/*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2015 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
*/
#include <folly/String.h>
+
#include <folly/Format.h>
+#include <folly/ScopeGuard.h>
#include <cerrno>
#include <cstdarg>
namespace {
-inline void stringPrintfImpl(std::string& output, const char* format,
- va_list args) {
- // Tru to the space at the end of output for our output buffer.
- // Find out write point then inflate its size temporarily to its
- // capacity; we will later shrink it to the size needed to represent
- // the formatted string. If this buffer isn't large enough, we do a
- // resize and try again.
-
- const auto write_point = output.size();
- auto remaining = output.capacity() - write_point;
- output.resize(output.capacity());
-
+int stringAppendfImplHelper(char* buf,
+ size_t bufsize,
+ const char* format,
+ va_list args) {
va_list args_copy;
va_copy(args_copy, args);
- int bytes_used = vsnprintf(&output[write_point], remaining, format,
- args_copy);
+ int bytes_used = vsnprintf(buf, bufsize, format, args_copy);
va_end(args_copy);
+ return bytes_used;
+}
+
+void stringAppendfImpl(std::string& output, const char* format, va_list args) {
+ // Very simple; first, try to avoid an allocation by using an inline
+ // buffer. If that fails to hold the output string, allocate one on
+ // the heap, use it instead.
+ //
+ // It is hard to guess the proper size of this buffer; some
+ // heuristics could be based on the number of format characters, or
+ // static analysis of a codebase. Or, we can just pick a number
+ // that seems big enough for simple cases (say, one line of text on
+ // a terminal) without being large enough to be concerning as a
+ // stack variable.
+ std::array<char, 128> inline_buffer;
+
+ int bytes_used = stringAppendfImplHelper(
+ inline_buffer.data(), inline_buffer.size(), format, args);
if (bytes_used < 0) {
- throw std::runtime_error(
- to<std::string>("Invalid format string; snprintf returned negative "
- "with format string: ", format));
- } else if (bytes_used < remaining) {
- // There was enough room, just shrink and return.
- output.resize(write_point + bytes_used);
- } else {
- output.resize(write_point + bytes_used + 1);
- remaining = bytes_used + 1;
- va_list args_copy;
- va_copy(args_copy, args);
- bytes_used = vsnprintf(&output[write_point], remaining, format,
- args_copy);
- va_end(args_copy);
- if (bytes_used + 1 != remaining) {
- throw std::runtime_error(
- to<std::string>("vsnprint retry did not manage to work "
- "with format string: ", format));
- }
- output.resize(write_point + bytes_used);
+ throw std::runtime_error(to<std::string>(
+ "Invalid format string; snprintf returned negative "
+ "with format string: ",
+ format));
}
+
+ if (static_cast<size_t>(bytes_used) < inline_buffer.size()) {
+ output.append(inline_buffer.data(), bytes_used);
+ return;
+ }
+
+ // Couldn't fit. Heap allocate a buffer, oh well.
+ std::unique_ptr<char[]> heap_buffer(new char[bytes_used + 1]);
+ int final_bytes_used =
+ stringAppendfImplHelper(heap_buffer.get(), bytes_used + 1, format, args);
+ // The second call can take fewer bytes if, for example, we were printing a
+ // string buffer with null-terminating char using a width specifier -
+ // vsnprintf("%.*s", buf.size(), buf)
+ CHECK(bytes_used >= final_bytes_used);
+
+ // We don't keep the trailing '\0' in our output string
+ output.append(heap_buffer.get(), final_bytes_used);
}
-} // anon namespace
+} // anon namespace
std::string stringPrintf(const char* format, ...) {
- // snprintf will tell us how large the output buffer should be, but
- // we then have to call it a second time, which is costly. By
- // guestimating the final size, we avoid the double snprintf in many
- // cases, resulting in a performance win. We use this constructor
- // of std::string to avoid a double allocation, though it does pad
- // the resulting string with nul bytes. Our guestimation is twice
- // the format string size, or 32 bytes, whichever is larger. This
- // is a hueristic that doesn't affect correctness but attempts to be
- // reasonably fast for the most common cases.
- std::string ret(std::max(32UL, strlen(format) * 2), '\0');
- ret.resize(0);
-
va_list ap;
va_start(ap, format);
- stringPrintfImpl(ret, format, ap);
- va_end(ap);
+ SCOPE_EXIT {
+ va_end(ap);
+ };
+ return stringVPrintf(format, ap);
+}
+
+std::string stringVPrintf(const char* format, va_list ap) {
+ std::string ret;
+ stringAppendfImpl(ret, format, ap);
return ret;
}
std::string& stringAppendf(std::string* output, const char* format, ...) {
va_list ap;
va_start(ap, format);
- stringPrintfImpl(*output, format, ap);
- va_end(ap);
+ SCOPE_EXIT {
+ va_end(ap);
+ };
+ return stringVAppendf(output, format, ap);
+}
+
+std::string& stringVAppendf(std::string* output,
+ const char* format,
+ va_list ap) {
+ stringAppendfImpl(*output, format, ap);
return *output;
}
void stringPrintf(std::string* output, const char* format, ...) {
- output->clear();
va_list ap;
va_start(ap, format);
- stringPrintfImpl(*output, format, ap);
- va_end(ap);
+ SCOPE_EXIT {
+ va_end(ap);
+ };
+ return stringVPrintf(output, format, ap);
+}
+
+void stringVPrintf(std::string* output, const char* format, va_list ap) {
+ output->clear();
+ stringAppendfImpl(*output, format, ap);
};
namespace {
// https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/strerror_r.3.html
// http://www.kernel.org/doc/man-pages/online/pages/man3/strerror.3.html
-#if defined(__APPLE__) || defined(__FreeBSD__) || \
+#if defined(__APPLE__) || defined(__FreeBSD__) ||\
+ defined(__CYGWIN__) || defined(__ANDROID__) ||\
((_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) && !_GNU_SOURCE)
// Using XSI-compatible strerror_r
int r = strerror_r(err, buf, sizeof(buf));
return result;
}
-StringPiece skipWhitespace(StringPiece sp) {
- // Spaces other than ' ' characters are less common but should be
- // checked. This configuration where we loop on the ' '
- // separately from oddspaces was empirically fastest.
- auto oddspace = [] (char c) {
- return c == '\n' || c == '\t' || c == '\r';
- };
-
-loop:
- for (; !sp.empty() && sp.front() == ' '; sp.pop_front()) {
- }
- if (!sp.empty() && oddspace(sp.front())) {
- sp.pop_front();
- goto loop;
- }
-
- return sp;
-}
-
namespace {
void toLowerAscii8(char& c) {
n = std::min(n, length);
size_t offset = 0;
if (n != 0) {
+ n = std::min(4 - n, length);
do {
toLowerAscii8(str[offset]);
offset++;
n = (size_t)(str + offset);
n &= kAlignMask64;
- if ((n != 0) && (offset + 4 < length)) {
+ if ((n != 0) && (offset + 4 <= length)) {
// The next address is 32-bit aligned but not 64-bit aligned.
// Convert the next 4 bytes in order to get to the 64-bit aligned
// part of the input.
}
// Convert 8 characters at a time
- while (offset + 8 < length) {
+ while (offset + 8 <= length) {
toLowerAscii64(*(uint64_t*)(str + offset));
offset += 8;
}
// Convert 4 characters at a time
- while (offset + 4 < length) {
+ while (offset + 4 <= length) {
toLowerAscii32(*(uint32_t*)(str + offset));
offset += 4;
}
projects / folly.git / blobdiff