Get file type and url

Member 7766180 wrote:

Is there code to read this "Magic"? I think I know what it is, thanks to your help! But how does one access or read the "Magic"?

#include <Windows.h>
#include <stdio.h>
typedef struct {
	DWORD nLength; //The size of the magic. Must be <8, or increase the size of BYTE pFileStart[8]; at the top of GetFileType
	char *pMagic;  //The exact bytes that must match
} FileMagic;
FileMagic g_fmFileTypes[] = {
	{ 4, "RIFF" },      //index 0
	{ 3, "ID3" },       //index 1
	{ 4, "PK\x03\x04" } //\xNN gives the character with the hex code NN.
};
LPCSTR GetFileExtensions(int nMagicID) {
	switch (nMagicID) {
		case 0: //RIFF
			return "mp3";
		case 1: //ID3
			return "avi;wav";
		case 2: //PK\x03\x04
			return "zip";
	}
	return ""; //No file extension / unknown
}
int GetFileType(LPCSTR szFileName) {
	BYTE pFileStart[8];
	DWORD nBytesRead;
	int nFileType;
	BYTE *pData = NULL;
	int nMagicID = -1;
	//Open the file for reading
	HANDLE hFile = CreateFile(szFileName, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
	if (hFile == NULL) {
		return -2;
	}
	if (!ReadFile(hFile, pFileStart, sizeof(pFileStart), &nBytesRead, NULL) || nBytesRead != sizeof(pFileStart)) {
		CloseHandle(hFile);
		return -2;
	}
	//Loop through file magics defined in g_fmFileTypes to find a match
	for (nFileType = 0; nFileType < ARRAYSIZE(g_fmFileTypes); ++nFileType) {
		if (memcmp(g_fmFileTypes[nFileType].pMagic, pFileStart, g_fmFileTypes[nFileType].nLength) == 0) { //Does the magic match?
			nMagicID = nFileType; //Save the ID of this file type
			break; //Stop searching
		}
	}
	CloseHandle(hFile);
	return nMagicID;
}
int main(int argc, char *argv[]) {
	if (argc != 2) {
		printf("Usage: %s <file to test>\n", argv[0]);
	}
	int nMagicID = GetFileType(argv[1]); //Get the file magic
	if (nMagicID == -2) {
		puts("An error occured.");
	} else if (nMagicID == -1) {
		puts("The type of this file is unknown.");
	} else {
		printf("The file type(s) are: %s\n", GetFileExtensions(nMagicID)); //Now print the possible file extensions
	}
	return 0;
}

#include <Windows.h>
#include <stdio.h>

typedef enum {
	FMID_ERROR,   //File not found, permission denied, ...
	FMID_UNKNOWN, //The file format is unknown
	FMID_ID3,     //MP3
	FMID_RIFF,    //AVI or WAV
	FMID_PK,      //ZIP
} FileMagicID;

typedef struct {
	DWORD nOffset;         //The position from the start of the file of the magic. Usually 0.
	DWORD nLength;         //The size of the magic
	char *pMagic;          //The exact bytes that must match
	FileMagicID eFileType; //A unique number to identify the file in this program. Has no meaning outside of this code.
} FileMagic;

FileMagic g_fmFileTypes[] = {
	{ 0, 4, "RIFF", FMID_RIFF },
	{ 0, 3, "ID3", FMID_ID3 },
	{ 0, 4, "PK\x03\x04", FMID_PK } //\xNN gives the character with the hex code NN.
	//Add your file formats in here in the format
	//{ [offset of magic], [length of magic], [magic as either a string "abc" or array { 'a', 'b', 'c' }], [the internal identifier, FMID_???] }
};

FileMagicID GetFileType(LPCSTR szFileName) {
	BYTE pFileStart[8];
	DWORD nBytesRead;
	DWORD nFileType;
	BYTE *pData = NULL;
	FileMagicID idMagic = FMID_UNKNOWN;
	HANDLE hFile = CreateFile(szFileName, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
	if (hFile == NULL) {
		return FMID_ERROR;
	}
	if (!ReadFile(hFile, pFileStart, sizeof(pFileStart), &nBytesRead, NULL) || nBytesRead != sizeof(pFileStart)) {
		CloseHandle(hFile);
		return FMID_ERROR;
	}
	for (nFileType = 0; nFileType < ARRAYSIZE(g_fmFileTypes); ++nFileType) {
		if (g_fmFileTypes[nFileType].nOffset + g_fmFileTypes[nFileType].nLength < sizeof(pFileStart)) { //Do we already have enough data read in?
			if (memcmp(g_fmFileTypes[nFileType].pMagic, pFileStart + g_fmFileTypes[nFileType].nOffset, g_fmFileTypes[nFileType].nLength) == 0) { //Does the magic match?
				idMagic = g_fmFileTypes[nFileType].eFileType; //Save the ID of this file type
				break; //Stop searching
			} //else file is not this type, keep searching
		} else { //No, we have to read it
			pData = (BYTE *)malloc(g_fmFileTypes[nFileType].nLength);
			if (pData == NULL) { //Not enough memory
				idMagic = FMID_ERROR;
				break;
			}
			nBytesRead = SetFilePointer(hFile, g_fmFileTypes[nFileType].nOffset, NULL, FILE_BEGIN); //Seek to where the magic should be
			if (nBytesRead == g_fmFileTypes[nFileType].nOffset) { //Is the file big enough?
				if (ReadFile(hFile, pData, g_fmFileTypes[nFileType].nLength, &nBytesRead, NULL) && nBytesRead == g_fmFileTypes[nFileType].nLength) { //Was the file big enough to read all the data?
					if (memcmp(g_fmFileTypes[nFileType].pMagic, pData, g_fmFileTypes[nFileType].nLength) == 0) { //Does the magic match?
						idMagic = g_fmFileTypes[nFileType].eFileType; //Save the ID of this file type
						free(pData);
						break; //Stop searching
					}
				} //else file is not this type, keep searching
			} //else file is not this type, keep searching
			free(pData);
		}
	}
	CloseHandle(hFile);
	return idMagic;
}

//A simple function for getting a file extension from the internal identifier, FMID_???
LPCSTR GetFileExtensions(FileMagicID fmMagic) {
	switch (fmMagic) {
		case FMID_ID3:
			return "mp3";
		case FMID_RIFF:
			return "avi;wav";
		case FMID_PK:
			return "zip";
	}
	return ""; //No file extension / unknown
}

int main(int argc, char *argv[]) {
	if (argc != 2) {
		printf("Usage: %s <file to test>\n", argv[0]);
	}
	FileMagicID fmMagic = GetFileType(argv[1]); //Get the file magic
	if (fmMagic == FMID_ERROR) {
		puts("An error occured.");
	} else if (fmMagic == FMID_UNKNOWN) {
		puts("The type of this file is unknown.");
	} else {
		printf("The file type(s) are: %s\n", GetFileExtensions(fmMagic)); //Now print the possible file extensions
	}
	return 0;
}

>Magic.exe test.zip
The file types are: zip
>move test.zip test.mp3
>Magic.exe test.mp3
The file types are: zip