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/*
* A simple resizable circular buffer.
*/
#include "rust_internal.h"
bool
is_power_of_two(size_t value) {
if (value > 0) {
return (value & (value - 1)) == 0;
}
return false;
}
circular_buffer::circular_buffer(rust_dom *dom, size_t unit_sz) :
dom(dom),
unit_sz(unit_sz),
_buffer_sz(INITIAL_CIRCULAR_BUFFFER_SIZE_IN_UNITS * unit_sz),
_next(0),
_unread(0),
_buffer((uint8_t *)dom->calloc(_buffer_sz)) {
A(dom, unit_sz, "Unit size must be larger than zero.");
dom->log(rust_log::MEM | rust_log::COMM,
"new circular_buffer(buffer_sz=%d, unread=%d)"
"-> circular_buffer=0x%" PRIxPTR,
_buffer_sz, _unread, this);
A(dom, _buffer, "Failed to allocate buffer.");
}
circular_buffer::~circular_buffer() {
dom->log(rust_log::MEM | rust_log::COMM,
"~circular_buffer 0x%" PRIxPTR,
this);
I(dom, _buffer);
// I(dom, _unread == 0);
dom->free(_buffer);
}
/**
* Copies the unread data from this buffer to the "dst" address.
*/
void
circular_buffer::transfer(void *dst) {
I(dom, dst);
I(dom, is_power_of_two(_buffer_sz));
uint8_t *ptr = (uint8_t *) dst;
for (size_t i = 0; i < _unread; i += unit_sz) {
memcpy(&ptr[i], &_buffer[(_next + i) & (_buffer_sz - 1)], unit_sz);
}
}
/**
* Copies the data at the "src" address into this buffer. The buffer is
* grown if it isn't large enough.
*/
void
circular_buffer::enqueue(void *src) {
I(dom, src);
I(dom, _unread <= _buffer_sz);
// Grow if necessary.
if (_unread == _buffer_sz) {
I(dom, _buffer_sz <= MAX_CIRCULAR_BUFFFER_SIZE);
void *tmp = dom->malloc(_buffer_sz << 1);
transfer(tmp);
_buffer_sz <<= 1;
dom->free(_buffer);
_buffer = (uint8_t *)tmp;
}
dom->log(rust_log::MEM | rust_log::COMM,
"circular_buffer enqueue "
"unread: %d, buffer_sz: %d, unit_sz: %d",
_unread, _buffer_sz, unit_sz);
I(dom, is_power_of_two(_buffer_sz));
I(dom, _unread < _buffer_sz);
I(dom, _unread + unit_sz <= _buffer_sz);
// Copy data
size_t i = (_next + _unread) & (_buffer_sz - 1);
memcpy(&_buffer[i], src, unit_sz);
_unread += unit_sz;
dom->log(rust_log::MEM | rust_log::COMM,
"circular_buffer pushed data at index: %d", i);
}
/**
* Copies data from this buffer to the "dst" address. The buffer is
* shrunk if possible.
*/
void
circular_buffer::dequeue(void *dst) {
I(dom, unit_sz > 0);
I(dom, _unread >= unit_sz);
I(dom, _unread <= _buffer_sz);
I(dom, _buffer);
if (dst != NULL) {
memcpy(dst, &_buffer[_next], unit_sz);
}
dom->log(rust_log::MEM | rust_log::COMM,
"shifted data from index %d", _next);
_unread -= unit_sz;
_next += unit_sz;
I(dom, _next <= _buffer_sz);
if (_next == _buffer_sz) {
_next = 0;
}
// Shrink if possible.
if (_buffer_sz >= INITIAL_CIRCULAR_BUFFFER_SIZE_IN_UNITS * unit_sz &&
_unread <= _buffer_sz / 4) {
dom->log(rust_log::MEM | rust_log::COMM,
"circular_buffer is shrinking to %d bytes", _buffer_sz / 2);
void *tmp = dom->malloc(_buffer_sz / 2);
transfer(tmp);
_buffer_sz >>= 1;
dom->free(_buffer);
_buffer = (uint8_t *)tmp;
_next = 0;
}
}
uint8_t *
circular_buffer::peek() {
return &_buffer[_next];
}
bool
circular_buffer::is_empty() {
return _unread == 0;
}
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