gp_cbuffer.h

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// SPDX-License-Identifier: LGPL-2.1-or-later
/*
 * Copyright (C) 2023 Cyril Hrubis <metan@ucw.cz>
 */
 
#ifndef UTILS_GP_CIRCULAR_BUFFER_H
#define UTILS_GP_CIRCULAR_BUFFER_H
 
#include <stddef.h>
 
typedef struct gp_cbuffer {
        size_t last;
        size_t used;
        size_t size;
} gp_cbuffer;
 
static inline void gp_cbuffer_init(gp_cbuffer *self, size_t size)
{
        self->last = 0;
        self->used = 0;
        self->size = size;
}
 
static inline size_t gp_cbuffer_append(gp_cbuffer *self)
{
        size_t old_last = self->last;
 
        if (self->used < self->size)
                self->used++;
 
        self->last = (self->last+1) % self->size;
 
        return old_last;
}
 
static inline size_t gp_cbuffer_next(gp_cbuffer *self, size_t idx)
{
        return (idx+1) % self->size;
}
 
static inline size_t gp_cbuffer_prev(gp_cbuffer *self, size_t idx)
{
        if (idx)
                return idx-1;
 
        return self->size-1;
}
 
static inline size_t gp_cbuffer_used(gp_cbuffer *self)
{
        return self->used;
}
 
static inline size_t gp_cbuffer_first(gp_cbuffer *self)
{
        size_t first;
 
        if (self->last >= self->used)
                first = self->last - self->used;
        else
                first = self->size - (self->used - self->last);
 
        return first;
}
 
static inline size_t gp_cbuffer_last(gp_cbuffer *self)
{
        return gp_cbuffer_prev(self, self->last);
}
 
typedef struct gp_cbuffer_iter {
        size_t idx;
        size_t cnt;
} gp_cbuffer_iter;
 
#define GP_CBUFFER_FOREACH(self, iter) \
        for ((iter)->idx = gp_cbuffer_first(self), (iter)->cnt = 0; \
             (iter)->cnt < (self)->used; \
             (iter)->idx = gp_cbuffer_next(self, (iter)->idx), (iter)->cnt++)
 
#define GP_CBUFFER_FORRANGE(self, iter, skip, count) \
        if ((self)->used > skip) \
                for ((iter)->idx = (gp_cbuffer_first(self) + skip) % (self)->size, (iter)->cnt = 0; \
                     (iter)->cnt < GP_MIN((self)->used - skip, count); \
                     (iter)->idx = gp_cbuffer_next(self, (iter)->idx), (iter)->cnt++)
 
#define GP_CBUFFER_FOREACH_REV(self, iter) \
        for ((iter)->idx = gp_cbuffer_last(self), (iter)->cnt = 0; \
             (iter)->cnt < (self)->used; \
             (iter)->idx = gp_cbuffer_prev(self, (iter)->idx), (iter)->cnt++)
 
#endif /* UTILS_GP_CIRCULAR_BUFFER_H */