intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 154 insertions, 0 deletions

diff --git a/library/cpp/yson_pull/detail/cescape_decode.h b/library/cpp/yson_pull/detail/cescape_decode.h
new file mode 100644
index 00000000000..2ee5dd95007
--- /dev/null
+++ b/library/cpp/yson_pull/detail/cescape_decode.h
@@ -0,0 +1,154 @@
+#pragma once
+
+#include <util/system/types.h>
+
+#include <algorithm>
+#include <cstring>
+
+namespace NYsonPull {
+    namespace NDetail {
+        namespace NCEscape {
+            namespace NImpl {
+                inline ui8 as_digit(ui8 c) {
+                    return c - ui8{'0'};
+                }
+
+                inline ui8 as_hexdigit(ui8 c) {
+                    static constexpr ui8 hex_decode_map[256] = {
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255,
+                        255, 255, 255, 255, 255, 10, 11, 12, 13, 14, 15, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+                        255, 255, 255, 255};
+
+                    return hex_decode_map[c];
+                }
+
+                inline const ui8* read_oct(ui8& result, const ui8* p, ui8 n) {
+                    auto digit = ui8{0};
+                    while (n-- && (digit = as_digit(*p)) < 8) {
+                        result = result * 8 + digit;
+                        ++p;
+                    }
+                    return p;
+                }
+
+                inline const ui8* read_hex(ui8& result, const ui8* p, ui8 n) {
+                    auto digit = ui8{0};
+                    while (n-- && (digit = as_hexdigit(*p)) < 16) {
+                        result = result * 16 + digit;
+                        ++p;
+                    }
+                    return p;
+                }
+
+                inline const ui8* unescape_char_and_advance(
+                    ui8& result,
+                    const ui8* p,
+                    const ui8* end) {
+                    switch (*p) {
+                        default:
+                            result = *p;
+                            ++p;
+                            break;
+                        case 'b':
+                            result = '\b';
+                            ++p;
+                            break;
+                        case 'f':
+                            result = '\f';
+                            ++p;
+                            break;
+                        case 'n':
+                            result = '\n';
+                            ++p;
+                            break;
+                        case 'r':
+                            result = '\r';
+                            ++p;
+                            break;
+                        case 't':
+                            result = '\t';
+                            ++p;
+                            break;
+
+                        case 'x': {
+                            ++p;
+                            result = 0;
+                            auto* next = read_hex(
+                                result,
+                                p, std::min<ptrdiff_t>(2, end - p));
+                            if (next > p) {
+                                p = next;
+                            } else {
+                                result = 'x';
+                            }
+                        } break;
+
+                        case '0':
+                        case '1':
+                        case '2':
+                        case '3':
+                            result = 0;
+                            p = read_oct(
+                                result,
+                                p, std::min<ptrdiff_t>(3, end - p));
+                            break;
+
+                        case '4':
+                        case '5':
+                        case '6':
+                        case '7':
+                            result = 0;
+                            p = read_oct(
+                                result,
+                                p, std::min<ptrdiff_t>(2, end - p));
+                            break;
+                    }
+                    return p;
+                }
+
+                template <typename T, typename U>
+                inline void unescape_impl(
+                    const ui8* p,
+                    const ui8* end,
+                    T&& consume_one,
+                    U&& consume_span) {
+                    while (p < end) {
+                        auto* escaped = static_cast<const ui8*>(
+                            ::memchr(p, '\\', end - p));
+                        if (escaped == nullptr) {
+                            consume_span(p, end - p);
+                            return;
+                        } else {
+                            consume_span(p, escaped - p);
+                            auto c = ui8{'\\'};
+                            p = escaped + 1;
+                            if (p < end) {
+                                p = unescape_char_and_advance(c, p, end);
+                            }
+                            consume_one(c);
+                        }
+                    }
+                }
+            }
+        }     // namespace NCEscape
+    }         // namespace NDetail
+}