1/* 2 * Copyright (C) 2005 Junio C Hamano 3 * The delta-parsing part is almost straight copy of patch-delta.c 4 * which is (C) 2005 Nicolas Pitre <nico@cam.org>. 5 */ 6#include <stdlib.h> 7#include <string.h> 8#include <limits.h> 9#include "delta.h" 10#include "count-delta.h" 11 12/* 13 * NOTE. We do not _interpret_ delta fully. As an approximation, we 14 * just count the number of bytes that are copied from the source, and 15 * the number of literal data bytes that are inserted. 16 * 17 * Number of bytes that are _not_ copied from the source is deletion, 18 * and number of inserted literal bytes are addition, so sum of them 19 * is the extent of damage. 20 */ 21int count_delta(void *delta_buf, unsigned long delta_size, 22 unsigned long *src_copied, unsigned long *literal_added) 23{ 24 unsigned long copied_from_source, added_literal; 25 const unsigned char *data, *top; 26 unsigned char cmd; 27 unsigned long src_size, dst_size, out; 28 29 if (delta_size < DELTA_SIZE_MIN) 30 return -1; 31 32 data = delta_buf; 33 top = delta_buf + delta_size; 34 35 src_size = get_delta_hdr_size(&data); 36 dst_size = get_delta_hdr_size(&data); 37 38 added_literal = copied_from_source = out = 0; 39 while (data < top) { 40 cmd = *data++; 41 if (cmd & 0x80) { 42 unsigned long cp_off = 0, cp_size = 0; 43 if (cmd & 0x01) cp_off = *data++; 44 if (cmd & 0x02) cp_off |= (*data++ << 8); 45 if (cmd & 0x04) cp_off |= (*data++ << 16); 46 if (cmd & 0x08) cp_off |= (*data++ << 24); 47 if (cmd & 0x10) cp_size = *data++; 48 if (cmd & 0x20) cp_size |= (*data++ << 8); 49 if (cmd & 0x40) cp_size |= (*data++ << 16); 50 if (cp_size == 0) cp_size = 0x10000; 51 52 copied_from_source += cp_size; 53 out += cp_size; 54 } else { 55 /* write literal into dst */ 56 added_literal += cmd; 57 out += cmd; 58 data += cmd; 59 } 60 } 61 62 /* sanity check */ 63 if (data != top || out != dst_size) 64 return -1; 65 66 /* delete size is what was _not_ copied from source. 67 * edit size is that and literal additions. 68 */ 69 *src_copied = copied_from_source; 70 *literal_added = added_literal; 71 return 0; 72}