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// Ring buffer implementation. This is basically an array that wraps read/write
// pointers around the memory region. It should be more efficient than the old
// RBuffer which required memmove() calls to relocate read/write positions.
//
// The main purpose of RBuffer is simplify memory management when reading from
// uv_stream_t instances:
//
// - The event loop writes data to a RBuffer, advancing the write pointer
// - The main loop reads data, advancing the read pointer
// - If the buffer becomes full(size == capacity) the rstream is temporarily
// stopped(automatic backpressure handling)
//
// Reference: http://en.wikipedia.org/wiki/Circular_buffer
#ifndef NVIM_RBUFFER_H
#define NVIM_RBUFFER_H
#include <stddef.h>
#include <stdint.h>
// Macros that simplify working with the read/write pointers directly by hiding
// ring buffer wrap logic. Some examples:
//
// - Pass the write pointer to a function(write_data) that incrementally
// produces data, returning the number of bytes actually written to the
// ring buffer:
//
// RBUFFER_UNTIL_FULL(rbuf, ptr, cnt)
// rbuffer_produced(rbuf, write_data(state, ptr, cnt));
//
// - Pass the read pointer to a function(read_data) that incrementally
// consumes data, returning the number of bytes actually read from the
// ring buffer:
//
// RBUFFER_UNTIL_EMPTY(rbuf, ptr, cnt)
// rbuffer_consumed(rbuf, read_data(state, ptr, cnt));
//
// Note that the rbuffer_{produced,consumed} calls are necessary or these macros
// create infinite loops
#define RBUFFER_UNTIL_EMPTY(buf, rptr, rcnt) \
for (size_t rcnt = 0, _r = 1; _r; _r = 0) \
for (char *rptr = rbuffer_read_ptr(buf, &rcnt); \
buf->size; \
rptr = rbuffer_read_ptr(buf, &rcnt))
#define RBUFFER_UNTIL_FULL(buf, wptr, wcnt) \
for (size_t wcnt = 0, _r = 1; _r; _r = 0) \
for (char *wptr = rbuffer_write_ptr(buf, &wcnt); \
rbuffer_space(buf); \
wptr = rbuffer_write_ptr(buf, &wcnt))
// Iteration
#define RBUFFER_EACH(buf, c, i) \
for (size_t i = 0; i < buf->size; i = buf->size) \
for (char c = 0; \
i < buf->size ? ((int)(c = *rbuffer_get(buf, i))) || 1 : 0; \
i++)
#define RBUFFER_EACH_REVERSE(buf, c, i) \
for (size_t i = buf->size; i != SIZE_MAX; i = SIZE_MAX) \
for (char c = 0; \
i-- > 0 ? ((int)(c = *rbuffer_get(buf, i))) || 1 : 0; \
)
typedef struct rbuffer RBuffer;
/// Type of function invoked during certain events:
/// - When the RBuffer switches to the full state
/// - When the RBuffer switches to the non-full state
typedef void(*rbuffer_callback)(RBuffer *buf, void *data);
struct rbuffer {
rbuffer_callback full_cb, nonfull_cb;
void *data;
size_t size;
char *end_ptr, *read_ptr, *write_ptr;
char start_ptr[];
};
#ifdef INCLUDE_GENERATED_DECLARATIONS
# include "rbuffer.h.generated.h"
#endif
#endif // NVIM_RBUFFER_H
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