[v1,1/8] dmg: Introduce a new struct to cache random access points

Commit Message

Ashijeet Acharya April 25, 2017, 7:59 p.m. UTC

We need to cache the random access point while performing partial
decompression so that we can resume decompression from that point
onwards in our next sequential read request. Introduce a new struct
DMGReadState which will help us do this.

Signed-off-by: Ashijeet Acharya <[e-mail]>
---
 block/dmg.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

Patch

diff --git a/block/dmg.h b/block/dmg.h
index b592d6f..ee67ae1 100644
--- a/block/dmg.h
+++ b/block/dmg.h
@@ -31,6 +31,15 @@ 
 #include "block/block_int.h"
 #include <zlib.h>
 
+/* used to cache current position in compressed input stream */
+typedef struct DMGReadState {
+    uint8_t *saved_next_in;
+    int64_t saved_avail_in;
+    int32_t saved_chunk_type;
+    int64_t sectors_read; /* possible sectors read in each cycle */
+    int32_t sector_offset_in_chunk;
+} DMGReadState;
+
 typedef struct BDRVDMGState {
     CoMutex lock;
     /* each chunk contains a certain number of sectors,
@@ -51,6 +60,7 @@  typedef struct BDRVDMGState {
     uint8_t *compressed_chunk;
     uint8_t *uncompressed_chunk;
     z_stream zstream;
+    DMGReadState *drs;
 } BDRVDMGState;
 
 extern int (*dmg_uncompress_bz2)(char *next_in, unsigned int avail_in,