apphandler: Add storage for Get/Set System Info Parameter
All but one standard System Info Parameter and most (all?) OEM
parameters are string type. Add a interface to connect string callbacks
to System Info Parameter selector codes. Also add a convenience call
that can connect a static string to a parameter selector code.
Change-Id: I5e35d0418b8ddf5b2575fac093acfc7d7ca2217c
Signed-off-by: Xo Wang <xow@google.com>
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/sys_info_param.hpp b/sys_info_param.hpp
new file mode 100644
index 0000000..6088626
--- /dev/null
+++ b/sys_info_param.hpp
@@ -0,0 +1,66 @@
+#pragma once
+
+#include <cstdint>
+#include <functional>
+#include <map>
+#include <string>
+#include <tuple>
+
+/**
+ * Key-value store for string-type system info parameters.
+ */
+class SysInfoParamStoreIntf
+{
+ public:
+ virtual ~SysInfoParamStoreIntf()
+ {
+ }
+
+ /**
+ * Returns true if parameter is found. If and only if s is non-null,
+ * invokes the parameter's callback and writes the value.
+ *
+ * @param[in] paramSelector - the key to lookup.
+ * @return tuple of bool and string, true if parameter is found and
+ * string set accordingly.
+ */
+ virtual std::tuple<bool, std::string>
+ lookup(uint8_t paramSelector) const = 0;
+
+ /**
+ * Update a parameter by its code with a string value.
+ *
+ * @param[in] paramSelector - the key to update.
+ * @param[in] s - the value to set.
+ */
+ virtual void update(uint8_t paramSelector, const std::string& s) = 0;
+
+ /**
+ * Update a parameter by its code with a callback that is called to retrieve
+ * its value whenever called. Callback must be idempotent, as it may be
+ * called multiple times by the host to retrieve the parameter by chunks.
+ *
+ * @param[in] paramSelector - the key to update.
+ * @param[in] callback - the callback to use for parameter retrieval.
+ */
+ virtual void update(uint8_t paramSelector,
+ const std::function<std::string()>& callback) = 0;
+
+ // TODO: Store "read-only" flag for each parameter.
+ // TODO: Function to erase a parameter?
+};
+
+/**
+ * Implement the system info parameters store as a map of callbacks.
+ */
+class SysInfoParamStore : public SysInfoParamStoreIntf
+{
+ public:
+ std::tuple<bool, std::string> lookup(uint8_t paramSelector) const override;
+ void update(uint8_t paramSelector, const std::string& s) override;
+ void update(uint8_t paramSelector,
+ const std::function<std::string()>& callback) override;
+
+ private:
+ std::map<uint8_t, std::function<std::string()>> params;
+};