talk-ios/NextcloudTalk/ScreenCapturer.m

// From https://github.com/react-native-webrtc/react-native-webrtc (MIT License)
// SPDX-FileCopyrightText: 2023 React-Native-WebRTC authors
// SPDX-License-Identifier: MIT

#include <mach/mach_time.h>

#import <ReplayKit/ReplayKit.h>
#import <WebRTC/RTCCVPixelBuffer.h>
#import <WebRTC/RTCVideoFrameBuffer.h>

#import "ScreenCapturer.h"
#import "SocketConnection.h"

#import "NextcloudTalk-Swift.h"

const NSUInteger kMaxReadLength = 10 * 1024;

@interface Message : NSObject

@property(nonatomic, assign, readonly) CVImageBufferRef imageBuffer;
@property(nonatomic, copy, nullable) void (^didComplete)(BOOL succes, Message *message);

- (NSInteger)appendBytes:(UInt8 *)buffer length:(NSUInteger)length;

@end

@interface Message ()

@property(nonatomic, assign) CVImageBufferRef imageBuffer;
@property(nonatomic, assign) int imageOrientation;
@property(nonatomic, assign) CFHTTPMessageRef framedMessage;

@end

@implementation Message

- (instancetype)init {
    self = [super init];
    if (self) {
        self.imageBuffer = NULL;
    }

    return self;
}

- (void)dealloc {
    CVPixelBufferRelease(_imageBuffer);
}

/** Returns the amount of missing bytes to complete the message, or -1 when not enough bytes were provided to compute
 * the message length */
- (NSInteger)appendBytes:(UInt8 *)buffer length:(NSUInteger)length {
    if (!_framedMessage) {
        _framedMessage = CFHTTPMessageCreateEmpty(kCFAllocatorDefault, false);
    }

    CFHTTPMessageAppendBytes(_framedMessage, buffer, length);
    if (!CFHTTPMessageIsHeaderComplete(_framedMessage)) {
        return -1;
    }

    NSInteger contentLength =
        [CFBridgingRelease(CFHTTPMessageCopyHeaderFieldValue(_framedMessage, (__bridge CFStringRef) @"Content-Length"))
            integerValue];
    NSInteger bodyLength = (NSInteger)[CFBridgingRelease(CFHTTPMessageCopyBody(_framedMessage)) length];

    NSInteger missingBytesCount = contentLength - bodyLength;
    if (missingBytesCount == 0) {
        BOOL success = [self unwrapMessage:self.framedMessage];
        self.didComplete(success, self);

        CFRelease(self.framedMessage);
        self.framedMessage = NULL;
    }

    return missingBytesCount;
}

// MARK: Private Methods

- (CIContext *)imageContext {
    // Initializing a CIContext object is costly, so we use a singleton instead
    static CIContext *imageContext = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        imageContext = [[CIContext alloc] initWithOptions:nil];
    });

    return imageContext;
}

- (BOOL)unwrapMessage:(CFHTTPMessageRef)framedMessage {
    size_t width =
        [CFBridgingRelease(CFHTTPMessageCopyHeaderFieldValue(_framedMessage, (__bridge CFStringRef) @"Buffer-Width"))
            integerValue];
    size_t height =
        [CFBridgingRelease(CFHTTPMessageCopyHeaderFieldValue(_framedMessage, (__bridge CFStringRef) @"Buffer-Height"))
            integerValue];
    _imageOrientation = [CFBridgingRelease(
        CFHTTPMessageCopyHeaderFieldValue(_framedMessage, (__bridge CFStringRef) @"Buffer-Orientation")) intValue];

    NSData *messageData = CFBridgingRelease(CFHTTPMessageCopyBody(_framedMessage));

    // Copy the pixel buffer
    CVReturn status =
        CVPixelBufferCreate(kCFAllocatorDefault, width, height, kCVPixelFormatType_32BGRA, NULL, &_imageBuffer);
    if (status != kCVReturnSuccess) {
        NSLog(@"CVPixelBufferCreate failed");
        return false;
    }

    [self copyImageData:messageData toPixelBuffer:&_imageBuffer];

    return true;
}

- (void)copyImageData:(NSData *)data toPixelBuffer:(CVPixelBufferRef *)pixelBuffer {
    CVPixelBufferLockBaseAddress(*pixelBuffer, 0);

    CIImage *image = [CIImage imageWithData:data];
    [self.imageContext render:image toCVPixelBuffer:*pixelBuffer];

    CVPixelBufferUnlockBaseAddress(*pixelBuffer, 0);
}

@end

// MARK: -

@interface ScreenCapturer ()<NSStreamDelegate>

@property(nonatomic, strong) SocketConnection *connection;
@property(nonatomic, strong) Message *message;

@end

@implementation ScreenCapturer {
    mach_timebase_info_data_t _timebaseInfo;
    NSInteger _readLength;
    int64_t _startTimeStampNs;
}

- (instancetype)initWithDelegate:(__weak id<RTCVideoCapturerDelegate>)delegate {
    self = [super initWithDelegate:delegate];
    if (self) {
        mach_timebase_info(&_timebaseInfo);
    }

    return self;
}

- (void)setConnection:(SocketConnection *)connection {
    if (_connection != connection) {
        [_connection close];
        _connection = connection;
    }
}

- (void)startCaptureWithConnection:(SocketConnection *)connection {
    mach_timebase_info(&_timebaseInfo);
    _startTimeStampNs = -1;

    self.connection = connection;
    self.message = nil;

    [self.connection openWithStreamDelegate:self];
}

- (void)stopCapture {
    self.connection = nil;
}

// MARK: Private Methods

- (void)readBytesFromStream:(NSInputStream *)stream {
    if (!stream.hasBytesAvailable) {
        return;
    }

    if (!self.message) {
        self.message = [[Message alloc] init];
        _readLength = kMaxReadLength;

        __weak __typeof__(self) weakSelf = self;
        self.message.didComplete = ^(BOOL success, Message *message) {
            if (success) {
                [weakSelf didCaptureVideoFrame:message.imageBuffer withOrientation:message.imageOrientation];
            }

            weakSelf.message = nil;
        };
    }

    uint8_t buffer[_readLength];
    NSInteger numberOfBytesRead = [stream read:buffer maxLength:_readLength];
    if (numberOfBytesRead < 0) {
        NSLog(@"error reading bytes from stream");
        return;
    }

    _readLength = [self.message appendBytes:buffer length:numberOfBytesRead];
    if (_readLength == -1 || _readLength > kMaxReadLength) {
        _readLength = kMaxReadLength;
    }
}

- (void)didCaptureVideoFrame:(CVPixelBufferRef)pixelBuffer withOrientation:(CGImagePropertyOrientation)orientation {
    int64_t currentTime = mach_absolute_time();
    int64_t currentTimeStampNs = currentTime * _timebaseInfo.numer / _timebaseInfo.denom;

    if (_startTimeStampNs < 0) {
        _startTimeStampNs = currentTimeStampNs;
    }

    RTCCVPixelBuffer *rtcPixelBuffer = [[RTCCVPixelBuffer alloc] initWithPixelBuffer:pixelBuffer];
    int64_t frameTimeStampNs = currentTimeStampNs - _startTimeStampNs;

    RTCVideoRotation rotation;
    switch (orientation) {
        case kCGImagePropertyOrientationLeft:
            rotation = RTCVideoRotation_90;
            break;
        case kCGImagePropertyOrientationDown:
            rotation = RTCVideoRotation_180;
            break;
        case kCGImagePropertyOrientationRight:
            rotation = RTCVideoRotation_270;
            break;
        default:
            rotation = RTCVideoRotation_0;
            break;
    }

    RTCVideoFrame *videoFrame = [[RTCVideoFrame alloc] initWithBuffer:rtcPixelBuffer
                                                             rotation:rotation
                                                          timeStampNs:frameTimeStampNs];

    [self.delegate capturer:self didCaptureVideoFrame:videoFrame];
}

@end

@implementation ScreenCapturer (NSStreamDelegate)

- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode {
    switch (eventCode) {
        case NSStreamEventOpenCompleted:
            NSLog(@"server stream open completed");
            break;
        case NSStreamEventHasBytesAvailable:
            [self readBytesFromStream:(NSInputStream *)aStream];
            break;
        case NSStreamEventEndEncountered:
            NSLog(@"server stream end encountered");
            [self stopCapture];
            [self.eventsDelegate capturerDidEnd:self];
            break;
        case NSStreamEventErrorOccurred:
            NSLog(@"server stream error encountered: %@", aStream.streamError.localizedDescription);
            break;

        default:
            break;
    }
}

@end