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82 lines
3.4 KiB
Python
82 lines
3.4 KiB
Python
from .lib import TestBase
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class TestTutorial(TestBase):
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def test_example(self):
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# Memory Managers
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##################
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import smmap
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# This instance should be globally available in your application
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# It is configured to be well suitable for 32-bit or 64 bit applications.
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mman = smmap.SlidingWindowMapManager()
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# the manager provides much useful information about its current state
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# like the amount of open file handles or the amount of mapped memory
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assert mman.num_file_handles() == 0
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assert mman.mapped_memory_size() == 0
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# and many more ...
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# Cursors
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##########
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import smmap.test.lib
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with smmap.test.lib.FileCreator(1024 * 1024 * 8, "test_file") as fc:
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# obtain a cursor to access some file.
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c = mman.make_cursor(fc.path)
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# the cursor is now associated with the file, but not yet usable
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assert c.is_associated()
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assert not c.is_valid()
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# before you can use the cursor, you have to specify a window you want to
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# access. The following just says you want as much data as possible starting
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# from offset 0.
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# To be sure your region could be mapped, query for validity
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assert c.use_region().is_valid() # use_region returns self
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# once a region was mapped, you must query its dimension regularly
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# to assure you don't try to access its buffer out of its bounds
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assert c.size()
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c.buffer()[0] # first byte
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c.buffer()[1:10] # first 9 bytes
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c.buffer()[c.size() - 1] # last byte
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# its recommended not to create big slices when feeding the buffer
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# into consumers (e.g. struct or zlib).
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# Instead, either give the buffer directly, or use pythons buffer command.
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from smmap.util import buffer
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buffer(c.buffer(), 1, 9) # first 9 bytes without copying them
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# you can query absolute offsets, and check whether an offset is included
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# in the cursor's data.
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assert c.ofs_begin() < c.ofs_end()
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assert c.includes_ofs(100)
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# If you are over out of bounds with one of your region requests, the
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# cursor will be come invalid. It cannot be used in that state
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assert not c.use_region(fc.size, 100).is_valid()
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# map as much as possible after skipping the first 100 bytes
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assert c.use_region(100).is_valid()
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# You can explicitly free cursor resources by unusing the cursor's region
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c.unuse_region()
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assert not c.is_valid()
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# Buffers
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#########
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# Create a default buffer which can operate on the whole file
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buf = smmap.SlidingWindowMapBuffer(mman.make_cursor(fc.path))
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# you can use it right away
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assert buf.cursor().is_valid()
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buf[0] # access the first byte
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buf[-1] # access the last ten bytes on the file
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buf[-10:] # access the last ten bytes
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# If you want to keep the instance between different accesses, use the
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# dedicated methods
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buf.end_access()
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assert not buf.cursor().is_valid() # you cannot use the buffer anymore
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assert buf.begin_access(offset=10) # start using the buffer at an offset
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