// This file is originally from Trantor - MsgBuffer.cc

// Copyright (c) 2016-2021, Tao An.  All rights reserved.

// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
//   * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//   * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//   * Neither the name of Tao An nor the names of other contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "msg_buffer.h"

#include <string.h>
#include "core/math/math.h"
#ifndef _WIN32
#include <netinet/in.h>
#include <sys/uio.h>
#else
#include <WindowsSupport.h>
#include <winsock2.h>
#endif
#include <assert.h>
#include <errno.h>

static constexpr size_t kBufferOffset{ 8 };

MsgBuffer::MsgBuffer(size_t len) :
		head_(kBufferOffset), initCap_(len), buffer_(len + head_), tail_(head_) {
}

void MsgBuffer::ensureWritableBytes(size_t len) {
	if (writableBytes() >= len)
		return;
	if (head_ + writableBytes() >=
			(len + kBufferOffset)) // move readable bytes
	{
		std::copy(begin() + head_, begin() + tail_, begin() + kBufferOffset);
		tail_ = kBufferOffset + (tail_ - head_);
		head_ = kBufferOffset;
		return;
	}
	// create new buffer
	size_t newLen;
	if ((buffer_.size() * 2) > (kBufferOffset + readableBytes() + len))
		newLen = buffer_.size() * 2;
	else
		newLen = kBufferOffset + readableBytes() + len;
	MsgBuffer newbuffer(newLen);
	newbuffer.append(*this);
	swap(newbuffer);
}
void MsgBuffer::swap(MsgBuffer &buf) noexcept {
	buffer_.swap(buf.buffer_);
	std::swap(head_, buf.head_);
	std::swap(tail_, buf.tail_);
	std::swap(initCap_, buf.initCap_);
}
void MsgBuffer::append(const MsgBuffer &buf) {
	ensureWritableBytes(buf.readableBytes());
	memcpy(&buffer_[tail_], buf.peek(), buf.readableBytes());
	tail_ += buf.readableBytes();
}
void MsgBuffer::append(const char *buf, size_t len) {
	ensureWritableBytes(len);
	memcpy(&buffer_[tail_], buf, len);
	tail_ += len;
}
void MsgBuffer::appendInt16(const uint16_t s) {
	uint16_t ss = htons(s);
	append(static_cast<const char *>((void *)&ss), 2);
}
void MsgBuffer::appendInt32(const uint32_t i) {
	uint32_t ii = htonl(i);
	append(static_cast<const char *>((void *)&ii), 4);
}
void MsgBuffer::appendInt64(const uint64_t l) {
	uint64_t ll = Math::hton64(l);
	append(static_cast<const char *>((void *)&ll), 8);
}

void MsgBuffer::addInFrontInt16(const uint16_t s) {
	uint16_t ss = htons(s);
	addInFront(static_cast<const char *>((void *)&ss), 2);
}
void MsgBuffer::addInFrontInt32(const uint32_t i) {
	uint32_t ii = htonl(i);
	addInFront(static_cast<const char *>((void *)&ii), 4);
}
void MsgBuffer::addInFrontInt64(const uint64_t l) {
	uint64_t ll = Math::hton64(l);
	addInFront(static_cast<const char *>((void *)&ll), 8);
}

uint16_t MsgBuffer::peekInt16() const {
	assert(readableBytes() >= 2);
	uint16_t rs = *(static_cast<const uint16_t *>((void *)peek()));
	return ntohs(rs);
}
uint32_t MsgBuffer::peekInt32() const {
	assert(readableBytes() >= 4);
	uint32_t rl = *(static_cast<const uint32_t *>((void *)peek()));
	return ntohl(rl);
}
uint64_t MsgBuffer::peekInt64() const {
	assert(readableBytes() >= 8);
	uint64_t rll = *(static_cast<const uint64_t *>((void *)peek()));
	return Math::ntoh64(rll);
}

void MsgBuffer::retrieve(size_t len) {
	if (len >= readableBytes()) {
		retrieveAll();
		return;
	}
	head_ += len;
}
void MsgBuffer::retrieveAll() {
	if (buffer_.size() > (initCap_ * 2)) {
		buffer_.resize(initCap_);
	}
	tail_ = head_ = kBufferOffset;
}
ssize_t MsgBuffer::readFd(int fd, int *retErrno) {
	char extBuffer[8192];
	struct iovec vec[2];
	size_t writable = writableBytes();
	vec[0].iov_base = begin() + tail_;
	vec[0].iov_len = static_cast<int>(writable);
	vec[1].iov_base = extBuffer;
	vec[1].iov_len = sizeof(extBuffer);
	const int iovcnt = (writable < sizeof extBuffer) ? 2 : 1;
	ssize_t n = ::readv(fd, vec, iovcnt);
	if (n < 0) {
		*retErrno = errno;
	} else if (static_cast<size_t>(n) <= writable) {
		tail_ += n;
	} else {
		tail_ = buffer_.size();
		append(extBuffer, n - writable);
	}
	return n;
}

std::string MsgBuffer::read(size_t len) {
	if (len > readableBytes())
		len = readableBytes();
	std::string ret(peek(), len);
	retrieve(len);
	return ret;
}
uint8_t MsgBuffer::readInt8() {
	uint8_t ret = peekInt8();
	retrieve(1);
	return ret;
}
uint16_t MsgBuffer::readInt16() {
	uint16_t ret = peekInt16();
	retrieve(2);
	return ret;
}
uint32_t MsgBuffer::readInt32() {
	uint32_t ret = peekInt32();
	retrieve(4);
	return ret;
}
uint64_t MsgBuffer::readInt64() {
	uint64_t ret = peekInt64();
	retrieve(8);
	return ret;
}

void MsgBuffer::addInFront(const char *buf, size_t len) {
	if (head_ >= len) {
		memcpy(begin() + head_ - len, buf, len);
		head_ -= len;
		return;
	}
	if (len <= writableBytes()) {
		std::copy(begin() + head_, begin() + tail_, begin() + head_ + len);
		memcpy(begin() + head_, buf, len);
		tail_ += len;
		return;
	}
	size_t newLen;
	if (len + readableBytes() < initCap_)
		newLen = initCap_;
	else
		newLen = len + readableBytes();
	MsgBuffer newBuf(newLen);
	newBuf.append(buf, len);
	newBuf.append(*this);
	swap(newBuf);
}