buffer 缓冲区

qqmusic::utils::buffer提供了二进制缓冲区类, 以及用于curl库写缓冲区的回调函数

相关头文件: qqmusic/utils/buffer.h

class buffer

二进制缓冲区类

constructor

构造函数, 共3个重载

qqmusic::utils::buffer();

默认构造函数, 初始化空的缓冲区

qqmusic::utils::buffer(size_t size);

预先分配长度为size的缓冲区, 内容全为\0

qqmusic::utils::buffer(const uint8_t* src_head, size_t size);

将开头为src_head, 长度为size的内存拷贝到新创建的缓冲区内

func get_size

size_t
qqmusic::utils::buffer::get_size() const;

获取当前缓冲区的长度, 返回size_t类型

func get_head

uint8_t*
qqmusic::utils::buffer::get_head() const;

返回uint8* const类型的缓冲区开头地址, 不可更改.

func append

size_t
qqmusic::utils::buffer::append(const void* src_data_buf,
                               size_t data_buf_size);

将src_data_buf开头的data_buf_size字节数据插入缓冲区后面.

如果成功操作, 就返回插入的数据大小, 否则返回-1

func clear

void
qqmusic::utils::buffer::clear();

将缓冲区内容清除

func resize

bool
qqmusic::utils::buffer::resize(size_t size);

将缓冲区大小设置为size, 如果成功就返回false, 否则返回true

func http_writebuf

size_t http_writebuf(void*  src_data_buf,
                     size_t data_buf_size,
                     size_t data_buf_num,
                     void*  buffer_ptr);

http_writebuf函数是为与libcurl交互设计的回调函数.

使用案例

#include <fstream>
#include <string>

#include <curl/curl.h>
#include <utils/buffer.h>

int main(int argc, char** argv)
{
    if (argc != 3) {
        printf("Usage -- %s url output_file_name\n", argv[0]);
        return 1;
    }
    std::string url = std::string(argv[1]);
    std::string output_file_name = std::string(argv[2]);
    utils::buffer buf;

    curl_global_init(CURL_GLOBAL_DEFAULT);
    CURL* handle = curl_easy_init();


    // set handler options
    curl_easy_setopt(handle, CURLOPT_URL, url.c_str());

    // set http_writebuf as CURLOPT_WRITEFUNCTION
    curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, utils::http_writebuf);
    curl_easy_setopt(handle, CURLOPT_USERAGENT, "Mozilla/5.0 (X11; Linux x86_64) "
                                                "AppleWebKit/537.36 (KHTML, like Gecko) "
                                                "Chrome/122.0.0.0 Safari/537.36");

    // pass the address of buffer object to CURLOPT_WRITEDATA
    curl_easy_setopt(handle, CURLOPT_WRITEDATA, &buf);
    curl_easy_perform(handle);

    curl_easy_cleanup(handle);
    curl_global_cleanup();

    std::fstream output_file;
    output_file.open(output_file_name, std::ios::out);
    output_file.write((char*)buf.get_head(), buf.get_size());
    output_file.close();
    return 0;
}