src/base/Here.cc

   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 #include "squid.h"
  10 #include "base/Here.h"
  11
  12 #include <iostream>
  13
  14 /* File name hashing helpers */
  15
  16 // Build prefix is the file system path leading to Squid src/ source directory.
  17 // It is "." for in-tree builds but may be lengthy and sensitive otherwise.
  18
  19 /// \returns the build prefix length or, if estimation is not possible, zero
  20 static size_t
  21 BuildPrefixLength()
  22 {
  23     // The hard-coded tail must be kept in sync with this file actual name!
  24     const char *tail = "src/base/Here.cc";
  25     const char *full = __FILE__;
  26
  27     // Disable heuristic if it does not work.
  28     if (strstr(full, tail) == 0)
  29         return 0;
  30
  31     return strlen(full) - strlen(tail);
  32 }
  33
  34 /// \returns filename portion without the build prefix
  35 static const char *
  36 SkipBuildPrefix(const char* path)
  37 {
  38     static const size_t ToSkip = BuildPrefixLength();
  39     return path + ToSkip;
  40 }
  41
  42 /// quickly computes a (weak) hash of a file name
  43 static SourceLocationId
  44 FileNameHash(const char *path)
  45 {
  46     // Keep in sync with FileNameHash() in scripts/calc-must-ids.pl!
  47
  48     const char *name = strrchr(path, '/');
  49     if (name)
  50         ++name; // skip '/'
  51     else
  52         name = path;
  53
  54     uint32_t hash = 0;
  55     uint32_t iterations = 0;
  56     while (*name) {
  57         ++iterations;
  58         hash ^= 271 * static_cast<uint32_t>(*name);
  59         ++name;
  60     }
  61     return hash ^ (iterations * 271);
  62 }
  63
  64 /* SourceLocation */
  65
  66 SourceLocationId
  67 SourceLocation::id() const
  68 {
  69     const auto fnameHashFull = fileNameHashCacher(fileName, &FileNameHash);
  70     // 32 bits = 18 bits for the filename hash + 14 bits for the line number.
  71     // Keep in sync with ComputeMustIds() in scripts/calc-must-ids.pl.
  72     const auto fnameHash = fnameHashFull % 0x3FFFF;
  73     return (fnameHash << 14) | (lineNo & 0x3FFF);
  74 }
  75
  76 std::ostream &
  77 SourceLocation::print(std::ostream &os) const
  78 {
  79     if (fileName) {
  80         os << SkipBuildPrefix(fileName);
  81
  82         // TODO: Use more common and search-friendlier fileName:lineNo: format.
  83         if (lineNo > 0)
  84             os << '(' << lineNo << ')';
  85     }
  86     if (context) {
  87         if (fileName)
  88             os << ' ';
  89         os << context;
  90     }
  91     return os;
  92 }
  93