我能够将std :: vector数据存储和恢复到NSData并返回,但是,它会间歇性地工作。我最初发布了这个问题并接受了答案,因为它似乎在这里工作:
Storing and Restoring std::vector from NSData
但是,有时它会起作用,有时会导致EXC_BAD_ACCESS错误。我创建了一个示例Xcode项目,它可以重现可以从这里下载的问题:
http://3DTOPO.com/VectorToData.zip
有时它会在测试迭代33,47或105中崩溃。
以下是崩溃时的回溯:
* thread #1: tid = 0x1542ee1, 0x000000010d45e65e libsystem_platform.dylib`_platform_memmove$VARIANT$Nehalem + 254, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x7faf29000000)
frame #0: 0x000000010d45e65e libsystem_platform.dylib`_platform_memmove$VARIANT$Nehalem + 254
frame #1: 0x0000000109f46753 Foundation`_NSDataCreateVMDispatchData + 131
frame #2: 0x0000000109f44cf2 Foundation`-[_NSPlaceholderData initWithBytes:length:copy:deallocator:] + 230
frame #3: 0x0000000109f50902 Foundation`-[NSData(NSData) initWithBytes:length:] + 37
* frame #4: 0x0000000109ea2bfe VectorToData`storeContourData() + 574 at ViewController.mm:86
frame #5: 0x0000000109ea2943 VectorToData`-[ViewController viewDidLoad](self=0x00007faf3a10f410, _cmd="viewDidLoad") + 1443 at ViewController.mm:67
frame #6: 0x000000010af31984 UIKit`-[UIViewController loadViewIfRequired] + 1198
frame #7: 0x000000010af31cd3 UIKit`-[UIViewController view] + 27
frame #8: 0x000000010ae07fb4 UIKit`-[UIWindow addRootViewControllerViewIfPossible] + 61
frame #9: 0x000000010ae0869d UIKit`-[UIWindow _setHidden:forced:] + 282
frame #10: 0x000000010ae1a180 UIKit`-[UIWindow makeKeyAndVisible] + 42
frame #11: 0x000000010ad8eed9 UIKit`-[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 4131
frame #12: 0x000000010ad95568 UIKit`-[UIApplication _runWithMainScene:transitionContext:completion:] + 1769
frame #13: 0x000000010ad92714 UIKit`-[UIApplication workspaceDidEndTransaction:] + 188
frame #14: 0x000000010d78a8c8 FrontBoardServices`__FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 24
frame #15: 0x000000010d78a741 FrontBoardServices`-[FBSSerialQueue _performNext] + 178
frame #16: 0x000000010d78aaca FrontBoardServices`-[FBSSerialQueue _performNextFromRunLoopSource] + 45
frame #17: 0x000000010a905301 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
frame #18: 0x000000010a8fb22c CoreFoundation`__CFRunLoopDoSources0 + 556
frame #19: 0x000000010a8fa6e3 CoreFoundation`__CFRunLoopRun + 867
frame #20: 0x000000010a8fa0f8 CoreFoundation`CFRunLoopRunSpecific + 488
frame #21: 0x000000010ad91f21 UIKit`-[UIApplication _run] + 402
frame #22: 0x000000010ad96f09 UIKit`UIApplicationMain + 171
frame #23: 0x0000000109ea237f VectorToData`main(argc=1, argv=0x00007fff55d5d6e0) + 111 at main.m:14
frame #24: 0x000000010d12a92d libdyld.dylib`start + 1
虽然首选使用NSData,但我愿意使用C ++解决方案,但我发现我无法在iOS上工作的示例(例如fstream和iostream)。如果提供了C ++解决方案,请说明如何恢复数据以及存储数据。
如果您无法打开上面链接的项目,这里是相关的代码,只需将其命名为ViewController.mm并将其放入新的Single View Application Xcode项目中:
//
// ViewController.m
// VectorToData
//
// Created by jeshua on 8/27/16.
// Copyright © 2016 3DTOPO Inc. All rights reserved.
//
#import "ViewController.h"
#import <vector>
using namespace std;
typedef vector<CGPoint> CGContour;
typedef vector<CGContour> CGContours;
const size_t cgContourSize = sizeof(CGContour);
static CGContours contoursVector;
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
for (int testNumber = 0; testNumber < 1000; testNumber++) {
NSLog(@"__________ Test Number: %d __________", testNumber);
long numberOfContours = arc4random_uniform(2000) + 1000;
contoursVector.clear();
contoursVector = CGContours(numberOfContours);
long numberOfBytesGenerated = 0;
for( int contourNum = 0; (contourNum < numberOfContours); contourNum++ ) {
long contourPointCount = arc4random_uniform(5000) + 1;
CGContour thisContour = CGContour(contourPointCount);
for( long pointNum = 0; pointNum < thisContour.size(); pointNum++ )
{
thisContour[pointNum] = CGPointMake(arc4random_uniform(800), arc4random_uniform(1200));
}
//This might seem redundant, but in my actual code the data is converted to CGPoints here
//and is not already a CGPoint
contoursVector[contourNum] = CGContour(contourPointCount);
for( long pointNum = 0; pointNum < thisContour.size(); pointNum++ )
{
contoursVector[contourNum][pointNum] = thisContour[pointNum];
numberOfBytesGenerated += cgContourSize;
}
}
NSLog(@" numberContoursGenerated: %lu, numberOfBytesGenerated: %lu", numberOfContours, numberOfBytesGenerated);
storeContourData();
NSLog(@"\n\n");
}
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
void storeContourData() {
NSMutableArray<NSData *> *contourDataArray = [NSMutableArray new];
long numberContoursStored = 0;
long numberOfBytesStored = 0;
for(const CGContour &contour : contoursVector)
{
// Both these data initializations seem to work the same
NSData *data = [[NSData alloc] initWithBytes:&contour[0]
length:contour.size() * cgContourSize];
// NSData *data = [[NSData alloc] initWithBytes:contour.data()
// length:contour.size() * cgContourSize];
[contourDataArray addObject:data];
numberContoursStored++;
numberOfBytesStored += contour.size() * cgContourSize;
}
NSLog(@" numberContoursStored: %lu, numberOfBytesStored: %lu", numberContoursStored, numberOfBytesStored);
}
@end
答案 0 :(得分:0)
问题是轮廓字节大小的错误计算,它不是
contour.size() * cgContourSize; // sizeof(vector<CGPoint>)
但应该是
contour.size() * sizeof(CGPoint);
您无法预先计算向量(或其他数据容器)的字节大小。
应该避免这样的陈述:
sizeof(vector<...>);
因为结果是矢量对象的 byte 大小,而不是矢量中数据的 byte 大小。