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// Module Name: RLE.c 
// 
// Description: 
//    A implementation of Run Length Encoding and Decoding Routines 
// 
#include  
#include  
#include  
#include "RLE.h" 
#include "Client.h" 
 
// Global Variables 
DWORD	dwCodeLength = 19; 
 
// Return the Run Length Encoded Size 
DWORD RunLength(BYTE *pInput,DWORD dwCount) 
{ 
	// Compressed Count 
	DWORD	dwNewCount = 4; 
 
	// Max Run Length 
	DWORD	dwMaxRun; 
 
	// Variables Used for Code Shifting 
	DWORD	dwUnusedByte = 0; 
	BOOL	fOutput = FALSE; 
 
	__asm 
	{ 
		// Calculate the Maximum Run Length 
		MOV		EDX,1 
		MOV		ECX,dwCodeLength 
		SUB		ECX,9 
		SHL		EDX,CL 
		SUB		EDX,1 
		MOV		dwMaxRun,EDX 
 
		// Load the Count of Bytes to Encode 
		MOV		EDX,dwCount 
 
		// Initialize the Output Bits 
		XOR		EDI,EDI 
 
		// Initialize the Storage DWORD 
		XOR		ESI,ESI 
 
		// Load the Byte to Compare 
		_LoadByte: 
 
		// Save the Storage DWORD 
		PUSH	ESI 
 
		// Load a Byte 
		MOV		ESI,pInput 
		MOV		AL,[ESI] 
 
		// Initialize the Run Length Count to 1 
		MOV		ECX,DWORD PTR 1 
 
		// Compare the Bytes 
		_CompareBytes: 
 
		// Check for EOD 
		CMP		EDX,0 
		JZ		_Finished 
 
		// Compare to the Max Length for an Encode 
		CMP		ECX,dwMaxRun 
		JA		_Finished 
 
		// Compare the Bytes 
		CMP		AL,[ESI + ECX] 
 
		// Increment the Run Length 
		LEA		ECX,[ECX + 1] 
 
		// Decrement the Bytes Processed 
		LEA		EDX,[EDX - 1] 
 
		// Branch for the Comparison 
		JE		_CompareBytes 
 
		// Finished Encoding 
		_Finished: 
 
		// Decrement the Run Length for Encoding 
		DEC		ECX 
 
		// Increment the Pointer to the Source Data 
		ADD		ESI,ECX 
		MOV		pInput,ESI 
 
		// Restore the Storage DWORD 
		POP		ESI 
 
		// Check for a 1:1 Character Copy 
		CMP		ECX,1 
		JNZ		_BuildCode 
 
		// Move in the Character 
		XOR		EBX,EBX 
		MOV		BH,1 
		MOV		BL,AL 
 
		// Set the Code Length 
		MOV		ECX,9 
 
		// Jump to Checking the Bit Shifting 
		JMP		_CheckShift 
 
		// Build the Compression Code 
		_BuildCode: 
		MOV		EBX,ECX 
		SHL		EBX,8 
		MOV		BL,AL 
 
		// Set the Code Length 
		MOV		ECX,dwCodeLength 
 
		// See How Many Bits Can be Shifted to the Output DWORD 
		_CheckShift: 
		ADD		EDI,ECX 
		CMP		EDI,32 
		JLE		_ShiftData 
 
		// See How Many Bits of the Last Code Can't Be Used 
		SUB		EDI,32 
 
		// Adjust ECX to Handle only the Bits that Can Be Used 
		SUB		ECX,EDI 
 
		// Save the Code 
		MOV		dwUnusedByte,EBX 
 
		// Shift the Input Symbol to the Right 
		PUSH	ECX 
		MOV		ECX,EDI 
		SHR		EBX,CL 
		POP		ECX 
 
		// Set the Output Flag 
		MOV		fOutput,TRUE 
 
		// Shift the Output Data 
		_ShiftData: 
 
		// Shift the Output Symbol to Handle a New Symbol 
		SHL		ESI,CL 
 
		// OR the Output Symbol with New Symbol 
		OR		ESI,EBX 
 
		// Check for Outputting a full DWORD 
		CMP		fOutput,FALSE 
		JE		_Continue 
 
		// Increment the Compression Count 
		ADD		dwNewCount,4 
 
		// Remove the Bits we Used 
		MOV		EAX,32 
		SUB		EAX,EDI 
		MOV		ECX,EAX 
 
		// Restore the Unused Portion of the Code 
		MOV		EAX,dwUnusedByte 
		SHL		EAX,CL 
		SHR		EAX,CL 
 
		// Update the Code to Have the Left Over Bits 
		MOV		ESI,EAX 
 
		// Initialize the Left Over Bits 
		MOV		dwUnusedByte,0 
 
		// Reset the Output Flag 
		MOV		fOutput,FALSE 
 
		// Compare for More Data 
		_Continue: 
		CMP		EDX,0 
		JZ		_Exit 
 
		// Go Back for More Bytes 
		JMP		_LoadByte 
 
		// Finished Encoding 
		_Exit: 
 
		// Update Any Remaining Compression data in the Buffer 
		CMP		EDI,0 
		JE		_Done 
 
		// Left Shift the Remaining Bits 
		MOV		EAX,32 
		SUB		EAX,EDI 
		MOV		ECX,EAX 
		SHL		ESI,CL 
 
		// Increment the Compression Count 
		ADD		dwNewCount,4 
 
		// Done Encoding 
		_Done: 
	} 
 
	// Return the Compressed Count 
	return dwNewCount; 
} 
 
// Run Length Encode the Input Data to the Output Data 
DWORD RunLengthEncode(BYTE *pInput,DWORD dwCount,BYTE *pOutput) 
{ 
	// Compressed Count 
	DWORD	dwNewCount = 4; 
 
	// Variables Used for Code Shifting 
	DWORD	dwUnusedByte = 0; 
	BOOL	fOutput = FALSE; 
 
	// Max Run Length 
	DWORD	dwMaxRun; 
 
	__asm 
	{ 
		// Calculate the Maximum Run Length 
		MOV		EDX,1 
		MOV		ECX,dwCodeLength 
		SUB		ECX,9 
		SHL		EDX,CL 
		SUB		EDX,1 
		MOV		dwMaxRun,EDX 
 
		// Point to the Input Byte 
		MOV		EDI,pOutput 
 
		// Load the Count of Bytes to Encode 
		MOV		EDX,dwCount 
 
		// Store the Original Length in the Compressed Data 
		MOV		[EDI],EDX 
 
		// Increment the Input Data Pointer 
		ADD		EDI,4 
		MOV		pOutput,EDI 
 
		// Initialize the Output Bits 
		XOR		EDI,EDI 
 
		// Initialize the Storage DWORD 
		XOR		ESI,ESI 
 
		// Load the Byte to Compare 
		_LoadByte: 
 
		// Save the Storage DWORD 
		PUSH	ESI 
 
		// Load a Byte 
		MOV		ESI,pInput 
		MOV		AL,[ESI] 
 
		// Initialize the Run Length Count to 1 
		MOV		ECX,DWORD PTR 1 
 
		// Compare the Bytes 
		_CompareBytes: 
 
		// Check for EOD 
		CMP		EDX,0 
		JZ		_Finished 
 
		// Compare to the Max Length for an Encode 
		CMP		ECX,dwMaxRun 
		JA		_Finished 
 
		// Compare the Bytes 
		CMP		AL,[ESI + ECX] 
 
		// Increment the Run Length 
		LEA		ECX,[ECX + 1] 
 
		// Decrement the Bytes Processed 
		LEA		EDX,[EDX - 1] 
 
		// Branch for the Comparison 
		JE		_CompareBytes 
 
		// Finished Encoding 
		_Finished: 
 
		// Decrement the Run Length for Encoding 
		DEC		ECX 
 
		// Increment the Pointer to the Source Data 
		ADD		ESI,ECX 
		MOV		pInput,ESI 
 
		// Restore the Storage DWORD 
		POP		ESI 
 
		// Check for a 1:1 Character Copy 
		CMP		ECX,1 
		JNZ		_BuildCode 
 
		// Move in the Character 
		XOR		EBX,EBX 
		MOV		BH,1 
		MOV		BL,AL 
 
		// Set the Code Length 
		MOV		ECX,9 
 
		// Jump to Checking the Bit Shifting 
		JMP		_CheckShift 
 
		// Build the Compression Code 
		_BuildCode: 
		MOV		EBX,ECX 
		SHL		EBX,8 
		MOV		BL,AL 
 
		// Set the Code Length 
		MOV		ECX,dwCodeLength 
 
		// See How Many Bits Can be Shifted to the Output DWORD 
		_CheckShift: 
		ADD		EDI,ECX 
		CMP		EDI,32 
		JLE		_ShiftData 
 
		// See How Many Bits of the Last Code Can't Be Used 
		SUB		EDI,32 
 
		// Adjust ECX to Handle only the Bits that Can Be Used 
		SUB		ECX,EDI 
 
		// Save the Code 
		MOV		dwUnusedByte,EBX 
 
		// Shift the Input Symbol to the Right 
		PUSH	ECX 
		MOV		ECX,EDI 
		SHR		EBX,CL 
		POP		ECX 
 
		// Set the Output Flag 
		MOV		fOutput,TRUE 
 
		// Shift the Output Data 
		_ShiftData: 
 
		// Shift the Output Symbol to Handle a New Symbol 
		SHL		ESI,CL 
 
		// OR the Output Symbol with New Symbol 
		OR		ESI,EBX 
 
		// Check for Outputting a full DWORD 
		CMP		fOutput,FALSE 
		JE		_Continue 
 
		// Output an Encoded Symbol 
		MOV		EAX,ESI 
		PUSH	EDI 
		MOV		EDI,pOutput 
		MOV		[EDI],EAX 
		ADD		EDI,4 
		MOV		pOutput,EDI 
		POP		EDI 
 
		// Increment the Compression Count 
		ADD		dwNewCount,4 
 
		// Remove the Bits we Used 
		MOV		EAX,32 
		SUB		EAX,EDI 
		MOV		ECX,EAX 
 
		// Restore the Unused Portion of the Code 
		MOV		EAX,dwUnusedByte 
		SHL		EAX,CL 
		SHR		EAX,CL 
 
		// Update the Code to Have the Left Over Bits 
		MOV		ESI,EAX 
 
		// Initialize the Left Over Bits 
		MOV		dwUnusedByte,0 
 
		// Reset the Output Flag 
		MOV		fOutput,FALSE 
 
		// Compare for More Data 
		_Continue: 
		CMP		EDX,0 
		JZ		_Exit 
 
		// Go Back for More Bytes 
		JMP		_LoadByte 
 
		// Finished Encoding 
		_Exit: 
 
		// Update Any Remaining Compression data in the Buffer 
		CMP		EDI,0 
		JE		_Done 
 
		// Left Shift the Remaining Bits 
		MOV		EAX,32 
		SUB		EAX,EDI 
		MOV		ECX,EAX 
		SHL		ESI,CL 
 
		// Output the Final Encoded Symbol 
		MOV		EAX,ESI 
		MOV		EDI,pOutput 
		MOV		[EDI],EAX 
 
		// Increment the Compression Count 
		ADD		dwNewCount,4 
 
		// Done Encoding 
		_Done: 
	} 
 
	// Return the Compressed Count 
	return dwNewCount; 
} 
 
// Run Length Decode the Input Data to the Output Data 
DWORD RunLengthDecode(BYTE *pInput,BYTE *pOutput) 
{ 
	// Compressed Count 
	DWORD	dwCount; 
	DWORD	dwCompCount; 
	DWORD	dwCodeLength2; 
 
	__asm 
	{ 
		// Get the CodeLength - 1 for Checking a 1:1 Compression 
		MOV		EAX,dwCodeLength 
		DEC		EAX 
		MOV		dwCodeLength2,EAX 
 
		// Point to the Input Byte 
		MOV		ESI,pInput 
 
		// Point to the Output Byte 
		MOV		EDI,pOutput 
 
		// Load the Count of Bytes Encoded 
		LODSD 
 
		// Save the New Input Location 
		MOV		pInput,ESI 
 
		// Save the Count of the UnCompressed Data 
		MOV		dwCompCount,EAX 
 
		// Initialize the Count of Bytes Decoded 
		MOV		dwCount,EAX 
 
		// Initialize Number of Bits for Current Symbol to Process 
		MOV		ESI,dwCodeLength 
 
		// Initialize the Decode Storage 
		XOR		EDX,EDX 
 
		// Main Loop for Reading Input 
		_LoopInput: 
 
		// Save the Number of Bits for the Current Symbol 
		PUSH	ESI 
 
		// Point to the Input Data 
		MOV		ESI,pInput 
 
		// Read an Encoded DWORD 
		LODSD 
 
		// Save the Pointer to the Input Data 
		MOV		pInput,ESI 
 
		// Restore the Number of Bits for the Current Symbol 
		POP		ESI 
 
		// Initialize Number of Bits to Process 
		MOV		EBX,32 
 
		// Shift in an Encoded Symbol, 1 bit at a time 
		_LeftShift: 
 
		// Shift 1 Bit of the Input Code to the Output 
		SHLD	EDX,EAX,1 
 
		// Shift the Input Code 1 Bit to the Left 
		SHL		EAX,1 
 
		// Decrement the Number of Bits Processed 
		DEC		ESI 
 
		// Check for a Fully Encoded Symbol 
		JZ		_Output 
 
		// Compare the High Bit for RLE or Character Encode 
		CMP		ESI,dwCodeLength2 
		JNZ		_CheckBits 
 
		// Compare the High Bit, 0 = RLE, 1 = 1:1 Character Encode 
		CMP		EDX,0 
		JZ		_CheckBits 
 
		// Update the Bits Left to 8 
		MOV		ESI,8 
 
		// Check for More Bits to Process 
		_CheckBits: 
 
		// Decrement the Number of Bits Processed in the Input DWORD 
		DEC		EBX 
 
		// Continue Shifting More Bits 
		JNZ		_LeftShift 
 
		// Read Another DWORD of Data 
		JMP		_LoopInput 
 
		// Output the Run Length Amount of the Code 
		_Output: 
 
		// Get the Run Length 
		MOV		ECX,EDX 
		SHR		ECX,8 
 
		// Get the Code 
		AND		EDX,255 
 
		// Save the Input DWORD 
		PUSH	EAX 
 
		// Copy the Code 
		MOV		EAX,EDX 
 
		// Save the Run Length 
		PUSH	ECX 
 
		// Output the Run Length Amount of the Code 
		REP		STOSB 
 
		// Restore the Run Length 
		POP		ECX 
 
		// Restore the Input DWORD 
		POP		EAX 
 
		// Check for More Data to Decode 
		SUB		dwCompCount,ECX 
		JZ		_Exit 
 
		// Initialize the Decode Storage 
		XOR		EDX,EDX 
 
		// Initialize Number of Bits for Current Symbol to Process 
		MOV		ESI,dwCodeLength 
 
		// Check for More Bits to Process 
		JMP		_CheckBits 
 
		// Finished 
		_Exit: 
	} 
 
	// Return the Count of Uncompressed Data 
	return dwCount; 
}