84674909a2
This PR is for resolving the following issue: [issue](https://github.com/capnproto/pycapnp/issues/379) 1. Created `_PyCustomMessageBuilder` extends `MessageBuilder`, enabling the ability to customise the `SegmentAllocate` method in Python. This allows allocation and data population within shared memory, and supports zero-copy inter-process data transfer by passing segment offsets. 2. Fields of type `Data` now support being set with a `memoryview`. When retrieving a `Data` field from a `DynamicStructBuilder`, it will return a writable `memoryview`, allowing users to modify the data directly. This enables memory to be pre-allocated and content to be modified in later, eliminating an extra copy. When retrieving a `Data` field from a `DynamicStructReader`, it will return a read-only `memoryview`, allowing user to read data without memory copy. * add memoryview and custom builder * support set dynamic field * add curSize * add initialSize and lastSize * change StringPtr name * add test case * refine test case * convert func to py callable object * add initial value * refine example * add copy as_reader and new_message, make structReader's data field return RO memoryView * rebase master and bugfix * reformat flake8 * refine test case * refine test cases for blob * remove unused import for flake8 * run black . --------- Co-authored-by: Brian Xu <brian.xu1@bytedance.com>
49 lines
1.1 KiB
Python
49 lines
1.1 KiB
Python
#!/usr/bin/env python3
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import capnp # noqa: F401
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import addressbook_capnp
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class Allocator:
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def __init__(self):
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self.cur_size = 0
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self.last_size = 0
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def __call__(self, minimum_size: int) -> bytearray:
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actual_size = max(minimum_size, self.cur_size)
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print(
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f"minimum_size: {minimum_size}, last_size: {self.last_size}, "
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f"actual_size: {actual_size}, cur_size: {self.cur_size}"
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)
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self.last_size = actual_size
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self.cur_size += actual_size
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WORD_SIZE = 8
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byte_count = actual_size * WORD_SIZE
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return bytearray(byte_count)
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person = addressbook_capnp.Person.new_message(allocate_seg_callable=Allocator())
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person.init("extraData", 5)
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print(person.extraData)
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print(bytes(person.extraData))
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print(type(person.extraData))
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print()
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person.extraData[1] = 0xFF
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print(person.extraData)
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print(bytes(person.extraData))
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print()
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person.extraData = b"hello"
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print(person.extraData)
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print(bytes(person.extraData))
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print(type(person.extraData))
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print()
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person = person.as_reader()
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print(person.extraData)
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print(bytes(person.extraData))
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print(type(person.extraData))
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