// 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.
#include "absl/strings/str_cat.h"
#include <assert.h>
#include <algorithm>
#include <cstdint>
#include <cstring>
#include "absl/strings/ascii.h"
#include "absl/strings/internal/resize_uninitialized.h"
namespace absl {
AlphaNum::AlphaNum(Hex hex) {
char* const end = &digits_[numbers_internal::kFastToBufferSize];
char* writer = end;
uint64_t value = hex.value;
static const char hexdigits[] = "0123456789abcdef";
do {
*--writer = hexdigits[value & 0xF];
value >>= 4;
} while (value != 0);
char* beg;
if (end - writer < hex.width) {
beg = end - hex.width;
std::fill_n(beg, writer - beg, hex.fill);
} else {
beg = writer;
}
piece_ = absl::string_view(beg, end - beg);
}
AlphaNum::AlphaNum(Dec dec) {
assert(dec.width <= numbers_internal::kFastToBufferSize);
char* const end = &digits_[numbers_internal::kFastToBufferSize];
char* const minfill = end - dec.width;
char* writer = end;
uint64_t value = dec.value;
bool neg = dec.neg;
while (value > 9) {
*--writer = '0' + (value % 10);
value /= 10;
}
*--writer = '0' + value;
if (neg) *--writer = '-';
ptrdiff_t fillers = writer - minfill;
if (fillers > 0) {
// Tricky: if the fill character is ' ', then it's <fill><+/-><digits>
// But...: if the fill character is '0', then it's <+/-><fill><digits>
bool add_sign_again = false;
if (neg && dec.fill == '0') { // If filling with '0',
++writer; // ignore the sign we just added
add_sign_again = true; // and re-add the sign later.
}
writer -= fillers;
std::fill_n(writer, fillers, dec.fill);
if (add_sign_again) *--writer = '-';
}
piece_ = absl::string_view(writer, end - writer);
}
// ----------------------------------------------------------------------
// StrCat()
// This merges the given strings or integers, with no delimiter. This
// is designed to be the fastest possible way to construct a std::string out
// of a mix of raw C strings, StringPieces, strings, and integer values.
// ----------------------------------------------------------------------
// Append is merely a version of memcpy that returns the address of the byte
// after the area just overwritten.
static char* Append(char* out, const AlphaNum& x) {
// memcpy is allowed to overwrite arbitrary memory, so doing this after the
// call would force an extra fetch of x.size().
char* after = out + x.size();
memcpy(out, x.data(), x.size());
return after;
}
std::string StrCat(const AlphaNum& a, const AlphaNum& b) {
std::string result;
absl::strings_internal::STLStringResizeUninitialized(&result,
a.size() + b.size());
char* const begin = &*result.begin();
char* out = begin;
out = Append(out, a);
out = Append(out, b);
assert(out == begin + result.size());
return result;
}
std::string StrCat(const AlphaNum& a, const AlphaNum& b, const AlphaNum& c) {
std::string result;
strings_internal::STLStringResizeUninitialized(
&result, a.size() + b.size() + c.size());
char* const begin = &*result.begin();
char* out = begin;
out = Append(out, a);
out = Append(out, b);
out = Append(out, c);
assert(out == begin + result.size());
return result;
}
std::string StrCat(const AlphaNum& a, const AlphaNum& b, const AlphaNum& c,
const AlphaNum& d) {
std::string result;
strings_internal::STLStringResizeUninitialized(
&result, a.size() + b.size() + c.size() + d.size());
char* const begin = &*result.begin();
char* out = begin;
out = Append(out, a);
out = Append(out, b);
out = Append(out, c);
out = Append(out, d);
assert(out == begin + result.size());
return result;
}
namespace strings_internal {
// Do not call directly - these are not part of the public API.
std::string CatPieces(std::initializer_list<absl::string_view> pieces) {
std::string result;
size_t total_size = 0;
for (const absl::string_view piece : pieces) total_size += piece.size();
strings_internal::STLStringResizeUninitialized(&result, total_size);
char* const begin = &*result.begin();
char* out = begin;
for (const absl::string_view piece : pieces) {
const size_t this_size = piece.size();
memcpy(out, piece.data(), this_size);
out += this_size;
}
assert(out == begin + result.size());
return result;
}
// It's possible to call StrAppend with an absl::string_view that is itself a
// fragment of the std::string we're appending to. However the results of this are
// random. Therefore, check for this in debug mode. Use unsigned math so we
// only have to do one comparison. Note, there's an exception case: appending an
// empty std::string is always allowed.
#define ASSERT_NO_OVERLAP(dest, src) \
assert(((src).size() == 0) || \
(uintptr_t((src).data() - (dest).data()) > uintptr_t((dest).size())))
void AppendPieces(std::string* dest,
std::initializer_list<absl::string_view> pieces) {
size_t old_size = dest->size();
size_t total_size = old_size;
for (const absl::string_view piece : pieces) {
ASSERT_NO_OVERLAP(*dest, piece);
total_size += piece.size();
}
strings_internal::STLStringResizeUninitialized(dest, total_size);
char* const begin = &*dest->begin();
char* out = begin + old_size;
for (const absl::string_view piece : pieces) {
const size_t this_size = piece.size();
memcpy(out, piece.data(), this_size);
out += this_size;
}
assert(out == begin + dest->size());
}
} // namespace strings_internal
void StrAppend(std::string* dest, const AlphaNum& a) {
ASSERT_NO_OVERLAP(*dest, a);
dest->append(a.data(), a.size());
}
void StrAppend(std::string* dest, const AlphaNum& a, const AlphaNum& b) {
ASSERT_NO_OVERLAP(*dest, a);
ASSERT_NO_OVERLAP(*dest, b);
std::string::size_type old_size = dest->size();
strings_internal::STLStringResizeUninitialized(
dest, old_size + a.size() + b.size());
char* const begin = &*dest->begin();
char* out = begin + old_size;
out = Append(out, a);
out = Append(out, b);
assert(out == begin + dest->size());
}
void StrAppend(std::string* dest, const AlphaNum& a, const AlphaNum& b,
const AlphaNum& c) {
ASSERT_NO_OVERLAP(*dest, a);
ASSERT_NO_OVERLAP(*dest, b);
ASSERT_NO_OVERLAP(*dest, c);
std::string::size_type old_size = dest->size();
strings_internal::STLStringResizeUninitialized(
dest, old_size + a.size() + b.size() + c.size());
char* const begin = &*dest->begin();
char* out = begin + old_size;
out = Append(out, a);
out = Append(out, b);
out = Append(out, c);
assert(out == begin + dest->size());
}
void StrAppend(std::string* dest, const AlphaNum& a, const AlphaNum& b,
const AlphaNum& c, const AlphaNum& d) {
ASSERT_NO_OVERLAP(*dest, a);
ASSERT_NO_OVERLAP(*dest, b);
ASSERT_NO_OVERLAP(*dest, c);
ASSERT_NO_OVERLAP(*dest, d);
std::string::size_type old_size = dest->size();
strings_internal::STLStringResizeUninitialized(
dest, old_size + a.size() + b.size() + c.size() + d.size());
char* const begin = &*dest->begin();
char* out = begin + old_size;
out = Append(out, a);
out = Append(out, b);
out = Append(out, c);
out = Append(out, d);
assert(out == begin + dest->size());
}
} // namespace absl
