new file mode 100644
--- /dev/null
+++ b/src/core/ngx_hunk.h
@@ -0,0 +1,57 @@
+#ifndef _NGX_CHUNK_H_INCLUDED_
+#define _NGX_CHUNK_H_INCLUDED_
+
+
+#include <ngx_config.h>
+#include <ngx_types.h>
+#include <ngx_alloc.h>
+
+
+/* type */
+#define NGX_HUNK_TEMP       0x0001
+#define NGX_HUNK_MEMORY     0x0002
+#define NGX_HUNK_MMAP       0x0004
+#define NGX_HUNK_FILE       0x0008
+#define NGX_HUNK_FLUSH      0x0010
+/* in thread state flush means to write the hunk completely before return
+   in event-driven state flush means to start to write the hunk */
+#define NGX_HUNK_LAST       0x0020
+
+#define NGX_HUNK_IN_MEMORY  (NGX_HUNK_TEMP | NGX_HUNK_MEMORY | NGX_HUNK_MMAP )
+#define NGX_HUNK_TYPE       0x0ffff
+
+/* flags */
+#define NGX_HUNK_SHUTDOWN   0x10000
+/* can be used with NGX_HUNK_LAST only */
+
+
+typedef struct ngx_hunk_s ngx_hunk_t;
+struct ngx_hunk_s {
+    union {
+        char    *p;             /* start of current data */
+        off_t    f;   
+    } pos;
+    union {
+        char    *p;             /* end of current data */
+        off_t    f;   
+    } last;
+    int          type;
+    char        *start;         /* start of hunk */
+    char        *end;           /* end of hunk */
+    char        *pre_start;     /* start of pre-allocated hunk */
+    char        *post_end;      /* end of post-allocated hunk */
+    int          tag;
+    ngx_file_t   fd;
+};
+
+typedef struct ngx_chain_s  ngx_chain_t;
+struct ngx_chain_s {
+    ngx_hunk_t  *hunk;
+    ngx_chain_t *next;
+};
+
+
+ngx_hunk_t *ngx_get_hunk(ngx_pool_t *pool, int size, int before, int after);
+
+
+#endif /* _NGX_CHUNK_H_INCLUDED_ */