/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Hex dump utilities.

 */

#import "QHex.h"

@implementation QHex

+ (NSString *)hexStringWithBytes:(const void *)bytes length:(NSUInteger)length {

    NSMutableString *   result;

    const uint8_t *     base;

    NSParameterAssert(bytes != NULL);

    // length can be 0

    base = bytes;

    result = [[NSMutableString alloc] initWithCapacity:length * 2];

    for (NSUInteger i = 0; i < length; i++) {

        [result appendFormat:@"%02x", base[i]];

    }

    return result;

}

+ (NSString *)hexStringWithData:(NSData *)data {

    static const uint8_t dummy = 0;

    const void * bytes;

    NSParameterAssert(data != nil);

    // *grrr*  -[NSData bytes] can return NULL if the data is empty, but 

    // +hexStringWithBytes:length: requires a non-NULL value.

    bytes = data.bytes;

    if (bytes == NULL) {

        assert(data.length == 0);

        bytes = &dummy;

    }

    return [[self class] hexStringWithBytes:bytes length:data.length];

}

+ (NSData *)dataWithValidHexString:(NSString *)hexString {

    NSData *    result;

    result = [[self class] dataWithHexString:hexString];

    NSParameterAssert(result != nil);

    return result;

}

+ (nullable NSData *)dataWithHexString:(NSString *)hexString {

    NSMutableData *     result;

    NSUInteger          cursor;

    NSUInteger          limit;

    NSParameterAssert(hexString != nil);

    cursor = 0;

    limit = hexString.length;

    if ((limit % 2) != 0) {

        result = nil;

    } else {

        result = [[NSMutableData alloc] initWithCapacity:limit / 2];

        while (cursor != limit) {

            unsigned int    thisUInt;

            uint8_t         thisByte;

            if ( sscanf([[hexString substringWithRange:NSMakeRange(cursor, 2)] UTF8String], "%x", &thisUInt) != 1 ) {

                result = nil;

                break;

            }

            thisByte = (uint8_t) thisUInt;

            [result appendBytes:&thisByte length:sizeof(thisByte)];

            cursor += 2;

        }

    }

    return result;

}

@end