source: roaraudio/libroar/buffer.c

//buffer.c:

/*
 *      Copyright (C) Philipp 'ph3-der-loewe' Schafft - 2008-2015
 *
 *  This file is part of libroar a part of RoarAudio,
 *  a cross-platform sound system for both, home and professional use.
 *  See README for details.
 *
 *  This file is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 3
 *  as published by the Free Software Foundation.
 *
 *  libroar 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 software; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 51 Franklin Street, Fifth Floor,
 *  Boston, MA 02110-1301, USA.
 *
 *  NOTE for everyone want's to change something and send patches:
 *  read README and HACKING! There a addition information on
 *  the license of this document you need to read before you send
 *  any patches.
 *
 *  NOTE for uses of non-GPL (LGPL,...) software using libesd, libartsc
 *  or libpulse*:
 *  The libs libroaresd, libroararts and libroarpulse link this lib
 *  and are therefore GPL. Because of this it may be illigal to use
 *  them with any software that uses libesd, libartsc or libpulse*.
 */

#include "libroar.h"

struct roar_buffer_ring {
 size_t read_pos;
 size_t write_pos;
};

struct roar_buffer {
 size_t               refc;
 size_t               len;
 size_t               user_len;
 int                  flags;
 void               * data;
 void               * user_data;
 union {
  void                    * vp;
  int32_t                   i32;
  struct roar_buffer_ring   ring;
 }                    meta;
 int                  type;
 struct roar_buffer * next;
};

#define _ckbuf_free(m)  if ( buf == NULL || (m) ) { roar_err_set(ROAR_ERROR_FAULT); return -1; }
#define _ckbuf(m)       if ( _ckmem_corruption(buf, (m)) == -1 ) return -1;

// if we use the 'inline' keyword here the program segfaults. why?
static int _ckmem_corruption(volatile struct roar_buffer * buf, int m) {
 int flags;

 ROAR_DBG("_ckmem_corruption(buf=%p) = ?", buf);

 // we need to recheck here, why?
 // gcc changes the order of the above macros. why?
 // this is a strange world.
 if ( buf == NULL || m ) {
  ROAR_DBG("_ckmem_corruption(buf=%p) = -1 // FAULT", buf);
  roar_err_set(ROAR_ERROR_FAULT);
  return -1;
 }

 ROAR_DBG("_ckmem_corruption(buf=%p) = ?", buf);

 flags = buf->flags & (ROAR_BUFFER_FLAG_USEABLE|ROAR_BUFFER_FLAG_FREED);

 ROAR_DBG("_ckmem_corruption(buf=%p{.flags=0x%.4x, ...}) = ?", buf, buf->flags);

 if ( flags == ROAR_BUFFER_FLAG_USEABLE ) {
  // seems ok, continue with next check.
 } else if ( flags == ROAR_BUFFER_FLAG_FREED ) {
  roar_panic(ROAR_FATAL_ERROR_MEMORY_USED_AFTER_FREE, NULL);
  roar_err_set(ROAR_ERROR_FAULT);
  return -1;
 } else {
  roar_panic(ROAR_FATAL_ERROR_MEMORY_CORRUPTION, NULL);
  roar_err_set(ROAR_ERROR_BADCKSUM);
  return -1;
 }

 if ( buf->refc == 0 ) {
  roar_panic(ROAR_FATAL_ERROR_MEMORY_CORRUPTION, NULL);
  roar_err_set(ROAR_ERROR_FAULT);
  return -1;
 }

 return 0;
}

int roar_buffer_new_data (struct roar_buffer ** buf, size_t len, void ** data) {
 void * bufdata;
 int err;

 if ((bufdata = roar_mm_malloc(len)) == NULL) {
  return -1;
 }

 if ( roar_buffer_new_no_ma(buf, len, bufdata) == -1 ) {
  roar_mm_free_noerror(bufdata);
  return -1;
 }

 if ( roar_buffer_set_flag(*buf, ROAR_BUFFER_FLAG_NOFREE, ROAR_BUFFER_RESET) == -1 ) {
  err = roar_error;
  roar_buffer_free(*buf);
  roar_mm_free(bufdata);
  roar_err_set(err);
  return -1;
 }

 if ( data != NULL )
  *data = bufdata;

 return 0;
}

int roar_buffer_new_no_ma(struct roar_buffer ** buf, size_t len, void * data) { // no internal malloc
 struct roar_buffer * new;

 ROAR_DBG("buffer_new(buf=%p, len=%i) = ?", buf, len);

 _ckbuf_free(data == NULL)

 if ((new = roar_mm_malloc(sizeof(struct roar_buffer))) == NULL) {
  *buf = NULL;
  return -1;
 }

 new->refc      =  1;

 new->data      = data;

 new->flags     = ROAR_BUFFER_FLAG_NONE|ROAR_BUFFER_FLAG_NOFREE|ROAR_BUFFER_FLAG_USEABLE;
 new->type      = -1;

 new->user_data = new->data;

 new->next      = NULL;

 new->len       = len;
 new->user_len  = len;
 *buf           = new;

 ROAR_DBG("buffer_new(buf=%p, len=%i): New buffer at %p", buf, len, new);

 return 0;
}

int roar_buffer_new_str  (struct roar_buffer ** buf, const char * str, int terminate) {
 size_t len;
 void * data;

 if ( buf == NULL || str == NULL ) {
  roar_err_set(ROAR_ERROR_FAULT);
  return -1;
 }

 len = roar_mm_strlen(str);
 if ( terminate )
  len++;

 if ( roar_buffer_new_data(buf, len, &data) == -1 )
  return -1;

 if ( len )
  memcpy(data, str, len);
 return 0;
}

int roar_buffer_ref      (struct roar_buffer *  buf) {
 _ckbuf(0)

 buf->refc++;

 return 0;
}

int roar_buffer_unref     (struct roar_buffer * buf) {
 struct roar_buffer * next, * cur;
 int flags;

 ROAR_DBG("roar_buffer_unref(buf=%p) = ?", buf);

 _ckbuf_free(0)

 ROAR_DBG("roar_buffer_unref(buf=%p) = ?", buf);

 cur = buf;
 while (cur != NULL) {
  flags = cur->flags & (ROAR_BUFFER_FLAG_USEABLE|ROAR_BUFFER_FLAG_FREED);
  if ( flags == ROAR_BUFFER_FLAG_FREED ) {
   roar_panic(ROAR_FATAL_ERROR_MEMORY_DOUBLE_FREE, NULL);
  }

  _ckmem_corruption(cur, 0);

  if ( cur->refc == 0 ) {
   ROAR_WARN("roar_buffer_unref(buf=%p): Ref counter for buffer at %p is wrong. assuming one.", cur, cur);
   cur->refc = 1;
   roar_panic(ROAR_FATAL_ERROR_MEMORY_CORRUPTION, NULL);
  } else if ( cur->refc > 1 ) {
   cur->refc--;
   return 0;
  }

  ROAR_DBG("roar_buffer_unref(buf=%p) = ?", buf);

  if ( roar_buffer_get_flag(cur, ROAR_BUFFER_FLAG_NOFREE) != 1 )
   roar_mm_free(cur->data);

  cur->flags = ROAR_BUFFER_FLAG_FREED;
  next = cur->next;
  roar_mm_free(cur);
  cur = next;
 }

 ROAR_DBG("roar_buffer_unref(buf=%p) = 0", buf);
 return 0;
}

int roar_buffer_delete   (struct roar_buffer * buf, struct roar_buffer ** next) {
 if ( buf == NULL ) {
  if ( next != NULL )
   *next = NULL;
  roar_err_set(ROAR_ERROR_FAULT);
  return -1;
 }

 ROAR_DBG("roar_buffer_delete(buf=%p, next=%p) = ?", buf, next);

 if ( next != NULL ) {
  *next = buf;
  return roar_buffer_next(next);
 } else {
  return roar_buffer_unref(buf);
 }
}

int roar_buffer_next     (struct roar_buffer ** buf) {
 struct roar_buffer * ret;

 if ( buf == NULL || *buf == NULL ) {
  roar_err_set(ROAR_ERROR_FAULT);
 }

 ret = (*buf)->next;

 if ( ret != NULL )
  roar_buffer_ref(ret);

 roar_buffer_unref(*buf);

 *buf = ret;

 return 0;
}

int roar_buffer_add      (struct roar_buffer * buf, struct roar_buffer *  next) {
 if ( roar_buffer_ref(next) == -1 )
  return -1;
 return roar_buffer_moveinto(buf, &next);
}

int roar_buffer_moveinto (struct roar_buffer * buf, struct roar_buffer ** next) {
 unsigned int deep = 0;

 _ckbuf(next == NULL || _ckmem_corruption(*next, 0))

 ROAR_DBG("buffer_add(buf=%p, next=%p) = ?", buf, next);
 ROAR_DBG("buffer_add(buf=%p, next=%p): *next=%p", buf, next, *next);

 if ( buf->flags & ROAR_BUFFER_FLAG_RING ) {
  roar_err_set(ROAR_ERROR_INVAL);
  return -1;
 }

 if ( buf == *next ) {
  ROAR_ERR("buffer_add(*): both pointer are of the same destination, This is a error in the application");
  roar_err_set(ROAR_ERROR_INVAL);
  return -1;
 }

 while ( buf->next != NULL ) {
  ROAR_DBG("buffer_add(*): buf=%p, next=%p (len=%i)", buf, buf->next, buf->user_len);
//  ROAR_DBG("buffer_add(): buf=%p, buf->next=%p", buf, buf->next);
  buf = buf->next;
  deep++;

  if ( buf == *next ) {
   ROAR_ERR("buffer_add(*): Can not add buffer: loop detected at deep %u. This is a error in the application", deep);
   // why don't we return here?
  }
 }

 buf->next = *next;

 ROAR_DBG("buffer_add(*): adding buffer at deep %u", deep);

 *next = NULL;

 return 0;
}

int roar_buffer_moveintoqueue(struct roar_buffer ** buf, struct roar_buffer ** next) {
 if ( buf == NULL || next == NULL ) {
  roar_err_set(ROAR_ERROR_FAULT);
  return -1;
 }

 if ( *buf == NULL ) {
  *buf = *next;
  *next = NULL;
  return 0;
 } else {
  return roar_buffer_moveinto(*buf, next);
 }
}

int roar_buffer_get_next (struct roar_buffer *  buf, struct roar_buffer ** next) {
 _ckbuf(0)

 *next = buf->next;

 return roar_buffer_ref(*next);
}

int roar_buffer_ring_new (struct roar_buffer ** buf, size_t len, int free_running) {
 struct roar_buffer * n;

 _ckbuf_free(0)

 if ( len == 0 ) {
  roar_err_set(ROAR_ERROR_RANGE);
  return -1;
 }

 // just to be sure:
 *buf = NULL;

 if ( roar_buffer_new(&n, len) == -1 )
  return -1;

 n->flags |= ROAR_BUFFER_FLAG_RING;

 if ( free_running )
  n->flags |= ROAR_BUFFER_FLAG_FREE_RUNNING;

 n->meta.ring.read_pos  = 0;
 n->meta.ring.write_pos = 0;

 memset(n->data, 0, n->len);

 *buf = n;

 return 0;
}

int roar_buffer_get_data (struct roar_buffer *  buf, void   ** data) {
 _ckbuf(data == NULL)

 *data = buf->user_data;

 return 0;
}

int roar_buffer_get_datalen(struct roar_buffer * buf, void   ** data, size_t * len) {
 _ckbuf(0)

 if ( data != NULL )
  *data = buf->user_data;
 if ( len != NULL )
 *len = buf->user_len;

 return 0;
}

int roar_buffer_set_offset (struct roar_buffer *  buf, size_t off) {
 _ckbuf(0)

 if ( off > buf->user_len ) {
  roar_err_set(ROAR_ERROR_RANGE);
  return -1;
 }

 buf->user_len  -= off;
 buf->user_data += off;

 return 0;
}

int roar_buffer_shift_out (struct roar_buffer ** buf, void * data, size_t * len) {
 size_t todo, cl;
 struct roar_buffer * cur;
 void * cd;

 _ckbuf_free(len == NULL || data == NULL);

 if ( *buf == NULL ) {
  ROAR_DBG("roar_buffer_shift_out(buf=%p, data=%p, len={%lu}) = -1 // Invalid pointer to buffer ring", buf, data, (unsigned long)len);
  roar_err_set(ROAR_ERROR_FAULT);
  return -1;
 }

 todo = *len;
 cur  = *buf;

 *len = 0;

 while (todo && cur != NULL) {
  ROAR_DBG("roar_buffer_shift_out(*): todo=%u, cur=%p", (unsigned int) todo, cur);

  _ckmem_corruption(cur, 0);

  if ( roar_buffer_get_len(cur, &cl) == -1 )
   return -1;

  if ( cl > todo ) {
   if ( roar_buffer_get_data(cur, &cd) == -1 )
    return -1;

   cl = todo;

   memcpy(data, cd, cl);
   todo -= cl;
   data += cl;
   *len += cl;

   if ( roar_buffer_set_offset(cur, cl) == -1 )
    return -1;
  } else {
   if ( roar_buffer_get_data(cur, &cd) == -1 )
    return -1;

   memcpy(data, cd, cl);
   todo -= cl;
   data += cl;
   *len += cl;

   if ( roar_buffer_next(&cur) == -1 )
    return -1;
  }

/*
  if ( cur == NULL )
   break;
*/
 }

 *buf = cur;

 return 0;
}

int roar_buffer_set_meta (struct roar_buffer * buf, void *  meta) {
 _ckbuf(0)

 buf->meta.vp = meta;

 return 0;
}

int roar_buffer_get_meta (struct roar_buffer * buf, void ** meta) {
 _ckbuf(meta == NULL)

 *meta = buf->meta.vp;

 return 0;
}

int roar_buffer_set_meta_i32(struct roar_buffer *  buf, int32_t    meta) {
 _ckbuf(0)

 buf->meta.i32 = meta;

 return 0;
}

int roar_buffer_get_meta_i32(struct roar_buffer *  buf, int32_t *  meta) {
 _ckbuf(meta == NULL)

 *meta = buf->meta.i32;

 return 0;
}

int roar_buffer_set_type    (struct roar_buffer *  buf, int        type) {
 _ckbuf(0)

 switch (type) {
  case ROAR_VIO_DFT_RAW:
  case ROAR_VIO_DFT_PACKET:
  case ROAR_VIO_DFT_UNFRAMED:
  case ROAR_VIO_DFT_OGG_PACKET:
  case ROAR_VIO_DFT_OGG_PAGE:
   break;
  default:
    roar_err_set(ROAR_ERROR_NOTSUP);
    return -1;
 }

 buf->type = type;

 return 0;
}

int roar_buffer_get_type    (struct roar_buffer *  buf, int     *  type) {
 _ckbuf(type == NULL)

 *type = buf->type;

 return 0;
}

int roar_buffer_set_len  (struct roar_buffer *  buf, size_t    len) {
 size_t   totlen;
 void   * newbuf;
 size_t true_len;

 ROAR_DBG("roar_buffer_set_len(buf=%p, len=%lu) = ?", buf, (long unsigned int)len);

 _ckbuf(0)

 ROAR_DBG("roar_buffer_set_len(buf=%p, len=%lu) = ?", buf, (long unsigned int)len);

 // handle special case where user length is zero:
 if ( len && !buf->user_len ) {
  buf->user_data = buf->data;
  buf->user_len  = buf->len;
 }

 ROAR_DBG("roar_buffer_set_len(buf=%p, len=%lu) = ?", buf, (long unsigned int)len);

 // calculate the true length of our buffer starting at buf->user_data.
 true_len = buf->len - (buf->user_data - buf->data);

 if ( len > true_len ) {
  ROAR_DBG("roar_buffer_set_len(buf=%p, len=%lu): We need to enlarge the buffer.", buf, (long unsigned int)len);

  // we can only enlage a buffer if it's one of our own memory segments
  if ( buf->flags & ROAR_BUFFER_FLAG_NOFREE )  {
   ROAR_DBG("roar_buffer_set_len(buf=%p, len=%lu) = -1 //error=NOTSUP", buf, (long unsigned int)len);
   roar_err_set(ROAR_ERROR_NOTSUP);
   return -1;
  }

  totlen = (buf->len - buf->user_len) + len;
  newbuf = roar_mm_realloc(buf->data, totlen);
  if ( newbuf == NULL )
   return -1;

  buf->user_data = newbuf + (buf->user_data - buf->data);
  buf->user_len = len;
  buf->data = newbuf;
  buf->len  = totlen;
 } else {
  ROAR_DBG("roar_buffer_set_len(buf=%p, len=%lu): No need to enlarge the buffer.", buf, (long unsigned int)len);
  buf->user_len = len;
 }

 ROAR_DBG("roar_buffer_set_len(buf=%p, len=%lu) = 0", buf, (long unsigned int)len);
 return 0;
}

int roar_buffer_get_len  (struct roar_buffer *  buf, size_t *  len) {
 _ckbuf(0)

 *len = buf->user_len;

 return 0;
}

int roar_buffer_set_flag (struct roar_buffer *  buf, int flag, int reset) {
 _ckbuf(0)

 buf->flags |= flag;

 if ( reset )
  buf->flags -= flag;

 return 0;
}

int roar_buffer_get_flag (struct roar_buffer *  buf, int flag) {
 _ckbuf(0)

 return buf->flags & flag;
}

int roar_buffer_duplicate (struct roar_buffer *  buf, struct roar_buffer ** copy) {
 struct roar_buffer *  cur = buf;
 struct roar_buffer *  new;
 void * od, * nd;
 int err;

 _ckbuf(copy == NULL)

 *copy = NULL;

 // TODO:  This function does not handle ring buffers.
 // FIXME: This function does not error out in case of wrong buffer type in buf.
 // TODO:  This function does not handle buffer meta data.

 while (cur != NULL) {
  if ( roar_buffer_new(&new, cur->user_len) == -1 ) {
   err = roar_error;
   roar_buffer_free(*copy);
   roar_err_set(err);
   return -1;
  }

  if ( *copy == NULL )
   *copy = new;

  _LIBROAR_IGNORE_RET(roar_buffer_get_data(cur, &od));
  _LIBROAR_IGNORE_RET(roar_buffer_get_data(new, &nd));
  memcpy(nd, od, cur->user_len);

  if ( *copy != new ) {
   _LIBROAR_IGNORE_RET(roar_buffer_moveinto(*copy, &new));
  }

  cur = cur->next;
 }

 return 0;
}

int roar_buffer_ring_stats (struct roar_buffer *  buf, struct roar_buffer_stats * stats) {
 ROAR_DBG("roar_buffer_ring_stats(buf=%p, stats=%p) = ?", buf, stats);

 _ckbuf(0)

 ROAR_DBG("roar_buffer_ring_stats(buf=%p, stats=%p) = ?", buf, stats);

 stats->parts        = 0;
 stats->bytes        = 0;
 stats->memory_usage = 0;

 while (buf != NULL ) {
  stats->parts++;
  stats->bytes        += buf->user_len;
  stats->memory_usage += buf->len + sizeof(struct roar_buffer);
  buf = buf->next;
 }

 return 0;
}

int roar_buffer_ring_read  (struct roar_buffer *  buf, void * data, size_t * len) {
 struct roar_buffer_ring * ring;
 size_t havelen;
 size_t done;
 size_t tmp;

 _ckbuf(len == NULL)

 if ( buf == NULL || len == NULL )
  return -1;

 if ( data == NULL && *len != 0 ) {
  roar_err_set(ROAR_ERROR_FAULT);
  return -1;
 }

 if ( !(buf->flags & ROAR_BUFFER_FLAG_RING) ) {
  roar_err_set(ROAR_ERROR_TYPEMM);
  return -1;
 }

 if ( *len == 0 )
  return 0;

 // we may handle this later:
 if ( *len > buf->user_len ) {
  roar_err_set(ROAR_ERROR_NOTSUP);
  return -1;
 }

 if ( (buf->flags & ROAR_BUFFER_FLAG_FREE_RUNNING) ) {
  if ( buf->meta.ring.read_pos >= buf->user_len )
   buf->meta.ring.read_pos -= buf->user_len;

  if ( (*len + buf->meta.ring.read_pos) > buf->user_len ) {
   // wraped mode:
   memcpy(data, buf->user_data+buf->meta.ring.read_pos, buf->user_len - buf->meta.ring.read_pos);
   memcpy(data, buf->user_data, *len + buf->meta.ring.read_pos - buf->user_len);
 
   buf->meta.ring.read_pos += *len;
   buf->meta.ring.read_pos -= buf->user_len;
   return 0;
  } else {
   // unwarped mode:
   memcpy(data, buf->user_data+buf->meta.ring.read_pos, *len);
   buf->meta.ring.read_pos += *len;
   return 0;
  }
 } else {
  ring = &(buf->meta.ring);

  if ( ring->read_pos == ring->write_pos ) {
   *len = 0;
   return 0;
  } else if ( ring->read_pos < ring->write_pos ) {
   havelen = ring->write_pos - ring->read_pos;

   if ( havelen > *len )
    havelen = *len;

   memcpy(data, buf->user_data+ring->read_pos, havelen);
   ring->read_pos += havelen;

   *len = havelen;
   return 0;
  } else { // write_pos < read_pos
   done = 0;

   // first pass: use data up to end of buffer

   havelen = buf->user_len - ring->read_pos;

   if ( havelen > *len )
    havelen = *len;

   memcpy(data, buf->user_data+ring->read_pos, havelen);
   ring->read_pos += havelen;

   done += havelen;

   if ( ring->read_pos == buf->user_len ) {
    ring->read_pos = 0;
   }

   // second pass: use data from strat of buffer to write pointer

   if ( *len > done ) {
    tmp = *len - done;
    if ( roar_buffer_ring_read(buf, data+done, &tmp) == 0 ) {
     done += tmp;
    }
   }

   *len = done;
   return 0;
  }
 }

 roar_err_set(ROAR_ERROR_UNKNOWN);
 return -1;
}

int roar_buffer_ring_write (struct roar_buffer *  buf, void * data, size_t * len) {
 struct roar_buffer_ring * ring;
 size_t havelen;
 size_t done;
 size_t tmp;

 ROAR_DBG("roar_buffer_ring_write(buf=%p, data=%p, len=%p) = ?", buf, data, len);

 _ckbuf(len == NULL)

 if ( data == NULL && *len != 0 ) {
  roar_err_set(ROAR_ERROR_FAULT);
  return -1;
 }

 if ( !(buf->flags & ROAR_BUFFER_FLAG_RING) ) {
  roar_err_set(ROAR_ERROR_TYPEMM);
  return -1;
 }

 if ( *len == 0 )
  return 0;

 // we may handle this later:
 if ( *len > buf->user_len ) {
  roar_err_set(ROAR_ERROR_NOTSUP);
  return -1;
 }

 if ( (buf->flags & ROAR_BUFFER_FLAG_FREE_RUNNING) ) {
  if ( buf->meta.ring.write_pos >= buf->user_len )
   buf->meta.ring.write_pos -= buf->user_len;

  if ( (*len + buf->meta.ring.write_pos) > buf->user_len ) {
   // wraped mode:
   memcpy(buf->user_data+buf->meta.ring.write_pos, data, buf->user_len - buf->meta.ring.write_pos);
   memcpy(buf->user_data, data, *len + buf->meta.ring.write_pos - buf->user_len);

   buf->meta.ring.write_pos += *len;
   buf->meta.ring.write_pos -= buf->user_len;
   return 0;
  } else {
   // unwarped mode:
   memcpy(buf->user_data+buf->meta.ring.write_pos, data, *len);
   buf->meta.ring.write_pos += *len;
   return 0;
  }
 } else {
  ring = &(buf->meta.ring);
  done = 0;

  ROAR_DBG("roar_buffer_ring_write(buf=%p, data=%p, len=%p): write_pos=%u, read_pos=%u, user_len=%u", buf, data, len, (unsigned int)ring->write_pos, (unsigned int)ring->read_pos, (unsigned int)buf->user_len);

  if ( ring->write_pos >= ring->read_pos ) {
   ROAR_DBG("roar_buffer_ring_write(buf=%p, data=%p, len=%p) = ?", buf, data, len);

   havelen = buf->user_len - ring->write_pos;

   if ( ring->read_pos == 0 )
    havelen--;

   if ( havelen > *len )
    havelen = *len;

   memcpy(buf->user_data+ring->write_pos, data, havelen);

   done += havelen;
   ring->write_pos += havelen;

   if ( ring->write_pos == buf->user_len )
    ring->write_pos = 0;

   if ( *len > done && ring->read_pos != 0 ) {
    tmp = *len - done;
    if ( roar_buffer_ring_write(buf, data+done, &tmp) == 0 ) {
     done += tmp;
    }
   }

   *len = done;
   ROAR_DBG("roar_buffer_ring_write(buf=%p, data=%p, len=%p) = 0", buf, data, len);
   return 0;
  } else {
   ROAR_DBG("roar_buffer_ring_write(buf=%p, data=%p, len=%p) = ?", buf, data, len);

   // test for buffer-is-full:
   if ( (ring->write_pos + 1) == ring->read_pos ) {
    *len = 0;
    ROAR_DBG("roar_buffer_ring_write(buf=%p, data=%p, len=%p) = 0", buf, data, len);
    return 0;
   }

   ROAR_DBG("roar_buffer_ring_write(buf=%p, data=%p, len=%p) = ?", buf, data, len);

   havelen = ring->read_pos - ring->write_pos - 1;

   if ( havelen > *len )
    havelen = *len;

   memcpy(buf->user_data+ring->write_pos, data, havelen);

   ring->write_pos += havelen;
   *len = havelen;

   ROAR_DBG("roar_buffer_ring_write(buf=%p, data=%p, len=%p) = 0", buf, data, len);
   return 0;
  }
 }

 roar_err_set(ROAR_ERROR_UNKNOWN);
 return -1;
}

int roar_buffer_ring_avail(struct roar_buffer *  buf, size_t * readlen, size_t * writelen) {
 struct roar_buffer_ring * ring;
 size_t have;

 _ckbuf(0)

 if ( !(buf->flags & ROAR_BUFFER_FLAG_RING) ) {
  roar_err_set(ROAR_ERROR_TYPEMM);
  return -1;
 }

 ring = &(buf->meta.ring);

 ROAR_DBG("roar_buffer_ring_avail(buf=%p, readlen=%p, writelen=%p) = ?", buf, readlen, writelen);

 if ( readlen != NULL ) {
  have = 0;

  if ( ring->write_pos >= ring->read_pos ) {
   have  = ring->write_pos - ring->read_pos;
  } else {
   have  = buf->user_len - ring->read_pos;
   have += ring->write_pos;
   have -= 1;
  }

  *readlen = have;
  ROAR_DBG("roar_buffer_ring_avail(buf=%p, readlen=%p, writelen=%p): readlen=%llu", buf, readlen, writelen, (unsigned long long int)have);
 }

 if ( writelen != NULL ) {
  have = 0;

  if ( ring->read_pos > ring->write_pos ) {
   have  = ring->read_pos - ring->write_pos - 1;
  } else {
   have  = buf->user_len - ring->write_pos;
   have += ring->read_pos;
   have -= 1;
  }

  *writelen = have;
  ROAR_DBG("roar_buffer_ring_avail(buf=%p, readlen=%p, writelen=%p): readlen=%llu", buf, readlen, writelen, (unsigned long long int)have);
 }

 ROAR_DBG("roar_buffer_ring_avail(buf=%p, readlen=%p, writelen=%p) = 0", buf, readlen, writelen);

 return 0;
}

int roar_buffer_ring_reset(struct roar_buffer *  buf) {
 _ckbuf(0)

 if ( !(buf->flags & ROAR_BUFFER_FLAG_RING) ) {
  roar_err_set(ROAR_ERROR_TYPEMM);
  return -1;
 }

 buf->meta.ring.read_pos = buf->meta.ring.write_pos = 0;

 return 0;
}

//ll