开发小记

Posted on Edited on In

开发中的小笔记。记录开发中的点滴滴点。

批量替换json文件中的注释

备份至.bat

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$ perl -i.bat -lpe 's/\/\/[^"]+$//g' xx

批量正则替换的另一种思路

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#!/base/sh
find . -name '*.swift' | while read file; do
  perl -i -lpe 's/if \(([^\)].*)\) \{/if $1 \{/g' $file
done

批量删除空格组成的空行中的空格

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#!/base/sh
find . -name '*.swift' | while read file; do
  sed -i '' 's/^[[:space:]][[:space:]]*$//g' $file
done

获取代码执行时间

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#import <mach/mach_time.h>
static NSMutableDictionary *__times;
static inline void debug_start_of(NSString *key)
{
  __times = __times ?: [NSMutableDictionary new];

  uint64_t start = mach_absolute_time();
  __times[key] = @(start);
}
static inline void debug_stop_of(NSString *key)
{
  if (__times) {
    uint64_t end = mach_absolute_time();
    uint64_t start = [__times[key] unsignedLongLongValue];
    if (start != 0) {
      uint64_t elapsed = end - start;
      mach_timebase_info_data_t info;
      if (mach_timebase_info(&info) != KERN_SUCCESS) {
        printf("mach_timebase_info failed\n");
      }
      uint64_t nanosecs = elapsed * info.numer / info.denom;
      uint64_t millisecs = nanosecs / 1000000;

      printf("[DEBUG code rt] %s:%llu ms\n", [key cStringUsingEncoding:NSUTF8StringEncoding], millisecs);
    } else {
      printf("[DEBUG code rt] %s error: no start\n", [key cStringUsingEncoding:NSUTF8StringEncoding]);
    }
  }
}

NAN

  • A对B除余时，如果B == 0 则会造成NAN，truncatingRemainder(dividingBy:)是swift的方法，也会造成此问题

  • 当NSUInteger 0 - 1时，运算结果为 NAN，iOS中有一个宏isnan(x)返回是否为nan。另外这里有一篇文章Objective-C 中 判断 NaN大致记录了一下

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    //  math.h  #56

    #if defined(__GNUC__)
    #   define    HUGE_VAL     __builtin_huge_val()
    #   define    HUGE_VALF    __builtin_huge_valf()
    #   define    HUGE_VALL    __builtin_huge_vall()
    #   define    NAN          __builtin_nanf("0x7fc00000")
    #else
    #   define    HUGE_VAL     1e500
    #   define    HUGE_VALF    1e50f
    #   define    HUGE_VALL    1e5000L
    #   define    NAN          __nan()
    #endif

  • 另外，NAN不能直接判断 == 需要调用下面的宏。否则会发生莫名其妙的问题

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      //  math.h  #178

    #define isnan(x)                                                         \
        ( sizeof(x) == sizeof(float)  ? __inline_isnanf((float)(x))          \
        : sizeof(x) == sizeof(double) ? __inline_isnand((double)(x))         \
                                      : __inline_isnanl((long double)(x)))