From 540dc9643efc866af6e7040634c9d7a17ca6c5b0 Mon Sep 17 00:00:00 2001
From: Jan Breuer <jan.breuer@jaybee.cz>
Date: 周六, 05 12月 2015 21:40:52 +0800
Subject: [PATCH] Fix error queue and resolve #67

---
 libscpi/src/fifo.c |  109 +++++++++++++++++++++++++++++++++++++++++++-----------
 1 files changed, 87 insertions(+), 22 deletions(-)

diff --git a/libscpi/src/fifo.c b/libscpi/src/fifo.c
index 600cf1a..a64d351 100644
--- a/libscpi/src/fifo.c
+++ b/libscpi/src/fifo.c
@@ -1,48 +1,113 @@
 
 #include "fifo_private.h"
 
-void fifo_init(fifo_t * fifo) {
+/**
+ * Initialize fifo
+ * @param fifo
+ */
+void fifo_init(scpi_fifo_t * fifo) {
     fifo->wr = 0;
     fifo->rd = 0;
     fifo->size = FIFO_SIZE;
 }
 
-void fifo_clear(fifo_t * fifo) {
+/**
+ * Empty fifo
+ * @param fifo
+ */
+void fifo_clear(scpi_fifo_t * fifo) {
     fifo->wr = 0;
     fifo->rd = 0;
 }
 
-scpi_bool_t fifo_add(fifo_t * fifo, int16_t value) {
-    /* FIFO full? */
-    if (fifo->wr == ((fifo->rd + fifo->size) % (fifo->size + 1))) {
-        fifo_remove(fifo, NULL);
-    }
-
-    fifo->data[fifo->wr] = value;
-    fifo->wr = (fifo->wr + 1) % (fifo->size + 1);
-
-    return TRUE;
+/**
+ * Test if fifo is empty
+ * @param fifo
+ * @return
+ */
+scpi_bool_t fifo_is_empty(scpi_fifo_t * fifo) {
+    return fifo->wr == fifo->rd;
 }
 
-scpi_bool_t fifo_remove(fifo_t * fifo, int16_t * value) {
-    /* FIFO empty? */
-    if (fifo->wr == fifo->rd) {
+/**
+ * Test if fifo is full
+ * @param fifo
+ * @return
+ */
+scpi_bool_t fifo_is_full(scpi_fifo_t * fifo) {
+    return fifo->wr == ((fifo->rd + fifo->size - 1) % (fifo->size));
+}
+
+/**
+ * Add element to fifo. If fifo is full, return FALSE.
+ * @param fifo
+ * @param value
+ * @return
+ */
+scpi_bool_t fifo_add(scpi_fifo_t * fifo, int16_t value) {
+    /* FIFO full? */
+    if (fifo_is_full(fifo)) {
         return FALSE;
     }
 
-    if(value) {
-        *value = fifo->data[fifo->rd];
-    }
-
-    fifo->rd = (fifo->rd + 1) % (fifo->size + 1);
+    fifo->data[fifo->wr] = value;
+    fifo->wr = (fifo->wr + 1) % (fifo->size);
 
     return TRUE;
 }
 
-scpi_bool_t fifo_count(fifo_t * fifo, int16_t * value) {
+/**
+ * Remove element form fifo
+ * @param fifo
+ * @param value
+ * @return FALSE - fifo is empty
+ */
+scpi_bool_t fifo_remove(scpi_fifo_t * fifo, int16_t * value) {
+    /* FIFO empty? */
+    if (fifo_is_empty(fifo)) {
+        return FALSE;
+    }
+
+    if (value) {
+        *value = fifo->data[fifo->rd];
+    }
+
+    fifo->rd = (fifo->rd + 1) % (fifo->size);
+
+    return TRUE;
+}
+
+/**
+ * Remove last element from fifo
+ * @param fifo
+ * @param value
+ * @return FALSE - fifo is empty
+ */
+scpi_bool_t fifo_remove_last(scpi_fifo_t * fifo, int16_t * value) {
+    /* FIFO empty? */
+    if (fifo_is_empty(fifo)) {
+        return FALSE;
+    }
+
+    fifo->wr = (fifo->wr + fifo->size - 1) % (fifo->size);
+
+    if (value) {
+        *value = fifo->data[fifo->wr];
+    }
+
+    return TRUE;
+}
+
+/**
+ * Retrive number of elements in fifo
+ * @param fifo
+ * @param value
+ * @return
+ */
+scpi_bool_t fifo_count(scpi_fifo_t * fifo, int16_t * value) {
     *value = fifo->wr - fifo->rd;
     if (*value < 0) {
-        *value += (fifo->size + 1);
+        *value += (fifo->size);
     }
     return TRUE;
 }

--
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