kakoune/src/diff.hh
Maxime Coste 388ada8142 Remove MirroredArray for diff implementation
We can index native arrays negatively, so just setup V1 and V2 to
point in the middle of the work arrays and remove the need for
creating MirroredArray.
2017-07-17 19:28:52 +09:00

168 lines
5.1 KiB
C++

#ifndef diff_hh_INCLUDED
#define diff_hh_INCLUDED
// Implementation of the linear space variant of the algorithm described in
// "An O(ND) Difference Algorithm and Its Variations"
// (http://xmailserver.org/diff2.pdf)
#include "array_view.hh"
#include "vector.hh"
#include <functional>
#include <iterator>
namespace Kakoune
{
struct Snake{ int x, y, u, v; bool add; };
template<typename Iterator, typename Equal>
Snake find_end_snake_of_further_reaching_dpath(Iterator a, int N, Iterator b, int M,
const int* V,
const int D, const int k, Equal eq)
{
const bool add = k == -D or (k != D and V[k-1] < V[k+1]);
// if diagonal on the right goes further along x than diagonal on the left,
// then we take a vertical edge from it to this diagonal, hence x = V[k+1]
// else, we take an horizontal edge from our left diagonal,x = V[k-1]+1
const int x = add ? V[k+1] : V[k-1]+1;
// we are by construction on diagonal k, so our position along b (y) is x - k.
const int y = x - k;
int u = x, v = y;
// follow end snake along diagonal k
while (u < N and v < M and eq(a[u], b[v]))
++u, ++v;
return { x, y, u, v, add };
}
struct SnakeLen : Snake
{
SnakeLen(Snake s, int d) : Snake(s), d(d) {}
int d;
};
template<typename Iterator, typename Equal>
SnakeLen find_middle_snake(Iterator a, int N, Iterator b, int M,
int* V1, int* V2, Equal eq)
{
const int delta = N - M;
V1[1] = 0;
V2[1] = 0;
std::reverse_iterator<Iterator> ra{a + N}, rb{b + M};
for (int D = 0; D <= (M + N + 1) / 2; ++D)
{
for (int k1 = -D; k1 <= D; k1 += 2)
{
auto p = find_end_snake_of_further_reaching_dpath(a, N, b, M, V1, D, k1, eq);
V1[k1] = p.u;
const int k2 = -(k1 - delta);
if ((delta % 2 != 0) and -(D-1) <= k2 and k2 <= (D-1))
{
if (V1[k1] + V2[k2] >= N)
return { p, 2 * D - 1 };// return last snake on forward path
}
}
for (int k2 = -D; k2 <= D; k2 += 2)
{
auto p = find_end_snake_of_further_reaching_dpath(ra, N, rb, M, V2, D, k2, eq);
V2[k2] = p.u;
const int k1 = -(k2 - delta);
if ((delta % 2 == 0) and -D <= k1 and k1 <= D)
{
if (V1[k1] + V2[k2] >= N)
return { { N - p.u, M - p.v, N - p.x , M - p.y, p.add } , 2 * D };// return last snake on reverse path
}
}
}
kak_assert(false);
return { {}, 0 };
}
struct Diff
{
enum { Keep, Add, Remove } mode;
int len;
int posB;
};
inline void append_diff(Vector<Diff>& diffs, Diff diff)
{
if (not diffs.empty() and diffs.back().mode == diff.mode
and (diff.mode != Diff::Add or
diffs.back().posB + diffs.back().len == diff.posB))
diffs.back().len += diff.len;
else
diffs.push_back(diff);
}
template<typename Iterator, typename Equal>
void find_diff_rec(Iterator a, int offA, int lenA,
Iterator b, int offB, int lenB,
int* V1, int* V2, Equal eq, Vector<Diff>& diffs)
{
if (lenA > 0 and lenB > 0)
{
auto middle_snake = find_middle_snake(a + offA, lenA, b + offB, lenB, V1, V2, eq);
kak_assert(middle_snake.u <= lenA and middle_snake.v <= lenB);
if (middle_snake.d > 1)
{
find_diff_rec(a, offA, middle_snake.x,
b, offB, middle_snake.y,
V1, V2, eq, diffs);
if (int len = middle_snake.u - middle_snake.x)
append_diff(diffs, {Diff::Keep, len, 0});
find_diff_rec(a, offA + middle_snake.u, lenA - middle_snake.u,
b, offB + middle_snake.v, lenB - middle_snake.v,
V1, V2, eq, diffs);
}
else
{
if (middle_snake.d == 1)
{
const int diag = middle_snake.x - (middle_snake.add ? 0 : 1);
if (diag != 0)
append_diff(diffs, {Diff::Keep, diag, 0});
if (middle_snake.add)
append_diff(diffs, {Diff::Add, 1, offB + diag});
else
append_diff(diffs, {Diff::Remove, 1, 0});
}
if (int len = middle_snake.u - middle_snake.x)
append_diff(diffs, {Diff::Keep, len, 0});
}
}
else if (lenB > 0)
append_diff(diffs, {Diff::Add, lenB, offB});
else if (lenA > 0)
append_diff(diffs, {Diff::Remove, lenA, 0});
}
template<typename Iterator, typename Equal = std::equal_to<typename std::iterator_traits<Iterator>::value_type>>
Vector<Diff> find_diff(Iterator a, int N, Iterator b, int M, Equal eq = Equal{})
{
const int max = 2 * (N + M) + 1;
Vector<int> data(2*max);
Vector<Diff> diffs;
find_diff_rec(a, 0, N, b, 0, M,
data.data() + (N+M), data.data() + max + (N+M),
eq, diffs);
return diffs;
}
}
#endif // diff_hh_INCLUDED