[英]How to write and read bytes in Postgres with C
I write BYTE*
to bytea
field in postgres with function, which returns bytea:我使用 function 将BYTE*
写入 postgres 中的bytea
字段,返回 bytea:
...
PG_RETURN_BYTEA_P(pbBuffer);
These bytes look in file like:这些字节在文件中看起来像: Later Im trying read this bytea
field and write to other file with other function like this:后来我尝试读取这个bytea
字段并使用其他 function 写入其他文件,如下所示:
bytea* data = PG_GETARG_BYTEA_P(0);
char filePath[] = "C:\\pg\\11.txt";
HANDLE h = CreateFile(filePath, FILE_WRITE_DATA, FILE_SHARE_READ, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
DWORD dw = sizeof(data);
WriteFile(h, data, dw, &dw, NULL);
CloseHandle(h);
In file It looks like:在文件中它看起来像: What should I do to get the same result as in begin?我应该怎么做才能得到与开始相同的结果?
first function works:第一个 function 作品:
FILE* log = AllocateFile("C:\\pg\\log.txt", PG_BINARY_A);
char* dataToEncrypt = PG_GETARG_CSTRING(0);
FILE* tempFile = AllocateFile("C:\\pg\\openText.txt", PG_BINARY_A);
fprintf(tempFile, "%s", dataToEncrypt);
FreeFile(tempFile);
HANDLE hSourceFile = INVALID_HANDLE_VALUE;
HANDLE hDestinationFile = INVALID_HANDLE_VALUE;
HCRYPTPROV hCryptProv = NULL;
HCRYPTKEY hKey = NULL;
HCRYPTKEY hXchgKey = NULL;
HCRYPTHASH hHash = NULL;
PBYTE pbKeyBlob = NULL;
DWORD dwKeyBlobLen;
PBYTE pbBuffer = NULL;
DWORD dwBlockLen;
DWORD dwBufferLen;
DWORD dwCount;
bool fEOF = FALSE;
char pszPassword[] = "key";
char s[] = "C:\\pg\\openText.txt";
char d[] = "C:\\pg\\cryptoText.txt";
hSourceFile = CreateFile(s, FILE_READ_DATA, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if (INVALID_HANDLE_VALUE == hSourceFile)
{
fprintf(log, "%u %s\n", GetLastError(), "CreateFile s");
goto Exit_MyEncryptFile;
}
hDestinationFile = CreateFile(d, FILE_WRITE_DATA, FILE_SHARE_READ, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
if (INVALID_HANDLE_VALUE == hDestinationFile)
{
fprintf(log, "%u %s\n", GetLastError(), "CreateFile d");
goto Exit_MyEncryptFile;
}
if (!CryptAcquireContext(&hCryptProv, NULL, MS_ENHANCED_PROV, PROV_RSA_FULL, 0))
{
fprintf(log, "%u %s\n", GetLastError(), "CryptAcquireContext");
goto Exit_MyEncryptFile;
}
if (!CryptCreateHash(hCryptProv, CALG_MD5, 0, 0, &hHash))
{
fprintf(log, "%u %s\n", GetLastError(), "CryptCreateHash");
goto Exit_MyEncryptFile;
}
if (!CryptHashData(hHash, (BYTE*)pszPassword, lstrlen(pszPassword), 0))
{
fprintf(log, "%u %s\n", GetLastError(), "CryptHashData");
goto Exit_MyEncryptFile;
}
if (!CryptDeriveKey(hCryptProv, ENCRYPT_ALGORITHM, hHash, KEYLENGTH, &hKey))
{
fprintf(log, "%u %s\n", GetLastError(), "CryptDeriveKey");
goto Exit_MyEncryptFile;
}
dwBlockLen = 1000 - 1000 % ENCRYPT_BLOCK_SIZE;
if (ENCRYPT_BLOCK_SIZE > 1)
dwBufferLen = dwBlockLen + ENCRYPT_BLOCK_SIZE;
else
dwBufferLen = dwBlockLen;
pbBuffer = (BYTE*)malloc(dwBufferLen);
do
{
if (!ReadFile(hSourceFile, pbBuffer, dwBlockLen, &dwCount, NULL))
{
fprintf(log, "%u %s\n", GetLastError(), "ReadFile");
goto Exit_MyEncryptFile;
}
if (dwCount < dwBlockLen)
fEOF = TRUE;
if (!CryptEncrypt(hKey, NULL, fEOF, 0, pbBuffer, &dwCount, dwBufferLen))
{
fprintf(log, "%u %s\n", GetLastError(), "CryptEncrypt");
goto Exit_MyEncryptFile;
}
if (!WriteFile(hDestinationFile, pbBuffer, dwCount, &dwCount, NULL))
{
fprintf(log, "%u %s\n", GetLastError(), "WriteFile");
goto Exit_MyEncryptFile;
}
} while (!fEOF);
You don't show us the function that creates that bytea
, so I have no idea if you did it right.您没有向我们展示创建该bytea
的 function ,所以我不知道您是否做对了。
But you most certainly messed up the second function:但你肯定搞砸了第二个 function:
A bytea
is not a string. bytea
不是字符串。 If you read in src/include/fmgr.h
,如果您阅读src/include/fmgr.h
,
/*
* Support for fetching detoasted copies of toastable datatypes (all of
* which are varlena types). pg_detoast_datum() gives you either the input
* datum (if not toasted) or a detoasted copy allocated with palloc().
* pg_detoast_datum_copy() always gives you a palloc'd copy --- use it
* if you need a modifiable copy of the input. Caller is expected to have
* checked for null inputs first, if necessary.
*
* pg_detoast_datum_packed() will return packed (1-byte header) datums
* unmodified. It will still expand an externally toasted or compressed datum.
* The resulting datum can be accessed using VARSIZE_ANY() and VARDATA_ANY()
* (beware of multiple evaluations in those macros!)
*
* In consumers oblivious to data alignment, call PG_DETOAST_DATUM_PACKED(),
* VARDATA_ANY(), VARSIZE_ANY() and VARSIZE_ANY_EXHDR(). Elsewhere, call
* PG_DETOAST_DATUM(), VARDATA() and VARSIZE(). Directly fetching an int16,
* int32 or wider field in the struct representing the datum layout requires
* aligned data. memcpy() is alignment-oblivious, as are most operations on
* datatypes, such as text, whose layout struct contains only char fields.
*
* Note: it'd be nice if these could be macros, but I see no way to do that
* without evaluating the arguments multiple times, which is NOT acceptable.
*/
Now, since bytea
is a varlena
type, the code should look somewhat like this:现在,由于bytea
是varlena
类型,代码应该看起来像这样:
bytea* data = PG_GETARG_BYTEA_PP(0);
uint32 data_length = VARSIZE_ANY(data);
char *raw_data = VARDATA_ANY(data);
WriteFile(h, raw_data, data_length, &dw, NULL);
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.