45 lines
1.3 KiB
Python
45 lines
1.3 KiB
Python
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import os
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import mmap
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if __name__ == '__main__':
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def memory_map(file_path, access=mmap.ACCESS_WRITE):
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size = os.path.getsize(file_path)
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fild_data = os.open(file_path, os.O_RDWR)
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return mmap.mmap(fild_data, size, access=access)
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SIZE = 1000000
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# with open(r'5.文件与IO/10.data', 'wb') as f:
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# f.seek(SIZE - 1)
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# f.write(b'\x00')
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m = memory_map('5.文件与IO/10.data')
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print(len(m))
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m[0:11] = b'Hello World'
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m.close()
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with open(r'5.文件与IO/10.data', 'rb') as f:
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print(f.read(11))
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# 当然，这个函数得益于他的open内嵌，也能在with的上下文中打开并自动关闭
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with memory_map('5.文件与IO/10.data') as m:
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print(len(m))
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print(m.closed)
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# 当然，如果你想只读，可以在access里设置成mmp.ACCESS_READ,
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# 如果只想把文件拷贝到内存而不是直接在文件里修改，mmp.ACCESS_COPY非常有用
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# mmap和memoryview又有所不同
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m = memory_map('5.文件与IO/10.data')
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v = memoryview(m).cast('I')
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v[0] = 7
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m[0:4] = b'\x07\x01\x00\x00'
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print(m[0:4])
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print(v[0])
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# 可以看出来，memoryview在做转换的时候用的是小端存储
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print(int.from_bytes(m[0:4], byteorder='little'))
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print(int.from_bytes(m[0:4], byteorder='big'))
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v.release()
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m.close()
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