[result] fix Result.map() issue with copying the value when the result was in error

release/loggen.py

@@ -151,6 +151,12 @@ FILES = [
 ]
 
 while True:
-    sys.stdout.write(FILES[1][1].next())
-    sys.stdout.flush()
-    time.sleep(random.uniform(1.0, 2.0))
+    for fname, gen in FILES:
+        for i in range(random.randrange(0, 4)):
+            with open(fname, "a+") as fp:
+                fp.write(gen.next())
+                if random.uniform(0.0, 1.0) < 0.010:
+                    fp.truncate(0)
+            time.sleep(random.uniform(0.00, 0.01))
+            if random.uniform(0.0, 1.0) < 0.001:
+                os.remove(fname)

src/base/result.h

@@ -772,10 +772,10 @@ struct Result {
 
     template<typename Func>
     auto map(Func func) const {
-        auto value = this->storage().template get<T>();
-        using return_type = decltype(func(value));
+        using return_type = decltype(func(T{}));
 
         if (this->isOk()) {
+            auto value = this->storage().template get<T>();
             auto res = func(value);
             return Result<return_type, E>(types::Ok<return_type>(std::move(res)));
         }

src/line_buffer.cc

@@ -774,7 +774,9 @@ Result<shared_buffer_ref, std::string> line_buffer::read_range(const file_range
         return Err(string("out-of-bounds"));
     }
 
-    this->fill_range(fr.fr_offset, fr.fr_size);
+    if (!this->fill_range(fr.fr_offset, fr.fr_size)) {
+        return Err(string("unable to read file"));
+    }
     line_start = this->get_range(fr.fr_offset, avail);
 
     if (fr.fr_size > avail) {

src/shared_buffer.cc

@@ -139,3 +139,20 @@ void shared_buffer_ref::disown()
     this->sb_data = nullptr;
     this->sb_length = 0;
 }
+
+void shared_buffer_ref::copy_ref(const shared_buffer_ref &other)
+{
+    if (other.sb_data == nullptr) {
+        this->sb_owner = nullptr;
+        this->sb_data = nullptr;
+        this->sb_length = 0;
+    }
+    else if (other.sb_owner != nullptr) {
+        this->share(*other.sb_owner, other.sb_data, other.sb_length);
+    } else {
+        this->sb_owner = nullptr;
+        this->sb_data = (char *)malloc(other.sb_length);
+        memcpy(this->sb_data, other.sb_data, other.sb_length);
+        this->sb_length = other.sb_length;
+    }
+}

src/shared_buffer.hh

@@ -116,21 +116,7 @@ public:
     void disown();
 
 private:
-    void copy_ref(const shared_buffer_ref &other) {
-        if (other.sb_data == nullptr) {
-            this->sb_owner = nullptr;
-            this->sb_data = nullptr;
-            this->sb_length = 0;
-        }
-        else if (other.sb_owner != nullptr) {
-            this->share(*other.sb_owner, other.sb_data, other.sb_length);
-        } else {
-            this->sb_owner = nullptr;
-            this->sb_data = (char *)malloc(other.sb_length);
-            memcpy(this->sb_data, other.sb_data, other.sb_length);
-            this->sb_length = other.sb_length;
-        }
-    }
+    void copy_ref(const shared_buffer_ref &other);
 
     auto_mem<char *> sb_backtrace;
     shared_buffer *sb_owner;