path: root/contrib/libs/hyperscan/src/nfa/accel_dfa_build_strat.cpp

/* 
 * Copyright (c) 2015-2017, Intel Corporation 
 * 
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 *    may be used to endorse or promote products derived from this software 
 *    without specific prior written permission. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
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#include "accel_dfa_build_strat.h" 
 
#include "accel.h" 
#include "grey.h" 
#include "nfagraph/ng_limex_accel.h" 
#include "shufticompile.h" 
#include "trufflecompile.h" 
#include "util/accel_scheme.h" 
#include "util/charreach.h" 
#include "util/container.h" 
#include "util/dump_charclass.h" 
#include "util/small_vector.h" 
#include "util/verify_types.h" 
 
#include <sstream> 
#include <unordered_map> 
#include <unordered_set> 
#include <vector> 
 
#define PATHS_LIMIT 500 
 
using namespace std; 
 
namespace ue2 { 
 
namespace { 
struct path { 
    small_vector<CharReach, MAX_ACCEL_DEPTH + 1> reach; 
    dstate_id_t dest = DEAD_STATE; 
    explicit path(dstate_id_t base) : dest(base) {} 
}; 
}; 
 
template<typename Container> 
void dump_paths(const Container &paths) { 
    for (UNUSED const path &p : paths) { 
        DEBUG_PRINTF("[%s] -> %u\n", describeClasses(p.reach).c_str(), p.dest); 
    } 
    DEBUG_PRINTF("%zu paths\n", paths.size()); 
} 
 
static 
vector<CharReach> reverse_alpha_remapping(const raw_dfa &rdfa) { 
    vector<CharReach> rv(rdfa.alpha_size - 1); /* TOP not required */ 
 
    for (u32 i = 0; i < N_CHARS; i++) { 
        rv.at(rdfa.alpha_remap[i]).set(i); 
    } 
 
    return rv; 
} 
 
static 
bool is_useful_path(const vector<path> &good, const path &p) { 
    for (const auto &g : good) { 
        assert(g.dest == p.dest); 
        assert(g.reach.size() <= p.reach.size()); 
        auto git = g.reach.rbegin(); 
        auto pit = p.reach.rbegin(); 
 
        for (; git != g.reach.rend(); ++git, ++pit) { 
            if (!pit->isSubsetOf(*git)) { 
                goto next; 
            } 
        } 
        DEBUG_PRINTF("better: [%s] -> %u\n", describeClasses(g.reach).c_str(), 
                     g.dest); 
 
        return false; 
    next:; 
    } 
 
    return true; 
} 
 
static 
path append(const path &orig, const CharReach &cr, u32 new_dest) { 
    path p(new_dest); 
    p.reach = orig.reach; 
    p.reach.push_back(cr); 
 
    return p; 
} 
 
static 
void extend(const raw_dfa &rdfa, const vector<CharReach> &rev_map, 
            const path &p, unordered_map<u32, vector<path>> &all, 
            vector<path> &out) { 
    const dstate &s = rdfa.states[p.dest]; 
 
    if (!p.reach.empty() && p.reach.back().none()) { 
        out.push_back(p); 
        return; 
    } 
 
    if (!s.reports.empty()) { 
        if (generates_callbacks(rdfa.kind)) { 
            out.push_back(p); 
            return; 
        } else { 
            path pp = append(p, CharReach(), p.dest); 
            all[p.dest].push_back(pp); 
            out.push_back(move(pp)); 
        } 
    } 
 
    if (!s.reports_eod.empty()) { 
        path pp = append(p, CharReach(), p.dest); 
        all[p.dest].push_back(pp); 
        out.push_back(move(pp)); 
    } 
 
    flat_map<u32, CharReach> dest; 
    for (u32 i = 0; i < rev_map.size(); i++) { 
        u32 succ = s.next[i]; 
        dest[succ] |= rev_map[i]; 
    } 
 
    for (const auto &e : dest) { 
        path pp = append(p, e.second, e.first); 
        if (!is_useful_path(all[e.first], pp)) { 
            DEBUG_PRINTF("not useful: [%s] -> %u\n", 
                         describeClasses(pp.reach).c_str(), pp.dest); 
            continue; 
        } 
 
        DEBUG_PRINTF("----good: [%s] -> %u\n", 
                     describeClasses(pp.reach).c_str(), pp.dest); 
        all[e.first].push_back(pp); 
        out.push_back(move(pp)); 
    } 
} 
 
static 
vector<vector<CharReach>> generate_paths(const raw_dfa &rdfa, 
                                         dstate_id_t base, u32 len) { 
    const vector<CharReach> rev_map = reverse_alpha_remapping(rdfa); 
    vector<path> paths{path(base)}; 
    unordered_map<u32, vector<path>> all; 
    all[base].push_back(path(base)); 
    for (u32 i = 0; i < len && paths.size() < PATHS_LIMIT; i++) { 
        vector<path> next_gen; 
        for (const auto &p : paths) { 
            extend(rdfa, rev_map, p, all, next_gen); 
        } 
 
        paths = move(next_gen); 
    } 
 
    dump_paths(paths); 
 
    vector<vector<CharReach>> rv; 
    rv.reserve(paths.size()); 
    for (auto &p : paths) { 
        rv.push_back(vector<CharReach>(std::make_move_iterator(p.reach.begin()), 
                                       std::make_move_iterator(p.reach.end()))); 
    } 
    return rv; 
} 
 
static 
AccelScheme look_for_offset_accel(const raw_dfa &rdfa, dstate_id_t base, 
                                  u32 max_allowed_accel_offset) { 
    DEBUG_PRINTF("looking for accel for %hu\n", base); 
    vector<vector<CharReach>> paths = 
        generate_paths(rdfa, base, max_allowed_accel_offset + 1); 
    AccelScheme as = findBestAccelScheme(paths, CharReach(), true); 
    DEBUG_PRINTF("found %s + %u\n", describeClass(as.cr).c_str(), as.offset); 
    return as; 
} 
 
static UNUSED 
bool better(const AccelScheme &a, const AccelScheme &b) { 
    if (!a.double_byte.empty() && b.double_byte.empty()) { 
        return true; 
    } 
 
    if (!b.double_byte.empty()) { 
        return false; 
    } 
 
    return a.cr.count() < b.cr.count(); 
} 
 
static 
bool double_byte_ok(const AccelScheme &info) { 
    return !info.double_byte.empty() && 
           info.double_cr.count() < info.double_byte.size() && 
           info.double_cr.count() <= 2;
} 
 
static 
bool has_self_loop(dstate_id_t s, const raw_dfa &raw) { 
    u16 top_remap = raw.alpha_remap[TOP]; 
    for (u32 i = 0; i < raw.states[s].next.size(); i++) { 
        if (i != top_remap && raw.states[s].next[i] == s) { 
            return true; 
        } 
    } 
    return false; 
} 
 
static 
flat_set<u16> find_nonexit_symbols(const raw_dfa &rdfa, 
                                   const CharReach &escape) { 
    flat_set<u16> rv; 
    CharReach nonexit = ~escape; 
    for (auto i = nonexit.find_first(); i != nonexit.npos; 
         i = nonexit.find_next(i)) { 
        rv.insert(rdfa.alpha_remap[i]); 
    } 
 
    return rv; 
} 
 
static 
dstate_id_t get_sds_or_proxy(const raw_dfa &raw) { 
    if (raw.start_floating != DEAD_STATE) { 
        DEBUG_PRINTF("has floating start\n"); 
        return raw.start_floating; 
    } 
 
    DEBUG_PRINTF("looking for SDS proxy\n"); 
 
    dstate_id_t s = raw.start_anchored; 
 
    if (has_self_loop(s, raw)) { 
        return s; 
    } 
 
    u16 top_remap = raw.alpha_remap[TOP]; 
 
    std::unordered_set<dstate_id_t> seen; 
    while (true) { 
        seen.insert(s); 
        DEBUG_PRINTF("basis %hu\n", s); 
 
        /* check if we are connected to a state with a self loop */ 
        for (u32 i = 0; i < raw.states[s].next.size(); i++) { 
            dstate_id_t t = raw.states[s].next[i]; 
            if (i != top_remap && t != DEAD_STATE && has_self_loop(t, raw)) { 
                return t; 
            } 
        } 
 
        /* find a neighbour to use as a basis for looking for the sds proxy */ 
        dstate_id_t t = DEAD_STATE; 
        for (u32 i = 0; i < raw.states[s].next.size(); i++) { 
            dstate_id_t tt = raw.states[s].next[i]; 
            if (i != top_remap && tt != DEAD_STATE && !contains(seen, tt)) { 
                t = tt; 
                break; 
            } 
        } 
 
        if (t == DEAD_STATE) { 
            /* we were unable to find a state to use as a SDS proxy */ 
            return DEAD_STATE; 
        } 
 
        s = t; 
    } 
} 
 
static 
set<dstate_id_t> find_region(const raw_dfa &rdfa, dstate_id_t base, 
                             const AccelScheme &ei) { 
    DEBUG_PRINTF("looking for region around %hu\n", base); 
 
    set<dstate_id_t> region = {base}; 
 
    if (!ei.double_byte.empty()) { 
        return region; 
    } 
 
    DEBUG_PRINTF("accel %s+%u\n", describeClass(ei.cr).c_str(), ei.offset); 
 
    const CharReach &escape = ei.cr; 
    auto nonexit_symbols = find_nonexit_symbols(rdfa, escape); 
 
    vector<dstate_id_t> pending = {base}; 
    while (!pending.empty()) { 
        dstate_id_t curr = pending.back(); 
        pending.pop_back(); 
        for (auto s : nonexit_symbols) { 
            dstate_id_t t = rdfa.states[curr].next[s]; 
            if (contains(region, t)) { 
                continue; 
            } 
 
            DEBUG_PRINTF("    %hu is in region\n", t); 
            region.insert(t); 
            pending.push_back(t); 
        } 
    } 
 
    return region; 
} 
 
AccelScheme 
accel_dfa_build_strat::find_escape_strings(dstate_id_t this_idx) const { 
    AccelScheme rv; 
    const raw_dfa &rdfa = get_raw(); 
    rv.cr.clear(); 
    rv.offset = 0; 
    const dstate &raw = rdfa.states[this_idx]; 
    const vector<CharReach> rev_map = reverse_alpha_remapping(rdfa); 
    bool outs2_broken = false; 
    flat_map<dstate_id_t, CharReach> succs; 
 
    for (u32 i = 0; i < rev_map.size(); i++) { 
        if (raw.next[i] == this_idx) { 
            continue; 
        } 
 
        const CharReach &cr_i = rev_map.at(i); 
 
        rv.cr |= cr_i; 
        dstate_id_t next_id = raw.next[i]; 
 
        DEBUG_PRINTF("next is %hu\n", next_id); 
        const dstate &raw_next = rdfa.states[next_id]; 
 
        if (outs2_broken) { 
            continue; 
        } 
 
        if (!raw_next.reports.empty() && generates_callbacks(rdfa.kind)) { 
            DEBUG_PRINTF("leads to report\n"); 
            outs2_broken = true; /* cannot accelerate over reports */ 
            continue; 
        } 
        succs[next_id] |= cr_i; 
    } 
 
    if (!outs2_broken) { 
        for (const auto &e : succs) { 
            const CharReach &cr_i = e.second; 
            const dstate &raw_next = rdfa.states[e.first]; 
 
            CharReach cr_all_j; 
            for (u32 j = 0; j < rev_map.size(); j++) { 
                if (raw_next.next[j] == raw.next[j]) { 
                    continue; 
                } 
 
                DEBUG_PRINTF("state %hu: adding sym %u -> %hu to 2 \n", e.first, 
                             j, raw_next.next[j]); 
                cr_all_j |= rev_map.at(j); 
            } 
 
            if (cr_i.count() * cr_all_j.count() > 8) { 
                DEBUG_PRINTF("adding %zu to double_cr\n", cr_i.count()); 
                rv.double_cr |= cr_i; 
            } else { 
                for (auto ii = cr_i.find_first(); ii != CharReach::npos; 
                     ii = cr_i.find_next(ii)) { 
                    for (auto jj = cr_all_j.find_first(); jj != CharReach::npos; 
                         jj = cr_all_j.find_next(jj)) { 
                        rv.double_byte.emplace((u8)ii, (u8)jj); 
                        if (rv.double_byte.size() > 8) { 
                            DEBUG_PRINTF("outs2 too big\n"); 
                            outs2_broken = true; 
                            goto done; 
                        } 
                    } 
                } 
            } 
        } 
 
    done: 
        assert(outs2_broken || rv.double_byte.size() <= 8); 
        if (outs2_broken) { 
            rv.double_byte.clear(); 
        } 
    } 
 
    DEBUG_PRINTF("this %u, sds proxy %hu\n", this_idx, get_sds_or_proxy(rdfa)); 
    DEBUG_PRINTF("broken %d\n", outs2_broken); 
    if (!double_byte_ok(rv) && !is_triggered(rdfa.kind) && 
        this_idx == rdfa.start_floating && this_idx != DEAD_STATE) { 
        DEBUG_PRINTF("looking for offset accel at %u\n", this_idx); 
        auto offset = 
            look_for_offset_accel(rdfa, this_idx, max_allowed_offset_accel()); 
        DEBUG_PRINTF("width %zu vs %zu\n", offset.cr.count(), rv.cr.count()); 
        if (double_byte_ok(offset) || offset.cr.count() < rv.cr.count()) { 
            DEBUG_PRINTF("using offset accel\n"); 
            rv = offset; 
        } 
    } 
 
    return rv; 
} 
 
void 
accel_dfa_build_strat::buildAccel(UNUSED dstate_id_t this_idx, 
                                  const AccelScheme &info, 
                                  void *accel_out) { 
    AccelAux *accel = (AccelAux *)accel_out; 
 
    DEBUG_PRINTF("accelerations scheme has offset s%u/d%u\n", info.offset, 
                 info.double_offset); 
    accel->generic.offset = verify_u8(info.offset); 
 
    if (double_byte_ok(info) && info.double_cr.none() && 
        info.double_byte.size() == 1) { 
        accel->accel_type = ACCEL_DVERM; 
        accel->dverm.c1 = info.double_byte.begin()->first; 
        accel->dverm.c2 = info.double_byte.begin()->second; 
        accel->dverm.offset = verify_u8(info.double_offset); 
        DEBUG_PRINTF("state %hu is double vermicelli\n", this_idx); 
        return; 
    } 
 
    if (double_byte_ok(info) && info.double_cr.none() && 
        (info.double_byte.size() == 2 || info.double_byte.size() == 4)) { 
        bool ok = true; 
 
        assert(!info.double_byte.empty()); 
        u8 firstC = info.double_byte.begin()->first & CASE_CLEAR; 
        u8 secondC = info.double_byte.begin()->second & CASE_CLEAR; 
 
        for (const pair<u8, u8> &p : info.double_byte) { 
            if ((p.first & CASE_CLEAR) != firstC || 
                (p.second & CASE_CLEAR) != secondC) { 
                ok = false; 
                break; 
            } 
        } 
 
        if (ok) { 
            accel->accel_type = ACCEL_DVERM_NOCASE; 
            accel->dverm.c1 = firstC; 
            accel->dverm.c2 = secondC; 
            accel->dverm.offset = verify_u8(info.double_offset); 
            DEBUG_PRINTF("state %hu is nc double vermicelli\n", this_idx); 
            return; 
        } 
 
        u8 m1; 
        u8 m2; 
        if (buildDvermMask(info.double_byte, &m1, &m2)) { 
            accel->accel_type = ACCEL_DVERM_MASKED; 
            accel->dverm.offset = verify_u8(info.double_offset); 
            accel->dverm.c1 = info.double_byte.begin()->first & m1; 
            accel->dverm.c2 = info.double_byte.begin()->second & m2; 
            accel->dverm.m1 = m1; 
            accel->dverm.m2 = m2; 
            DEBUG_PRINTF( 
                "building maskeddouble-vermicelli for 0x%02hhx%02hhx\n", 
                accel->dverm.c1, accel->dverm.c2); 
            return; 
        } 
    } 
 
    if (double_byte_ok(info) && 
        shuftiBuildDoubleMasks( 
            info.double_cr, info.double_byte, (u8 *)&accel->dshufti.lo1, 
            (u8 *)&accel->dshufti.hi1, (u8 *)&accel->dshufti.lo2, 
            (u8 *)&accel->dshufti.hi2)) { 
        accel->accel_type = ACCEL_DSHUFTI; 
        accel->dshufti.offset = verify_u8(info.double_offset); 
        DEBUG_PRINTF("state %hu is double shufti\n", this_idx); 
        return; 
    } 
 
    if (info.cr.none()) { 
        accel->accel_type = ACCEL_RED_TAPE; 
        DEBUG_PRINTF("state %hu is a dead end full of bureaucratic red tape" 
                     " from which there is no escape\n", 
                     this_idx); 
        return; 
    } 
 
    if (info.cr.count() == 1) { 
        accel->accel_type = ACCEL_VERM; 
        accel->verm.c = info.cr.find_first(); 
        DEBUG_PRINTF("state %hu is vermicelli\n", this_idx); 
        return; 
    } 
 
    if (info.cr.count() == 2 && info.cr.isCaselessChar()) { 
        accel->accel_type = ACCEL_VERM_NOCASE; 
        accel->verm.c = info.cr.find_first() & CASE_CLEAR; 
        DEBUG_PRINTF("state %hu is caseless vermicelli\n", this_idx); 
        return; 
    } 
 
    if (info.cr.count() > max_floating_stop_char()) { 
        accel->accel_type = ACCEL_NONE; 
        DEBUG_PRINTF("state %hu is too broad\n", this_idx); 
        return; 
    } 
 
    accel->accel_type = ACCEL_SHUFTI; 
    if (-1 != shuftiBuildMasks(info.cr, (u8 *)&accel->shufti.lo, 
                               (u8 *)&accel->shufti.hi)) { 
        DEBUG_PRINTF("state %hu is shufti\n", this_idx); 
        return; 
    } 
 
    assert(!info.cr.none()); 
    accel->accel_type = ACCEL_TRUFFLE; 
    truffleBuildMasks(info.cr, (u8 *)&accel->truffle.mask1, 
                      (u8 *)&accel->truffle.mask2); 
    DEBUG_PRINTF("state %hu is truffle\n", this_idx); 
} 
 
map<dstate_id_t, AccelScheme> 
accel_dfa_build_strat::getAccelInfo(const Grey &grey) { 
    map<dstate_id_t, AccelScheme> rv; 
    raw_dfa &rdfa = get_raw(); 
    if (!grey.accelerateDFA) { 
        return rv; 
    } 
 
    dstate_id_t sds_proxy = get_sds_or_proxy(rdfa); 
    DEBUG_PRINTF("sds %hu\n", sds_proxy); 
 
    /* Find accel info for a single state. */ 
    auto do_state = [&](size_t i) { 
        if (i == DEAD_STATE) { 
            return; 
        } 
 
        /* Note on report acceleration states: While we can't accelerate while 
         * we are spamming out callbacks, the QR code paths don't raise reports 
         * during scanning so they can accelerate report states. */ 
        if (generates_callbacks(rdfa.kind) && !rdfa.states[i].reports.empty()) { 
            return; 
        } 
 
        size_t single_limit = 
            i == sds_proxy ? max_floating_stop_char() : max_stop_char(); 
        DEBUG_PRINTF("inspecting %zu/%hu: %zu\n", i, sds_proxy, single_limit); 
 
        AccelScheme ei = find_escape_strings(i); 
        if (ei.cr.count() > single_limit) { 
            DEBUG_PRINTF("state %zu is not accelerable has %zu\n", i, 
                         ei.cr.count()); 
            return; 
        } 
 
        DEBUG_PRINTF("state %zu should be accelerable %zu\n", i, ei.cr.count()); 
 
        rv[i] = ei; 
    }; 
 
    if (only_accel_init) { 
        DEBUG_PRINTF("only computing accel for init states\n"); 
        do_state(rdfa.start_anchored); 
        if (rdfa.start_floating != rdfa.start_anchored) { 
            do_state(rdfa.start_floating); 
        } 
    } else { 
        DEBUG_PRINTF("computing accel for all states\n"); 
        for (size_t i = 0; i < rdfa.states.size(); i++) { 
            do_state(i); 
        } 
    } 
 
    /* provide acceleration states to states in the region of sds */ 
    if (contains(rv, sds_proxy)) { 
        AccelScheme sds_ei = rv[sds_proxy]; 
        sds_ei.double_byte.clear(); /* region based on single byte scheme 
                                     * may differ from double byte */ 
        DEBUG_PRINTF("looking to expand offset accel to nearby states, %zu\n", 
                     sds_ei.cr.count()); 
        auto sds_region = find_region(rdfa, sds_proxy, sds_ei); 
        for (auto s : sds_region) { 
            if (!contains(rv, s) || better(sds_ei, rv[s])) { 
                rv[s] = sds_ei; 
            } 
        } 
    } 
 
    return rv; 
} 
};