types.c

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/*
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 *   Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/** Boxed value structures and functions to manipulate them
 *
 * @file src/lib/util/types.c
 *
 * @copyright 2021 The FreeRADIUS server project
 */
RCSID("$Id: c943376987d4d3915d6f7962214a5bc791340e17 $")
 
#include <freeradius-devel/util/strerror.h>
#include <freeradius-devel/util/types.h>
#include <freeradius-devel/util/value.h>
 
/** Map data types to names representing those types
 */
fr_table_num_ordered_t const fr_type_table[] = {
        { L("null"),            FR_TYPE_NULL            },
        { L("string"),          FR_TYPE_STRING          },
        { L("octets"),          FR_TYPE_OCTETS          },
 
        { L("ipaddr"),          FR_TYPE_IPV4_ADDR       },
        { L("ipv4addr"),        FR_TYPE_IPV4_ADDR       },
        { L("ipv4prefix"),      FR_TYPE_IPV4_PREFIX     },
        { L("ipv6addr"),        FR_TYPE_IPV6_ADDR       },
        { L("ipv6prefix"),      FR_TYPE_IPV6_PREFIX     },
        { L("ifid"),            FR_TYPE_IFID            },
        { L("combo-ip"),        FR_TYPE_COMBO_IP_ADDR   },
        { L("combo-prefix"),    FR_TYPE_COMBO_IP_PREFIX },
        { L("ether"),           FR_TYPE_ETHERNET        },
 
        { L("bool"),            FR_TYPE_BOOL            },
 
        { L("uint8"),           FR_TYPE_UINT8           },
        { L("uint16"),          FR_TYPE_UINT16          },
        { L("uint32"),          FR_TYPE_UINT32          },
        { L("uint64"),          FR_TYPE_UINT64          },
 
        { L("int8"),            FR_TYPE_INT8            },
        { L("int16"),           FR_TYPE_INT16           },
        { L("int32"),           FR_TYPE_INT32           },
        { L("int64"),           FR_TYPE_INT64           },
 
        { L("float32"),         FR_TYPE_FLOAT32         },
        { L("float64"),         FR_TYPE_FLOAT64         },
 
        { L("date"),            FR_TYPE_DATE            },
        { L("time_delta"),      FR_TYPE_TIME_DELTA      },
 
        { L("size"),            FR_TYPE_SIZE            },
 
        { L("tlv"),             FR_TYPE_TLV             },
        { L("struct"),          FR_TYPE_STRUCT          },
 
        { L("vsa"),             FR_TYPE_VSA             },
        { L("vendor"),          FR_TYPE_VENDOR          },
        { L("group"),           FR_TYPE_GROUP           },
        { L("union"),           FR_TYPE_UNION           },
 
        { L("attribute"),       FR_TYPE_ATTR            },
 
        /*
         *      Alternative names
         */
        { L("cidr"),            FR_TYPE_IPV4_PREFIX     },
        { L("byte"),            FR_TYPE_UINT8           },
        { L("short"),           FR_TYPE_UINT16          },
        { L("integer"),         FR_TYPE_UINT32          },
        { L("integer64"),       FR_TYPE_UINT64          },
        { L("decimal"),         FR_TYPE_FLOAT64         },
        { L("signed"),          FR_TYPE_INT32           }
};
size_t fr_type_table_len = NUM_ELEMENTS(fr_type_table);
 
/** Table of all the direct mappings between types and C types
 *
 * Useful for setting talloc types correctly.
 */
static char const *fr_type_to_c_type[] = {
        [FR_TYPE_STRING]                        = "char *",
        [FR_TYPE_OCTETS]                        = "uint8_t *",
 
        [FR_TYPE_IPV4_ADDR]                     = "fr_ipaddr_t",
        [FR_TYPE_IPV4_PREFIX]                   = "fr_ipaddr_t",
        [FR_TYPE_IPV6_ADDR]                     = "fr_ipaddr_t",
        [FR_TYPE_IPV6_PREFIX]                   = "fr_ipaddr_t",
        [FR_TYPE_COMBO_IP_ADDR]                 = "fr_ipaddr_t",
        [FR_TYPE_COMBO_IP_PREFIX]               = "fr_ipaddr_t",
        [FR_TYPE_IFID]                          = "fr_ifid_t",
        [FR_TYPE_ETHERNET]                      = "fr_ethernet_t",
 
        [FR_TYPE_BOOL]                          = "bool",
        [FR_TYPE_UINT8]                         = "uint8_t",
        [FR_TYPE_UINT16]                        = "uint16_t",
        [FR_TYPE_UINT32]                        = "uint32_t",
        [FR_TYPE_UINT64]                        = "uint64_t",
 
        [FR_TYPE_INT8]                          = "int8_t",
        [FR_TYPE_INT16]                         = "int16_t",
        [FR_TYPE_INT32]                         = "int32_t",
        [FR_TYPE_INT64]                         = "int64_t",
 
        [FR_TYPE_FLOAT32]                       = "float",
        [FR_TYPE_FLOAT64]                       = "double",
 
        [FR_TYPE_DATE]                          = "fr_unix_time_t",
 
        [FR_TYPE_TIME_DELTA]                    = "fr_time_delta_t",
        [FR_TYPE_SIZE]                          = "size_t",
        [FR_TYPE_VALUE_BOX]                     = "fr_value_box_t",
        [FR_TYPE_ATTR]                          = "fr_dict_attr_t *",
        [FR_TYPE_VOID]                          = "void *",
 
        [FR_TYPE_VALUE_BOX_CURSOR]              = "fr_dcursor_t *",
        [FR_TYPE_PAIR_CURSOR]                   = "fr_dcursor_t *",
 
        [FR_TYPE_MAX]                           = 0     //!< Ensure array covers all types.
};
 
/** Table of all the direct mappings between types and C type sizes
 *
 */
static size_t const fr_type_to_c_size[] = {
        [FR_TYPE_STRING]                        = sizeof(char *),
        [FR_TYPE_OCTETS]                        = sizeof(uint8_t *),
 
        [FR_TYPE_IPV4_ADDR]                     = sizeof(fr_ipaddr_t),
        [FR_TYPE_IPV4_PREFIX]                   = sizeof(fr_ipaddr_t),
        [FR_TYPE_IPV6_ADDR]                     = sizeof(fr_ipaddr_t),
        [FR_TYPE_IPV6_PREFIX]                   = sizeof(fr_ipaddr_t),
        [FR_TYPE_COMBO_IP_ADDR]                 = sizeof(fr_ipaddr_t),
        [FR_TYPE_COMBO_IP_PREFIX]               = sizeof(fr_ipaddr_t),
        [FR_TYPE_IFID]                          = sizeof(fr_ifid_t),
        [FR_TYPE_ETHERNET]                      = sizeof(fr_ethernet_t),
 
        [FR_TYPE_BOOL]                          = sizeof(bool),
        [FR_TYPE_UINT8]                         = sizeof(uint8_t),
        [FR_TYPE_UINT16]                        = sizeof(uint16_t),
        [FR_TYPE_UINT32]                        = sizeof(uint32_t),
        [FR_TYPE_UINT64]                        = sizeof(uint64_t),
 
        [FR_TYPE_INT8]                          = sizeof(int8_t),
        [FR_TYPE_INT16]                         = sizeof(int16_t),
        [FR_TYPE_INT32]                         = sizeof(int32_t),
        [FR_TYPE_INT64]                         = sizeof(int64_t),
 
        [FR_TYPE_FLOAT32]                       = sizeof(float),
        [FR_TYPE_FLOAT64]                       = sizeof(double),
 
        [FR_TYPE_DATE]                          = sizeof(fr_unix_time_t),
 
        [FR_TYPE_TIME_DELTA]                    = sizeof(fr_time_delta_t),
        [FR_TYPE_SIZE]                          = sizeof(size_t),
        [FR_TYPE_VALUE_BOX]                     = sizeof(fr_value_box_t),
        [FR_TYPE_ATTR]                          = sizeof(fr_dict_attr_t *),
        [FR_TYPE_VOID]                          = sizeof(void *),
 
        [FR_TYPE_VALUE_BOX_CURSOR]              = sizeof(void *),
        [FR_TYPE_PAIR_CURSOR]                   = sizeof(void *),
 
        [FR_TYPE_MAX]                           = 0     //!< Ensure array covers all types.
};
 
#define ARRAY_BEG(_type)        { [_type] = true,
#define ARRAY_MID(_type)        [_type] = true,
#define ARRAY_END(_type)        [_type] = true }
 
bool const fr_type_integer_except_bool[FR_TYPE_MAX + 1] = FR_TYPE_INTEGER_EXCEPT_BOOL_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
bool const fr_type_integer[FR_TYPE_MAX + 1] = FR_TYPE_INTEGER_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
bool const fr_type_numeric[FR_TYPE_MAX + 1] = FR_TYPE_NUMERIC_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
bool const fr_type_signed[FR_TYPE_MAX + 1] = FR_TYPE_SIGNED_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
 
bool const fr_type_ip[FR_TYPE_MAX + 1] = FR_TYPE_IP_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
 
bool const fr_type_fixed_size[FR_TYPE_MAX + 1] = FR_TYPE_FIXED_SIZE_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
bool const fr_type_variable_size[FR_TYPE_MAX + 1] = FR_TYPE_VARIABLE_SIZE_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
bool const fr_type_quoted[FR_TYPE_MAX + 1] = FR_TYPE_QUOTED_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
 
bool const fr_type_structural_except_vsa[FR_TYPE_MAX + 1] = FR_TYPE_STRUCTURAL_EXCEPT_VSA_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
bool const fr_type_structural[FR_TYPE_MAX + 1] = FR_TYPE_STRUCTURAL_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
bool const fr_type_leaf[FR_TYPE_MAX + 1] = FR_TYPE_LEAF_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
bool const fr_type_non_leaf[FR_TYPE_MAX + 1] = FR_TYPE_NON_LEAF_DEF(ARRAY_BEG, ARRAY_MID, ARRAY_END);
 
#define O(_x) [FR_TYPE_ ## _x] = true
 
/*
 *      Can we promote [src][dst] -> dst
 *              dst is not octets / string
 *              src and dst are both FR_TYPE_VALUE
 */
static const bool type_cast_table[FR_TYPE_MAX][FR_TYPE_MAX] = {
        [FR_TYPE_IPV4_ADDR] = {
                O(IPV4_PREFIX),
                O(IPV6_ADDR),
                O(IPV6_PREFIX),
                O(COMBO_IP_ADDR),
                O(COMBO_IP_PREFIX),
                O(UINT32),              /* ipv4 addresses are uint32 */
        },
        [FR_TYPE_IPV4_PREFIX] = {
                O(IPV4_ADDR),           /* if the prefix is /32 */
                O(IPV6_ADDR),
                O(IPV6_PREFIX),
                O(COMBO_IP_ADDR),
                O(COMBO_IP_PREFIX)
        },
        [FR_TYPE_IPV6_ADDR] = {
                O(IPV6_PREFIX),
                O(COMBO_IP_ADDR),
                O(COMBO_IP_PREFIX)
        },
        [FR_TYPE_IPV6_PREFIX] = {
                O(IPV6_ADDR),           /* if the prefix is /128 */
                O(COMBO_IP_ADDR),
                O(COMBO_IP_PREFIX)
        },
        [FR_TYPE_COMBO_IP_ADDR] = {
                O(IPV4_ADDR),
                O(IPV4_PREFIX),
                O(IPV6_ADDR),
                O(IPV6_PREFIX),
                O(COMBO_IP_PREFIX)
        },
        [FR_TYPE_COMBO_IP_PREFIX] = {
                O(IPV4_ADDR),
                O(IPV4_PREFIX),
                O(IPV6_ADDR),
                O(IPV6_PREFIX),
                O(COMBO_IP_ADDR)        /* if the prefix is /128 or /32 */
        },
 
        [FR_TYPE_ETHERNET] = {
                O(UINT64),
        },
 
        [FR_TYPE_UINT64] = {
                O(ETHERNET),
        },
 
        [FR_TYPE_DATE] = {      /* in 2021, dates always have values 2^31 or more */
                O(UINT32),
                O(UINT64),
                O(INT32),
                O(INT64),
                O(SIZE),
                O(FLOAT32),
                O(FLOAT64),
                O(TIME_DELTA),
        },
 
        [FR_TYPE_TIME_DELTA] = {
                O(DATE),
        },
 
        [FR_TYPE_UINT32] = {
                O(IPV4_ADDR),
        },
 
};
 
/*
 *      This is different from FR_TYPE_NUMERIC, largely in that it
 *      doesn't include FR_TYPE_DATE.  Because we know that dates
 *      always have values 2^31 or greater, so casts exclude some of
 *      the smaller integer types.
 */
static const bool type_is_number[FR_TYPE_MAX] = {
        O(BOOL),  O(SIZE),   O(FLOAT32), O(FLOAT64),
        O(UINT8), O(UINT16), O(UINT32), O(UINT64),
        O(INT8),  O(INT16),  O(INT32),  O(INT64),
        O(TIME_DELTA),
};
 
/** Return if we're allowed to cast the types.
 *
 * @param dst   the destination type we wish to cast to
 * @param src   the source type we wish to cast to
 *
 */
bool fr_type_cast(fr_type_t dst, fr_type_t src)
{
        /*
         *      Invalid casts.
         */
        switch (dst) {
        case FR_TYPE_NON_LEAF:
                return false;
 
        default:
                break;
        }
 
        switch (src) {
        case FR_TYPE_NON_LEAF:
                return false;
 
        default:
                break;
        }
 
        if (src == dst) return true;
 
        /*
         *      Anything can be converted to octets or strings.
         */
        if (dst == FR_TYPE_OCTETS) return true;
        if (dst == FR_TYPE_STRING) return true;
 
        /*
         *      Strings and octets can be converted to anything.  We
         *      do run-time checks on the values to see if they fit.
         */
        if (src == FR_TYPE_OCTETS) return true;
        if (src == FR_TYPE_STRING) return true;
 
        /*
         *      Any integer-style thing can be cast to any other
         *      integer-style thing.  Mostly.  We do run-time checks
         *      on values to see if they fit.
         */
        if (type_is_number[src] && type_is_number[dst]) {
                return true;
        }
 
        /*
         *      That takes care of the simple cases.  :( Now to the
         *      complex ones.  Instead of masses of if / then / else,
         *      we just use a lookup table.
         */
        return type_cast_table[src][dst];
}
 
#undef O
#define O(_x) [FR_TYPE_ ## _x] = FR_TYPE_ ## _x
 
/** promote (a,b) -> a or b
 *              a/b are not octets / string
 *              a and b are both FR_TYPE_VALUE
 *
 *  Note that this table can return a type which is _not_ a or b.
 *
 *  Many lookups of table[a][b] will return b.  Some will return a.
 *  Others will return a type which is compatible with both a and b.
 */
static fr_type_t type_promote_table[FR_TYPE_MAX][FR_TYPE_MAX] = {
        [FR_TYPE_IPV4_ADDR] = {
                O(IPV4_PREFIX),
                O(IPV6_ADDR),
                O(IPV6_PREFIX),
                [FR_TYPE_UINT32] = FR_TYPE_IPV4_ADDR,
        },
 
        [FR_TYPE_IPV4_PREFIX] = {
                [FR_TYPE_IPV4_ADDR] = FR_TYPE_IPV4_PREFIX,
                O(IPV4_PREFIX),
                [FR_TYPE_IPV6_ADDR] = FR_TYPE_IPV6_PREFIX,
                O(IPV6_PREFIX),
        },
 
        [FR_TYPE_IPV6_ADDR] = {
                O(IPV6_PREFIX),
        },
 
        [FR_TYPE_IPV6_PREFIX] = {
                [FR_TYPE_IPV6_ADDR] = FR_TYPE_IPV6_PREFIX,
        },
 
        /* unsigned integers */
 
        [FR_TYPE_BOOL] = {
                O(UINT8),
                O(UINT16),
                O(UINT32),
                O(UINT64),
                O(INT8),
                O(INT16),
                O(INT32),
                O(INT64),
                O(SIZE),
                O(FLOAT32),
                O(FLOAT64),
                O(TIME_DELTA),
        },
 
        [FR_TYPE_UINT8] = {
                [FR_TYPE_BOOL] = FR_TYPE_UINT8,
                O(UINT16),
                O(UINT32),
                O(UINT64),
                [FR_TYPE_INT8] = FR_TYPE_UINT8,
                O(INT16),
                O(INT32),
                O(INT64),
                O(SIZE),
                O(FLOAT32),
                O(FLOAT64),
                O(TIME_DELTA),
        },
 
        [FR_TYPE_UINT16] = {
                [FR_TYPE_BOOL] = FR_TYPE_UINT16,
                [FR_TYPE_UINT8] = FR_TYPE_UINT16,
                O(UINT32),
                O(UINT64),
                [FR_TYPE_INT16] = FR_TYPE_UINT16,
                O(INT32),
                O(INT64),
                O(SIZE),
                O(FLOAT32),
                O(FLOAT64),
                O(TIME_DELTA),
        },
 
        [FR_TYPE_UINT32] = {
                [FR_TYPE_BOOL] = FR_TYPE_UINT32,
                O(IPV4_ADDR),
                [FR_TYPE_UINT8] = FR_TYPE_UINT32,
                [FR_TYPE_UINT16] = FR_TYPE_UINT32,
                O(UINT64),
                [FR_TYPE_INT32] = FR_TYPE_UINT32,
                O(INT64),
                O(SIZE),
                O(FLOAT32),
                O(FLOAT64),
                O(TIME_DELTA),
                O(DATE),
        },
 
        [FR_TYPE_UINT64] = {
                [FR_TYPE_BOOL] = FR_TYPE_UINT64,
                [FR_TYPE_UINT8] = FR_TYPE_UINT64,
                [FR_TYPE_UINT16] = FR_TYPE_UINT64,
                [FR_TYPE_UINT32] = FR_TYPE_UINT64,
 
                [FR_TYPE_INT8] = FR_TYPE_UINT64,
                [FR_TYPE_INT16] = FR_TYPE_UINT64,
                [FR_TYPE_INT32] = FR_TYPE_UINT64,
                [FR_TYPE_INT64] = FR_TYPE_UINT64,
                O(SIZE),
                [FR_TYPE_FLOAT32] = FR_TYPE_FLOAT64,
                O(FLOAT64),
                O(TIME_DELTA),
                O(DATE),
        },
 
        /* signed integers */
        [FR_TYPE_INT8] = {
                [FR_TYPE_BOOL] = FR_TYPE_INT8,
                O(UINT8),
                O(UINT16),
                O(UINT32),
                O(UINT64),
                O(INT16),
                O(INT32),
                O(INT64),
                O(SIZE),
                O(FLOAT32),
                O(FLOAT64),
                O(TIME_DELTA),
        },
 
        [FR_TYPE_INT16] = {
                [FR_TYPE_BOOL] = FR_TYPE_INT16,
                [FR_TYPE_UINT8] = FR_TYPE_INT16,
                O(UINT16),
                O(UINT32),
                O(UINT64),
                [FR_TYPE_INT8] = FR_TYPE_INT16,
                O(INT32),
                O(INT64),
                O(SIZE),
                O(FLOAT32),
                O(FLOAT64),
                O(TIME_DELTA),
        },
 
        [FR_TYPE_INT32] = {
                [FR_TYPE_BOOL] = FR_TYPE_INT32,
                [FR_TYPE_UINT8] = FR_TYPE_INT32,
                [FR_TYPE_UINT16] = FR_TYPE_INT32,
                O(UINT32),
                O(UINT64),
                [FR_TYPE_INT8] = FR_TYPE_INT32,
                [FR_TYPE_INT16] = FR_TYPE_INT32,
                O(INT64),
                O(SIZE),
                O(FLOAT32),
                O(FLOAT64),
                O(TIME_DELTA),
                O(DATE),
        },
 
        [FR_TYPE_INT64] = {
                [FR_TYPE_UINT8] = FR_TYPE_UINT64,
                [FR_TYPE_UINT16] = FR_TYPE_UINT64,
                [FR_TYPE_UINT32] = FR_TYPE_UINT64,
                O(UINT64),
                O(SIZE),
                [FR_TYPE_INT8] = FR_TYPE_UINT64,
                [FR_TYPE_INT16] = FR_TYPE_UINT64,
                [FR_TYPE_INT32] = FR_TYPE_UINT64,
                [FR_TYPE_FLOAT32] = FR_TYPE_FLOAT64,
                O(FLOAT64),
                O(TIME_DELTA),
                O(DATE),
        },
 
        [FR_TYPE_TIME_DELTA] = {
                [FR_TYPE_BOOL] = FR_TYPE_TIME_DELTA,
                [FR_TYPE_UINT8] = FR_TYPE_TIME_DELTA,
                [FR_TYPE_UINT16] = FR_TYPE_TIME_DELTA,
                [FR_TYPE_UINT32] = FR_TYPE_TIME_DELTA,
                [FR_TYPE_UINT64] = FR_TYPE_TIME_DELTA,
                [FR_TYPE_SIZE] = FR_TYPE_TIME_DELTA,
 
                [FR_TYPE_INT8] = FR_TYPE_TIME_DELTA,
                [FR_TYPE_INT16] = FR_TYPE_TIME_DELTA,
                [FR_TYPE_INT32] = FR_TYPE_TIME_DELTA,
                [FR_TYPE_INT64] = FR_TYPE_TIME_DELTA,
 
                [FR_TYPE_FLOAT32] = FR_TYPE_TIME_DELTA,
                [FR_TYPE_FLOAT64] = FR_TYPE_TIME_DELTA,
                [FR_TYPE_DATE] = FR_TYPE_TIME_DELTA,
        },
 
        [FR_TYPE_DATE] = {
                [FR_TYPE_UINT32] = FR_TYPE_DATE,
                [FR_TYPE_UINT64] = FR_TYPE_DATE,
                [FR_TYPE_SIZE] = FR_TYPE_DATE,
 
                [FR_TYPE_INT32] = FR_TYPE_DATE,
                [FR_TYPE_INT64] = FR_TYPE_DATE,
 
                [FR_TYPE_FLOAT32] = FR_TYPE_DATE,
                [FR_TYPE_FLOAT64] = FR_TYPE_DATE,
                O(TIME_DELTA),
        },
 
        [FR_TYPE_SIZE] = {
                [FR_TYPE_BOOL] = FR_TYPE_SIZE,
                [FR_TYPE_UINT8] = FR_TYPE_SIZE,
                [FR_TYPE_UINT16] = FR_TYPE_SIZE,
                [FR_TYPE_UINT32] = FR_TYPE_SIZE,
                [FR_TYPE_UINT64] = FR_TYPE_SIZE,
                [FR_TYPE_INT8] = FR_TYPE_SIZE,
                [FR_TYPE_INT16] = FR_TYPE_SIZE,
                [FR_TYPE_INT32] = FR_TYPE_SIZE,
                [FR_TYPE_INT64] = FR_TYPE_SIZE,
                [FR_TYPE_FLOAT32] = FR_TYPE_FLOAT64,
                O(FLOAT64),
                [FR_TYPE_TIME_DELTA] = FR_TYPE_SIZE,
                O(DATE),
        }
};
 
/** Return the promoted type
 *
 *  We presume that the two types are compatible, as checked by
 *  calling fr_type_cast().  The main difference here is that the two
 *  types don't have any src / dst relationship.  Instead, we just
 *  pick one which best suits any value-box comparisons
 *
 *  Note that this function can return a type which is _not_ a or b.
 *
 * @param a     type one
 * @param b     type two
 * @return      the promoted type
 */
fr_type_t fr_type_promote(fr_type_t a, fr_type_t b)
{
        if (!fr_type_is_leaf(a) || !fr_type_is_leaf(b)) return FR_TYPE_NULL;
 
        if (a == b) return a;
 
        /*
         *      string / octets and "type", the un-typed data gets cast to
         *      "type".
         *
         *      We prefer to cast raw data to real types.  We also
         *      prefer to _parse_ strings, and do the type checking on
         *      the real types.  That way we have things like:  "000" == 0
         */
        if (a == FR_TYPE_OCTETS) return b;
        if (b == FR_TYPE_OCTETS) return a;
 
        /*
         *      Check for string after octets, because we want to cast
         *      octets to string, and not vice versa.
         */
        if (a == FR_TYPE_STRING) return b;
        if (b == FR_TYPE_STRING) return a;
 
        /*
         *      Otherwise bad things happen. :(
         */
        if (unlikely(type_promote_table[a][b] != type_promote_table[b][a])) {
                fr_strerror_printf("Inverse type mapping inconsistent for a = %s, b = %s",
                                   fr_type_to_str(a),
                                   fr_type_to_str(b));
 
                return FR_TYPE_NULL;
        }
 
        if (unlikely(type_promote_table[a][b] == FR_TYPE_NULL)) {
                fr_strerror_printf("No type promotions for a = %s, b = %s",
                                   fr_type_to_str(a),
                                   fr_type_to_str(b));
                return FR_TYPE_NULL;
        }
 
        /*
         *      That takes care of the simple cases.  :( Now to the
         *      complex ones.  Instead of masses of if / then / else,
         *      we just use a lookup table.
         */
        return type_promote_table[a][b];
}
 
/** Allocate an array of a given type
 *
 * @param[in] ctx       to allocate array in.
 * @param[in] type      array to allocate.
 * @param[in] count     The number of elements to allocate.
 * @return
 *      - NULL on error.
 *      - A new talloc array.
 */
void **fr_type_array_alloc(TALLOC_CTX *ctx, fr_type_t type, size_t count)
{
        char const *c_type;
 
        c_type = fr_type_to_c_type[type];
        if (c_type == NULL) {
                fr_strerror_printf("Type %s does not have a C type equivalent", fr_type_to_str(type));
                return NULL;
        }
 
        return _talloc_zero_array(ctx, fr_type_to_c_size[type], count, c_type);
 }