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update README #561

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update README #561

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methane Sep 13, 2023
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116 changes: 50 additions & 66 deletions README.md
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Original file line number Diff line number Diff line change
@@ -10,53 +10,6 @@ It lets you exchange data among multiple languages like JSON.
But it's faster and smaller.
This package provides CPython bindings for reading and writing MessagePack data.


## Very important notes for existing users

### PyPI package name

Package name on PyPI was changed from `msgpack-python` to `msgpack` from 0.5.

When upgrading from msgpack-0.4 or earlier, do `pip uninstall msgpack-python` before
`pip install -U msgpack`.


### Compatibility with the old format

You can use `use_bin_type=False` option to pack `bytes`
object into raw type in the old msgpack spec, instead of bin type in new msgpack spec.

You can unpack old msgpack format using `raw=True` option.
It unpacks str (raw) type in msgpack into Python bytes.

See note below for detail.


### Major breaking changes in msgpack 1.0

* Python 2

* The extension module does not support Python 2 anymore.
The pure Python implementation (`msgpack.fallback`) is used for Python 2.

* Packer

* `use_bin_type=True` by default. bytes are encoded in bin type in msgpack.
**If you are still using Python 2, you must use unicode for all string types.**
You can use `use_bin_type=False` to encode into old msgpack format.
* `encoding` option is removed. UTF-8 is used always.

* Unpacker

* `raw=False` by default. It assumes str types are valid UTF-8 string
and decode them to Python str (unicode) object.
* `encoding` option is removed. You can use `raw=True` to support old format.
* Default value of `max_buffer_size` is changed from 0 to 100 MiB.
* Default value of `strict_map_key` is changed to True to avoid hashdos.
You need to pass `strict_map_key=False` if you have data which contain map keys
which type is not bytes or str.


## Install

```
@@ -65,12 +18,9 @@ $ pip install msgpack

### Pure Python implementation

The extension module in msgpack (`msgpack._cmsgpack`) does not support
Python 2 and PyPy.

But msgpack provides a pure Python implementation (`msgpack.fallback`)
for PyPy and Python 2.
The extension module in msgpack (`msgpack._cmsgpack`) does not support PyPy.

But msgpack provides a pure Python implementation (`msgpack.fallback`) for PyPy.


### Windows
@@ -82,10 +32,6 @@ Without extension, using pure Python implementation on CPython runs slowly.

## How to use

NOTE: In examples below, I use `raw=False` and `use_bin_type=True` for users
using msgpack < 1.0. These options are default from msgpack 1.0 so you can omit them.


### One-shot pack & unpack

Use `packb` for packing and `unpackb` for unpacking.
@@ -97,16 +43,16 @@ msgpack provides `dumps` and `loads` as an alias for compatibility with

```pycon
>>> import msgpack
>>> msgpack.packb([1, 2, 3], use_bin_type=True)
>>> msgpack.packb([1, 2, 3])
'\x93\x01\x02\x03'
>>> msgpack.unpackb(_, raw=False)
>>> msgpack.unpackb(_)
[1, 2, 3]
```

`unpack` unpacks msgpack's array to Python's list, but can also unpack to tuple:

```pycon
>>> msgpack.unpackb(b'\x93\x01\x02\x03', use_list=False, raw=False)
>>> msgpack.unpackb(b'\x93\x01\x02\x03', use_list=False)
(1, 2, 3)
```

@@ -127,11 +73,11 @@ from io import BytesIO

buf = BytesIO()
for i in range(100):
buf.write(msgpack.packb(i, use_bin_type=True))
buf.write(msgpack.packb(i))

buf.seek(0)

unpacker = msgpack.Unpacker(buf, raw=False)
unpacker = msgpack.Unpacker(buf)
for unpacked in unpacker:
print(unpacked)
```
@@ -162,8 +108,8 @@ def encode_datetime(obj):
return obj


packed_dict = msgpack.packb(useful_dict, default=encode_datetime, use_bin_type=True)
this_dict_again = msgpack.unpackb(packed_dict, object_hook=decode_datetime, raw=False)
packed_dict = msgpack.packb(useful_dict, default=encode_datetime)
this_dict_again = msgpack.unpackb(packed_dict, object_hook=decode_datetime)
```

`Unpacker`'s `object_hook` callback receives a dict; the
@@ -191,8 +137,8 @@ It is also possible to pack/unpack custom data types using the **ext** type.
... return ExtType(code, data)
...
>>> data = array.array('d', [1.2, 3.4])
>>> packed = msgpack.packb(data, default=default, use_bin_type=True)
>>> unpacked = msgpack.unpackb(packed, ext_hook=ext_hook, raw=False)
>>> packed = msgpack.packb(data, default=default)
>>> unpacked = msgpack.unpackb(packed, ext_hook=ext_hook)
>>> data == unpacked
True
```
@@ -210,7 +156,7 @@ in a map, can be unpacked or skipped individually.

## Notes

### string and binary type
### string and binary type in old msgpack spec

Early versions of msgpack didn't distinguish string and binary types.
The type for representing both string and binary types was named **raw**.
@@ -263,3 +209,41 @@ You can use `gc.disable()` when unpacking large message.
List is the default sequence type of Python.
But tuple is lighter than list.
You can use `use_list=False` while unpacking when performance is important.


## Major breaking changes in the history

### msgpack 0.5

Package name on PyPI was changed from `msgpack-python` to `msgpack` from 0.5.

When upgrading from msgpack-0.4 or earlier, do `pip uninstall msgpack-python` before
`pip install -U msgpack`.


### msgpack 1.0

* Python 2 support

* The extension module does not support Python 2 anymore.
The pure Python implementation (`msgpack.fallback`) is used for Python 2.

* msgpack 1.0.6 drops official support of Python 2.7, as pip and
GitHub Action (setup-python) no longer support Python 2.7.

* Packer

* Packer uses `use_bin_type=True` by default.
Bytes are encoded in bin type in msgpack.
* The `encoding` option is removed. UTF-8 is used always.

* Unpacker

* Unpacker uses `raw=False` by default. It assumes str types are valid UTF-8 string
and decode them to Python str (unicode) object.
* `encoding` option is removed. You can use `raw=True` to support old format (e.g. unpack into bytes, not str).
* Default value of `max_buffer_size` is changed from 0 to 100 MiB to avoid DoS attack.
You need to pass `max_buffer_size=0` if you have large but safe data.
* Default value of `strict_map_key` is changed to True to avoid hashdos.
You need to pass `strict_map_key=False` if you have data which contain map keys
which type is not bytes or str.