5 files changed, 205 insertions, 3 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 7c1d3d1dc..489d2bb7f 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -11,6 +11,7 @@ set(SRCS
             hash.cpp
             key_map.cpp
             log_manager.cpp
+            logging/filter.cpp
             logging/text_formatter.cpp
             logging/backend.cpp
             math_util.cpp
@@ -49,6 +50,7 @@ set(HEADERS
             log.h
             log_manager.h
             logging/text_formatter.h
+            logging/filter.h
             logging/log.h
             logging/backend.h
             math_util.h
diff --git a/src/common/logging/filter.cpp b/src/common/logging/filter.cpp
new file mode 100644
index 000000000..0cf9b05e7
--- /dev/null
+++ b/src/common/logging/filter.cpp
@@ -0,0 +1,132 @@
+// Copyright 2014 Citra Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <algorithm>
+
+#include "common/logging/filter.h"
+#include "common/logging/backend.h"
+#include "common/string_util.h"
+
+namespace Log {
+
+Filter::Filter(Level default_level) {
+    ResetAll(default_level);
+}
+
+void Filter::ResetAll(Level level) {
+    class_levels.fill(level);
+}
+
+void Filter::SetClassLevel(Class log_class, Level level) {
+    class_levels[static_cast<size_t>(log_class)] = level;
+}
+
+void Filter::SetSubclassesLevel(const ClassInfo& log_class, Level level) {
+    const size_t log_class_i = static_cast<size_t>(log_class.log_class);
+
+    const size_t begin = log_class_i + 1;
+    const size_t end = begin + log_class.num_children;
+    for (size_t i = begin; begin < end; ++i) {
+        class_levels[i] = level;
+    }
+}
+
+void Filter::ParseFilterString(const std::string& filter_str) {
+    auto clause_begin = filter_str.cbegin();
+    while (clause_begin != filter_str.cend()) {
+        auto clause_end = std::find(clause_begin, filter_str.cend(), ' ');
+
+        // If clause isn't empty
+        if (clause_end != clause_begin) {
+            ParseFilterRule(clause_begin, clause_end);
+        }
+
+        if (clause_end != filter_str.cend()) {
+            // Skip over the whitespace
+            ++clause_end;
+        }
+        clause_begin = clause_end;
+    }
+}
+
+template <typename It>
+static Level GetLevelByName(const It begin, const It end) {
+    for (u8 i = 0; i < static_cast<u8>(Level::Count); ++i) {
+        const char* level_name = Logger::GetLevelName(static_cast<Level>(i));
+        if (Common::ComparePartialString(begin, end, level_name)) {
+            return static_cast<Level>(i);
+        }
+    }
+    return Level::Count;
+}
+
+template <typename It>
+static Class GetClassByName(const It begin, const It end) {
+    for (ClassType i = 0; i < static_cast<ClassType>(Class::Count); ++i) {
+        const char* level_name = Logger::GetLogClassName(static_cast<Class>(i));
+        if (Common::ComparePartialString(begin, end, level_name)) {
+            return static_cast<Class>(i);
+        }
+    }
+    return Class::Count;
+}
+
+template <typename InputIt, typename T>
+static InputIt find_last(InputIt begin, const InputIt end, const T& value) {
+    auto match = end;
+    while (begin != end) {
+        auto new_match = std::find(begin, end, value);
+        if (new_match != end) {
+            match = new_match;
+            ++new_match;
+        }
+        begin = new_match;
+    }
+    return match;
+}
+
+bool Filter::ParseFilterRule(const std::string::const_iterator begin,
+        const std::string::const_iterator end) {
+    auto level_separator = std::find(begin, end, ':');
+    if (level_separator == end) {
+        LOG_ERROR(Log, "Invalid log filter. Must specify a log level after `:`: %s",
+                std::string(begin, end).c_str());
+        return false;
+    }
+
+    const Level level = GetLevelByName(level_separator + 1, end);
+    if (level == Level::Count) {
+        LOG_ERROR(Log, "Unknown log level in filter: %s", std::string(begin, end).c_str());
+        return false;
+    }
+
+    if (Common::ComparePartialString(begin, level_separator, "*")) {
+        ResetAll(level);
+        return true;
+    }
+
+    auto class_name_end = find_last(begin, level_separator, '.');
+    if (class_name_end != level_separator &&
+            !Common::ComparePartialString(class_name_end + 1, level_separator, "*")) {
+        class_name_end = level_separator;
+    }
+
+    const Class log_class = GetClassByName(begin, class_name_end);
+    if (log_class == Class::Count) {
+        LOG_ERROR(Log, "Unknown log class in filter: %s", std::string(begin, end).c_str());
+        return false;
+    }
+
+    if (class_name_end == level_separator) {
+        SetClassLevel(log_class, level);
+    }
+    SetSubclassesLevel(log_class, level);
+    return true;
+}
+
+bool Filter::CheckMessage(Class log_class, Level level) const {
+    return static_cast<u8>(level) >= static_cast<u8>(class_levels[static_cast<size_t>(log_class)]);
+}
+
+}
diff --git a/src/common/logging/filter.h b/src/common/logging/filter.h
new file mode 100644
index 000000000..32b14b159
--- /dev/null
+++ b/src/common/logging/filter.h
@@ -0,0 +1,63 @@
+// Copyright 2014 Citra Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <array>
+#include <string>
+
+#include "common/logging/log.h"
+
+namespace Log {
+
+struct ClassInfo;
+
+/**
+ * Implements a log message filter which allows different log classes to have different minimum
+ * severity levels. The filter can be changed at runtime and can be parsed from a string to allow
+ * editing via the interface or loading from a configuration file.
+ */
+class Filter {
+public:
+    /// Initializes the filter with all classes having `default_level` as the minimum level.
+    Filter(Level default_level);
+
+    /// Resets the filter so that all classes have `level` as the minimum displayed level.
+    void ResetAll(Level level);
+    /// Sets the minimum level of `log_class` (and not of its subclasses) to `level`.
+    void SetClassLevel(Class log_class, Level level);
+    /**
+     * Sets the minimum level of all of `log_class` subclasses to `level`. The level of `log_class`
+     * itself is not changed.
+     */
+    void SetSubclassesLevel(const ClassInfo& log_class, Level level);
+
+    /**
+     * Parses a filter string and applies it to this filter.
+     *
+     * A filter string consists of a space-separated list of filter rules, each of the format
+     * `<class>:<level>`. `<class>` is a log class name, with subclasses separated using periods.
+     * A rule for a given class also affects all of its subclasses. `*` wildcards are allowed and
+     * can be used to apply a rule to all classes or to all subclasses of a class without affecting
+     * the parent class. `<level>` a severity level name which will be set as the minimum logging
+     * level of the matched classes. Rules are applied left to right, with each rule overriding
+     * previous ones in the sequence.
+     *
+     * A few examples of filter rules:
+     *  - `*:Info` -- Resets the level of all classes to Info.
+     *  - `Service:Info` -- Sets the level of Service and all subclasses (Service.FS, Service.APT,
+     *                       etc.) to Info.
+     *  - `Service.*:Debug` -- Sets the level of all Service subclasses to Debug, while leaving the
+     *                         level of Service unchanged.
+     *  - `Service.FS:Trace` -- Sets the level of the Service.FS class to Trace.
+     */
+    void ParseFilterString(const std::string& filter_str);
+    bool ParseFilterRule(const std::string::const_iterator start, const std::string::const_iterator end);
+
+    /// Matches class/level combination against the filter, returning true if it passed.
+    bool CheckMessage(Class log_class, Level level) const;
+
+private:
+    std::array<Level, (size_t)Class::Count> class_levels;
+};
+
+}
diff --git a/src/common/logging/text_formatter.cpp b/src/common/logging/text_formatter.cpp
index 88deb150e..3fe435346 100644
--- a/src/common/logging/text_formatter.cpp
+++ b/src/common/logging/text_formatter.cpp
@@ -11,6 +11,7 @@
 #endif
 
 #include "common/logging/backend.h"
+#include "common/logging/filter.h"
 #include "common/logging/log.h"
 #include "common/logging/text_formatter.h"
 
@@ -105,7 +106,7 @@ void PrintMessage(const Entry& entry) {
     fputc('\n', stderr);
 }
 
-void TextLoggingLoop(std::shared_ptr<Logger> logger) {
+void TextLoggingLoop(std::shared_ptr<Logger> logger, const Filter* filter) {
     std::array<Entry, 256> entry_buffer;
 
     while (true) {
@@ -114,7 +115,10 @@ void TextLoggingLoop(std::shared_ptr<Logger> logger) {
             break;
         }
         for (size_t i = 0; i < num_entries; ++i) {
-            PrintMessage(entry_buffer[i]);
+            const Entry& entry = entry_buffer[i];
+            if (filter->CheckMessage(entry.log_class, entry.log_level)) {
+                PrintMessage(entry);
+            }
         }
     }
 }
diff --git a/src/common/logging/text_formatter.h b/src/common/logging/text_formatter.h
index 04164600f..d7e298e28 100644
--- a/src/common/logging/text_formatter.h
+++ b/src/common/logging/text_formatter.h
@@ -11,6 +11,7 @@ namespace Log {
 
 class Logger;
 struct Entry;
+class Filter;
 
 /**
  * Attempts to trim an arbitrary prefix from `path`, leaving only the part starting at `root`. It's
@@ -33,6 +34,6 @@ void PrintMessage(const Entry& entry);
  * Logging loop that repeatedly reads messages from the provided logger and prints them to the
  * console. It is the baseline barebones log outputter.
  */
-void TextLoggingLoop(std::shared_ptr<Logger> logger);
+void TextLoggingLoop(std::shared_ptr<Logger> logger, const Filter* filter);
 
 }