ghc/runtime/prims/ByteOps.lc

   1 %---------------------------------------------------------------*
   2 %
   3 \section{Underlying code for converting to/from ``bytes''}
   4 %
   5 %---------------------------------------------------------------*
   6
   7 Stolen from HBC, more or less.
   8
   9 A \tr{I_ foo2bytes__(foo in, ptr arr)} routine takes a \tr{foo}
  10 input \tr{in}, scribbles some appropriate bytes into the array passed
  11 to it, \tr{arr}, and returns the number of bytes so put.
  12
  13 A \tr{I_ bytes2foo__(ptr arr, foo *out)} routine looks at the
  14 array of bytes given to it (\tr{arr}) and gives them back interpreted
  15 as a \tr{foo} (sticks it in the place pointed to by \tr{out}).  It
  16 returns the number of bytes taken.
  17
  18 \begin{code}
  19
  20 #include "rtsdefs.h"
  21
  22 #if __STDC__
  23     /* need the ANSI arg decl, so "short" and "float" args dont get promoted */
  24 #define X2BYTES(type)                           \
  25 I_                                              \
  26 CAT2(type,2bytes__)(type in, unsigned char *arr)\
  27 {                                               \
  28     union {                                     \
  29         type i;                                 \
  30         unsigned char cs[sizeof (type)];        \
  31     } u;                                        \
  32     int k;                                      \
  33                                                 \
  34     u.i = in;                                   \
  35     for (k = sizeof (type) - 1; k >= 0; k--)    \
  36         arr[k] = u.cs[k];                       \
  37                                                 \
  38     return(sizeof (type));                      \
  39 }
  40
  41 #else /* not STDC */
  42 #define X2BYTES(type)                           \
  43 I_                                              \
  44 CAT2(type,2bytes__)(in, arr)                    \
  45   type in;                                      \
  46   unsigned char *arr;                           \
  47 {                                               \
  48     union {                                     \
  49         type i;                                 \
  50         unsigned char cs[sizeof (type)];        \
  51     } u;                                        \
  52     int k;                                      \
  53                                                 \
  54     u.i = in;                                   \
  55     for (k = sizeof (type) - 1; k >= 0; k--)    \
  56         arr[k] = u.cs[k];                       \
  57                                                 \
  58     return(sizeof (type));                      \
  59 }
  60 #endif /* not STDC */
  61
  62 X2BYTES(long)
  63 X2BYTES(int)
  64 X2BYTES(short)
  65 X2BYTES(float)
  66 X2BYTES(double)
  67
  68 #define BYTES2X(ctype,htype)                    \
  69 I_                                              \
  70 CAT3(bytes2,ctype,__)(P_ in, htype *out)        \
  71 {                                               \
  72     union {                                     \
  73         ctype i;                                \
  74         unsigned char cs[sizeof (ctype)];       \
  75     } u;                                        \
  76     int k;                                      \
  77     unsigned char *arr = (unsigned char *) in;  \
  78                                                 \
  79     for (k = 0; k < sizeof(ctype); k++)         \
  80         u.cs[k] = arr[k];                       \
  81                                                 \
  82     *out = (htype) u.i;                         \
  83                                                 \
  84     return(sizeof (ctype));                     \
  85 }
  86
  87 static STG_INLINE
  88 void
  89 assign_flt(W_ p_dest[], StgFloat src)
  90 {
  91     float_thing y;
  92     y.f = src;
  93     *p_dest = y.fu;
  94 }
  95
  96
  97 static STG_INLINE
  98 void
  99 assign_dbl(W_ p_dest[], StgDouble src)
 100 {
 101     double_thing y;
 102     y.d = src;
 103     p_dest[0] = y.du.dhi;
 104     p_dest[1] = y.du.dlo;
 105 }
 106
 107 #define BYTES2FX(ctype,htype,assign_fx)         \
 108 I_                                              \
 109 CAT3(bytes2,ctype,__)(P_ in, htype *out)        \
 110 {                                               \
 111     union {                                     \
 112         ctype i;                                \
 113         unsigned char cs[sizeof (ctype)];       \
 114     } u;                                        \
 115     int k;                                      \
 116     unsigned char *arr = (unsigned char *) in;  \
 117                                                 \
 118     for (k = 0; k < sizeof(ctype); k++)         \
 119         u.cs[k] = arr[k];                       \
 120                                                 \
 121     assign_fx(out, (htype) u.i);                \
 122                                                 \
 123     return(sizeof (ctype));                     \
 124 }
 125
 126 BYTES2X(long,I_)
 127 BYTES2X(int,I_)
 128 BYTES2X(short,I_)
 129
 130 BYTES2FX(float,StgFloat,assign_flt)
 131 BYTES2FX(double,StgDouble,assign_dbl)
 132 \end{code}