src/tutorial/complex.c

   1 /*
   2  * $PostgreSQL$
   3  *
   4  ******************************************************************************
   5   This file contains routines that can be bound to a Postgres backend and
   6   called by the backend in the process of processing queries.  The calling
   7   format for these routines is dictated by Postgres architecture.
   8 ******************************************************************************/
   9
  10 #include "postgres.h"
  11
  12 #include "fmgr.h"
  13 #include "libpq/pqformat.h"             /* needed for send/recv functions */
  14
  15
  16 PG_MODULE_MAGIC;
  17
  18 typedef struct Complex
  19 {
  20         double          x;
  21         double          y;
  22 }       Complex;
  23
  24 /*
  25  * Since we use V1 function calling convention, all these functions have
  26  * the same signature as far as C is concerned.  We provide these prototypes
  27  * just to forestall warnings when compiled with gcc -Wmissing-prototypes.
  28  */
  29 Datum           complex_in(PG_FUNCTION_ARGS);
  30 Datum           complex_out(PG_FUNCTION_ARGS);
  31 Datum           complex_recv(PG_FUNCTION_ARGS);
  32 Datum           complex_send(PG_FUNCTION_ARGS);
  33 Datum           complex_add(PG_FUNCTION_ARGS);
  34 Datum           complex_abs_lt(PG_FUNCTION_ARGS);
  35 Datum           complex_abs_le(PG_FUNCTION_ARGS);
  36 Datum           complex_abs_eq(PG_FUNCTION_ARGS);
  37 Datum           complex_abs_ge(PG_FUNCTION_ARGS);
  38 Datum           complex_abs_gt(PG_FUNCTION_ARGS);
  39 Datum           complex_abs_cmp(PG_FUNCTION_ARGS);
  40
  41
  42 /*****************************************************************************
  43  * Input/Output functions
  44  *****************************************************************************/
  45
  46 PG_FUNCTION_INFO_V1(complex_in);
  47
  48 Datum
  49 complex_in(PG_FUNCTION_ARGS)
  50 {
  51         char       *str = PG_GETARG_CSTRING(0);
  52         double          x,
  53                                 y;
  54         Complex    *result;
  55
  56         if (sscanf(str, " ( %lf , %lf )", &x, &y) != 2)
  57                 ereport(ERROR,
  58                                 (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
  59                                  errmsg("invalid input syntax for complex: \"%s\"",
  60                                                 str)));
  61
  62         result = (Complex *) palloc(sizeof(Complex));
  63         result->x = x;
  64         result->y = y;
  65         PG_RETURN_POINTER(result);
  66 }
  67
  68 PG_FUNCTION_INFO_V1(complex_out);
  69
  70 Datum
  71 complex_out(PG_FUNCTION_ARGS)
  72 {
  73         Complex    *complex = (Complex *) PG_GETARG_POINTER(0);
  74         char       *result;
  75
  76         result = (char *) palloc(100);
  77         snprintf(result, 100, "(%g,%g)", complex->x, complex->y);
  78         PG_RETURN_CSTRING(result);
  79 }
  80
  81 /*****************************************************************************
  82  * Binary Input/Output functions
  83  *
  84  * These are optional.
  85  *****************************************************************************/
  86
  87 PG_FUNCTION_INFO_V1(complex_recv);
  88
  89 Datum
  90 complex_recv(PG_FUNCTION_ARGS)
  91 {
  92         StringInfo      buf = (StringInfo) PG_GETARG_POINTER(0);
  93         Complex    *result;
  94
  95         result = (Complex *) palloc(sizeof(Complex));
  96         result->x = pq_getmsgfloat8(buf);
  97         result->y = pq_getmsgfloat8(buf);
  98         PG_RETURN_POINTER(result);
  99 }
 100
 101 PG_FUNCTION_INFO_V1(complex_send);
 102
 103 Datum
 104 complex_send(PG_FUNCTION_ARGS)
 105 {
 106         Complex    *complex = (Complex *) PG_GETARG_POINTER(0);
 107         StringInfoData buf;
 108
 109         pq_begintypsend(&buf);
 110         pq_sendfloat8(&buf, complex->x);
 111         pq_sendfloat8(&buf, complex->y);
 112         PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
 113 }
 114
 115 /*****************************************************************************
 116  * New Operators
 117  *
 118  * A practical Complex datatype would provide much more than this, of course.
 119  *****************************************************************************/
 120
 121 PG_FUNCTION_INFO_V1(complex_add);
 122
 123 Datum
 124 complex_add(PG_FUNCTION_ARGS)
 125 {
 126         Complex    *a = (Complex *) PG_GETARG_POINTER(0);
 127         Complex    *b = (Complex *) PG_GETARG_POINTER(1);
 128         Complex    *result;
 129
 130         result = (Complex *) palloc(sizeof(Complex));
 131         result->x = a->x + b->x;
 132         result->y = a->y + b->y;
 133         PG_RETURN_POINTER(result);
 134 }
 135
 136
 137 /*****************************************************************************
 138  * Operator class for defining B-tree index
 139  *
 140  * It's essential that the comparison operators and support function for a
 141  * B-tree index opclass always agree on the relative ordering of any two
 142  * data values.  Experience has shown that it's depressingly easy to write
 143  * unintentionally inconsistent functions.      One way to reduce the odds of
 144  * making a mistake is to make all the functions simple wrappers around
 145  * an internal three-way-comparison function, as we do here.
 146  *****************************************************************************/
 147
 148 #define Mag(c)  ((c)->x*(c)->x + (c)->y*(c)->y)
 149
 150 static int
 151 complex_abs_cmp_internal(Complex * a, Complex * b)
 152 {
 153         double          amag = Mag(a),
 154                                 bmag = Mag(b);
 155
 156         if (amag < bmag)
 157                 return -1;
 158         if (amag > bmag)
 159                 return 1;
 160         return 0;
 161 }
 162
 163
 164 PG_FUNCTION_INFO_V1(complex_abs_lt);
 165
 166 Datum
 167 complex_abs_lt(PG_FUNCTION_ARGS)
 168 {
 169         Complex    *a = (Complex *) PG_GETARG_POINTER(0);
 170         Complex    *b = (Complex *) PG_GETARG_POINTER(1);
 171
 172         PG_RETURN_BOOL(complex_abs_cmp_internal(a, b) < 0);
 173 }
 174
 175 PG_FUNCTION_INFO_V1(complex_abs_le);
 176
 177 Datum
 178 complex_abs_le(PG_FUNCTION_ARGS)
 179 {
 180         Complex    *a = (Complex *) PG_GETARG_POINTER(0);
 181         Complex    *b = (Complex *) PG_GETARG_POINTER(1);
 182
 183         PG_RETURN_BOOL(complex_abs_cmp_internal(a, b) <= 0);
 184 }
 185
 186 PG_FUNCTION_INFO_V1(complex_abs_eq);
 187
 188 Datum
 189 complex_abs_eq(PG_FUNCTION_ARGS)
 190 {
 191         Complex    *a = (Complex *) PG_GETARG_POINTER(0);
 192         Complex    *b = (Complex *) PG_GETARG_POINTER(1);
 193
 194         PG_RETURN_BOOL(complex_abs_cmp_internal(a, b) == 0);
 195 }
 196
 197 PG_FUNCTION_INFO_V1(complex_abs_ge);
 198
 199 Datum
 200 complex_abs_ge(PG_FUNCTION_ARGS)
 201 {
 202         Complex    *a = (Complex *) PG_GETARG_POINTER(0);
 203         Complex    *b = (Complex *) PG_GETARG_POINTER(1);
 204
 205         PG_RETURN_BOOL(complex_abs_cmp_internal(a, b) >= 0);
 206 }
 207
 208 PG_FUNCTION_INFO_V1(complex_abs_gt);
 209
 210 Datum
 211 complex_abs_gt(PG_FUNCTION_ARGS)
 212 {
 213         Complex    *a = (Complex *) PG_GETARG_POINTER(0);
 214         Complex    *b = (Complex *) PG_GETARG_POINTER(1);
 215
 216         PG_RETURN_BOOL(complex_abs_cmp_internal(a, b) > 0);
 217 }
 218
 219 PG_FUNCTION_INFO_V1(complex_abs_cmp);
 220
 221 Datum
 222 complex_abs_cmp(PG_FUNCTION_ARGS)
 223 {
 224         Complex    *a = (Complex *) PG_GETARG_POINTER(0);
 225         Complex    *b = (Complex *) PG_GETARG_POINTER(1);
 226
 227         PG_RETURN_INT32(complex_abs_cmp_internal(a, b));
 228 }