Diff: pipe.h

Revision:

1:ef70a58a6c98

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pipe.h	Mon Apr 10 11:28:24 2017 +0100
@@ -0,0 +1,262 @@
+/* Copyright (c) 2017 Michael Ammann
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef PIPE_H
+#define PIPE_H
+
+/** pipe, this class implements a buffered pipe that can be savely 
+    written and read between two context. E.g. Written from a task 
+    and read from a interrupt.
+*/
+template <class T>
+class Pipe
+{
+public:
+    /* Constructor
+        \param n size of the pipe/buffer
+        \param b optional buffer that should be used. 
+                 if NULL the constructor will allocate a buffer of size n. 
+    */
+    Pipe(int n, T* b = NULL)
+    {
+        _a = b ? NULL : n ? new T[n] : NULL;
+        _r = 0;
+        _w = 0;
+        _b = b ? b : _a;
+        _s = n;
+    }    
+    /** Destructor 
+        frees a allocated buffer.
+    */
+    ~Pipe(void)
+    {
+        if (_a) 
+            delete [] _a;
+    }
+    
+    /* This function can be used during debugging to hexdump the 
+       content of a buffer to the stdout. 
+    */
+    void dump(void)
+    {
+        int o = _r;
+        printf("pipe: %d/%d ", size(), _s);
+        while (o != _w) {
+            T t = _b[o]; 
+            printf("%0*X", sizeof(T)*2, t);
+            o = _inc(o); 
+        }
+        printf("\n");
+    }
+    
+    // writing thread/context API
+    //------------------------------------------------------------- 
+    
+    /** Check if buffer is writeable (=not full)
+        \return true if writeable
+    */
+    bool writeable(void)
+    {
+        return free() > 0;
+    }
+    
+    /** Return the number of free elements in the buffer 
+        \return the number of free elements
+    */
+    int free(void)
+    {
+        int s = _r - _w;
+        if (s <= 0)
+            s += _s;
+        return s - 1;
+    }
+    
+    /* Add a single element to the buffer. (blocking)
+        \param c the element to add.
+        \return c
+    */
+    T putc(T c)
+    {
+        int i = _w;
+        int j = i;
+        i = _inc(i);
+        while (i == _r) // = !writeable() 
+            /* nothing / just wait */;
+        _b[j] = c;
+        _w = i; 
+        return c;
+    }
+    
+    /* Add a buffer of elements to the buffer.
+        \param p the elements to add
+        \param n the number elements to add from p
+        \param t set to true if blocking, false otherwise
+        \return number elements added 
+    */
+    int put(const T* p, int n, bool t = false)
+    {
+        int c = n;
+        while (c)
+        {
+            int f;
+            for (;;) // wait for space
+            {
+                f = free();
+                if (f > 0) break;     // data avail
+                if (!t) return n - c; // no more space and not blocking
+                /* nothing / just wait */;
+            }
+            // check free space
+            if (c < f) f = c;
+            int w = _w;
+            int m = _s - w; 
+            // check wrap
+            if (f > m) f = m;
+            memcpy(&_b[w], p, f);
+            _w = _inc(w, f);
+            c -= f;
+            p += f;
+        }
+        return n - c;
+    }
+    
+    // reading thread/context API
+    // --------------------------------------------------------
+    
+    /** Check if there are any emelemnt available (readble / not empty)
+        \return true if readable/not empty
+    */
+    bool readable(void)
+    {
+        return (_r != _w);
+    }
+    
+    /** Get the number of values available in the buffer
+        return the number of element available
+    */
+    int size(void)
+    {
+        int s = _w - _r;
+        if (s < 0)
+            s += _s;
+        return s;
+    }
+    
+    /** get a single value from buffered pipe (this function will block if no values available)
+        \return the element extracted
+    */
+    T getc(void)
+    {
+        int r = _r;
+        while (r == _w) // = !readable()
+            /* nothing / just wait */;
+        T t = _b[r];
+        _r = _inc(r);
+        return t;
+    }
+    
+    /*! get elements from the buffered pipe
+        \param p the elements extracted
+        \param n the maximum number elements to extract
+        \param t set to true if blocking, false otherwise
+        \return number elements extracted
+    */
+    int get(T* p, int n, bool t = false)
+    {
+        int c = n;
+        while (c)
+        {
+            int f;
+            for (;;) // wait for data
+            {
+                f = size();
+                if (f)  break;        // free space
+                if (!t) return n - c; // no space and not blocking
+                /* nothing / just wait */;
+            }
+            // check available data
+            if (c < f) f = c;
+            int r = _r;
+            int m = _s - r; 
+            // check wrap
+            if (f > m) f = m;
+            memcpy(p, &_b[r], f);
+            _r = _inc(r, f);
+            c -= f;
+            p += f;
+        }
+        return n - c;
+    }
+    
+    // the following functions are useful if you like to inspect 
+    // or parse the buffer in the reading thread/context
+    // --------------------------------------------------------
+    
+    /** set the parsing index and return the number of available 
+        elments starting this position.
+        \param ix the index to set.
+        \return the number of elements starting at this position 
+    */
+    int set(int ix) 
+    {
+        int sz = size();
+        ix = (ix > sz) ? sz : ix;
+        _o = _inc(_r, ix); 
+        return sz - ix;
+    }
+    
+    /** get the next element from parsing position and increment parsing index
+        \return the extracted element.
+    */
+    T next(void)
+    {
+        int o = _o;
+        T t = _b[o]; 
+        _o = _inc(o); 
+        return t; 
+    }
+    
+    /** commit the index, mark the current parsing index as consumed data.
+    */
+    void done(void) 
+    {
+        _r = _o; 
+    } 
+
+private:
+    /** increment the index
+        \param i index to increment
+        \param n the step to increment
+        \return the incremented index.
+    */
+    inline int _inc(int i, int n = 1)
+    {
+        i += n;
+        if (i >= _s)
+            i -= _s;
+        return i;
+    }
+
+    T*            _b; //!< buffer
+    T*            _a; //!< allocated buffer
+    int           _s; //!< size of buffer (s - 1) elements can be stored
+    volatile int  _w; //!< write index 
+    volatile int  _r; //!< read index 
+    int           _o; //!< offest index used by parsing functions  
+};
+
+#endif
+
+// End Of File