break out cassette FFWD to tone function and expose to user

doc/cassette.asciidoc

@@ -52,9 +52,15 @@ The tape is automatically positioned at the first header tone.
 
 +cassette rewind+
 
-This command rewinds the tape currently on the CASSETTE IN port.
-This command first positions the tape to its beginning,
-and then ``fast-forwards'' to the first header tone.
+This command rewinds the tape currently on the CASSETTE IN port. After rewinding
+the tape, you will typically need to fast-forward to the head tone using
+the +cassette tone+ command.
+
++cassette tone+
+
+If more than one program is stored in one WAVE file, then after loading the first
+program, you may need to fast-forward to the next header tone. This command will
+do just that.
 
 +cassette blank <file-path>+
 

doc/commands.asciidoc

@@ -170,6 +170,7 @@ The +cassette+ command performs various operations of the emulated cassette tape
 --------
 cassette load [ <file-path> ]
 cassette rewind
+cassette tone
 cassette blank <file-path>
 cassette save
 cassette eject { in | out }

src/cassettein.cpp

@@ -157,17 +157,26 @@ void CassetteIn::rewind() {
     this->playing = false;
     note_pos();
 
+    this->gui.setCassettePos(this->t/10,this->samp_siz);
+}
 
-
-
+void CassetteIn::tone() {
+    if (!isLoaded()) {
+        return;
+    }
+    note_pos();
 
     note("FAST FORWARD TO TONE");
 
+    this->playing = false;
+
     const unsigned int HEAD_SAMPLES = 17;
     std::int_fast8_t slope_was = 0;
-    uint i_was = 0;
-    uint c_head = 0;
-    for (std::uint_fast32_t i = 1; i < this->samp_siz; ++i) {
+    std::uint_fast32_t i_was = 0;
+    std::uint_fast32_t c_head = 0;
+
+    const std::uint_fast32_t start = this->t/10 > 0 ? this->t/10 : 1;
+    for (std::uint_fast32_t i = start; i < this->samp_siz; ++i) {
         std::int_fast8_t slope_is = slope(this->samp[i-1], this->samp[i]);
         if (slope_is) {
             if (slope_is != slope_was) {
@@ -244,6 +253,7 @@ bool CassetteIn::load(const std::string& filePath) {
     this->gui.setCassetteInFile(filePath);
 
     rewind();
+    tone();
 
 	return true;
 }

src/cassettein.h

@@ -42,6 +42,7 @@ public:
 
         bool load(const std::string& filePath);
         void rewind();
+        void tone();
         virtual bool eject();
 };
 

src/configep2.cpp

@@ -304,6 +304,10 @@ void Config::tryParseLine(const std::string& line, Memory& ram, Memory& rom, Slo
 		{
             cassetteIn.rewind();
 		}
+        else if (cas == "tone")
+        {
+            cassetteIn.tone();
+        }
         else if (cas == "blank")
 		{
 			std::string fcas;