/src/rt/circular_buffer.cpp
http://github.com/jruderman/rust · C++ · 194 lines · 133 code · 30 blank · 31 comment · 17 complexity · 939d699fde671784aaf04b1a1d7ddf68 MD5 · raw file
- /*
- * A simple resizable circular buffer.
- */
- #include "circular_buffer.h"
- #include "rust_globals.h"
- #include "rust_kernel.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:
- //