src/dj.c

@@ -62,6 +62,34 @@ static int write_flags = O_WRONLY | O_CREAT;
 /* Macro to check if fd is stdin or stdout */
 #define fdisstd(fd) ((fd) == STDIN_FILENO || (fd) == STDOUT_FILENO)
 
+/* Fills the unused portion of io's buffer with padding, updating io->bufuse.
+ * Returns io. */
+static struct Io *
+Io_bufrpad(struct Io *io, int padding){
+
+	assert(io != NULL);
+
+	memset(io->buf + io->bufuse, padding, io->bs - io->bufuse);
+	io->bufuse = io->bs;
+
+	return io;
+}
+
+/* Copies from the buffer in src to the buffer in dest no more than n units,
+ * removing the copied units from src and permuting the remaining units in the
+ * src buffer to the start of the buffer, modifying both the src and dest
+ * bufuse and returning dest. */
+static struct Io*
+Io_bufxfer(struct Io *dest, struct Io *src, int n){
+
+	assert(dest != NULL && src != NULL);
+
+	memcpy(dest->buf, src->buf, (dest->bufuse = n));
+	memmove(src->buf, src->buf + n, (src->bufuse -= n));
+
+	return dest;
+}
+
 /* Opens io->fn and saves the file descriptor into io->fd. Returns io->fd,
  * which will be -1 if an error occured. */
 static int
@@ -281,12 +309,8 @@ int main(int argc, char *argv[]){
 			printio(fmt, io);
 			if(!noerror)
 				count = 1;
-			if(align >= 0){
-				/* fill the rest of the ibuf with padding */
-				memset(io[0].buf + io[0].bufuse, align,
-					io[0].bs - io[0].bufuse);
-				io->bufuse = io->bs;
-			}
+			if(align >= 0)
+				Io_bufrpad(&io[0], align);
 		}else
 			++io[0].rec;
 
@@ -294,18 +318,10 @@ int main(int argc, char *argv[]){
 		do{
 			int t;
 
-			if(io[0].bs <= io[1].bs){
+			if(io[1].bs > io[0].bs){
 				int n;
 
-				/* saturate obuf */
-				memcpy(io[1].buf, io[0].buf,
-				       (io[1].bufuse = (n = MIN(io[0].bufuse, io[1].bs))));
-				/* permute the copied units out of ibuf */
-				memmove(io[0].buf, io[0].buf + n, (io[0].bufuse -= n));
-			}else /* if(io[0].bs < io[1].bs) */ {
-				int n;
-
-				/* drain what we can from ibuf */
+				/* copy from ibuf as much as possible to the obuf */
 				memcpy(io[1].buf + io[1].bufuse, io[0].buf,
 				       (n = MIN(io[0].bufuse, io[1].bs - io[1].bufuse)));
 				io[1].bufuse += n;
@@ -314,8 +330,9 @@ int main(int argc, char *argv[]){
 				io[0].bufuse -= n;
 
 				if(io[0].bs + io[1].bufuse <= io[1].bs && count != 1)
-					continue; /* obuf not saturated - we could write more */
-			}
+					continue; /* we could write more */
+			}else
+				Io_bufxfer(&io[1], &io[0], MIN(io[0].bufuse, io[1].bs));
 
 			t = io[1].bufuse;
 			Io_write(&io[1]);