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reimplement ringbuffer 

The new implementation use the mirroring method to distinguish full
buffer and the empty buffer. It also support buffers of arbitrary size.
This commit is contained in:
Grissiom 2013-05-08 15:45:31 +08:00
parent 1161e7b3f8
commit 639bd30321
2 changed files with 122 additions and 58 deletions
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58
components/drivers/include/rtdevice.h
View File

@ -28,16 +28,64 @@ struct rt_completion
rt_list_t suspended_list; rt_list_t suspended_list;
}; };
#define RT_RINGBUFFER_SIZE(rb) ((rb)->write_index - (rb)->read_index)
#define RT_RINGBUFFER_EMPTY(rb) ((rb)->buffer_size - RT_RINGBUFFER_SIZE(rb))
/* ring buffer */ /* ring buffer */
struct rt_ringbuffer struct rt_ringbuffer
{ {
rt_uint16_t read_index, write_index;
rt_uint8_t *buffer_ptr; rt_uint8_t *buffer_ptr;
rt_uint16_t buffer_size; /* use the msb of the {read,write}_index as mirror bit. You can see this as
* if the buffer adds a virtual mirror and the pointers point either to the
* normal or to the mirrored buffer. If the write_index has the same value
* with the read_index, but in differenct mirro, the buffer is full. While
* if the write_index and the read_index are the same and within the same
* mirror, the buffer is empty. The ASCII art of the ringbuffer is:
*
* mirror = 0 mirror = 1
* +---+---+---+---+---+---+---+|+~~~+~~~+~~~+~~~+~~~+~~~+~~~+
* | 0 | 1 | 2 | 3 | 4 | 5 | 6 ||| 0 | 1 | 2 | 3 | 4 | 5 | 6 | Full
* +---+---+---+---+---+---+---+|+~~~+~~~+~~~+~~~+~~~+~~~+~~~+
* read_idx-^ write_idx-^
*
* +---+---+---+---+---+---+---+|+~~~+~~~+~~~+~~~+~~~+~~~+~~~+
* | 0 | 1 | 2 | 3 | 4 | 5 | 6 ||| 0 | 1 | 2 | 3 | 4 | 5 | 6 | Empty
* +---+---+---+---+---+---+---+|+~~~+~~~+~~~+~~~+~~~+~~~+~~~+
* read_idx-^ ^-write_idx
*
* The tradeoff is we could only use 32KiB of buffer for 16 bit of index.
* But it should be enough for most of the cases.
*
* Ref: http://en.wikipedia.org/wiki/Circular_buffer#Mirroring */
rt_uint16_t read_mirror : 1;
rt_uint16_t read_index : 15;
rt_uint16_t write_mirror : 1;
rt_uint16_t write_index : 15;
/* as we use msb of index as mirror bit, the size should be signed and
* could only be positive. */
rt_int16_t buffer_size;
}; };
/** return the size of data in rb */
rt_inline rt_uint16_t RT_RINGBUFFER_SIZE(struct rt_ringbuffer *rb)
{
if (rb->read_index == rb->write_index)
{
if (rb->read_mirror == rb->write_mirror)
/* we are in the same side, the ringbuffer is empty. */
return 0;
else
return rb->buffer_size;
}
else
{
if (rb->write_index > rb->read_index)
return rb->write_index - rb->read_index;
else
return rb->buffer_size - (rb->read_index - rb->write_index);
}
}
/** return the size of empty space in rb */
#define RT_RINGBUFFER_EMPTY(rb) ((rb)->buffer_size - RT_RINGBUFFER_SIZE(rb))
/* pipe device */ /* pipe device */
#define PIPE_DEVICE(device) ((struct rt_pipe_device*)(device)) #define PIPE_DEVICE(device) ((struct rt_pipe_device*)(device))
struct rt_pipe_device struct rt_pipe_device
@ -95,7 +143,7 @@ void rt_completion_done(struct rt_completion *completion);
*/ */
void rt_ringbuffer_init(struct rt_ringbuffer *rb, void rt_ringbuffer_init(struct rt_ringbuffer *rb,
rt_uint8_t *pool, rt_uint8_t *pool,
rt_uint16_t size); rt_int16_t size);
rt_size_t rt_ringbuffer_put(struct rt_ringbuffer *rb, rt_size_t rt_ringbuffer_put(struct rt_ringbuffer *rb,
const rt_uint8_t *ptr, const rt_uint8_t *ptr,
rt_uint16_t length); rt_uint16_t length);

122
components/drivers/src/ringbuffer.c
View File

@ -18,12 +18,14 @@
void rt_ringbuffer_init(struct rt_ringbuffer *rb, void rt_ringbuffer_init(struct rt_ringbuffer *rb,
rt_uint8_t *pool, rt_uint8_t *pool,
rt_uint16_t size) rt_int16_t size)
{ {
RT_ASSERT(rb != RT_NULL); RT_ASSERT(rb != RT_NULL);
RT_ASSERT(size > 0)
/* initialize read and write index */ /* initialize read and write index */
rb->read_index = rb->write_index = 0; rb->read_mirror = rb->read_index = 0;
rb->write_mirror = rb->write_index = 0;
/* set buffer pool and size */ /* set buffer pool and size */
rb->buffer_ptr = pool; rb->buffer_ptr = pool;
@ -36,38 +38,40 @@ rt_size_t rt_ringbuffer_put(struct rt_ringbuffer *rb,
rt_uint16_t length) rt_uint16_t length)
{ {
rt_uint16_t size; rt_uint16_t size;
rt_uint16_t mask;
rt_uint16_t write_position;
RT_ASSERT(rb != RT_NULL); RT_ASSERT(rb != RT_NULL);
mask = rb->buffer_size - 1;
/* whether has enough space */ /* whether has enough space */
size = rb->buffer_size - (rb->write_index - rb->read_index); size = RT_RINGBUFFER_EMPTY(rb);
/* no space */ /* no space */
if (size == 0) if (size == 0)
return 0; return 0;
/* drop some data */ /* drop some data */
if (size < length) if (size < length)
length = size; length = size;
write_position = (rb->write_index & mask); if (rb->buffer_size - rb->write_index > length)
if (rb->buffer_size - write_position> length)
{ {
/* read_index - write_index = empty space */ /* read_index - write_index = empty space */
memcpy(&rb->buffer_ptr[write_position], ptr, length); memcpy(&rb->buffer_ptr[rb->write_index], ptr, length);
/* this should not cause overflow because there is enough space for
* length of data in current mirror */
rb->write_index += length;
return length;
} }
else
{ memcpy(&rb->buffer_ptr[rb->write_index],
memcpy(&rb->buffer_ptr[write_position], &ptr[0],
ptr, rb->buffer_size - rb->write_index);
rb->buffer_size - write_position); memcpy(&rb->buffer_ptr[0],
memcpy(&rb->buffer_ptr[0], &ptr[rb->buffer_size - rb->write_index],
&ptr[rb->buffer_size - write_position], length - (rb->buffer_size - rb->write_index));
length - (rb->buffer_size - write_position));
} /* we are going into the other side of the mirror */
rb->write_index += length; rb->write_mirror = ~rb->write_mirror;
rb->write_index = length - (rb->buffer_size - rb->write_index);
return length; return length;
} }
@ -78,20 +82,24 @@ RTM_EXPORT(rt_ringbuffer_put);
*/ */
rt_size_t rt_ringbuffer_putchar(struct rt_ringbuffer *rb, const rt_uint8_t ch) rt_size_t rt_ringbuffer_putchar(struct rt_ringbuffer *rb, const rt_uint8_t ch)
{ {
rt_uint16_t mask;
RT_ASSERT(rb != RT_NULL); RT_ASSERT(rb != RT_NULL);
/* whether has enough space */
mask = rb->buffer_size - 1;
/* whether has enough space */ /* whether has enough space */
if (rb->write_index - rb->read_index == rb->buffer_size) if (!RT_RINGBUFFER_EMPTY(rb))
return 0; return 0;
/* put character */ rb->buffer_ptr[rb->write_index] = ch;
rb->buffer_ptr[rb->write_index & mask] = ch;
rb->write_index += 1;
/* flip mirror */
if (rb->write_index == rb->buffer_size-1)
{
rb->write_mirror = ~rb->write_mirror;
rb->write_index = 0;
}
else
{
rb->write_index++;
}
return 1; return 1;
} }
RTM_EXPORT(rt_ringbuffer_putchar); RTM_EXPORT(rt_ringbuffer_putchar);
@ -104,38 +112,41 @@ rt_size_t rt_ringbuffer_get(struct rt_ringbuffer *rb,
rt_uint16_t length) rt_uint16_t length)
{ {
rt_size_t size; rt_size_t size;
rt_uint16_t mask;
rt_uint16_t read_position;
RT_ASSERT(rb != RT_NULL); RT_ASSERT(rb != RT_NULL);
/* whether has enough data */ /* whether has enough data */
mask = rb->buffer_size - 1; size = RT_RINGBUFFER_SIZE(rb);
size = rb->write_index - rb->read_index;
/* no data */ /* no data */
if (size == 0) if (size == 0)
return 0; return 0;
/* less data */ /* less data */
if (size < length) if (size < length)
length = size; length = size;
read_position = rb->read_index & mask; if (rb->buffer_size - rb->read_index > length)
if (rb->buffer_size - read_position >= length)
{ {
/* copy all of data */ /* copy all of data */
memcpy(ptr, &rb->buffer_ptr[read_position], length); memcpy(ptr, &rb->buffer_ptr[rb->read_index], length);
/* this should not cause overflow because there is enough space for
* length of data in current mirror */
rb->read_index += length;
return length;
} }
else
{ /* copy first and second */
/* copy first and second */ memcpy(&ptr[0],
memcpy(ptr, &rb->buffer_ptr[rb->read_index],
&rb->buffer_ptr[read_position], rb->buffer_size - rb->read_index);
rb->buffer_size - read_position); memcpy(&ptr[rb->buffer_size - rb->read_index],
memcpy(&ptr[rb->buffer_size - read_position], &rb->buffer_ptr[0],
&rb->buffer_ptr[0], length - (rb->buffer_size - rb->read_index));
length - rb->buffer_size + read_position);
} /* we are going into the other side of the mirror */
rb->read_index += length; rb->read_mirror = ~rb->read_mirror;
rb->read_index = length - (rb->buffer_size - rb->read_index);
return length; return length;
} }
@ -146,19 +157,24 @@ RTM_EXPORT(rt_ringbuffer_get);
*/ */
rt_size_t rt_ringbuffer_getchar(struct rt_ringbuffer *rb, rt_uint8_t *ch) rt_size_t rt_ringbuffer_getchar(struct rt_ringbuffer *rb, rt_uint8_t *ch)
{ {
rt_uint16_t mask;
RT_ASSERT(rb != RT_NULL); RT_ASSERT(rb != RT_NULL);
/* ringbuffer is empty */ /* ringbuffer is empty */
if (rb->read_index == rb->write_index) if (!RT_RINGBUFFER_SIZE(rb))
return 0; return 0;
mask = rb->buffer_size - 1;
/* put character */ /* put character */
*ch = rb->buffer_ptr[rb->read_index & mask]; *ch = rb->buffer_ptr[rb->read_index];
rb->read_index += 1;
if (rb->read_index == rb->buffer_size-1)
{
rb->read_mirror = ~rb->read_mirror;
rb->read_index = 0;
}
else
{
rb->read_index++;
}
return 1; return 1;
} }