无法使用 sqlite3 和 C++ 解压缩从 sql table 中选择的压缩字符串
Cannot decompress a compressed string selected from an sql table using sqlite3 and C++
描述
我正在尝试将压缩数据插入 sql table,然后提取并解压缩它。起初我压缩一个字符串,然后将其插入 table (第 1 节)。压缩工作正常。即使当我在插入之前尝试解压缩它时,我也会取回字符串。插入字符串并稍后尝试将其提取回来后出现问题。
正如您在代码的第 2 部分中看到的那样。解压就不行了。我不知道为什么在我从 table.
中提取它后它不再起作用了
源代码
#include <zlc/zlibcomplete.hpp>
#include <string>
#include "3rdparty/sqlite_modern_cpp.h"
using namespace std;
using namespace zlibcomplete;
int main()
{
//SECTION 1
database db("data.db");
db << "CREATE TABLE IF NOT EXISTS paragraph(ID INTEGER PRIMARY KEY, LINE TEXT);";
string line = "hello world!";
//Compress string by using zlib
GZipCompressor compressor(9, auto_flush);
string compressed_line = compressor.compress(line);
compressor.finish();
//IF I DECOMPRESS STRING HERE IT WORKS FINE!!!
GZipDecompressor decompressor;
string output = decompressor.decompress(line);
//insert compressed string into table paragraph
db <<"insert into paragraph(ID,LINE) VALUES (?,?);"
<< 1
<< compressed_line;
//SECTION 2: Problem starts here where I try to return the compressed value
db <<"select line from paragraph where id = ?;"
<< "1"
>>[&](string line)
{
//Decompress string by using zlib
GZipDecompressor decompressor;
string output = decompressor.decompress(line);
//out is empty I don't know why???
cout << output << endl;
};
return 0;
}
修正后更新
第一次下载base64 classes as pointed out in this solution.
#include <zlc/zlibcomplete.hpp>
#include <string>
#include "3rdparty/sqlite_modern_cpp.h"
#include "base64.h"
using namespace std;
using namespace zlibcomplete;
int main()
{
//SECTION 1
database db("data.db");
db << "CREATE TABLE IF NOT EXISTS paragraph(ID INTEGER PRIMARY KEY, LINE TEXT);";
string line = "hello world!";
//Compress string by using zlib
GZipCompressor compressor(9, auto_flush);
string compressed_line = compressor.compress(line);
compressor.finish();
std::string compressed = base64_encode(reinterpret_cast<const unsigned char*>(compressed_line.c_str()), compressed_line.length());
//insert compressed string into table paragraph
db <<"insert into paragraph(ID,LINE) VALUES (?,?);"
<< 1
<< compressed;
db <<"select line from paragraph where id = ?;"
<< "1"
>>[&](string line)
{
//decode HERE
std::string compressed_decoded = base64_decode(line);
//Decompress string by using zlib
GZipDecompressor decompressor;
string output = decompressor.decompress(line);
cout << output << endl;
};
return 0;
}
您的代码无法处理压缩字符串中的零。如果压缩字符串中有一个字符 0,那么文本将被截断并且不再可能进行反向操作。
描述
我正在尝试将压缩数据插入 sql table,然后提取并解压缩它。起初我压缩一个字符串,然后将其插入 table (第 1 节)。压缩工作正常。即使当我在插入之前尝试解压缩它时,我也会取回字符串。插入字符串并稍后尝试将其提取回来后出现问题。
正如您在代码的第 2 部分中看到的那样。解压就不行了。我不知道为什么在我从 table.
中提取它后它不再起作用了源代码
#include <zlc/zlibcomplete.hpp>
#include <string>
#include "3rdparty/sqlite_modern_cpp.h"
using namespace std;
using namespace zlibcomplete;
int main()
{
//SECTION 1
database db("data.db");
db << "CREATE TABLE IF NOT EXISTS paragraph(ID INTEGER PRIMARY KEY, LINE TEXT);";
string line = "hello world!";
//Compress string by using zlib
GZipCompressor compressor(9, auto_flush);
string compressed_line = compressor.compress(line);
compressor.finish();
//IF I DECOMPRESS STRING HERE IT WORKS FINE!!!
GZipDecompressor decompressor;
string output = decompressor.decompress(line);
//insert compressed string into table paragraph
db <<"insert into paragraph(ID,LINE) VALUES (?,?);"
<< 1
<< compressed_line;
//SECTION 2: Problem starts here where I try to return the compressed value
db <<"select line from paragraph where id = ?;"
<< "1"
>>[&](string line)
{
//Decompress string by using zlib
GZipDecompressor decompressor;
string output = decompressor.decompress(line);
//out is empty I don't know why???
cout << output << endl;
};
return 0;
}
修正后更新
第一次下载base64 classes as pointed out in this solution.
#include <zlc/zlibcomplete.hpp>
#include <string>
#include "3rdparty/sqlite_modern_cpp.h"
#include "base64.h"
using namespace std;
using namespace zlibcomplete;
int main()
{
//SECTION 1
database db("data.db");
db << "CREATE TABLE IF NOT EXISTS paragraph(ID INTEGER PRIMARY KEY, LINE TEXT);";
string line = "hello world!";
//Compress string by using zlib
GZipCompressor compressor(9, auto_flush);
string compressed_line = compressor.compress(line);
compressor.finish();
std::string compressed = base64_encode(reinterpret_cast<const unsigned char*>(compressed_line.c_str()), compressed_line.length());
//insert compressed string into table paragraph
db <<"insert into paragraph(ID,LINE) VALUES (?,?);"
<< 1
<< compressed;
db <<"select line from paragraph where id = ?;"
<< "1"
>>[&](string line)
{
//decode HERE
std::string compressed_decoded = base64_decode(line);
//Decompress string by using zlib
GZipDecompressor decompressor;
string output = decompressor.decompress(line);
cout << output << endl;
};
return 0;
}
您的代码无法处理压缩字符串中的零。如果压缩字符串中有一个字符 0,那么文本将被截断并且不再可能进行反向操作。