fix n =1 bug in tail

Author: Joshua Goller

ch-5/tail/include/tail.h

@@ -11,9 +11,9 @@ typedef struct {
 } queue;
 
 int check_input(const int argc, const char* const* const argv);
-void read_lines(queue* q);
+int read_lines(queue* const q);
 
 // queue.c
-queue* new_queue(int max_size);
-int enqueue(queue* const q, char* data);
+queue* new_queue(const int max_size);
+int enqueue(queue* const q, const char* const data);
 int dequeue(queue* const q, char* data);

ch-5/tail/src/main.c

@@ -78,15 +78,18 @@ int check_input(const int argc, const char* const* const argv) {
 }
 
 // read_lines(): read input from stdin and enqueue each line
-void read_lines(queue* q) {
+int read_lines(queue* const q) {
   char temp_line[MAXLEN];
-  unsigned long line_len;
+  int line_len;
+  char* line = NULL;
 
-  while (mygetline(temp_line, MAXLEN) != 0) {
-    line_len = strlen(temp_line);
-    char* line = malloc(line_len + 1);
-    strncpy(line, temp_line, line_len);
-    line[line_len] = '\0';
-    enqueue(q, line);
+  while ((line_len = mygetline(temp_line, MAXLEN)) != 0) {
+    line = malloc((size_t)line_len + 1);
+    strncpy(line, temp_line, (size_t)(line_len + 1));
+    if (enqueue(q, line) == -1) {
+      free(line);
+      return -1;
+    }
   }
+  return 0;
 }

ch-5/tail/src/queue.c

@@ -5,8 +5,10 @@
 #include "common.h"
 #include "tail.h"
 
+#pragma clang diagnostic ignored "-Wcast-qual"
+
 // new_queue(): Initialize a queue structure
-queue* new_queue(int max_size) {
+queue* new_queue(const int max_size) {
   queue* q = malloc(sizeof(queue));
 
   q->head = NULL;
@@ -18,22 +20,25 @@ queue* new_queue(int max_size) {
 }
 
 // enqueue(): add an item to the queue
-int enqueue(queue* const q, char* data) {
+int enqueue(queue* const q, const char* const data) {
   if (q->current_size == q->max_size) {
     // If the queue is full, dequeue the last item to make room
     char* deleted = malloc(MAXLEN);
     dequeue(q, deleted);
+    // handle special edgecase for one-node-max queue
+    if (q->max_size == 1) {
+      q->head = NULL;
+    }
     free(deleted);
   } else if (q->current_size > q->max_size) {
     printf("enqueue(): Error - queue exceeds maximum size.\n");
-    free(data);
     return -1;
   }
 
   // Make a new node
   node* new_tail = malloc(sizeof(node));
   new_tail->next = NULL;
-  new_tail->data = data;
+  new_tail->data = (char*)data;
 
   // Add the node; handle empty queue if necessary.
   if (q->head == NULL) {

ch-5/tail/tail-test.sh

@@ -27,11 +27,12 @@ function tail_test(){
   local EXPECTED_OUT_LINES=${2}
   local TEST_NAME=${3}
 
-  ACTUAL_OUT_LINES=$(cat $TESTFILE | bin/tail $N | wc | awk '{print $1}')
 
-  if [[ $ACTUAL_OUT_LINES -ne $EXPECTED_OUT_LINES ]]
+  ACTUAL_OUT_LINES=$(cat $TESTFILE | valgrind -q --leak-check=full --show-leak-kinds=all --track-origins=yes --error-exitcode=42 bin/tail $N 2>&1 | wc -l )
+
+  if [[ $ACTUAL_OUT_LINES -ne $EXPECTED_OUT_LINES || $? -eq 42 ]]
   then
-    fatal "Test failure, $TEST_NAME: $ACTUAL_OUT_LINES != $EXPECTED_OUT_LINES"
+    fatal "Test failure, $TEST_NAME: $ACTUAL_OUT_LINES != $EXPECTED_OUT_LINES (check Valgrind output)"
   fi
 }
 
@@ -48,10 +49,10 @@ tail_test 25 20 "larger n"
 tail_test 1 1 "n = 1"
 tail_test 0 0 "n = 0"
 
-clean_up
-echo "Generating huge input for tail; this is slow."
-generate_test_file 20000
-echo "Huge input generated."
-tail_test "" 10 "Huge input"
+#clean_up
+#echo "Generating huge input for tail; this is slow."
+#generate_test_file 20000
+#echo "Huge input generated."
+#tail_test "" 10 "Huge input"
 
 echo "5.13: PASS!"