static int scanA(struct histindex *index, int line1, int count1)
{
unsigned int ptr, tbl_idx;
unsigned int chain_len;
struct record **rec_chain, *rec;
for (ptr = LINE_END(1); line1 <= ptr; ptr--) {
tbl_idx = TABLE_HASH(index, 1, ptr);
rec_chain = index->records + tbl_idx;
rec = *rec_chain;
chain_len = 0;
while (rec) {
if (CMP(index, 1, rec->ptr, 1, ptr)) {
/*
* ptr is identical to another element. Insert
* it onto the front of the existing element
* chain.
*/
NEXT_PTR(index, ptr) = rec->ptr;
rec->ptr = ptr;
/* cap rec->cnt at MAX_CNT */
rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
LINE_MAP(index, ptr) = rec;
goto continue_scan;
}
rec = rec->next;
chain_len++;
}
if (chain_len == index->max_chain_length)
return -1;
/*
* This is the first time we have ever seen this particular
* element in the sequence. Construct a new chain for it.
*/
if (!(rec = xdl_cha_alloc(&index->rcha)))
return -1;
rec->ptr = ptr;
rec->cnt = 1;
rec->next = *rec_chain;
*rec_chain = rec;
LINE_MAP(index, ptr) = rec;
continue_scan:
; /* no op */
}
return 0;
}
static int find_lcs(struct histindex *index, struct region *lcs,
int line1, int count1, int line2, int count2) {
int b_ptr;
if (scanA(index, line1, count1))
return -1;
index->cnt = index->max_chain_length + 1;
for (b_ptr = line2; b_ptr <= LINE_END(2); )
b_ptr = try_lcs(index, lcs, b_ptr, line1, count1, line2, count2);
return index->has_common && index->max_chain_length < index->cnt;
}
static int find_lcs(xpparam_t const *xpp, xdfenv_t *env,
struct region *lcs,
int line1, int count1, int line2, int count2)
{
int b_ptr;
int sz, ret = -1;
struct histindex index;
memset(&index, 0, sizeof(index));
index.env = env;
index.xpp = xpp;
index.records = NULL;
index.line_map = NULL;
/* in case of early xdl_cha_free() */
index.rcha.head = NULL;
index.table_bits = xdl_hashbits(count1);
sz = index.records_size = 1 << index.table_bits;
sz *= sizeof(struct record *);
if (!(index.records = (struct record **) xdl_malloc(sz)))
goto cleanup;
memset(index.records, 0, sz);
sz = index.line_map_size = count1;
sz *= sizeof(struct record *);
if (!(index.line_map = (struct record **) xdl_malloc(sz)))
goto cleanup;
memset(index.line_map, 0, sz);
sz = index.line_map_size;
sz *= sizeof(unsigned int);
if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
goto cleanup;
memset(index.next_ptrs, 0, sz);
/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
goto cleanup;
index.ptr_shift = line1;
index.max_chain_length = 64;
if (scanA(&index, line1, count1))
goto cleanup;
index.cnt = index.max_chain_length + 1;
for (b_ptr = line2; b_ptr <= LINE_END(2); )
b_ptr = try_lcs(&index, lcs, b_ptr, line1, count1, line2, count2);
if (index.has_common && index.max_chain_length < index.cnt)
ret = 1;
else
ret = 0;
cleanup:
free_index(&index);
return ret;
}
static int try_lcs(struct histindex *index, struct region *lcs, int b_ptr,
int line1, int count1, int line2, int count2)
{
unsigned int b_next = b_ptr + 1;
struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
unsigned int as, ae, bs, be, np, rc;
int should_break;
for (; rec; rec = rec->next) {
if (rec->cnt > index->cnt) {
if (!index->has_common)
index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
continue;
}
as = rec->ptr;
if (!CMP(index, 1, as, 2, b_ptr))
continue;
index->has_common = 1;
for (;;) {
should_break = 0;
np = NEXT_PTR(index, as);
bs = b_ptr;
ae = as;
be = bs;
rc = rec->cnt;
while (line1 < (int)as && line2 < (int)bs
&& CMP(index, 1, as - 1, 2, bs - 1)) {
as--;
bs--;
if (1 < rc)
rc = XDL_MIN(rc, CNT(index, as));
}
while ((int)ae < LINE_END(1) && (int)be < LINE_END(2)
&& CMP(index, 1, ae + 1, 2, be + 1)) {
ae++;
be++;
if (1 < rc)
rc = XDL_MIN(rc, CNT(index, ae));
}
if (b_next <= be)
b_next = be + 1;
if (lcs->end1 - lcs->begin1 < ae - as || rc < index->cnt) {
lcs->begin1 = as;
lcs->begin2 = bs;
lcs->end1 = ae;
lcs->end2 = be;
index->cnt = rc;
}
if (np == 0)
break;
while (np <= ae) {
np = NEXT_PTR(index, np);
if (np == 0) {
should_break = 1;
break;
}
}
if (should_break)
break;
as = np;
}
}
return b_next;
}
static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env,
int line1, int count1, int line2, int count2)
{
struct histindex index;
struct region lcs;
int sz;
int result = -1;
if (count1 <= 0 && count2 <= 0)
return 0;
if (LINE_END(1) >= MAX_PTR)
return -1;
if (!count1) {
while(count2--)
env->xdf2.rchg[line2++ - 1] = 1;
return 0;
} else if (!count2) {
while(count1--)
env->xdf1.rchg[line1++ - 1] = 1;
return 0;
}
memset(&index, 0, sizeof(index));
index.env = env;
index.xpp = xpp;
index.records = NULL;
index.line_map = NULL;
/* in case of early xdl_cha_free() */
index.rcha.head = NULL;
index.table_bits = xdl_hashbits(count1);
sz = index.records_size = 1 << index.table_bits;
sz *= sizeof(struct record *);
if (!(index.records = (struct record **) xdl_malloc(sz)))
goto cleanup;
memset(index.records, 0, sz);
sz = index.line_map_size = count1;
sz *= sizeof(struct record *);
if (!(index.line_map = (struct record **) xdl_malloc(sz)))
goto cleanup;
memset(index.line_map, 0, sz);
sz = index.line_map_size;
sz *= sizeof(unsigned int);
if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
goto cleanup;
memset(index.next_ptrs, 0, sz);
/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
goto cleanup;
index.ptr_shift = line1;
index.max_chain_length = 64;
memset(&lcs, 0, sizeof(lcs));
if (find_lcs(&index, &lcs, line1, count1, line2, count2))
result = fall_back_to_classic_diff(&index, line1, count1, line2, count2);
else {
if (lcs.begin1 == 0 && lcs.begin2 == 0) {
while (count1--)
env->xdf1.rchg[line1++ - 1] = 1;
while (count2--)
env->xdf2.rchg[line2++ - 1] = 1;
result = 0;
} else {
result = histogram_diff(xpp, env,
line1, lcs.begin1 - line1,
line2, lcs.begin2 - line2);
if (result)
goto cleanup;
result = histogram_diff(xpp, env,
lcs.end1 + 1, LINE_END(1) - lcs.end1,
lcs.end2 + 1, LINE_END(2) - lcs.end2);
if (result)
goto cleanup;
}
}
cleanup:
xdl_free(index.records);
xdl_free(index.line_map);
xdl_free(index.next_ptrs);
xdl_cha_free(&index.rcha);
return result;
}
