wrapping a C library with cython

A.  look at which function we need to add python module.

/* *  Copyright (c) 2012-2017, Jyri J. Virkki *  All rights reserved. * *  This file is under BSD license. See LICENSE file. */#ifndef _BLOOM_H#define _BLOOM_H#ifdef __cplusplusextern "C" {#endif/** *************************************************************************** * Structure to keep track of one bloom filter.  Caller needs to * allocate this and pass it to the functions below. First call for * every struct must be to bloom_init(). * */struct bloom{  // These fields are part of the public interface of this structure.  // Client code may read these values if desired. Client code MUST NOT  // modify any of these.  int entries;  double error;  int bits;  int bytes;  int hashes;  // Fields below are private to the implementation. These may go away or  // change incompatibly at any moment. Client code MUST NOT access or rely  // on these.  double bpe;  unsigned char * bf;  int ready;};/** *************************************************************************** * Initialize the bloom filter for use. * * The filter is initialized with a bit field and number of hash functions * according to the computations from the wikipedia entry: *     http://en.wikipedia.org/wiki/Bloom_filter * * Optimal number of bits is: *     bits = (entries * ln(error)) / ln(2)^2 * * Optimal number of hash functions is: *     hashes = bpe * ln(2) * * Parameters: * ----------- *     bloom   - Pointer to an allocated struct bloom (see above). *     entries - The expected number of entries which will be inserted. *               Must be at least 1000 (in practice, likely much larger). *     error   - Probability of collision (as long as entries are not *               exceeded). * * Return: * ------- *     0 - on success *     1 - on failure * */int bloom_init(struct bloom * bloom, int entries, double error);/** *************************************************************************** * Deprecated, use bloom_init() * */int bloom_init_size(struct bloom * bloom, int entries, double error,                    unsigned int cache_size);/** *************************************************************************** * Check if the given element is in the bloom filter. Remember this may * return false positive if a collision occured. * * Parameters: * ----------- *     bloom  - Pointer to an allocated struct bloom (see above). *     buffer - Pointer to buffer containing element to check. *     len    - Size of 'buffer'. * * Return: * ------- *     0 - element is not present *     1 - element is present (or false positive due to collision) *    -1 - bloom not initialized * */int bloom_check(struct bloom * bloom, const void * buffer, int len);/** *************************************************************************** * Add the given element to the bloom filter. * The return code indicates if the element (or a collision) was already in, * so for the common check+add use case, no need to call check separately. * * Parameters: * ----------- *     bloom  - Pointer to an allocated struct bloom (see above). *     buffer - Pointer to buffer containing element to add. *     len    - Size of 'buffer'. * * Return: * ------- *     0 - element was not present and was added *     1 - element (or a collision) had already been added previously *    -1 - bloom not initialized * */int bloom_add(struct bloom * bloom, const void * buffer, int len);/** *************************************************************************** * Print (to stdout) info about this bloom filter. Debugging aid. * */void bloom_print(struct bloom * bloom);/** *************************************************************************** * Deallocate internal storage. * * Upon return, the bloom struct is no longer usable. You may call bloom_init * again on the same struct to reinitialize it again. * * Parameters: * ----------- *     bloom  - Pointer to an allocated struct bloom (see above). * * Return: none * */void bloom_free(struct bloom * bloom);/** *************************************************************************** * Returns version string compiled into library. * * Return: version string * */const char * bloom_version();#ifdef __cplusplus}#endif#endif

according to the bloom.h file.

I only want to export the following functions for users:

1. bloom_init

2. bloom_check

3. bloom_free

4. bloom_add

B. write .pxd file to interface with c code

cdef extern from "../bloom.h":     struct bloom:         pass     int bloom_init(bloom * bloom, int entries, double error)     int bloom_check(bloom * bloom, const void * buffer, int len)     int bloom_add(bloom * bloom, const void * buffer, int len)     void bloom_free(bloom * bloom)

C. write .pyx file to interface with python code

# distutils: libraries="bloom"# distutils: library_dirs="." cimport cbloom cdef class Bloom:     cdef cbloom.bloom b     cdef cbloom.bloom * pb     def __cinit__(self, n, error):         self.pb = &self.b         result = cbloom.bloom_init(self.pb, n, error)         if result == 1:             raise Exception('bloom_init failed.')     def __dealloc__(self):         cbloom.bloom_free(self.pb)     def add(self, bytes item):         result = cbloom.bloom_add(self.pb, <void*>item, len(item))         if result == 1:             raise Exception('This item has already been add  ed!')     def __contains__(self, bytes item):         result = cbloom.bloom_check(self.pb, <void*>item, len(item))         return result==1

look at how to use this lib

if u encountered import error, do not forget to add the path of .so file into your LD_LIBRARY_PATH

and source it.