/*

     File: ASCIIString.m

 Abstract: An NSData-backed string that treats each byte as an ASCII character (more precisely, an ISO-8859-1 character). If the character is a control character other than tab or newline, it is displayed as a period.

  Version: 1.2

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 */

#import "ASCIIString.h"

/* Returns the character used to display the given byte in the resulting string.

 */

static inline unichar displayCharacterForByte(unsigned char dataByte) {

    if ((dataByte >= 32 && dataByte < 127) ||

            (dataByte >= (128 + 32) && dataByte < 255) ||

            dataByte == '\n' ||

            dataByte == '\t') {

        return dataByte;

    } else {

        return '.';

    }

}

@implementation ASCIIString

- (id)initWithData:(NSData *)obj {

    if (self = [super init]) {

        data = [obj copy];

    }

    return self;

}

- (id)init {

    return [self initWithData:[NSData data]];

}

- (void)dealloc {

    [data release];

    [super dealloc];

}

- (NSData *)data {

    return data;

}

#pragma mark -

/* Returns the length of the string, which is one Unicode character per byte.

 */

- (NSUInteger)length {

    return [data length];

}

/* Converts the byte at the given index to a displayable unichar using displayCharacterForByte().

 */

- (unichar)characterAtIndex:(NSUInteger)index {

    const unsigned char *bytes = [data bytes];

    return displayCharacterForByte(bytes[index]);

}

/* Converts a range of bytes to displayable characters and puts them in the supplied buffer, using displayCharacterForByte(). If the range is beyond the bounds of the data, an exception is thrown.

 */

- (void)getCharacters:(unichar *)buffer range:(NSRange)range {

    const unsigned char *bytes = [data bytes];

    if (NSMaxRange(range) > [data length]) {

        @throw [NSException exceptionWithName:NSRangeException reason:[NSString stringWithFormat:@"*** -[%@ %@]: Range %@ is out of bounds", NSStringFromClass([self class]), NSStringFromSelector(_cmd), NSStringFromRange(range)] userInfo:nil];

    }

    NSUInteger i;

    for (i = 0; i < range.length; i++) {

        buffer[i] = displayCharacterForByte(bytes[range.location + i]);

    }

}

@end