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79 lines
2.2 KiB
79 lines
2.2 KiB
/* |
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* Copyright (C) 2005 Junio C Hamano |
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* The delta-parsing part is almost straight copy of patch-delta.c |
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* which is (C) 2005 Nicolas Pitre <nico@cam.org>. |
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*/ |
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#include <stdlib.h> |
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#include <string.h> |
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#include <limits.h> |
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#include "delta.h" |
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#include "count-delta.h" |
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/* |
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* NOTE. We do not _interpret_ delta fully. As an approximation, we |
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* just count the number of bytes that are copied from the source, and |
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* the number of literal data bytes that are inserted. |
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* |
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* Number of bytes that are _not_ copied from the source is deletion, |
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* and number of inserted literal bytes are addition, so sum of them |
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* is the extent of damage. xdelta can express an edit that copies |
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* data inside of the destination which originally came from the |
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* source. We do not count that in the following routine, so we are |
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* undercounting the source material that remains in the final output |
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* that way. |
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*/ |
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int count_delta(void *delta_buf, unsigned long delta_size, |
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unsigned long *src_copied, unsigned long *literal_added) |
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{ |
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unsigned long copied_from_source, added_literal; |
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const unsigned char *data, *top; |
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unsigned char cmd; |
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unsigned long src_size, dst_size, out; |
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if (delta_size < DELTA_SIZE_MIN) |
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return -1; |
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data = delta_buf; |
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top = delta_buf + delta_size; |
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src_size = get_delta_hdr_size(&data); |
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dst_size = get_delta_hdr_size(&data); |
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added_literal = copied_from_source = out = 0; |
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while (data < top) { |
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cmd = *data++; |
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if (cmd & 0x80) { |
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unsigned long cp_off = 0, cp_size = 0; |
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if (cmd & 0x01) cp_off = *data++; |
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if (cmd & 0x02) cp_off |= (*data++ << 8); |
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if (cmd & 0x04) cp_off |= (*data++ << 16); |
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if (cmd & 0x08) cp_off |= (*data++ << 24); |
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if (cmd & 0x10) cp_size = *data++; |
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if (cmd & 0x20) cp_size |= (*data++ << 8); |
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if (cp_size == 0) cp_size = 0x10000; |
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if (cmd & 0x40) |
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/* copy from dst */ |
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; |
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else |
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copied_from_source += cp_size; |
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out += cp_size; |
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} else { |
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/* write literal into dst */ |
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added_literal += cmd; |
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out += cmd; |
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data += cmd; |
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} |
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} |
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/* sanity check */ |
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if (data != top || out != dst_size) |
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return -1; |
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/* delete size is what was _not_ copied from source. |
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* edit size is that and literal additions. |
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*/ |
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*src_copied = copied_from_source; |
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*literal_added = added_literal; |
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return 0; |
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}
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