In Objetive-C when I want set/change value of pointer. I use
*pointer = value
But In Swift, how to get/set value of pointer?
I'm woking with bitmap pixel:
NSUInteger offsetPixelCountForInput = ghostOrigin.y * inputWidth + ghostOrigin.x;
for (NSUInteger j = 0; j < ghostSize.height; j++) {
for (NSUInteger i = 0; i < ghostSize.width; i++) {
UInt32 * inputPixel = inputPixels + j * inputWidth + i + offsetPixelCountForInput;
UInt32 inputColor = *inputPixel;
newR = MAX(0,MIN(255, newR));
newG = MAX(0,MIN(255, newG));
newB = MAX(0,MIN(255, newB));
*inputPixel = RGBAMake(newR, newG, newB, A(inputColor));
}
}
So I want to convert this code into Swift, but I'm stuck with pointers.
23.03.2016 - Update code
var inputPixels:UnsafeMutablePointer<UInt32> = nil
inputPixels = UnsafeMutablePointer<UInt32>(calloc(inputHeight * inputWidth, UInt(sizeof(UInt32))))
You can work with pointers in Swift. There are UnsafePointer and UnsafeMutablePointer generic types.
Here is a function that takes a float pointer
You can use float variable and pass it's address &floatVar
or you can create and allocate an UnsafeMutablePointer and pass it. But you have to manually allocate and deallocate memory.
When you work with an UnsafeMutablePointer pointer type and want to assign some value to it you have to do the following:
check if points to some variable (not nil)
Assign your value to the memory property
Code Example:
func work (p: UnsafeMutablePointer<Float>) {
if p != nil {
p.memory = 10
}
println(p)
println(p.memory)
}
var f: Float = 0.0
var fPointer: UnsafeMutablePointer<Float> = UnsafeMutablePointer.alloc(1)
work(&f)
work(fPointer)
fPointer.dealloc(1)
You should use pointee property instead of memory in Swift 3
pointer.pointee = value
Related
I am trying to implement Variable Rate Shading in the app based on DirectX 11.
I am doing it this way:
UINT dwRtWidth = 2560;
UINT dwRtHeight = 1440;
D3D11_TEXTURE2D_DESC srcDesc;
ZeroMemory(&srcDesc, sizeof(srcDesc));
int sri_w = dwRtWidth / NV_VARIABLE_PIXEL_SHADING_TILE_WIDTH;
int sri_h = dwRtHeight / NV_VARIABLE_PIXEL_SHADING_TILE_HEIGHT;
srcDesc.Width = sri_w;
srcDesc.Height = sri_h;
srcDesc.ArraySize = 1;
srcDesc.Format = DXGI_FORMAT_R8_UINT;
srcDesc.SampleDesc.Count = 1;
srcDesc.SampleDesc.Quality = 0;
srcDesc.Usage = D3D11_USAGE_DEFAULT; //Optional
srcDesc.BindFlags = D3D11_BIND_SHADER_RESOURCE; //Optional
srcDesc.CPUAccessFlags = 0;
srcDesc.MiscFlags = 0;
D3D11_SUBRESOURCE_DATA initialData;
UINT* data = (UINT*)malloc(sri_w * sri_h * sizeof(UINT));
for (int i = 0; i < sri_w * sri_h; i++)
data[i] = (UINT)0;
initialData.pSysMem = data;
initialData.SysMemPitch = sri_w;
//initialData.SysMemSlicePitch = 0;
HRESULT hr = s_device->CreateTexture2D(&srcDesc, &initialData, &pShadingRateSurface);
if (FAILED(hr))
{
LOG("Texture not created");
LOG(std::system_category().message(hr));
}
else
LOG("Texture created");
When I try to create texture with initial data, it is not being created and HRESULTS gives message: 'The parameter is incorrect'. Doesn't say which one.
When I create texture without initial data it's created successfully.
What's wrong with the initial data? I also tried to use unsigned char instead of UINT as it has 8 bits, but result was the same, texture was not created.
Please help.
Aftr some time I found a solution to the problem. I needed to add a line:
srcDesc.MipLevels = 1;
With this change the texture was finally created with initial data
I'm coming from Swift to Objective-C and a problem I have run into is that NSData doesn't seem have methods to enumerate over UInt8 values the way Swift's Data does. Other answers with similar titles exist but they all deal with property lists, whereas I just have a bucket of ASCII bytes. Specifically, the code I want to replicate in Obj-C is:
//Find the next newline in ASCII data given a byte offset
let subset = myData.advanced(by: offset)
var lineEnd: Data.Index = myData.endIndex
subset.enumerateBytes({ (memory, idx, stop) in
let newline: UInt8 = 10
for idx in memory.indices {
let charByte = memory[idx]
if charByte == newline {
lineEnd = idx
stop = true; return;
}
}
})
Ideally I want a way to convert an NSArray to an array of NSNumbers which I can extract the intValues from. Of course, if there is a better method, let me know. A goal is to keep the Obj-C code as similar to Swift as possible as I will be maintaining the two codebases simultaneously.
The only good way to access an NSData's bytes is to call its -bytes method, which gets you a C pointer to its internal storage.
NSData *data = ...;
const uint8_t *bytes = data.bytes;
NSUInteger length = data.length;
for (NSUInteger i = 0; i < length; i++) {
uint8_t byte = bytes[i];
// do something with byte
}
The closest equivalent to advance would be subdataWithRange. The equivalent to enumerateBytes is enumerateByteRangesUsingBlock. It would yield something like:
NSData *subset = [data subdataWithRange:NSMakeRange(offset, data.length - offset)];
__block NSUInteger lineEnd = data.length;
Byte newline = 10;
[subset enumerateByteRangesUsingBlock:^(const void * _Nonnull bytes, NSRange byteRange, BOOL * _Nonnull stop) {
for (NSInteger index = 0; index < byteRange.length; index++) {
Byte charByte = ((Byte *)bytes)[index];
if (charByte == newline) {
lineEnd = index + byteRange.location;
*stop = true;
return;
}
}
}];
Note, I made a few changes from your Swift example:
If the data was not contiguous, your Swift example returns the index within the current block. But I suspect you want the location within subset, not the current block. I'm wagering that you've never noticed this because it's pretty rare that NSData blocks are not continuous.
But the Swift code doesn't look correct to me. This Objective-C example reports the offset within subset, not within the current block within subset.
It's not observable performance difference, but I pulled the definition of newline out of the enumeration block. Why repeatedly define that?
If you're really searching for a character in the NSData, I'd suggest avoiding creating the subset altogether. Just use rangeOfData:options:range:. This will find whatever you're looking for.
I am re-writing the particle filter library of iOS in Swift from Objective C which is available on Bitbucket and I have a question regarding a syntax of Objective C which I cannot understand.
The code goes as follows:
- (void)setRssi:(NSInteger)rssi {
_rssi = rssi;
// Ignore zeros in average, StdDev -- we clear the value before setting it to
// prevent old values from hanging around if there's no reading
if (rssi == 0) {
self.meters = 0;
return;
}
self.meters = [self metersFromRssi:rssi];
NSInteger* pidx = self.rssiBuffer;
*(pidx+self.bufferIndex++) = rssi;
if (self.bufferIndex >= RSSIBUFFERSIZE) {
self.bufferIndex %= RSSIBUFFERSIZE;
self.bufferFull = YES;
}
if (self.bufferFull) {
// Only calculate trailing mean and Std Dev when we have enough data
double accumulator = 0;
for (NSInteger i = 0; i < RSSIBUFFERSIZE; i++) {
accumulator += *(pidx+i);
}
self.meanRssi = accumulator / RSSIBUFFERSIZE;
self.meanMeters = [self metersFromRssi:self.meanRssi];
accumulator = 0;
for (NSInteger i = 0; i < RSSIBUFFERSIZE; i++) {
NSInteger difference = *(pidx+i) - self.meanRssi;
accumulator += difference*difference;
}
self.stdDeviationRssi = sqrt( accumulator / RSSIBUFFERSIZE);
self.meanMetersVariance = ABS(
[self metersFromRssi:self.meanRssi]
- [self metersFromRssi:self.meanRssi+self.stdDeviationRssi]
);
}
}
The class continues with more code and functions which are not important and what I do not understand are these two lines
NSInteger* pidx = self.rssiBuffer;
*(pidx+self.bufferIndex++) = rssi;
Variable pidx is initialized to the size of a buffer which was previously defined and then in the next line the size of that buffer and buffer plus one is equal to the RSSI variable which is passed as a parameter in the function.
I assume that * has something to do with reference but I just can't figure out the purpose of this line. Variable pidx is used only in this function for calculating trailing mean and standard deviation.
Let explain those code:
NSInteger* pidx = self.rssiBuffer; means that you are getting pointer of the first value of the buffer.
*(pidx+self.bufferIndex++) = rssi; means that you are setting the value of the buffer at index 0+self.bufferIndex to rssiand then increase bufferIndex by 1. Thanks to #Jakub Vano point it out.
In C++, it will look like that
int self.rssiBuffer[1000]; // I assume we have buffer like that
self.rssiBuffer[self.bufferIndex++] = rssi
- (IBAction)convert_button:(id)sender {
NSString * binary_input = _binary_field.text;
if(binary_input!=NULL)
{
int count, total, i, j, tmp;
total = 0;
count = binary_input.length;
for (i = 0; i <= count; i++) {
if (binary_input[count-i] == '1') {//error here saying Expected method to read array element not found of object type 'NSString *'
tmp = 1;
for (j = 1; j < i; j++)
tmp *= 2;
total += tmp;
}
}
long decimal_value = strtol([binary_input UTF8String], NULL, 2);
NSString *resultString = [[NSString alloc]
initWithFormat: #"%li", decimal_value];
_decimal_output.text = resultString;
}
}
I am getting an error as commented in the code at my if statement that error says Expected method to read array element not found of object type 'NSString *'
I am new to objective-c and have mainly have done c++, any help is appreciated in how to fix the error, the logic makes sense to me.
for (i = 0; i <= count; i++) {
if (binary_input[count-i] == '1')
In your first iteration through the loop, you'll be looking for the element in spot -1, which is outside the bounds of an array.
ArrayList a = new ArrayList();
for(int i = 0; i < a.size(), i++)
{
float f = float(a.get(i)); // ERROR : cant convert Object to float
}
Processing is a simpler java, so you can use the java syntax:
ArrayList<Float> a = new ArrayList<Float>();
a.add(1.0f); // "Autobox" a float into a Float object, adding it to the array
for (int i = 0; i < a.size(); i++)
{
float f = a.get(i); // "Unbox" the Float object
}
Lookup autoboxing/unboxing.
Must not be .NET, otherwise would be i < a.count;
float f = (float)(a.get(i)); ??