src/base/Here.h

   1 /*
   2  * Copyright (C) 1996-2020 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 #ifndef SQUID_BASE_HERE_H
  10 #define SQUID_BASE_HERE_H
  11
  12 #include <iosfwd>
  13
  14 /// source code location of the caller
  15 #define Here() SourceLocation(__FUNCTION__, __FILE__, __LINE__)
  16
  17 /// semi-uniquely identifies a source code location; stable across Squid runs
  18 typedef uint32_t SourceLocationId;
  19
  20 /// returns a hash of a file name
  21 typedef SourceLocationId FileNameHasher(const char *fileName);
  22
  23 /// a caching proxy for `hasher` results
  24 typedef SourceLocationId FileNameHashCacher(const char *fileName, FileNameHasher hasher);
  25
  26 static FileNameHashCacher UnitFileNameHashCacher;
  27
  28 /// a source code location that is cheap to create, copy, and store
  29 class SourceLocation
  30 {
  31 public:
  32     SourceLocation(const char *aContext, const char *aFileName, const int aLineNo):
  33         context(aContext),
  34         fileName(aFileName),
  35         lineNo(aLineNo),
  36         fileNameHashCacher(&UnitFileNameHashCacher)
  37     {}
  38
  39     /// \returns our location identifier
  40     SourceLocationId id() const;
  41
  42     /// describes location using a compact but human-friendly format
  43     std::ostream &print(std::ostream &os) const;
  44
  45     const char *context; ///< line-independent location description
  46     const char *fileName; ///< source file name, often relative to build path
  47     int lineNo; ///< line number inside the source file name (if positive)
  48
  49 private:
  50     SourceLocationId calculateId(FileNameHasher) const;
  51     FileNameHashCacher *fileNameHashCacher;
  52 };
  53
  54 inline std::ostream &
  55 operator <<(std::ostream &os, const SourceLocation &location)
  56 {
  57     return location.print(os);
  58 }
  59
  60 /// SourceLocation::id() speed optimization hack: Caches `hasher` results. The
  61 /// cache capacity is one filename hash. Each translation unit gets one cache.
  62 static SourceLocationId
  63 UnitFileNameHashCacher(const char *fileName, FileNameHasher hasher)
  64 {
  65     static SourceLocationId cachedHash = 0;
  66     static const char *hashedFilename = 0;
  67     // Each file #included in a translation unit has its own __FILE__ value.
  68     // Keep the cache fresh (and the result correct).
  69     if (hashedFilename != fileName) { // cheap pointer comparison
  70         hashedFilename = fileName;
  71         cachedHash = hasher(fileName);
  72     }
  73     return cachedHash;
  74 }
  75
  76 #endif
  77