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/pypy/rlib/longlong2float.py

https://bitbucket.org/jakelundy/pypy
Python | 55 lines | 52 code | 0 blank | 3 comment | 0 complexity | 7b4dce4ae3fac5bdd48982c01caa29e6 MD5 | raw file
    

  1. """
    2. 

  2. This module exposes the functions longlong2float() and float2longlong(),
    3. 

  3. which cast the bit pattern of a float into a long long and back.
    4. 

  4. Warning: don't use in the other direction, i.e. don't cast a random
    5. 

  5. long long to a float and back to a long long.  There are corner cases
    6. 

  6. in which it does not work.
    7. 

  7. """
    8. 

  8. from pypy.rpython.lltypesystem import lltype, rffi
    9. 

  9. 

  10. 

  11. # -------- implement longlong2float and float2longlong --------
    12. 

  12. DOUBLE_ARRAY_PTR = lltype.Ptr(lltype.Array(rffi.DOUBLE))
    13. 

  13. LONGLONG_ARRAY_PTR = lltype.Ptr(lltype.Array(rffi.LONGLONG))
    14. 

  14. 

  15. # these definitions are used only in tests, when not translated
    16. 

  16. def longlong2float_emulator(llval):
    17. 

  17.     d_array = lltype.malloc(DOUBLE_ARRAY_PTR.TO, 1, flavor='raw')
    18. 

  18.     ll_array = rffi.cast(LONGLONG_ARRAY_PTR, d_array)
    19. 

  19.     ll_array[0] = llval
    20. 

  20.     floatval = d_array[0]
    21. 

  21.     lltype.free(d_array, flavor='raw')
    22. 

  22.     return floatval
    23. 

  23. 

  24. def float2longlong_emulator(floatval):
    25. 

  25.     d_array = lltype.malloc(DOUBLE_ARRAY_PTR.TO, 1, flavor='raw')
    26. 

  26.     ll_array = rffi.cast(LONGLONG_ARRAY_PTR, d_array)
    27. 

  27.     d_array[0] = floatval
    28. 

  28.     llval = ll_array[0]
    29. 

  29.     lltype.free(d_array, flavor='raw')
    30. 

  30.     return llval
    31. 

  31. 

  32. from pypy.translator.tool.cbuild import ExternalCompilationInfo
    33. 

  33. eci = ExternalCompilationInfo(includes=['string.h'],
    34. 

  34.                               post_include_bits=["""
    35. 

  35. static double pypy__longlong2float(long long x) {
    36. 

  36.     double dd;
    37. 

  37.     memcpy(&dd, &x, 8);
    38. 

  38.     return dd;
    39. 

  39. }
    40. 

  40. static long long pypy__float2longlong(double x) {
    41. 

  41.     long long ll;
    42. 

  42.     memcpy(&ll, &x, 8);
    43. 

  43.     return ll;
    44. 

  44. }
    45. 

  45. """])
    46. 

    47. 

  47. longlong2float = rffi.llexternal(
    48. 

  48.     "pypy__longlong2float", [rffi.LONGLONG], rffi.DOUBLE,
    49. 

  49.     _callable=longlong2float_emulator, compilation_info=eci,
    50. 

  50.     _nowrapper=True, pure_function=True)
    51. 

  51. 

  52. float2longlong = rffi.llexternal(
    53. 

  53.     "pypy__float2longlong", [rffi.DOUBLE], rffi.LONGLONG,
    54. 

  54.     _callable=float2longlong_emulator, compilation_info=eci,
    55. 

  55.     _nowrapper=True, pure_function=True)
    56. 

  56.