stmbl/shared/ringbuf.h

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#pragma once
/**
* Ringbuffer structure
*
*/
struct ringbuf {
char *buf; ///< Pointer to buffer memory
unsigned bufsize; ///< Size of buffer memory
volatile unsigned pos; ///< Current read position
volatile unsigned len; ///< Length of data in buffer
};
/**
* Read a single byte from a buffer
*
* \param rb pointer to ringbuffer struct
* \param data pointer to data byte
* \return number of bytes read (0 if buffer was empty)
*/
static inline int rb_getc(struct ringbuf *rb, char *data)
{
if (!rb->len)
return 0;
*data = rb->buf[rb->pos++];
if (rb->pos >= rb->bufsize)
rb->pos -= rb->bufsize;
rb->len--;
return 1;
}
/**
* Write a single byte to a buffer
*
* \param rb pointer to ringbuffer struct
* \param data pointer to data byte
* \return number of bytes written (0 if buffer was full)
*/
static inline int rb_putc(struct ringbuf *rb, const char data)
{
if (rb->len >= rb->bufsize)
return 0;
unsigned i = rb->pos + rb->len;
if (i >= rb->bufsize)
i -= rb->bufsize;
rb->buf[i] = data;
rb->len++;
return 1;
}
#if 0
/**
* Read from a buffer
*
*/
int rb_read(struct ringbuf *rb, void *data, int len)
{
if (len > rb->len)
len = rb->len;
int len1 = len;
if (rb->pos + len1 >= rb->bufsize) {
int len2 = (rb->pos + len1) - rb->bufsize;
len1 -= len2;
memcpy((char*)data + len1, rb->buf, len2);
}
memcpy(data, rb->buf + rb->pos, len1);
rb->len -= len;
rb->pos += len;
if (rb->pos > rb->bufsize)
rb->pos -= rb->bufsize;
return len;
}
/**
* Write to a buffer
*
* \param rb pointer to ringbuffer struct
* \param data pointer to data byte
* \return number of bytes written (0 if buffer was full)
*
*/
int rb_write(struct ringbuf *rb, const void *data, int len)
{
if (len > rb->bufsize - rb->len)
len = rb->bufsize - rb->len;
int len1 = len;
if (rb->pos + rb->len + len1 >= rb->bufsize) {
int len2 = (rb->pos + rb->len + len1) - rb->bufsize;
len1 -= len2;
memcpy(rb->buf, (char*)data + len1, len2);
}
memcpy(rb->buf + rb->pos + rb->len, data, len1);
rb->len += len;
return len;
}
#endif