使用NSGlyph和内存分配 [英] Using NSGlyph and memory allocation

问题描述

在一个方法中，为 NSTextView visibleRect 频繁地跟踪换行符 strong> NSGlyph 以使用 NSLayoutManager getGlyphs：range：。

应该/我可以找出多少内存这应该是，因为我有范围的引用（不影响布局），以及什么样的清理应该发生 - 运行 ARC ？

代码（在主队列上运行）：

  NSLayoutManager * lm = [self.textView layoutManager]; 
 NSTextContainer * tc = [self.textView textContainer]; 
 NSRect vRect = [self.textView visibleRect]; 
 NSRange visibleRange = [lm glyphRangeForBoundingRectWithoutAdditionalLayout：vRect inTextContainer：tc]; 
 NSUInteger vRangeLoc = visibleRange.location; 
 NSUInteger numberOfLines; 
 NSUInteger index; 
 NSGlyph glyphArray [5000]; //< --- memory assigned here 
 NSUInteger numberOfGlyphs = [lm getGlyphs：glyphArray range：visibleRange]; 
 NSRange lineRange; 
 NSMutableIndexSet * idxset = [NSMutableIndexSet indexSet]; 
 for（numberOfLines = 0，index = 0; index< numberOfGlyphs; numberOfLines ++）{
（void）[lm lineFragmentRectForGlyphAtIndex：index effectiveRange：& lineRange withoutAdditionalLayout：YES]; 
 [idxset addIndex：lineRange.location + vRangeLoc]; 
 index = NSMaxRange（lineRange）; 
} 
 self.currentLinesIndexSet = idxset; 
   
 
解决方案
使用 NSGlyph glyphs [ 5000] 表示法，您正在分配堆栈上的内存。但是不是5000字形，它只需要保存 visibleRange.length + 1  glyphs：
 
 <   glyphArray   
 
 
 
在输出中，来自 glyphRange  $ b null终止。不会在结果中包含未显示的任何 NSNullGlyph 或
其他字形。传入的内存应该是大的
，至少 glyphRange.length + 1 元素。
 
 
因为它是在栈上，你不必担心释放内存 - 因为从来没有malloced内存;即使没有 ARC  
 
 
 
，它会工作，如果你这样写：
  NSLayoutManager * lm = ... 
 NSRange glyphRange = ... 
 NSGlyph glyphArray [glyphRange.length + 1] ; 
 NSUInteger numberOfGlyphs = [lm getGlyphs：glyphArray range：glyphRange]; 
 //与字形做某事
  
 
in a method to track line breaks frequently, for a NSTextView visibleRect, i am allocating memory for NSGlyph to use NSLayoutManager getGlyphs:range:.

should/can i find out how much memory this should be since i have a reference for the range (without affecting layout), and also, what kind of cleanup should happen -- running with ARC ?

the code (which runs on a main queue) :
    NSLayoutManager *lm = [self.textView layoutManager];
    NSTextContainer *tc = [self.textView textContainer];
    NSRect vRect = [self.textView visibleRect];
    NSRange visibleRange = [lm glyphRangeForBoundingRectWithoutAdditionalLayout:vRect inTextContainer:tc];
    NSUInteger vRangeLoc = visibleRange.location;
    NSUInteger numberOfLines;
    NSUInteger index;
    NSGlyph glyphArray[5000]; // <--- memory assigned here
    NSUInteger numberOfGlyphs = [lm getGlyphs:glyphArray range:visibleRange];
    NSRange lineRange;
    NSMutableIndexSet *idxset = [NSMutableIndexSet indexSet];
    for (numberOfLines = 0, index = 0; index < numberOfGlyphs; numberOfLines++) {
        (void)[lm lineFragmentRectForGlyphAtIndex:index effectiveRange:&lineRange withoutAdditionalLayout:YES];
        [idxset addIndex:lineRange.location + vRangeLoc];
        index = NSMaxRange(lineRange);
    }
    self.currentLinesIndexSet = idxset;

解决方案
With the NSGlyph glyphs[5000] notation, you're allocating the memory on the stack. But instead of 5000 glyphs it only has to hold visibleRange.length + 1 glyphs:

  
glyphArray
  
  
On output, the displayable glyphs from glyphRange,
  null-terminated. Does not include in the result any NSNullGlyph or
  other glyphs that are not shown. The memory passed in should be large
  enough for at least glyphRange.length+1 elements.
And because it is on the stack, you don't have to worry about freeing the memory—because never malloced memory; it is freed automatically when leaving the function—even without ARC

So it should work, if you write it like this:
NSLayoutManager *lm = ...
NSRange glyphRange = ...
NSGlyph glyphArray[glyphRange.length + 1];
NSUInteger numberOfGlyphs = [lm getGlyphs:glyphArray range:glyphRange];
// do something with your glyphs


                        
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