LZ4: Do not reverse bottom-up images

Reversing the bottom-up images in the server is not needed since Pixman,
in the client, is able to deal with them. As a result, the previous code
was more complex and wrong. This commit fixes and cleans it.

3 files changed, 14 insertions, 24 deletions

diff --git a/server/lz4_encoder.c b/server/lz4_encoder.c
index aa03721d..2327e9a2 100644
--- a/server/lz4_encoder.c
+++ b/server/lz4_encoder.c
@@ -49,21 +49,20 @@ void lz4_encoder_destroy(Lz4EncoderContext* encoder)
     free(encoder);
 }
 
-int lz4_encode(Lz4EncoderContext *lz4, int height, int stride,
-               uint8_t *io_ptr, unsigned int num_io_bytes)
+int lz4_encode(Lz4EncoderContext *lz4, int height, int stride, uint8_t *io_ptr,
+               unsigned int num_io_bytes, int top_down)
 {
     Lz4Encoder *enc = (Lz4Encoder *)lz4;
     uint8_t *lines;
     int num_lines = 0;
     int total_lines = 0;
     int in_size, enc_size, out_size, already_copied;
-    int stride_abs = abs(stride);
     uint8_t *in_buf, *compressed_lines;
     uint8_t *out_buf = io_ptr;
     LZ4_stream_t *stream = LZ4_createStream();
 
     // Encode direction
-    *(out_buf++) = stride < 0 ? 1 : 0;
+    *(out_buf++) = top_down ? 1 : 0;
     num_io_bytes--;
     out_size = 1;
 
@@ -74,9 +73,9 @@ int lz4_encode(Lz4EncoderContext *lz4, int height, int stride,
             LZ4_freeStream(stream);
             return 0;
         }
-        in_buf = stride < 0 ? lines - (stride_abs * (num_lines - 1)) : lines;
-        lines += stride * num_lines;
-        in_size = stride_abs * num_lines;
+        in_buf = lines;
+        in_size = stride * num_lines;
+        lines += in_size;
         compressed_lines = (uint8_t *) malloc(LZ4_compressBound(in_size) + 4);
         enc_size = LZ4_compress_continue(stream, (const char *) in_buf,
                                          (char *) compressed_lines + 4, in_size);
diff --git a/server/lz4_encoder.h b/server/lz4_encoder.h
index f3359c09..97b8dc85 100644
--- a/server/lz4_encoder.h
+++ b/server/lz4_encoder.h
@@ -43,8 +43,7 @@ struct Lz4EncoderUsrContext {
 Lz4EncoderContext* lz4_encoder_create(Lz4EncoderUsrContext *usr);
 void lz4_encoder_destroy(Lz4EncoderContext *encoder);
 
-/* returns the total size of the encoded data. Images must be supplied from the
-   top line to the bottom */
-int lz4_encode(Lz4EncoderContext *lz4, int height, int stride,
-               uint8_t *io_ptr, unsigned int num_io_bytes);
+/* returns the total size of the encoded data. */
+int lz4_encode(Lz4EncoderContext *lz4, int height, int stride, uint8_t *io_ptr,
+               unsigned int num_io_bytes, int top_down);
 #endif
diff --git a/server/red_worker.c b/server/red_worker.c
index 8f07ee92..922a459d 100644
--- a/server/red_worker.c
+++ b/server/red_worker.c
@@ -6422,7 +6422,6 @@ static int red_lz4_compress_image(DisplayChannelClient *dcc, SpiceImage *dest,
     Lz4Data *lz4_data = &worker->lz4_data;
     Lz4EncoderContext *lz4 = worker->lz4;
     int lz4_size = 0;
-    int stride;
 
 #ifdef COMPRESS_STAT
     stat_time_t start_time = stat_now();
@@ -6454,20 +6453,13 @@ static int red_lz4_compress_image(DisplayChannelClient *dcc, SpiceImage *dest,
 
     lz4_data->data.u.lines_data.chunks = src->data;
     lz4_data->data.u.lines_data.stride = src->stride;
+    lz4_data->data.u.lines_data.next = 0;
+    lz4_data->data.u.lines_data.reverse = 0;
     lz4_data->usr.more_lines = lz4_usr_more_lines;
 
-    if ((src->flags & SPICE_BITMAP_FLAGS_TOP_DOWN)) {
-        lz4_data->data.u.lines_data.next = 0;
-        lz4_data->data.u.lines_data.reverse = 0;
-        stride = src->stride;
-    } else {
-        lz4_data->data.u.lines_data.next = src->data->num_chunks - 1;
-        lz4_data->data.u.lines_data.reverse = 1;
-        stride = -src->stride;
-    }
-
-    lz4_size = lz4_encode(lz4, src->y, stride, (uint8_t*)lz4_data->data.bufs_head->buf,
-                          sizeof(lz4_data->data.bufs_head->buf));
+    lz4_size = lz4_encode(lz4, src->y, src->stride, (uint8_t*)lz4_data->data.bufs_head->buf,
+                          sizeof(lz4_data->data.bufs_head->buf),
+                          src->flags & SPICE_BITMAP_FLAGS_TOP_DOWN);
 
     // the compressed buffer is bigger than the original data
     if (lz4_size > (src->y * src->stride)) {