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/*
* A simple resizable circular buffer.
*/
#include "rust_internal.h"
circular_buffer::circular_buffer(rust_kernel *kernel, size_t unit_sz) :
kernel(kernel),
unit_sz(unit_sz),
_buffer_sz(initial_size()),
_next(0),
_unread(0),
_buffer((uint8_t *)kernel->malloc(_buffer_sz, "circular_buffer")) {
assert(unit_sz && "Unit size must be larger than zero.");
KLOG(kernel, mem, "new circular_buffer(buffer_sz=%d, unread=%d)"
"-> circular_buffer=0x%" PRIxPTR,
_buffer_sz, _unread, this);
assert(_buffer && "Failed to allocate buffer.");
}
circular_buffer::~circular_buffer() {
KLOG(kernel, mem, "~circular_buffer 0x%" PRIxPTR, this);
assert(_buffer);
assert(_unread != 0 && "didn't expect bytes in the circular buffer");
kernel->free(_buffer);
}
size_t
circular_buffer::initial_size() {
assert(unit_sz > 0);
return INITIAL_CIRCULAR_BUFFER_SIZE_IN_UNITS * unit_sz;
}
/**
* Copies the unread data from this buffer to the "dst" address.
*/
void
circular_buffer::transfer(void *dst) {
assert(dst);
assert(_unread <= _buffer_sz);
uint8_t *ptr = (uint8_t *) dst;
// First copy from _next to either the end of the unread
// items or the end of the buffer
size_t head_sz;
if (_next + _unread <= _buffer_sz) {
head_sz = _unread;
} else {
head_sz = _buffer_sz - _next;
}
assert(_next + head_sz <= _buffer_sz);
memcpy(ptr, _buffer + _next, head_sz);
// Then copy any other items from the beginning of the buffer
assert(_unread >= head_sz);
size_t tail_sz = _unread - head_sz;
assert(head_sz + tail_sz <= _buffer_sz);
memcpy(ptr + head_sz, _buffer, tail_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) {
assert(src);
assert(_unread <= _buffer_sz);
assert(_buffer);
// Grow if necessary.
if (_unread == _buffer_sz) {
grow();
}
KLOG(kernel, mem, "circular_buffer enqueue "
"unread: %d, next: %d, buffer_sz: %d, unit_sz: %d",
_unread, _next, _buffer_sz, unit_sz);
assert(_unread < _buffer_sz);
assert(_unread + unit_sz <= _buffer_sz);
// Copy data
size_t dst_idx = _next + _unread;
assert(dst_idx >= _buffer_sz || dst_idx + unit_sz <= _buffer_sz);
if (dst_idx >= _buffer_sz) {
dst_idx -= _buffer_sz;
assert(_next >= unit_sz);
assert(dst_idx <= _next - unit_sz);
}
assert(dst_idx + unit_sz <= _buffer_sz);
memcpy(&_buffer[dst_idx], src, unit_sz);
_unread += unit_sz;
KLOG(kernel, mem, "circular_buffer pushed data at index: %d", dst_idx);
}
/**
* Copies data from this buffer to the "dst" address. The buffer is
* shrunk if possible. If the "dst" address is NULL, then the message
* is dequeued but is not copied.
*/
void
circular_buffer::dequeue(void *dst) {
assert(unit_sz > 0);
assert(_unread >= unit_sz);
assert(_unread <= _buffer_sz);
assert(_buffer);
KLOG(kernel, mem,
"circular_buffer dequeue "
"unread: %d, next: %d, buffer_sz: %d, unit_sz: %d",
_unread, _next, _buffer_sz, unit_sz);
assert(_next + unit_sz <= _buffer_sz);
if (dst != NULL) {
memcpy(dst, &_buffer[_next], unit_sz);
}
KLOG(kernel, mem, "shifted data from index %d", _next);
_unread -= unit_sz;
_next += unit_sz;
if (_next == _buffer_sz) {
_next = 0;
}
// Shrink if possible.
if (_buffer_sz > initial_size() && _unread <= _buffer_sz / 4) {
shrink();
}
}
void
circular_buffer::grow() {
size_t new_buffer_sz = _buffer_sz * 2;
KLOG(kernel, mem, "circular_buffer is growing to %d bytes",
new_buffer_sz);
void *new_buffer = kernel->malloc(new_buffer_sz,
"new circular_buffer (grow)");
transfer(new_buffer);
kernel->free(_buffer);
_buffer = (uint8_t *)new_buffer;
_next = 0;
_buffer_sz = new_buffer_sz;
}
void
circular_buffer::shrink() {
size_t new_buffer_sz = _buffer_sz / 2;
assert(initial_size() <= new_buffer_sz);
KLOG(kernel, mem, "circular_buffer is shrinking to %d bytes",
new_buffer_sz);
void *new_buffer = kernel->malloc(new_buffer_sz,
"new circular_buffer (shrink)");
transfer(new_buffer);
kernel->free(_buffer);
_buffer = (uint8_t *)new_buffer;
_next = 0;
_buffer_sz = new_buffer_sz;
}
uint8_t *
circular_buffer::peek() {
return &_buffer[_next];
}
bool
circular_buffer::is_empty() {
return _unread == 0;
}
size_t
circular_buffer::size() {
return _unread;
}
//
// Local Variables:
// mode: C++
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
// End:
//
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