Read in blocks rather than one char at a time, greatly improves speed

git-svn-id: svn://busybox.net/trunk/busybox@7907 69ca8d6d-28ef-0310-b511-8ec308f3f277

1 files changed, 23 insertions, 4 deletions

diff --git a/archival/libunarchive/seek_by_char.c b/archival/libunarchive/seek_by_char.c
index f33935cb5..77da4ef2e 100644
--- a/archival/libunarchive/seek_by_char.c
+++ b/archival/libunarchive/seek_by_char.c
@@ -14,12 +14,31 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
+#include <stdlib.h>
+
 #include "unarchive.h"
+#include "busybox.h"
 
-extern void seek_by_char(const archive_handle_t *archive_handle, const unsigned int amount)
+/*      If we are reading through a pipe(), or from stdin then we cant lseek,
+ *  we must read and discard the data to skip over it.
+ *
+ *  TODO: rename to seek_by_read
+ */
+extern void seek_by_char(const archive_handle_t *archive_handle, const unsigned int jump_size)
 {
-        unsigned int i;
-        for (i = 0; i < amount; i++) {
-                archive_xread_char(archive_handle);
+        unsigned int remaining = jump_size;
+        unsigned int read_amount;
+        RESERVE_CONFIG_BUFFER(buf, BUFSIZ);
+
+        while (remaining > 0) {
+                if (remaining > BUFSIZ) {
+                        read_amount = BUFSIZ;
+                } else {
+                        read_amount = remaining;
+                }
+                read_amount = archive_xread(archive_handle, buf, read_amount);
+                remaining -= read_amount;
         }
+
+        RELEASE_CONFIG_BUFFER(buf);
 }