Add 'done' argument to fread_csv_line

README.md

@@ -43,13 +43,14 @@ Both the array and the strings in the array are `malloc`'d.
 
 ## Documentation (fread_csv_line.c)
 
-    char *fread_csv_line(FILE *fp, int max_line_size, int *err)
+    char *fread_csv_line(FILE *fp, int max_line_size, int *done, int *err)
 
 Given a file pointer, extract a line of CSV from it.
 
 Other arguments:
   int max_line_size:  a maximum line size.  Lines longer than this will
     cause fread_csv_line to return NULL.
+  int *done:  Pointer to an int which will be set to 1 if the end of fp is reached.
   int *err:  Pointer to an int where error codes will be
     written.  The two error codes, defined in `csv.h`, are:
     CSV_ERR_LONGLINE and CSV_ERR_NO_MEMORY.
@@ -60,10 +61,11 @@ sense) in unpredictable ways, and will break if other things tamper with the fil
 position in between calls to fread_csv_line.
 
 Warning: `fread_csv_line` will not work correctly if called on different files in
-parallel.
+parallel.  (Hopefully sometime in the future we'll add a proper `init` system to
+deal with this).
 
-Hopefully sometime in the future we'll add a proper `init` system to deal with the
-latter warning.
+Warning: Calling fread_csv_line on fp after a previous call exhausted the file
+  (indicated by *done), is undefined behavior.
 
 ## TODO
 

fread_csv_line.c

@@ -33,11 +33,15 @@ while(0)
  *
  * Other arguments:
  * size_t max_line_size: Maximum line size, in bytes.
+ * int *done: Pointer to an int that will be set to 1 when file is exhausted.
  * int *err: Pointer to an int where error code will be written.
  *
+ * Warning: Calling this function on an exhausted file (as indicated by the
+ *   'done' flag) is undefined behavior.
+ *
  * See csv.h for definitions of error codes.
  */
-char *fread_csv_line(FILE *fp, int max_line_size, int *err) {
+char *fread_csv_line(FILE *fp, int max_line_size, int *done, int *err) {
     static FILE *bookmark;
     static char read_buf[READ_BLOCK_SIZE], *read_ptr, *read_end;
     static int fread_len, prev_max_line_size = -1;
@@ -70,8 +74,7 @@ char *fread_csv_line(FILE *fp, int max_line_size, int *err) {
         QUICK_GETC(ch, fp);
 
         if ( !ch || (ch == '\n' && !fQuote)) {
-            *bptr = '\0';
-            return strdup(buf);
+            break;
         }
 
         if ( bptr >= limit ) {
@@ -87,8 +90,7 @@ char *fread_csv_line(FILE *fp, int max_line_size, int *err) {
 
                 if ( ch != '\"' ) {
                     if ( !ch || ch == '\n' ) {
-                        *bptr = '\0';
-                        return strdup(buf);
+                        break;
                     }
                     fQuote = 0;
                 }
@@ -98,4 +100,8 @@ char *fread_csv_line(FILE *fp, int max_line_size, int *err) {
             fQuote = 1;
         }
     }
+
+    *done = !ch;
+    *bptr = '\0';
+    return strdup(buf);
 }