lib: Add 'prefs' API

This defines and reads configuration files that can be used to customize
UHD's behaviour. On Unix systems, they default to:

/etc/uhd/uhd.conf
$APPDATA/.uhd/uhd.conf

On Windows systems, it will look in:

%ProgramData%/uhd/uhd.conf
%AppData%/.uhd/uhd.conf

2 files changed, 108 insertions, 0 deletions

diff --git a/host/lib/utils/CMakeLists.txt b/host/lib/utils/CMakeLists.txt
index 62d1ba090..659c855a1 100644
--- a/host/lib/utils/CMakeLists.txt
+++ b/host/lib/utils/CMakeLists.txt
@@ -155,6 +155,12 @@ SET_SOURCE_FILES_PROPERTIES(
     "UHD_PKG_PATH=\"${UHD_PKG_PATH}\";UHD_LIB_DIR=\"${UHD_LIB_DIR}\""
 )
 
+SET_SOURCE_FILES_PROPERTIES(
+    ${CMAKE_CURRENT_SOURCE_DIR}/prefs.cpp
+    PROPERTIES COMPILE_DEFINITIONS
+    "UHD_SYS_CONF_FILE=\"${UHD_SYS_CONF_FILE}\";UHD_USER_CONF_FILE=\"${UHD_USER_CONF_FILE}\""
+)
+
 ########################################################################
 # Append sources
 ########################################################################
@@ -170,6 +176,7 @@ LIBUHD_APPEND_SOURCES(
     ${CMAKE_CURRENT_SOURCE_DIR}/paths.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/pathslib.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/platform.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/prefs.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/static.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/tasks.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/thread.cpp
diff --git a/host/lib/utils/prefs.cpp b/host/lib/utils/prefs.cpp
new file mode 100644
index 000000000..5e5fa40f5
--- /dev/null
+++ b/host/lib/utils/prefs.cpp
@@ -0,0 +1,101 @@
+//
+// Copyright 2017-2018 Ettus Research, a National Instruments Company
+//
+// SPDX-License-Identifier: GPL-3.0+
+//
+
+#include <uhd/utils/log.hpp>
+#include <uhd/utils/paths.hpp>
+#include <uhdlib/utils/prefs.hpp>
+#include <uhdlib/utils/paths.hpp>
+#include <boost/filesystem.hpp>
+#include <cstdlib>
+
+using namespace uhd;
+
+namespace {
+    constexpr char UHD_CONF_FILE_VAR[] = "UHD_CONFIG_FILE";
+
+    inline void _update_conf_file(
+            const std::string& path,
+            const std::string& config_type,
+            config_parser& conf_file
+    ) {
+        if (not path.empty()) {
+                UHD_LOG_TRACE("PREFS", "Trying to load " << path);
+            try {
+                conf_file.read_file(path);
+                UHD_LOG_DEBUG("PREFS",
+                        "Loaded " << config_type << " config file " << path);
+            } catch (...) {
+                // nop
+            }
+        }
+    }
+
+    void update_from_key(
+        const std::string& key, const std::string &value,
+        uhd::device_addr_t& user_args
+    ) {
+        if (value.empty()) {
+            return;
+        }
+
+        const std::string key_str = key + "=" + value;
+        for (const auto& key : uhd::prefs::get_uhd_config().options(key_str)) {
+            user_args[key] =
+                uhd::prefs::get_uhd_config().get<std::string>(key_str, key);
+        }
+    }
+}
+
+config_parser& uhd::prefs::get_uhd_config()
+{
+    static config_parser _conf_files{};
+    static bool init_done = false;
+    if (not init_done) {
+        UHD_LOG_TRACE("CONF", "Initializing config file object...");
+        const std::string sys_conf_file = path_expandvars(UHD_SYS_CONF_FILE);
+        _update_conf_file(sys_conf_file, "system", _conf_files);
+        const std::string user_conf_file =
+            (boost::filesystem::path(get_app_path())
+                / std::string(UHD_USER_CONF_FILE)).string();
+        _update_conf_file(user_conf_file, "user", _conf_files);
+        std::string env_conf_file;
+        try { // getenv into std::string can fail
+            if (std::getenv(UHD_CONF_FILE_VAR) != NULL) {
+                env_conf_file = std::string(std::getenv(UHD_CONF_FILE_VAR));
+            }
+            _update_conf_file(env_conf_file, "ENV", _conf_files);
+        } catch (const std::exception &) {
+            // nop
+        }
+        UHD_LOG_TRACE("PREFS", "Done initializing.");
+    }
+
+    return _conf_files;
+}
+
+
+device_addr_t uhd::prefs::get_usrp_args(
+    const uhd::device_addr_t &user_args
+) {
+    device_addr_t usrp_args;
+    const std::vector<std::string> keys_to_update_from = {
+        "type",
+        "product",
+        "serial"
+    };
+
+    for (const auto& key : keys_to_update_from) {
+        update_from_key(key, user_args.get(key, ""), usrp_args);
+    }
+
+    // Finally, copy over the original user args:
+    for (const auto &user_key : user_args.keys()) {
+        usrp_args[user_key] = user_args[user_key];
+    }
+
+    return usrp_args;
+}
+