Update vlog_is_on.cc

src/vlog_is_on.cc

@@ -36,6 +36,7 @@
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
+#include <limits>
 #include <mutex>
 #include <string>
 
@@ -50,121 +51,116 @@ namespace google {
 
 inline namespace glog_internal_namespace_ {
 
-// Implementation of fnmatch that does not need 0-termination
-// of arguments and does not allocate any memory,
-// but we only support "*" and "?" wildcards, not the "[...]" patterns.
-// It's not a static function for the unittest.
+// Optimized implementation of fnmatch that does not require 0-termination
+// of its arguments and does not allocate any memory.
+// It supports only "*" and "?" wildcards.
+// This version is implemented iteratively rather than recursively.
 GLOG_NO_EXPORT bool SafeFNMatch_(const char* pattern, size_t patt_len,
                                  const char* str, size_t str_len) {
-  size_t p = 0;
-  size_t s = 0;
-  while (true) {
-    if (p == patt_len && s == str_len) return true;
-    if (p == patt_len) return false;
-    if (s == str_len) return p + 1 == patt_len && pattern[p] == '*';
-    if (pattern[p] == str[s] || pattern[p] == '?') {
-      p += 1;
-      s += 1;
-      continue;
-    }
-    if (pattern[p] == '*') {
-      if (p + 1 == patt_len) return true;
-      do {
-        if (SafeFNMatch_(pattern + (p + 1), patt_len - (p + 1), str + s,
-                         str_len - s)) {
-          return true;
-        }
-        s += 1;
-      } while (s != str_len);
+  size_t p = 0, s = 0;
+  // star_idx holds the index of the last '*' encountered.
+  // match_idx holds the index in str corresponding to that '*' match.
+  size_t star_idx = std::numeric_limits<size_t>::max();
+  size_t match_idx = 0;
+
+  while (s < str_len) {
+    if (p < patt_len && (pattern[p] == str[s] || pattern[p] == '?')) {
+      // Characters match (or we have a '?') so advance both indices.
+      ++p;
+      ++s;
+    } else if (p < patt_len && pattern[p] == '*') {
+      // Record the position of '*' and the current string index.
+      star_idx = p;
+      match_idx = s;
+      ++p;
+    } else if (star_idx != std::numeric_limits<size_t>::max()) {
+      // No direct match, but we have seen a '*' before.
+      // Backtrack: assume '*' matches one more character.
+      p = star_idx + 1;
+      s = ++match_idx;
+    } else {
+      // No match and no '*' to backtrack to.
       return false;
     }
-    return false;
   }
+
+  // Check for remaining '*' in the pattern.
+  while (p < patt_len && pattern[p] == '*') {
+    ++p;
+  }
+  return p == patt_len;
 }
 
 }  // namespace glog_internal_namespace_
 
 using glog_internal_namespace_::SafeFNMatch_;
 
-// List of per-module log levels from FLAGS_vmodule.
-// Once created each element is never deleted/modified
-// except for the vlog_level: other threads will read VModuleInfo blobs
-// w/o locks and we'll store pointers to vlog_level at VLOG locations
-// that will never go away.
-// We can't use an STL struct here as we wouldn't know
-// when it's safe to delete/update it: other threads need to use it w/o locks.
+// Structure holding per-module logging level info.
 struct VModuleInfo {
   string module_pattern;
-  mutable int32 vlog_level;  // Conceptually this is an AtomicWord, but it's
-                             // too much work to use AtomicWord type here
-                             // w/o much actual benefit.
+  mutable int32 vlog_level;  // Conceptually atomic but kept simple for performance.
   const VModuleInfo* next;
 };
 
-// This protects the following global variables.
+// Global variables controlling per-module logging levels.
 static std::mutex vmodule_mutex;
-// Pointer to head of the VModuleInfo list.
-// It's a map from module pattern to logging level for those module(s).
 static VModuleInfo* vmodule_list = nullptr;
 static SiteFlag* cached_site_list = nullptr;
-
-// Boolean initialization flag.
 static bool inited_vmodule = false;
 
-// L >= vmodule_mutex.
+// Initializes the module-specific logging levels based on FLAGS_vmodule.
 static void VLOG2Initializer() {
-  // Can now parse --vmodule flag and initialize mapping of module-specific
-  // logging levels.
   inited_vmodule = false;
   const char* vmodule = FLAGS_vmodule.c_str();
-  const char* sep;
   VModuleInfo* head = nullptr;
   VModuleInfo* tail = nullptr;
-  while ((sep = strchr(vmodule, '=')) != nullptr) {
+  while (*vmodule != '\0') {
+    const char* sep = strchr(vmodule, '=');
+    if (sep == nullptr) break;
     string pattern(vmodule, static_cast<size_t>(sep - vmodule));
     int module_level;
     if (sscanf(sep, "=%d", &module_level) == 1) {
       auto* info = new VModuleInfo;
       info->module_pattern = pattern;
       info->vlog_level = module_level;
+      info->next = nullptr;
       if (head) {
         tail->next = info;
       } else {
         head = info;
       }
       tail = info;
     }
-    // Skip past this entry
+    // Skip past this entry (find the next comma).
     vmodule = strchr(sep, ',');
     if (vmodule == nullptr) break;
-    vmodule++;  // Skip past ","
+    ++vmodule;  // Skip the comma.
   }
-  if (head) {  // Put them into the list at the head:
+  if (head) {
     tail->next = vmodule_list;
     vmodule_list = head;
   }
   inited_vmodule = true;
 }
 
-// This can be called very early, so we use SpinLock and RAW_VLOG here.
+// Sets the VLOG level for a given module pattern.
 int SetVLOGLevel(const char* module_pattern, int log_level) {
   int result = FLAGS_v;
-  size_t const pattern_len = strlen(module_pattern);
+  const size_t pattern_len = strlen(module_pattern);
   bool found = false;
   {
-    std::lock_guard<std::mutex> l(
-        vmodule_mutex);  // protect whole read-modify-write
-    for (const VModuleInfo* info = vmodule_list; info != nullptr;
-         info = info->next) {
+    std::lock_guard<std::mutex> l(vmodule_mutex);
+    for (const VModuleInfo* info = vmodule_list; info != nullptr; info = info->next) {
       if (info->module_pattern == module_pattern) {
         if (!found) {
           result = info->vlog_level;
           found = true;
         }
         info->vlog_level = log_level;
-      } else if (!found && SafeFNMatch_(info->module_pattern.c_str(),
-                                        info->module_pattern.size(),
-                                        module_pattern, pattern_len)) {
+      } else if (!found &&
+                 SafeFNMatch_(info->module_pattern.c_str(),
+                              info->module_pattern.size(),
+                              module_pattern, pattern_len)) {
         result = info->vlog_level;
         found = true;
       }
@@ -176,15 +172,12 @@ int SetVLOGLevel(const char* module_pattern, int log_level) {
       info->next = vmodule_list;
       vmodule_list = info;
 
+      // Update any cached site flags that match this module.
       SiteFlag** item_ptr = &cached_site_list;
       SiteFlag* item = cached_site_list;
-
-      // We traverse the list fully because the pattern can match several items
-      // from the list.
       while (item) {
         if (SafeFNMatch_(module_pattern, pattern_len, item->base_name,
                          item->base_len)) {
-          // Redirect the cached value to its module override.
           item->level = &info->vlog_level;
           *item_ptr = item->next;  // Remove the item from the list.
         } else {
@@ -198,8 +191,7 @@ int SetVLOGLevel(const char* module_pattern, int log_level) {
   return result;
 }
 
-// NOTE: Individual VLOG statements cache the integer log level pointers.
-// NOTE: This function must not allocate memory or require any locks.
+// Initializes the VLOG site flag and returns whether logging should occur.
 bool InitVLOG3__(SiteFlag* site_flag, int32* level_default, const char* fname,
                  int32 verbose_level) {
   std::lock_guard<std::mutex> l(vmodule_mutex);
@@ -208,59 +200,40 @@ bool InitVLOG3__(SiteFlag* site_flag, int32* level_default, const char* fname,
     VLOG2Initializer();
   }
 
-  // protect the errno global in case someone writes:
-  // VLOG(..) << "The last error was " << strerror(errno)
+  // Save errno in case any recoverable error occurs.
   int old_errno = errno;
-
-  // site_default normally points to FLAGS_v
   int32* site_flag_value = level_default;
 
-  // Get basename for file
+  // Get the base file name (strip directory path).
   const char* base = strrchr(fname, '/');
-
 #ifdef _WIN32
   if (!base) {
     base = strrchr(fname, '\\');
   }
 #endif
-
   base = base ? (base + 1) : fname;
   const char* base_end = strchr(base, '.');
-  size_t base_length =
-      base_end ? static_cast<size_t>(base_end - base) : strlen(base);
+  size_t base_length = base_end ? static_cast<size_t>(base_end - base) : strlen(base);
 
-  // Trim out trailing "-inl" if any
-  if (base_length >= 4 && (memcmp(base + base_length - 4, "-inl", 4) == 0)) {
+  // Trim any trailing "-inl" if present.
+  if (base_length >= 4 && memcmp(base + base_length - 4, "-inl", 4) == 0) {
     base_length -= 4;
   }
 
-  // TODO: Trim out _unittest suffix?  Perhaps it is better to have
-  // the extra control and just leave it there.
-
-  // find target in vector of modules, replace site_flag_value with
-  // a module-specific verbose level, if any.
-  for (const VModuleInfo* info = vmodule_list; info != nullptr;
-       info = info->next) {
+  // Search for a matching module override.
+  for (const VModuleInfo* info = vmodule_list; info != nullptr; info = info->next) {
     if (SafeFNMatch_(info->module_pattern.c_str(), info->module_pattern.size(),
                      base, base_length)) {
       site_flag_value = &info->vlog_level;
-      // value at info->vlog_level is now what controls
-      // the VLOG at the caller site forever
       break;
     }
   }
 
-  // Cache the vlog value pointer if --vmodule flag has been parsed.
+  // Cache the level pointer in the site flag.
   ANNOTATE_BENIGN_RACE(site_flag,
-                       "*site_flag may be written by several threads,"
-                       " but the value will be the same");
+      "*site_flag may be written by several threads, but the value will be the same");
   if (read_vmodule_flag) {
     site_flag->level = site_flag_value;
-    // If VLOG flag has been cached to the default site pointer,
-    // we want to add to the cached list in order to invalidate in case
-    // SetVModule is called afterwards with new modules.
-    // The performance penalty here is neglible, because InitVLOG3__ is called
-    // once per site.
     if (site_flag_value == level_default && !site_flag->base_name) {
       site_flag->base_name = base;
       site_flag->base_len = base_length;
@@ -269,8 +242,7 @@ bool InitVLOG3__(SiteFlag* site_flag, int32* level_default, const char* fname,
     }
   }
 
-  // restore the errno in case something recoverable went wrong during
-  // the initialization of the VLOG mechanism (see above note "protect the..")
+  // Restore errno and return whether logging should proceed.
   errno = old_errno;
   return *site_flag_value >= verbose_level;
 }