Opal: Convert entire Opal code into the Pure C

1 files changed, 165 insertions, 0 deletions

diff --git a/src/chips/opal/opal.h b/src/chips/opal/opal.h
new file mode 100644
index 0000000..0772d3e
--- /dev/null
+++ b/src/chips/opal/opal.h
@@ -0,0 +1,165 @@
+/*
+
+    The Opal OPL3 emulator.
+
+    Note: this is not a complete emulator, just enough for Reality Adlib Tracker tunes.
+
+    Missing features compared to a real OPL3:
+
+        - Timers/interrupts
+        - OPL3 enable bit (it defaults to always on)
+        - CSW mode
+        - Test register
+        - Percussion mode
+
+*/
+
+#ifndef OPAL_HHHH
+#define OPAL_HHHH
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define OPAL_TRUE 1
+#define OPAL_FALSE 0
+typedef int opal_bool;
+
+typedef struct OpalChannel_t OpalChannel;
+typedef struct OpalOperator_t OpalOperator;
+typedef struct Opal_t Opal;
+
+/* Various constants */
+typedef enum OpalEnum_t
+{
+    OpalOPL3SampleRate      = 49716,
+    OpalNumChannels         = 18,
+    OpalNumOperators        = 36,
+} OpalEnum;
+
+/* A single FM operator */
+struct OpalOperator_t
+{
+    Opal*           Master;             /* Master object */
+    OpalChannel*    Chan;               /* Owning channel */
+    uint32_t        Phase;              /* The current offset in the selected waveform */
+    uint16_t        Waveform;           /* The waveform id this operator is using */
+    uint16_t        FreqMultTimes2;     /* Frequency multiplier * 2 */
+    int             EnvelopeStage;      /* Which stage the envelope is at (see Env* enums above) */
+    int16_t         EnvelopeLevel;      /* 0 - $1FF, 0 being the loudest */
+    uint16_t        OutputLevel;        /* 0 - $FF */
+    uint16_t        AttackRate;
+    uint16_t        DecayRate;
+    uint16_t        SustainLevel;
+    uint16_t        ReleaseRate;
+    uint16_t        AttackShift;
+    uint16_t        AttackMask;
+    uint16_t        AttackAdd;
+    const uint16_t* AttackTab;
+    uint16_t        DecayShift;
+    uint16_t        DecayMask;
+    uint16_t        DecayAdd;
+    const uint16_t* DecayTab;
+    uint16_t        ReleaseShift;
+    uint16_t        ReleaseMask;
+    uint16_t        ReleaseAdd;
+    const uint16_t* ReleaseTab;
+    uint16_t        KeyScaleShift;
+    uint16_t        KeyScaleLevel;
+    int16_t         Out[2];
+    opal_bool       KeyOn;
+    opal_bool       KeyScaleRate;       /* Affects envelope rate scaling */
+    opal_bool       SustainMode;        /* Whether to sustain during the sustain phase, or release instead */
+    opal_bool       TremoloEnable;
+    opal_bool       VibratoEnable;
+};
+
+/* A single channel, which can contain two or more operators */
+struct OpalChannel_t
+{
+    OpalOperator*   Op[4];
+
+    Opal*           Master;             /* Master object */
+    uint16_t        Freq;               /* Frequency; actually it's a phase stepping value */
+    uint16_t        Octave;             /* Also known as "block" in Yamaha parlance */
+    uint32_t        PhaseStep;
+    uint16_t        KeyScaleNumber;
+    uint16_t        FeedbackShift;
+    uint16_t        ModulationType;
+    OpalChannel*    ChannelPair;
+    opal_bool       Enable;
+    opal_bool       LeftEnable, RightEnable;
+    uint16_t        LeftPan, RightPan;
+};
+
+
+/*==================================================================================================
+            Opal instance.
+ ==================================================================================================*/
+struct Opal_t
+{
+    int32_t             SampleRate;
+    int32_t             SampleAccum;
+    int16_t             LastOutput[2], CurrOutput[2];
+    OpalChannel         Chan[OpalNumChannels];
+    OpalOperator        Op[OpalNumOperators];
+    uint16_t            Clock;
+    uint16_t            TremoloClock;
+    uint16_t            TremoloLevel;
+    uint16_t            VibratoTick;
+    uint16_t            VibratoClock;
+    opal_bool           NoteSel;
+    opal_bool           TremoloDepth;
+    opal_bool           VibratoDepth;
+};
+
+
+/*==================================================================================================
+            Public API.
+ ==================================================================================================*/
+/*!
+ * \brief Initialize Opal with a given output sample rate
+ * \param self Pointer to the Opal instance
+ * \param sample_rate Desired output sample rate
+ */
+extern void Opal_Init(Opal *self, int sample_rate);
+
+/*!
+ * \brief Change the output sample rate of existing initialized instance
+ * \param self Pointer to the Opal instance
+ * \param sample_rate Desired output sample rate
+ */
+extern void Opal_SetSampleRate(Opal *self, int sample_rate);
+
+/*!
+ * \brief Send the register data to the Opal
+ * \param self Pointer to the Opal instance
+ * \param reg_num OPL3 Register address
+ * \param val Value to write
+ */
+extern void Opal_Port(Opal *self, uint16_t reg_num, uint8_t val);
+
+/*!
+ * \brief Panorama level per channel
+ * \param self Pointer to the Opal instance
+ * \param reg_num Channel number (multiplied by 256)
+ * \param pan Panorama level (0 - left, 64 - middle, 127 - right)
+ */
+extern void Opal_Pan(Opal *self, uint16_t reg_num, uint8_t pan);
+
+/*!
+ * \brief Generate one 16-bit PCM sample in system endian (there are two integers will be written)
+ * \param self Pointer to the Opal instance
+ * \param left Sample for the left chanel
+ * \param right Sample for the right channel
+ */
+extern void Opal_Sample(Opal *self, int16_t* left, int16_t* right);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* OPAL_HHHH */