137 lines
5.4 KiB
C
137 lines
5.4 KiB
C
//
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// TPCircularBuffer.c
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// Circular/Ring buffer implementation
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//
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// https://github.com/michaeltyson/TPCircularBuffer
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//
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// Created by Michael Tyson on 10/12/2011.
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//
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// Copyright (C) 2012-2013 A Tasty Pixel
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//
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// This software is provided 'as-is', without any express or implied
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// warranty. In no event will the authors be held liable for any damages
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// arising from the use of this software.
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//
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// Permission is granted to anyone to use this software for any purpose,
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// including commercial applications, and to alter it and redistribute it
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// freely, subject to the following restrictions:
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//
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// 1. The origin of this software must not be misrepresented; you must not
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// claim that you wrote the original software. If you use this software
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// in a product, an acknowledgment in the product documentation would be
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// appreciated but is not required.
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//
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// 2. Altered source versions must be plainly marked as such, and must not be
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// misrepresented as being the original software.
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//
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// 3. This notice may not be removed or altered from any source distribution.
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//
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#include "TPCircularBuffer.h"
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#include <mach/mach.h>
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#include <stdio.h>
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#define reportResult(result,operation) (_reportResult((result),(operation),strrchr(__FILE__, '/')+1,__LINE__))
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static inline bool _reportResult(kern_return_t result, const char *operation, const char* file, int line) {
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if ( result != ERR_SUCCESS ) {
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printf("%s:%d: %s: %s\n", file, line, operation, mach_error_string(result));
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return false;
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}
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return true;
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}
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bool TPCircularBufferInit(TPCircularBuffer *buffer, int length) {
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// Keep trying until we get our buffer, needed to handle race conditions
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int retries = 3;
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while ( true ) {
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buffer->length = round_page(length); // We need whole page sizes
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// Temporarily allocate twice the length, so we have the contiguous address space to
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// support a second instance of the buffer directly after
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vm_address_t bufferAddress;
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kern_return_t result = vm_allocate(mach_task_self(),
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&bufferAddress,
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buffer->length * 2,
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VM_FLAGS_ANYWHERE); // allocate anywhere it'll fit
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if ( result != ERR_SUCCESS ) {
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if ( retries-- == 0 ) {
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reportResult(result, "Buffer allocation");
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return false;
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}
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// Try again if we fail
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continue;
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}
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// Now replace the second half of the allocation with a virtual copy of the first half. Deallocate the second half...
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result = vm_deallocate(mach_task_self(),
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bufferAddress + buffer->length,
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buffer->length);
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if ( result != ERR_SUCCESS ) {
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if ( retries-- == 0 ) {
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reportResult(result, "Buffer deallocation");
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return false;
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}
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// If this fails somehow, deallocate the whole region and try again
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vm_deallocate(mach_task_self(), bufferAddress, buffer->length);
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continue;
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}
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// Re-map the buffer to the address space immediately after the buffer
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vm_address_t virtualAddress = bufferAddress + buffer->length;
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vm_prot_t cur_prot, max_prot;
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result = vm_remap(mach_task_self(),
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&virtualAddress, // mirror target
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buffer->length, // size of mirror
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0, // auto alignment
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0, // force remapping to virtualAddress
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mach_task_self(), // same task
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bufferAddress, // mirror source
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0, // MAP READ-WRITE, NOT COPY
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&cur_prot, // unused protection struct
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&max_prot, // unused protection struct
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VM_INHERIT_DEFAULT);
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if ( result != ERR_SUCCESS ) {
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if ( retries-- == 0 ) {
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reportResult(result, "Remap buffer memory");
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return false;
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}
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// If this remap failed, we hit a race condition, so deallocate and try again
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vm_deallocate(mach_task_self(), bufferAddress, buffer->length);
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continue;
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}
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if ( virtualAddress != bufferAddress+buffer->length ) {
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// If the memory is not contiguous, clean up both allocated buffers and try again
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if ( retries-- == 0 ) {
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printf("Couldn't map buffer memory to end of buffer\n");
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return false;
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}
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vm_deallocate(mach_task_self(), virtualAddress, buffer->length);
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vm_deallocate(mach_task_self(), bufferAddress, buffer->length);
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continue;
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}
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buffer->buffer = (void*)bufferAddress;
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buffer->fillCount = 0;
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buffer->head = buffer->tail = 0;
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return true;
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}
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return false;
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}
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void TPCircularBufferCleanup(TPCircularBuffer *buffer) {
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vm_deallocate(mach_task_self(), (vm_address_t)buffer->buffer, buffer->length * 2);
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memset(buffer, 0, sizeof(TPCircularBuffer));
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}
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void TPCircularBufferClear(TPCircularBuffer *buffer) {
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int32_t fillCount;
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if ( TPCircularBufferTail(buffer, &fillCount) ) {
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TPCircularBufferConsume(buffer, fillCount);
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}
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}
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