|
|
vuint number of constant objects
|
|
... qstr data
|
|
... encoded constant objects
|
|
====== ================================
|
|
|
|
Raw code elements
|
|
~~~~~~~~~~~~~~~~~
|
|
|
|
A raw-code element contains code, either bytecode or native machine code. Its
|
|
contents are:
|
|
|
|
====== ================================
|
|
size field
|
|
====== ================================
|
|
vuint type, size and whether there are sub-raw-code elements
|
|
... code (bytecode or machine code)
|
|
vuint number of sub-raw-code elements (only if non-zero)
|
|
... sub-raw-code elements
|
|
====== ================================
|
|
|
|
The first vuint in a raw-code element encodes the type of code stored in this
|
|
element (the two least-significant bits), whether this raw-code has any
|
|
children (the third least-significant bit), and the length of the code that
|
|
follows (the amount of RAM to allocate for it).
|
|
|
|
Following the vuint comes the code itself. Unless the code type is viper code
|
|
with relocations, this code is constant data and does not need to be modified.
|
|
|
|
If this raw-code has any children (as indicated by a bit in the first vuint),
|
|
following the code comes a vuint counting the number of sub-raw-code elements.
|
|
|
|
Finally any sub-raw-code elements are stored, recursively.
|