git-tar-tree: no more void pointer arithmetic

[git.git] / delta.h

diff --git a/delta.h b/delta.h
index 31d1820..7b3f86d 100644 (file)
--- a/delta.h
+++ b/delta.h
@@ -1,12 +1,75 @@
 #ifndef DELTA_H
 #define DELTA_H
 
-/* handling of delta buffers */
-extern void *diff_delta(void *from_buf, unsigned long from_size,
-                       void *to_buf, unsigned long to_size,
-                       unsigned long *delta_size, unsigned long max_size);
-extern void *patch_delta(void *src_buf, unsigned long src_size,
-                        void *delta_buf, unsigned long delta_size,
+/* opaque object for delta index */
+struct delta_index;
+
+/*
+ * create_delta_index: compute index data from given buffer
+ *
+ * This returns a pointer to a struct delta_index that should be passed to
+ * subsequent create_delta() calls, or to free_delta_index().  A NULL pointer
+ * is returned on failure.  The given buffer must not be freed nor altered
+ * before free_delta_index() is called.  The returned pointer must be freed
+ * using free_delta_index().
+ */
+extern struct delta_index *
+create_delta_index(const void *buf, unsigned long bufsize);
+
+/*
+ * free_delta_index: free the index created by create_delta_index()
+ *
+ * Given pointer must be what create_delta_index() returned, or NULL.
+ */
+extern void free_delta_index(struct delta_index *index);
+
+/*
+ * create_delta: create a delta from given index for the given buffer
+ *
+ * This function may be called multiple times with different buffers using
+ * the same delta_index pointer.  If max_delta_size is non-zero and the
+ * resulting delta is to be larger than max_delta_size then NULL is returned.
+ * On success, a non-NULL pointer to the buffer with the delta data is
+ * returned and *delta_size is updated with its size.  The returned buffer
+ * must be freed by the caller.
+ */
+extern void *
+create_delta(const struct delta_index *index,
+            const void *buf, unsigned long bufsize,
+            unsigned long *delta_size, unsigned long max_delta_size);
+
+/*
+ * diff_delta: create a delta from source buffer to target buffer
+ *
+ * If max_delta_size is non-zero and the resulting delta is to be larger
+ * than max_delta_size then NULL is returned.  On success, a non-NULL
+ * pointer to the buffer with the delta data is returned and *delta_size is
+ * updated with its size.  The returned buffer must be freed by the caller.
+ */
+static inline void *
+diff_delta(const void *src_buf, unsigned long src_bufsize,
+          const void *trg_buf, unsigned long trg_bufsize,
+          unsigned long *delta_size, unsigned long max_delta_size)
+{
+       struct delta_index *index = create_delta_index(src_buf, src_bufsize);
+       if (index) {
+               void *delta = create_delta(index, trg_buf, trg_bufsize,
+                                          delta_size, max_delta_size);
+               free_delta_index(index);
+               return delta;
+       }
+       return NULL;
+}
+
+/*
+ * patch_delta: recreate target buffer given source buffer and delta data
+ *
+ * On success, a non-NULL pointer to the target buffer is returned and
+ * *trg_bufsize is updated with its size.  On failure a NULL pointer is
+ * returned.  The returned buffer must be freed by the caller.
+ */
+extern void *patch_delta(const void *src_buf, unsigned long src_size,
+                        const void *delta_buf, unsigned long delta_size,
                         unsigned long *dst_size);
 
 /* the smallest possible delta size is 4 bytes */
@@ -14,19 +77,20 @@ extern void *patch_delta(void *src_buf, unsigned long src_size,
 
 /*
  * This must be called twice on the delta data buffer, first to get the
- * expected reference buffer size, and again to get the result buffer size.
+ * expected source buffer size, and again to get the target buffer size.
  */
-static inline unsigned long get_delta_hdr_size(const unsigned char **datap)
+static inline unsigned long get_delta_hdr_size(const unsigned char **datap,
+                                              const unsigned char *top)
 {
        const unsigned char *data = *datap;
-       unsigned char cmd = *data++;
-       unsigned long size = cmd & ~0x80;
-       int i = 7;
-       while (cmd & 0x80) {
+       unsigned char cmd;
+       unsigned long size = 0;
+       int i = 0;
+       do {
                cmd = *data++;
                size |= (cmd & ~0x80) << i;
                i += 7;
-       }
+       } while (cmd & 0x80 && data < top);
        *datap = data;
        return size;
 }