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-rwxr-xr-xC/Delta.c62
1 files changed, 62 insertions, 0 deletions
diff --git a/C/Delta.c b/C/Delta.c
new file mode 100755
index 0000000..93c93a1
--- /dev/null
+++ b/C/Delta.c
@@ -0,0 +1,62 @@
+/* Delta.c -- Delta converter
+2009-05-26 : Igor Pavlov : Public domain */
+
+#include "Delta.h"
+
+void Delta_Init(Byte *state)
+{
+ unsigned i;
+ for (i = 0; i < DELTA_STATE_SIZE; i++)
+ state[i] = 0;
+}
+
+static void MyMemCpy(Byte *dest, const Byte *src, unsigned size)
+{
+ unsigned i;
+ for (i = 0; i < size; i++)
+ dest[i] = src[i];
+}
+
+void Delta_Encode(Byte *state, unsigned delta, Byte *data, SizeT size)
+{
+ Byte buf[DELTA_STATE_SIZE];
+ unsigned j = 0;
+ MyMemCpy(buf, state, delta);
+ {
+ SizeT i;
+ for (i = 0; i < size;)
+ {
+ for (j = 0; j < delta && i < size; i++, j++)
+ {
+ Byte b = data[i];
+ data[i] = (Byte)(b - buf[j]);
+ buf[j] = b;
+ }
+ }
+ }
+ if (j == delta)
+ j = 0;
+ MyMemCpy(state, buf + j, delta - j);
+ MyMemCpy(state + delta - j, buf, j);
+}
+
+void Delta_Decode(Byte *state, unsigned delta, Byte *data, SizeT size)
+{
+ Byte buf[DELTA_STATE_SIZE];
+ unsigned j = 0;
+ MyMemCpy(buf, state, delta);
+ {
+ SizeT i;
+ for (i = 0; i < size;)
+ {
+ for (j = 0; j < delta && i < size; i++, j++)
+ {
+ buf[j] = data[i] = (Byte)(buf[j] + data[i]);
+ }
+ }
+ }
+ if (j == delta)
+ j = 0;
+ MyMemCpy(state, buf + j, delta - j);
+ MyMemCpy(state + delta - j, buf, j);
+}