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authorGravatar misterg <misterg@google.com>2017-09-19 16:54:40 -0400
committerGravatar misterg <misterg@google.com>2017-09-19 16:54:40 -0400
commitc2e754829628d1e9b7a16b3389cfdace76950fdf (patch)
tree5a7f056f44e27c30e10025113b644f0b3b5801fc /absl/strings/internal/char_map.h
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+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Character Map Class
+//
+// A fast, bit-vector map for 8-bit unsigned characters.
+// This class is useful for non-character purposes as well.
+
+#ifndef ABSL_STRINGS_INTERNAL_CHAR_MAP_H_
+#define ABSL_STRINGS_INTERNAL_CHAR_MAP_H_
+
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+
+#include "absl/base/macros.h"
+#include "absl/base/port.h"
+
+namespace absl {
+namespace strings_internal {
+
+class Charmap {
+ public:
+ constexpr Charmap() : m_() {}
+
+ // Initializes with a given char*. Note that NUL is not treated as
+ // a terminator, but rather a char to be flicked.
+ Charmap(const char* str, int len) : m_() {
+ while (len--) SetChar(*str++);
+ }
+
+ // Initializes with a given char*. NUL is treated as a terminator
+ // and will not be in the charmap.
+ explicit Charmap(const char* str) : m_() {
+ while (*str) SetChar(*str++);
+ }
+
+ constexpr bool contains(unsigned char c) const {
+ return (m_[c / 64] >> (c % 64)) & 0x1;
+ }
+
+ // Returns true if and only if a character exists in both maps.
+ bool IntersectsWith(const Charmap& c) const {
+ for (size_t i = 0; i < ABSL_ARRAYSIZE(m_); ++i) {
+ if ((m_[i] & c.m_[i]) != 0) return true;
+ }
+ return false;
+ }
+
+ bool IsZero() const {
+ for (uint64_t c : m_) {
+ if (c != 0) return false;
+ }
+ return true;
+ }
+
+ // Containing only a single specified char.
+ static constexpr Charmap Char(char x) {
+ return Charmap(CharMaskForWord(x, 0), CharMaskForWord(x, 1),
+ CharMaskForWord(x, 2), CharMaskForWord(x, 3));
+ }
+
+ // Containing all the chars in the C-std::string 's'.
+ // Note that this is expensively recursive because of the C++11 constexpr
+ // formulation. Use only in constexpr initializers.
+ static constexpr Charmap FromString(const char* s) {
+ return *s == 0 ? Charmap() : (Char(*s) | FromString(s + 1));
+ }
+
+ // Containing all the chars in the closed interval [lo,hi].
+ static constexpr Charmap Range(char lo, char hi) {
+ return Charmap(RangeForWord(lo, hi, 0), RangeForWord(lo, hi, 1),
+ RangeForWord(lo, hi, 2), RangeForWord(lo, hi, 3));
+ }
+
+ friend constexpr Charmap operator&(const Charmap& a, const Charmap& b) {
+ return Charmap(a.m_[0] & b.m_[0], a.m_[1] & b.m_[1], a.m_[2] & b.m_[2],
+ a.m_[3] & b.m_[3]);
+ }
+
+ friend constexpr Charmap operator|(const Charmap& a, const Charmap& b) {
+ return Charmap(a.m_[0] | b.m_[0], a.m_[1] | b.m_[1], a.m_[2] | b.m_[2],
+ a.m_[3] | b.m_[3]);
+ }
+
+ friend constexpr Charmap operator~(const Charmap& a) {
+ return Charmap(~a.m_[0], ~a.m_[1], ~a.m_[2], ~a.m_[3]);
+ }
+
+ private:
+ constexpr Charmap(uint64_t b0, uint64_t b1, uint64_t b2, uint64_t b3)
+ : m_{b0, b1, b2, b3} {}
+
+ static constexpr uint64_t RangeForWord(unsigned char lo, unsigned char hi,
+ uint64_t word) {
+ return OpenRangeFromZeroForWord(hi + 1, word) &
+ ~OpenRangeFromZeroForWord(lo, word);
+ }
+
+ // All the chars in the specified word of the range [0, upper).
+ static constexpr uint64_t OpenRangeFromZeroForWord(uint64_t upper,
+ uint64_t word) {
+ return (upper <= 64 * word)
+ ? 0
+ : (upper >= 64 * (word + 1))
+ ? ~static_cast<uint64_t>(0)
+ : (~static_cast<uint64_t>(0) >> (64 - upper % 64));
+ }
+
+ static constexpr uint64_t CharMaskForWord(unsigned char x, uint64_t word) {
+ return (x / 64 == word) ? (static_cast<uint64_t>(1) << (x % 64)) : 0;
+ }
+
+ private:
+ void SetChar(unsigned char c) {
+ m_[c / 64] |= static_cast<uint64_t>(1) << (c % 64);
+ }
+
+ uint64_t m_[4];
+};
+
+// Mirror the char-classifying predicates in <cctype>
+constexpr Charmap UpperCharmap() { return Charmap::Range('A', 'Z'); }
+constexpr Charmap LowerCharmap() { return Charmap::Range('a', 'z'); }
+constexpr Charmap DigitCharmap() { return Charmap::Range('0', '9'); }
+constexpr Charmap AlphaCharmap() { return LowerCharmap() | UpperCharmap(); }
+constexpr Charmap AlnumCharmap() { return DigitCharmap() | AlphaCharmap(); }
+constexpr Charmap XDigitCharmap() {
+ return DigitCharmap() | Charmap::Range('A', 'F') | Charmap::Range('a', 'f');
+}
+constexpr Charmap PrintCharmap() { return Charmap::Range(0x20, 0x7e); }
+constexpr Charmap SpaceCharmap() { return Charmap::FromString("\t\n\v\f\r "); }
+constexpr Charmap CntrlCharmap() {
+ return Charmap::Range(0, 0x7f) & ~PrintCharmap();
+}
+constexpr Charmap BlankCharmap() { return Charmap::FromString("\t "); }
+constexpr Charmap GraphCharmap() { return PrintCharmap() & ~SpaceCharmap(); }
+constexpr Charmap PunctCharmap() { return GraphCharmap() & ~AlnumCharmap(); }
+
+} // namespace strings_internal
+} // namespace absl
+
+#endif // ABSL_STRINGS_INTERNAL_CHAR_MAP_H_