I have an Uint8List data list, for example:
Uint8List uintList = Uint8List.fromList([10, 1]);
How can I convert these numbers to a decimal number?
int decimalValue = ??? // in this case 265
Mees' answer is the correct general method, and it's good to understand how to do bitwise operations manually.
However, Dart does have a ByteData class that has various functions to help parse byte data for you (e.g. getInt16, getUint16). In your case, you can do:
Uint8List uintList = Uint8List.fromList([10, 1]);
int decimalValue = ByteData.view(uintList.buffer).getInt16(0, Endian.little);
print(decimalValue); // Prints: 266.
From what I understand of your question, you want decimalValue to be an integer where the least significant byte is (decimal)10, and the byte after that to be 1. This would result in the value 1 * 256 + 10 = 266. If you meant the bytes the other way around, it would be 10 * 256 + 1 = 2560 + 1 = 2561.
I don't actually have any experience with dart, but I assume code similar to this would work:
int decimalValue = 0;
for (int i = 0; i < uintList.length; i++) {
decimalValue = decimalValue << 8; // shift everything one byte to the left
decimalValue = decimalValue | uintList[i]; // bitwise or operation
}
If it doesn't produce the number you want it to, you might have to iterate through the loop backwards instead, which requires changing one line of code:
for (int i = uintList.length-1; i >= 0; i--) {
I am facing problem with the objective c code to convert decimal to binary. When I enter small values it shows me the output.
For e.g. 12 -> 1010
But when I enters large numbers, it shows me the output as "10..." (includes dots in the output)
Please help me.
My program is as follows:
NSUInteger x = [newDec integerValue];
//int y[30];
int i=0;
int m =1;
while (x != 0) {
int mod = x % 2;
x /= 2;
i = i + mod * m;
m = m * 10;
string = [NSString stringWithFormat:#"%d", i];
}
There are two problems with your code.
1) Your label size is perhaps not able to accommodate your string. So check the length of it.
2) Your code will not support the conversion if value of x is large. The reason is that int has limited capacity. Check this question regarding memory size of in-built variable. So, consider making your string mutable and add 0s or 1s in it. I am attaching my snippet of code.
NSMutableString *string = [[NSMutableString alloc] init];
while (x != 0) {
int mod = x % 2;
x /= 2;
[string insertString:[NSString stringWithFormat:#"%d", mod] atIndex:0];
}
NSLog(#"String = %#", string);
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I am working on a app which sends data to server with user location info. Server accept this data based on checksum calculation, which is written in java.
Here is the code written in Java:
private static final String CHECKSUM_CONS = "1217278743473774374";
private static String createChecksum(double lat, double lon) {
int latLon = (int) ((lat + lon) * 1E6);
String checkSumStr = CHECKSUM_CONS + latLon;
byte buffer[] = checkSumStr.getBytes();
ByteArrayInputStream bais = new ByteArrayInputStream(buffer);
CheckedInputStream cis = new CheckedInputStream(bais, new Adler32());
byte readBuffer[] = new byte[50];
long value = 0;
try {
while (cis.read(readBuffer) >= 0) {
value = cis.getChecksum().getValue();
}
} catch (Exception e) {
LOGGER.log(Level.SEVERE, e.getMessage(), e);
}
return String.valueOf(value);
}
I tried looking for help to find out how to write objective c equivalent of this. Above function uses adler32 and I don't have any clue about that. Please help.
Thanks for your time.
The answers shown here by #achievelimitless and #user3275097 are incorrect.
First off, signed integers should not be used. The modulo operator on negative numbers is defined differently in different languages, and should be avoided when possible. Simply use unsigned integers instead.
Second, the loops will quickly overflow the 16-bit accumulators, which will give the wrong answer. The modulo operations can be deferred, but they must be done before overflow. You can calculate how many loops you can do safely by assuming that all of the input bytes are 255.
Third, because of the second point, you should not use 16-bit types. You should use at least 32-bit types to avoid having to do the modulo operation very often. You still need to limit the number of loops, but the number gets much bigger. For 32-bit unsigned types, the maximum number of loops is 5552. So the basic code looks like:
#define MOD 65521
#define MAX 5552
unsigned long adler32(unsigned char *buf, size_t len)
{
unsigned long a = 1, b = 0;
size_t n;
while (len) {
n = len > MAX ? MAX : len;
len -= n;
do {
a += *buf++;
b += a;
} while (--n);
a %= MOD;
b %= MOD;
}
return a | (b << 16);
}
As noted by #Sulthan, you should simply use the adler32() function provided in zlib, which is already there on Mac OS X and iOS.
On basis of definition of adler32 checksum as mentioned in wikipedia,
Objective C implementation would be like this:
static NSNumber * adlerChecksumof(NSString *str)
{
NSMutableData *data= [[NSMutableData alloc]init];
unsigned char whole_byte;
char byte_chars[3] = {'\0','\0','\0'};
for (int i = 0; i < ([str length] / 2); i++)
{
byte_chars[0] = [str characterAtIndex:i*2];
byte_chars[1] = [str characterAtIndex:i*2+1];
whole_byte = strtol(byte_chars, NULL, 16);
[data appendBytes:&whole_byte length:1];
}
int16_t a=1;
int16_t b=0;
Byte * dataBytes= (Byte *)[data bytes];
for (int i=0; i<[data length]; i++)
{
a+= dataBytes[i];
b+=a;
}
a%= 65521;
b%= 65521;
int32_t adlerChecksum= b*65536+a;
return #(adlerChecksum);
}
Here str would be your string as mentioned in your question..
So when you want to calculate checksum of some string just do this:
NSNumber * calculatedChkSm= adlerChecksumof(#"1217278743473774374");
Please Let me know if more info needed
Is there a simple way to do something like..
[NSMagicDataConverter humanStringWithBytes:20000000]
..which would return "19.1MB"?
Starting in OS X 10.8 and iOS 6, you can use NSByteCountFormatter.
Your example would look like this:
[NSByteCountFormatter stringFromByteCount:20000000 countStyle:NSByteCountFormatterCountStyleFile];
I would mush this into an NSFormatter subclass.
#import <Foundation/Foundation.h>
#interface SOFileSizeFormatter : NSNumberFormatter
{
#private
BOOL useBaseTenUnits;
}
/** Flag signaling whether to calculate file size in binary units (1024) or base ten units (1000). Default is binary units. */
#property (nonatomic, readwrite, assign, getter=isUsingBaseTenUnits) BOOL useBaseTenUnits;
#end
static const char sUnits[] = { '\0', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y' };
static int sMaxUnits = sizeof sUnits - 1;
#implementation SOFileSizeFormatter
#synthesize useBaseTenUnits;
- (NSString *) stringFromNumber:(NSNumber *)number
{
int multiplier = useBaseTenUnits ? 1000 : 1024;
int exponent = 0;
double bytes = [number doubleValue];
while ((bytes >= multiplier) && (exponent < sMaxUnits)) {
bytes /= multiplier;
exponent++;
}
return [NSString stringWithFormat:#"%# %cB", [super stringFromNumber: [NSNumber numberWithDouble: bytes]], sUnits[exponent]];
}
#end
Usage:
NSString *path = ...; // path to a file of 1,500,000 bytes
NSString *sizeString = nil;
NSNumber *sizeAttrib = [[[NSFileManager defaultManager] attributesOfItemAtPath:path error:NULL]objectForKey:NSFileSize];
SOFileSizeFormatter *sizeFormatter = [[[SOFileSizeFormatter alloc] init] autorelease];
[sizeFormatter setMaximumFractionDigits:2];
sizeString = [sizeFormatter stringFromNumber:sizeAttrib];
// sizeString ==> #"1.43 MB"
[sizeFormatter setUseBaseTenUnits:YES];
sizeString = [sizeFormatter stringFromNumber:sizeAttrib];
// sizeString ==> #"1.5 MB"
Here's my own take on the problem:
enum {
kUnitStringBinaryUnits = 1 << 0,
kUnitStringOSNativeUnits = 1 << 1,
kUnitStringLocalizedFormat = 1 << 2
};
NSString* unitStringFromBytes(double bytes, uint8_t flags){
static const char units[] = { '\0', 'k', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y' };
static int maxUnits = sizeof units - 1;
int multiplier = (flags & kUnitStringOSNativeUnits && !leopardOrGreater() || flags & kUnitStringBinaryUnits) ? 1024 : 1000;
int exponent = 0;
while (bytes >= multiplier && exponent < maxUnits) {
bytes /= multiplier;
exponent++;
}
NSNumberFormatter* formatter = [[[NSNumberFormatter alloc] init] autorelease];
[formatter setMaximumFractionDigits:2];
if (flags & kUnitStringLocalizedFormat) {
[formatter setNumberStyle: NSNumberFormatterDecimalStyle];
}
// Beware of reusing this format string. -[NSString stringWithFormat] ignores \0, *printf does not.
return [NSString stringWithFormat:#"%# %cB", [formatter stringFromNumber: [NSNumber numberWithDouble: bytes]], units[exponent]];
}
By default (if 0 is passed for flags), it will output SI units (base ten). You can set kUnitStringBinaryUnits to select binary (base two) units suitable for memory, or kUnitStringOSNativeUnits to have the unit type selected automatically based on OS version (pre-Leopard gets base two, post-Leopard gets base ten). Setting kUnitStringLocalizedFormat formats the string based on the user's current locale. For example:
unitStringFromBytes(1073741824, 0); // → "1.07 GB"
unitStringFromBytes(1073741824, kUnitStringBinaryUnits); // → "1 GB"
unitStringFromBytes(1073741824, kUnitStringOSNativeUnits | kUnitStringLocalizedFormat); // → "1.07 GB" (In Mac OS 10.6)
unitStringFromBytes(12345678901234567890123456789, kUnitStringOSNativeUnits | kUnitStringLocalizedFormat); // → "12,345.68 YB" (In Mac OS 10.6, in the US)
unitStringFromBytes(12345678901234567890123456789, kUnitStringOSNativeUnits | kUnitStringLocalizedFormat); // → "12.345,68 YB" (In Mac OS 10.6, in Spain)
Here's the helper function required for OS-native units:
BOOL leopardOrGreater(){
static BOOL alreadyComputedOS = NO;
static BOOL leopardOrGreater = NO;
if (!alreadyComputedOS) {
SInt32 majorVersion, minorVersion;
Gestalt(gestaltSystemVersionMajor, &majorVersion);
Gestalt(gestaltSystemVersionMinor, &minorVersion);
leopardOrGreater = ((majorVersion == 10 && minorVersion >= 5) || majorVersion > 10);
alreadyComputedOS = YES;
}
return leopardOrGreater;
}
NSString *stringFromFileSize(NSInteger theSize)
{
/*
From http://snippets.dzone.com/posts/show/3038 with slight modification
*/
float floatSize = theSize;
if (theSize<1023)
return([NSString stringWithFormat:#"%i bytes",theSize]);
floatSize = floatSize / 1024;
if (floatSize<1023)
return([NSString stringWithFormat:#"%1.1f KB",floatSize]);
floatSize = floatSize / 1024;
if (floatSize<1023)
return([NSString stringWithFormat:#"%1.1f MB",floatSize]);
floatSize = floatSize / 1024;
return([NSString stringWithFormat:#"%1.1f GB",floatSize]);
}
Here is a more Objective C-like function (uses NSNumber, NSArray, NSStirng, etc...) for doing this conversion.
This is based on Sidnicious's answer, so a big thanks for the initial work done there. Also based on Wikipedia articles.
Use it generally like this: [HumanReadableDataSizeHelper humanReadableSizeFromBytes:[NSNumber numberWithDouble:doubleValue]].
But, it looks like you want SI units with a 1024 multiplier so you would use it like this: [HumanReadableDataSizeHelper humanReadableSizeFromBytes:[NSNumber numberWithDouble:doubleValue] useSiPrefixes:YES useSiMultiplier:NO]
The reason I default to binary prefixes (ki, Mi) is because those seem to be the most appropriate unit prefix set to use for sizes of data on a computer. What you requested was the SI unit prefixes but using a multiplier of 1024, technically incorrect. Though I will note that SI prefixes for multiples of 1024 is fairly common and binary prefixes are not well accepted (according to Wikipedia).
HumanReadableDataSizeHelper.h
#interface HumanReadableDataSizeHelper : NSObject
/**
#brief Produces a string containing the largest appropriate units and the new fractional value.
#param sizeInBytes The value to convert in bytes.
This function converts the bytes value to a value in the greatest units that produces a value >= 1 and returns the new value and units as a string.
The magnitude multiplier used is 1024 and the prefixes used are the binary prefixes (ki, Mi, ...).
*/
+ (NSString *)humanReadableSizeFromBytes:(NSNumber *)sizeInBytes;
/**
#brief Produces a string containing the largest appropriate units and the new fractional value.
#param sizeInBytes The value to convert in bytes.
#param useSiPrefixes Controls what prefix-set is used.
#param useSiMultiplier Controls what magnitude multiplier is used.
This function converts the bytes value to a value in the greatest units that produces a value >= 1 and returns the new value and units as a string.
When useSiPrefixes is true, the prefixes used are the SI unit prefixes (k, M, ...).
When useSiPrefixes is false, the prefixes used are the binary prefixes (ki, Mi, ...).
When useSiMultiplier is true, the magnitude multiplier used is 1000
When useSiMultiplier is false, the magnitude multiplier used is 1024.
*/
+ (NSString *)humanReadableSizeFromBytes:(NSNumber *)sizeInBytes useSiPrefixes:(BOOL)useSiPrefixes useSiMultiplier:(BOOL)useSiMultiplier;
#end
HumanReadableDataSizeHelper.m
#implementation HumanReadableDataSizeHelper
+ (NSString *)humanReadableSizeFromBytes:(NSNumber *)sizeInBytes
{
return [self humanReadableSizeFromBytes:sizeInBytes useSiPrefixes:NO useSiMultiplier:NO];
}
+ (NSString *)humanReadableSizeFromBytes:(NSNumber *)sizeInBytes useSiPrefixes:(BOOL)useSiPrefixes useSiMultiplier:(BOOL)useSiMultiplier
{
NSString *unitSymbol = #"B";
NSInteger multiplier;
NSArray *prefixes;
if (useSiPrefixes)
{
/* SI prefixes
http://en.wikipedia.org/wiki/Kilo-
kilobyte (kB) 10^3
megabyte (MB) 10^6
gigabyte (GB) 10^9
terabyte (TB) 10^12
petabyte (PB) 10^15
exabyte (EB) 10^18
zettabyte (ZB) 10^21
yottabyte (YB) 10^24
*/
prefixes = [NSArray arrayWithObjects: #"", #"k", #"M", #"G", #"T", #"P", #"E", #"Z", #"Y", nil];
}
else
{
/* Binary prefixes
http://en.wikipedia.org/wiki/Binary_prefix
kibibyte (KiB) 2^10 = 1.024 * 10^3
mebibyte (MiB) 2^20 ≈ 1.049 * 10^6
gibibyte (GiB) 2^30 ≈ 1.074 * 10^9
tebibyte (TiB) 2^40 ≈ 1.100 * 10^12
pebibyte (PiB) 2^50 ≈ 1.126 * 10^15
exbibyte (EiB) 2^60 ≈ 1.153 * 10^18
zebibyte (ZiB) 2^70 ≈ 1.181 * 10^21
yobibyte (YiB) 2^80 ≈ 1.209 * 10^24
*/
prefixes = [NSArray arrayWithObjects: #"", #"ki", #"Mi", #"Gi", #"Ti", #"Pi", #"Ei", #"Zi", #"Yi", nil];
}
if (useSiMultiplier)
{
multiplier = 1000;
}
else
{
multiplier = 1024;
}
NSInteger exponent = 0;
double size = [sizeInBytes doubleValue];
while ( (size >= multiplier) && (exponent < [prefixes count]) )
{
size /= multiplier;
exponent++;
}
NSNumberFormatter* formatter = [[[NSNumberFormatter alloc] init] autorelease];
[formatter setMaximumFractionDigits:2];
[formatter setNumberStyle:NSNumberFormatterDecimalStyle]; // Uses localized number formats.
NSString *sizeInUnits = [formatter stringFromNumber:[NSNumber numberWithDouble:size]];
return [NSString stringWithFormat:#"%# %#%#", sizeInUnits, [prefixes objectAtIndex:exponent], unitSymbol];
}
#end
You can use FormatterKit and its TTTUnitOfInformationFormatter class:
https://github.com/mattt/FormatterKit
It is also available through CocoaPods with:
pod 'FormatterKit', '~> 1.1.1'
- (id)transformedValue:(id)value
{
double convertedValue = [value doubleValue];
int multiplyFactor = 0;
NSArray *tokens = #[#"bytes",#"KB",#"MB",#"GB",#"TB"];
while (convertedValue > 1024) {
convertedValue /= 1024;
multiplyFactor++;
}
return [NSString stringWithFormat:#"%4.2f %#",convertedValue, tokens[multiplyFactor]];
}
I know the questions is for Obj C but if anyone looking for a swift version:
public static func fileSizeDisplay(fromBytes:Int) -> String {
let display = ["bytes","KB","MB","GB","TB","PB"]
var value:Double = Double(fromBytes)
var type = 0
while (value > 1024){
value /= 1024
type = type + 1
}
return "\(String(format:"%g", value)) \(display[type])"
}
the maximum value for an 32-Bit integer is: 2^31-1 = 2147483647.
but just with negative and positive number. because the half of the number is negative.
so the real maximum value is 2^32-1 = 4294967295. but in this case we just use positive numbers.
ok, a normal int is both negative and positive number.
i want to use just positive number because i want the maximum value to be: 4294967295.
i'm going to use
"unsigned int"
instead of
"int"
but this will not work!
the maximum value is still 2147483647.
here is the code for a simple random number generator:
-(Action for my button) {
unsigned int minNumber;
unsigned int maxNumber;
unsigned int ranNumber;
minNumber=[self.textFieldFrom.text intValue]; //getting numbers from my textfields
maxNumber=[self.textFieldTo.text intValue]; //Should i use unsigned intValue?
ranNumber=rand()%(maxNumber-minNumber+1)+minNumber;
NSString *str = [NSString stringWithFormat:#"%d", ranNumber];
self.label.text = str;
}
and this will view : 2147483647 as a maximum value.
what's wrong? should i use unsigned intValue when i getting numbers from my textFields?
Jonathan
here you can read about this number. : http://en.wikipedia.org/wiki/2147483647
The problem is intValue which returns a int (not an unsigned int) and is maxed out at 2,147,483,647. If you need larger than INT32_MAX, then use long variables and NSString method longLongValue instead of intValue.
Yes, %d is signed, but if you use %u that will not solve the problem with intValue. Using long long variables and longlongValue method will solve this. For example:
NSString *string = #"2147483650";
unsigned int i = [string intValue];
NSLog(#"i = %u", i); // returns 2147483647
NSUInteger j = [string integerValue];
NSLog(#"j = %u", j); // returns 2147483647
long long k = [string longLongValue];
NSLog(#"k = %lld", k); // returns 2147483650
So, looking at your original code, it might be:
long long minNumber;
long long maxNumber;
long long ranNumber;
minNumber = [self.textFieldFrom.text longLongValue];
maxNumber = [self.textFieldTo.text longLongValue];
ranNumber = arc4random_uniform(maxNumber-minNumber+1) + minNumber;
NSString *str = [NSString stringWithFormat:#"%lld", ranNumber];
self.label.text = str;
%d modifier is parsed as signed integer.