1 /*
2 * Copyright 2018 The WebRTC Project Authors. All rights reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "rtc_base/strings/string_builder.h"
12
13 #include <stdarg.h>
14
15 #include <cstdio>
16 #include <cstring>
17
18 #include "absl/strings/string_view.h"
19 #include "rtc_base/checks.h"
20 #include "rtc_base/numerics/safe_minmax.h"
21
22 namespace rtc {
23
SimpleStringBuilder(rtc::ArrayView<char> buffer)24 SimpleStringBuilder::SimpleStringBuilder(rtc::ArrayView<char> buffer)
25 : buffer_(buffer) {
26 buffer_[0] = '\0';
27 RTC_DCHECK(IsConsistent());
28 }
29
operator <<(char ch)30 SimpleStringBuilder& SimpleStringBuilder::operator<<(char ch) {
31 return operator<<(absl::string_view(&ch, 1));
32 }
33
operator <<(absl::string_view str)34 SimpleStringBuilder& SimpleStringBuilder::operator<<(absl::string_view str) {
35 RTC_DCHECK_LT(size_ + str.length(), buffer_.size())
36 << "Buffer size was insufficient";
37 const size_t chars_added =
38 rtc::SafeMin(str.length(), buffer_.size() - size_ - 1);
39 memcpy(&buffer_[size_], str.data(), chars_added);
40 size_ += chars_added;
41 buffer_[size_] = '\0';
42 RTC_DCHECK(IsConsistent());
43 return *this;
44 }
45
46 // Numeric conversion routines.
47 //
48 // We use std::[v]snprintf instead of std::to_string because:
49 // * std::to_string relies on the current locale for formatting purposes,
50 // and therefore concurrent calls to std::to_string from multiple threads
51 // may result in partial serialization of calls
52 // * snprintf allows us to print the number directly into our buffer.
53 // * avoid allocating a std::string (potential heap alloc).
54 // TODO(tommi): Switch to std::to_chars in C++17.
55
operator <<(int i)56 SimpleStringBuilder& SimpleStringBuilder::operator<<(int i) {
57 return AppendFormat("%d", i);
58 }
59
operator <<(unsigned i)60 SimpleStringBuilder& SimpleStringBuilder::operator<<(unsigned i) {
61 return AppendFormat("%u", i);
62 }
63
operator <<(long i)64 SimpleStringBuilder& SimpleStringBuilder::operator<<(long i) { // NOLINT
65 return AppendFormat("%ld", i);
66 }
67
operator <<(long long i)68 SimpleStringBuilder& SimpleStringBuilder::operator<<(long long i) { // NOLINT
69 return AppendFormat("%lld", i);
70 }
71
operator <<(unsigned long i)72 SimpleStringBuilder& SimpleStringBuilder::operator<<(
73 unsigned long i) { // NOLINT
74 return AppendFormat("%lu", i);
75 }
76
operator <<(unsigned long long i)77 SimpleStringBuilder& SimpleStringBuilder::operator<<(
78 unsigned long long i) { // NOLINT
79 return AppendFormat("%llu", i);
80 }
81
operator <<(float f)82 SimpleStringBuilder& SimpleStringBuilder::operator<<(float f) {
83 return AppendFormat("%g", f);
84 }
85
operator <<(double f)86 SimpleStringBuilder& SimpleStringBuilder::operator<<(double f) {
87 return AppendFormat("%g", f);
88 }
89
operator <<(long double f)90 SimpleStringBuilder& SimpleStringBuilder::operator<<(long double f) {
91 return AppendFormat("%Lg", f);
92 }
93
AppendFormat(const char * fmt,...)94 SimpleStringBuilder& SimpleStringBuilder::AppendFormat(const char* fmt, ...) {
95 va_list args;
96 va_start(args, fmt);
97 const int len =
98 std::vsnprintf(&buffer_[size_], buffer_.size() - size_, fmt, args);
99 if (len >= 0) {
100 const size_t chars_added = rtc::SafeMin(len, buffer_.size() - 1 - size_);
101 size_ += chars_added;
102 RTC_DCHECK_EQ(len, chars_added) << "Buffer size was insufficient";
103 } else {
104 // This should never happen, but we're paranoid, so re-write the
105 // terminator in case vsnprintf() overwrote it.
106 RTC_DCHECK_NOTREACHED();
107 buffer_[size_] = '\0';
108 }
109 va_end(args);
110 RTC_DCHECK(IsConsistent());
111 return *this;
112 }
113
AppendFormat(const char * fmt,...)114 StringBuilder& StringBuilder::AppendFormat(const char* fmt, ...) {
115 va_list args, copy;
116 va_start(args, fmt);
117 va_copy(copy, args);
118 const int predicted_length = std::vsnprintf(nullptr, 0, fmt, copy);
119 va_end(copy);
120
121 RTC_DCHECK_GE(predicted_length, 0);
122 if (predicted_length > 0) {
123 const size_t size = str_.size();
124 str_.resize(size + predicted_length);
125 // Pass "+ 1" to vsnprintf to include space for the '\0'.
126 const int actual_length =
127 std::vsnprintf(&str_[size], predicted_length + 1, fmt, args);
128 RTC_DCHECK_GE(actual_length, 0);
129 }
130 va_end(args);
131 return *this;
132 }
133
134 } // namespace rtc
135