std::basic_istream::read
性病：基本[医]iStream：：
| basic_istream& read( char_type* s, std::streamsize count | | |
|---|
从流中提取字符。
表现为UnformattedInputFunction.在构造和检查哨兵对象之后，提取字符并将它们存储到字符数组的连续位置，该字符数组的第一个元素由s提取和存储字符，直到出现下列任何情况：
count提取并存储字符
- 文件结束条件发生在输入序列%28上，在这种情况下，
setstate(failbit|eofbit)称为%29。成功提取的字符数可以使用Gcount%28%29...
参数
| s | - | pointer to the character array to store the characters to |
|---|---|---|
| count | - | number of characters to read |
返回值
*this...
例外
failure如果发生错误%28，则错误状态标志不是goodbit29%和exceptions()将被抛向那个州。
如果内部操作抛出异常，则会捕获该操作，并且badbit已经设定好了。如果exceptions()设置为badbit，异常将被重新抛出。
例
二次
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <cstdint>
int main()
{
// read() is often used for binary I/O
std::string bin = {'\x12', '\x12', '\x12', '\x12'};
std::istringstream raw(bin
std::uint32_t n;
if(raw.read(reinterpret_cast<char*>(&n), sizeof n))
std::cout << std::hex << std::showbase << n << '\n';
// prepare file for next snippet
std::ofstream("test.txt", std::ios::binary) << "abcd1\nabcd2\nabcd3";
// read entire file into string
if(std::ifstream is{"test.txt", std::ios::binary | std::ios::ate}) {
auto size = is.tellg(
std::string str(size, '\0' // construct string to stream size
is.seekg(0
if(is.read(&str[0], size))
std::cout << str << '\n';
}
}
二次
产出：
二次
0x12121212
abcd1
abcd2
abcd3
二次
另见
| write | inserts blocks of characters (public member function of std::basic_ostream) |
|---|---|
| operator>> | extracts formatted data (public member function) |
| readsome | extracts already available blocks of characters (public member function) |
| get | extracts characters (public member function) |
| getline | extracts characters until the given character is found (public member function) |
| fread | reads from a file (function) |
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