[vlc-devel] [PATCH 1/3] blockhelper: create new block_FindMaskedFlags

[davidf+nntp at woaf.net]

From: David Flynn <davidf at rd.bbc.co.uk>

Searches a bytestream_t, between two points, returning the position of
the first block with flags that are a subset of given mask.

Signed-off-by: David Flynn <davidf at rd.bbc.co.uk>
---
 include/vlc_block_helper.h |   61 ++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 61 insertions(+), 0 deletions(-)

diff --git a/include/vlc_block_helper.h b/include/vlc_block_helper.h
index 654d26b..1938e5a 100644
--- a/include/vlc_block_helper.h
+++ b/include/vlc_block_helper.h
@@ -520,4 +520,65 @@ static inline int block_FindStartcodeFromOffset(
     return VLC_EGENERIC;
 }
 
+/**
+ * block_FindMaskedFlags:
+ *
+ * searches @p_bytestream, between @pi_start and @pi_end, for the first
+ * block with flags that are a subset of @pi_flags_mask.
+ *
+ * *pi_end is updated to contain the offset of byte after the last
+ * block searched.
+ *
+ * On Success, *pi_offset is updated to the offset of the matching block.
+ *             *pi_flags_mask is updated to the unmasked value of flags found
+ * On Failure, *pi_offset is not modified.
+ */
+static inline int block_FindMaskedFlags(
+    block_bytestream_t *p_bytestream, uint32_t *pi_flags_mask,
+    size_t *pi_start, size_t *pi_end)
+{
+    block_t *p_block = p_bytestream->p_block;
+    size_t i_offset = p_bytestream->i_offset + *pi_start;
+    size_t i_length = *pi_end - *pi_start;
+
+    /* Find the block i_offset indexes */
+    for(; p_block != NULL; p_block = p_block->p_next )
+    {
+        if( i_offset < p_block->i_buffer )
+            break;
+        i_offset -= p_block->i_buffer;
+    }
+
+    /* ensure there is atleast i_start of data */
+    if( !p_block )
+        return VLC_EGENERIC;
+
+    /* special case when i_len == 0 */
+    if( !i_length )
+        return VLC_ENOITEM;
+
+    /* i_offset will be the offset to the start of each block */
+    /* *pi_end will be the offset of the next next block */
+    *pi_end = *pi_start - i_offset;
+    i_offset = *pi_start;
+    i_length += i_offset;
+
+    /* search for a block that has any of the flags set in mask */
+    for(; p_block; p_block = p_block->p_next )
+    {
+        *pi_end += p_block->i_buffer;
+        if( p_block->i_flags & *pi_flags_mask )
+        {
+            *pi_flags_mask = p_block->i_flags;
+            *pi_start = i_offset;
+            return VLC_SUCCESS;
+        }
+        i_offset = *pi_end;
+        if( i_length < p_block->i_buffer )
+            break;
+        i_length -= p_block->i_buffer;
+    }
+
+    return VLC_ENOITEM;
+}
 #endif /* VLC_BLOCK_HELPER_H */
-- 
1.5.6.5