sanitizer_common: make parsing of smaps testable (NFC)

[dvyukov]

Summary

Move parsing of /proc/self/smaps into a separate function
so that it can be tested.

Depends on D112788.

compiler-rt/lib/sanitizer_common/sanitizer_common.h

 
 typedef void (*fill_profile_f)(uptr start, uptr rss, bool file,
                                /*out*/uptr *stats, uptr stats_size);
 
 // Parse the contents of /proc/self/smaps and generate a memory profile.
 // |cb| is a tool-specific callback that fills the |stats| array containing
 // |stats_size| elements.
 void GetMemoryProfile(fill_profile_f cb, uptr *stats, uptr stats_size);
+void ParseUnixMemoryProfile(fill_profile_f cb, uptr *stats, uptr stats_size,
+                            const char *smaps, uptr smaps_len);
 
 // Simple low-level (mmap-based) allocator for internal use. Doesn't have
 // constructor, so all instances of LowLevelAllocator should be
 // linker initialized.
 class LowLevelAllocator {
  public:
   // Requires an external lock.
   void *Allocate(uptr size);

compiler-rt/lib/sanitizer_common/sanitizer_procmaps_common.cpp

 }
 
 void GetMemoryProfile(fill_profile_f cb, uptr *stats, uptr stats_size) {
   char *smaps = nullptr;
   uptr smaps_cap = 0;
   uptr smaps_len = 0;
   if (!ReadFileToBuffer("/proc/self/smaps", &smaps, &smaps_cap, &smaps_len))
     return;
+  ParseUnixMemoryProfile(cb, stats, stats_size, smaps, smaps_len);
+  UnmapOrDie(smaps, smaps_cap);
+}
+
+void ParseUnixMemoryProfile(fill_profile_f cb, uptr *stats, uptr stats_size,
+                            const char *smaps, uptr smaps_len) {
   uptr start = 0;
   bool file = false;
   const char *pos = smaps;
   while (pos < smaps + smaps_len) {
     if (IsHex(pos[0])) {
       start = ParseHex(&pos);
       for (; *pos != '/' && *pos > '\n'; pos++) {}
       file = *pos == '/';
     } else if (internal_strncmp(pos, "Rss:", 4) == 0) {
       while (!IsDecimal(*pos)) pos++;
       uptr rss = ParseDecimal(&pos) * 1024;
       cb(start, rss, file, stats, stats_size);
     }
     while (*pos++ != '\n') {}
   }
-  UnmapOrDie(smaps, smaps_cap);
 }
 
 } // namespace __sanitizer
 
 #endif