qemuconf.c

/*
 * qemuconf.c
 * Copyright (C) 2015 tox <tox@rootkit>
 *
 * Distributed under terms of the MIT license.
 */

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <limits.h>
#include <string.h>
#include <libgen.h>
#include <ctype.h>

#define DROP(x, y) { for(y = i; i < len && x; i++); }
#define BEGINS(x, y) (strncmp(x, y, strlen(y)) == 0)

static int start();
static int dump();
static int addoptarg(char *arg, int len);
static int addopt(char *opt, int len);
static int compact(char *text, int i, int len, int minindent);
static int parseconfig(char *text, int len);
static int loadconfig(char *path);

char **cargv;
char **curopt = NULL;
char *cwd = ".";
static char *binary = NULL;
int cargc = 1;
int maxargc = 0;

int
start() {
	if(chdir(cwd)) {
		perror(cwd);
		return 1;
	}
	execvp(binary, cargv);
	perror(binary);
	return 1;
}

int dump() {
	int i;

	fputs(cargv[0], stdout);
	for(i = 1; i < cargc; i++) {
		fputc(' ', stdout);
		fputs(cargv[i], stdout);
	}
	fputc('\n', stdout);
}

int
addoptarg(char *arg, int len) {
	arg[len] = '\0';
	if(curopt != NULL) {
		*curopt = arg;
		curopt = NULL;
		return 0;
	}
	cargv[cargc] = arg;
	if(++cargc == maxargc) {
		fputs("Too many args", stderr);
		return 1;
	}
	cargv[cargc] = NULL;

	return 0;
}

int
addopt(char *opt, int len) {
	char *optdup;
	if(BEGINS(opt, "cwd")) {
		curopt = &cwd;
	} else if(BEGINS(opt, "binary")) {
		curopt = &binary;
	} else {
		if(!(optdup = calloc(sizeof(char), len + 2))) {
			perror("malloc");
			return 1;
		}
		optdup[0] = '-';
		memcpy(optdup+1, opt, len);
		return addoptarg(optdup, len + 1);
	}
	return 0;
}

int
compact(char *text, int i, int len, int minindent) {
	int _i, indent, curindent, w=i, line = 0;

	for(curindent = 0, indent = -1, line = 0; i < len; line++, i++) {
		DROP(isspace(text[i]) && text[i] != '\n', _i);
		curindent = i - _i;

		if(text[i] == '#' || text[i] == '\n') {
			DROP(text[i] != '\n', i);
			continue;
		}
		else if(line != 0 && curindent <= minindent) {
			break;
		}

		DROP(isalnum(text[i]), _i);
		memmove(&text[w], &text[_i], i - _i);
		w += i - _i;
		DROP(isspace(text[i]) && text[i] != '\n', _i);
		if(_i != i) {
			text[w++] = '=';
		}
		DROP(text[i] != '\n', _i);
		memmove(&text[w], &text[_i], i - _i);
		w += i - _i;
		text[w++] = ',';
		curindent = 0;
	}
	memset(&text[w], ' ', i - curindent - w);
	memset(&text[w-1], '\n', line - 1);
	text[i-curindent-1] = '\n';
	return 0;
}

int
parseconfig(char *text, int len) {
	int i = 0, _i, line, linestart, curindent;

	for(linestart = i = line = 0; i < len; line++, linestart = ++i) {
		DROP(isspace(text[i]) && text[i] != '\n', _i);
		curindent = i - _i;
		if(i >= len)
			break;

		if(text[i] == '\n')
			continue;
		if(text[i] == '#') {
			DROP(text[i] != '\n', i);
			continue;
		}

		if(text[i] == '.') {
			i++;
			DROP(isspace(text[i]), i);
			DROP(text[i] != '\n', _i);
			text[i] = '\0';
			if(loadconfig(&text[_i])) {
				fprintf(stderr, "Error at line %i. ", line + 1);
				return 1;
			}
			continue;
		}

		DROP(isalnum(text[i]) || text[i] == '-', _i);

		addopt(&text[_i], i - _i);

		DROP(isspace(text[i]) && text[i] != '\n', i);
		if(text[i] == '\n')
			continue;
		else if(text[i] == ':' || i != _i) {
			if(text[i] == ':') {
				_i = ++i;
			}
			else {
				DROP(isspace(text[i]) && text[i] != '\n', i);
				DROP(text[i] != '\n', _i);
			}

			if(text[i-1] == ':') {
				text[i-1] = ',';
				if(compact(text, i, len, curindent)) {
					fprintf(stderr, "at line %i character %i. ", line + 1, i - linestart);
					return 1;
				}
				DROP(text[i] != '\n', i);
			}

			addoptarg(&text[_i], i - _i);
		}
		else if(i == _i) {
			fprintf(stderr, "Expected whitespace or ':' instead of '%c' at line %i character %i. ", text[i], line + 1, i - linestart);
			return 1;
		}
	}
	return 0;
}

int
loadconfig(char *path) {
	int r = 0, len = 0;
	char *text = NULL, *wd;
	char oldwd[PATH_MAX+1] = { 0 };
	FILE *file;
	char *pathdup = strdup(path);

	if(!(file = fopen(path, "r"))) {
		perror(path);
		return 1;
	}

	if(!getcwd(oldwd, sizeof(oldwd))) {
		perror("getcwd");
		return EXIT_FAILURE;
	}

	wd = dirname(pathdup);
	if(chdir(wd)) {
		perror(wd);
		return 1;
	}

	do {
		len += r;
		text = realloc(text, sizeof(char) * (len + BUFSIZ));
	} while((r = fread(text, sizeof(char), (len + BUFSIZ - 1), file)) > 0);
	text[len] = 0;

	if(ferror(file)) {
		perror(path);
		return 1;
	}

	if(parseconfig(text, strlen(text))) {
		fprintf(stderr, "At file '%s'\n", path);
		return 1;
	}

	if(chdir(oldwd)) {
		perror(oldwd);
		return 1;
	}
	free(pathdup);

	return 0;
}

int main(int argc, char *argv[]) {
	int opt;
	int (*action)() = start;

	while ((opt = getopt(argc, argv, "nq:V")) != -1) {
		switch(opt) {
			case 'q':
				binary = optarg;
				break;
			case 'n':
				action = dump;
				break;
			case 'V':
				puts("qemuconf-" VERSION);
				return EXIT_SUCCESS;
usage:
			default:
				printf("Usage: %s [-n] [-q exec] [-V] CONFIGFILE [-- [qemu args...]]\n", argv[0]);
				return EXIT_FAILURE;
		}
	}
	if(optind >= argc)
		goto usage;

	if((maxargc = sysconf(_SC_ARG_MAX)) < 0) {
		perror("sysconf");
		return EXIT_FAILURE;
	}

	if(!(cargv = calloc(sizeof(char *), maxargc))) {
		perror("calloc");
		return EXIT_FAILURE;
	}

	if(loadconfig(argv[optind++]))
		return EXIT_FAILURE;

	for(; optind < argc; optind++, cargc++) {
		cargv[cargc] = argv[optind];
	}

	if(!binary)
		binary = BINARY;
	cargv[0] = binary;
	if(action())
		return EXIT_FAILURE;
	return EXIT_SUCCESS;
}