buffer.cpp

00001 #include "mbed.h"
00002 #include "rtos.h"
00003 #include "string.h"
00004 #include <stdio.h>
00005 #include <ctype.h>
00006 
00007 // A First-In-First-Out buffer is used with streams of data.
00008 // It is thread-safe and often used to buffer data across threads
00009 
00010 #define BUFFERSIZE 100
00011 /*
00012 typedef struct {
00013         uint8_t   id;
00014         float    tempCelsius;
00015         float    tempFarenheit;
00016         float    humidity;
00017         float    pressure;
00018         int32_t  accelerometer[3];
00019         int32_t  gyroscope[3];
00020         int32_t  magnetometer[3];
00021         char*    date;
00022     } log_data;
00023 
00024 Semaphore *spaceAvailable;
00025 Semaphore *samplesInBuffer;
00026 Mutex *bufferLock;
00027 
00028 log_data buffer[BUFFERSIZE];
00029 unsigned int newestIndex = BUFFERSIZE-1;
00030 unsigned int oldestIndex = BUFFERSIZE-1;
00031 
00032 class Buffer {
00033 public:
00034     void addDataToQueue(log_data d) {
00035     // Check whether there's space
00036     int32_t Nspaces = spaceAvailable->wait();
00037     
00038     // If there's space, use the mutex
00039     bufferLock->lock();
00040     
00041     // Update buffer
00042     newestIndex = (newestIndex+1) % BUFFERSIZE;
00043     buffer[newestIndex] = d;
00044     printf("\tAdded log_data id %d to buffer, %d space available\n",
00045         unsigned(d.id), Nspaces-1);
00046     
00047     bufferLock->unlock();
00048     
00049     // Signal that a sample has been added
00050     samplesInBuffer->release();
00051     }
00052     
00053     log_data takeCharacterFromQueue(){
00054     // Check whether there are samples
00055     int32_t Nsamples = samplesInBuffer->wait();
00056     
00057     bufferLock->lock();
00058     
00059     oldestIndex = (oldestIndex+1) % BUFFERSIZE;
00060     log_data d = buffer[oldestIndex];
00061     printf("\tRemoved log_data id %d from buffer, %d bytes remaining\n",
00062         unsigned(d.id), Nsamples-1);
00063     
00064     bufferLock->unlock();
00065     
00066     //Signal there's space in the buffer
00067     spaceAvailable->release();
00068     
00069     return d;
00070     }
00071     
00072     Buffer() {
00073         bufferLock = new Mutex();
00074         spaceAvailable = new Semaphore(BUFFERSIZE);
00075         samplesInBuffer = new Semaphore(0);
00076     }
00077 };
00078 */