Align fileio's map_ptr() reads. Fixes bug 8177.

diff --git a/fileio.c b/fileio.c
index c0fca9b8d3d09345571583416f2bf7b293e4f1f1..c56b0d9a2f4b7b1b28eb29d2655ee01ea63fd8aa 100644 (file)
--- a/fileio.c
+++ b/fileio.c
@@ -26,6 +26,13 @@
 #define ENODATA EAGAIN
 #endif
 
+/* We want all reads to be aligned on 1K boundries. */
+#define ALIGN_BOUNDRY 1024
+/* How far past the boundary is an offset? */
+#define ALIGNED_OVERSHOOT(oft) ((oft) & (ALIGN_BOUNDRY-1))
+/* Round up a length to the next boundary */
+#define ALIGNED_LENGTH(len) ((((len) - 1) | (ALIGN_BOUNDRY-1)) + 1)
+
 extern int sparse_files;
 
 static OFF_T sparse_seek = 0;
@@ -171,7 +178,7 @@ struct map_struct *map_file(int fd, OFF_T len, int32 read_size, int32 blk_size)
 
        map->fd = fd;
        map->file_size = len;
-       map->def_window_size = read_size;
+       map->def_window_size = ALIGNED_LENGTH(read_size);
 
        return map;
 }
@@ -181,7 +188,7 @@ struct map_struct *map_file(int fd, OFF_T len, int32 read_size, int32 blk_size)
 char *map_ptr(struct map_struct *map, OFF_T offset, int32 len)
 {
        OFF_T window_start, read_start;
-       int32 window_size, read_size, read_offset;
+       int32 window_size, read_size, read_offset, align_fudge;
 
        if (len == 0)
                return NULL;
@@ -196,12 +203,13 @@ char *map_ptr(struct map_struct *map, OFF_T offset, int32 len)
                return map->p + (offset - map->p_offset);
 
        /* nope, we are going to have to do a read. Work out our desired window */
-       window_start = offset;
+       align_fudge = (int32)ALIGNED_OVERSHOOT(offset);
+       window_start = offset - align_fudge;
        window_size = map->def_window_size;
        if (window_start + window_size > map->file_size)
                window_size = (int32)(map->file_size - window_start);
-       if (len > window_size)
-               window_size = len;
+       if (window_size < len + align_fudge)
+               window_size = ALIGNED_LENGTH(len + align_fudge);
 
        /* make sure we have allocated enough memory for the window */
        if (window_size > map->p_size) {
@@ -257,7 +265,7 @@ char *map_ptr(struct map_struct *map, OFF_T offset, int32 len)
                read_size -= nread;
        }
 
-       return map->p;
+       return map->p + align_fudge;
 }