an ancient (ca. 2005) sega dreamcast AFS archive unpacker written by a high schooler who still commented every line of their programs

AFS_Unpk.c

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>

struct afsHeader // Header of the file
{
	char magic[4]; // Magic word "AFS"
	uint32_t count; // Number of .ADX files in the archive
};

struct afsEntry // Each entry in the .AFS filesystem
{
	uint32_t offset; // Offset to the .ADX file
	uint32_t size; // Size of the .ADX file
};

// Precondition: Parameter filename is a string representing a valid .AFS archive's filename
// Postcondition: .ADX files aer extracted from the .AFS archive
int unpackAFS(char *filename)
{
	int i, j; // Used in for loops
	char *dir; // Base filename for generating output filenames
	FILE *inputAFS, *outputADX; // Streams for input and output

	struct afsHeader fileHeader; // Header of the archive
	struct afsEntry *fileEntries; // Filesystem of the archive

	dir = malloc(strlen(filename)); // Initialize the base filename
	strcpy(dir, filename); // Copy the .AFS filename into it
	*(strrchr(dir, '.')) = '\0'; // Take off the extension

	inputAFS = fopen(filename, "rb"); // Open the .AFS archive for binary reading
	if(!inputAFS) // If it didn't open
		return(1); // Complain

	fread(&fileHeader, sizeof(fileHeader), 1, inputAFS); // Read in the header
	if(strcmp(fileHeader.magic, "AFS")) // Make sure it's got the magic word
	{
		fclose(inputAFS); // If it doesn't, we don't want it
		printf("\nError: Not a valid .AFS file\n"); // Tell the people
		return(2); // Complain
	}

	printf("\n%u Sounds:\n", fileHeader.count); // Display some header info

	fileEntries = malloc(sizeof(fileEntries[0]) * fileHeader.count); // Initialize the array of entries
	fread(fileEntries, sizeof(fileEntries[0]), fileHeader.count, inputAFS); // Read the table of contents

	for(i = 0; i < fileHeader.count; i++) // For each file entry
	{
		char *name; // Output file's name

		name = malloc(strlen(dir) + 10); // Make a string that's big enough for the filename
		fseek(inputAFS, fileEntries[i].offset, SEEK_SET); // Go to the file offset

		printf("\tEntry: 0x%04X\tOffset: 0x%08X\tSize: 0x%08X\n",
				i, fileEntries[i].offset, fileEntries[i].size); // Output some info about the file

		sprintf(name, "%s_%04d.adx", dir, i); // Make the filename string
		outputADX = fopen(name, "wb"); // Try to open the .ADX file for writing
		if(!outputADX) // If it didn't open properly
			return(3); // Complain

		for(j = 0; j < fileEntries[i].size; j++) // For each of the bytes
			fputc(fgetc(inputAFS), outputADX); // Copy the bytes from one stream to the other

		fclose(outputADX); // Close the file, as we're done with it
	}

	fclose(inputAFS); // Close the file, as we're done with it

	return 0; // We're all done
}

int main(int argc, char *argv[]) // Main part of the program
{
	printf("Lightning's .AFS Utility\n"); // =P
	if(argc <= 1) // If there aren't the right arguments
		printf("\n\tUsage: AFS_Unpk <filename>.afs\n"); // Tell the people
	else // If it's run correctly
		return unpackAFS(argv[1]); // Do it

	return(0); // Finished
}