c86e8568d8
The previous one wrongly coalesced a span with the next one even though the span being added does not reach it. Signed-off-by: Junio C Hamano <junkio@cox.net>
138 lines
2.8 KiB
C
138 lines
2.8 KiB
C
/*
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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 "cache.h"
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#include "delta.h"
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#include "count-delta.h"
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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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struct span {
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struct span *next;
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unsigned long ofs;
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unsigned long end;
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};
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static void touch_range(struct span **span,
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unsigned long ofs, unsigned long end)
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{
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struct span *e = *span;
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struct span *p = NULL;
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while (e && e->ofs <= ofs) {
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again:
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if (ofs < e->end) {
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while (e->end < end) {
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if (e->next && e->next->ofs <= end) {
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e->end = e->next->ofs;
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e = e->next;
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}
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else {
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e->end = end;
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return;
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}
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}
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return;
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}
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p = e;
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e = e->next;
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}
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if (e && e->ofs <= end) {
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e->ofs = ofs;
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goto again;
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}
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else {
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e = xmalloc(sizeof(*e));
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e->ofs = ofs;
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e->end = end;
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if (p) {
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e->next = p->next;
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p->next = e;
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}
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else {
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e->next = *span;
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*span = e;
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}
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}
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}
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static unsigned long count_range(struct span *s)
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{
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struct span *t;
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unsigned long sz = 0;
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while (s) {
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t = s;
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sz += s->end - s->ofs;
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s = s->next;
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free(t);
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}
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return sz;
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}
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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.
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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 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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struct span *span = NULL;
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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 = 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 (cmd & 0x40) cp_size |= (*data++ << 16);
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if (cp_size == 0) cp_size = 0x10000;
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touch_range(&span, cp_off, cp_off+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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*src_copied = count_range(span);
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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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*literal_added = added_literal;
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return 0;
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}
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