From 88d91faba5df82e70abfd95b60c96b4a0bd53744 Mon Sep 17 00:00:00 2001
From: Michael Sevakis <jethead71@rockbox.org>
Date: Thu, 10 Feb 2011 05:56:21 +0000
Subject: [PATCH] buffering: Don't execute move-handle-ony case if handle is of
 metadata type (atomic) and must be kept fully buffered. Manage handle
 corruption guard and handle buffering with one set of logic which allows
 reading of the maximum amount of data without overflow. 'FIXME' regarding
 handle corruption guard is really part of expected operation when thread that
 does the handle closing hasn't yet performed the delegated task before
 rebuffering starts.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29270 a1c6a512-1295-4272-9138-f99709370657
---
 apps/buffering.c | 38 +++++++++++++++++---------------------
 1 file changed, 17 insertions(+), 21 deletions(-)

diff --git a/apps/buffering.c b/apps/buffering.c
index 1482d6790b..14db47bb91 100644
--- a/apps/buffering.c
+++ b/apps/buffering.c
@@ -666,31 +666,25 @@ static bool buffer_handle(int handle_id)
     while (h->filerem > 0 && !stop)
     {
         /* max amount to copy */
-        size_t copy_n = MIN( MIN(h->filerem, BUFFERING_DEFAULT_FILECHUNK),
+        ssize_t copy_n = MIN( MIN(h->filerem, BUFFERING_DEFAULT_FILECHUNK),
                              buffer_len - h->widx);
+        uintptr_t offset = h->next ? ringbuf_offset(h->next) : buf_ridx;
+        ssize_t overlap = ringbuf_add_cross(h->widx, copy_n, offset);
 
-        ssize_t overlap;
-        uintptr_t next_handle = ringbuf_offset(h->next);
+        if (!h->next)
+            overlap++; /* sub one more below to avoid buffer overflow */
 
-        /* stop copying if it would overwrite the reading position */
-        if (ringbuf_add_cross(h->widx, copy_n, buf_ridx) >= 0)
-            return false;
-
-        /* FIXME: This would overwrite the next handle
-         * If this is true, then there's a handle even though we have still
-         * data to buffer. This should NEVER EVER happen! (but it does :( ) */
-        if (h->next && (overlap
-                = ringbuf_add_cross(h->widx, copy_n, next_handle)) > 0)
+        if (overlap > 0)
         {
-            /* stop buffering data for now and post-pone buffering the rest */
+            /* read only up to available space and stop if it would overwrite
+               the reading position or the next handle */
             stop = true;
-            DEBUGF( "%s(): Preventing handle corruption: h1.id:%d h2.id:%d"
-                    " copy_n:%lu overlap:%ld h1.filerem:%lu\n", __func__,
-                    h->id, h->next->id, (unsigned long)copy_n, (long)overlap,
-                    (unsigned long)h->filerem);
             copy_n -= overlap;
         }
 
+        if (copy_n <= 0)
+            return false; /* no space for read */
+
         /* rc is the actual amount read */
         int rc = read(h->fd, &buffer[h->widx], copy_n);
 
@@ -830,12 +824,14 @@ static void shrink_handle(struct memory_handle *h)
     if (!h)
         return;
 
-    if (h->next && h->filerem == 0 &&
-            (h->type == TYPE_ID3 || h->type == TYPE_CUESHEET ||
-             h->type == TYPE_BITMAP || h->type == TYPE_CODEC ||
-             h->type == TYPE_ATOMIC_AUDIO))
+    if (h->type == TYPE_ID3 || h->type == TYPE_CUESHEET ||
+        h->type == TYPE_BITMAP || h->type == TYPE_CODEC ||
+        h->type == TYPE_ATOMIC_AUDIO)
     {
         /* metadata handle: we can move all of it */
+        if (!h->next || h->filerem != 0)
+            return; /* Last handle or not finished loading */
+
         uintptr_t handle_distance =
             ringbuf_sub(ringbuf_offset(h->next), h->data);
         delta = handle_distance - h->available;