Dir cleanup

src/paracomm.c

@@ -0,0 +1,138 @@
+#include "paracomm.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#define kMosiIdleByte 0x00
+#define kMosiStartByte 0x42
+#define kMisoIdleNibble 0x0
+#define kMisoStartNibble 0xa
+
+static uint8_t mosi_workbuf[2][256];
+static uint8_t mosi_workbuf_idx;
+static uint8_t mosi_workbuf_size;
+
+static uint8_t* mosi_sendbuf;
+static uint8_t mosi_size;
+static uint8_t mosi_sent;
+
+static uint8_t mosi_state;
+
+static uint8_t miso_recvbuf[256];
+static uint8_t miso_size;
+static uint8_t miso_received_nibbles;
+static uint8_t miso_state;
+
+static void swapbuffers() {
+    mosi_sendbuf = mosi_workbuf[mosi_workbuf_idx];
+    mosi_size = mosi_workbuf_size;
+
+    mosi_workbuf_size = 0;
+    mosi_workbuf_idx = (mosi_workbuf_idx + 1) % 2;
+}
+
+uint8_t paracomm_nextbyte() {
+    switch (mosi_state) {
+    case 0:
+        if (mosi_size == 0) {
+            swapbuffers();
+            if (mosi_size == 0) {
+                return kMosiIdleByte;
+            }
+        }
+        mosi_state = 1;
+        return kMosiStartByte;
+    case 1:
+        // assert(mosi_size > 0)
+        mosi_sent = 0;
+        mosi_state = 2;
+        return mosi_size;
+    case 2: {
+        uint8_t b = mosi_sendbuf[mosi_sent];
+        mosi_sent += 1;
+
+        if (mosi_sent == mosi_size) {
+            swapbuffers();
+            mosi_state = 0;
+        }
+
+        return b;
+    }
+    }
+
+    __builtin_unreachable();
+}
+
+void paracomm_feed(uint8_t n) {
+    switch (miso_state) {
+    case 0:
+        if (n == kMisoStartNibble) {
+            miso_state = 1;
+        } else if (n == kMisoIdleNibble) {
+        } else {
+            // error: spurious nibble
+        }
+        break;
+    case 1:
+        miso_size = n;
+        miso_state = 2;
+        break;
+    case 2:
+        miso_size += n << 4;
+        miso_received_nibbles = 0;
+        miso_state = 3;
+        break;
+    case 3: {
+        uint8_t idx = miso_received_nibbles / 2;
+        if (miso_received_nibbles % 2 == 0) {
+            miso_recvbuf[idx] = n;
+        } else {
+            miso_recvbuf[idx] += n << 4;
+        }
+        miso_received_nibbles += 1;
+
+        if (miso_received_nibbles == 2 * miso_size) {
+            miso_state = 0;
+        }
+    } break;
+    }
+}
+
+void paracomm_init() {
+    mosi_size = 0;
+    mosi_workbuf_idx = 0;
+    mosi_workbuf_size = 0;
+    mosi_state = 0;
+
+    miso_state = 0;
+}
+
+int paracomm_send(uint8_t b) {
+    if (mosi_workbuf_size == 256) {
+        return -1;
+    }
+
+    uint8_t* buff = mosi_workbuf[mosi_workbuf_idx];
+    buff[mosi_workbuf_size] = b;
+    mosi_workbuf_size += 1;
+
+    return 0;
+}
+
+uint8_t paracomm_recv(uint8_t* buf, uint8_t size) {
+    if (miso_state != 0) {
+        return 0;
+    }
+    if (size > miso_size) {
+        size = miso_size;
+    }
+    memcpy(buf, miso_recvbuf, size);
+    memcpy(miso_recvbuf, miso_recvbuf+size, miso_size - size);
+    miso_size -= size;
+
+    return size;
+}
+
+uint8_t paracomm_busy() {
+    return mosi_state != 0 || miso_state != 0;
+}