granicus.if.org Git - postgresql/blob - src/tutorial/complex.c

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