/src/freeradius-server/src/freeradius-devel/util/dbuff.h

Source (jump to first uncovered line)
#pragma once
/*
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program 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 General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */

/** A generic data buffer structure for encoding and decoding
 *
 * Because doing manual length checks is error prone and a waste of everyone's time.
 *
 * @file src/lib/util/dbuff.h
 *
 * @copyright 2020 Arran Cudbard-Bell <a.cudbardb@freeradius.org>
 */
RCSIDH(dbuff_h, "$Id: 2f9e02d673e5bfb71e69e70c7db912747ad10556 $")

#  ifdef __cplusplus
extern "C" {
#  endif

#include <errno.h>
#include <freeradius-devel/missing.h>
#include <freeradius-devel/util/debug.h>
#include <freeradius-devel/util/nbo.h>
#include <limits.h>
#include <stdbool.h>
#include <stdint.h>
#include <sys/types.h>

/** A dbuff
 *
 * dbuffs wrap an underlying buffer, maintaining 'start', 'current', and 'end'
 * position pointers.
 *
 * dbuffs also contain information on if and how the underlying buffer can be
 * extended.
 *
 * For encoding extending means reallocing the underlying buffer so that there's
 * addition space to write data to.
 *
 * For stream decoding extending means shifting out existing data and refilling
 * the underlying buffer from a data source.
 *
 * dbuffs are intended to be organised into hierarchies, with one dbuff per stack
 * frame, initialised from a parent in a higher stack frame.
 *
 * Each time a dbuff is copied (using one of the provided FR_DBUFF_BIND_CURRENT_* macros),
 * the copy's 'start' position is updated to be the 'current' position of its
 * parent.  This ensures length macros report only spaced used/available in the
 * new dbuff and not its parent.
 * Other copy macros may move the 'end' position, to artificially limit the
 * amount of data available.
 */
typedef struct fr_dbuff_s fr_dbuff_t;

/** A position marker associated with a dbuff
 *
 * Markers are used whenever the caller needs to access part of the underlying
 * buffer other than the 'start', 'current' or 'end' positions described by
 * a #fr_dbuff_t.
 *
 * Markers are needed because if a #fr_dbuff_t is extended, pointers into the
 * underlying buffer may be invalidated by a realloc or memmove.
 *
 * Markers are intended to be allocated on the stack and associated with a
 * stack-frame-local `fr_dbuff_t`.  Using a stack-frame-local dbuff ensures
 * markers are automatically released when the stack frame is popped so that
 * markers are not leaked.
 */
typedef struct fr_dbuff_marker_s fr_dbuff_marker_t;

/** dbuff extension callback
 *
 * This callback is used to extend the underlying buffer.
 *
 * - Where the buffer is being used to aggregate data, this callback will
 * usually call realloc to extend the buffer.
 *
 * - Where the buffer is being used for stream decoding, this callback will
 * usually shift the existing data in the buffer to the left, and read in more
 * data from the stream.
 *
 * After performing an operation on the underlying buffer, this callback should
 * call #fr_dbuff_update to fix position pointers in the current dbuff and its
 * parents and markers.
 *
 * Generally the caller will request the minimum amount the buffer should be
 * extended by.  This callback may choose to ignore the request and extend the
 * buffer by more than the requested amount.
 *
 * @param[in] dbuff   to extend.
 * @param[in] req_extension How much the caller wants to extend the buffer
 *        by.
 * @return How much the buffer was extended by.
 * @see fr_dbuff_update
 */
typedef size_t(*fr_dbuff_extend_t)(fr_dbuff_t *dbuff, size_t req_extension);

/** A position marker associated with a dbuff
 * @private
 */
struct fr_dbuff_marker_s {
  /** @private
   */
  union {
    uint8_t const *p_i;     //!< Immutable position pointer.
    uint8_t *p;       //!< Mutable position pointer.
  };
  fr_dbuff_marker_t *next;    //!< Next marker in the list.
  fr_dbuff_t    *parent;  //!< Owner of the marker.
};

#define FR_DBUFF_ADV_PARENT_CURRENT 0x01    //!< Advance current position of parent.
              //!< Useful for nested encoders/decoders.
#define FR_DBUFF_ADV_PARENT_END   0x02    //!< Advance end pointer of parent.
              ///< Useful for producer/consumer

/** A dbuff
 * @private
 */
struct fr_dbuff_s {
  /** @private
   */
  union {
    uint8_t const *buff_i;      //!< Immutable 'buffer' pointer.
    uint8_t *buff;        //!< Mutable 'buffer' pointer.
  };

  /** @private
   */
  union {
    uint8_t const *start_i;     //!< Immutable 'start' pointer.
    uint8_t *start;       //!< Mutable 'start' pointer.
  };

  /** @private
   */
  union {
    uint8_t const *end_i;     //!< Immutable 'end' pointer.
    uint8_t *end;       //!< Mutable 'end' pointer.
  };

  /** @private
   */
  union {
    uint8_t const *p_i;     //!< Immutable 'current' pointer.
    uint8_t *p;       //!< Mutable 'current' pointer.
  };

  uint8_t     is_const:1;   //!< The buffer this dbuff wraps is const.
  uint8_t     adv_parent:2; //!< Whether we advance the parent
            ///< of this dbuff.

  size_t      shifted;  //!< How many bytes this sbuff has been
            ///< shifted since its creation.

  fr_dbuff_extend_t extend;   //!< Function to re-populate or extend
            ///< the buffer.
  void      *uctx;    //!< Extend uctx data.

  fr_dbuff_t    *parent;  //!< The #fr_dbuff_t this #fr_dbuff_t was
            ///< created from.
            ///< This will usually be the #fr_dbuff_t
            ///< passed into a function.

  fr_dbuff_marker_t *m;   //!< Pointers to update if the underlying
            ///< buffer changes.
};

/** Generic wrapper macro to return if there's insufficient memory to satisfy the request on the dbuff
 *
 */
#define FR_DBUFF_RETURN(_func, ...) \
do { \
  ssize_t _slen = _func(__VA_ARGS__ ); \
  if (_slen < 0) return _slen; \
} while (0)

/** @name Initialisers
 * @{
 */

/** @cond */

/** Copy another fr_dbuff_t, modifying it.
 *
 * @private
 */
#define _FR_DBUFF(_dbuff_or_marker, _start, _adv_parent) \
((fr_dbuff_t){ \
  .buff   = fr_dbuff_buff(_dbuff_or_marker), \
  .start    = (_start), \
  .end    = fr_dbuff_end(_dbuff_or_marker), \
  .p    = fr_dbuff_current(_dbuff_or_marker), \
  .is_const   = fr_dbuff_ptr(_dbuff_or_marker)->is_const, \
  .adv_parent   = (_adv_parent), \
  .shifted  = fr_dbuff_ptr(_dbuff_or_marker)->shifted, \
  .extend   = fr_dbuff_ptr(_dbuff_or_marker)->extend, \
  .uctx   = fr_dbuff_ptr(_dbuff_or_marker)->uctx, \
  .parent   = fr_dbuff_ptr(_dbuff_or_marker) \
})
/* @endcond */

/** Create a new dbuff pointing to the same underlying buffer
 *
 * - Parent will _NOT_ be advanced by operations on its child.
 * - Child will have its `start` pointer set to the `p` pointer of the parent.
 *
 * @param[in] _dbuff_or_marker  to make an ephemeral copy of.
 */
#define FR_DBUFF(_dbuff_or_marker) _FR_DBUFF(_dbuff_or_marker, fr_dbuff_current(_dbuff_or_marker), 0x00)

/** Create a new dbuff pointing to the same underlying buffer
 *
 * - Parent will _NOT_ be advanced by operations on its child.
 * - Child will have its `start` pointer set to the `start` pointer of the parent.
 *
 * @param[in] _dbuff_or_marker  to make an ephemeral copy of.
 */
#define FR_DBUFF_ABS(_dbuff_or_marker) _FR_DBUFF(_dbuff_or_marker, fr_dbuff_start(_dbuff_or_marker), 0x00)

/** Create a new dbuff pointing to the same underlying buffer
 *
 * - Parent `p` pointer will be advanced with child's `p` pointer.
 * - Child will have its `start` pointer set to the `p` pointer of the parent.
 *
 * @param[in] _dbuff_or_marker  to make an ephemeral copy of.
 */
#define FR_DBUFF_BIND_CURRENT(_dbuff_or_marker) _FR_DBUFF(_dbuff_or_marker, fr_dbuff_current(_dbuff_or_marker), FR_DBUFF_ADV_PARENT_CURRENT)

/** Create a new dbuff pointing to the same underlying buffer
 *
 * - Parent `p` pointer will be advanced with child's `p` pointer.
 * - Child will have its `start` pointer set to the `start` pointer of the parent.
 *
 * @param[in] _dbuff_or_marker  to make an ephemeral copy of.
 */
#define FR_DBUFF_BIND_CURRENT_ABS(_dbuff_or_marker) FR_DBUFF_ABS(_dbuff_or_marker, fr_dbuff_start(_dbuff_or_marker), FR_DBUFF_ADV_PARENT_CURRENT)

/** Create a new dbuff pointing to the same underlying buffer
 *
 * This is used to create the producer of a producer/consumer pairs of dbuffs.
 *
 * - Parent `end` pointer will be advanced with child's `p` pointer.
 * - Child will have its `start` pointer set to the `start` pointer of the parent.
 *
 * @param[in] _dbuff_or_marker  to make an ephemeral copy of.
 */
#define FR_DBUFF_BIND_END_ABS(_dbuff_or_marker) _FR_DBUFF(_dbuff_or_marker, fr_dbuff_start(_dbuff_or_marker), FR_DBUFF_ADV_PARENT_END)

/** @cond */
/** Limit available bytes in the dbuff to _max when passing it to another function
 *
 * @private
 */
#define _FR_DBUFF_MAX(_dbuff_or_marker, _max, _adv_parent) \
((fr_dbuff_t){ \
  .buff   = fr_dbuff_buff(_dbuff_or_marker), \
  .start    = fr_dbuff_current(_dbuff_or_marker), \
  .end    = (((fr_dbuff_end(_dbuff_or_marker) - (_max) < fr_dbuff_current(_dbuff_or_marker))) ? fr_dbuff_end(_dbuff_or_marker) : (fr_dbuff_current(_dbuff_or_marker) + (_max))), \
  .p    = fr_dbuff_current(_dbuff_or_marker), \
  .is_const = fr_dbuff_ptr(_dbuff_or_marker)->is_const, \
  .adv_parent = _adv_parent, \
  .shifted  = fr_dbuff_ptr(_dbuff_or_marker)->shifted, \
  .extend   = NULL, \
  .uctx   = NULL, \
  .parent   = fr_dbuff_ptr(_dbuff_or_marker) \
})
/* @endcond */

/** Limit the maximum number of bytes available in the dbuff when passing it to another function
 *
 @code{.c}
 fr_dbuff_t tlv = FR_DBUFF_MAX(dbuff, UINT8_MAX);

 if (my_child_encoder(&tlv, vp) < 0) return -1;

 return fr_dbuff_advance(dbuff, fr_dbuff_used(tlv))
 @endcode
 *
 * @note Do not use to re-initialise the contents of _dbuff, i.e. to
 *  permanently shrink the exiting dbuff. The parent pointer will loop.
 *
 * @note Do not modify the "child" dbuff directly.  Use the functions
 *   supplied as part of this API.
 *
 * @param[in] _dbuff_or_marker  to reserve bytes in.
 * @param[in] _max    The maximum number of bytes the caller is allowed to write to.
 */
#define FR_DBUFF_MAX(_dbuff_or_marker,  _max) _FR_DBUFF_MAX(_dbuff_or_marker, _max, 0x00)

/** Limit the maximum number of bytes available in the dbuff when passing it to another function
 *
 @code{.c}
 my_child_encoder(&FR_DBUFF_MAX_BIND_CURRENT(dbuff, 253), vp);
 @endcode
 *
 * @note Do not use to re-initialise the contents of _dbuff, i.e. to
 *  permanently shrink the exiting dbuff. The parent pointer will loop.
 *
 * @note Do not modify the "child" dbuff directly.  Use the functions
 *   supplied as part of this API.
 *
 * @param[in] _dbuff_or_marker  to reserve bytes in.
 * @param[in] _max    The maximum number of bytes the caller is allowed to write to.
 */
#define FR_DBUFF_MAX_BIND_CURRENT(_dbuff_or_marker,  _max) _FR_DBUFF_MAX(_dbuff_or_marker, _max, FR_DBUFF_ADV_PARENT_CURRENT)

/*
 *  GCC is stupid and will warn about output variables
 *  being unnitialised, even if they're not dereferenced.
 */
#if defined(__GNUC__) && __GNUC__ >= 11
DIAG_OFF(maybe-uninitialized)
#endif
/** Does the actual work of initialising a dbuff
 * @private
 */
static inline
#ifndef __COVERITY__
CC_HINT(nonnull)
#endif
void _fr_dbuff_init(fr_dbuff_t *out, uint8_t const *start, uint8_t const *end, bool is_const)
{
  if (unlikely(end < start)) end = start; /* Could be an assert? */

  *out = (fr_dbuff_t){
    .buff_i = start,
    .start_i = start,
    .p_i = start,
    .end_i = end,
    .is_const = is_const
  };
}

/** Initialise an dbuff for encoding or decoding
 *
 * @param[out] _out   Pointer to buffer to parse
 * @param[in] _start    Start of the buffer to parse.
 * @param[in] _len_or_end Either an end pointer or the length
 *        of the buffer we're deconding.
 */
#define fr_dbuff_init(_out, _start, _len_or_end) \
_fr_dbuff_init(_out, \
         (uint8_t const *)(_start), \
         _Generic((_len_or_end), \
      size_t    : (uint8_t const *)(_start) + (size_t)(_len_or_end), \
      long    : (uint8_t const *)(_start) + (size_t)(_len_or_end), \
      int   : (uint8_t const *)(_start) + (size_t)(_len_or_end), \
      unsigned int  : (uint8_t const *)(_start) + (size_t)(_len_or_end), \
      uint8_t * : (uint8_t const *)(_len_or_end), \
      uint8_t const * : (uint8_t const *)(_len_or_end), \
      char *    : (uint8_t const *)(_len_or_end), \
      char const *  : (uint8_t const *)(_len_or_end) \
         ), \
         _Generic((_start), \
      uint8_t * : false, \
      uint8_t const * : true, \
      char *    : false, \
      char const *  : true \
         ))
#if defined(__GNUC__) && __GNUC__ >= 11
DIAG_ON(maybe-uninitialized)
#endif

size_t  _fr_dbuff_extend_talloc(fr_dbuff_t *dbuff, size_t extension);

int fr_dbuff_trim_talloc(fr_dbuff_t *dbuff, size_t len);

int fr_dbuff_reset_talloc(fr_dbuff_t *dbuff);

/** Talloc extension structure use by #fr_dbuff_init_talloc
 * @private
 *
 * Holds the data necessary for creating dynamically
 * extensible buffers.
 */
typedef struct {
  TALLOC_CTX    *ctx;     //!< Context to alloc new buffers in.
  size_t      init;     //!< How much to allocate initially.
  size_t      max;      //!< Maximum size of the buffer.
} fr_dbuff_uctx_talloc_t;

/** Initialise a special dbuff which automatically extends as additional data is written
 *
 * @param[in] ctx to allocate buffer in.
 * @param[out] dbuff  to initialise.
 * @param[out] tctx to initialise.  Must have a lifetime >= to the dbuff.
 * @param[in] init  The length of the initial buffer.
 * @param[in] max The maximum length of the buffer.
 * @return
 *  - The passed dbuff on success.
 *  - NULL on failure.
 */
static inline fr_dbuff_t *fr_dbuff_init_talloc(TALLOC_CTX *ctx,
                 fr_dbuff_t *dbuff, fr_dbuff_uctx_talloc_t *tctx,
                 size_t init, size_t max)
{
  uint8_t *buff;

  *tctx = (fr_dbuff_uctx_talloc_t){
    .ctx = ctx,
    .init = init,
    .max = max
  };

  /*
   *  Allocate the initial buffer
   *
   *  We always allocate a buffer so we don't trigger ubsan
   *  errors by performing arithmetic on NULL pointers.
   *
   *  Note that unlike sbuffs, we don't need space for a trailing '\0'.
   */
  buff = talloc_zero_array(ctx, uint8_t, init);
  if (!buff) {
    fr_strerror_printf("Failed allocating buffer of %zu bytes", init);
    memset(dbuff, 0, sizeof(*dbuff)); /* clang scan */
    return NULL;
  }

  *dbuff = (fr_dbuff_t){
    .buff = buff,
    .start = buff,
    .p = buff,
    .end = buff + init,
    .extend = _fr_dbuff_extend_talloc,
    .uctx = tctx
  };

  return dbuff;
}

/** Free the talloc buffer associated with a dbuff
 *
 */
static inline void fr_dbuff_free_talloc(fr_dbuff_t *dbuff)
{
  TALLOC_FREE(dbuff->buff);
}

size_t  _fr_dbuff_extend_fd(fr_dbuff_t *dbuff, size_t extension);

/** File sbuff extension structure use by #fr_dbuff_init_fd
 * @private
 *
 * Holds the data necessary for creating dynamically
 * extensible file buffers.
 */
typedef struct {
  int     fd;     //!< fd of file we're reading from.
  uint8_t     *buff_end;    //!< The true end of the buffer.
  size_t      max;      //!< Maximum number of bytes to read.
} fr_dbuff_uctx_fd_t;


/** Initialise a special dbuff which automatically reads in more data as the buffer is exhausted
 *
 * @param[out] dbuff  to initialise.
 * @param[out] fctx to initialise.  Must have a lifetime >= to the dbuff.
 * @param[in] buff  Temporary buffer to use for storing file contents.
 * @param[in] len Length of the temporary buffer.
 * @param[in] fd  descriptor of an open file to read from.
 * @param[in] max The maximum length of data to read from the file.
 * @return
 *  - The passed dbuff on success.
 *  - NULL on failure.
 */
static inline fr_dbuff_t *fr_dbuff_init_fd(fr_dbuff_t *dbuff, fr_dbuff_uctx_fd_t *fctx,
               uint8_t *buff, size_t len, int fd, size_t max)
{
  *fctx = (fr_dbuff_uctx_fd_t){
    .fd = fd,
    .max = max,
    .buff_end = buff + len    //!< Store the real end
  };

  *dbuff = (fr_dbuff_t){
    .buff = buff,
    .start = buff,
    .p = buff,
    .end = buff,      //!< Starts with 0 bytes available
    .extend = _fr_dbuff_extend_fd,
    .uctx = fctx
  };

  return dbuff;
}

/** Creates a compound literal to pass into functions which accept a dbuff
 *
 * @note The return value of the function should be used to determine how much
 *   data was written to the buffer.
 *
 * @param[in] _start    of the buffer.
 * @param[in] _len_or_end Length of the buffer or the end pointer.
 */
#define FR_DBUFF_TMP(_start, _len_or_end) \
(fr_dbuff_t){ \
  .buff_i   = (uint8_t const *)(_start), \
  .start_i  = (uint8_t const *)(_start), \
  .end_i    = _Generic((_len_or_end), \
        size_t    : (uint8_t const *)(_start) + (size_t)(_len_or_end), \
        long    : (uint8_t const *)(_start) + (size_t)(_len_or_end), \
        int   : (uint8_t const *)(_start) + (size_t)(_len_or_end), \
        unsigned int  : (uint8_t const *)(_start) + (size_t)(_len_or_end), \
        uint8_t * : (uint8_t const *)(_len_or_end), \
        uint8_t const * : (uint8_t const *)(_len_or_end), \
        char *    : (uint8_t const *)(_len_or_end), \
        char const *  : (uint8_t const *)(_len_or_end) \
      ), \
  .p_i    = _start, \
  .is_const = _Generic((_start), \
        uint8_t * : false, \
        uint8_t const * : true, \
        char *    : false, \
        char const *  : true \
            ) \
}

/** Structure to encapsulate a thread local dbuff information
 *
 */
typedef struct {
  fr_dbuff_t      dbuff;    //!< Thread local dbuff.
  fr_dbuff_uctx_talloc_t    tctx;   //!< Thread local tctx.
} fr_dbuff_thread_local_t;

static inline int _dbuff_thread_local_free(void *dbtl)
{
  return talloc_free(dbtl);
}

/** Create a function local and thread local extensible dbuff
 *
 * @param[out] _out   Where to write a pointer to the thread local dbuff
 * @param[in] _init   Initial size for the dbuff buffer.
 * @param[in] _max    Maximum size of the dbuff buffer.
 */
#define FR_DBUFF_TALLOC_THREAD_LOCAL(_out, _init, _max) \
do { \
  static _Thread_local fr_dbuff_thread_local_t *_dbuff_t_local; \
  if (!_dbuff_t_local) { \
    fr_dbuff_thread_local_t *dbtl = talloc_zero(NULL, fr_dbuff_thread_local_t); \
    fr_dbuff_init_talloc(dbtl, &dbtl->dbuff, &dbtl->tctx, _init, _max); \
    fr_atexit_thread_local(_dbuff_t_local, _dbuff_thread_local_free, dbtl); \
    *(_out) = &_dbuff_t_local->dbuff; \
  } else { \
    fr_dbuff_reset_talloc(&_dbuff_t_local->dbuff); \
    *(_out) = &_dbuff_t_local->dbuff; \
  } \
} while (0)
/** @} */

/** @name Extension requests
 *
 * These functions/macros may be used to request that the underlying buffer is
 * either extended to accomodate more data, or that data is shifted out of the
 * buffer, and that the buffer is refilled.
 *
 * @{
 */

/** Flag indicating a dbuff is extendable
 */
#define FR_DBUFF_FLAG_EXTENDABLE    0x01

/** Flag indicating that during the last extend call the dbuff was extended
 */
#define FR_DBUFF_FLAG_EXTENDED      0x02

/** Whether the buffer is currently extendable and whether it was extended
 */
typedef enum {
  /** dbuff cannot be extended
   */
  FR_DBUFF_NOT_EXTENDABLE     = 0x00,

  /** dbuff can be extended
   */
  FR_DBUFF_EXTENDABLE     = FR_DBUFF_FLAG_EXTENDABLE,

  /** dbuff was extended in the last extend call and may be extended again
   */
  FR_DBUFF_EXTENDABLE_EXTENDED    = FR_DBUFF_FLAG_EXTENDABLE | FR_DBUFF_FLAG_EXTENDED,

  /** dbuff was extended in the last extend call but cannot be extended again
   */
  FR_DBUFF_EXTENDED     = FR_DBUFF_FLAG_EXTENDED
} fr_dbuff_extend_status_t;

/** Check if a dbuff can be extended again
 */
#define fr_dbuff_is_extendable(_status)   ((_status) & FR_DBUFF_FLAG_EXTENDABLE)

/** Check if the dbuff was extended during the last extend call
 */
#define fr_dbuff_was_extended(_status)    ((_status) & FR_DBUFF_FLAG_EXTENDED)

/** Internal function - do not call directly
 * @private
 */
static inline size_t _fr_dbuff_extend_lowat(fr_dbuff_extend_status_t *status, fr_dbuff_t *in,
              size_t remaining, size_t lowat)
{
  size_t extended = 0;

  if (status && !fr_dbuff_is_extendable(*status)) {
  not_extendable:
    if (status) *status = FR_DBUFF_NOT_EXTENDABLE;
    return remaining;
  }

  if (remaining >= lowat) {
    if (status) *status = FR_DBUFF_EXTENDABLE;
    return remaining;
  }

  if (!in->extend || !(extended = in->extend(in, lowat - remaining))) goto not_extendable;

  if (status) *status = FR_DBUFF_EXTENDABLE_EXTENDED;

  return remaining + extended;
}

/** Extend if we're below _lowat
 *
 * @param[out] _status    May be NULL.  If fr_dbuff_extend_lowat is used
 *        in a copy loop, the caller should pass a pointer
 *            to a #fr_dbuff_extend_status_t.  The initial
 *        value of the #fr_dbuff_extend_status_t variable
 *            should be #FR_DBUFF_EXTENDABLE, and will be updated
 *        to indicate whether the dbuff is extensible,
 *        whether it was extended, and whether it may be
 *        extended again.  This information
 *        is used the loop condition to prevent spurious
 *        extension calls.
 * @param[in] _dbuff_or_marker  to extend.
 * @param[in] _lowat    If bytes remaining are below the amount, extend.
 * @return
 *  - 0 if there are no bytes left in the buffer and we couldn't extend.
 *  - >0 the number of bytes in the buffer after extending.
 */
#define fr_dbuff_extend_lowat(_status, _dbuff_or_marker, _lowat) \
  _fr_dbuff_extend_lowat(_status, \
             fr_dbuff_ptr(_dbuff_or_marker), \
             fr_dbuff_remaining(_dbuff_or_marker), _lowat)

/** Extend if we're below _lowat and return if we can't extend above _lowat
 *
 * @param[in] _dbuff_or_marker  to extend.
 * @param[in] _lowat    If bytes remaining are below the amount, extend.
 * @return
 *  - 0 if there are no bytes left in the buffer and we couldn't extend.
 *  - >0 the number of bytes in the buffer after extending.
 */
#define FR_DBUFF_EXTEND_LOWAT_OR_RETURN(_dbuff_or_marker, _lowat) \
do { \
  size_t _remaining = fr_dbuff_extend_lowat(NULL, _dbuff_or_marker, _lowat); \
  if (_remaining < _lowat) return -(_lowat - _remaining); \
} while (0)

/** @cond */
/** Extend if we're below _lowat and return if we can't extend above _lowat
 *
 * @private
 *
 * @param[in,out] _pos_p  the position pointer to use.
 * @param[in] _dbuff_or_marker  to extend.
 * @param[in] _lowat    The minimum amount the dbuff should be extended by.
 * @return The number of bytes we would need to satisfy _lowat as a negative integer.
 */
#define _FR_DBUFF_EXTEND_LOWAT_POS_OR_RETURN(_pos_p, _dbuff_or_marker, _lowat) \
do { \
  size_t _remaining = _fr_dbuff_extend_lowat(NULL, \
               fr_dbuff_ptr(_dbuff_or_marker), \
                     fr_dbuff_end(_dbuff_or_marker) - (*(_pos_p)), _lowat); \
  if (_remaining < _lowat) return -(_lowat - _remaining); \
} while (0)
/** @endcond */

/** Extend if no space remains
 *
 * @param[in] _dbuff  to extend.
 * @return
 *  - 0 if there are no bytes left in the buffer and we couldn't extend.
 *  - >0 the number of bytes in the buffer after extending.
 */
#define fr_dbuff_extend(_dbuff) fr_dbuff_extend_lowat(NULL, _dbuff, 1)
/** @} */

/** @name Extension callback helpers
 *
 * These public functions are intended to be called by extension callbacks
 * to fixup dbuffs after the underlying buffer or its contents has been altered.
 * @{
 */
void  fr_dbuff_update(fr_dbuff_t *dbuff, uint8_t *new_buff, size_t new_len);

size_t  fr_dbuff_shift(fr_dbuff_t *dbuff, size_t shift);
/** @} */

/** @name Length checks
 *
 * These macros return the amount of data used/remaining relative to the dbuff
 * or marker's 'start', 'current', and 'end' pointers.
 *
 * In the majority of cases these macros should not be used and the extension
 * request functions should be used instead.  The only exception to this is if
 * the caller is certain the #fr_dbuff_t is not extensible.
 *
 * @{
 */
/** Return the number of bytes remaining between the dbuff or marker and the end of the buffer
 *
 * @note Do not use this in functions that may be used for stream decoding
 *   unless you're sure you know what you're doing.
 *   The value return does not reflect the number of bytes that may
 *   be potentially read from the stream, only the number of bytes
 *   until the end of the current chunk.
 *
 * @param[in] _dbuff_or_marker  to return the number of bytes remaining for.
 * @return
 *  - >0 the number of bytes remaining before we reach the end of the buffer.
 *  - -0 we're at the end of the buffer.
 */
#define fr_dbuff_remaining(_dbuff_or_marker) \
  ((size_t)(fr_dbuff_end(_dbuff_or_marker) < fr_dbuff_current(_dbuff_or_marker) ? \
    0 : (fr_dbuff_end(_dbuff_or_marker) - fr_dbuff_current(_dbuff_or_marker))))

/** Check if _len bytes are available in the dbuff and if not return the number of bytes we'd need
 *
 * @note Do not use this in functions that may be used for stream decoding
 *   unless you're sure you know what you're doing.
 *   The value return does not reflect the number of bytes that may
 *   be potentially read from the stream, only the number of bytes
 *   until the end of the current chunk.
 *
 * @param[in] _dbuff_or_marker  to return the number of bytes remaining for.
 * @param[in] _len    Minimum remaining bytes.
 * @return
 *  - >0 the number of bytes remaining before we reach the end of the buffer.
 *  - -0 we're at the end of the buffer.
 */
#define FR_DBUFF_REMAINING_RETURN(_dbuff_or_marker, _len) \
  if ((_len) > fr_dbuff_remaining(_dbuff_or_marker)) return -((_len) - fr_dbuff_remaining(_dbuff_or_marker))

/** Return the number of bytes remaining between the start of the dbuff or marker and the current position
 *
 */
#define fr_dbuff_used(_dbuff_or_marker) \
  ((size_t)(fr_dbuff_start(_dbuff_or_marker) > fr_dbuff_current(_dbuff_or_marker) ? \
    0 : (fr_dbuff_current(_dbuff_or_marker) - fr_dbuff_start(_dbuff_or_marker))))

/** The length of the underlying buffer
 *
 * @param[in] _dbuff_or_marker  to return the length of.
 * @return The length of the underlying buffer.
 */
#define fr_dbuff_len(_dbuff_or_marker) \
  ((size_t)(fr_dbuff_end(_dbuff_or_marker) - fr_dbuff_start(_dbuff_or_marker)))

/** How many bytes the dbuff or marker is behind its parent
 *
 * @param[in] _dbuff_or_marker
 * @return
 *  - 0 the dbuff or marker is ahead of its parent.
 *  - >0 the number of bytes the marker is behind its parent.
 */
#define fr_dbuff_behind(_dbuff_or_marker) \
  (fr_dbuff_current(_dbuff_or_marker) > fr_dbuff_current((_dbuff_or_marker)->parent) ? \
    0 : fr_dbuff_current((_dbuff_or_marker)->parent) - fr_dbuff_current(_dbuff_or_marker))

/** How many bytes the dbuff or marker is ahead of its parent
 *
 * @return
 *  - 0 the dbuff or marker is behind its parent.
 *  - >0 the number of bytes the marker is ahead of its parent.
 */
#define fr_dbuff_ahead(_dbuff_or_marker) \
  (fr_dbuff_current((_dbuff_or_marker)->parent) > fr_dbuff_current(_dbuff_or_marker) ? \
    0 : fr_dbuff_current(_dbuff_or_marker) - fr_dbuff_current((_dbuff_or_marker)->parent))
/** @} */

/** @name Accessors
 *
 * Caching the pointers returned by the accessors is strongly discouraged.
 * Cached pointers can become invalidated if the #fr_dbuff_t is extended, as
 * the extensions callback may use realloc or memmove on the underlying buffer.
 *
 @code{.c}
 fr_dbuff_t dbuff;
 fr_dbuff_uctx_talloc_t tctx;
 uint8_t *p;

 fr_dbuff_init_talloc(NULL, &dbuff, &tctx, 512, SIZE_MAX);

 p = fr_dbuff_current(&dbuff);      // Cache the start pointer
 fr_dbuff_extend_lowat(&dbuff, 1024);   // Extension call triggers realloc

 printf("%s", p);       // Should print an empty string but may
            // SEGV as p may now be invalid.
 @endcode
 *
 * If offsets of a #fr_dbuff_t need to be accessed, markers should be used.
 * If a dbuff is extended all markers associated with it will be updated so that the
 * content they point to remains constant.
 *
 @code{.c}
 fr_dbuff_t dbuff;
 fr_dbuff_uctx_talloc_t tctx;
 fr_dbuff_marker_t m;

 fr_dbuff_init_talloc(NULL, &dbuff, &tctx, 512, SIZE_MAX);
 fr_dbuff_marker(&m, &dbuff);

 fr_dbuff_extend_lowat(&dbuff, 1024);   // Extension call triggers realloc

 printf("%s", fr_dbuff_current(&m));    // Marker was updated when the dbuff
            // was extended.  All is well.
 @endcode
 *
 * Using offsets of the pointers returned by accessor functions is also strongly
 * discouraged as it invalidates many of the protections dbuffs give.
 *
 @code{.c}
 uint8_t buff[2];
 fr_dbuff_t dbuff;

 fr_dbuff_init(&dbuff, buff, sizeof(buff));
 fr_dbuff_current(&dbuff)[2] = 0x00;    // Write to invalid memory
 @endcode
 *
 * @{
 */

/** Return a pointer to the dbuff
 *
 * @param[in] _dbuff_or_marker  to return a pointer to.
 * @return A pointer to the dbuff.
 */
#define fr_dbuff_ptr(_dbuff_or_marker) \
  _Generic((_dbuff_or_marker), \
     fr_dbuff_t *     : ((fr_dbuff_t *)(_dbuff_or_marker)), \
     fr_dbuff_marker_t *    : (((fr_dbuff_marker_t *)(_dbuff_or_marker))->parent) \
  )

/** Return a const pointer to the dbuff
 *
 * @param[in] _dbuff_or_marker  to return a pointer to.
 * @return A pointer to the dbuff.
 */
#define fr_dbuff_ptr_const(_dbuff_or_marker) \
  _Generic((_dbuff_or_marker), \
     fr_dbuff_t *     : ((fr_dbuff_t const *)(_dbuff_or_marker)), \
     fr_dbuff_t const *   : ((fr_dbuff_t const *)(_dbuff_or_marker)), \
     fr_dbuff_marker_t *    : (((fr_dbuff_marker_t const *)(_dbuff_or_marker))->parent), \
     fr_dbuff_marker_t const *  : (((fr_dbuff_marker_t const *)(_dbuff_or_marker))->parent) \
  )

/** Return the underlying buffer in a dbuff or one of marker
 *
 * @param[in] _dbuff_or_marker  to return the buffer for.
 * @return A pointer to the start of the buffer.
 */
#define fr_dbuff_buff(_dbuff_or_marker) \
  _Generic((_dbuff_or_marker), \
     fr_dbuff_t *     : (((fr_dbuff_t const *)(_dbuff_or_marker))->buff), \
     fr_dbuff_t const *   : (((fr_dbuff_t const *)(_dbuff_or_marker))->buff), \
     fr_dbuff_marker_t *    : (((fr_dbuff_marker_t const *)(_dbuff_or_marker))->parent->buff), \
     fr_dbuff_marker_t const *  : (((fr_dbuff_marker_t const *)(_dbuff_or_marker))->parent->buff) \
  )

/** Return the 'start' position of a dbuff or marker
 *
 * The start position is not necessarily the start of the buffer, and is
 * advanced every time a dbuff is copied.
 *
 * @param[in] _dbuff_or_marker  to return the start position of.
 * @return A pointer to the start position of the buffer.
 */
#define fr_dbuff_start(_dbuff_or_marker) \
  (_Generic((_dbuff_or_marker), \
      fr_dbuff_t *      : (((fr_dbuff_t const *)(_dbuff_or_marker))->start), \
      fr_dbuff_t const *    : (((fr_dbuff_t const *)(_dbuff_or_marker))->start), \
      fr_dbuff_marker_t *   : (((fr_dbuff_marker_t const *)(_dbuff_or_marker))->parent->start), \
      fr_dbuff_marker_t const * : (((fr_dbuff_marker_t const *)(_dbuff_or_marker))->parent->start) \
  ))

/** Return the 'current' position of a dbuff or marker
 *
 * @param[in] _dbuff_or_marker  to return the current position of.
 * @return A pointer to the current position of the buffer or marker.
 */
#define fr_dbuff_current(_dbuff_or_marker) \
  (_Generic((_dbuff_or_marker), \
      fr_dbuff_t *      : (((fr_dbuff_t const *)(_dbuff_or_marker))->p), \
      fr_dbuff_t const *    : (((fr_dbuff_t const *)(_dbuff_or_marker))->p), \
      fr_dbuff_marker_t *   : (((fr_dbuff_marker_t const *)(_dbuff_or_marker))->p), \
      fr_dbuff_marker_t const * : (((fr_dbuff_marker_t const *)(_dbuff_or_marker))->p) \
  ))

/** @cond */
/** Return a pointer to the 'current' position in a dbuff or marker
 * @private
 *
 * @param[in] _dbuff_or_marker  to return a pointer to the position pointer for.
 * @return A pointer to the position pointer in the dbuff or marker.
 */
#define _fr_dbuff_current_ptr(_dbuff_or_marker) \
  (_Generic((_dbuff_or_marker), \
      fr_dbuff_t *      : &(((fr_dbuff_t *)(_dbuff_or_marker))->p), \
      fr_dbuff_marker_t *   : &(((fr_dbuff_marker_t *)(_dbuff_or_marker))->p) \
  ))
/** @endcond */

/** Return the current 'end' position of a dbuff or marker
 *
 * @param[in] _dbuff_or_marker  to return the end position of.
 * @return A pointer to the end position of the buffer or marker.
 */
#define fr_dbuff_end(_dbuff_or_marker) \
  (_Generic((_dbuff_or_marker), \
      fr_dbuff_t *      : (((fr_dbuff_t const *)(_dbuff_or_marker))->end), \
      fr_dbuff_t const *    : (((fr_dbuff_t const *)(_dbuff_or_marker))->end), \
      fr_dbuff_marker_t *   : (((fr_dbuff_marker_t const *)(_dbuff_or_marker))->parent->end), \
      fr_dbuff_marker_t const * : (((fr_dbuff_marker_t const *)(_dbuff_or_marker))->parent->end) \
  ))
/** @} */

/** @name Position modification (recursive)
 *
 * Modify the 'current' position pointer of a dbuff or marker.
 * @{
 */

/** Set a new 'current' position in a dbuff or marker
 * @private
 */
static inline void _fr_dbuff_set_recurse(fr_dbuff_t *dbuff, uint8_t adv_parent_flags, uint8_t const *p)
{
  if (adv_parent_flags & FR_DBUFF_ADV_PARENT_CURRENT) dbuff->p_i = p;
  if (adv_parent_flags & FR_DBUFF_ADV_PARENT_END) dbuff->end_i = p;

  if (dbuff->adv_parent && dbuff->parent) _fr_dbuff_set_recurse(dbuff->parent, dbuff->adv_parent, p);
}

/** Set a new 'current' position in a dbuff or marker
 * @private
 *
 * @param[in,out] pos_p   position pointer to modify.
 * @param[out] dbuff    dbuff to use for constraints checks.
 * @param[in] p     Position to set.
 * @return
 *  - 0 not advanced (p before dbuff start) or after dbuff end.
 *  - >0  the number of bytes the dbuff advanced by.
 *  - <0  the number of bytes the dbuff retreated by.
 *
 */
static inline ssize_t _fr_dbuff_set(uint8_t **pos_p, fr_dbuff_t *dbuff, uint8_t const *p)
{
  uint8_t *c;

  if (unlikely(p > dbuff->end)) return -(p - dbuff->end);
  if (unlikely(p < dbuff->start)) return 0;

  c = *pos_p;
  if (dbuff->adv_parent && dbuff->parent) _fr_dbuff_set_recurse(dbuff->parent, dbuff->adv_parent, p);
  *pos_p = UNCONST(uint8_t *, p);

  return p - c;
}

/** Set the 'current' position in a dbuff or marker using another dbuff or marker, a char pointer, or a length value
 *
 * @param[in] _dst  dbuff or marker to set the position for.
 * @param[in] _src  Variable to glean new position from.  Behaviour here
 *      depends on the type of the variable.
 *      - dbuff, the current position of the dbuff.
 *      - marker, the current position of the marker.
 *      - pointer, the position of the pointer.
 *      - size_t, _dst->start + _src.
 * @return
 *  - 0 not advanced.
 *  - >0  the number of bytes the dbuff was advanced by.
 *  - <0  the number of bytes required to complete the advancement
 */
#define fr_dbuff_set(_dst, _src) \
_fr_dbuff_set(\
  _fr_dbuff_current_ptr(_dst), fr_dbuff_ptr(_dst), \
  _Generic((_src), \
    fr_dbuff_t *      : fr_dbuff_current((fr_dbuff_t const *)(_src)), \
    fr_dbuff_marker_t *   : fr_dbuff_current((fr_dbuff_marker_t const *)(_src)), \
    uint8_t const *     : (uint8_t const *)(_src), \
    uint8_t *     : (uint8_t const *)(_src), \
    size_t        : (fr_dbuff_start(_dst) + (uintptr_t)(_src)), \
    long        : (fr_dbuff_start(_dst) + (uintptr_t)(_src)), \
    int       : (fr_dbuff_start(_dst) + (uintptr_t)(_src)) \
  ) \
)

/** Set the 'current' position in a dbuff or marker returning if _src is out of range
 *
 * @copydetails fr_dbuff_set
 */
#define FR_DBUFF_SET_RETURN(_dst, _src) FR_DBUFF_RETURN(fr_dbuff_set, _dst, _src)

/** Set a new 'end' position in a dbuff or marker
 * @private
 *
 * @param[out] dbuff    dbuff to use for constraints checks.
 * @param[in] p     Position to set.
 * @return
 *  - 0 not advanced (p before dbuff start) or after dbuff end.
 *  - >0  the number of bytes the dbuff was trimmed by.
 */
static inline ssize_t _fr_dbuff_set_end(fr_dbuff_t *dbuff, uint8_t const *p)
{
  if (unlikely(p > dbuff->end)) return -(p - dbuff->end);
  if (unlikely(p < dbuff->start)) return 0;

  dbuff->end = UNCONST(uint8_t *, p);

  return dbuff->end - p;
}

/** Set a new 'end' position in a dbuff or marker
 *
 * @param[out] _dst   dbuff to use for constraints checks.
 * @param[in] _end    Position to set.
 * @return
 *  - 0 not advanced (p before dbuff start) or after dbuff end.
 *  - >0  the number of bytes the dbuff was trimmed by.
 */
#define fr_dbuff_set_end(_dst, _end) \
_fr_dbuff_set_end(\
  fr_dbuff_ptr(_dst), \
  _Generic((_end), \
    fr_dbuff_t *      : fr_dbuff_current((fr_dbuff_t const *)(_end)), \
    fr_dbuff_marker_t *   : fr_dbuff_current((fr_dbuff_marker_t const *)(_end)), \
    uint8_t const *     : (uint8_t const *)(_end), \
    uint8_t *     : (uint8_t const *)(_end) \
  ) \
)

/** Advance 'current' position in dbuff or marker by _len bytes
 *
 * @param[in] _dbuff_or_marker  to advance.
 * @param[in] _len    How much to advance dbuff by.
 *        Must be a positive integer.
 * @return
 *  - 0 not advanced.
 *  - >0  the number of bytes the dbuff or marker was advanced by.
 *  - <0  the number of bytes required to complete the advancement
 */
#define fr_dbuff_advance(_dbuff_or_marker, _len)  \
  fr_dbuff_set(_dbuff_or_marker, \
         (fr_dbuff_current(_dbuff_or_marker) + \
         (_Generic((_len), \
      unsigned char : (size_t)(_len), \
      unsigned short : (size_t)(_len), \
      unsigned int : (size_t)(_len), \
      unsigned long : (size_t)(_len), \
      unsigned long long : (size_t)(_len), \
      int : (size_t)(_len) \
         ))))

/** Advance the 'current' position in dbuff or marker by _len bytes returning if _len is out of range
 *
 * @copydetails fr_dbuff_advance
 */
#define FR_DBUFF_ADVANCE_RETURN(_dbuff_or_marker, _len) FR_DBUFF_RETURN(fr_dbuff_advance, _dbuff_or_marker, _len)

/** Advance a dbuff or marker potentially extending it
 * @private
 *
 * @param[in,out] pos_p   position pointer to modify.
 * @param[out] dbuff    dbuff to use for constraints checks.
 * @param[in] len   Number of bytes to advance by.
 * @return
 *  - 0 not advanced, specified length would take us
 *    past the end of the buffer, and we couldn't extend
 *    by enough bytes.
 *  - >0  the number of bytes the dbuff advanced by.
 *      - <0  the number of bytes we'd need to complete the advance.
 *
 */
static inline ssize_t _fr_dbuff_advance_extend(uint8_t **pos_p, fr_dbuff_t *dbuff, size_t len)
{
  uint8_t *p = *pos_p + len;

  if (p > dbuff->end) {
    size_t rel = p - dbuff->start;        /* Get relative position to the start */

    if (!dbuff->extend) {
    oos:
      return -((dbuff->start + rel) - dbuff->end);
    }

    dbuff->extend(dbuff, p - dbuff->end);     /* Try and extend by the number of bytes over */
    if ((dbuff->start + rel) > dbuff->end) goto oos;

    *pos_p = dbuff->start + rel;        /* Update pos_p */
  } else {
    *pos_p += len;
  }

  if (dbuff->adv_parent && dbuff->parent) _fr_dbuff_set_recurse(dbuff->parent, dbuff->adv_parent, *pos_p);

  return len;
}

/** Advance current'position in dbuff or marker by _len bytes (extending if necessary)
 *
 * @param[in] _dbuff_or_marker  to advance.
 * @param[in] _len    How much to advance dbuff by.
 *        Must be a positive integer.
 * @return
 *  - 0 not advanced.
 *  - >0  the number of bytes the dbuff or marker was advanced by.
 *      - <0  the number of bytes we'd need to complete the advance.
 */
#define fr_dbuff_advance_extend(_dbuff_or_marker, _len)  \
  _fr_dbuff_advance(_fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), \
        (_Generic((_len), \
          unsigned char : (size_t)(_len), \
        unsigned short : (size_t)(_len), \
          unsigned int : (size_t)(_len), \
        unsigned long : (size_t)(_len), \
          unsigned long long : (size_t)(_len), \
          int : (size_t)(_len) \
        )))

#define FR_DBUFF_BIND_EXTEND_RETURN(_dbuff_or_marker, _len) FR_DBUFF_RETURN(fr_dbuff_advance_extend, _dbuff_or_marker, _len)

/** Reset the 'current' position of the dbuff or marker to the 'start' of the buffer
 *
 */
#define fr_dbuff_set_to_start(_dbuff_or_marker) \
  fr_dbuff_set(_dbuff_or_marker, fr_dbuff_start(_dbuff_or_marker))

/** Reset the 'current' position of the dbuff or marker to the 'end' of the buffer
 *
 */
#define fr_dbuff_set_to_end(_dbuff_or_marker) \
  fr_dbuff_set(_dbuff_or_marker, fr_dbuff_end(_dbuff_or_marker))
/** @} */

/** @name Marker management
 *
 * Markers serve two purposes:
 *
 * - Markers allow the caller to track content in a dbuff as the dbuff is extended.
 *   If the caller referred to content using a pointer into the underlying buffer,
 *   that pointer may be invalidated if the buffer were extended.
 *
 * - Markers prevent content being shifted out of the buffer during an extension.
 *
 * Most operations that can be performed on an #fr_dbuff_t can also be performed
 * on a #fr_dbuff_marker_t.
 *
 * It is recommended that markers be created against a stack-frame-local dbuff so
 * that they are automatically released when the framed is popped.
 *
 * @see fr_dbuff_marker_t
 *
 * @{
 */

/** Initialises a new marker pointing to the 'current' position of the dbuff
 *
 * @param[out] m  to initialise.
 * @param[in] dbuff to associate marker with.
 * @return The position the marker was set to.
 */
static inline uint8_t *fr_dbuff_marker(fr_dbuff_marker_t *m, fr_dbuff_t *dbuff)
{
  *m = (fr_dbuff_marker_t){
    .next = dbuff->m, /* Link into the head */
    .p = dbuff->p,    /* Set the current position in the dbuff */
    .parent = dbuff   /* Record which dbuff this marker was associated with */
  };
  dbuff->m = m;

  return dbuff->p;
}

/** Releases the specified marker and any markers added before it
 *
 * Pointers should be released in the inverse order to allocation.
 *
 * @param[in] m   to release.
 */
static inline void fr_dbuff_marker_release(fr_dbuff_marker_t *m)
{
  m->parent->m = m->next;

#ifndef NDEBUG
  memset(m, 0, sizeof(*m)); /* Use after release */
#endif
}

/** Trims the linked list back to the specified pointer and return how many bytes marker was behind p
 *
 * Pointers should be released in the inverse order to allocation.
 *
 * Alternatively the oldest pointer can be released, resulting in any newer pointer
 * also being removed from the list.
 *
 * @param[in] m   to release.
 * @return
 *  - 0 marker is ahead of p.
 *  - >0 the number of bytes the marker is behind p.
 */
static inline size_t fr_dbuff_marker_release_behind(fr_dbuff_marker_t *m)
{
  size_t len = fr_dbuff_behind(m);
  fr_dbuff_marker_release(m);
  return len;
}

/** Trims the linked list back to the specified pointer and return how many bytes marker was ahead of p
 *
 * Pointers should be released in the inverse order to allocation.
 *
 * Alternatively the oldest pointer can be released, resulting in any newer pointer
 * also being removed from the list.
 *
 * @param[in] m   to release.
 * @return
 *  - 0 marker is ahead of p.
 *  - >0 the number of bytes the marker is behind p.
 */
static inline size_t fr_dbuff_marker_release_ahead(fr_dbuff_marker_t *m)
{
  size_t len = fr_dbuff_ahead(m);
  fr_dbuff_marker_release(m);
  return len;
}
/** @} */

/** @name "in" functions (copy data into a dbuff)
 * @{
 */

/** Internal copy function to switch between memcpy and memmove - do not call directly
 *
 * @private
 *
 * @param[out] o_start    Where to copy data to.
 * @param[in] o_end   end of the output buffer.
 * @param[in] i_start   Where to copy data from.
 * @param[in] i_end   end of the source buffer.
 * @return
 *  - 0 on sanity check error.
 *  - >0 the number of bytes copied.
 */
static inline CC_HINT(always_inline) size_t _fr_dbuff_safecpy(uint8_t *o_start, uint8_t *o_end,
                    uint8_t const *i_start, uint8_t const *i_end)
{
  ssize_t diff;
  size_t  i_len = i_end - i_start;

  if (unlikely((o_end < o_start) || (i_end < i_start))) return 0; /* sanity check */

  diff = (o_end - o_start) - (i_len);
  if (diff < 0) return 0;

  if ((i_start > o_end) || (i_end < o_start)) {     /* no-overlap */
    memcpy(o_start,  i_start, i_len);
  } else {             /* overlap */
    memmove(o_start, i_start, i_len);
  }

  return (i_len);
}

/** Internal function - do not call directly
 *
 * @private
 */
static inline ssize_t _fr_dbuff_in_memcpy(uint8_t **pos_p, fr_dbuff_t *out,
            uint8_t const *in, size_t inlen)
{
  fr_assert(!out->is_const);

  _FR_DBUFF_EXTEND_LOWAT_POS_OR_RETURN(pos_p, out, inlen);

  return _fr_dbuff_set(pos_p, out, (*pos_p) + _fr_dbuff_safecpy((*pos_p), (*pos_p) + inlen, in, in + inlen));   /* Advance out */
}

/** Internal function - do not call directly
 *
 * @private
 */
static inline ssize_t _fr_dbuff_in_memcpy_dbuff(uint8_t **pos_p, fr_dbuff_t *out,
                  uint8_t * const *in_p, fr_dbuff_t const *in, size_t inlen)
{
  fr_dbuff_t  *our_in;
  uint8_t   **our_in_p;
  size_t    ext_len;

  memcpy(&our_in, &in, sizeof(our_in));   /* Stupid const issues caused by generics */
  memcpy(&our_in_p, &in_p, sizeof(our_in_p)); /* Stupid const issues caused by generics */

  if (inlen == SIZE_MAX) {
    ext_len = _fr_dbuff_extend_lowat(NULL, our_in, fr_dbuff_end(our_in) - (*our_in_p), inlen);
    if (ext_len < inlen) inlen = ext_len;
  } else {
    _FR_DBUFF_EXTEND_LOWAT_POS_OR_RETURN(our_in_p, our_in, inlen);    /* Extend in or return */
  }
  return _fr_dbuff_in_memcpy(pos_p, out, *our_in_p, inlen);     /* Copy _in to _out */
}

/** Copy exactly _inlen bytes into a dbuff or marker
 *
 * If _in is a dbuff and _inlen is greater than the number of bytes available
 * in that dbuff, the copy operation will fail.
 *
 * @note _in will not be advanced.  If this is required #fr_dbuff_move should be used.
 *
 * @param[in] _dbuff_or_marker  to copy data to.
 * @param[in] _in   data to copy in to the dbuff or marker.
 * @param[in] _inlen    How much data we need to copy.
 *        If _in is a `char *` or `dbuff *` and SIZE_MAX
 *        is passed, then _inlen will be substituted
 *        for the length of the data in the dbuff.
 * @return
 *  - 0 no data copied.
 *  - >0  the number of bytes copied to the dbuff.
 *  - <0  the number of bytes we would have needed
 *    to complete the copy operation.
 */
#define fr_dbuff_in_memcpy(_dbuff_or_marker, _in, _inlen) \
  _Generic((_in), \
    uint8_t *   : _fr_dbuff_in_memcpy(_fr_dbuff_current_ptr(_dbuff_or_marker), \
                    fr_dbuff_ptr(_dbuff_or_marker), \
                    (uint8_t const *)(_in), \
                    _inlen), \
    uint8_t const *   : _fr_dbuff_in_memcpy(_fr_dbuff_current_ptr(_dbuff_or_marker), \
                    fr_dbuff_ptr(_dbuff_or_marker), \
                    (uint8_t const *)(_in), \
                    _inlen), \
    char *      : _fr_dbuff_in_memcpy(_fr_dbuff_current_ptr(_dbuff_or_marker), \
                    fr_dbuff_ptr(_dbuff_or_marker), \
                    (uint8_t const *)(_in), \
                    (size_t)(_inlen) == SIZE_MAX ? strlen((char const *)(_in)) : (_inlen)), \
    char const *    : _fr_dbuff_in_memcpy(_fr_dbuff_current_ptr(_dbuff_or_marker), \
                    fr_dbuff_ptr(_dbuff_or_marker), \
                    (uint8_t const *)(_in), \
                    (size_t)(_inlen) == SIZE_MAX ? strlen((char const *)(_in)) : (_inlen)), \
    fr_dbuff_t *    : _fr_dbuff_in_memcpy_dbuff(_fr_dbuff_current_ptr(_dbuff_or_marker), \
                    fr_dbuff_ptr(_dbuff_or_marker), \
                    &((fr_dbuff_t const *)(_in))->p, \
                    ((fr_dbuff_t const *)(_in)), \
                    _inlen), \
    fr_dbuff_marker_t * : _fr_dbuff_in_memcpy_dbuff(_fr_dbuff_current_ptr(_dbuff_or_marker), \
                    fr_dbuff_ptr(_dbuff_or_marker), \
                    &((fr_dbuff_marker_t const *)(_in))->p, \
                    ((fr_dbuff_marker_t const *)(_in))->parent, _inlen) \
  )

/** Copy exactly _inlen bytes into dbuff or marker returning if there's insufficient space
 * @copydetails fr_dbuff_in_memcpy
 */
#define FR_DBUFF_IN_MEMCPY_RETURN(_dbuff_or_marker, _in, _inlen) FR_DBUFF_RETURN(fr_dbuff_in_memcpy, _dbuff_or_marker, _in, _inlen)

/** Internal function - do not call directly
 *
 * @private
 */
static inline size_t _fr_dbuff_in_memcpy_partial(uint8_t **pos_p, fr_dbuff_t *out,
             uint8_t const *in, size_t inlen)
{
  size_t ext_len;

  fr_assert(!out->is_const);

  ext_len = _fr_dbuff_extend_lowat(NULL, out, fr_dbuff_end(out) - (*pos_p), inlen);
  if (ext_len < inlen) inlen = ext_len;

  return _fr_dbuff_set(pos_p, out, (*pos_p) + _fr_dbuff_safecpy((*pos_p), (*pos_p) + inlen, in, in + inlen));
}

/** Internal function - do not call directly
 *
 * @private
 */
static inline size_t _fr_dbuff_in_memcpy_partial_dbuff(uint8_t **pos_p, fr_dbuff_t *out,
                   uint8_t * const *in_p, fr_dbuff_t const *in, size_t inlen)
{
  fr_dbuff_t  *our_in = UNCONST(fr_dbuff_t *, in);  /* Stupid const issues caused by generics */
  uint8_t   **our_in_p = UNCONST(uint8_t **, in_p); /* Stupid const issues caused by generics */
  size_t    ext_len;

  ext_len = _fr_dbuff_extend_lowat(NULL, our_in, fr_dbuff_end(our_in) - (*our_in_p), inlen);
  if (ext_len < inlen) inlen = ext_len;

  return _fr_dbuff_in_memcpy_partial(pos_p, out, (*our_in_p), inlen);
}

/** Copy at most _inlen bytes into the dbuff
 *
 * Use this variant when writing data to a streaming buffer where
 * partial writes will be tracked.
 *
 * If _in is a #fr_dbuff_t and _inlen is greater than the number of bytes
 * available in that dbuff, the copy operation will truncated.
 *
 * @note _in will not be advanced.  If this is required #fr_dbuff_move should be used.
 *
 * @param[in] _out  to copy data to.
 * @param[in] _in Data to copy to dbuff.
 * @param[in] _inlen  How much data we need to copy.
 *      If _in is a char * or dbuff * and SIZE_MAX
 *      is passed, then _inlen will be substituted
 *      for the length of the buffer.
 * @return
 *  - 0 no data copied.
 *  - >0  the number of bytes copied to the dbuff.
 */
#define fr_dbuff_in_memcpy_partial(_out, _in, _inlen) \
  _Generic((_in), \
    uint8_t *   : _fr_dbuff_in_memcpy_partial(_fr_dbuff_current_ptr(_out), _out, (uint8_t const *)(_in), _inlen), \
    uint8_t const *   : _fr_dbuff_in_memcpy_partial(_fr_dbuff_current_ptr(_out), _out, (uint8_t const *)(_in), _inlen), \
    char *      : _fr_dbuff_in_memcpy_partial(_fr_dbuff_current_ptr(_out), _out, (uint8_t const *)(_in), _inlen == SIZE_MAX ? strlen((char const *)(_in)) : _inlen), \
    char const *    : _fr_dbuff_in_memcpy_partial(_fr_dbuff_current_ptr(_out), _out, (uint8_t const *)(_in), _inlen == SIZE_MAX ? strlen((char const *)(_in)) : _inlen), \
    fr_dbuff_t *    : _fr_dbuff_in_memcpy_partial_dbuff(_fr_dbuff_current_ptr(_out), fr_dbuff_ptr(_out), &((fr_dbuff_t const *)(_in))->p, ((fr_dbuff_t const *)(_in)), _inlen), \
    fr_dbuff_marker_t * : _fr_dbuff_in_memcpy_partial_dbuff(_fr_dbuff_current_ptr(_out), fr_dbuff_ptr(_out), &((fr_dbuff_marker_t const *)(_in))->p, ((fr_dbuff_marker_t const *)(_in))->parent, _inlen) \
  )

/** Copy a partial byte sequence into a dbuff
 *
 * @copybrief fr_dbuff_in_memcpy_partial
 *
 * @param[in] _dbuff  to copy byte sequence into.
 * @param[in] ... bytes to copy.
 */
#define fr_dbuff_in_bytes_partial(_dbuff, ...) \
  fr_dbuff_in_memcpy_partial(_dbuff, ((uint8_t []){ __VA_ARGS__ }), sizeof((uint8_t []){ __VA_ARGS__ }))

/** Copy a byte sequence into a dbuff or marker
 *
 * @copybrief fr_dbuff_in_memcpy
 *
 * @param[in] _dbuff_or_marker  to copy byte sequence into.
 * @param[in] ...   bytes to copy.
 */
#define fr_dbuff_in_bytes(_dbuff_or_marker, ...) \
  fr_dbuff_in_memcpy(_dbuff_or_marker, ((uint8_t []){ __VA_ARGS__ }), sizeof((uint8_t []){ __VA_ARGS__ }))

/** Copy a byte sequence into a dbuff or marker returning if there's insufficient space
 *
 * @copydetails fr_dbuff_in_bytes
 */
#define FR_DBUFF_IN_BYTES_RETURN(_dbuff_or_marker, ...) \
  FR_DBUFF_IN_MEMCPY_RETURN(_dbuff_or_marker, ((uint8_t []){ __VA_ARGS__ }), sizeof((uint8_t []){ __VA_ARGS__ }))

/** Internal function - do not call directly
 *
 * @private
 */
static inline ssize_t _fr_dbuff_memset(uint8_t **pos_p, fr_dbuff_t *dbuff, uint8_t c, size_t inlen)
{
  fr_assert(!dbuff->is_const);

  _FR_DBUFF_EXTEND_LOWAT_POS_OR_RETURN(pos_p, dbuff, inlen);

  memset((*pos_p), c, inlen);

  return _fr_dbuff_set(pos_p, dbuff, (*pos_p) + inlen);
}

/** Set _inlen bytes of a dbuff or marker to _c
 *
 * @param[in] _dbuff_or_marker  to copy data to.
 *        Will be advanced by _inlen bytes.
 * @param[in] _c    Value to set.
 * @param[in] _inlen    How much data we need to copy.
 * @return
 *  - 0 no data set.
 *  - >0  the number of bytes set in the dbuff.
 *  - <0  the number of bytes required.
 */
#define fr_dbuff_memset(_dbuff_or_marker, _c, _inlen) \
  _fr_dbuff_memset(_fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), _c, _inlen)

/** Set _inlen bytes of a dbuff or marker to _c returning if there is insufficient space
 *
 * @copydetails fr_dbuff_memset
 */
#define FR_DBUFF_MEMSET_RETURN(_dbuff_or_marker, _c, _inlen) FR_DBUFF_RETURN(fr_dbuff_memset, _dbuff_or_marker, _c, _inlen)

/** @cond */
/** Define integer decoding functions
 * @private
 */
#define FR_DBUFF_PARSE_INT_DEF(_type) \
static inline ssize_t _fr_dbuff_in_##_type(uint8_t **pos_p, fr_dbuff_t *out, _type##_t num) \
{ \
  fr_assert(!out->is_const); \
  _FR_DBUFF_EXTEND_LOWAT_POS_OR_RETURN(pos_p, out, sizeof(_type##_t)); \
  fr_nbo_from_##_type((*pos_p), num); \
  return _fr_dbuff_set(pos_p, out, (*pos_p) + sizeof(_type##_t)); \
}
FR_DBUFF_PARSE_INT_DEF(uint16)
FR_DBUFF_PARSE_INT_DEF(uint32)
FR_DBUFF_PARSE_INT_DEF(uint64)
FR_DBUFF_PARSE_INT_DEF(int16)
FR_DBUFF_PARSE_INT_DEF(int32)
FR_DBUFF_PARSE_INT_DEF(int64)
/** @endcond */

/*

 */

/** Internal function - do not call directly
 *
 * The fr_dbuff_in_<type>() functions take rvalues, so to implement float and
 * double in terms of the same-sized integers, we need a layer that gives us an
 * lvalue whose address we can cast.
 *
 * @private
 */
static inline ssize_t _fr_dbuff_in_float(uint8_t **pos_p, fr_dbuff_t *out, float num)
{
  return _fr_dbuff_in_uint32(pos_p, out, *(uint32_t *)(&num));
}

/** Internal function - do not call directly
 *
 * @copydetails _fr_dbuff_in_float
 *
 * @private
 */
static inline ssize_t _fr_dbuff_in_double(uint8_t **pos_p, fr_dbuff_t *out, double num)
{
  return _fr_dbuff_in_uint64(pos_p, out, *(uint64_t *)(&num));
}

/** Copy data from a fixed sized C type into a dbuff or marker
 *
 * @param[out] _dbuff_or_marker   to write to.  Integer types will be automatically
          converted to big endian byte order.
 * @param[in] _in     Value to copy.
 * @return
 *  - <0 the number of bytes we would have needed to complete the conversion.
 *  - >0 the number of bytes _dbuff_or_marker was advanced by.
 */
#define fr_dbuff_in(_dbuff_or_marker, _in) \
  _Generic((_in), \
    int8_t    : fr_dbuff_in_bytes(_dbuff_or_marker, (int8_t)_in), \
    int16_t   : _fr_dbuff_in_int16(_fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), (int16_t)_in), \
    int32_t   : _fr_dbuff_in_int32(_fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), (int32_t)_in), \
    int64_t   : _fr_dbuff_in_int64(_fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), (int64_t)_in), \
    uint8_t   : fr_dbuff_in_bytes(_dbuff_or_marker, (uint8_t)_in), \
    uint16_t  : _fr_dbuff_in_uint16(_fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), (uint16_t)_in), \
    uint32_t  : _fr_dbuff_in_uint32(_fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), (uint32_t)_in), \
    uint64_t  : _fr_dbuff_in_uint64(_fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), (uint64_t)_in), \
    float   : _fr_dbuff_in_float(_fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), (float)_in), \
    double    : _fr_dbuff_in_double(_fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), (double)_in) \
  )

/** Copy data from a fixed sized C type into a dbuff returning if there is insufficient space
 *
 * @copydetails fr_dbuff_in
 */
#define FR_DBUFF_IN_RETURN(_dbuff_or_marker, _in) FR_DBUFF_RETURN(fr_dbuff_in, _dbuff_or_marker, _in)

/** Internal function - do not call directly
 * @private
 */
static inline ssize_t _fr_dbuff_in_uint64v(uint8_t **pos_p, fr_dbuff_t *dbuff, uint64_t num)
{
  size_t  ret;
  uint8_t swapped[sizeof(uint64_t)];

  ret = ROUND_UP_DIV((size_t)fr_high_bit_pos(num | 0x08), 8);
  fr_nbo_from_uint64(swapped, num);

  return _fr_dbuff_in_memcpy(pos_p, dbuff, (swapped + (sizeof(uint64_t) - ret)), ret);
}

/** Copy an integer value into a dbuff or marker using our internal variable length encoding
 *
 * @param[out] _dbuff_or_marker   to copy integer value to.
 * @param[in] _num      to copy.
 * @return
 *  - <0 the number of bytes we would have needed to encode the integer value.
 *  - >0 the number of bytes used to represent the integer value.
 */
#define fr_dbuff_in_uint64v(_dbuff_or_marker, _num) \
  _fr_dbuff_in_uint64v(_fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), _num)

/** Copy an integer value into a dbuff or marker using our internal variable length encoding returning if there is insufficient space
 *
 * @copydetails fr_dbuff_in_uint64v
 */
#define FR_DBUFF_IN_UINT64V(_dbuff_or_marker, _num) FR_DBUFF_RETURN(fr_dbuff_in_uint64v, _dbuff_or_marker, _num)
/** @} */

/** @name "move" functions (copy data between dbuffs and markers)
 * @{
 */
/** Internal function - do not call directly
 * @private
 */
size_t _fr_dbuff_move_dbuff_to_dbuff(fr_dbuff_t *out, fr_dbuff_t *in, size_t len);

/** Internal function - do not call directly
 * @private
 */
size_t _fr_dbuff_move_dbuff_to_dbuff_marker(fr_dbuff_marker_t *out, fr_dbuff_t *in, size_t len);

/** Internal function - do not call directly
 * @private
 */
size_t _fr_dbuff_move_dbuff_marker_to_dbuff(fr_dbuff_t *out, fr_dbuff_marker_t *in, size_t len);

/** Internal function - do not call directly
 * @private
 */
size_t _fr_dbuff_move_dbuff_marker_to_dbuff_marker(fr_dbuff_marker_t *out, fr_dbuff_marker_t *in, size_t len);

/** Copy in as many bytes as possible from one dbuff or marker to another
 *
 * @warning Advances both _in and _out by _len, this may not be what you want.
 *      If you only want _out to be advanced use fr_dbuff_in_memcpy(_out, _in, _len).
 *      If you only want _in to be advanced use fr_dbuff_out_memcpy(_out, _in, _len).
 *
 * @param[in] _out  to copy into.
 * @param[in] _in to copy from.
 * @param[in] _len  The maximum length to copy.
 * @return Number of bytes to copy.
 */
#define fr_dbuff_move(_out, _in, _len) \
  _Generic((_out), \
    fr_dbuff_t *    : \
    _Generic((_in), \
      fr_dbuff_t *    : _fr_dbuff_move_dbuff_to_dbuff((fr_dbuff_t *)_out, \
                    (fr_dbuff_t *)_in, \
                    _len), \
      fr_dbuff_marker_t * : _fr_dbuff_move_dbuff_marker_to_dbuff((fr_dbuff_t *)_out, \
                           (fr_dbuff_marker_t *)_in, \
                           _len) \
    ), \
    fr_dbuff_marker_t * : \
    _Generic((_in), \
      fr_dbuff_t *    : _fr_dbuff_move_dbuff_to_dbuff_marker((fr_dbuff_marker_t *)_out, \
                           (fr_dbuff_t *)_in, \
                           _len), \
      fr_dbuff_marker_t * : _fr_dbuff_move_dbuff_marker_to_dbuff_marker((fr_dbuff_marker_t *)_out, \
                            (fr_dbuff_marker_t *)_in, \
                            _len) \
    ) \
  )
/** @} */

/** @name "out" functions (copy data out of a dbuff)
 * @{
 */

/** Internal function - do not call directly
 *
 * @private
 */
static inline ssize_t _fr_dbuff_out_memcpy(uint8_t *out, uint8_t **pos_p, fr_dbuff_t *in, size_t outlen)
{
  size_t  ext_len, to_copy, remaining;

  for (remaining = outlen; remaining > 0; remaining -= to_copy) {
    to_copy = remaining;
    ext_len = _fr_dbuff_extend_lowat(NULL, in, fr_dbuff_end(in) - (*pos_p), 1);
    if (ext_len == 0) return -remaining;
    if (ext_len < to_copy) to_copy = ext_len;
    out += _fr_dbuff_set(pos_p, in,
             (*pos_p) + _fr_dbuff_safecpy(out, out + to_copy, (*pos_p), (*pos_p) + to_copy));
  }

  return outlen;
}
/** Internal function - do not call directly
 *
 * @private
 */
static inline ssize_t _fr_dbuff_out_memcpy_dbuff(uint8_t **out_p, fr_dbuff_t *out, uint8_t **pos_p, fr_dbuff_t *in, size_t outlen)
{
  if (outlen == SIZE_MAX) outlen = _fr_dbuff_extend_lowat(NULL, out, fr_dbuff_end(out) - (*out_p), outlen);

  return _fr_dbuff_out_memcpy((*out_p), pos_p, in, outlen);
}

/** Copy exactly _outlen bytes from the dbuff
 *
 * If _out is a dbuff and _outlen is greater than the number of bytes
 * available in that dbuff, the copy operation will fail.
 *
 * @note _out will not be advanced.  If this is required #fr_dbuff_move should be used.
 *
 * @param[in] _out    either a buffer, or another dbuff/marker to copy data to.
 * @param[in] _dbuff_or_marker  to copy data from.
 * @param[in] _outlen   How much data we need to copy.
 *        If _out is `fr_dbuff_t *` and SIZE_MAX
 *        is passed, then _inlen will be substituted
 *        for the length of the buffer.
 * @return
 *  - 0 no data copied.
 *  - >0  the number of bytes copied.
 *  - <0  the number of bytes we would have needed
 *    to complete the copy operation.
 */
#define fr_dbuff_out_memcpy(_out, _dbuff_or_marker, _outlen) \
  _Generic((_out), \
     uint8_t *    : _fr_dbuff_out_memcpy((uint8_t *)(_out), \
                     _fr_dbuff_current_ptr(_dbuff_or_marker), \
                     fr_dbuff_ptr(_dbuff_or_marker), \
                     _outlen), \
     fr_dbuff_t *   : _fr_dbuff_out_memcpy_dbuff(_fr_dbuff_current_ptr((fr_dbuff_t *)_out), \
                     fr_dbuff_ptr((fr_dbuff_t *)(_out)), \
                     _fr_dbuff_current_ptr(_dbuff_or_marker), \
                     fr_dbuff_ptr(_dbuff_or_marker), _outlen), \
     fr_dbuff_marker_t *  : _fr_dbuff_out_memcpy_dbuff(_fr_dbuff_current_ptr((fr_dbuff_marker_t *)_out), \
                     fr_dbuff_ptr((fr_dbuff_marker_t *)(_out)), \
                     _fr_dbuff_current_ptr(_dbuff_or_marker), \
                     fr_dbuff_ptr(_dbuff_or_marker), _outlen) \
  )

/** Copy outlen bytes from the dbuff returning if there's insufficient data in the dbuff
 *
 * @copydetails fr_dbuff_out_memcpy
 */
#define FR_DBUFF_OUT_MEMCPY_RETURN(_out, _dbuff_or_marker, _outlen) FR_DBUFF_RETURN(fr_dbuff_out_memcpy, _out, _dbuff_or_marker, _outlen)

/** @cond */
/** Define integer encoding functions
 * @private
 */
#define FR_DBUFF_OUT_DEF(_type) \
static inline ssize_t _fr_dbuff_out_##_type(_type##_t *out, uint8_t **pos_p, fr_dbuff_t *in) \
{ \
  fr_assert(out); \
  FR_DBUFF_EXTEND_LOWAT_OR_RETURN(in, sizeof(_type##_t)); \
  *out = fr_nbo_to_##_type((*pos_p)); \
  return _fr_dbuff_set(pos_p, in, (*pos_p) + sizeof(_type##_t)); \
}

FR_DBUFF_OUT_DEF(uint16)
FR_DBUFF_OUT_DEF(uint32)
FR_DBUFF_OUT_DEF(uint64)
FR_DBUFF_OUT_DEF(int16)
FR_DBUFF_OUT_DEF(int32)
FR_DBUFF_OUT_DEF(int64)
/** @endcond */

/** Copy data from a dbuff or marker to a fixed sized C type
 *
 * @param[out] _out     Where to write the data.  If out is an integer type
 *          a byteswap will be performed if native endianess
 *              is not big endian.
 * @param[in] _dbuff_or_marker    to copy data from. Will be advanced by the number
 *          of bytes consumed, i.e. if out is a uin16_t *,
 *          _dbuff_or_marker will be advanced by two bytes.
 * @return
 *  - <0 the number of bytes we would have needed to complete the conversion.
 *  - >0 the number of bytes _in was advanced by.
 */
#define fr_dbuff_out(_out, _dbuff_or_marker) \
  _Generic((_out), \
    uint8_t * : _fr_dbuff_out_memcpy((uint8_t *)(_out), _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), 1), \
    uint16_t *  : _fr_dbuff_out_uint16((uint16_t *)(_out), _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker)), \
    uint32_t *  : _fr_dbuff_out_uint32((uint32_t *)(_out), _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker)), \
    uint64_t *  : _fr_dbuff_out_uint64((uint64_t *)(_out), _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker)), \
    int8_t *  : _fr_dbuff_out_memcpy((uint8_t *)(_out), _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), 1), \
    int16_t * : _fr_dbuff_out_int16((int16_t *)(_out), _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker)), \
    int32_t * : _fr_dbuff_out_int32((int32_t *)(_out), _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker)), \
    int64_t * : _fr_dbuff_out_int64((int64_t *)(_out), _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker)), \
    float *   : _fr_dbuff_out_uint32((uint32_t *)(_out), _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker)), \
    double *  : _fr_dbuff_out_uint64((uint64_t *)(_out), _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker)) \
  )

/** Copy data from a dbuff or marker to a fixed sized C type returning if there is insufficient data
 *
 * @copydetails fr_dbuff_out
 */
#define FR_DBUFF_OUT_RETURN(_out, _dbuff_or_marker) FR_DBUFF_RETURN(fr_dbuff_out, _out, _dbuff_or_marker)

/** Internal function - do not call directly
 * @private
 */
static inline ssize_t _fr_dbuff_out_uint64v(uint64_t *num, uint8_t **pos_p, fr_dbuff_t *dbuff, size_t length)
{
  ssize_t   slen;

  fr_assert(length > 0 && length <= sizeof(uint64_t));

  *num = 0;
  slen = _fr_dbuff_out_memcpy(((uint8_t *) num) + (8 - length), pos_p, dbuff, length);
  if (slen <= 0) return slen;

  *num = fr_nbo_to_uint64((uint8_t const *)num);
  return length;
}

/** Read bytes from a dbuff or marker and interpret them as a network order unsigned integer
 * @param[in] _num    points to a uint64_t to store the integer in
 * @param[in] _dbuff_or_marker  data to copy bytes from
 * @param[in] _len    number of bytes to read (must be positive and less than eight)
 *
 * @return
 *  - 0 no data read.
 *  - >0  the number of bytes read.
 *  - <0  the number of bytes we would have needed
 *    to complete the read operation.
 */
#define fr_dbuff_out_uint64v(_num, _dbuff_or_marker, _len) \
  _fr_dbuff_out_uint64v(_num, _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), _len)

/** Read bytes from a dbuff or marker and interpret them as a network order unsigned integer
 *
 * @copydetails fr_dbuff_out_uint64v
 */
#define FR_DBUFF_OUT_UINT64V_RETURN(_num, _dbuff_or_marker, _len) FR_DBUFF_RETURN(fr_dbuff_out_uint64v, _num, _dbuff_or_marker, _len)

/** Internal function - do not call directly
 * @private
 */
static inline ssize_t _fr_dbuff_out_int64v(int64_t *num, uint8_t **pos_p, fr_dbuff_t *dbuff, size_t length)
{
  ssize_t   slen;
  uint8_t   msb = **pos_p;

  fr_assert(length > 0 && length <= sizeof(uint64_t));

  *num = 0;
  slen = _fr_dbuff_out_memcpy(((uint8_t *) num) + (8 - length), pos_p, dbuff, length);
  if (slen <= 0) return slen;

  if (msb & 0x80) memset(((uint8_t *)num), 0xff, sizeof(*num) - length);
  *num = fr_nbo_to_int64((uint8_t const *)num);

  return length;
}

/** Read bytes from a dbuff or marker and interpret them as a network order signed integer
 * @param[in] _num    points to an int64_t to store the integer in
 * @param[in] _dbuff_or_marker  data to copy bytes from
 * @param[in] _len    number of bytes to read (must be positive and less than eight)
 *
 * @return
 *  - 0 no data read.
 *  - >0  the number of bytes read.
 *  - <0  the number of bytes we would have needed
 *    to complete the read operation.
 */
#define fr_dbuff_out_int64v(_num, _dbuff_or_marker, _len) \
  _fr_dbuff_out_int64v(_num, _fr_dbuff_current_ptr(_dbuff_or_marker), fr_dbuff_ptr(_dbuff_or_marker), _len)

/** Read bytes from a dbuff or marker and interpret them as a network order unsigned integer
 *
 * @copydetails fr_dbuff_out_int64v
 */
#define FR_DBUFF_OUT_INT64V_RETURN(_num, _dbuff_or_marker, _len) FR_DBUFF_RETURN(fr_dbuff_out_int64v, _num, _dbuff_or_marker, _len)

/** @} */

#ifdef __cplusplus
}
#endif

Coverage Report

Created: 2023-12-08 06:56