Diff: StringFifo.cpp

Revision:

0:093546398fcd

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/StringFifo.cpp	Sun Jun 11 04:06:39 2017 +0000
@@ -0,0 +1,78 @@
+/*
+ * StringFifo: A simple FIFO class for passing strings between threads.
+ */
+#include "StringFifo.h"
+
+StringFifo::StringFifo(int size)
+{
+    sP = (char *) malloc(size);
+    if (sP != NULL) {
+        len = size;
+    } else {
+        len = 0;
+    }
+    pushI = 0;
+    popI = 0;
+}
+
+StringFifo::~StringFifo()
+{
+    free(sP);
+    len = 0;
+}
+
+void StringFifo::PushString(char* s)
+{
+    int sLen;
+    int i;
+
+    push_mutex.lock();
+
+    // Compute the required room
+    sLen = 0;
+    while (*(s+sLen) != 0) sLen++;
+    sLen += 1;  // Add in null character
+    
+    // Wait until there is room
+    while (Remaining() < sLen) {
+        Thread::yield();
+    }
+    
+    // Push the string
+    i = pushI;
+    while ((*(sP + i) = *s++) != 0) {
+        i = (i + 1) % len;
+    }
+    
+    // Atomically update pushI
+    pushI = (i + 1) % len;  // Always point to next location to fill 
+
+    push_mutex.unlock();
+}
+
+void StringFifo::PopString(char* s)
+{
+    int i;
+
+    // Wait until there is a string to pop
+    while (IsEmpty()) {
+        Thread::yield();
+    }
+    
+    // Get the string
+    i = popI;
+    while ((*s++ = *(sP + i)) != 0) {
+        i = (i + 1) % len;
+    }
+    
+    // Update popI
+    popI = (i + 1) % len;  // Always point to start of next string
+}
+
+int StringFifo::Remaining()
+{
+    if (pushI >= popI)
+        return (len - pushI + popI);
+    else
+        return (popI - pushI);
+}