[trac4090] Add support for TokenSubstring

Add support and testing for TokenSubstring.  This token
takes three paramaters (string, start and length) and produces
a new string based on the original string.  It allows negative
values for start and length causing it to count from the end
of the string for start and to get characters before the start
point for length.

src/lib/eval/tests/token_unittest.cc

@@ -60,6 +60,40 @@ public:
     OptionPtr option_str4_; ///< A string option for DHCPv4
     OptionPtr option_str6_; ///< A string option for DHCPv6
 
+
+    /// @brief Verify that the substring eval works properly
+    ///
+    /// This function takes the parameters and sets up the value
+    /// stack then executes the eval and checks the results.
+    ///
+    /// @param test_string The string to operate on
+    /// @param test_start The postion to start when getting a substring
+    /// @param test_length The length of the substring to get
+    /// @param result_string The expected result of the eval
+    void verifySubstringEval(const std::string& test_string,
+                             const std::string& test_start,
+                             const std::string& test_length,
+                             const std::string& result_string) {
+
+        // create the token
+        ASSERT_NO_THROW(t_.reset(new TokenSubstring()));
+
+        // push values on stack
+        values_.push(test_string);
+        values_.push(test_start);
+        values_.push(test_length);
+
+        // evaluate the token
+        EXPECT_NO_THROW(t_->evaluate(*pkt4_, values_));
+
+        // verify results
+        ASSERT_EQ(1, values_.size());
+        EXPECT_EQ(result_string, values_.top());
+
+        // remove result
+        values_.pop();
+    }
+
     /// @todo: Add more option types here
 };
 
@@ -197,3 +231,176 @@ TEST_F(TokenTest, optionEqualTrue) {
 }
 
 };
+
+// This test checks if an a token representing a substring request
+// throws an excpetion if there aren't enough values on the stack.
+// The stack from the top is: length, start, string.
+// The actual packet is not used.
+TEST_F(TokenTest, substringNotEnoughValues) {
+    ASSERT_NO_THROW(t_.reset(new TokenSubstring()));
+
+    // Subsring requires three values on the stack, try
+    // with 0, 1 and 2 all should thorw an exception
+    EXPECT_THROW(t_->evaluate(*pkt4_, values_), EvalBadStack);
+
+    values_.push("");
+    EXPECT_THROW(t_->evaluate(*pkt4_, values_), EvalBadStack);
+
+    values_.push("0");
+    EXPECT_THROW(t_->evaluate(*pkt4_, values_), EvalBadStack);
+
+    // Three should work
+    values_.push("0");
+    EXPECT_NO_THROW(t_->evaluate(*pkt4_, values_));
+
+    // As we had an empty string to start with we should have an empty
+    // one after the evaluate
+    ASSERT_EQ(1, values_.size());
+    EXPECT_EQ("", values_.top());
+}
+
+// Test getting the whole string in different ways
+TEST_F(TokenTest, substringWholeString) {
+    // Get the whole string
+    verifySubstringEval("foobar", "0", "6", "foobar");
+
+    // Get the whole string with "all"
+    verifySubstringEval("foobar", "0", "all", "foobar");
+
+    // Get the whole string with an extra long number
+    verifySubstringEval("foobar", "0", "123456", "foobar");
+
+    // Get the whole string counting from the back
+    verifySubstringEval("foobar", "-6", "all", "foobar");
+}
+
+// Test getting a suffix, in this case the last 3 characters
+TEST_F(TokenTest, substringTrailer) {
+    verifySubstringEval("foobar", "3", "3", "bar");
+    verifySubstringEval("foobar", "3", "all", "bar");
+    verifySubstringEval("foobar", "-3", "all", "bar");
+    verifySubstringEval("foobar", "-3", "123", "bar");
+}
+
+// Test getting the middle of the string in different ways
+TEST_F(TokenTest, substringMiddle) {
+    verifySubstringEval("foobar", "1", "4", "ooba");
+    verifySubstringEval("foobar", "-5", "4", "ooba");
+    verifySubstringEval("foobar", "-1", "-4", "ooba");
+    verifySubstringEval("foobar", "5", "-4", "ooba");
+}
+
+// Test getting the last letter in different ways
+TEST_F(TokenTest, substringLastLetter) {
+    verifySubstringEval("foobar", "5", "all", "r");
+    verifySubstringEval("foobar", "5", "1", "r");
+    verifySubstringEval("foobar", "5", "5", "r");
+    verifySubstringEval("foobar", "-1", "all", "r");
+    verifySubstringEval("foobar", "-1", "1", "r");
+    verifySubstringEval("foobar", "-1", "5", "r");
+}
+
+// Test we get only what is available if we ask for a longer string
+TEST_F(TokenTest, substringLength) {
+    // Test off the front
+    verifySubstringEval("foobar", "0", "-4", "");
+    verifySubstringEval("foobar", "1", "-4", "f");
+    verifySubstringEval("foobar", "2", "-4", "fo");
+    verifySubstringEval("foobar", "3", "-4", "foo");
+
+    // and the back
+    verifySubstringEval("foobar", "3", "4", "bar");
+    verifySubstringEval("foobar", "4", "4", "ar");
+    verifySubstringEval("foobar", "5", "4", "r");
+    verifySubstringEval("foobar", "6", "4", "");
+}
+
+// Test that we get nothing if the starting postion is out of the string
+TEST_F(TokenTest, substringStartingPosition) {
+    // Off the front
+    verifySubstringEval("foobar", "-7", "1", "");
+    verifySubstringEval("foobar", "-7", "-11", "");
+    verifySubstringEval("foobar", "-7", "all", "");
+
+    // and the back
+    verifySubstringEval("foobar", "6", "1", "");
+    verifySubstringEval("foobar", "6", "-11", "");
+    verifySubstringEval("foobar", "6", "all", "");
+}
+
+// Check what happens if we use strings that aren't numbers for start or length
+// We should return the empty string
+TEST_F(TokenTest, substringBadParams) {
+    verifySubstringEval("foobar", "0ick", "all", "");
+    verifySubstringEval("foobar", "ick0", "all", "");
+    verifySubstringEval("foobar", "ick", "all", "");
+    verifySubstringEval("foobar", "0", "ick", "");
+    verifySubstringEval("foobar", "0", "0ick", "");
+    verifySubstringEval("foobar", "0", "ick0", "");
+    verifySubstringEval("foobar", "0", "allaboard", "");
+}
+
+// lastly check that we don't get anything if the string is empty
+TEST_F(TokenTest, substringStartingEmpty) {
+    verifySubstringEval("", "0", "all", "");
+    verifySubstringEval("foobar", "0", "0", "");
+}
+
+// Check if we can use the substring and equal tokens together
+// We put the result on the stack first then the substring values
+// then evaluate the substring which should leave the original
+// result on the bottom with the substring result on next.
+// Evaulating the equals should produce true for the first
+// and false for the second.
+// throws an excpetion if there aren't enough values on the stack.
+// The stack from the top is: length, start, string.
+// The actual packet is not used.
+TEST_F(TokenTest, substringEquals) {
+    TokenPtr tequal;
+
+    ASSERT_NO_THROW(t_.reset(new TokenSubstring()));
+    ASSERT_NO_THROW(tequal.reset(new TokenEqual()));
+
+    // The final expected value
+    values_.push("ooba");
+
+    // The substring values
+    // Subsring requires three values on the stack, try
+    // with 0, 1 and 2 all should thorw an exception
+    values_.push("foobar");
+    values_.push("1");
+    values_.push("4");
+    EXPECT_NO_THROW(t_->evaluate(*pkt4_, values_));
+
+    // we should have two values on the stack
+    ASSERT_EQ(2, values_.size());
+
+    // next the equals eval
+    EXPECT_NO_THROW(tequal->evaluate(*pkt4_, values_));
+    ASSERT_EQ(1, values_.size());
+    EXPECT_EQ("true", values_.top());
+
+    // get rid of the result
+    values_.pop();
+
+    // and try it again but with a bad final value
+    // The final expected value
+    values_.push("foob");
+
+    // The substring values
+    // Subsring requires three values on the stack, try
+    // with 0, 1 and 2 all should thorw an exception
+    values_.push("foobar");
+    values_.push("1");
+    values_.push("4");
+    EXPECT_NO_THROW(t_->evaluate(*pkt4_, values_));
+
+    // we should have two values on the stack
+    ASSERT_EQ(2, values_.size());
+
+    // next the equals eval
+    EXPECT_NO_THROW(tequal->evaluate(*pkt4_, values_));
+    ASSERT_EQ(1, values_.size());
+    EXPECT_EQ("false", values_.top());
+
+}