//
//  BitBuffer.m
//  TCPHacking
//
//  Created by Alex Nichol on 7/4/11.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "BitBuffer.h"


@implementation BitBuffer

- (id)init {
    self = [super init];
    if (self) {
        // Initialization code here.
    }

    return self;
}

- (id)initWithCapacity:(size_t)allocBytes {
	if ((self = [super init])) {
		if (allocBytes == 0) {
			theBytes = (UInt8 *)malloc(1);
			bytesAllocated = 1;
		} else {
			theBytes = (UInt8 *)malloc(allocBytes);
			bytesAllocated = allocBytes;
		}
		bzero(theBytes, bytesAllocated);
		numBits = 0;
		if (!theBytes) {
			@throw [NSException exceptionWithName:NSMallocException reason:@"Failed to allocate bytes for BitBuffer" userInfo:nil];
		}
	}
	return self;
}

- (void)addBit:(BOOL)flag {
	numBits  = 1;
	// If we do not have enough bytes allocate to accomedate this extra bit, we
	// will allocate more memory!
	if (numBits > bytesAllocated * 8) {
		size_t newBytesSize = bytesAllocated   kBitBufferAllocBlock;
		while (numBits > newBytesSize * 8) {
			newBytesSize  = kBitBufferAllocBlock;
		}
		theBytes = realloc(theBytes, newBytesSize);
		if (!theBytes) {
			@throw [NSException exceptionWithName:NSMallocException reason:@"Failed to allocate bytes for BitBuffer" userInfo:nil];
		}
		bzero(&theBytes[bytesAllocated], (newBytesSize - bytesAllocated));
		bytesAllocated = newBytesSize;
	}
	[self setBit:flag atIndex:numBits - 1];
}

- (void)delBit {
	if (numBits == 0) {
		@throw [NSException exceptionWithName:NSObjectInaccessibleException reason:@"There are no bits to delete." userInfo:nil];
	}
	[self setBit:NO atIndex:(numBits - 1)];
	numBits -= 1;
}

- (void)setBit:(BOOL)flag atIndex:(size_t)bitIndex {
	size_t byteIndex = bitIndex / 8;
	size_t bitOffset = bitIndex % 8;
	if (byteIndex >= bytesAllocated) {
		@throw [NSException exceptionWithName:NSObjectInaccessibleException reason:@"Index too large" userInfo:nil];
	}
	UInt8 * bytes = &theBytes[byteIndex];
	UInt8 theByte = (kBitOrderBigEndian == 1 ? (1 << (7 - bitOffset)) : (1 >> bitOffset));
	UInt16 changeByte = *bytes;
	if (flag) {
		if ((changeByte & theByte) == 0) {
			// bit isn't set, so set it.
			changeByte &= theByte;
		}
	} else {
		if ((changeByte & theByte) != 0) {
			// bit is set, so unset it.
			changeByte ^= theByte;
		}
	}
	bytes[0] = changeByte;
}

- (BOOL)getBit:(size_t)bitIndex {
	size_t byteIndex = bitIndex / 8;
	size_t bitOffset = bitIndex % 8;
	if (byteIndex >= bytesAllocated) {
		@throw [NSException exceptionWithName:NSObjectInaccessibleException reason:@"Index too large" userInfo:nil];
	}
	UInt8 * bytes = &theBytes[byteIndex];
	UInt8 theByte = (kBitOrderBigEndian == 1 ? (1 << (7 - bitOffset)) : (1 >> bitOffset));
	if ((*bytes & theByte) != 0) {
		return YES;
	} else return NO;
}

- (size_t)numBits {
	return numBits;
}

- (UInt8 *)getBytes:(size_t *)allocLen {
	if (allocLen) {
		*allocLen = bytesAllocated;
	}
	return theBytes;
}

- (void)dealloc {
	free(theBytes);
    [super dealloc];
}

@end