Improve apr_file_gets() performance on buffered files by not calling

apr_file_read() on each byte if we don't have to.

(mod_negotiation requests call apr_file_gets() for each line in the map file,
which can get to be quite expensive to have repeated memcpy()'s for one byte!)


git-svn-id: http://svn.apache.org/repos/asf/apr/apr/trunk@65294 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 58 insertions, 11 deletions

diff --git a/CHANGES b/CHANGES
index 6a871e3f9..70a71eb2d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,4 +1,7 @@
 Changes for APR 1.1 [Deferring these features when 1.0 is rolled out.]
+
+  *) Improve apr_file_gets() performance on buffered files. [Justin Erenkrantz]
+
   *) Win32: Fix bug in apr_socket_sendfile that interferred with
      Win32 LSPs. PR 23982 [Jan Bilek, Bill Stoddard]
 
diff --git a/file_io/unix/readwrite.c b/file_io/unix/readwrite.c
index 1e6a6e665..98a11421d 100644
--- a/file_io/unix/readwrite.c
+++ b/file_io/unix/readwrite.c
@@ -24,9 +24,6 @@
 #define USE_WAIT_FOR_IO
 #endif
 
-/* problems: 
- * 1) ungetchar not used for buffered files
- */
 APR_DECLARE(apr_status_t) apr_file_read(apr_file_t *thefile, void *buf, apr_size_t *nbytes)
 {
     apr_ssize_t rv;
@@ -311,18 +308,65 @@ APR_DECLARE(apr_status_t) apr_file_gets(char *str, int len, apr_file_t *thefile)
         return APR_SUCCESS;
     }
 
-    while (str < final) { /* leave room for trailing '\0' */
-        nbytes = 1;
-        rv = apr_file_read(thefile, str, &nbytes);
-        if (rv != APR_SUCCESS) {
-            break;
+    /* If we have an underlying buffer, we can be *much* more efficient
+     * and skip over the apr_file_read calls.
+     */
+    if (thefile->buffered) {
+
+#if APR_HAS_THREADS
+        if (thefile->thlock) {
+            apr_thread_mutex_lock(thefile->thlock);
+        }
+#endif
+
+        if (thefile->direction == 1) {
+            apr_file_flush(thefile);
+            thefile->direction = 0;
+            thefile->bufpos = 0;
+            thefile->dataRead = 0;
         }
-        if (*str == '\n') {
+
+        while (str < final) { /* leave room for trailing '\0' */
+            /* Force ungetc leftover to call apr_file_read. */
+            if (thefile->bufpos < thefile->dataRead &&
+                thefile->ungetchar == -1) {
+                *str = thefile->buffer[thefile->bufpos++];
+            }
+            else {
+                nbytes = 1;
+                rv = apr_file_read(thefile, str, &nbytes);
+                if (rv != APR_SUCCESS) {
+                    break;
+                }
+            }
+            if (*str == '\n') {
+                ++str;
+                break;
+            }
+            ++str;
+        }
+
+#if APR_HAS_THREADS
+        if (thefile->thlock) {
+            apr_thread_mutex_unlock(thefile->thlock);
+        }
+#endif
+    }
+    else {
+        while (str < final) { /* leave room for trailing '\0' */
+            nbytes = 1;
+            rv = apr_file_read(thefile, str, &nbytes);
+            if (rv != APR_SUCCESS) {
+                break;
+            }
+            if (*str == '\n') {
+                ++str;
+                break;
+            }
             ++str;
-            break;
         }
-        ++str;
     }
+
     /* We must store a terminating '\0' if we've stored any chars. We can
      * get away with storing it if we hit an error first. 
      */