100 lines
3.3 KiB
Objective-C
100 lines
3.3 KiB
Objective-C
#import "CyclicalBuffer.h"
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#import "Constraints.h"
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#import "Util.h"
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#define INITIAL_CAPACITY 100 // The buffer size can not be longer than an unsigned int.
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@implementation CyclicalBuffer
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-(id) init {
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if (self = [super init]) {
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buffer = [NSMutableData dataWithLength:INITIAL_CAPACITY];
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}
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return self;
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}
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-(void) enqueueData:(NSData*)data {
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require(data != nil);
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if(data.length == 0) return;
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NSUInteger incomingDataLength = data.length;
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NSUInteger bufferCapacity = buffer.length;
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NSUInteger writeOffset = (readOffset + count) % bufferCapacity;
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NSUInteger bufferSpaceAvailable = bufferCapacity - count;
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NSUInteger writeSlack = bufferCapacity - writeOffset;
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if (bufferSpaceAvailable < incomingDataLength) {
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NSUInteger readSlack = bufferCapacity - readOffset;
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NSUInteger newCapacity = bufferCapacity * 2 + incomingDataLength;
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NSMutableData* newBuffer = [NSMutableData dataWithLength:newCapacity];
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[newBuffer replaceBytesInRange:NSMakeRange(0, MIN(readSlack, count)) withBytes:(uint8_t*)[buffer bytes] + readOffset];
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if (readSlack < count) {
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[newBuffer replaceBytesInRange:NSMakeRange(readSlack, count - readSlack) withBytes:(uint8_t*)[buffer bytes]];
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}
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buffer = newBuffer;
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bufferCapacity = newCapacity;
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readOffset = 0;
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writeOffset = count;
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bufferSpaceAvailable = bufferCapacity - count;
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writeSlack = bufferCapacity - writeOffset;
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}
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assert(bufferSpaceAvailable >= incomingDataLength);
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[buffer replaceBytesInRange:NSMakeRange(writeOffset, MIN(writeSlack, incomingDataLength)) withBytes:[data bytes]];
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if (incomingDataLength > writeSlack) {
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[buffer replaceBytesInRange:NSMakeRange(0, incomingDataLength - writeSlack) withBytes:(uint8_t*)[data bytes] + writeSlack];
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}
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count += data.length;
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}
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-(NSUInteger) enqueuedLength {
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return count;
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}
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-(void) discard:(NSUInteger)length {
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require(length <= count);
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count -= length;
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readOffset = (readOffset + length)%(unsigned int)buffer.length;
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}
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-(NSData*) peekDataWithLength:(NSUInteger)length{
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require(length <= count);
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if (length == 0) return [NSData data];
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NSUInteger readSlack = buffer.length - readOffset;
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NSMutableData* result = [NSMutableData dataWithLength:length];
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[result replaceBytesInRange:NSMakeRange(0, MIN(readSlack, length)) withBytes:(uint8_t*)[buffer bytes] + readOffset];
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if (readSlack < length) {
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[result replaceBytesInRange:NSMakeRange(readSlack, length - readSlack) withBytes:[buffer bytes]];
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}
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return result;
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}
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-(NSData*) dequeueDataWithLength:(NSUInteger)length {
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NSData* result = [self peekDataWithLength:length];
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[self discard:length];
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return result;
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}
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-(NSData*) dequeuePotentialyVolatileDataWithLength:(NSUInteger)length {
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NSUInteger readSlack = buffer.length - readOffset;
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if (readSlack < length) return [self dequeueDataWithLength:length];
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NSData* result = [buffer subdataVolatileWithRange:NSMakeRange(readOffset, length)];
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[self discard:length];
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return result;
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}
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-(NSData*) peekVolatileHeadOfData {
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NSUInteger capacity = buffer.length;
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NSUInteger slack = capacity - readOffset;
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return [buffer subdataVolatileWithRange:NSMakeRange(readOffset, MIN(count, slack))];
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}
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@end
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