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// Copyright 2020 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_STRINGS_STRING_UTIL_INTERNAL_H_
#define BASE_STRINGS_STRING_UTIL_INTERNAL_H_
#include <algorithm>
#include "polyfills/base/logging.h"
#include "polyfills/base/notreached.h"
#include "base/ranges/algorithm.h"
#include "base/strings/string_piece.h"
#include "base/third_party/icu/icu_utf.h"
namespace gurl_base {
namespace internal {
// Used by ReplaceStringPlaceholders to track the position in the string of
// replaced parameters.
struct ReplacementOffset {
ReplacementOffset(uintptr_t parameter, size_t offset)
: parameter(parameter), offset(offset) {}
// Index of the parameter.
uintptr_t parameter;
// Starting position in the string.
size_t offset;
};
static bool CompareParameter(const ReplacementOffset& elem1,
const ReplacementOffset& elem2) {
return elem1.parameter < elem2.parameter;
}
// Assuming that a pointer is the size of a "machine word", then
// uintptr_t is an integer type that is also a machine word.
using MachineWord = uintptr_t;
inline bool IsMachineWordAligned(const void* pointer) {
return !(reinterpret_cast<MachineWord>(pointer) & (sizeof(MachineWord) - 1));
}
template <typename T, typename CharT = typename T::value_type>
std::basic_string<CharT> ToLowerASCIIImpl(T str) {
std::basic_string<CharT> ret;
ret.reserve(str.size());
for (size_t i = 0; i < str.size(); i++)
ret.push_back(ToLowerASCII(str[i]));
return ret;
}
template <typename T, typename CharT = typename T::value_type>
std::basic_string<CharT> ToUpperASCIIImpl(T str) {
std::basic_string<CharT> ret;
ret.reserve(str.size());
for (size_t i = 0; i < str.size(); i++)
ret.push_back(ToUpperASCII(str[i]));
return ret;
}
template <typename T, typename CharT = typename T::value_type>
int CompareCaseInsensitiveASCIIT(T a, T b) {
// Find the first characters that aren't equal and compare them. If the end
// of one of the strings is found before a nonequal character, the lengths
// of the strings are compared.
size_t i = 0;
while (i < a.length() && i < b.length()) {
CharT lower_a = ToLowerASCII(a[i]);
CharT lower_b = ToLowerASCII(b[i]);
if (lower_a < lower_b)
return -1;
if (lower_a > lower_b)
return 1;
i++;
}
// End of one string hit before finding a different character. Expect the
// common case to be "strings equal" at this point so check that first.
if (a.length() == b.length())
return 0;
if (a.length() < b.length())
return -1;
return 1;
}
template <typename T, typename CharT = typename T::value_type>
TrimPositions TrimStringT(T input,
T trim_chars,
TrimPositions positions,
std::basic_string<CharT>* output) {
// Find the edges of leading/trailing whitespace as desired. Need to use
// a StringPiece version of input to be able to call find* on it with the
// StringPiece version of trim_chars (normally the trim_chars will be a
// constant so avoid making a copy).
const size_t last_char = input.length() - 1;
const size_t first_good_char =
(positions & TRIM_LEADING) ? input.find_first_not_of(trim_chars) : 0;
const size_t last_good_char = (positions & TRIM_TRAILING)
? input.find_last_not_of(trim_chars)
: last_char;
// When the string was all trimmed, report that we stripped off characters
// from whichever position the caller was interested in. For empty input, we
// stripped no characters, but we still need to clear |output|.
if (input.empty() || first_good_char == std::basic_string<CharT>::npos ||
last_good_char == std::basic_string<CharT>::npos) {
bool input_was_empty = input.empty(); // in case output == &input
output->clear();
return input_was_empty ? TRIM_NONE : positions;
}
// Trim.
output->assign(input.data() + first_good_char,
last_good_char - first_good_char + 1);
// Return where we trimmed from.
return static_cast<TrimPositions>(
(first_good_char == 0 ? TRIM_NONE : TRIM_LEADING) |
(last_good_char == last_char ? TRIM_NONE : TRIM_TRAILING));
}
template <typename T, typename CharT = typename T::value_type>
T TrimStringPieceT(T input, T trim_chars, TrimPositions positions) {
size_t begin =
(positions & TRIM_LEADING) ? input.find_first_not_of(trim_chars) : 0;
size_t end = (positions & TRIM_TRAILING)
? input.find_last_not_of(trim_chars) + 1
: input.size();
return input.substr(std::min(begin, input.size()), end - begin);
}
template <typename T, typename CharT = typename T::value_type>
std::basic_string<CharT> CollapseWhitespaceT(
T text,
bool trim_sequences_with_line_breaks) {
std::basic_string<CharT> result;
result.resize(text.size());
// Set flags to pretend we're already in a trimmed whitespace sequence, so we
// will trim any leading whitespace.
bool in_whitespace = true;
bool already_trimmed = true;
int chars_written = 0;
for (auto c : text) {
if (IsUnicodeWhitespace(c)) {
if (!in_whitespace) {
// Reduce all whitespace sequences to a single space.
in_whitespace = true;
result[chars_written++] = L' ';
}
if (trim_sequences_with_line_breaks && !already_trimmed &&
((c == '\n') || (c == '\r'))) {
// Whitespace sequences containing CR or LF are eliminated entirely.
already_trimmed = true;
--chars_written;
}
} else {
// Non-whitespace characters are copied straight across.
in_whitespace = false;
already_trimmed = false;
result[chars_written++] = c;
}
}
if (in_whitespace && !already_trimmed) {
// Any trailing whitespace is eliminated.
--chars_written;
}
result.resize(chars_written);
return result;
}
template <class Char>
bool DoIsStringASCII(const Char* characters, size_t length) {
// Bitmasks to detect non ASCII characters for character sizes of 8, 16 and 32
// bits.
constexpr MachineWord NonASCIIMasks[] = {
0, MachineWord(0x8080808080808080ULL), MachineWord(0xFF80FF80FF80FF80ULL),
0, MachineWord(0xFFFFFF80FFFFFF80ULL),
};
if (!length)
return true;
constexpr MachineWord non_ascii_bit_mask = NonASCIIMasks[sizeof(Char)];
static_assert(non_ascii_bit_mask, "Error: Invalid Mask");
MachineWord all_char_bits = 0;
const Char* end = characters + length;
// Prologue: align the input.
while (!IsMachineWordAligned(characters) && characters < end)
all_char_bits |= *characters++;
if (all_char_bits & non_ascii_bit_mask)
return false;
// Compare the values of CPU word size.
constexpr size_t chars_per_word = sizeof(MachineWord) / sizeof(Char);
constexpr int batch_count = 16;
while (characters <= end - batch_count * chars_per_word) {
all_char_bits = 0;
for (int i = 0; i < batch_count; ++i) {
all_char_bits |= *(reinterpret_cast<const MachineWord*>(characters));
characters += chars_per_word;
}
if (all_char_bits & non_ascii_bit_mask)
return false;
}
// Process the remaining words.
all_char_bits = 0;
while (characters <= end - chars_per_word) {
all_char_bits |= *(reinterpret_cast<const MachineWord*>(characters));
characters += chars_per_word;
}
// Process the remaining bytes.
while (characters < end)
all_char_bits |= *characters++;
return !(all_char_bits & non_ascii_bit_mask);
}
template <bool (*Validator)(uint32_t)>
inline bool DoIsStringUTF8(StringPiece str) {
const char* src = str.data();
int32_t src_len = static_cast<int32_t>(str.length());
int32_t char_index = 0;
while (char_index < src_len) {
int32_t code_point;
CBU8_NEXT(src, char_index, src_len, code_point);
if (!Validator(code_point))
return false;
}
return true;
}
// Implementation note: Normally this function will be called with a hardcoded
// constant for the lowercase_ascii parameter. Constructing a StringPiece from
// a C constant requires running strlen, so the result will be two passes
// through the buffers, one to file the length of lowercase_ascii, and one to
// compare each letter.
//
// This function could have taken a const char* to avoid this and only do one
// pass through the string. But the strlen is faster than the case-insensitive
// compares and lets us early-exit in the case that the strings are different
// lengths (will often be the case for non-matches). So whether one approach or
// the other will be faster depends on the case.
//
// The hardcoded strings are typically very short so it doesn't matter, and the
// string piece gives additional flexibility for the caller (doesn't have to be
// null terminated) so we choose the StringPiece route.
template <typename T, typename CharT = typename T::value_type>
inline bool DoLowerCaseEqualsASCII(T str, StringPiece lowercase_ascii) {
return std::equal(
str.begin(), str.end(), lowercase_ascii.begin(), lowercase_ascii.end(),
[](auto lhs, auto rhs) { return ToLowerASCII(lhs) == rhs; });
}
template <typename T, typename CharT = typename T::value_type>
bool StartsWithT(T str, T search_for, CompareCase case_sensitivity) {
if (search_for.size() > str.size())
return false;
BasicStringPiece<CharT> source = str.substr(0, search_for.size());
switch (case_sensitivity) {
case CompareCase::SENSITIVE:
return source == search_for;
case CompareCase::INSENSITIVE_ASCII:
return std::equal(search_for.begin(), search_for.end(), source.begin(),
CaseInsensitiveCompareASCII<CharT>());
default:
GURL_NOTREACHED();
return false;
}
}
template <typename T, typename CharT = typename T::value_type>
bool EndsWithT(T str, T search_for, CompareCase case_sensitivity) {
if (search_for.size() > str.size())
return false;
BasicStringPiece<CharT> source =
str.substr(str.size() - search_for.size(), search_for.size());
switch (case_sensitivity) {
case CompareCase::SENSITIVE:
return source == search_for;
case CompareCase::INSENSITIVE_ASCII:
return std::equal(source.begin(), source.end(), search_for.begin(),
CaseInsensitiveCompareASCII<CharT>());
default:
GURL_NOTREACHED();
return false;
}
}
// A Matcher for DoReplaceMatchesAfterOffset() that matches substrings.
template <class CharT>
struct SubstringMatcher {
BasicStringPiece<CharT> find_this;
size_t Find(const std::basic_string<CharT>& input, size_t pos) {
return input.find(find_this.data(), pos, find_this.length());
}
size_t MatchSize() { return find_this.length(); }
};
// Type deduction helper for SubstringMatcher.
template <typename T, typename CharT = typename T::value_type>
auto MakeSubstringMatcher(T find_this) {
return SubstringMatcher<CharT>{find_this};
}
// A Matcher for DoReplaceMatchesAfterOffset() that matches single characters.
template <class CharT>
struct CharacterMatcher {
BasicStringPiece<CharT> find_any_of_these;
size_t Find(const std::basic_string<CharT>& input, size_t pos) {
return input.find_first_of(find_any_of_these.data(), pos,
find_any_of_these.length());
}
constexpr size_t MatchSize() { return 1; }
};
// Type deduction helper for CharacterMatcher.
template <typename T, typename CharT = typename T::value_type>
auto MakeCharacterMatcher(T find_any_of_these) {
return CharacterMatcher<CharT>{find_any_of_these};
}
enum class ReplaceType { REPLACE_ALL, REPLACE_FIRST };
// Runs in O(n) time in the length of |str|, and transforms the string without
// reallocating when possible. Returns |true| if any matches were found.
//
// This is parameterized on a |Matcher| traits type, so that it can be the
// implementation for both ReplaceChars() and ReplaceSubstringsAfterOffset().
template <typename Matcher, typename T, typename CharT = typename T::value_type>
bool DoReplaceMatchesAfterOffset(std::basic_string<CharT>* str,
size_t initial_offset,
Matcher matcher,
T replace_with,
ReplaceType replace_type) {
using CharTraits = std::char_traits<CharT>;
const size_t find_length = matcher.MatchSize();
if (!find_length)
return false;
// If the find string doesn't appear, there's nothing to do.
size_t first_match = matcher.Find(*str, initial_offset);
if (first_match == std::basic_string<CharT>::npos)
return false;
// If we're only replacing one instance, there's no need to do anything
// complicated.
const size_t replace_length = replace_with.length();
if (replace_type == ReplaceType::REPLACE_FIRST) {
str->replace(first_match, find_length, replace_with.data(), replace_length);
return true;
}
// If the find and replace strings are the same length, we can simply use
// replace() on each instance, and finish the entire operation in O(n) time.
if (find_length == replace_length) {
auto* buffer = &((*str)[0]);
for (size_t offset = first_match; offset != std::basic_string<CharT>::npos;
offset = matcher.Find(*str, offset + replace_length)) {
CharTraits::copy(buffer + offset, replace_with.data(), replace_length);
}
return true;
}
// Since the find and replace strings aren't the same length, a loop like the
// one above would be O(n^2) in the worst case, as replace() will shift the
// entire remaining string each time. We need to be more clever to keep things
// O(n).
//
// When the string is being shortened, it's possible to just shift the matches
// down in one pass while finding, and truncate the length at the end of the
// search.
//
// If the string is being lengthened, more work is required. The strategy used
// here is to make two find() passes through the string. The first pass counts
// the number of matches to determine the new size. The second pass will
// either construct the new string into a new buffer (if the existing buffer
// lacked capacity), or else -- if there is room -- create a region of scratch
// space after |first_match| by shifting the tail of the string to a higher
// index, and doing in-place moves from the tail to lower indices thereafter.
size_t str_length = str->length();
size_t expansion = 0;
if (replace_length > find_length) {
// This operation lengthens the string; determine the new length by counting
// matches.
const size_t expansion_per_match = (replace_length - find_length);
size_t num_matches = 0;
for (size_t match = first_match; match != std::basic_string<CharT>::npos;
match = matcher.Find(*str, match + find_length)) {
expansion += expansion_per_match;
++num_matches;
}
const size_t final_length = str_length + expansion;
if (str->capacity() < final_length) {
// If we'd have to allocate a new buffer to grow the string, build the
// result directly into the new allocation via append().
std::basic_string<CharT> src(str->get_allocator());
str->swap(src);
str->reserve(final_length);
size_t pos = 0;
for (size_t match = first_match;; match = matcher.Find(src, pos)) {
str->append(src, pos, match - pos);
str->append(replace_with.data(), replace_length);
pos = match + find_length;
// A mid-loop test/break enables skipping the final Find() call; the
// number of matches is known, so don't search past the last one.
if (!--num_matches)
break;
}
// Handle substring after the final match.
str->append(src, pos, str_length - pos);
return true;
}
// Prepare for the copy/move loop below -- expand the string to its final
// size by shifting the data after the first match to the end of the resized
// string.
size_t shift_src = first_match + find_length;
size_t shift_dst = shift_src + expansion;
// Big |expansion| factors (relative to |str_length|) require padding up to
// |shift_dst|.
if (shift_dst > str_length)
str->resize(shift_dst);
str->replace(shift_dst, str_length - shift_src, *str, shift_src,
str_length - shift_src);
str_length = final_length;
}
// We can alternate replacement and move operations. This won't overwrite the
// unsearched region of the string so long as |write_offset| <= |read_offset|;
// that condition is always satisfied because:
//
// (a) If the string is being shortened, |expansion| is zero and
// |write_offset| grows slower than |read_offset|.
//
// (b) If the string is being lengthened, |write_offset| grows faster than
// |read_offset|, but |expansion| is big enough so that |write_offset|
// will only catch up to |read_offset| at the point of the last match.
auto* buffer = &((*str)[0]);
size_t write_offset = first_match;
size_t read_offset = first_match + expansion;
do {
if (replace_length) {
CharTraits::copy(buffer + write_offset, replace_with.data(),
replace_length);
write_offset += replace_length;
}
read_offset += find_length;
// min() clamps std::basic_string<CharT>::npos (the largest unsigned value)
// to str_length.
size_t match = std::min(matcher.Find(*str, read_offset), str_length);
size_t length = match - read_offset;
if (length) {
CharTraits::move(buffer + write_offset, buffer + read_offset, length);
write_offset += length;
read_offset += length;
}
} while (read_offset < str_length);
// If we're shortening the string, truncate it now.
str->resize(write_offset);
return true;
}
template <typename T, typename CharT = typename T::value_type>
bool ReplaceCharsT(T input,
T find_any_of_these,
T replace_with,
std::basic_string<CharT>* output) {
// Commonly, this is called with output and input being the same string; in
// that case, skip the copy.
if (input.data() != output->data() || input.size() != output->size())
output->assign(input.data(), input.size());
return DoReplaceMatchesAfterOffset(output, 0,
MakeCharacterMatcher(find_any_of_these),
replace_with, ReplaceType::REPLACE_ALL);
}
template <class string_type>
inline typename string_type::value_type* WriteIntoT(string_type* str,
size_t length_with_null) {
GURL_DCHECK_GE(length_with_null, 1u);
str->reserve(length_with_null);
str->resize(length_with_null - 1);
return &((*str)[0]);
}
// Generic version for all JoinString overloads. |list_type| must be a sequence
// (gurl_base::span or std::initializer_list) of strings/StringPieces (std::string,
// std::u16string, StringPiece or StringPiece16). |CharT| is either char or
// char16_t.
template <typename list_type,
typename T,
typename CharT = typename T::value_type>
static std::basic_string<CharT> JoinStringT(list_type parts, T sep) {
if (gurl_base::empty(parts))
return std::basic_string<CharT>();
// Pre-allocate the eventual size of the string. Start with the size of all of
// the separators (note that this *assumes* parts.size() > 0).
size_t total_size = (parts.size() - 1) * sep.size();
for (const auto& part : parts)
total_size += part.size();
std::basic_string<CharT> result;
result.reserve(total_size);
auto iter = parts.begin();
GURL_DCHECK(iter != parts.end());
result.append(iter->data(), iter->size());
++iter;
for (; iter != parts.end(); ++iter) {
result.append(sep.data(), sep.size());
result.append(iter->data(), iter->size());
}
// Sanity-check that we pre-allocated correctly.
GURL_DCHECK_EQ(total_size, result.size());
return result;
}
template <typename T, typename CharT = typename T::value_type>
std::basic_string<CharT> DoReplaceStringPlaceholders(
T format_string,
const std::vector<std::basic_string<CharT>>& subst,
std::vector<size_t>* offsets) {
size_t substitutions = subst.size();
GURL_DCHECK_LT(substitutions, 10U);
size_t sub_length = 0;
for (const auto& cur : subst)
sub_length += cur.length();
std::basic_string<CharT> formatted;
formatted.reserve(format_string.length() + sub_length);
std::vector<ReplacementOffset> r_offsets;
for (auto i = format_string.begin(); i != format_string.end(); ++i) {
if ('$' == *i) {
if (i + 1 != format_string.end()) {
++i;
if ('$' == *i) {
while (i != format_string.end() && '$' == *i) {
formatted.push_back('$');
++i;
}
--i;
} else {
if (*i < '1' || *i > '9') {
GURL_DLOG(ERROR) << "Invalid placeholder: $" << *i;
continue;
}
uintptr_t index = *i - '1';
if (offsets) {
ReplacementOffset r_offset(index,
static_cast<int>(formatted.size()));
r_offsets.insert(
ranges::upper_bound(r_offsets, r_offset, &CompareParameter),
r_offset);
}
if (index < substitutions)
formatted.append(subst.at(index));
}
}
} else {
formatted.push_back(*i);
}
}
if (offsets) {
for (const auto& cur : r_offsets)
offsets->push_back(cur.offset);
}
return formatted;
}
// The following code is compatible with the OpenBSD lcpy interface. See:
// http://www.gratisoft.us/todd/papers/strlcpy.html
// ftp://ftp.openbsd.org/pub/OpenBSD/src/lib/libc/string/{wcs,str}lcpy.c
template <typename CHAR>
size_t lcpyT(CHAR* dst, const CHAR* src, size_t dst_size) {
for (size_t i = 0; i < dst_size; ++i) {
if ((dst[i] = src[i]) == 0) // We hit and copied the terminating NULL.
return i;
}
// We were left off at dst_size. We over copied 1 byte. Null terminate.
if (dst_size != 0)
dst[dst_size - 1] = 0;
// Count the rest of the |src|, and return it's length in characters.
while (src[dst_size])
++dst_size;
return dst_size;
}
} // namespace internal
} // namespace base
#endif // BASE_STRINGS_STRING_UTIL_INTERNAL_H_