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Posted to commits@nuttx.apache.org by xi...@apache.org on 2020/11/20 13:33:15 UTC
[incubator-nuttx] 01/02: mm/circbuf: support circular buffer
managerment
This is an automated email from the ASF dual-hosted git repository.
xiaoxiang pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/incubator-nuttx.git
commit 23ddeaf3be530cd8faa7e7077fa9ea7caa83d708
Author: dongjiuzhu <do...@xiaomi.com>
AuthorDate: Thu Nov 12 18:40:06 2020 +0800
mm/circbuf: support circular buffer managerment
N/A
Change-Id: Ib1fc009b9ce3af5815920f22221fe8a7262299ef
Signed-off-by: dongjiuzhu <do...@xiaomi.com>
---
include/nuttx/mm/circbuf.h | 308 +++++++++++++++++++++++++++++
mm/Kconfig | 6 +
mm/Makefile | 1 +
mm/circbuf/Make.defs | 30 +++
mm/circbuf/circbuf.c | 474 +++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 819 insertions(+)
diff --git a/include/nuttx/mm/circbuf.h b/include/nuttx/mm/circbuf.h
new file mode 100644
index 0000000..c6d291c
--- /dev/null
+++ b/include/nuttx/mm/circbuf.h
@@ -0,0 +1,308 @@
+/****************************************************************************
+ * include/nuttx/mm/circbuf.h
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership. The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_MM_CIRCBUF_H
+#define __INCLUDE_NUTTX_MM_CIRCBUF_H
+
+/* Note about locking: There is no locking required while only one reader
+ * and one writer is using the circular buffer.
+ * For multiple writer and one reader there is only a need to lock the
+ * writer. And vice versa for only one writer and multiple reader there is
+ * only a need to lock the reader.
+ */
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <stdbool.h>
+#include <sys/types.h>
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+/* This structure describes circular buffer */
+
+struct circbuf_s
+{
+ FAR void *base; /* The pointer to buffer space */
+ size_t size; /* The size of buffer space */
+ size_t head; /* The head of buffer space */
+ size_t tail; /* The tail of buffer space */
+ bool external; /* The flag for external buffer */
+};
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+#undef EXTERN
+#if defined(__cplusplus)
+#define EXTERN extern "C"
+extern "C"
+{
+#else
+#define EXTERN extern
+#endif
+
+/****************************************************************************
+ * Name: circbuf_init
+ *
+ * Description:
+ * Initialize a circular buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * base - A pointer to circular buffer's internal buffer. It can be
+ * provided by caller because sometimes the creation of buffer
+ * is special or needs to preallocated, eg: DMA buffer.
+ * If NULL, a buffer of the given size will be allocated.
+ * bytes - The size of the internal buffer.
+ *
+ * Returned Value:
+ * Zero on success; A negated errno value is returned on any failure.
+ *
+ ****************************************************************************/
+
+int circbuf_init(FAR struct circbuf_s *circ,
+ FAR void *base, size_t bytes);
+
+/****************************************************************************
+ * Name: circbuf_resize
+ *
+ * Description:
+ * Resize a circular buffer (change buffer size).
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * bytes - The size of the internal buffer.
+ *
+ * Returned Value:
+ * Zero on success; A negated errno value is returned on any failure.
+ *
+ ****************************************************************************/
+
+int circbuf_resize(FAR struct circbuf_s *circ, size_t bytes);
+
+/****************************************************************************
+ * Name: circbuf_uninit
+ *
+ * Description:
+ * Free the circular buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+void circbuf_uninit(FAR struct circbuf_s *circ);
+
+/****************************************************************************
+ * Name: circbuf_reset
+ *
+ * Description:
+ * Remove the entire circular buffer content.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+void circbuf_reset(FAR struct circbuf_s *circ);
+
+/****************************************************************************
+ * Name: circbuf_is_full
+ *
+ * Description:
+ * Return true if the circular buffer is full.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+bool circbuf_is_full(FAR struct circbuf_s *circ);
+
+/****************************************************************************
+ * Name: circbuf_is_empty
+ *
+ * Description:
+ * Return true if the circular buffer is empty.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+bool circbuf_is_empty(FAR struct circbuf_s *circ);
+
+/****************************************************************************
+ * Name: circbuf_size
+ *
+ * Description:
+ * Return size of the circular buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+size_t circbuf_size(FAR struct circbuf_s *circ);
+
+/****************************************************************************
+ * Name: circbuf_used
+ *
+ * Description:
+ * Return the used bytes of the circular buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+size_t circbuf_used(FAR struct circbuf_s *circ);
+
+/****************************************************************************
+ * Name: circbuf_space
+ *
+ * Description:
+ * Return the remaing space of the circular buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+size_t circbuf_space(FAR struct circbuf_s *circ);
+
+/****************************************************************************
+ * Name: circbuf_peek
+ *
+ * Description:
+ * Get data form the circular buffer without removing
+ *
+ * Note :
+ * That with only one concurrent reader and one concurrent writer,
+ * you don't need extra locking to use these api.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * dst - Address where to store the data.
+ * bytes - Number of bytes to get.
+ *
+ * Returned Value:
+ * The bytes of get data is returned if the peek data is successful;
+ * A negated errno value is returned on any failure.
+ ****************************************************************************/
+
+ssize_t circbuf_peek(FAR struct circbuf_s *circ,
+ FAR void *dst, size_t bytes);
+
+/****************************************************************************
+ * Name: circbuf_read
+ *
+ * Description:
+ * Get data form the circular buffer.
+ *
+ * Note :
+ * That with only one concurrent reader and one concurrent writer,
+ * you don't need extra locking to use these api.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * dst - Address where to store the data.
+ * bytes - Number of bytes to get.
+ *
+ * Returned Value:
+ * The bytes of get data is returned if the read data is successful;
+ * A negated errno value is returned on any failure.
+ ****************************************************************************/
+
+ssize_t circbuf_read(FAR struct circbuf_s *circ,
+ FAR void *dst, size_t bytes);
+
+/****************************************************************************
+ * Name: circbuf_skip
+ *
+ * Description:
+ * Skip data form the circular buffer.
+ *
+ * Note:
+ * That with only one concurrent reader and one concurrent writer,
+ * you don't need extra locking to use these api.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * bytes - Number of bytes to skip.
+ *
+ * Returned Value:
+ * The bytes of get data is returned if the skip data is successful;
+ * A negated errno value is returned on any failure.
+ ****************************************************************************/
+
+ssize_t circbuf_skip(FAR struct circbuf_s *circ, size_t bytes);
+
+/****************************************************************************
+ * Name: circbuf_write
+ *
+ * Description:
+ * Write data to the circular buffer.
+ *
+ * Note:
+ * That with only one concurrent reader and one concurrent writer,
+ * you don't need extra locking to use these api.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * src - The data to be added.
+ * bytes - Number of bytes to be added.
+ *
+ * Returned Value:
+ * The bytes of get data is returned if the write data is successful;
+ * A negated errno value is returned on any failure.
+ ****************************************************************************/
+
+ssize_t circbuf_write(FAR struct circbuf_s *circ,
+ FAR const void *src, size_t bytes);
+
+/****************************************************************************
+ * Name: circbuf_overwrite
+ *
+ * Description:
+ * Write data to the circular buffer. It can overwrite old data when
+ * circular buffer don't have enough space to store data.
+ *
+ * Note:
+ * Usage circbuf_overwrite () is dangerous. It should be only called
+ * when the buffer is exclusived locked or when it is secured that no
+ * other thread is accessing the buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * src - The data to be added.
+ * bytes - Number of bytes to be added.
+ *
+ * Returned Value:
+ * The bytes length of overwrite is returned if it's successful;
+ * A negated errno value is returned on any failure.
+ ****************************************************************************/
+
+ssize_t circbuf_overwrite(FAR struct circbuf_s *circ,
+ FAR const void *src, size_t bytes);
+
+#undef EXTERN
+#if defined(__cplusplus)
+}
+#endif
+#endif
diff --git a/mm/Kconfig b/mm/Kconfig
index e4b8170..788ae47 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -155,4 +155,10 @@ config MM_FILL_ALLOCATIONS
Fill all malloc() allocations with 0xAA. This helps
detecting uninitialized variable errors.
+config MM_CIRCBUF
+ bool "Circular buffer support"
+ default n
+ ---help---
+ Build in support for the circular buffer management.
+
source "mm/iob/Kconfig"
diff --git a/mm/Makefile b/mm/Makefile
index b08ad3a..ae04d19 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -43,6 +43,7 @@ include kmm_heap/Make.defs
include mm_gran/Make.defs
include shm/Make.defs
include iob/Make.defs
+include circbuf/Make.defs
BINDIR ?= bin
diff --git a/mm/circbuf/Make.defs b/mm/circbuf/Make.defs
new file mode 100644
index 0000000..1d71c24
--- /dev/null
+++ b/mm/circbuf/Make.defs
@@ -0,0 +1,30 @@
+############################################################################
+# mm/circbuf/Make.defs
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership. The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+# Circular buffer management
+
+ifeq ($(CONFIG_MM_CIRCBUF),y)
+CSRCS += circbuf.c
+
+# Add the circular buffer directory to the build
+
+DEPPATH += --dep-path circbuf
+VPATH += :circbuf
+endif
diff --git a/mm/circbuf/circbuf.c b/mm/circbuf/circbuf.c
new file mode 100644
index 0000000..cef8e13
--- /dev/null
+++ b/mm/circbuf/circbuf.c
@@ -0,0 +1,474 @@
+/****************************************************************************
+ * mm/circbuf/circbuf.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership. The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/* Note about locking: There is no locking required while only one reader
+ * and one writer is using the circular buffer.
+ * For multiple writer and one reader there is only a need to lock the
+ * writer. And vice versa for only one writer and multiple reader there is
+ * only a need to lock the reader.
+ */
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/mm/circbuf.h>
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: circbuf_init
+ *
+ * Description:
+ * Initialize a circular buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * base - A pointer to circular buffer's internal buffer. It can be
+ * provided by caller because sometimes the creation of buffer
+ * is special or needs to preallocated, eg: DMA buffer.
+ * If NULL, a buffer of the given size will be allocated.
+ * bytes - The size of the internal buffer.
+ *
+ * Returned Value:
+ * Zero on success; A negated errno value is returned on any failure.
+ *
+ ****************************************************************************/
+
+int circbuf_init(FAR struct circbuf_s *circ, FAR void *base, size_t bytes)
+{
+ DEBUGASSERT(circ);
+ DEBUGASSERT(!base || bytes);
+
+ circ->external = !!base;
+
+ if (!base && bytes)
+ {
+ base = kmm_malloc(bytes);
+ if (!base)
+ {
+ return -ENOMEM;
+ }
+ }
+
+ circ->base = base;
+ circ->size = bytes;
+ circ->head = 0;
+ circ->tail = 0;
+
+ return 0;
+}
+
+/****************************************************************************
+ * Name: circbuf_resize
+ *
+ * Description:
+ * Resize a circular buffer (change buffer size).
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * bytes - The size of the internal buffer.
+ *
+ * Returned Value:
+ * Zero on success; A negated errno value is returned on any failure.
+ *
+ ****************************************************************************/
+
+int circbuf_resize(FAR struct circbuf_s *circ, size_t bytes)
+{
+ FAR void *tmp;
+ size_t len;
+
+ DEBUGASSERT(circ);
+ DEBUGASSERT(!circ->external);
+
+ tmp = kmm_malloc(bytes);
+ if (!tmp)
+ {
+ return -ENOMEM;
+ }
+
+ len = circbuf_used(circ);
+ if (bytes < len)
+ {
+ circbuf_skip(circ, len - bytes);
+ len = bytes;
+ }
+
+ circbuf_read(circ, tmp, len);
+
+ kmm_free(circ->base);
+
+ circ->base = tmp;
+ circ->size = bytes;
+ circ->head = len;
+ circ->tail = 0;
+
+ return 0;
+}
+
+/****************************************************************************
+ * Name: circbuf_reset
+ *
+ * Description:
+ * Remove the entire circular buffer content.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+void circbuf_reset(FAR struct circbuf_s *circ)
+{
+ DEBUGASSERT(circ);
+ circ->head = circ->tail = 0;
+}
+
+/****************************************************************************
+ * Name: circbuf_uninit
+ *
+ * Description:
+ * Free the circular buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+void circbuf_uninit(FAR struct circbuf_s *circ)
+{
+ DEBUGASSERT(circ);
+
+ if (!circ->external)
+ {
+ kmm_free(circ->base);
+ }
+
+ memset(circ, 0, sizeof(*circ));
+}
+
+/****************************************************************************
+ * Name: circbuf_size
+ *
+ * Description:
+ * Return size of the circular buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+size_t circbuf_size(FAR struct circbuf_s *circ)
+{
+ DEBUGASSERT(circ);
+ return circ->size;
+}
+
+/****************************************************************************
+ * Name: circbuf_used
+ *
+ * Description:
+ * Return the used bytes of the circular buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+size_t circbuf_used(FAR struct circbuf_s *circ)
+{
+ DEBUGASSERT(circ);
+ return circ->head - circ->tail;
+}
+
+/****************************************************************************
+ * Name: circbuf_space
+ *
+ * Description:
+ * Return the remaing space of the circular buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+size_t circbuf_space(FAR struct circbuf_s *circ)
+{
+ return circbuf_size(circ) - circbuf_used(circ);
+}
+
+/****************************************************************************
+ * Name: circbuf_is_empty
+ *
+ * Description:
+ * Return true if the circular buffer is empty.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+bool circbuf_is_empty(FAR struct circbuf_s *circ)
+{
+ return !circbuf_used(circ);
+}
+
+/****************************************************************************
+ * Name: circbuf_is_full
+ *
+ * Description:
+ * Return true if the circular buffer is full.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ ****************************************************************************/
+
+bool circbuf_is_full(FAR struct circbuf_s *circ)
+{
+ return !circbuf_space(circ);
+}
+
+/****************************************************************************
+ * Name: circbuf_peek
+ *
+ * Description:
+ * Get data form the circular buffer without removing
+ *
+ * Note :
+ * That with only one concurrent reader and one concurrent writer,
+ * you don't need extra locking to use these api.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * dst - Address where to store the data.
+ * bytes - Number of bytes to get.
+ *
+ * Returned Value:
+ * The bytes of get data is returned if the peek data is successful;
+ * A negated errno value is returned on any failure.
+ ****************************************************************************/
+
+ssize_t circbuf_peek(FAR struct circbuf_s *circ,
+ FAR void *dst, size_t bytes)
+{
+ size_t len;
+ size_t off;
+
+ DEBUGASSERT(circ);
+
+ len = circbuf_used(circ);
+ off = circ->tail % circ->size;
+
+ if (bytes > len)
+ {
+ bytes = len;
+ }
+
+ len = circ->size - off;
+ if (bytes < len)
+ {
+ len = bytes;
+ }
+
+ memcpy(dst, circ->base + off, len);
+ memcpy(dst + len, circ->base, bytes - len);
+
+ return bytes;
+}
+
+/****************************************************************************
+ * Name: circbuf_read
+ *
+ * Description:
+ * Get data form the circular buffer.
+ *
+ * Note :
+ * That with only one concurrent reader and one concurrent writer,
+ * you don't need extra locking to use these api.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * dst - Address where to store the data.
+ * bytes - Number of bytes to get.
+ *
+ * Returned Value:
+ * The bytes of get data is returned if the read data is successful;
+ * A negated errno value is returned on any failure.
+ ****************************************************************************/
+
+ssize_t circbuf_read(FAR struct circbuf_s *circ,
+ FAR void *dst, size_t bytes)
+{
+ DEBUGASSERT(circ);
+ DEBUGASSERT(dst || !bytes);
+
+ bytes = circbuf_peek(circ, dst, bytes);
+ circ->tail += bytes;
+
+ return bytes;
+}
+
+/****************************************************************************
+ * Name: circbuf_skip
+ *
+ * Description:
+ * Skip data form the circular buffer.
+ *
+ * Note :
+ * That with only one concurrent reader and one concurrent writer,
+ * you don't need extra locking to use these api.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * bytes - Number of bytes to skip.
+ *
+ * Returned Value:
+ * The bytes of get data is returned if the skip data is successful;
+ * A negated errno value is returned on any failure.
+ ****************************************************************************/
+
+ssize_t circbuf_skip(FAR struct circbuf_s *circ, size_t bytes)
+{
+ size_t len;
+
+ DEBUGASSERT(circ);
+
+ len = circbuf_used(circ);
+
+ if (bytes > len)
+ {
+ bytes = len;
+ }
+
+ circ->tail += bytes;
+
+ return bytes;
+}
+
+/****************************************************************************
+ * Name: circbuf_write
+ *
+ * Description:
+ * Write data to the circular buffer.
+ *
+ * Note :
+ * That with only one concurrent reader and one concurrent writer,
+ * you don't need extra locking to use these api.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * src - The data to be added.
+ * bytes - Number of bytes to be added.
+ *
+ * Returned Value:
+ * The bytes of get data is returned if the write data is successful;
+ * A negated errno value is returned on any failure.
+ ****************************************************************************/
+
+ssize_t circbuf_write(FAR struct circbuf_s *circ,
+ FAR const void *src, size_t bytes)
+{
+ size_t space;
+ size_t off;
+
+ DEBUGASSERT(circ);
+ DEBUGASSERT(src || !bytes);
+
+ space = circbuf_space(circ);
+ off = circ->head % circ->size;
+ if (bytes > space)
+ {
+ bytes = space;
+ }
+
+ space = circ->size - off;
+ if (bytes < space)
+ {
+ space = bytes;
+ }
+
+ memcpy(circ->base + off, src, space);
+ memcpy(circ->base, src + space, bytes - space);
+ circ->head += bytes;
+
+ return bytes;
+}
+
+/****************************************************************************
+ * Name: circbuf_overwrite
+ *
+ * Description:
+ * Write data to the circular buffer. It can overwrite old data when
+ * circular buffer don't have enough space to store data.
+ *
+ * Note:
+ * Usage circbuf_overwrite () is dangerous. It should be only called
+ * when the buffer is exclusived locked or when it is secured that no
+ * other thread is accessing the buffer.
+ *
+ * Input Parameters:
+ * circ - Address of the circular buffer to be used.
+ * src - The data to be added.
+ * bytes - Number of bytes to be added.
+ *
+ * Returned Value:
+ * The bytes length of overwrite is returned if it's successful;
+ * A negated errno value is returned on any failure.
+ ****************************************************************************/
+
+ssize_t circbuf_overwrite(FAR struct circbuf_s *circ,
+ FAR const void *src, size_t bytes)
+{
+ size_t overwrite = 0;
+ size_t space;
+ size_t off;
+
+ DEBUGASSERT(circ);
+ DEBUGASSERT(src || !bytes);
+
+ if (bytes > circ->size)
+ {
+ src += bytes - circ->size;
+ bytes = circ->size;
+ }
+
+ space = circbuf_space(circ);
+ if (bytes > space)
+ {
+ overwrite = bytes - space;
+ }
+
+ off = circ->head % circ->size;
+ space = circ->size - off;
+ if (bytes < space)
+ {
+ space = bytes;
+ }
+
+ memcpy(circ->base + off, src, space);
+ memcpy(circ->base, src + space, bytes - space);
+ circ->head += bytes;
+ circ->tail += overwrite;
+
+ return overwrite;
+}