our current experimental Neutrino branch

git-svn-id: file:///home/bas/coolstream_public_svn/THIRDPARTY/applications/neutrino-experimental@27 e54a6e83-5905-42d5-8d5c-058d10e6a962

src/gui/ringbuffer.c

@@ -0,0 +1,308 @@
+/*
+  Copyright (C) 2000 Paul Davis
+  Copyright (C) 2003 Rohan Drape
+    
+  This program 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 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 Lesser General Public License for more details.
+    
+  You should have received a copy of the GNU Lesser General Public License
+  along with this program; if not, write to the Free Software 
+  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+    
+  ISO/POSIX C version of Paul Davis's lock free ringbuffer C++ code.
+  This is safe for the case of one read thread and one write thread.
+*/
+
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include "ringbuffer.h"
+
+/* Create a new ringbuffer to hold at least `sz' bytes of data. The
+   actual buffer size is rounded up to the next power of two.  */
+
+ringbuffer_t *
+ringbuffer_create (int sz)
+{
+  int power_of_two;
+  ringbuffer_t *rb;
+
+  rb = malloc (sizeof (ringbuffer_t));
+
+  for (power_of_two = 1; 1 << power_of_two < sz; power_of_two++);
+
+  rb->size = 1 << power_of_two;
+  rb->size_mask = rb->size;
+  rb->size_mask -= 1;
+  rb->write_ptr = 0;
+  rb->read_ptr = 0;
+  rb->buf = malloc (rb->size);
+  rb->mlocked = 0;
+printf("[ringbuffer] size %d\n", rb->size);
+  return rb;
+}
+
+/* Free all data associated with the ringbuffer `rb'. */
+
+void
+ringbuffer_free (ringbuffer_t * rb)
+{
+  if (rb->mlocked) {
+    munlock (rb->buf, rb->size);
+  }
+  free (rb->buf);
+  free (rb);
+}
+
+/* Lock the data block of `rb' using the system call 'mlock'.  */
+
+int
+ringbuffer_mlock (ringbuffer_t * rb)
+{
+  if (mlock (rb->buf, rb->size)) {
+    return -1;
+  }
+  rb->mlocked = 1;
+  return 0;
+}
+
+/* Reset the read and write pointers to zero. This is not thread
+   safe. */
+
+void
+ringbuffer_reset (ringbuffer_t * rb)
+{
+  rb->read_ptr = 0;
+  rb->write_ptr = 0;
+}
+
+/* Return the number of bytes available for reading.  This is the
+   number of bytes in front of the read pointer and behind the write
+   pointer.  */
+
+size_t
+ringbuffer_read_space (ringbuffer_t * rb)
+{
+  size_t w, r;
+
+  w = rb->write_ptr;
+  r = rb->read_ptr;
+
+  if (w > r) {
+    return w - r;
+  } else {
+    return (w - r + rb->size) & rb->size_mask;
+  }
+}
+
+/* Return the number of bytes available for writing.  This is the
+   number of bytes in front of the write pointer and behind the read
+   pointer.  */
+
+size_t
+ringbuffer_write_space (ringbuffer_t * rb)
+{
+  size_t w, r;
+
+  w = rb->write_ptr;
+  r = rb->read_ptr;
+
+  if (w > r) {
+    return ((r - w + rb->size) & rb->size_mask) - 1;
+  } else if (w < r) {
+    return (r - w) - 1;
+  } else {
+    return rb->size - 1;
+  }
+}
+
+/* The copying data reader.  Copy at most `cnt' bytes from `rb' to
+   `dest'.  Returns the actual number of bytes copied. */
+
+size_t
+ringbuffer_read (ringbuffer_t * rb, char *dest, size_t cnt)
+{
+  size_t free_cnt;
+  size_t cnt2;
+  size_t to_read;
+  size_t n1, n2;
+
+  if ((free_cnt = ringbuffer_read_space (rb)) == 0) {
+    return 0;
+  }
+
+  to_read = cnt > free_cnt ? free_cnt : cnt;
+
+  cnt2 = rb->read_ptr + to_read;
+
+  if (cnt2 > rb->size) {
+    n1 = rb->size - rb->read_ptr;
+    n2 = cnt2 & rb->size_mask;
+  } else {
+    n1 = to_read;
+    n2 = 0;
+  }
+
+  memcpy (dest, &(rb->buf[rb->read_ptr]), n1);
+  rb->read_ptr += n1;
+  rb->read_ptr &= rb->size_mask;
+
+  if (n2) {
+    memcpy (dest + n1, &(rb->buf[rb->read_ptr]), n2);
+    rb->read_ptr += n2;
+    rb->read_ptr &= rb->size_mask;
+  }
+
+  return to_read;
+}
+
+/* The copying data writer.  Copy at most `cnt' bytes to `rb' from
+   `src'.  Returns the actual number of bytes copied. */
+
+size_t
+ringbuffer_write (ringbuffer_t * rb, char *src, size_t cnt)
+{
+  size_t free_cnt;
+  size_t cnt2;
+  size_t to_write;
+  size_t n1, n2;
+
+  if ((free_cnt = ringbuffer_write_space (rb)) == 0) {
+    return 0;
+  }
+
+  to_write = cnt > free_cnt ? free_cnt : cnt;
+
+  cnt2 = rb->write_ptr + to_write;
+
+  if (cnt2 > rb->size) {
+    n1 = rb->size - rb->write_ptr;
+    n2 = cnt2 & rb->size_mask;
+  } else {
+    n1 = to_write;
+    n2 = 0;
+  }
+
+  memcpy (&(rb->buf[rb->write_ptr]), src, n1);
+  rb->write_ptr += n1;
+  rb->write_ptr &= rb->size_mask;
+
+  if (n2) {
+    memcpy (&(rb->buf[rb->write_ptr]), src + n1, n2);
+    rb->write_ptr += n2;
+    rb->write_ptr &= rb->size_mask;
+  }
+
+  return to_write;
+}
+
+/* Advance the read pointer `cnt' places. */
+
+void
+ringbuffer_read_advance (ringbuffer_t * rb, size_t cnt)
+{
+  rb->read_ptr += cnt;
+  rb->read_ptr &= rb->size_mask;
+}
+
+/* Advance the write pointer `cnt' places. */
+
+void
+ringbuffer_write_advance (ringbuffer_t * rb, size_t cnt)
+{
+  rb->write_ptr += cnt;
+  rb->write_ptr &= rb->size_mask;
+}
+
+/* The non-copying data reader.  `vec' is an array of two places.  Set
+   the values at `vec' to hold the current readable data at `rb'.  If
+   the readable data is in one segment the second segment has zero
+   length.  */
+
+void
+ringbuffer_get_read_vector (ringbuffer_t * rb,
+			    ringbuffer_data_t * vec)
+{
+  size_t free_cnt;
+  size_t cnt2;
+  size_t w, r;
+
+  w = rb->write_ptr;
+  r = rb->read_ptr;
+
+  if (w > r) {
+    free_cnt = w - r;
+  } else {
+    free_cnt = (w - r + rb->size) & rb->size_mask;
+  }
+
+  cnt2 = r + free_cnt;
+
+  if (cnt2 > rb->size) {
+
+    /* Two part vector: the rest of the buffer after the current write
+       ptr, plus some from the start of the buffer. */
+
+    vec[0].buf = &(rb->buf[r]);
+    vec[0].len = rb->size - r;
+    vec[1].buf = rb->buf;
+    vec[1].len = cnt2 & rb->size_mask;
+
+  } else {
+
+    /* Single part vector: just the rest of the buffer */
+
+    vec[0].buf = &(rb->buf[r]);
+    vec[0].len = free_cnt;
+    vec[1].len = 0;
+  }
+}
+
+/* The non-copying data writer.  `vec' is an array of two places.  Set
+   the values at `vec' to hold the current writeable data at `rb'.  If
+   the writeable data is in one segment the second segment has zero
+   length.  */
+
+void
+ringbuffer_get_write_vector (ringbuffer_t * rb,
+			     ringbuffer_data_t * vec)
+{
+  size_t free_cnt;
+  size_t cnt2;
+  size_t w, r;
+
+  w = rb->write_ptr;
+  r = rb->read_ptr;
+
+  if (w > r) {
+    free_cnt = ((r - w + rb->size) & rb->size_mask) - 1;
+  } else if (w < r) {
+    free_cnt = (r - w) - 1;
+  } else {
+    free_cnt = rb->size - 1;
+  }
+
+  cnt2 = w + free_cnt;
+
+  if (cnt2 > rb->size) {
+
+    /* Two part vector: the rest of the buffer after the current write
+       ptr, plus some from the start of the buffer. */
+
+    vec[0].buf = &(rb->buf[w]);
+    vec[0].len = rb->size - w;
+    vec[1].buf = rb->buf;
+    vec[1].len = cnt2 & rb->size_mask;
+  } else {
+    vec[0].buf = &(rb->buf[w]);
+    vec[0].len = free_cnt;
+    vec[1].len = 0;
+  }
+}