// alder32.c, version 1.1.0
// OMKOV cryptutils alder32
// Copyright (C) 2020, Jakob Wakeling
// MIT Licence

#include "util/error.c"
#include "util/optget.h"

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>

#define VERSION "1.1.0"

static struct lop lops[] = {
	{ "help",    ARG_NUL, 256 },
	{ "version", ARG_NUL, 257 },
	{ "bsd",     ARG_NUL, 258 },
	{ NULL, 0, 0 }
};

static bool qflag;
static int form;

static inline void alder32(const char *file);

static void hlp(void);
static void ver(void);

int main(int ac, char *av[]) { A0 = av[0];
	struct opt opt = OPTGET_INIT; opt.str = "q"; opt.lops = lops;
	for (int o; (o = optget(&opt, av, 1)) != -1;) switch (o) {
	case 'q': { qflag = true; break; }
	case 256: { hlp(); return 0; }
	case 257: { ver(); return 0; }
	case 258: { form = 1; break; }
	default: { return 1; }
	}
	
	if (opt.ind == ac) { alder32(NULL); }
	else for (char **p = &av[opt.ind]; *p; ++p) { alder32(*p); }
	
	return warned;
}

static inline void alder32(const char *file) {
	uint8_t buf[BUFSIZ * 16]; FILE *fi; register uint32_t a = 1, b = 0;
	
	if (!file) { fi = stdin; } else { fi = fopen(file, "rb"); }
	if (!fi) { warn("%s: %s", file, serr()); return; }
	
	for (size_t c; (c = fread(buf, 1, sizeof (buf), fi));) {
		for (register size_t i = 0; i != c; ++i) {
			a = (a + buf[i]) % 65521; b = (b + a) % 65521;
		}
	} a = (b << 16) | a;
	
	if (ferror(fi)) { fclose(fi); warn("%s: %s", file, serr()); return; }
	
	if (!file || qflag) { printf("%08X\n", a); } else switch (form) {
	case 0: { printf("%08X *%s\n", a, file); break; }
	case 1: { printf("ALDER32 (%s) = %08X\n", file, a); break; }
	}
	
	if (fi != stdin) { fclose(fi); } return;
}

static void hlp(void) {
	puts("alder32 - compute the Alder-32 for a file\n");
	puts("usage: alder32 [file...]\n");
	puts("options:");
	puts("  --bsd      Use BSD style checksums");
	puts("  --help     Display help information");
	puts("  --version  Display version information");
}

static void ver(void) {
	puts("OMKOV cryptutils alder32, version " VERSION);
	puts("Copyright (C) 2020, Jakob Wakeling");
	puts("MIT Licence (https://opensource.org/licenses/MIT)");
}