3 files changed, 30 insertions, 27 deletions

diff --git a/apps/SoilMoistureIo.cpp b/apps/SoilMoistureIo.cpp
index c7f3504..a2d50e4 100644
--- a/apps/SoilMoistureIo.cpp
+++ b/apps/SoilMoistureIo.cpp
@@ -11,7 +11,7 @@ namespace soil_moisture {
 using namespace std;
 using json = nlohmann::json;
 
-void VectorSampleOutputStream::write(SampleRecord sample) {
+void VectorSampleOutputStream::write(SampleRecord const &sample) {
     samples.emplace_back(sample);
 }
 
@@ -19,7 +19,7 @@ CsvSampleOutputStream::CsvSampleOutputStream(shared_ptr<ostream> stream, KeyDict
         : stream(move(stream)), headerWritten(false), dict(dict) {
 }
 
-void CsvSampleOutputStream::write(SampleRecord sample) {
+void CsvSampleOutputStream::write(SampleRecord const &sample) {
     // Skip empty records
     if (sample.empty()) {
         return;
@@ -28,8 +28,8 @@ void CsvSampleOutputStream::write(SampleRecord sample) {
     // Build the dict with the keys from the first sample.
     if (dict.empty()) {
         SampleKeyIndex index = 0;
-        auto ptr = sample.begin();
-        while (ptr != sample.end()) {
+        auto ptr = sample.cbegin();
+        while (ptr != sample.cend()) {
             auto o = *ptr;
 
             if (o) {
@@ -88,7 +88,7 @@ JsonSampleOutputStream::JsonSampleOutputStream(shared_ptr<ostream> stream, KeyDi
         dict(dict), stream(move(stream)) {
 }
 
-void JsonSampleOutputStream::write(SampleRecord sample) {
+void JsonSampleOutputStream::write(SampleRecord const &sample) {
     // Skip empty records
     if (sample.empty()) {
         return;
@@ -125,7 +125,7 @@ KeyValueSampleOutputStream::KeyValueSampleOutputStream(shared_ptr<ostream> strea
         dict(dict), stream(move(stream)) {
 }
 
-void KeyValueSampleOutputStream::write(SampleRecord sample) {
+void KeyValueSampleOutputStream::write(SampleRecord const &sample) {
     // Skip empty records
     if (sample.empty()) {
         return;
@@ -146,7 +146,7 @@ void KeyValueSampleOutputStream::write(SampleRecord sample) {
                 } else {
                     s << ", ";
                 }
-                s << key->name << "=" << value;
+                s << key->name << "=" << value.get();
             }
         }
     } else {
@@ -173,7 +173,7 @@ SqlSampleOutputStream::SqlSampleOutputStream(shared_ptr<ostream> stream, KeyDict
         dict(dict), stream(move(stream)), table_name(table_name) {
 }
 
-void SqlSampleOutputStream::write(SampleRecord values) {
+void SqlSampleOutputStream::write(SampleRecord const &values) {
     throw sample_exception("deimplemented");
 
 //    string fs, vs;
@@ -305,11 +305,11 @@ string to_string(const sample_format_type &arg) {
         throw std::runtime_error("Unknown format value: " + to_string(arg));
 }
 
-std::ostream& operator<<(std::ostream& os, sample_format_type const& type){
+std::ostream& operator<<(std::ostream& os, sample_format_type const& type) {
     return os << to_string(type);
 }
 
-std::istream& operator>>(std::istream& is, sample_format_type& type){
+std::istream& operator>>(std::istream& is, sample_format_type& type) {
     string s;
     is >> s;
 
diff --git a/apps/SoilMoistureIo.h b/apps/SoilMoistureIo.h
index 3e78f46..fac518c 100644
--- a/apps/SoilMoistureIo.h
+++ b/apps/SoilMoistureIo.h
@@ -169,21 +169,21 @@ public:
     }
 
     inline
-    vec::const_iterator begin() {
-        return values.begin();
+    vec::const_iterator cbegin() const {
+        return values.cbegin();
     }
 
     inline
-    vec::const_iterator end() {
-        return values.end();
+    vec::const_iterator cend() const {
+        return values.cend();
     }
 
     inline
-    bool empty() {
+    bool empty() const {
         return values.empty();
     }
 
-    o<string> at(const SampleKey *key) const {
+    const o<string> at(const SampleKey *key) const {
         SampleKeyIndex index = key->index;
         if (index >= values.size()) {
             return o<string>();
@@ -195,11 +195,11 @@ public:
     void set(const SampleKey *key, const std::string &value) {
         values.resize(max(values.size(), key->index + 1));
 
-        values.at(key->index) = o<string>(value);
+        values.at(key->index).reset(value);
     }
 
     template<class A>
-    const o<A> lexical_at(const SampleKey *key) {
+    const o<A> lexical_at(const SampleKey *key) const {
         auto value = at(key);
 
         if (!value) {
@@ -233,13 +233,13 @@ private:
 
 class SampleOutputStream {
 public:
-    virtual void write(SampleRecord sample) = 0;
+    virtual void write(SampleRecord const &sample) = 0;
 };
 
 class VectorSampleOutputStream : public SampleOutputStream {
 
 public:
-    virtual void write(SampleRecord sample) override;
+    virtual void write(SampleRecord const &sample) override;
 
 public:
     vector<SampleRecord> samples;
@@ -249,7 +249,7 @@ class CsvSampleOutputStream : public SampleOutputStream {
 public:
     CsvSampleOutputStream(shared_ptr<ostream> stream, KeyDictionary &dict);
 
-    void write(SampleRecord sample);
+    void write(SampleRecord const &sample);
 
     const KeyDictionary &getDict() {
         return dict;
@@ -267,7 +267,7 @@ class JsonSampleOutputStream : public SampleOutputStream {
 public:
     JsonSampleOutputStream(shared_ptr<ostream> stream, KeyDictionary &dict);
 
-    void write(SampleRecord sample) override;
+    void write(SampleRecord const &sample) override;
 
 private:
     KeyDictionary &dict;
@@ -278,7 +278,7 @@ class KeyValueSampleOutputStream : public SampleOutputStream {
 public:
     KeyValueSampleOutputStream(shared_ptr<ostream> stream, KeyDictionary &dict);
 
-    void write(SampleRecord sample) override;
+    void write(SampleRecord const &sample) override;
 
 private:
     KeyDictionary &dict;
@@ -289,7 +289,7 @@ class SqlSampleOutputStream : public SampleOutputStream {
 public:
     SqlSampleOutputStream(shared_ptr<ostream> stream, KeyDictionary &dict, string table_name);
 
-    void write(SampleRecord sample) override;
+    void write(SampleRecord const &sample) override;
 
 private:
     KeyDictionary &dict;
diff --git a/apps/sample-timestamp.cpp b/apps/sample-timestamp.cpp
index 4855506..df4a89e 100644
--- a/apps/sample-timestamp.cpp
+++ b/apps/sample-timestamp.cpp
@@ -18,7 +18,7 @@ public:
             timestamp_key(dict.indexOf(timestamp_name)), now_key(dict.indexOf(now_name)), start_time_(start_time), output_(output) {
     }
 
-    virtual void write(SampleRecord sample) override {
+    virtual void write(SampleRecord const &sample) override {
         o<long> relative_time_o = sample.lexical_at<long>(now_key);
 
         if (!relative_time_o) {
@@ -28,9 +28,12 @@ public:
         long relative_time = relative_time_o.get();
 
         string new_value = std::to_string(start_time_ + relative_time);
-        sample.set(timestamp_key, new_value);
 
-        output_->write(sample);
+        SampleRecord updatedSample(sample);
+
+        updatedSample.set(timestamp_key, new_value);
+
+        output_->write(updatedSample);
     };
 
 private: