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. xdelta can express an edit that copies 20 * data inside of the destination which originally came from the 21 * source. We do not count that in the following routine, so we are 22 * undercounting the source material that remains in the final output 23 * that way. 24 */ 25int count_delta(void *delta_buf, unsigned long delta_size, 26 unsigned long *src_copied, unsigned long *literal_added) 27{ 28 unsigned long copied_from_source, added_literal; 29 const unsigned char *data, *top; 30 unsigned char cmd; 31 unsigned long src_size, dst_size, out; 32 33 if (delta_size < DELTA_SIZE_MIN) 34 return -1; 35 36 data = delta_buf; 37 top = delta_buf + delta_size; 38 39 src_size = get_delta_hdr_size(&data); 40 dst_size = get_delta_hdr_size(&data); 41 42 added_literal = copied_from_source = out = 0; 43 while (data < top) { 44 cmd = *data++; 45 if (cmd & 0x80) { 46 unsigned long cp_off = 0, cp_size = 0; 47 if (cmd & 0x01) cp_off = *data++; 48 if (cmd & 0x02) cp_off |= (*data++ << 8); 49 if (cmd & 0x04) cp_off |= (*data++ << 16); 50 if (cmd & 0x08) cp_off |= (*data++ << 24); 51 if (cmd & 0x10) cp_size = *data++; 52 if (cmd & 0x20) cp_size |= (*data++ << 8); 53 if (cmd & 0x40) cp_size |= (*data++ << 16); 54 if (cp_size == 0) cp_size = 0x10000; 55 56 copied_from_source += cp_size; 57 out += cp_size; 58 } else { 59 /* write literal into dst */ 60 added_literal += cmd; 61 out += cmd; 62 data += cmd; 63 } 64 } 65 66 /* sanity check */ 67 if (data != top || out != dst_size) 68 return -1; 69 70 /* delete size is what was _not_ copied from source. 71 * edit size is that and literal additions. 72 */ 73 *src_copied = copied_from_source; 74 *literal_added = added_literal; 75 return 0; 76}