Add fifo routine to be used for CW queueing

src/Makefile.am

@@ -10,7 +10,7 @@ RIGSRC = hamlibdatetime.h rig.c serial.c serial.h misc.c misc.h register.c regis
    	network.c network.h cm108.c cm108.h gpio.c gpio.h idx_builtin.h token.h \
    	par_nt.h microham.c microham.h amplifier.c amp_reg.c amp_conf.c \
    	amp_conf.h amp_settings.c extamp.c sleep.c sleep.h sprintflst.c \
-   	sprintflst.h cache.c cache.h snapshot_data.c snapshot_data.h multicast.c
+   	sprintflst.h cache.c cache.h snapshot_data.c snapshot_data.h multicast.c fifo.c
 
 if VERSIONDLL
 RIGSRC +=	\

src/fifo.c

@@ -0,0 +1,58 @@
+#include <hamlib/rig.h>
+#include <stdio.h>
+#include "fifo.h"
+
+
+void initFIFO(FIFO *fifo)
+{
+    fifo->head = 0;
+    fifo->tail = 0;
+}
+
+// returns RIG_OK if added
+// return -RIG error if overflow
+int push(FIFO *fifo, const char *msg)
+{
+    int len = strlen(msg);
+
+    for (int i = 0; i < len; ++i)
+    {
+        fifo->data[fifo->tail] = msg[i];
+        fifo->tail = (fifo->tail + 1) % FIFO_SIZE;
+
+        if (fifo->tail == fifo->head) { return -RIG_EDOM; }
+    }
+
+    return RIG_OK;
+}
+
+char pop(FIFO *fifo)
+{
+    if (fifo->tail == fifo->head) { return -1; }
+
+    char c = fifo->data[fifo->head];
+    fifo->head = (fifo->head + 1) % FIFO_SIZE;
+    return c;
+}
+
+#ifdef TEST
+int main()
+{
+    FIFO fifo;
+    initFIFO(&fifo);
+
+    const char *str = "Hello, World!\n";
+
+    // Pushing the string onto the FIFO
+    push(&fifo, str);
+
+    // Popping and printing one character at a time
+    int c;
+    while ((c = pop(&fifo)) != -1)
+    {
+        printf("%c", c);
+    }
+
+    return 0;
+}
+#endif

src/fifo.h

@@ -0,0 +1,12 @@
+#define FIFO_SIZE 1024
+
+typedef struct
+{
+    char data[FIFO_SIZE];
+    int head;
+    int tail;
+} FIFO;
+
+void initFIFO(FIFO *fifo);
+int push(FIFO *fifo, const char *msg);
+char pop(FIFO *fifo);