/*

* Copyright (c) Facebook, Inc. and its affiliates.

*

* This source code is licensed under the MIT license found in the

* LICENSE file in the root directory of this source tree.

*/

#include "hermes/Support/SNPrintfBuf.h"

#include <algorithm>

#include <cassert>

#include <cstdarg>

#include <cstdio>

#include <cstring>

namespace hermes {

SNPrintfBuf::SNPrintfBuf(int initSize)

: curSize_(initSize),

buf_(new char[initSize]),

bufPtr_(&buf_[0]),

remaining_(initSize) {}

void SNPrintfBuf::printf(const char *fmt, ...) {

assert(buf_.get() && "Buffer has been released");

va_list vl;

va_start(vl, fmt);

// If the first vsnprintf fails, we need a second copy for the post-realloc

// call. Unfortunately, we must create it before we know whether we need it.

va_list dup_vl;

va_copy(dup_vl, vl);

int res = vsnprintf(bufPtr_, remaining_, fmt, vl);

if (res >= remaining_) {

realloc(res);

res = vsnprintf(bufPtr_, remaining_, fmt, dup_vl);

assert(res < remaining_ && "True by construction.");

}

remaining_ -= res;

bufPtr_ += res;

va_end(vl);

va_end(dup_vl);

}

void SNPrintfBuf::realloc(int minSize) {

assert(minSize >= remaining_ && "precondition");

// We add one to minSize for the terminating null, which is not included.

int newSize = std::max(minSize + 1, 2 * curSize_);

std::unique_ptr<char[]> newBuf(new char[newSize]);

// This will be the number of characters written, not counting terminating

// null.

int curUsed = curSize_ - remaining_;

// Copy the characters, including the terminating null.

std::memcpy(newBuf.get(), buf_.get(), curUsed + 1);

// Update the state variables.

curSize_ = newSize;

remaining_ = curSize_ - curUsed;

buf_ = std::move(newBuf);

bufPtr_ = buf_.get() + curUsed;

}

} // namespace hermes